Plate frame forming method and system, mouth frame for rocket and carrier rocket

Abstract

The embodiment of the invention provides a plate frame forming method and system, a mouth frame for a rocket and a carrier rocket. The plate frame forming method comprises the steps that a plate above the solid solution temperature is put into a stretching die to complete stretching of the plate; the stretched plate frame continues to be clamped in the stretching die, under the condition that it is monitored that the temperature of the plate frame is not lower than the solid solution temperature, a cooling medium is injected into the stretching die, and quenching of the plate frame is started; when it is monitored that the temperature of the plate frame is reduced to the quenching finishing temperature, the quenched plate frame is taken out of the stretching die; and aging treatment is conducted on the plate frame. The plate is heated to be above the lower limit of the solid solution temperature, the plate is always clamped in the stretching die during stretching and quenching, a low-temperature cooling medium is injected through a cooling medium runner in the die, the cooling speed of quenching is increased, precipitation of a strengthening phase is avoided, and therefore the shape precision and strength of the mouth frame for the rocket can be guaranteed.

Description

Technical Field

[0001] This invention relates to the field of rocket manufacturing, and in particular to a method and system for forming sheet metal frames, rocket mouth frames, and launch vehicles. Background Technology

[0002] Rocket entry frames (a type of sheet metal frame) are important sheet metal parts in rocket structures. They are mainly installed on the edge of the rocket compartment entry, serving to strengthen the rigidity around the entry. With the development of rocket technology, rocket entry frames have also become important force transmission structures, and their thickness has gradually increased, with higher strength requirements.

[0003] Traditional sheet metal frames are made of aluminum alloy sheets such as 2A12 or 2A14, which are cold-formed using molds, followed by quenching and aging treatment. However, the quenched sheet metal frames have significant quenching stress, making them prone to deformation and requiring manual reshaping. This results in a long and inefficient process, especially for thicker and larger sheets where the quenching stress is greater, making subsequent manual reshaping difficult.

[0004] To address the challenges of difficult sheet metal part shaping, poor dimensional stability, and low efficiency, there are domestic cases of integrating thermoforming and quenching, which can solve the shaping difficulties to some extent. However, these methods suffer from low quenching cooling rates and the inability to fully quench thicker sheet metal parts. Furthermore, the proposed methods carry the risk of low strength and cannot provide a solution that can solve the shaping difficulties, ensure dimensional stability, and significantly improve the strength of the sheet metal frame.

[0005] In the process of developing this invention, the applicant discovered at least the following problems in the prior art: Traditional plate frame quenching processes cannot simultaneously achieve high quenching efficiency, low stress, dimensional stability, and high strength. Summary of the Invention

[0006] This invention provides a method, system, rocket frame, and launch vehicle for forming sheet metal frames, thereby at least solving the problem that traditional sheet metal frame quenching processes cannot simultaneously achieve high quenching efficiency, low stress, dimensional stability, and high strength.

[0007] To achieve the above objectives, in one aspect, embodiments of the present invention provide a method for forming a sheet metal frame, comprising: placing a sheet metal at a solution temperature above a certain level into a stretching die and stretching the sheet metal to form a sheet metal frame; continuing to hold the sheet metal frame in the stretching die; when the temperature of the sheet metal frame is monitored to be no lower than the solution temperature, injecting a cooling medium into the stretching die to begin quenching the sheet metal frame; when the temperature of the sheet metal frame is monitored to drop to the quenching end temperature, removing the quenched sheet metal frame from the stretching die; and performing an aging treatment on the sheet metal frame; wherein the boiling point of the cooling medium is below -130°C.

[0008] Furthermore, the step of injecting cooling medium into the stretching die includes: determining the flow rate of the cooling medium injected into the stretching die based on the thickness of the stretched plate frame, so that the plate frame cools down to the quenching end temperature at a preset cooling rate.

[0009] Furthermore, the stretching die includes a punch and a die; the punch has a first cooling medium channel, and the distance from the sidewall of the first cooling medium channel near the working surface of the punch to the working surface of the punch is 10-30 mm; the die has a second cooling medium channel, and the distance from the sidewall of the second cooling medium channel near the working surface of the die to the working surface of the die is 10-30 mm.

[0010] Furthermore, the overall shape of the first cooling medium channel and / or the second cooling medium channel matches the shape of the plate frame.

[0011] Furthermore, the material of the plate is aluminum alloy; the thickness of the plate is less than or equal to 10 mm.

[0012] Furthermore, the cooling medium includes liquid nitrogen or cold helium.

[0013] Furthermore, the preset cooling rate is greater than or equal to 70℃ / s.

[0014] Furthermore, the plate frame forming method includes: placing the plate in a heat treatment furnace and heating it to above the solution temperature, holding it at that temperature for 30-180 minutes; placing the heat-held plate in the stretching die, and stretching the plate within 5-10 seconds to obtain the plate frame; continuing to hold the stretched plate frame in the stretching die, and controlling the flow rate of the cooling medium injected into the cooling medium channel of the stretching die to 0.5-1.5 m / s while ensuring that the temperature of the plate frame is not lower than the lower limit of the solution temperature, and starting quenching; after the temperature of the quenched plate frame drops to -130~-110℃, removing the quenched plate frame; and performing an aging treatment on the plate frame.

[0015] Furthermore, the flow rate of the cooling medium is 0.2~2.0 m / s.

[0016] On the other hand, embodiments of the present invention provide a sheet metal frame forming system, employing any of the methods described above, including: The system includes a control system, a temperature monitoring system and a cryogenic medium storage and circulation system connected to the control system, a stretching die connected to the temperature monitoring system, and a cryogenic cooling system disposed within the stretching die, wherein the cryogenic cooling system is connected to the cryogenic medium storage and circulation system. Furthermore, the control system is used to receive the temperature of the plate collected by the temperature monitoring system, and trigger the stretching die to stretch the plate according to the temperature of the plate, and trigger the low temperature medium storage and circulation system to quench the stretched plate. A stretching die is used to stretch the sheet material when the temperature of the sheet material is higher than the solution temperature, triggered by the control system, and to continue clamping the sheet material during quenching to complete the quenching process; the stretching die is equipped with a low-temperature cooling system, which is used to inject a cooling medium during quenching. A cryogenic medium storage and circulation system is used to inject cooling medium into the cryogenic cooling system in the stretching die when the temperature of the stretched sheet is not lower than the solution temperature, thereby quenching the sheet clamped in the stretching die. The cryogenic medium storage and circulation system includes a cryogenic medium storage container, which includes an inlet and an outlet. The outlet pipeline is connected to a pump, flow meter, and other equipment for controlling the flow of the cryogenic medium. When the pump is started, the cryogenic medium can flow into the cryogenic cooling system in the stretching die.

[0017] The temperature monitoring system is used to collect the temperature of the sheet metal before stretching, after stretching, and during quenching, and provide this data to the control system.

[0018] Furthermore, the cryogenic cooling system includes multiple cooling medium flow channels; The diameter of the cooling medium channels is 3~8mm, and the spacing between adjacent reciprocating cooling medium channels is 30~50mm. The cooling medium channels are evenly distributed below the working surface of the stretching die to cool the sheet metal clamped on the working surface.

[0019] Furthermore, the drawing die includes a punch and a die; the cooling medium flow channel includes a first cooling medium flow channel for cooling the punch and a second cooling medium flow channel for cooling the die; The punch is provided with a first cooling medium flow channel, and the distance from the side wall of the first cooling medium flow channel near the working surface of the punch to the working surface of the punch is 10~30 mm. A second cooling medium channel is provided inside the die cavity. The distance from the side wall of the second cooling medium channel near the working surface of the die cavity to the working surface of the die cavity is 10~30 mm.

[0020] Furthermore, the control system determines the flow rate of the cooling medium injected into the stretching die based on the thickness of the stretched plate frame, so that the plate frame cools down to the quenching end temperature at a preset cooling rate.

[0021] In addition, this embodiment of the invention also provides a rocket mouth frame, which is made by the method described above and then laser-cut to obtain the rocket mouth frame.

[0022] Meanwhile, embodiments of the present invention also provide a launch vehicle, which includes a rocket port frame installed in the rocket section, the rocket port frame being manufactured using the method described above.

[0023] The above technical solution has the following beneficial effects: heating the plate to above the lower limit of the solution temperature, and keeping the plate in the stretching die during stretching and quenching, combined with the injection of low-temperature cooling medium through the cooling medium channel in the die, improves the cooling rate of quenching and avoids the precipitation of strengthening phase, thereby ensuring the shape accuracy and strength of the rocket's mouth frame. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a flowchart of a plate frame forming method according to one embodiment of the present invention; Figure 2 This is an architectural diagram of a sheet metal frame forming system according to one embodiment of the present invention; Figure 3 This is a cross-sectional schematic diagram of a stretching die according to one embodiment of the present invention; Figure 4 This is a three-dimensional schematic diagram of a plate frame according to one embodiment of the present invention; Figure 5 This is a schematic diagram of the temperature change curves of the board material corresponding to each process stage in one of the embodiments of the present invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] like Figure 1 As shown, an embodiment of the present invention provides a method for forming a sheet metal frame, which includes: Step S10: Place the sheet material with a solution temperature above the lower limit into the stretching die and stretch the sheet material to form a sheet frame; Step S11: Continue to clamp the plate frame in the stretching die. If the temperature of the plate is not lower than the solution temperature, inject the cooling medium into the stretching die to start quenching the plate frame. Step S12: When the temperature of the plate is detected to drop to the quenching end temperature, remove the quenched plate from the stretching die; Step S13: Perform aging treatment on the board frame; The boiling point of the cooling medium is below -130℃.

[0028] In some embodiments, the plate material above the solution temperature can be heated to above the solution temperature by placing the plate material in a heat treatment furnace and holding it at that temperature for a predetermined time. The solution temperature of the plate material is a temperature range between the lower limit of the solution temperature and the upper limit of the solution temperature. The solution temperature range of different plates can be obtained experimentally and is common knowledge in the art. The solution temperature in steps S10 and S11 can be within the solution temperature range and must be a temperature that ensures the plate material will not overheat during the heating and holding process.

[0029] Preferably, the specific heating temperature exceeds the lower limit of the solution temperature by approximately 5°C to 15°C. Alternatively, for aluminum alloys, a higher solution temperature is selected to maximize the solution strengthening effect while ensuring the material does not overheat; a lower temperature results in poor solution effect and lower strength after aging. Heating the sheet to this temperature range before quenching allows the resulting component to achieve a balance between strength and toughness. For example, for aluminum alloys, especially 2A12-O or 2A12 aluminum alloys, heating to a solution temperature of 497~504°C, and for 2A14-O or 2A14 aluminum alloys, heating to a solution temperature of 492~505°C. The goal of heat preservation is to allow the sheet to retain sufficient heat so that its temperature remains above the lower limit of the solution temperature during subsequent processes before quenching, and at the start of quenching, the sheet temperature is kept no lower than the lower limit of the solution temperature.

[0030] The specific length of the predetermined heat preservation time can be obtained through actual measurement based on the specific production environment. For aluminum alloy sheets with a thickness of no more than 8 mm, the predetermined heat preservation time is 30~180 minutes. For example, for a 6 mm thick 2A14-O temper aluminum alloy sheet, the predetermined heat preservation time is 60 minutes; for a 7 mm thick 2A12-O temper aluminum alloy sheet, the predetermined heat preservation time is 90 minutes; and for a 4 mm thick 2A12-O temper aluminum alloy sheet, the predetermined heat preservation time is 90 minutes.

[0031] The heat-insulated sheet material is quickly placed into a stretching die to complete the stretching process. The heated sheet material needs to be transferred to the stretching die and stretched rapidly because it requires quick shaping. Prolonged transfer will cause the sheet to cool, compromising the temperature required for subsequent quenching. This leads to a decrease in the supersaturation of the solid solution after quenching, resulting in reduced plasticity after aging and increased susceptibility to cracking during stretching. The longer the transfer time, the greater the loss of plasticity. Preferably, the heat-insulated sheet material is placed into the stretching die and stretched within 5-15 seconds to form a sheet frame, such as a rocket nozzle frame. One method is to integrate the heat treatment furnace with the stretching die to reduce temperature loss during transfer, controlling the transfer time to within 10 seconds. Another method is to use a robotic arm to quickly place the heated sheet material into the stretching die of the stretching equipment to complete the stretching process in the shortest possible time. Preferably, quenching can begin within 3-5 seconds after stretching.

[0032] The stretched sheet frame is held in the stretching die. While monitoring the sheet frame temperature to ensure it is not lower than the lower limit of the solid solution temperature, cooling medium is injected into the cooling medium channel of the stretching die to begin quenching the sheet frame. The sheet frame is cooled to the quenching end temperature at a quenching rate greater than or equal to 70 degrees Celsius per second, preferably at a quenching rate greater than or equal to 80°C / s, 85°C / s, 90°C / s, 95°C / s, or 100°C / s. The quenching end temperature is lower than or equal to -110°C. At this temperature and below, a highly supersaturated solid solution can be obtained, and the supersaturated solid solution will not decompose. Compared to room temperature cooling medium, this provides a more sufficient kinetic basis for subsequent aging precipitation, significantly improving the mechanical properties after aging. Furthermore, the minimum temperature is related to the cooling medium and is the boiling point of the cooling medium. For example, when liquid nitrogen is used as the cooling medium, the minimum temperature is not lower than -193°C. Preferably, the quenching end temperature range for aluminum alloys is -130 to -110°C. Quenching to approximately -130°C using a low-temperature cooling medium, and increasing the quenching rate, can significantly improve the strength of the aluminum alloy. Under low-temperature conditions, the supersaturation of the metal can be significantly increased, providing sufficient power for subsequent age hardening, resulting in a significant increase in the metal's strength after aging.

[0033] When the temperature of the plate frame drops to the quenching end temperature, the quenched plate frame is removed from the stretching die; the plate is then aged to obtain the rocket mouth frame; the second phase is precipitated through aging (natural aging and artificial aging) to improve the strength of the material.

[0034] The design incorporates cooling medium channels parallel to the working surface of the stretching die. After stretching, the sheet metal frame remains clamped within the die, preventing springback and warping due to thermal stress during quenching and cooling, thus ensuring forming accuracy. This is particularly suitable for curved surfaces and high-precision sheets. Quenching is initiated when the sheet metal frame temperature is not lower than the lower limit of the solution cooling temperature, inhibiting premature precipitation of solute atoms and ensuring the supersaturation of the solid solution, which is beneficial for subsequent aging strength. The sheet metal frame after solution heat stretching requires rapid cooling to dissolve solute atoms into the matrix lattice; if the sheet metal frame temperature is too low before quenching and cooling, the motivation for solute atom precipitation is insufficient, leading to a significant decrease in strengthening effect. The method of injecting cooling medium into the stretching die's cooling medium channels allows for a uniform and controllable cooling rate. The flow rate of the cooling medium in the cooling medium channel of the drawing die can be controlled. The orifice diameter of the cooling medium channel is designed according to the size of the drawing die, generally φ3~φ8mm, and the flow rate is controlled between 0.2~2.0m / s. If the flow rate is too fast, the internal stress of quenching will be too large, which may lead to cracking. If it is too slow, the cooling efficiency will be insufficient. Therefore, 0.5~1.5m / s is preferred. Aging treatment refers to the heat treatment process in which metal or alloy workpieces, after solution treatment, high-temperature quenching or a certain degree of cold working deformation, are placed at a relatively high temperature or room temperature to maintain their shape, size, and properties over time. In this technical solution, aging treatment includes artificial aging and natural aging. For example, for aluminum alloys, artificial aging should be performed when 2A14-O state aluminum alloy is selected, and natural aging should be performed when 2A12-O state aluminum alloy is selected.

[0035] The embodiments of this invention have the following technical effects: They achieve an integrated process for forming and quenching sheet metal frames (e.g., rocket nozzle frames), significantly improving production efficiency and surface accuracy compared to traditional room-temperature stretching and quenching processes. The low-temperature quenching process used achieves a quenching speed greater than or equal to 80℃ / s, enabling thorough quenching even for thicker parts, such as those no more than 8 mm thick. The quenched aluminum alloy generates residual compressive stress at low temperatures, and combined with the integrated hot forming and quenching process design, its surface accuracy and dimensional stability are significantly improved. Furthermore, the aluminum alloy after low-temperature quenching exhibits high supersaturation of the solid solution, resulting in better dispersion precipitation after aging, and its strength is increased by more than 10% compared to room-temperature quenching. The forming equipment has online temperature monitoring and flow control functions, enabling monitoring of the sheet metal temperature before quenching to ensure material strength after quenching. It can also detect the sheet metal temperature after low-temperature quenching, utilizing the strengthening mechanism of aluminum alloys at low temperatures to ensure the precipitation of a large amount of dispersed second phase after quenching and aging, thereby improving material strength. The deviation between the inner surface of the rocket mouth frame obtained based on the embodiments of the present invention and the theoretical surface is 0.3~0.35mm, the tensile strength is 460~480 MPa, the yield strength is 314~420 MPa, and the elongation is 15%~21%.

[0036] Furthermore, the material of the sheet is aluminum alloy; the thickness of the sheet is less than or equal to 10 mm, for example, 0.5-9 mm. More preferably, the thickness of the sheet is 1-8 mm, which, when used with the method of this embodiment, results in high quenching efficiency, low stress, dimensional stability, and high strength.

[0037] Furthermore, the cooling medium includes liquid nitrogen or cold helium. Liquid nitrogen can reach a temperature of -193°C, while cold helium can be in gaseous or liquid state, with a boiling point of -268°C. Using liquid nitrogen or cold helium as the cooling medium can rapidly reduce the temperature of the plate material to ensure a quenching rate greater than or equal to 70°C / s, preferably greater than or equal to 80, 85, 90, 95, or 100°C / s. The cooling medium is selected based on a boiling point below or equal to -130°C, with chemically inert media being preferred.

[0038] Further, injecting cooling medium into the stretching die includes: determining the flow rate of the cooling medium injected into the stretching die based on the thickness of the stretched sheet, so that the sheet cools down to the quenching end temperature at a rate greater than or equal to 70°C / s, preferably at a rate greater than or equal to 80, 85, 90, 95 or 100°C / s; the preferred cooling rate is 80~100°C / s; for example, the flow rate is determined according to the sheet thickness and (low temperature) cooling medium flow rate comparison table in Table 1.

[0039]

[0040] Table 1 Comparison of Plate Thickness and Low-Temperature Cooling Medium Flow Rate Preferably, the cooling medium is injected into the cooling medium channel at a flow rate of 1.5 meters per second. The faster the flow rate of the cooling medium, the greater the cooling effect. Injecting the cooling medium into the cooling medium channel at a flow rate of 1.5 meters per second ensures that the quenching rate is greater than or equal to 70°C / s. Preferably, the quenching rate is greater than or equal to 80, 85, 90, 95, or 100°C / s.

[0041] In some embodiments, the control system 200 (e.g., a computer or PLC) determines the flow rate of the cooling medium injection based on the thickness of the stretched sheet. Simultaneously, the temperature monitoring system 204 monitors the cooling rate of the sheet in real time. If the cooling rate is too low, the flow rate of the injected cooling medium is gradually increased to improve the cooling rate. If the cooling rate is too high, the flow rate of the injected cooling medium is gradually decreased to reduce the cooling rate, ultimately adjusting the quenching cooling rate to the desired level. In some embodiments, a PID algorithm can be applied to adjust the flow rate of the injected cooling medium. By monitoring the sheet cooling rate in real time, the quenching cooling process can be accurately controlled, improving the desired quenching effect.

[0042] Furthermore, the stretching die includes a punch and a die; the punch is provided with a first cooling medium channel, and the distance from the side wall of the first cooling medium channel near the working surface of the punch to the working surface of the punch is 10~30 mm; the die is provided with a second cooling medium channel, and the distance from the side wall of the second cooling medium channel near the working surface of the die to the working surface of the die is 10~30 mm.

[0043] In some embodiments, a distance of less than 10 mm from the cooling medium channel to the working surface increases the manufacturing difficulty of the drawing die, while a distance greater than 30 mm reduces the cooling effect. A distance between 10 and 30 mm from the cooling medium channel to the working surface allows for easy manufacturing of the drawing die while maintaining the aforementioned quenching speed.

[0044] Furthermore, for large-diameter plate frames (such as rocket mouth frames with a radius of curvature of 1700~2100 mm and an arc length of 400~600 mm), tensile quenching is more prone to problems such as deformation and failure to meet strength requirements. By controlling the time and temperature of each step through the embodiments of the present invention, it is possible to ensure that the processing of large-diameter components can achieve the effects of high quenching efficiency, low stress, dimensional stability and high strength.

[0045] Furthermore, the first and second cooling medium channels should be designed to conform to the shape of the plate frame, for example, they can be continuously curved, reciprocating serpentine channels. The diameter of the cooling medium channels is 3-8mm, and the spacing between adjacent reciprocating cooling medium channels is 30-50mm. The cooling medium channels are evenly distributed below the working surface, which can uniformly cool the plate held by the working surface.

[0046] Furthermore, in a specific example, the sheet metal frame forming method may include: The sheet material is placed in a heat treatment furnace and heated to above the solution temperature, and held for 30 to 180 minutes. The sheet material is made of aluminum alloy and the thickness of the sheet material is less than or equal to 10 mm. The insulated sheet material is placed into the stretching mold, and the stretching of the sheet material is completed within 5 to 10 seconds to obtain the sheet material frame; The stretched plate frame continues to be held in the stretching die. When the temperature of the plate frame is not lower than the lower limit of the solid solution temperature, the flow rate of the cooling medium injected into the cooling medium channel of the stretching die is controlled to be 0.5~1.5m / s, and quenching begins. After the temperature of the quenched plate frame drops to -130℃~-110℃, the quenched plate frame is taken out. The plate frame is subjected to aging treatment.

[0047] Furthermore, in a specific example, the sheet metal frame forming method may include: The sheet material is placed in a heat treatment furnace and heated to 500℃~504℃, and held for 90~180 minutes; the sheet material is 4 mm thick 2A12-O state aluminum alloy. The insulated board frame is quickly placed into the stretching mold, and the stretching of the board is completed within 5 to 10 seconds. The stretched sheet frame continues to be clamped in the stretching die. The temperature of the sheet is monitored to be no less than 497℃. The flow rate of the cooling medium injected into the stretching die is controlled to be 0.5~1.5m / s. The cooling medium is liquid nitrogen. Quenching begins. Once the temperature of the quenched plate has dropped to -130~-110℃, remove the quenched plate. After the board material returns to room temperature and is allowed to stand naturally for more than 96 hours, natural aging is completed, and then laser cutting is performed to obtain the rocket mouth frame. Among them, the inner surface of the rocket's mouth frame deviates from the theoretical surface by 0.3 mm, the tensile strength is 460 MPa, the yield strength is 315 MPa, and the elongation is 21%.

[0048] Furthermore, in another specific example, the sheet metal frame forming method may include: The sheet material is placed in a heat treatment furnace and heated to 500℃~504℃, and held for 90~180 minutes; the sheet material is 7 mm thick 2A12-O state aluminum alloy. The insulated board is quickly placed into the stretching die, and the stretching of the board is completed within 5 to 10 seconds. The stretched sheet frame continues to be clamped in the stretching die. The temperature of the sheet is monitored to be no less than 497℃. The flow rate of the cooling medium injected into the stretching die is controlled to be 0.5~1.5m / s. The cooling medium is liquid nitrogen. Quenching begins. Once the temperature of the quenched plate has dropped to -130~-110℃, remove the quenched plate. After the board material returns to room temperature and is allowed to stand naturally for more than 96 hours, natural aging is completed, and then laser cutting is performed to obtain the rocket mouth frame. Among them, the inner surface of the rocket's mouth frame deviates from the theoretical surface by 0.3 mm, the tensile strength is 465 MPa, the yield strength is 314 MPa, and the elongation is 20.5%.

[0049] Furthermore, in another specific example, the sheet metal frame forming method may include: The sheet material is placed in a heat treatment furnace and heated to 495~501℃, and held for 60~180 minutes; the sheet material is 6 mm thick 2A14-O state aluminum alloy. The insulated board is quickly placed into the stretching die, and the stretching of the board is completed within 5 to 10 seconds. The stretched sheet frame continues to be clamped in the stretching die. The temperature of the sheet is monitored to be no less than 490℃. The flow rate of the cooling medium injected into the stretching die is controlled to be 0.5~1.5m / s. The cooling medium is liquid nitrogen. Quenching begins. Once the temperature of the quenched plate has dropped to -130~-110℃, remove the quenched plate. The sheet material is placed in an aging furnace for artificial aging, and then laser-cut to obtain the rocket mouth frame; The inner surface of the rocket's mouth frame deviates from the theoretical surface by 0.35 mm, has a tensile strength of 480 MPa, a yield strength of 420 MPa, and an elongation of 15%.

[0050] like Figure 2 As shown, an embodiment of the present invention provides a sheet metal frame forming system, employing any of the methods described above. The system includes: The system includes a control system 200, a temperature monitoring system 204 and a cryogenic medium storage and circulation system 203 connected to the control system 200, a stretching die 201 connected to the temperature monitoring system 204, and a cryogenic cooling system 202 disposed in the stretching die 201, wherein the cryogenic cooling system 202 is connected to the cryogenic medium storage and circulation system 203. The control system 200 is used to receive the temperature of the plate collected by the temperature monitoring system 204, and trigger the stretching die 201 to stretch the plate according to the temperature of the plate, and trigger the low temperature medium storage and circulation system 203 to quench the stretched plate. The stretching die 201 is used to stretch the sheet material when the temperature of the sheet material is higher than the solution temperature, triggered by the control system 200, and to continue to hold the sheet material during quenching to complete the quenching process; the stretching die 201 is equipped with a low-temperature cooling system 202, which is used to inject a cooling medium during quenching. The low-temperature medium storage and circulation system 203 is used to inject cooling medium into the low-temperature cooling system 202 in the stretching die 201 when the temperature of the stretched plate is not lower than the solution temperature, so as to complete the quenching of the plate held in the stretching die 201. Temperature monitoring system 204 is used to collect the temperature of the sheet metal before stretching, after stretching, and during quenching and provide it to control system 200.

[0051] The stretching die 201 includes a punch 2011 and a die 2012; the cooling medium flow channels include a first cooling medium flow channel 2021 and a second cooling medium flow channel 2022; the first cooling medium flow channel 2021 is provided inside the punch 2011, and the distance from the sidewall of the first cooling medium flow channel 2021 near the working surface of the punch 2011 to the working surface of the punch 2011 is 10~30 mm; the second cooling medium flow channel 2022 is provided inside the die 2012, and the distance from the sidewall of the second cooling medium flow channel 2022 near the working surface of the die 2012 to the working surface of the die 2012 is 10~30 mm. The overall shape of the first cooling medium flow channel 2021 and / or the second cooling medium flow channel 2022 matches the shape of the sheet metal frame. Specifically, the overall shape of the first cooling medium flow channel 2021 and / or the second cooling medium flow channel 2022 is approximately consistent with the radius of curvature and arc length of the corresponding plate frame. The outer edges of the first cooling medium flow channel 2021 and / or the second cooling medium flow channel 2022 are approximately the same size as or slightly larger than the plate frame. The area formed by the outer edges of the first cooling medium flow channel 2021 and / or the second cooling medium flow channel 2022 is 1 to 1.2 times the area of ​​the plate frame. This design improves the cooling speed because the plate frame is curved. The curvature of the first cooling medium flow channel 2021 and / or the second cooling medium flow channel 2022 is consistent with the plate frame, avoiding poor cooling performance in some curved areas. The area formed by the outer edges of the first cooling medium flow channel 2021 and / or the second cooling medium flow channel 2022 is 1 to 1.2 times the area of ​​the plate frame, ensuring consistent cooling effect between the edges and center of the plate frame.

[0052] The technical solutions of the present invention will be described in detail below with reference to specific application examples. For technical details not described in the implementation process, please refer to the relevant descriptions above.

[0053] To address the above problems, this invention provides a method for improving the dimensional accuracy and performance of a plate frame. Compared with traditional methods, this method not only significantly improves the surface accuracy and dimensional stability of the plate frame after quenching, but also increases the strength of the plate frame by 20%.

[0054] This invention utilizes a mold to achieve thermoforming of a sheet metal frame. The temperature of the formed frame is controlled within the solution treatment temperature range. A low-temperature cooling medium flows through an integrated cooling medium channel in the stretching mold. Because the cooling medium's temperature can be as low as -193°C, the quenching speed of the aluminum alloy quenching medium can reach greater than or equal to 80°C / s, allowing even parts with a thickness of 8mm to be thoroughly quenched. The quenched aluminum alloy generates residual compressive stress at low temperatures. Combined with the integrated thermoforming and quenching process design, its surface accuracy and dimensional stability are significantly improved. Furthermore, the low-temperature quenched aluminum alloy exhibits a large number of dispersed precipitates, increasing its strength by 10% compared to conventional quenching processes. After solution quenching, heating promotes the precipitation of the second phase in the supersaturated solid solution, thereby increasing strength.

[0055] To ensure the surface accuracy and dimensional stability of the sheet metal frame and improve the mechanical properties of the parts, this invention provides a method for improving the dimensional accuracy and performance of the sheet metal frame, the specific steps of which include: Step 1: Cut the O-state aluminum alloy sheet, such as 2A12 or 2A14, which can be heat-treatable and strengthened, into blanks. Place the blanks into a heat treatment furnace and heat them to above the solution temperature, and hold them at that temperature for a certain period of time.

[0056] Step 2: The heated sheet metal is quickly placed into the stretching die of the stretching equipment by the robotic arm. The stretching of the sheet metal is completed within 5 to 15 seconds. During the stretching process, the concave die remains stationary while the convex die moves downward. The stretching and forming of the sheet metal frame is completed when the workpiece is completely pressed into the convex die. Step 3: After stretching, the part continues to be in contact with the die and the sheet metal frame, and is quenched within 5 seconds. The cooling medium can be a low-temperature medium such as liquid nitrogen or cold helium. As shown in Table 1, before quenching, the flow rate of the low-temperature cooling medium is set according to the thickness of the sheet metal frame (thickness and flow rate are positively correlated) to ensure that the part can be thoroughly quenched. In addition, the material temperature before quenching is monitored by a temperature monitoring system to ensure that the material solution temperature meets the process requirements and ensures the material strength.

[0057] Step 4: Monitor the temperature of the sheet metal frame after quenching using the temperature monitoring system of the stretching die. Once the temperature of the quenched sheet metal frame drops below -110℃, use a robotic arm to remove the quenched sheet metal.

[0058] Step 5: For sheet metal requiring artificial aging, the quenched parts need to be placed in an aging furnace for artificial aging treatment.

[0059] Step Six: After aging treatment, the parts are laser-cut to remove the process allowance, and the surface is scanned and mechanical properties are tested to finally complete the manufacturing of the sheet frame.

[0060] Furthermore, schematic diagrams of the stretching equipment in steps two and three are shown below. Figure 2 As shown; it consists of a control system 200, a stretching die 201, and a cryogenic medium storage and circulation system 203, etc.; wherein, as Figure 3 As shown, the stretching die consists of a punch 2011 and a die 2012, and integrates a low-temperature cooling system 202 and a temperature detection system 204. The cooling medium channel of the low-temperature cooling system 202 is 10~30mm away from the surface of the punch and die. The cooling medium channel is set according to the shape and changes with the shape of the sheet frame 100. The low-temperature cooling system can control the cooling rate by controlling the pressure of the cooling medium. Both the punch and die are integrated with the low-temperature cooling system, which can significantly improve the cooling rate and ensure and improve the material strength. In addition, the die 2012 integrates a temperature monitoring system 204, which can monitor the temperature of the die and the sheet frame 100 in real time, ensuring that the temperature of the sheet frame 100 before quenching is above the solution temperature, and at the same time ensuring that the temperature of the sheet after quenching can be as low as -110℃.

[0061] The specific implementation methods of the embodiments of the present invention will now be described in detail. This detailed description is not a limitation of the present invention, but a specific description of certain aspects, characteristics and implementation methods of the present invention.

[0062] Example 1: Using 4mm thick 2A12-O temper aluminum alloy sheet as the blank, the deviation between the target sheet frame profile and the theoretical profile is (-0.5, +0.5) mm. Figure 4 As shown, the curvature radius of the plate frame is 1700mm~2100mm, and the arc length of the plate frame is 400mm~600mm; the mechanical properties of the plate frame need to meet the following requirements: tensile strength ≥425MPa, yield strength ≥275MPa, and elongation ≥15%.

[0063] Step 1: Cut the 2A12-O state aluminum alloy sheet into blanks, and then put the blanks into a heat treatment furnace and heat them to 504℃, and hold them at that temperature for 90 minutes.

[0064] Step 2: The heated sheet metal is quickly placed into the stretching die by a robotic arm. The stretching of the sheet metal is completed within 10 seconds. During the stretching process, the concave die remains stationary while the convex die moves downward. The stretching and forming of the sheet metal frame is completed when the workpiece is completely pressed into the die by the convex die.

[0065] Step 3: After stretching, keep the upper and lower molds in contact with the sheet frame. Monitor the temperature of the workpiece through the temperature monitoring system to ensure it is not lower than 497℃. Adjust the pipeline pressure to a cooling medium flow rate of 1.5m / s. The cooling medium is liquid nitrogen. Start quenching.

[0066] Step 4: Once the temperature of the quenched plate frame drops to -130℃, use a robotic arm to remove the quenched plate.

[0067] Step 5: After the workpiece returns to room temperature and is left to stand naturally for 96 hours, the natural aging process is complete. Step Six: After aging, the sheet metal frame undergoes laser edge cutting, surface scanning, and mechanical property testing; the deviation between the inner surface and the theoretical surface is 0.3mm, the tensile strength is 460 MPa, the yield strength is 315 MPa, and the elongation is 21%. Figure 5 As shown, Figure 5 Temperature change curves for each processing step are presented.

[0068] Example 2: Using 7mm thick 2A12-O state aluminum alloy sheet as blank, the deviation between the target sheet frame and the theoretical frame is (-0.5, +0.5)mm, the radius of curvature of the sheet frame is 1700mm~2100mm, and the arc length of the sheet frame is 400mm~600mm; the mechanical properties of the sheet frame meet the following requirements: tensile strength ≥445MPa, yield strength ≥275MPa, elongation ≥15%.

[0069] Step 1: Cut the 2A12-O state aluminum alloy sheet into blanks, and then put the blanks into a heat treatment furnace and heat them to 504℃, and hold them for 90 minutes.

[0070] Step 2: The heated sheet metal is quickly placed into the stretching die by a robotic arm. The stretching of the sheet metal is completed within 10 seconds. During the stretching process, the concave die remains stationary while the convex die moves downward. The stretching and forming of the sheet metal frame is completed when the workpiece is completely pressed into the die by the convex die.

[0071] Step 3: After stretching, keep the upper and lower molds in contact with the sheet frame. Monitor the temperature of the workpiece through the temperature monitoring system to ensure it is not lower than 497℃. Adjust the pipeline pressure to a cooling medium flow rate of 1.5m / s. The cooling medium is liquid nitrogen. Start quenching.

[0072] Step 4: Once the temperature of the quenched plate frame drops to -130℃, use a robotic arm to remove the quenched plate.

[0073] Step 5: After the workpiece returns to room temperature and is left to stand naturally for 96 hours, the natural aging process is complete. Step 6: After aging, the plate frame is laser-cut, and the surface is scanned and mechanical properties are tested; the deviation between the inner surface and the theoretical surface is 0.3mm, the tensile strength is 465 MPa, the yield strength is 314 MPa, and the elongation is 20.5%.

[0074] Example 3: Using 6mm thick 2A14-O state aluminum alloy sheet as blank, the deviation between the target sheet frame and the theoretical frame is (-0.5, +0.5) mm, the radius of curvature of the sheet frame is 1700mm~2100mm, and the arc length of the sheet frame is 400mm~600mm; the mechanical properties of the sheet frame need to meet the following requirements: tensile strength ≥445MPa, yield strength ≥380MPa, elongation ≥7%.

[0075] Step 1: Cut the 2A14-O state aluminum alloy sheet into blanks, and then put the blanks into a heat treatment furnace and heat them to 501℃ and hold for 60 minutes.

[0076] Step 2: The heated sheet metal is quickly placed into the stretching die by a robotic arm. The stretching of the sheet metal is completed within 10 seconds. During the stretching process, the concave die remains stationary while the convex die moves downward. The stretching and forming of the sheet metal frame is completed when the workpiece is completely pressed into the die by the convex die.

[0077] Step 3: After stretching, keep the upper and lower molds in contact with the sheet frame. Monitor the temperature of the workpiece through the temperature monitoring system to ensure it is not lower than 490℃. Adjust the pipeline pressure to a cooling medium flow rate of 1.5m / s. The cooling medium is liquid nitrogen. Start quenching.

[0078] Step 4: Once the temperature of the quenched plate frame drops to -130℃, use a robotic arm to remove the quenched plate.

[0079] Step 5: Place the workpiece in an aging furnace for manual aging. Step 6: After aging, the plate frame is laser-cut, and the surface is scanned and mechanical properties are tested; the deviation between the inner surface and the theoretical surface is 0.35mm, the tensile strength is 480 MPa, the yield strength is 420 MPa, and the elongation is 15%.

[0080] The embodiments of this invention have the following technical effects: By utilizing forming equipment, an integrated design of forming and quenching is achieved; compared with the traditional room-temperature stretching and quenching process, production efficiency and surface accuracy are significantly improved. The low-temperature quenching process employed can achieve a quenching speed greater than or equal to 80℃ / s, and can even quench through thick parts; the aluminum alloy after quenching generates residual compressive stress at low temperatures, and combined with the integrated hot forming and quenching process design, its surface accuracy and dimensional stability are significantly improved; in addition, the aluminum alloy after low-temperature quenching has a high supersaturation of solid solution, resulting in better dispersion precipitation after aging, and its strength is increased by more than 10% compared with the room-temperature quenching medium process. The forming equipment has online temperature monitoring and flow control functions, which can monitor the temperature before quenching to ensure the strength of the material after quenching; the equipment can also detect the temperature of the material after low-temperature quenching, utilizing the strengthening mechanism of aluminum alloy at low temperatures to ensure the precipitation of a large amount of dispersed second phase after quenching and aging, thereby improving the strength of the material.

[0081] It should be understood that the specific order or hierarchy of steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process may be rearranged without departing from the scope of this disclosure. The appended method claims provide elements of various steps in an exemplary order and are not intended to limit the scope to the specific order or hierarchy described.

[0082] In the above detailed description, various features are combined together in a single embodiment to simplify this disclosure. This approach to disclosure should not be construed as reflecting an intention that embodiments of the claimed subject matter require more features than are explicitly stated in each claim. Rather, as reflected in the appended claims, the invention is presented with fewer features than all of the features of the single disclosed embodiment. Therefore, the appended claims are hereby explicitly incorporated into the detailed description, wherein each claim stands alone as a preferred embodiment of the invention.

[0083] The disclosed embodiments have been described above to enable any person skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments without departing from the spirit and scope of this disclosure. Therefore, this disclosure is not limited to the embodiments given herein, but is consistent with the broadest scope of the principles and novel features disclosed in this application.

[0084] The foregoing description includes examples of one or more embodiments. It is certainly impossible to describe all possible combinations of components or methods in order to describe the above embodiments, but those skilled in the art will recognize that further combinations and arrangements of the various embodiments are possible. Therefore, the embodiments described herein are intended to cover all such changes, modifications, and variations falling within the scope of the appended claims. Furthermore, the term "comprising" as used in the specification or claims is used in a manner similar to the term "including." Additionally, the use of any term "or" in the specification of the claims is intended to mean "non-exclusive or."

[0085] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. 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 method for forming a sheet metal frame, characterized in that, Includes the following steps: A sheet material above the solution treatment temperature is placed in a stretching die and stretched to form a sheet frame; The plate frame is continued to be clamped in the stretching die. When the temperature of the plate frame is monitored to be not lower than the solution temperature, a cooling medium is injected into the stretching die to start quenching the plate frame. When the temperature of the plate frame drops to the quenching end temperature, the quenched plate frame is removed from the stretching die. The plate frame is subjected to aging treatment; The boiling point of the cooling medium is below -130°C.

2. The method for forming a sheet metal frame as described in claim 1, characterized in that, The step of injecting cooling medium into the stretching die includes: determining the flow rate of the cooling medium injected into the stretching die based on the thickness of the stretched plate frame, so that the plate frame cools down to the quenching end temperature at a preset cooling rate.

3. The method for forming a sheet metal frame as described in claim 1, characterized in that, The stretching die includes a punch and a die; The punch is provided with a first cooling medium flow channel, and the distance from the side wall of the first cooling medium flow channel near the working surface of the punch to the working surface of the punch is 10~30 mm. The die cavity is provided with a second cooling medium flow channel, and the distance from the side wall of the second cooling medium flow channel near the working surface of the die cavity to the working surface of the die cavity is 10~30 mm.

4. The plate frame forming method as described in claim 3, characterized in that, The overall shape of the first cooling medium channel and / or the second cooling medium channel matches the shape of the plate frame.

5. The method for forming a sheet metal frame as described in claim 1, characterized in that, The plate material is aluminum alloy; the thickness of the plate is less than or equal to 10 mm.

6. The method for forming a sheet metal frame as described in claim 2, characterized in that, The cooling medium includes liquid nitrogen or cold helium; the preset cooling rate is greater than or equal to 70°C / s.

7. The method for forming a sheet metal frame as described in claim 1, characterized in that, include: The sheet material is placed in a heat treatment furnace and heated to above the solution temperature, and held for 30 to 180 minutes. The sheet material is made of aluminum alloy and the thickness of the sheet material is less than or equal to 10 mm. The insulated sheet material is placed into the stretching mold, and the stretching of the sheet material is completed within 5 to 10 seconds to obtain the sheet material frame; The stretched plate frame continues to be held in the stretching die. When the temperature of the plate frame is not lower than the lower limit of the solid solution temperature, the flow rate of the cooling medium injected into the cooling medium channel of the stretching die is controlled to be 0.5~1.5m / s, and quenching begins. After the temperature of the quenched plate frame drops to -130℃~-110℃, the quenched plate frame is taken out. The plate frame is subjected to aging treatment.

8. A sheet metal frame forming system, characterized in that, The method described in any one of claims 1 to 7 includes: The system includes a control system (200), a temperature monitoring system (204) and a cryogenic medium storage and circulation system (203) connected to the control system (200), a stretching die (201) connected to the temperature monitoring system (204), and a cryogenic cooling system (202) disposed in the stretching die (201), wherein the cryogenic cooling system (202) is connected to the cryogenic medium storage and circulation system (203).

9. The sheet metal frame forming system as described in claim 8, characterized in that, The control system (200) is used to receive the temperature of the plate collected by the temperature monitoring system (204), and trigger the stretching die (201) to stretch the plate according to the temperature of the plate, and trigger the low temperature medium storage and circulation system (203) to quench the stretched plate frame. The stretching die (201) is used to stretch the plate when the temperature of the plate is higher than the solution temperature, triggered by the control system (200), and to continue to hold the plate frame during quenching to complete the quenching; the stretching die (201) is provided with a low temperature cooling system (202), which is used to inject a cooling medium during quenching. The low-temperature medium storage and circulation system (203) is used to inject cooling medium into the low-temperature cooling system (202) in the stretching die (201) by the control system (200) when the temperature of the stretched plate frame is not lower than the solution temperature, so as to complete the quenching of the plate frame clamped in the stretching die (201). The temperature monitoring system (204) is used to collect the temperature of the plate before stretching, the temperature of the plate frame after stretching and during quenching, and provide this data to the control system (200).

10. The sheet metal frame forming system as described in claim 9, characterized in that, The control system (200) determines the flow rate of the cooling medium injected into the stretching die (201) based on the thickness of the stretched plate frame, so that the plate frame is cooled to the quenching end temperature at a preset cooling rate.

11. A rocket mouth frame, characterized in that, A plate frame made by means of any one of claims 1 to 7.

12. A launch vehicle, characterized in that, This includes the rocket port frame as described in claim 11, which is installed in the rocket compartment.

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