Pipe hot gas pressure forming method with pressure and pressure increasing rate double control

Abstract

The application provides a pipe hot gas pressure forming method with pressure and pressure increasing rate double control, and relates to the technical field of intelligent pressure forming equipment control. The method comprises the following steps: obtaining forming process parameters corresponding to a plurality of to-be-formed pipes, the parameters comprising target pressure and target pressure increasing rate required by the to-be-formed pipes; when the to-be-formed pipes are placed in a mold, the to-be-formed pipes in the mold are pressurized, and in the pressurizing process, the actual pressure and actual pressure increasing rate of the gas medium acting on the to-be-formed pipes are obtained in real time; based on the target pressure, target pressure increasing rate, actual pressure and actual pressure increasing rate, the pressure deviation and pressure increasing rate deviation of the gas medium are determined; and the gas medium is dynamically adjusted based on the pressure deviation and pressure increasing rate deviation until the to-be-formed pipes completely fit the mold. The application controls the pressure increasing rate in the pipe hot gas pressure forming process, effectively improves the forming quality problem caused by the unstable pressure rising gradient, and reduces the failure rate of the forming.

Description

Technical Field

[0001] This invention relates to the field of intelligent pressure forming equipment control technology, and more specifically, to a hot gas pressure forming method for pipe fittings with dual control of pressure and pressurization rate. Background Technology

[0002] Lightweight, high-strength metal pipes made of ultra-high-strength steel, aluminum alloys, titanium alloys, and magnesium alloys are widely used in aerospace, automotive, and rail transportation industries, and hot gas pressure forming is the core forming process for these pipes.

[0003] In existing hot pneumatic forming processes for pipe fittings, forming pressure is typically the sole control target. The final forming pressure is adjusted to achieve mold-fitting of the pipe fitting. However, in actual forming, due to the high compressibility of the gas medium, controlling only the final forming pressure makes the pressure output susceptible to factors such as gas path resistance and changes in gas compression. This results in an inability to form a stable pressure gradient, leading to either excessively low or excessively high actual pressure rise rates. This makes it difficult to match the process window requirements for hot forming of pipe fittings, resulting in a high failure rate. Summary of the Invention

[0004] The problem addressed by this invention is how to improve the unstable pressure gradient caused by the compressibility of gas and to improve the forming quality of hot gas pressure forming of pipe fittings.

[0005] To address the above problems, this invention provides a method for hot gas pressure forming of pipe fittings with dual control of pressure and pressurization rate, comprising: Obtain forming process parameters for multiple pipe fittings to be formed, including the target pressure and target pressure increase rate required for forming the pipe fittings to be formed; After multiple tubes to be formed are placed in their respective molds, the tubes to be formed in the molds are pressurized, and during the pressurization process, the actual pressure and actual pressurization rate of the gas medium acting on the tubes to be formed are obtained in real time. Based on the target pressure, the target pressure increase rate, the actual pressure, and the actual pressure increase rate, the pressure deviation and pressure increase rate deviation of the gas medium are determined. Based on the pressure deviation and the pressure rise rate deviation, the gas medium is dynamically adjusted in a coordinated manner until the tube to be formed is completely fitted to the mold.

[0006] Optionally, obtaining the forming process parameters corresponding to the multiple pipe fittings to be formed includes: The target pressure is determined by combining the material properties, cross-sectional geometry, and forming type of each of the tubes to be formed; The forming time is determined based on the process constraints corresponding to the forming type. The target pressure increase rate is determined by combining the forming time and the target pressure.

[0007] Optionally, the step of pressurizing the tubes to be formed in the molds after the plurality of tubes to be formed are placed in the corresponding molds includes: Each of the tubes to be formed is heated to a preset forming temperature, and the tubes to be formed at the preset forming temperature are placed into the cavity of the mold for mold closing operation; After the mold is closed, the mold is sealed, and then the gas medium is introduced into the cavity of the sealed mold. Each of the tubes to be formed is pressurized according to the target pressurization rate and the target pressure.

[0008] Optionally, the real-time acquisition of the actual pressure and actual pressure rise rate of the gas medium acting on the tube to be formed includes: The actual pressure of the gas medium inside the mold cavity is collected at a preset sampling frequency by a pressure detection element installed in the gas path communicating with the cavity of the mold. The actual pressure rise rate of the gas medium is determined based on the actual pressure at all sampling times within the preset current time period and the sampling time difference between each sampling time.

[0009] Optionally, determining the pressure deviation and pressure rise rate deviation of the gas medium based on the target pressure, the target pressure rise rate, the actual pressure, and the actual pressure rise rate includes: The pressure deviation of the gas medium at the current sampling time is obtained by calculating the difference between the actual pressure at the current sampling time and the target pressure. The difference between the target pressure increase rate and the actual pressure increase rate within the preset current time period is calculated to obtain the pressure increase rate deviation of the gas medium within the preset current time period.

[0010] Optionally, the step of dynamically adjusting the gas medium based on the pressure deviation and the pressure rise rate deviation until the tube to be formed completely fits the mold includes: Based on the forming conditions of the tube to be formed, and in combination with the pressure deviation and the pressure rise rate deviation, an adjustment strategy for the gas medium is determined. According to the adjustment strategy, the gas medium is dynamically adjusted in a coordinated manner until the tube to be formed is completely fitted to the mold.

[0011] Optionally, the forming conditions include non-isothermal forming, and the step of determining the adjustment strategy for the gas medium based on the forming conditions of the pipe to be formed, combined with the pressure deviation and the pressure rise rate deviation, includes: When the forming condition is non-isothermal forming, it is determined whether the pressurization process is delayed based on the pressure deviation and the pressurization rate deviation. If so, the pressure compensation value of the target pressure is obtained, and the opening adjustment value of the control valve of the gas path corresponding to the gas medium is determined according to the preset rules; an adjustment strategy for the gas medium is formed according to the pressure compensation value and the opening adjustment value. If not, continue pressurizing according to the target pressurization rate and the target pressure.

[0012] Optionally, determining whether the pressurization process is delayed based on the pressure deviation and the pressurization rate deviation includes: Determine whether the pressure rise rate deviation and the pressure deviation are less than zero; If the pressure increase rate deviation is less than zero, and / or the pressure deviation is less than zero, then the pressure increase process is determined to be delayed. If both the pressure increase rate deviation and the pressure deviation are not less than zero, then the pressurization process is determined to be not delayed.

[0013] Optionally, the forming conditions include isothermal forming, and the step of determining the adjustment strategy for the gas medium based on the forming conditions of the pipe to be formed, combined with the pressure deviation and the pressure rise rate deviation, includes: When the forming condition is isothermal forming, the opening value of the control valve corresponding to the gas medium in the gas path is adjusted upward according to the preset rule. Based on the opening adjustment value, an adjustment strategy for the gas medium is formed.

[0014] Optionally, determining whether the pressurization process is delayed based on the pressure deviation and the pressurization rate deviation includes: When the pressure deviation is less than zero or the pressure increase rate deviation is less than zero, it is determined that there is a lag in the pressure increase process; When both the pressure deviation and the pressurization rate deviation are greater than or equal to zero, it is determined that there is no lag in the pressurization process.

[0015] The hot gas pressure forming method for pipe fittings with dual control of pressure and pressurization rate of the present invention introduces a target pressurization rate as the core control parameter and monitors the actual pressurization rate in real time during the pressurization process. This enables the system to accurately quantify the dynamic behavior of the gas medium during the compression process, transforming the pressure rise gradient, which was originally unstable due to factors such as gas compressibility, gas path resistance, and changes in gas compression, into a traceable and controllable variable. This improves the problem of unstable pressure rise gradient and solves the difficulty in matching the process window due to excessive fluctuations in pressurization rate, achieving precise adjustment of the entire gas pressure forming process.

[0016] Furthermore, by calculating pressure deviation and pressurization rate deviation in real time, a dual-variable collaborative control logic was established. This mechanism not only utilizes pressure deviation to ensure the accuracy of the forming endpoint, but also compensates for process disturbances caused by gas compressibility in real time through pressurization rate deviation. When the actual pressurization rate deviates from the target value, the system can dynamically adjust the gas flow rate to keep the pressure rise gradient under control, ensuring that the actual process curve always fits the optimal process window for hot forming of the material. This significantly enhances the ability to suppress external disturbances such as gas source fluctuations and material performance differences, and significantly improves the robustness of the forming process. Moreover, this invention can independently perform collaborative dynamic adjustment of pressure and pressurization rate for multiple pipe fittings, avoiding mutual interference and allowing each pipe fitting to be formed simultaneously according to its own optimal process window, greatly improving production efficiency and consistency.

[0017] Finally, through coordinated dynamic adjustment of pressure and rate, the pipe fitting completes deformation and ultimately achieves precise mold placement under the optimal strain rate path. This control strategy effectively avoids defects such as excessive local thinning or cracking of the pipe fitting due to excessively rapid pressure rise, and heat loss and insufficient forming due to excessively slow rates. By stabilizing the pressure rise gradient and precisely matching the process window, the resulting pipe fitting exhibits a more uniform wall thickness distribution and higher geometric accuracy. This effectively improves the forming quality problems caused by unstable pressure rise gradients while also reducing the forming failure rate. Attached Figure Description

[0018] Figure 1 This is a schematic flowchart of the hot gas pressure forming method for pipe fittings with dual control of pressure and pressurization rate according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the ideal control curve under non-isothermal forming conditions according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the actual control curve under non-isothermal forming conditions according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the control curve under isothermal forming conditions in an embodiment of the present invention. Detailed Implementation

[0019] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Although some embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the accompanying drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0020] It should be understood that the various steps described in the method embodiments of the present invention may be performed in different orders and / or in parallel. Furthermore, the method embodiments may include additional steps and / or omit the steps shown. The scope of the present invention is not limited in this respect.

[0021] The term "comprising" and its variations as used herein are open-ended, meaning "including but not limited to"; the term "based on" means "at least partially based on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments"; and the term "optionally" means "optional embodiments". Definitions of other terms will be given in the following description. It should be noted that the concepts of "first," "second," etc., mentioned in this invention are used only to distinguish different devices, modules, or units, and are not intended to limit the order of functions performed by these devices, modules, or units or their interdependencies.

[0022] It should be noted that the terms "a" and "a plurality of" used in this invention are illustrative rather than restrictive. Those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

[0023] It should be noted that the information (including but not limited to user device information, user personal information, etc.), data (including but not limited to data used for analysis, data stored, data displayed, etc.) and signals involved in this application are all authorized by the user or fully authorized by all parties. The collection, use and processing of related data must comply with the relevant laws, regulations and standards of the relevant countries and regions, and corresponding operation portals are provided for users to choose to authorize or refuse.

[0024] Combination Figure 1 As shown, the hot gas pressure forming method for pipe fittings with dual control of pressure and pressurization rate provided in this embodiment of the invention includes: Obtain forming process parameters corresponding to multiple pipe fittings to be formed, including the target pressure and target pressure increase rate required for forming the pipe fittings.

[0025] Specifically, when obtaining the forming process parameters for multiple pipe fittings to be formed, it is necessary to determine the matching target pressure value based on the material properties and cross-sectional geometric features of the pipe fittings to be formed. ) and target boost rate ( The target pressurization rate satisfies the total forming time from the start of pressurization to the complete molding of the pipe fitting. The time required for the critical region of the tube blank to cool from the initial pressurization temperature to the lower limit of the forming temperature is less than or equal to the time required for the tube blank to cool. For non-isothermal forming scenarios, the target pressure is calculated by combining the heat conduction law of the tube blank and the material flow stress model. For isothermal forming scenarios, the target pressure increase rate is determined based on the deformation of the tube and the optimized strain rate in the process window. At the same time, the target pressure needs to be set by combining the geometric features of the part, such as the minimum fillet radius, and the material flow stress model, so as to obtain and determine the forming process parameters required for forming the tube to be formed.

[0026] After multiple tubes to be formed are placed in their respective molds, the tubes to be formed in the molds are pressurized, and during the pressurization process, the actual pressure and actual pressurization rate of the gas medium acting on the tubes to be formed are obtained in real time.

[0027] Specifically, the tube blank to be formed is heated to a predetermined forming temperature. During non-isothermal forming, the mold is kept at room temperature or below the preset temperature of the tube blank. During isothermal forming, the mold is simultaneously heated to the same predetermined forming temperature as the tube blank. The heated tube blank is then placed into the mold cavity, and the mold is closed and sealed. Subsequently, a gaseous medium is injected into the tube blank within the sealed mold cavity through a pressure source, officially starting the pressurization process. During pressurization, a pressure sensor installed in the gas path connected to the mold cavity is used to detect the pressure signal of the gaseous medium in real time at a preset sampling frequency, obtaining the current measured pressure value. ), and calculate the current measured pressure rise rate based on the real-time collected continuous pressure data (). This enables real-time and accurate acquisition of actual pressure and actual pressurization rate during the forming process.

[0028] Based on the target pressure, the target pressurization rate, the actual pressure, and the actual pressurization rate, the pressure deviation and pressurization rate deviation of the gas medium are determined.

[0029] Specifically, based on a pre-set target pressure value ( ), target boost rate ( Based on the benchmark, combined with the measured pressure values ​​obtained in real time during the pressurization process ( ), measured boost rate ( By calculating the numerical difference, the pressure deviation (ΔP) and pressure rise rate deviation (ΔV) of the gas medium are obtained respectively. This allows for precise quantification of the deviation between the actual forming parameters and the target process parameters, providing direct and reliable data for subsequent coordinated dynamic adjustments.

[0030] Based on the pressure deviation and the pressure rise rate deviation, the gas medium is dynamically adjusted in a coordinated manner until the tube to be formed is completely fitted to the mold.

[0031] Specifically, based on the calculated pressure deviation (ΔP) and pressure rise rate deviation (ΔV), a coordinated control command is sent to the pressurization control unit to achieve coordinated dynamic adjustment of the pressure rise rate of the gas medium and the pressure control target of the forming process; if the measured pressure rise rate (ΔV) is detected... () lower than the target boost rate () When there is a tendency for pressure boosting to lag, on the one hand, the opening of the output control valve of the boosting system is increased to directly improve the measured pressure boosting rate. On the other hand, based on the estimated temperature drop of the billet caused by the pressure lag, a higher second target pressure is calculated through the system's preset forming pressure-temperature relationship model. The original pressure control target is then adjusted to this second target pressure as the new pressure control target. For isothermal forming scenarios, the pressure boosting system adjusts the control valve opening in real time based solely on the deviation between the measured pressure boosting rate and the target pressure boosting rate, dynamically controlling the pressure boosting rate to make the measured pressure boosting rate as close as possible to the target pressure boosting rate. Throughout the adjustment process, the steps of real-time acquisition of measured pressure and measured pressure boosting rate, calculation of deviation, and coordinated dynamic control are continuously executed until the pipe to be formed is completely fitted to the mold cavity. For example, during the coordinated dynamic adjustment process, when the real-time monitored pressure deviation and pressure boosting rate deviation are both close to zero, for example, less than the preset minimum threshold, and the measured pressure value reaches the target pressure, it can be determined that the pipe to be formed is completely fitted to the mold. After the mold is fitted, a pressure holding and shaping operation can be performed to further ensure the forming quality of the pipe.

[0032] In a preferred embodiment of the present invention, the preset forming pressure-temperature relationship model is a correlation model that is pre-set based on the material properties and forming process requirements of the tube to be formed. It is used to calculate the target forming pressure to be compensated based on the estimated temperature drop of the tube blank in the case of pressure lag. The core correspondence is that the tube blank temperature drops due to pressure lag, and the flow stress of the tube blank increases as the temperature drops. Based on this physical law, the model establishes a quantitative correlation between the estimated temperature drop of the tube blank and the adjustment value of the forming pressure, which directly provides a basis for the calculation of the second target pressure. For example, in the non-isothermal forming process of ultra-high strength steel 22MnB5 pipe fittings, the initial target pressure was set to 28MPa. At the 6-second forming time point, the system detected a significant pressure lag, with a measured pressure of 18.5MPa, a measured pressure increase rate of 3.1MPa / s, a pressure deviation of -2.5MPa, and a pressure increase rate deviation of -0.4MPa / s. At this point, the system, using the preset forming pressure-temperature relationship model and considering the estimated temperature drop of the billet caused by the pressure lag, directly calculated that the second target pressure needed to be adjusted to 30MPa. Based on this, the original target pressure of 28MPa was adjusted to 30MPa, completing the pressure compensation. In another example, three 22MnB5 pipe fittings were simultaneously subjected to hot gas pressure forming, each placed in an independent mold cavity and equipped with an independent air path and pressure sensor. Target pressure and pressurization rate are set according to the geometric characteristics of each pipe fitting. The three pressurization channels are independently pressurized, and their deviations are monitored in real time and dynamically adjusted independently without interference. In the end, all three pipe fittings are accurately molded, with uniform wall thickness and no forming defects.

[0033] This embodiment of the hot gas pressure forming method for pipe fittings, which controls both pressure and pressurization rate, introduces a target pressurization rate as the core control parameter and monitors the actual pressurization rate in real time during the pressurization process. This allows the system to accurately quantify the dynamic behavior of the gas medium during compression, transforming the previously unstable pressure rise gradient, which was affected by factors such as gas compressibility, gas path resistance, and changes in gas compression, into a trackable and controllable variable. This improves the problem of unstable pressure rise gradient and solves the difficulty in matching the process window due to excessive fluctuations in pressurization rate, achieving precise adjustment of the entire gas pressure forming process.

[0034] Furthermore, by calculating pressure deviation and pressurization rate deviation in real time, a dual-variable collaborative control logic was established. This mechanism not only utilizes pressure deviation to ensure the accuracy of the forming endpoint, but also compensates for process disturbances caused by gas compressibility in real time through pressurization rate deviation. When the actual pressurization rate deviates from the target value, the system can dynamically adjust the inflation flow rate to keep the pressure rise gradient under control, ensuring that the actual process curve always fits the optimal process window for hot forming of the material. This significantly enhances the ability to suppress external disturbances such as gas source fluctuations and material performance differences, and significantly improves the robustness of the forming process. Moreover, this embodiment can independently perform collaborative dynamic adjustment of pressure and pressurization rate for multiple pipe fittings, avoiding mutual interference and allowing each pipe fitting to be formed simultaneously according to its own optimal process window, greatly improving production efficiency and consistency.

[0035] Finally, through coordinated dynamic adjustment of pressure and rate, the pipe fitting completes deformation and ultimately achieves precise mold placement under the optimal strain rate path. This control strategy effectively avoids defects such as excessive local thinning or cracking of the pipe fitting due to excessively rapid pressure rise, and heat loss and insufficient forming due to excessively slow rates. By stabilizing the pressure rise gradient and precisely matching the process window, the resulting pipe fitting exhibits a more uniform wall thickness distribution and higher geometric accuracy. This effectively improves the forming quality problems caused by unstable pressure rise gradients while also reducing the forming failure rate.

[0036] Optionally, obtaining the forming process parameters corresponding to the multiple pipe fittings to be formed includes: The target pressure is determined by combining the material properties, cross-sectional geometry, and forming type of each of the tubes to be formed; The forming time is determined based on the process constraints corresponding to the forming type. The target pressure increase rate is determined by combining the forming time and the target pressure.

[0037] Specifically, the forming type of each pipe to be formed is determined as isothermal forming or non-isothermal forming. Then, based on the material properties of the pipe, the corresponding hot flow stress model of the material is retrieved. At the same time, combined with the geometric features of the part cross section, key forming geometric parameters such as the minimum inner corner radius of the part are considered. Based on the above material properties and geometric features, the matching target pressure values ​​are set respectively.

[0038] In a preferred embodiment of the present invention, the temperature matching relationship between the blank and the mold during the forming process is determined based on the material hot forming characteristics of each tube to be formed, the forming accuracy requirements of the part, and the actual production process conditions, thereby classifying the forming type: if the blank and the mold are heated synchronously to the same preset forming temperature during forming, so that the blank is always in the constant temperature environment to complete plastic deformation during the forming process, it is isothermal forming. For example, when forming aluminum alloy 6061 tubes, both the blank and the mold are heated to a predetermined forming temperature of 420°C. The blank and the mold maintain the same temperature during the forming process, and this forming type is isothermal forming. If the blank is only heated to a predetermined forming temperature during forming, and the mold is kept at room temperature or a preset temperature lower than the predetermined forming temperature of the blank, the blank will continuously cool during the forming process due to heat conduction with the mold, which is non-isothermal forming. For example, when forming ultra-high strength steel 22MnB5 tubes, only the blank is heated to a predetermined forming temperature of 910°C, and the mold is kept at room temperature. The blank will transfer heat to the mold and continuously cool during the forming process, and this forming type is non-isothermal forming.

[0039] For example, when forming ultra-high strength steel 22MnB5 pipes non-isothermal, the target pressure is set to 28MPa, based on its material flow stress model and the cross-sectional geometry of the part with a minimum inner corner radius of 12mm. When forming aluminum alloy 6061 pipes isothermal, the target pressure is set to 25MPa, based on its material flow stress model and the cross-sectional geometry of the part with a minimum inner corner radius of 6mm. If the forming type is non-isothermal, the process constraint is the time required for the critical area of ​​the billet to cool from the initial pressurization temperature to the lower limit of the forming temperature. The forming time must be less than or equal to this cooling time. For example, when forming ultra-high strength steel 22MnB5 pipes non-isothermal, the time for the critical corner area of ​​the billet to cool to the lower limit of the forming temperature is 8.5s, so the forming time is set to 8s. If the forming type is isothermal, the process constraint is the optimized strain rate in the pipe process window. The appropriate forming time is determined by combining the deformation of the pipe fitting with the optimized strain rate. For example, when isothermally forming aluminum alloy 6061 pipe fittings, the forming time is set to 21s based on the deformation of the part and the optimized strain rate within the process window. When determining the target pressure rise rate by combining the forming time and the target pressure, the target pressure is used as the numerator and the determined forming time is used as the denominator. The target pressure rise rate required for forming the pipe fitting is obtained by calculating the ratio of pressure to time. For example, for ultra-high strength steel 22MnB5 pipe fittings, the target pressure rise rate is calculated to be 3.5MPa / s based on a target pressure of 28MPa and a forming time of 8s. For aluminum alloy 6061 pipe fittings, the target pressure rise rate is calculated to be 1.2MPa / s based on a target pressure of 25MPa and a forming time of 21s. This completes the determination of the target pressure rise rate corresponding to the pipe fitting to be formed.

[0040] Combination Figure 4As shown, Figure 4 This is the control curve under isothermal forming conditions. The horizontal axis represents forming time t, the left vertical axis represents gas pressure P, and the right vertical axis represents temperature T. The orange curve in the figure represents the target temperature of the tube blank. The curve shows a slow decrease over time (temperature fluctuations are minimal under isothermal forming); the blue dashed line represents the target pressure ramp rate set based on the target forming time and average strain rate. The corresponding pressure rise curve; the red solid line represents the actual pressure rise rate. The corresponding pressure rise curve, through segmented fine-tuning of the pressure rise rate, ensures that the actual pressure is within... Reaching the target precisely at the right time At the same time, it ensures that the average strain rate of the entire forming process meets the process window requirements.

[0041] In this optional embodiment, by determining the target pressure, forming time, and target pressure ramp rate in layers and dimensions according to forming type, precise and adaptable setting of forming process parameters is achieved. This breaks through the limitations of traditional single pressure parameter setting. Target pressure determined by combining material properties and part cross-sectional geometry, considering the process characteristics and constraint differences of isothermal and non-isothermal forming types, can accurately match the force and energy requirements of the pipe fitting's plastic deformation. The forming time, determined according to the process constraints corresponding to the forming type, can respectively meet the limitations of billet cooling time under non-isothermal forming and the adaptation requirements of optimized strain rate within the process window under isothermal forming. By combining the target pressurization rate calculated based on the forming time and target pressure, a coordinated process parameter system is formed, which ensures the correlation and adaptability between various process parameters from the source of parameter setting. This avoids the problem of mismatch between pressurization rate and forming requirements caused by parameter setting disconnect. It lays a scientific and reasonable parameter foundation for the dual control and coordinated adjustment of pressure and pressurization rate in the subsequent forming process, effectively ensuring that the subsequent forming process proceeds according to the preset process rhythm. This reduces forming defects such as wrinkling, cracking, and insufficient mold application caused by unreasonable parameter setting, and improves the overall forming quality and forming efficiency of the pipe fitting.

[0042] Optionally, the step of pressurizing the tubes to be formed in the molds after the plurality of tubes to be formed are placed in the corresponding molds includes: Each of the tubes to be formed is heated to a preset forming temperature, and the tubes to be formed at the preset forming temperature are placed into the cavity of the mold for mold closing operation; After the mold is closed, the mold is sealed, and then the gas medium is introduced into the cavity of the sealed mold. Each of the tubes to be formed is pressurized according to the target pressurization rate and the target pressure.

[0043] Specifically, the preset forming temperature is determined according to the material properties and forming type of each pipe fitting to be formed. For non-isothermal forming of ultra-high strength steel 22MnB5 pipe fittings, the pipe blank is heated to the preset forming temperature of 910℃ and held for 7 minutes. For isothermal forming of aluminum alloy 6061 pipe fittings, the pipe blank and the mold are simultaneously heated to the same preset forming temperature of 420℃. Then, the pipe fitting to be formed, having reached the preset forming temperature, is quickly transferred into the mold cavity. The transfer time is controlled to avoid excessive drop in the temperature of the pipe blank. Subsequently, the mold is closed. The mold operation confines the tube blank within the preset forming space of the mold cavity. After the mold is closed, it is sealed to ensure the airtightness of the mold cavity and prevent leakage from affecting pressure control when gas medium is introduced later. After sealing, gas medium is introduced into the sealed mold cavity through a pressure source connected to the mold cavity. The gas medium is introduced into the mold cavity at a preset target pressurization rate and with the target pressure as the upper limit of the pressurization. The pressurization process of the tube blank is started, so that the gas medium acts on the surface of the tube blank to promote plastic deformation and gradually adhere to the mold cavity wall.

[0044] In this optional embodiment, standardized and streamlined operations for heating the pipe fitting, placing and closing the mold, sealing the mold, and pressurizing according to target parameters achieve standardized control of the pre-pressurization process in hot gas forming. First, the preset forming temperature is precisely controlled based on the pipe fitting material characteristics and forming type. Combined with billet insulation and rapid transfer operations, this effectively ensures that the billet temperature is within the process requirements when entering the mold, avoiding premature over-cooling of the billet in non-isothermal forming and uneven temperature in isothermal forming. Then, the mold closing operation confines the billet within the preset space of the mold cavity, laying the foundation for subsequent mold forming. The sealing treatment after mold closing ensures the airtightness of the mold cavity, preventing issues from a hardware perspective. The problem of pressure runaway and pressure rise rate fluctuations caused by gas medium leakage was addressed by introducing gas medium and starting pressurization according to the pre-set target pressure rise rate and target pressure. This ensured that the pressurization process followed the preset process rhythm from the initial stage, effectively avoiding the problem of parameter disorder in the initial stage of pressurization. This provided a stable process execution basis for real-time monitoring, deviation calculation and coordinated dynamic adjustment of pressure and pressure rise rate in the subsequent forming process. It reduced problems such as inaccurate forming pressure and abnormal pressure rise rate caused by non-standard operation of the preceding process, ensuring the effectiveness of subsequent dual-parameter coordinated control, thereby reducing the probability of pipe forming defects and improving the stability and controllability of the forming process.

[0045] Optionally, the real-time acquisition of the actual pressure and actual pressure rise rate of the gas medium acting on the tube to be formed includes: The actual pressure of the gas medium inside the mold cavity is collected at a preset sampling frequency by a pressure detection element installed in the gas path communicating with the cavity of the mold. The actual pressure rise rate of the gas medium is determined based on the actual pressure at all sampling times within the preset current time period and the sampling time difference between each sampling time.

[0046] Specifically, a pressure sensor is installed as a pressure detection element in the gas path connecting the mold cavity. A sampling frequency of 100Hz is set to meet the real-time monitoring requirements of hot gas pressure forming of the pipe. During the entire process of pressurizing the gas medium into the mold cavity, the pressure sensor continuously collects the pressure data of the gas medium inside the cavity according to the set sampling frequency. Each set of pressure data collected is the actual pressure of the gas medium acting on the surface of the pipe to be formed at the corresponding collection time, realizing continuous, accurate and real-time acquisition of the actual pressure during the forming process. Based on the continuous actual pressure data collected by the pressure sensor, the actual pressure value corresponding to each collection time within the preset current time period is extracted. Combined with the fixed collection time difference between adjacent collection times, the pressure change rate of the gas medium within the corresponding time period is obtained by calculating the pressure change per unit time. This rate is the actual pressurization rate of the gas medium acting on the pipe to be formed, thereby realizing the real-time measurement of the actual pressurization rate during the forming process and providing continuous and reliable measured data for subsequent deviation calculation.

[0047] In this optional embodiment, by installing pressure detection elements in the gas path connecting the mold cavity and continuously collecting actual pressure at a fixed high sampling frequency, and then accurately calculating the actual pressure rise rate based on continuous pressure data and the time difference of collection, real-time, continuous, and high-precision monitoring of pressure and pressure rise rate during the forming process is achieved. The high sampling frequency ensures the timeliness and completeness of pressure data collection, accurately capturing subtle pressure changes in the gas medium during the forming process, avoiding parameter monitoring distortion caused by data lag or missing data. The actual pressure rise rate is determined by the quantitative calculation of pressure change and time difference, making the dynamic process of pressure rise rate... The process parameters achieve precise numerical characterization, breaking through the limitations of traditional methods that can only monitor static pressure. This not only provides continuous and reliable measured data support for the accurate calculation of subsequent pressure deviation and pressurization rate deviation, but also ensures that the dynamic pressurization process during forming is monitored and quantifiable throughout. From the data acquisition level, it guarantees the accuracy and timeliness of the subsequent coordinated dynamic adjustment of the two parameters of pressure and pressurization rate, effectively avoiding the problem of improper control caused by inaccurate measured parameters and monitoring lag. This further improves the controllability and stability of the dual control system in the forming process, providing key data monitoring guarantees for high-quality forming of pipe fittings.

[0048] Optionally, determining the pressure deviation and pressure rise rate deviation of the gas medium based on the target pressure, the target pressure rise rate, the actual pressure, and the actual pressure rise rate includes: The pressure deviation of the gas medium at the current sampling time is obtained by calculating the difference between the actual pressure at the current sampling time and the target pressure. The difference between the target pressure increase rate and the actual pressure increase rate within the preset current time period is calculated to obtain the pressure increase rate deviation of the gas medium within the preset current time period.

[0049] Specifically, during the real-time monitoring of the forming pressurization process, for each pressure acquisition time point, the actual pressure value of the gas medium collected by the pressure detection element at that moment is directly extracted. This value is then compared with the pre-set forming target pressure value using a numerical difference calculation. The result of this calculation directly yields the pressure deviation of the gas medium at the current acquisition time, clearly quantifying the degree of deviation between the current actual pressure and the target pressure. For example, when the ultra-high strength steel 22MnB5 pipe fitting is formed to 2 seconds, the difference between the measured pressure of 5.2 MPa and the target pressure of 7 MPa at that moment yields a corresponding pressure deviation of -1.8 MPa. Simultaneously, for the preset current pressure acquisition time period, the actual pressure value collected during that time period is extracted... The actual pressure rise rate of the gas medium calculated from the pressure data is compared with the pre-set target pressure rise rate for forming. The result of this calculation yields the deviation of the gas medium's pressure rise rate within the current preset time period. This precisely quantifies the deviation of the actual pressure rise rate from the target pressure rise rate within that time period. For example, when the above-mentioned pipe fitting has been formed for 2 seconds, the difference between the measured pressure rise rate of 2.6 MPa / s and the target pressure rise rate of 3.5 MPa / s is calculated, resulting in a corresponding pressure rise rate deviation of -0.9 MPa / s. This enables real-time and precise quantification of the deviation of pressure and pressure rise rate from the target parameters during the forming process, providing a clear numerical basis for subsequent coordinated dynamic adjustments.

[0050] In this optional embodiment, by performing difference calculations on the actual pressure and target pressure at the current acquisition moment, and the actual pressure rise rate and target pressure rise rate over a preset time period, real-time and accurate quantification of pressure deviation and pressure rise rate deviation is achieved. This directly and clearly reflects the direction and degree of deviation of the actual forming parameters relative to the target process parameters in numerical form. It can accurately capture the instantaneous pressure deviation at each acquisition moment and effectively reflect the overall deviation of the pressure rise rate within the preset time period. This provides a clear, intuitive, and quantifiable numerical basis for subsequent coordinated dynamic adjustments, avoiding errors in control direction or inappropriate control intensity caused by ambiguous deviation judgment. It allows subsequent coordinated dynamic adjustments of the gas medium to have precise execution direction. From the perspective of deviation judgment, it ensures the pertinence and effectiveness of the coordinated control of pressure and pressure rise rate dual parameters, ensuring that the actual parameters can continuously approach the target parameters during the forming process. This further improves the controllability of the forming process and effectively reduces forming defects caused by inaccurate identification of parameter deviations. It provides key deviation judgment guarantee for the quality of pipe fitting molding.

[0051] Optionally, the step of dynamically adjusting the gas medium based on the pressure deviation and the pressure rise rate deviation until the tube to be formed completely fits the mold includes: Based on the forming conditions of the tube to be formed, and in combination with the pressure deviation and the pressure rise rate deviation, an adjustment strategy for the gas medium is determined. According to the adjustment strategy, the gas medium is dynamically adjusted in a coordinated manner until the tube to be formed is completely fitted to the mold.

[0052] Optionally, the forming conditions include non-isothermal forming, and the step of determining the adjustment strategy for the gas medium based on the forming conditions of the pipe to be formed, combined with the pressure deviation and the pressure rise rate deviation, includes: When the forming condition is non-isothermal forming, it is determined whether the pressurization process is delayed based on the pressure deviation and the pressurization rate deviation. If so, the pressure compensation value of the target pressure is obtained, and the opening adjustment value of the control valve of the gas path corresponding to the gas medium is determined according to the preset rules; an adjustment strategy for the gas medium is formed according to the pressure compensation value and the opening adjustment value. If not, continue pressurizing according to the target pressurization rate and the target pressure.

[0053] Optionally, determining whether the pressurization process is delayed based on the pressure deviation and the pressurization rate deviation includes: Determine whether the pressure rise rate deviation and the pressure deviation are less than zero; If the pressure increase rate deviation is less than zero, and / or the pressure deviation is less than zero, then the pressure increase process is determined to be delayed. If both the pressure increase rate deviation and the pressure deviation are not less than zero, then the pressurization process is determined to be not delayed.

[0054] Optionally, the forming conditions include isothermal forming, and the step of determining the adjustment strategy for the gas medium based on the forming conditions of the pipe to be formed, combined with the pressure deviation and the pressure rise rate deviation, includes: When the forming condition is isothermal forming, the opening value of the control valve corresponding to the gas medium in the gas path is adjusted upward according to the preset rule. Based on the opening adjustment value, an adjustment strategy for the gas medium is formed.

[0055] Optionally, determining whether the pressurization process is delayed based on the pressure deviation and the pressurization rate deviation includes: When the pressure deviation is less than zero or the pressure increase rate deviation is less than zero, it is determined that there is a lag in the pressure increase process; When both the pressure deviation and the pressurization rate deviation are greater than or equal to zero, it is determined that there is no lag in the pressurization process.

[0056] Specifically, after acquiring the pressure deviation and pressurization rate deviation in real time, the appropriate gas medium adjustment strategy is first determined based on the isothermal or non-isothermal forming conditions of the pipe to be formed, combined with the two types of deviation values. Then, the corresponding strategy is executed for coordinated dynamic adjustment until the pipe is completely fitted to the mold. When the forming condition is non-isothermal, it is first determined whether the pressurization rate deviation and pressure deviation are less than zero. If the pressurization rate deviation is less than zero and / or the pressure deviation is less than zero, the pressurization process is determined to be lagging. At this time, based on the estimated temperature drop of the billet caused by the pressurization lag, the pressure compensation value of the target pressure is calculated through the system's preset forming pressure-temperature relationship model. Simultaneously, according to the magnitude of the deviation value, the opening adjustment value of the corresponding gas path control valve is determined according to a preset ratio. This pressure compensation value and the opening adjustment value are combined to form an adjustment strategy for non-isothermal forming. For example, when the ultra-high strength steel 22MnB5 pipe is formed to 6 seconds, after determining the pressurization lag, the system... The model calculates a pressure compensation value of 2MPa, and simultaneously increases the opening of the gas path control valve by 30%. This forms an adjustment strategy and is executed. If both the pressure increase rate deviation and the pressure deviation are not less than zero, it is determined that the pressurization process is not lagging, and normal pressurization continues according to the preset target pressure increase rate and target pressure. When the forming condition is isothermal forming, there is no need to judge the pressurization lag state. The opening value of the gas path control valve corresponding to the gas medium is directly determined according to the magnitude of the pressure deviation and the pressure increase rate deviation, according to the preset ratio. Only this opening value is used to form an adjustment strategy for isothermal forming. For example, when the aluminum alloy 6061 pipe is formed to 5s, the opening of the gas path control valve is increased by 20% according to the deviation value. This forms an adjustment strategy and is executed. Subsequently, the actual pressure and the actual pressure increase rate are continuously monitored, and the above process of determining the adjustment strategy and executing the coordinated dynamic adjustment is repeated until the pipe to be formed completely fits the mold cavity, completing the hot gas pressure forming process.

[0057] Specifically, after obtaining the real-time pressure deviation and pressurization rate deviation, the isothermal or non-isothermal forming conditions of the pipe to be formed are first determined. Then, the gas medium is dynamically adjusted in a targeted manner based on the two types of deviation data. When the forming condition is non-isothermal, the magnitude of the negative values ​​of the pressure deviation and pressurization rate deviation is used to comprehensively judge whether there is a lag in the pressurization process. If a pressurization lag is determined, the opening of the output control valve in the gas medium circuit is increased proportionally according to the deviation value to increase the actual pressurization rate. At the same time, based on the estimated temperature drop of the billet caused by the pressurization lag, the pressure compensation value corresponding to the original target pressure is calculated through the system's preset forming pressure-temperature relationship model. This compensation value is superimposed on the initial target pressure to obtain a new target pressure, thereby completing the adjustment of the target pressure. Subsequently, the deviation is continuously monitored and the above adjustment actions are repeated until the pipe... When the component is completely fitted to the mold, such as when the ultra-high strength steel 22MnB5 pipe is formed for 6 seconds, if the pressure increase is determined to be lagging, the valve opening is increased by 30%, and the target pressure is adjusted from 28MPa to 30MPa through pressure compensation. If no pressure increase lag is determined, the current gas path control valve opening is kept unchanged, and normal pressure increase is continued according to the initially set target pressure increase rate and target pressure. When the forming condition is isothermal forming, no pressure compensation is required. Only the control valve opening of the gas path corresponding to the gas medium is dynamically adjusted and increased according to the value of pressure deviation and pressure increase rate deviation, so as to adjust the actual pressure increase rate and make the measured pressure increase rate continuously approach the target pressure increase rate. For example, when the aluminum alloy 6061 pipe is formed for 5 seconds, the valve opening is increased by 20% according to the deviation, and then the opening is continuously fine-tuned according to the real-time deviation until the pipe is completely fitted to the mold cavity.

[0058] In the pressurization process of non-isothermal forming, the real-time calculated pressure deviation and pressurization rate deviation are used as the criteria for judgment. The values ​​of these two types of deviations are compared with zero. If the calculated pressure deviation is less than zero, it means the actual pressure at the current sampling time is lower than the target pressure; or if the calculated pressurization rate deviation is less than zero, it means the actual pressurization rate within the preset time period is lower than the target pressurization rate. If either condition is met, it is directly determined that there is a lag in the pressurization process. For example, when the ultra-high strength steel 22MnB5 pipe fitting is formed to 2 seconds, the pressure deviation is -1.8 MPa and the pressurization rate deviation is -0.9 MPa / s. Both deviations are less than zero, indicating a pressurization lag. The deviation values ​​at 4 seconds and 6 seconds are also considered. If both are less than zero, it is determined that the pressurization process is lagging. If the calculated result of the pressure deviation is greater than or equal to zero, and the calculated result of the pressurization rate deviation is also greater than or equal to zero, it means that the current actual pressure has reached or exceeded the target pressure and the actual pressurization rate has reached or exceeded the target pressurization rate. When both conditions are met, it is determined that there is no lag in the pressurization process. For example, when the ultra-high strength steel 22MnB5 pipe fitting is formed to 8s, the pressure deviation is +1.6MPa and the pressurization rate deviation is +0.2MPa / s. Both deviations are greater than zero, so it is determined that there is no pressurization lag. In this way, through clear and quantitative numerical judgment rules, a rapid and accurate judgment on whether the pressurization process is lagging can be achieved, providing a clear judgment result for the subsequent targeted control actions.

[0059] For example, combined Figure 2 As shown, Figure 2 This is the ideal control curve under non-isothermal forming conditions. The horizontal axis represents forming time t, the left vertical axis represents gas pressure P, and the right vertical axis represents temperature T. The orange curve in the figure represents the decrease in billet temperature over time. = The temperature just dropped to the lower limit of the forming temperature. = The blue dashed line represents the target boost rate. The corresponding pressure rise curve, in Pressure to achieve goals at all times The red solid line represents the actual boost rate after real-time increase in boost rate. The corresponding pressure rise curve, this curve is in Real-time synchronization This embodiment increases the pressurization rate in real time, so that the pipe fitting is molded before the billet temperature drops to the forming lower limit, thus avoiding excessive cooling that could lead to forming failure.

[0060] For example, combined Figure 3 As shown, Figure 3 The graph shows the actual control curves under non-isothermal forming conditions. The horizontal axis represents forming time t, the left vertical axis represents gas pressure P, and the right vertical axis represents temperature T. The orange curves in the graph represent the target temperatures of the tube blank. Compared with actual temperature The descent curves of the two show a temperature difference ΔT; the blue dashed line represents the target boost rate. The corresponding pressure rise curve should be in Time to reach The red solid line represents the actual boost rate. The corresponding pressure rise curve shows a time difference Δt due to the pressure lag. Actual pressure Pressure higher than the original target The pressure difference ΔP is the pressure compensation value. In this embodiment, under the scenario of non-isothermal forming pressurization lag, the increased flow stress caused by the temperature drop is compensated by the coordinated regulation of increasing the pressurization rate and compensating for the target pressure, thus ensuring that the pipe fitting is successfully molded.

[0061] In this optional embodiment, a targeted collaborative dynamic adjustment strategy is implemented based on the different forming conditions of isothermal and non-isothermal pipe fittings, combined with pressure deviation and pressurization rate deviation. This achieves precise and adaptive control of pressure and pressurization rate during the forming process. For non-isothermal forming scenarios, the pressure lag is accurately judged by the deviation, and the control valve opening is increased and the target pressure is compensated simultaneously. This not only quickly increases the actual pressurization rate to compensate for the time lag, but also adapts to the problem of increased flow stress caused by pipe blank cooling through pressure compensation. This effectively avoids defects such as insufficient mold application and pipe fitting rupture caused by pressure lag and excessive cooling in non-isothermal forming. For isothermal forming scenarios, only the control valve opening is adjusted. The precise control of the pressurization rate ensures that the measured pressurization rate continuously approaches the target value, adapting to the process requirements of isothermal forming where there is no significant temperature change and only precise control of the strain rate is needed. Simultaneously, the entire adjustment process continues until the pipe fitting is fully molded, achieving dynamic closed-loop control throughout the forming process. This ensures that the actual parameters of pressure and pressurization rate always approach the target parameters, effectively avoiding the parameter mismatch problem under traditional single-pressure control. This significantly improves the controllability and adaptability of the forming process, significantly reducing forming defects such as wrinkling, cracking, and incomplete fillet filling. It guarantees high-quality molded forming of pipe fittings under different forming conditions, while also enhancing the adaptability of the forming process to pipe fittings of different materials and structures.

[0062] By comparing the pressure deviation and pressurization rate deviation with zero as the criteria, a clear, quantifiable, and rapidly executable judgment rule for whether the pressurization process is lagging is established. Pressurization lag is determined as long as either the pressure deviation or the pressurization rate deviation is less than zero; only when both deviations are greater than or equal to zero is no lag determined. This judgment method can directly and quickly identify the lag state of the pressurization process through measured deviation values, without the need for complex calculations or analysis. This ensures the accuracy of the judgment results and enables real-time determination of the lag state, facilitating subsequent control valve opening adjustment under non-isothermal forming conditions. The timely execution of pressure compensation provides a clear and reliable basis for judgment, effectively avoiding control delays caused by ambiguous judgments and untimely identification of lag. It ensures that the coordinated control action can be quickly initiated when the pressure is lag, and timely make up for the time and temperature loss caused by the pressure lag. It prevents forming defects such as insufficient mold application and cracking caused by excessive cooling and increased flow stress in the tube blank. At the same time, the standardized judgment rules make the control logic of the entire dual control system clearer, further improving the timeliness and accuracy of the forming process control, and ensuring the high-quality forming of tubes under non-isothermal forming.

[0063] In one example, taking the non-isothermal hot gas pressure forming of ultra-high strength steel 22MnB5 pipe fittings as an example, the pipe blank has an outer diameter of 80mm, a wall thickness of 1.2mm, and a length of 1350mm. The pipe blank is heated to 910℃, and the mold is at room temperature. Based on the cross-sectional geometry of the part, the minimum inner corner radius is 12mm; considering the material flow stress model, the target pressure value ( The pressure is set to 28 MPa. Based on heat conduction calculations, and considering the time required for the critical fillet region of the tube blank to cool to the lower forming limit temperature of 750°C (tT = 8.5 s), the total forming time (tf) of the part is set to 8 s. The target pressure ramp rate ( The pressure was set to 3.5 MPa / s. The tube blank was heated to 910℃ in a furnace and held for 7 minutes, then transferred to a mold for closing and sealing, with the transfer time controlled within 8 seconds. A pressure sensor (sampling frequency 100Hz) collected pressure data in real time and calculated the measured pressure rise rate. The pressure and pressurization rate during the hot gas forming process of the parts are coordinated and controlled to ensure that the formed parts have full fillets, no cracks, and no wrinkles. Specifically, as shown in Table 1, the pressure deviation = measured pressure - set target pressure. Taking time point 2s as an example, the measured pressure value at this time is 5.2MPa. Based on the target pressurization rate (3.5MPa / s), the set target pressure at this time is calculated to be 3.5×2=7MPa. Therefore, the pressure deviation at 2s is 5.2-7=-1.8MPa. Since the measured pressure at 2s is 5.2MPa, the measured pressurization rate is 5.2 / 2=2.6MPa / s. The pressurization rate deviation is 2.6-3.5=-0.9MPa / s, indicating that the pressurization is slower at 2s.

[0064] Table 1. Record of Coordinated Control of Pressure and Pressure Rise Rate in Non-Isothermal Hot Gas Forming Process of Ultra-High Strength Steel 22MnB5 Pipe Fittings

[0065] In this embodiment of the invention, during the non-isothermal hot gas pressure forming process of ultra-high strength steel 22MnB5 pipe fittings, in each control cycle (e.g., sampling frequency 100Hz), the system adjusts the pressure according to the measured pressure. The target pressure at the current moment is calculated based on the measured pressure and time t, thus obtaining the pressure deviation, i.e., the measured pressure minus the target pressure; simultaneously, the measured pressure rise rate is calculated based on the measured pressure and time. This leads to the deviation in the boost rate.

[0066] In the initial stage of forming, such as at t=2s, the measured pressure of 5.2MPa is lower than the set target pressure of 7.0MPa, and the measured rate of 2.6MPa / s is lower than the target rate of 3.5MPa / s, indicating that the pressurization is lagging. The system determines that the energy is insufficient and executes control actions such as increasing the valve opening. In the middle stage of forming, such as at t=4s, although the pressure deviation ΔP and the pressurization rate deviation ΔV are still negative, the absolute values ​​of the deviations gradually decrease, and the system activates the temperature compensation model and pressure compensation model based on heat conduction calculations. The pressure was increased to 30 MPa to accommodate the temperature drop and increased deformation resistance of the tube blank due to contact with the cold mold.

[0067] When the time progressed to t=8.1s, close to the total forming time calculated based on heat conduction, the measured pressure... = 30.0 MPa exactly reaches the compensated target pressure (30 MPa), and the measured pressure rise rate is... = 3.7MPa / s matches the adjusted target rate, and the pressure deviation ΔP = +2.0MPa and the pressure rise rate deviation ΔV = +0.2MPa / s are within the preset allowable range, indicating that the pipe has filled the mold cavity, and the deformation resistance naturally increases, causing the pressure and rate to reach the preset target. At this time, the control system, combining the three conditions of the forming time being close to the thermodynamic time window, the deviation being within the allowable range, and the pressure reaching the compensated target value, determines that the pipe to be formed is completely attached to the mold, and then stops dynamic control and enters the pressure holding and shaping stage. This embodiment calculates the pressure deviation and pressure rise rate deviation in real time, observes whether they eventually converge to the vicinity of the compensated target value under coordinated control, and makes a comprehensive judgment on whether the mold attachment is completed in combination with the forming time window.

[0068] In another example, taking the isothermal hot gas forming of 6061 aluminum alloy pipe fittings as an example, the pipe blank has an outer diameter of 60mm, a wall thickness of 1.5mm, and a length of 280mm. Both the pipe blank and the mold are heated to 420℃. Based on the cross-sectional geometry of the part, the minimum inner corner radius is 6mm; considering the material flow stress model, the target pressure value ( The pressure is set to 25 MPa. Based on the part's deformation and the optimized strain rate in the process window, the total forming time (tf) is set to 21 s. The target pressure ramp rate ( The pressure is set to 1.2 MPa / s. Since the mold and the tube blank are in an isothermal state, no temperature compensation is required. The control strategy focuses on precise tracking of the pressure increase rate, pressure lag compensation, and control of the forming time window. A pressure sensor (sampling frequency 100 Hz) collects pressure data in real time and calculates the measured pressure increase rate. The pressure and pressurization rate during the hot gas forming process of the parts are coordinated and controlled, resulting in fully filled rounded corners and a surface free of orange peel or cracks. Details are shown in Table 2 below.

[0069] Table 2. Record of Coordinated Control of Pressure and Pressure Rise Rate during Isothermal Hot Gas Forming of Aluminum Alloy 6061 Pipe Fittings

[0070] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A method for hot gas pressure forming of pipe fittings with dual control of pressure and pressurization rate, characterized in that, include: Obtain forming process parameters for multiple pipe fittings to be formed, including the target pressure and target pressure increase rate required for forming each pipe fitting. After multiple tubes to be formed are placed in their respective molds, the tubes to be formed in the molds are pressurized, and during the pressurization process, the actual pressure and actual pressurization rate of the gas medium acting on the tubes to be formed are obtained in real time. Based on the target pressure, the target pressure increase rate, the actual pressure, and the actual pressure increase rate, the pressure deviation and pressure increase rate deviation of the gas medium are determined. Based on the pressure deviation and the pressure rise rate deviation, the gas medium is dynamically adjusted in a coordinated manner until the tube to be formed is completely fitted to the mold.

2. The hot gas pressure forming method for pipe fittings with dual control of pressure and pressurization rate according to claim 1, characterized in that, The step of obtaining the forming process parameters corresponding to multiple tubes to be formed includes: The target pressure is determined by combining the material properties, cross-sectional geometry, and forming type of each of the tubes to be formed; The forming time is determined based on the process constraints corresponding to the forming type. The target pressure increase rate is determined by combining the forming time and the target pressure.

3. The hot gas pressure forming method for pipe fittings with dual control of pressure and pressurization rate according to claim 1, characterized in that, When multiple tubular components to be formed are placed in corresponding molds, the tubular components to be formed in the molds are pressurized respectively, including: Each of the tubes to be formed is heated to a preset forming temperature, and the tubes to be formed at the preset forming temperature are placed into the cavity of the mold for mold closing operation; After the mold is closed, the mold is sealed, and then the gas medium is introduced into the cavity of the sealed mold. Each of the tubes to be formed is pressurized according to the target pressurization rate and the target pressure.

4. The hot gas pressure forming method for pipe fittings with dual control of pressure and pressurization rate according to claim 1, characterized in that, The real-time acquisition of the actual pressure and actual pressure rise rate of the gas medium acting on the tube to be formed includes: The actual pressure of the gas medium inside the mold cavity is collected at a preset sampling frequency by a pressure detection element installed in the gas path communicating with the cavity of the mold. The actual pressure rise rate of the gas medium is determined based on the actual pressure at all sampling times within the preset current time period and the sampling time difference between each sampling time.

5. The hot gas pressure forming method for pipe fittings with dual control of pressure and pressurization rate according to claim 4, characterized in that, The determination of the pressure deviation and pressure rise rate deviation of the gas medium based on the target pressure, the target pressure rise rate, the actual pressure, and the actual pressure rise rate includes: The pressure deviation of the gas medium at the current sampling time is obtained by calculating the difference between the actual pressure at the current sampling time and the target pressure. The difference between the target pressure increase rate and the actual pressure increase rate within the preset current time period is calculated to obtain the pressure increase rate deviation of the gas medium within the preset current time period.

6. The hot gas pressure forming method for pipe fittings with dual control of pressure and pressurization rate according to claim 5, characterized in that, The step of dynamically adjusting the gas medium based on the pressure deviation and the pressure rise rate deviation until the tube to be formed completely fits the mold includes: Based on the forming conditions of the tube to be formed, and in combination with the pressure deviation and the pressure rise rate deviation, an adjustment strategy for the gas medium is determined. According to the adjustment strategy, the gas medium is dynamically adjusted in a coordinated manner until the tube to be formed is completely fitted to the mold.

7. The hot gas pressure forming method for pipe fittings with dual control of pressure and pressurization rate according to claim 6, characterized in that, The forming conditions include non-isothermal forming. The step of determining an adjustment strategy for the gas medium based on the forming conditions of the pipe to be formed, combined with the pressure deviation and the pressure rise rate deviation, includes: When the forming condition is non-isothermal forming, it is determined whether the pressurization process is delayed based on the pressure deviation and the pressurization rate deviation. If so, the pressure compensation value of the target pressure is obtained, and the opening adjustment value of the control valve of the gas path corresponding to the gas medium is determined according to the preset rules; an adjustment strategy for the gas medium is formed according to the pressure compensation value and the opening adjustment value. If not, continue pressurizing according to the target pressurization rate and the target pressure.

8. The hot gas pressure forming method for pipe fittings with dual control of pressure and pressurization rate according to claim 7, characterized in that, The step of determining whether the pressurization process is delayed based on the pressure deviation and the pressurization rate deviation includes: Determine whether the pressure rise rate deviation and the pressure deviation are less than zero; If the pressure increase rate deviation is less than zero, and / or the pressure deviation is less than zero, then the pressure increase process is determined to be delayed. If both the pressure increase rate deviation and the pressure deviation are not less than zero, then the pressurization process is determined to be not delayed.

9. The hot gas pressure forming method for pipe fittings with dual control of pressure and pressurization rate according to claim 6, characterized in that, The forming conditions include isothermal forming. The step of determining an adjustment strategy for the gas medium based on the forming conditions of the pipe to be formed, combined with the pressure deviation and the pressure rise rate deviation, includes: When the forming condition is isothermal forming, the opening value of the control valve corresponding to the gas medium in the gas path is adjusted upward according to the preset rule. Based on the opening adjustment value, an adjustment strategy for the gas medium is formed.

10. The hot gas pressure forming method for pipe fittings with dual control of pressure and pressurization rate according to claim 6, characterized in that, The step of determining whether the pressurization process is delayed based on the pressure deviation and the pressurization rate deviation includes: When the pressure deviation is less than zero or the pressure increase rate deviation is less than zero, it is determined that there is a lag in the pressure increase process; When both the pressure deviation and the pressurization rate deviation are greater than or equal to zero, it is determined that there is no lag in the pressurization process.

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