Method and system for improving bulging performance of large-width aluminum alloy tailor-welded blank

Abstract

This invention provides a method and system for improving the bulging performance of wide aluminum alloy welded plates, comprising: Step S1: welding to prepare the welded plate; Step S2: placing the prepared welded plate on a hydraulic bulging device and applying a clamping force, driving the welded plate to undergo plastic deformation through a liquid booster to obtain a pre-bulged blank; Step S3: solution quenching the pre-bulged blank; Step S4: hydraulically bulging the welded plate in stages, performing three-dimensional scanning of the upper and lower surfaces of the welded plate during the hydraulic staged bulging process, and comparing it with the target surface; Step S5: using a local constraint shaping device to locally constrain and shape the bulged surface to obtain a welded box bottom that meets dimensional accuracy requirements. This invention uses vacuum electron beam welding to prepare the welded plate, with a welding coefficient exceeding 90%, and the microstructure shows no obvious growth tendency after solution quenching, improving the uniformity and high ductility of the welded plate during bulging.

Description

Technical Field

[0001] This invention relates to the field of metal forming technology for aerospace launch vehicles, and more specifically, to a method and system for improving the bulging performance of wide aluminum alloy welded plates. Background Technology

[0002] Large-size thin-walled components are an extremely important type of part in aerospace vehicles. Due to the limited size of the slab blank, the existing technology for such components generally adopts the technical solution of "preparing large-size blanks by welding plates + heat treatment to control performance + integral forming of large-size components".

[0003] A literature search of existing technologies revealed that in the automotive industry, laser welding has become the mainstream process for welding body panels (CN117897253A, CN101354731A, CN101961744B, CN108801814B). In the aerospace industry, where the main structural material is 2-series aluminum alloys, friction stir welding and electron beam welding have replaced laser welding as the preferred processes for high-performance welding of 2-series aluminum alloys.

[0004] Meanwhile, premature instability of the weld seam during deep drawing or spinning of large welded plates is a major factor affecting the forming performance of welded plates. Therefore, scholars at home and abroad have conducted research on improving the forming performance of welded plates. WO20191531104A1, CN108326159B, and CN117506110A fill the deep drawing die with coolant, which causes low-temperature strengthening in the weld zone, increases the elongation of the weld zone, and improves the forming limit. However, cooling the die and workpiece to -160℃ is costly. CN115074513A and CN107199289B heat the sheet material and then place the entire sheet material into the die for hot deep drawing. Because the heat loss is relatively fast when the sheet material is placed in the die, it is difficult to accurately control the forming temperature of this method. At the same time, dynamic recovery and recrystallization occur during the hot deep drawing process, resulting in abnormal grain growth and decreased microstructure properties. CN108161353A, CN104607524A, and CN113607632B employ room temperature liquid-filled deep drawing to improve the overall deformation capacity of welded plates, with the main mechanism being stress distribution control. However, the weld seam remains a weak deformation zone, prone to fracture and instability. CN108161353A, CN107460416A, and CN108655668A utilize friction stir welding technology to improve the overall deformation capacity of welded plates, but the friction stir weld seam undergoes abnormal growth during solution quenching, affecting the component's service performance. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method and system for improving the bulging performance of wide aluminum alloy welded plates.

[0006] The method for improving the bulging performance of wide aluminum alloy welded plates according to the present invention includes:

[0007] Step S1: Welding to prepare the welded plate;

[0008] Step S2: Place the prepared welded plate on the welded plate hydraulic bulging device and apply a clamping force. Drive the welded plate to undergo plastic deformation through the liquid booster to obtain the welded plate pre-bulging blank.

[0009] Step S3: Solution harden and quench the pre-expanded blank of the welded plate;

[0010] Step S4: Perform hydraulic step-by-step bulging on the welded plate. During the hydraulic step-by-step bulging process, perform three-dimensional scanning on the upper and lower surfaces of the welded plate and compare them with the target surface.

[0011] Step S5: Use the local constraint shaping device for the welded plate to locally constrain and shape the bulging surface to obtain a welded box bottom that meets the dimensional accuracy requirements;

[0012] The hydraulic bulging device includes a pressure ring, a pressure inlet, a sealing plate, and a hydraulic source; the pressure inlet is connected to the sealing plate, and the hydraulic source applies a high-pressure liquid medium to the sheet material through the pressure inlet, fixing the sheet material between the pressure ring and the sealing plate; the pressure ring is used to apply a clamping force, so that the liquid medium is sealed between the sheet material and the sealing plate;

[0013] The local constraint shaping device, based on the hydraulic expansion device, also includes a mold for constraining top deformation; under the action of hydraulic expansion force, the welded plate contacts the inner surface of the mold, making contact from the top center and gradually fully fitting the surface.

[0014] Preferably, step S1 includes: the welded plate is composed of 3 strips, which are welded in pairs using vacuum electron beam welding, with the weld positions symmetrically distributed and no beveling; wherein the electron beam power is 1500W-4000W, the feed speed is 100mm / min-300mm / min, samples are taken from the base material and the welding allowance area respectively, the samples are clamped on a tensile testing machine, the tensile rate is set to 5mm / min, and the yield strength, fracture strength and elongation of the material are measured, wherein the average value of the fracture strength of the sample with weld is not less than 0.9 of the fracture strength of the base material.

[0015] Preferably, step S2 includes: placing the welded plate between the pressure ring and the sealing plate, connecting the liquid booster to the pressure port, applying the clamping force, filling the space between the double-layer welded plates with high-pressure liquid to form a sealed cavity, stopping the expansion when the pre-expansion height of the welded plate reaches 1 / 2 of the total height, and reading the hydraulic gauge value as 1.5 MPa at this time.

[0016] Preferably, step S3 includes: performing quenching heat treatment on the pre-expanded blank of the welded plate, with a holding temperature of 530℃-535℃, a holding time of 40min-50min, and a quenching transfer time of less than 12s.

[0017] Preferably, step S4 includes: placing the welded plate between the pressure ring and the sealing plate, connecting the liquid booster to the pressure inlet, applying a clamping force, and performing pressure bulging in three steps. In the first step, the quenched welded plate is placed between the pressure ring and the sealing plate, and the pressure is increased to 2.5 MPa, then the pressure is released to zero. In the second step, the pressure is increased to 3.5 MPa, then the pressure is released to zero. In the third step, the target pressure is 4.5 MPa, the pressure is gradually increased and the bulging height is measured. When the preset bulging height is reached, the pressure is stopped and the corresponding bulging pressure is recorded. After each bulging step, the actual surface is three-dimensionally scanned and recorded, and compared with the target surface. If the preset bulging height is reached, the pressure bulging is stopped; otherwise, the pressure is increased until the bulging height is reached.

[0018] The system for improving the bulging performance of wide aluminum alloy welded plates according to the present invention includes:

[0019] Module M1: Welding preparation of welded plates;

[0020] Module M2: The prepared welded plate is placed on the hydraulic bulging device for welded plate and a clamping force is applied. The welded plate is driven to undergo plastic deformation by a liquid booster to obtain a pre-bulged blank of the welded plate.

[0021] Module M3: Solution hardening and quenching of the pre-expanded blank of the welded plate;

[0022] Module M4: Performs hydraulic step-by-step bulging on the welded plate. During the hydraulic step-by-step bulging process, it performs three-dimensional scanning of the upper and lower surfaces of the welded plate and compares them with the target surface.

[0023] Module M5: Uses a local constraint shaping device for welded plates to locally constrain and shape the bulging surface to obtain a welded box bottom that meets dimensional accuracy requirements;

[0024] The hydraulic bulging device includes a pressure ring, a pressure inlet, a sealing plate, and a hydraulic source; the pressure inlet is connected to the sealing plate, and the hydraulic source applies a high-pressure liquid medium to the sheet material through the pressure inlet, fixing the sheet material between the pressure ring and the sealing plate; the pressure ring is used to apply a clamping force, so that the liquid medium is sealed between the sheet material and the sealing plate;

[0025] The local constraint shaping device, based on the hydraulic expansion device, also includes a mold for constraining top deformation; under the action of hydraulic expansion force, the welded plate contacts the inner surface of the mold, making contact from the top center and gradually fully fitting the surface.

[0026] Preferably, the module M1 includes: a welding plate composed of 3 strips, which are welded in pairs using vacuum electron beam welding, with the weld positions symmetrically distributed and without beveling; wherein the electron beam power is 1500W-4000W, the feed speed is 100mm / min-300mm / min, samples are taken from the base material and the welding allowance area respectively, the samples are clamped on a tensile testing machine, the tensile rate is set to 5mm / min, and the yield strength, fracture strength and elongation of the material are measured, wherein the average value of the fracture strength of the sample with weld is not less than 0.9 of the fracture strength of the base material.

[0027] Preferably, the module M2 includes: placing the welded plate between the pressure ring and the sealing plate, connecting the liquid booster to the pressure port, applying the clamping force, filling the space between the double-layer welded plates with high-pressure liquid to form a sealed cavity, stopping the expansion when the pre-expansion height of the welded plate reaches 1 / 2 of the total height, and reading the hydraulic gauge value as 1.5MPa at this time.

[0028] Preferably, module M3 includes: quenching heat treatment of the pre-expanded blank of the welded plate, with a holding temperature of 530℃-535℃, a holding time of 40min-50min, and a quenching transfer time of less than 12s.

[0029] Preferably, module M4 includes: placing the welded plate between the pressure ring and the sealing plate, connecting a liquid pressure booster to the pressure inlet, applying a clamping force, and performing pressure bulging in three steps: the first step is to place the quenched welded plate between the pressure ring and the sealing plate, start pressurizing to 2.5 MPa, and then unload the pressure to zero; the second step is to pressurize to 3.5 MPa, and then unload the pressure to zero; the third step is to target a pressure of 4.5 MPa, gradually increase the pressure and measure the bulging height, stop pressurizing when the preset bulging height is reached, and record the corresponding bulging pressure; after each step of bulging is completed, perform a three-dimensional scan of the actual surface and compare it with the target surface. If the preset bulging height is reached, stop pressurizing and bulging; otherwise, continue pressurizing until the bulging height is reached.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The present invention uses vacuum electron beam welding to prepare welded plates with a welding coefficient of over 90%, and the structure does not show obvious growth tendency after solution quenching, thus improving the uniformity of expansion and high ductility of the welded plates.

[0032] (2) The local constraint shaping device of the present invention plays a dual role in regulating the stress state and the bulging surface, reducing the risk of premature instability and cracking at the top of the bulging, and can achieve a bulging surface accuracy of not less than 2mm;

[0033] (3) The present invention can achieve near-net-shape forming. The formed tank bottom does not need to be machined and can be directly used for tank structure assembly, saving a lot of raw materials and processing costs. Attached Figure Description

[0034] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0035] Figure 1 This is a flowchart of the present invention;

[0036] Figure 2 Schematic diagram of a hydraulic bulging device for welded plates;

[0037] Figure 3 This is a schematic diagram of a hydraulic bulging local constraint device for welded plates. Detailed Implementation

[0038] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0039] Example 1

[0040] In this embodiment, the raw material is 2219 aluminum alloy with a plate thickness of 8mm. The initial heat treatment state of the plate is M state (soft state).

[0041] like Figure 1 As shown, this embodiment includes the following steps:

[0042] Step S1: Determine the structure and manufacturing process of the welded plate according to the bottom design drawing;

[0043] In this embodiment, the welded plate consists of three strips, each 8mm thick, 4200mm long, and 450mm, 3300mm, and 450mm wide respectively. The 3300mm wide strip is in the center, and the two 450mm wide strips are on either side, butt-welded in pairs. The weld seams are symmetrically distributed, and the welding process uses vacuum electron beam welding without beveling.

[0044] Step S2: Design and manufacture the hydraulic bulging device and constraint shaping device for the welded plate;

[0045] like Figure 2 and Figure 3As shown, the hydraulic bulging device consists of a pressure ring 1, a pressure inlet 2, a sealing plate 3, and a hydraulic source 4. The pressure inlet 2 is connected to the sealing plate 3. The hydraulic source 4 applies high-pressure liquid medium to the sheet metal through the pressure inlet 2, and the sheet metal is fixed between the pressure ring 1 and the sealing plate 3. The pressure ring 1 is used to apply a clamping force, so that the liquid medium is sealed between the sheet metal and the sealing plate 3. The local constraint shaping device, based on the hydraulic bulging device, also includes a mold 7 for constraining top deformation. Figure 3 Component 5 is a part formed using a local constraint shaping device. Component 6 is a free-bulging curved surface without a local constraint shaping device; under the action of hydraulic bulging force, component 5 comes into contact with the inner surface of mold 7, starting from the top center and gradually becoming completely fitted to the surface. Component 6, however, is free-bulging without constraint shaping, resulting in a final surface that differs significantly from the design drawing.

[0046] Step S3: Electron beam welding to prepare high-performance welded plates;

[0047] In this embodiment, a vacuum electron beam welding method is used to prepare the welded plate. The steps are as follows: assemble three plates according to the welded plate structure determined in S1 → fix the plates by electric welding → zero and position the electron beam welding gun → evacuate the equipment → set the equipment parameters (recommended electron beam power is 1500W-4000W, feed speed is 100mm / min-300mm / min) → start the equipment to begin the first weld → end the first weld → jump to the second weld to begin the second weld → end the second weld → turn off the vacuum to form a path. A sample is taken from the weld allowance area for a tensile test, and the weld coefficient is tested to be no less than 0.9. According to the national standard GB / T228.1, samples are taken and tested in the base material and the weld allowance area respectively. The tensile specimens are clamped on a tensile testing machine, the tensile rate is set to 5mm / min, and the yield strength, breaking strength, and elongation of the material are measured. The average value of the breaking strength of the welded specimen should be no less than 0.9 of the breaking strength of the base material. The purpose of testing the weld coefficient is to ensure that the weld does not fail prematurely during the subsequent bulging process.

[0048] Step S4: Pre-expansion forming of the welded plate. The plate is placed on the hydraulic expansion forming device for the welded plate. The welded plate is placed between the pressure ring 1 and the sealing plate 3. The liquid booster is connected to the pressure port 2 and the clamping force is applied. The liquid booster fills the space between the two layers of welded plates with high-pressure liquid to form a sealed cavity. In this embodiment, when the pre-expansion height of the plate reaches 1 / 2 of the total height, the expansion is stopped. At this time, the hydraulic gauge reading is 1.5MPa.

[0049] The clamping ring provides clamping force, and the intensifier pressurizes the liquid between the two-layer welded plates to form a sealed cavity, causing the two-layer plates to deform.

[0050] Step S5: Solution quenching of the welded plates;

[0051] The pre-expanded blank of the welded plate obtained in step S4 is subjected to quenching heat treatment. According to the recommended range of the general specification for quenching heat treatment of aerospace aluminum alloys, and after optimization by test piece-level performance testing, the holding temperature is 530-535℃, the holding time is 40-50min, and the quenching transfer time is less than 12s.

[0052] Step S6: Hydraulic step-by-step bulging of the welded plate. Place the welded plate between the pressure ring 1 and the sealing plate 3, connect the liquid pressure booster to the pressure inlet 2, and apply the clamping force. In this embodiment, a step-by-step bulging + final shaping forming strategy is formulated. According to the three-step pressure bulging, the target pressure for each step is set to 2.5MPa, 3.5MPa, and 4.5MPa. 1) In the first step, place the quenched welded plate between the pressure ring 1 and the sealing plate 3, start pressurizing to 2.5MPa and stop, unload the pressure to zero, and obtain the surface point cloud data in three dimensions; 2) In the second step, pressurize to 3.5MPa, unload after reaching the target pressure, and obtain the surface point cloud data in three dimensions, and compare it with the target surface; 3) In the third step, the target pressure is 4.5MPa. Gradually increase the pressure and measure the bulging height. When the bulging height value is reached, stop pressurizing and record the bulging pressure value. After each bulging step is completed, the material is unloaded, and the actual surface is scanned and recorded in three dimensions. The actual surface is then compared with the target surface. If the bulging height is reached, the pressure bulging stops; otherwise, the pressure continues to increase until the bulging height is reached.

[0053] The specific implementation method of comparing the 3D scanning technology with the target surface is as follows: 1. Data acquisition: In this embodiment, a 3D scanning LiDAR is used to scan the surface after each step of pressure bulging to obtain point cloud data of its surface. This point cloud data contains a large number of 3D coordinate points of the actual box bottom surface; 2. Data processing: The acquired point cloud data is imported into point cloud processing software for filtering, noise reduction, registration, fusion, and other processing to generate a complete and accurate 3D model; 3. Comparative analysis: In the 3D processing software, the generated 3D point cloud model is compared and analyzed with the target surface to evaluate the manufacturing accuracy, form and position errors, etc. of the target object.

[0054] Step S7: Hydraulic final forming of the welded plate. Using the local constraint shaping device, the bulging surface is defined, and the bulging surface is locally constrained and shaped to obtain a welded box bottom that meets the dimensional accuracy requirements. There are two specific control parameters for applying the constraint: first, the final shaping pressure. Under hydraulic pressure, the center of the plate is pressed against the local constraint shaping device. By applying the shaping pressure, excessive gaps between the plate and the constraint shaping device are eliminated, resulting in a final surface that meets the accuracy requirements; second, the bulging height. The constraint can be applied vertically to control the bulging height of the unconstrained parts. The unique advantage of these parameters is that under the action of hydraulic bulging force and the constraint shaping device, the plate no longer undergoes free bulging. Instead, the top center first contacts the constraint shaping device and gradually and completely conforms to the surface. Through local constraint shaping, the purpose of precisely controlling the bulging surface is achieved.

[0055] In this embodiment, the actual formed part surface was three-dimensionally scanned, as shown in Table 1. Compared with the target surface, the final surface accuracy deviation using the local constraint forming device did not exceed 2mm. Under the same pressure, the surface deviation of the unconstrained free bulging form reached 25.1mm.

[0056] Table 1. Surface accuracy during the box bottom forming process (maximum deviation between actual and target surface in mm)

[0057]

[0058] Example 2

[0059] The present invention also provides a system for improving the bulging performance of wide aluminum alloy welded plates. The system for improving the bulging performance of wide aluminum alloy welded plates can be implemented by executing the process steps of the method for improving the bulging performance of wide aluminum alloy welded plates. That is, those skilled in the art can understand the method for improving the bulging performance of wide aluminum alloy welded plates as a preferred embodiment of the system for improving the bulging performance of wide aluminum alloy welded plates.

[0060] The system for improving the bulging performance of wide aluminum alloy welded plates according to the present invention includes: module M1: welding to prepare the welded plate; module M2: placing the prepared welded plate on a hydraulic bulging device and applying a clamping force, driving the welded plate to undergo plastic deformation through a liquid booster to obtain a pre-bulged blank of the welded plate; module M3: solution quenching the pre-bulged blank of the welded plate; module M4: hydraulically bulging the welded plate in stages, and performing three-dimensional scanning of the upper and lower surfaces of the welded plate during the hydraulically bulging process, comparing them with the target surface; module M5: using a local constraint shaping device for the welded plate to locally constrain and shape the bulged surface to obtain a welded box bottom that meets the dimensional accuracy requirements;

[0061] The hydraulic bulging device includes a pressure ring, a pressure inlet, a sealing plate, and a hydraulic source; the pressure inlet is connected to the sealing plate, and the hydraulic source applies a high-pressure liquid medium to the sheet material through the pressure inlet, fixing the sheet material between the pressure ring and the sealing plate; the pressure ring is used to apply a clamping force, so that the liquid medium is sealed between the sheet material and the sealing plate;

[0062] The local constraint shaping device, based on the hydraulic expansion device, also includes a mold for constraining top deformation; under the action of hydraulic expansion force, the welded plate contacts the inner surface of the mold, making contact from the top center and gradually fully fitting the surface.

[0063] The module M1 includes: a welding plate composed of 3 strips, which are welded in pairs using vacuum electron beam welding, with the weld seams symmetrically distributed and without beveling; wherein the electron beam power is 1500W-4000W, the feed speed is 100mm / min-300mm / min, samples are taken from the base material and the welding allowance area, the samples are clamped on a tensile testing machine, the tensile rate is set to 5mm / min, and the yield strength, fracture strength and elongation of the material are measured, wherein the average value of the fracture strength of the sample with weld seam is not less than 0.9 of the fracture strength of the base material.

[0064] The module M2 includes: placing the welded plate between the pressure ring and the sealing plate, connecting the liquid booster to the pressure port, applying the clamping force, filling the space between the double-layer welded plates with high-pressure liquid to form a sealed cavity, stopping the expansion when the pre-expansion height of the welded plate reaches 1 / 2 of the total height, and reading the hydraulic gauge value as 1.5MPa at this time.

[0065] The module M3 includes: performing quenching heat treatment on the pre-expanded blank of the welded plate, with a holding temperature of 530℃-535℃, a holding time of 40min-50min, and a quenching transfer time of less than 12s.

[0066] The module M4 includes: placing the welded plate between the pressure ring and the sealing plate, connecting the liquid booster to the pressure inlet, applying clamping force, and performing pressure bulging in three steps. The first step involves placing the quenched welded plate between the pressure ring and the sealing plate, increasing the pressure to 2.5 MPa, stopping, unloading the pressure to zero, and obtaining 3D scanning point cloud data of the molded surface. The second step involves increasing the pressure to 3.5 MPa, unloading after reaching the target pressure, and obtaining 3D scanning point cloud data of the molded surface, which is then compared with the target molded surface. The third step involves a target pressure of 4.5 MPa, gradually increasing the pressure and measuring the bulging height. When the bulging height is reached, the pressure increase is stopped, and the bulging pressure value is recorded. After each bulging step, the pressure is unloaded, and the actual molded surface is 3D scanned and recorded, compared with the target molded surface. If the bulging height is reached, the pressure bulging stops; otherwise, the pressure continues to increase until the bulging height is reached.

[0067] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0068] Those skilled in the art will understand that, in addition to implementing the system, apparatus, and their modules provided by this invention in purely computer-readable program code, the same program can be implemented in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system, apparatus, and their modules provided by this invention can be considered a hardware component, and the modules included therein for implementing various programs can also be considered structures within the hardware component; alternatively, modules for implementing various functions can be considered both software programs implementing the method and structures within the hardware component.

[0069] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A method for improving the formability of a large wide aluminum alloy tailor welded blank, the method comprising: include: Step S1: Welding to prepare the welded plate; Step S2: Place the prepared welded plate on the welded plate hydraulic bulging device and apply a clamping force. Drive the welded plate to undergo plastic deformation through the liquid booster to obtain the welded plate pre-bulging blank. Step S3: Solution harden and quench the pre-expanded blank of the welded plate; Step S4: Perform hydraulic step-by-step bulging on the welded plate. During the hydraulic step-by-step bulging process, perform three-dimensional scanning on the upper and lower surfaces of the welded plate and compare them with the target surface. Step S4 includes: placing the welded plate between the pressure ring and the sealing plate, connecting the liquid booster to the pressure inlet, applying clamping force, and performing pressure bulging in three steps. The first step involves placing the quenched welded plate between the pressure ring and the sealing plate, initially pressurizing to 2.5 MPa, and then releasing the pressure to zero. The second step involves pressurizing to 3.5 MPa, and then releasing the pressure to zero. The third step targets a pressure of 4.5 MPa, gradually increasing the pressure and measuring the bulging height. Pressurization is stopped when the preset bulging height is reached, and the corresponding bulging pressure is recorded. After each bulging step, a three-dimensional scan of the actual surface is performed and compared with the target surface. If the preset bulging height is reached, pressure bulging is stopped; otherwise, pressure is continued until the preset bulging height is reached. Step S5: Use the local constraint shaping device for the welded plate to locally constrain and shape the bulging surface to obtain a welded box bottom that meets the dimensional accuracy requirements; Step S1 includes: the welded plate is composed of 3 strips, which are welded in pairs using vacuum electron beam welding, with the weld positions symmetrically distributed and no beveling; wherein the electron beam power is 1500W-4000W, the feed speed is 100mm / min-300mm / min, samples are taken from the base material and the welding allowance area respectively, the samples are clamped on a tensile testing machine, the tensile rate is set to 5mm / min, and the yield strength, fracture strength and elongation of the material are measured, wherein the average fracture strength of the sample with weld is not less than 0.9 times the fracture strength of the base material; Step S2 includes: placing the welded plate between the pressure ring and the sealing plate, connecting the liquid booster to the pressure port, applying the clamping force, filling the gap between the double-layer welded plates with high-pressure liquid to form a sealed cavity, stopping the expansion when the pre-expansion height of the welded plate reaches 1 / 2 of the total height, and reading the hydraulic gauge value as 1.5MPa at this time. The hydraulic bulging device includes a pressure ring, a pressure inlet, a sealing plate, and a hydraulic source; the pressure inlet is connected to the sealing plate, and the hydraulic source applies a high-pressure liquid medium to the sheet material through the pressure inlet, fixing the sheet material between the pressure ring and the sealing plate; the pressure ring is used to apply a clamping force, so that the liquid medium is sealed between the sheet material and the sealing plate; The local constraint shaping device, based on the hydraulic expansion device, also includes a mold for constraining top deformation; under the action of hydraulic expansion force, the welded plate contacts the inner surface of the mold, making contact from the top center and gradually fully fitting the surface.

2. The method for improving the bulging performance of wide aluminum alloy welded plates according to claim 1, characterized in that, Step S3 includes: quenching heat treatment of the pre-expanded blank of the welded plate, with a holding temperature of 530℃-535℃, a holding time of 40min-50min, and a quenching transfer time of less than 12s.

3. A system for improving the bulging performance of wide aluminum alloy welded plates, characterized in that, include: Module M1: Welding preparation of welded plates; Module M2: The prepared welded plate is placed on the hydraulic bulging device for welded plate and a clamping force is applied. The welded plate is driven to undergo plastic deformation by a liquid booster to obtain a pre-bulged blank of the welded plate. Module M3: Solution hardening and quenching of the pre-expanded blank of the welded plate; Module M4: Performs hydraulic step-by-step bulging on the welded plate. During the hydraulic step-by-step bulging process, it performs three-dimensional scanning of the upper and lower surfaces of the welded plate and compares them with the target surface. The module M4 includes: placing the welded plate between the pressure ring and the sealing plate; connecting the liquid pressure booster to the pressure inlet; applying clamping force; and performing pressure bulging in three steps. The first step involves placing the quenched welded plate between the pressure ring and the sealing plate, initially pressurizing to 2.5 MPa, and then releasing the pressure to zero. The second step involves pressurizing to 3.5 MPa, and then releasing the pressure to zero. The third step targets a pressure of 4.5 MPa, gradually increasing the pressure and measuring the bulging height. Pressurization stops when the preset bulging height is reached, and the corresponding bulging pressure is recorded. After each bulging step, a three-dimensional scan of the actual surface is performed and compared with the target surface. If the preset bulging height is reached, pressure bulging stops; otherwise, pressure continues to increase until the preset bulging height is reached. Module M5: Uses a local constraint shaping device for welded plates to locally constrain and shape the bulging surface to obtain a welded box bottom that meets dimensional accuracy requirements; The module M1 includes: a welding plate composed of 3 strips, which are welded in pairs using vacuum electron beam welding, with the weld seams symmetrically distributed and without beveling; wherein, the electron beam power is 1500W-4000W, the feed speed is 100mm / min-300mm / min, samples are taken from the base material and the welding allowance area, the samples are clamped on a tensile testing machine, the tensile rate is set to 5mm / min, and the yield strength, fracture strength and elongation of the material are measured, wherein the average fracture strength of the welded sample is not less than 0.9 times the fracture strength of the base material; The module M2 includes: placing the welded plate between the pressure ring and the sealing plate, connecting the liquid booster to the pressure port, applying the clamping force, filling the gap between the double-layer welded plates with high-pressure liquid to form a sealed cavity, stopping the expansion when the pre-expansion height of the welded plate reaches 1 / 2 of the total height, and reading the hydraulic gauge value as 1.5MPa at this time; The hydraulic bulging device includes a pressure ring, a pressure inlet, a sealing plate, and a hydraulic source; the pressure inlet is connected to the sealing plate, and the hydraulic source applies a high-pressure liquid medium to the sheet material through the pressure inlet, fixing the sheet material between the pressure ring and the sealing plate; the pressure ring is used to apply a clamping force, so that the liquid medium is sealed between the sheet material and the sealing plate; The local constraint shaping device, based on the hydraulic expansion device, also includes a mold for constraining top deformation; under the action of hydraulic expansion force, the welded plate contacts the inner surface of the mold, making contact from the top center and gradually fully fitting the surface.

4. The system for improving the bulging performance of wide aluminum alloy welded plates according to claim 3, characterized in that, The module M3 includes: performing quenching heat treatment on the pre-expanded blank of the welded plate, with a holding temperature of 530℃-535℃, a holding time of 40min-50min, and a quenching transfer time of less than 12s.

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