A hot and cold combined forming method for eccentric negative curvature thin-walled parts

Abstract

The present invention discloses a hot and cold combined forming method of an eccentric negative curvature thin-walled part, comprising the steps of drawing treatment: pre-drawing a blank through a pre-forming drawing die to obtain a pre-drawn part with a concave cavity feature; the maximum deformation of the concave cavity feature of the pre-drawn part does not exceed the maximum deformation of the concave cavity feature of the formed part; and the pre-forming drawing die includes a first elastic support supported on the lower side of the blank; eccentric treatment: eccentrically drawing the pre-drawn part through an eccentric drawing die to obtain an eccentric part with an eccentric feature, the maximum deformation of the eccentric feature of the eccentric part does not exceed the maximum deformation of the eccentric feature of the formed part; and the eccentric drawing die includes a second elastic support supported on the lower side of the eccentric part; bulging treatment: heating, bulging and holding the eccentric part through a bulging die to obtain a formed part with a negative curvature feature. The hot and cold combined forming method of an eccentric negative curvature thin-walled part provided by the present invention can meet the forming requirements of eccentric negative curvature thin-walled parts.

Description

Technical Field

[0001] The invention relates to the technical field of metal component forming, in particular to a cold-hot combined forming method for an eccentric negative curvature thin-walled part. Background Art

[0002] In recent years, as the performance requirements of components in high-end equipment fields such as aerospace, new energy vehicles, etc. have gradually increased, the use requirements and complexity of sheet metal parts have also been continuously increasing; key components of aerospace and other equipment use eccentric negative curvature surface shape components, such as exhaust tail cones, air intakes, etc., and commonly used materials include heat-resistant stainless steel, high-strength steel and high-temperature alloys.

[0003] The currently available methods for forming eccentric negative curvature parts include sheet metal stamping and welding, liquid filling deep drawing and superplastic forming. Among them, sheet metal stamping and welding is to form the complex curved surface of the eccentric negative curvature part in blocks, and then weld the stamped curved surface into a whole to form a complete eccentric negative curvature part. The defects of this method are that the parts obtained by the welding process have internal stress release, large resilience, low dimensional accuracy, and uneven deformation of the weld and heat-affected zone. The welding is difficult and the microstructure at the weld is complex, which makes it difficult to meet the high-quality requirements of this type of components. The eccentric asymmetric structure of the eccentric negative curvature thin-walled part further increases its requirements for spatial structure accuracy, and welding leads to scrap. The rate is increased, which seriously affects the production efficiency and production quality; when using the liquid filling deep drawing method, in the complex features of the formed parts, such as in the negative angle area, the effective lubrication cannot be established between the part and the mold, affecting the material flow, which will cause the blank to be unable to effectively supplement the negative angle area of ​​the mold, causing the material deformation to exceed the forming limit and break, making it difficult to form complex thin-walled parts; the difficulty of superplastic forming is that it is difficult to prepare a blank with uniform fine-grained structure that meets superplasticity. At the same time, due to the complex shape and structure of the slab during the forming process, local mold adhesion and friction occur, resulting in uneven wall thickness of the formed part; therefore, the existing forming methods cannot meet the requirements of uniform wall thickness, high forming accuracy and high reliability for forming eccentric negative curvature thin-walled parts. Summary of the invention

[0004] The purpose of the present invention is to provide a cold and hot combined forming method for eccentric negative curvature thin-walled parts to solve the problems existing in the above-mentioned prior art and meet the forming requirements of eccentric negative curvature thin-walled parts. + .

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] The present invention provides a hot and cold combined forming method for an eccentric negative curvature thin-walled part, comprising the following steps: drawing treatment: pre-drawing a blank through a pre-forming drawing die to obtain a pre-drawn part with a concave cavity feature; the maximum deformation of the concave cavity feature of the pre-drawn part does not exceed the maximum deformation of the concave cavity feature of the formed part; and the pre-forming drawing die includes a first elastic support for supporting the lower side of the blank; eccentric treatment: eccentrically drawing the pre-drawn part through an eccentric drawing die to obtain an eccentric part with an eccentric feature, the maximum deformation of the eccentric feature of the eccentric part does not exceed the maximum deformation of the eccentric feature of the formed part; and the eccentric drawing die includes a second elastic support for supporting the lower side of the eccentric part; bulging treatment: heating, bulging and maintaining pressure on the eccentric part through a bulging die to obtain the formed part with a negative curvature feature.

[0007] Preferably, the pre-forming drawing die includes a first pressurizing mechanism, a first lower support platform, a first upper support platform, a first upper die, a first edge clamping assembly and the first elastic support, the first edge clamping assembly and the first elastic support are fixedly arranged on the first lower support platform, and the first upper die is provided with a pre-forming cavity; the lower end of the first pressurizing mechanism is connected to the first upper support platform, the first upper die is arranged above the first elastic support and is fixedly connected to the first pressurizing mechanism through the first upper support platform, the first edge clamping assembly is arranged between the first upper die and the first elastic support and is used to press the edge of the blank; the pre-forming cavity has a concave cavity feature, the first pressurizing mechanism is used to drive the first upper die to move vertically, and to move the blank vertically under the support of the first edge clamping assembly, so that the first elastic support can punch the blank to form the pre-drawn part with a concave cavity feature.

[0008] Preferably, the eccentric drawing die includes a second pressurizing mechanism, a second lower support platform, a second upper support platform, a second upper die, a second edge clamping assembly and a second elastic support, the second edge clamping assembly and the second elastic support are fixedly arranged on the second lower support platform, and an eccentric cavity is arranged on the second upper die; the lower end of the second pressurizing mechanism is connected to the second upper support platform, the second upper die is arranged above the second elastic support and is fixedly connected to the second pressurizing mechanism through the second upper support platform, the second edge clamping assembly is arranged between the second upper die and the second elastic support and is used to press the edge of the pre-drawn part; the eccentric cavity has an eccentric feature, the second pressurizing mechanism is used to drive the second upper die to move vertically, and make the pre-drawn part move vertically under the support of the second edge clamping assembly, so that the second elastic support can stamp the pre-drawn part to form the eccentric part with an eccentric feature.

[0009] Preferably, the first edge holding assembly and the second edge holding assembly both include edge holding rings and multiple nitrogen springs, and the nitrogen springs are circumferentially supported on the edge holding ring and the first lower support platform or the second lower support platform; the edge holding ring is used to support the circumferential edge of the lower side of the blank or the pre-drawn part.

[0010] Preferably, the bulging mold includes a third pressurizing mechanism, a third upper support platform, a third lower support platform, a third upper mold and a third lower mold; the third upper mold is connected to the third upper support platform, and the lower end of the third pressurizing mechanism is connected to the third upper support platform; the third lower mold is provided with a bulging cavity with a negative curvature characteristic, and the third upper mold and the third lower mold are used to seal and press the eccentric piece, and the third upper mold is provided with a pressurizing channel connected to the outside, and the third lower mold is provided with an exhaust channel connected to the bulging cavity; and the third upper mold and the third lower mold are provided with heating mechanisms; the three pressurizing mechanisms are used to drive the third upper mold to move vertically.

[0011] Preferably, outer walls of the third upper mold and the third lower mold are provided with heat-insulating components.

[0012] Preferably, a cooling component is also provided on the third lower mold.

[0013] Preferably, in the step of bulging treatment, the third upper mold and the third lower mold are first heated and kept warm by the heating mechanism, and then the eccentric piece is sealed and pressed between the third upper mold and the third lower mold, and then pressurized fluid is injected through the pressurized channel to bulge the eccentric piece to fit the inner wall of the bulging cavity and maintain pressure.

[0014] Compared with the prior art, the present invention has achieved the following technical effects:

[0015] The cold and hot combined forming method of the eccentric negative curvature thin-walled part provided by the present invention has the following advantages:

[0016] The wall thickness of the formed part is more uniform: the pre-drawn part and the eccentric part are drawn respectively using the first elastic support and the second elastic support. Since the strength of the first elastic support and the second elastic support is lower than that of the rigid mold, elastic deformation occurs after contact with the blank or the pre-drawn part, and surface contact is gradually formed, and the stress field generated acts more uniformly on the blank or the pre-drawn part, thereby making the wall thickness of the formed part more uniform.

[0017] The formed parts are not easy to crack: During the bulging process, the plasticity and elongation of the eccentric parts at high temperature are further improved through the hot bulging forming method, avoiding the cracking and local thinning of the parts; at the same time, the eccentric negative curvature thin-walled parts adopt the cold and hot combined forming of pre-forming drawing, eccentric drawing and hot bulging forming as an overall forming method, which ensures the reliability and stability of the formed parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 A schematic flow chart of a cold and hot combined forming method for an eccentric negative curvature thin-walled part provided in Example 1;

[0020] Figure 2 A schematic diagram of the change from a blank to a formed part provided in Example 1;

[0021] Figure 3 A comparative schematic diagram of a pre-drawn part, an eccentric part and a formed part provided in Example 1;

[0022] Figure 4 A schematic structural diagram of the initial state of the pre-forming drawing die provided in Example 1;

[0023] Figure 5 A schematic structural diagram of the final state of the pre-forming drawing die provided in the first embodiment;

[0024] Figure 6 A schematic structural diagram of the initial state of the eccentric drawing die provided in Example 1;

[0025] Figure 7 A schematic structural diagram of the eccentric drawing die in the final state provided in the first embodiment;

[0026] Figure 8 A schematic structural diagram of the initial state of the bulging die provided in Example 1;

[0027] Fig. 9 This is a schematic structural diagram of the final state of the bulging die provided in Example 1.

[0028] In the figure: 10-preforming drawing die; 11-first elastic support; 12-first pressurizing mechanism; 13-first lower support platform; 14-first upper support platform; 15-first upper die; 16-first edge holding assembly; 17-preforming cavity; 20-blank; 30-pre-drawn part; 40-eccentric drawing die; 41-second elastic support; 42-second pressurizing mechanism; 43-second lower support platform; 44-second upper support platform; 45- The second upper mold; 46-the second edge clamping assembly; 47-the eccentric cavity; 50-the eccentric piece; 60-the forming piece; 70-the bulging mold; 71-the third pressurizing mechanism; 72-the third upper support platform; 73-the third lower support platform; 74-the third upper mold; 75-the third lower mold; 76-the bulging cavity; 77-the pressurizing channel; 78-the exhaust channel; 79-the heating mechanism; 80-the heat-insulating component; 90-the edge clamping ring; 100-the nitrogen spring. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] The purpose of the present invention is to provide a combined cold and hot forming method for eccentric negative curvature thin-walled parts to solve the problems existing in the above-mentioned prior art and meet the forming requirements of eccentric negative curvature thin-walled parts.

[0031] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] Embodiment 1

[0033] This embodiment provides a cold and hot combined forming method for an eccentric negative curvature thin-walled part, see Figure 1 , Figure 2 and Figure 3 , including the steps of drawing process, eccentric process and bulging process; drawing process: pre-drawing the blank 20 by the pre-forming drawing die 10 to obtain a pre-drawn part 30 with a concave cavity feature, such as Figure 2 and Figure 3 The pre-drawn part 30 has a characteristic diameter D1 and a height H as shown; the maximum deformation of the cavity characteristic of the pre-drawn part 30 does not exceed the maximum deformation of the cavity characteristic of the formed part 60; and the pre-forming drawing die 10 includes a first elastic support 11 for supporting the lower side of the blank 20; eccentric treatment: the pre-drawn part 30 is eccentrically drawn by the eccentric drawing die 40 to obtain an eccentric part 50 with an eccentric characteristic, that is, Figure 2 and Figure 3 The eccentric member 50 shown has an eccentric distance of D2, and the maximum deformation of the eccentric characteristic of the eccentric member 50 does not exceed the maximum deformation of the eccentric characteristic of the formed member 60; and the eccentric drawing die 40 includes a second elastic support 41 for supporting the lower side of the eccentric member 50; bulging treatment: the eccentric member 50 is heated, bulged and pressurized by the bulging die 70 to obtain a formed member 60 with a negative curvature characteristic, that is, a negative curvature with a characteristic dimension of D3.

[0034] This embodiment provides a cold and hot combined forming method for an eccentric negative curvature thin-walled part, which has the following advantages:

[0035] The wall thickness of the formed part 60 is more uniform: the pre-drawn part 30 and the eccentric part 50 are drawn respectively using the first elastic support 11 and the second elastic support 41. Since the strength of the first elastic support 11 and the second elastic support 41 is lower than that of the rigid mold, they are elastically deformed after contacting the blank 20 or the pre-drawn part 30, and gradually form surface-to-surface contact, generating a stress field that acts more uniformly on the blank 20 or the pre-drawn part 30, thereby making the wall thickness of the formed part 60 more uniform.

[0036] The formed part 60 is not easy to crack: during the bulging process, the plasticity and elongation of the eccentric part 50 are further improved at high temperature through the hot bulging forming method, thereby avoiding cracking and local thinning of the part; at the same time, the eccentric negative curvature thin-walled part adopts the cold and hot combined forming of pre-forming drawing, eccentric drawing and hot bulging forming as an integral forming method, thereby ensuring the reliability and stability of the formed part 60.

[0037] In the cold and hot combined forming method of the eccentric negative curvature thin-walled part provided in this embodiment, please refer to Figure 4 and Figure 5 The pre-forming drawing die 10 used includes a first pressurizing mechanism 12, a first lower support platform 13, a first upper support platform 14, a first upper die 15, a first edge clamping assembly 16 and a first elastic support 11. The first edge clamping assembly 16 and the first elastic support 11 are fixedly arranged on the first lower support platform 13, and a pre-forming cavity 17 is arranged on the first upper die 15; the lower end of the first pressurizing mechanism 12 is connected to the first upper support platform 14, the first upper die 15 is arranged above the first elastic support 11 and is fixedly connected to the first pressurizing mechanism 12 through the first upper support platform 14, the first edge clamping assembly 16 is arranged between the first upper die 15 and the first elastic support 11 and is used to press the edge of the blank 20; the pre-forming cavity 17 has a concave cavity feature, the first pressurizing mechanism 12 is used to drive the first upper die 15 to move vertically, and to move the blank 20 vertically under the support of the first edge clamping assembly 16, so that the first elastic support 11 can punch the blank 20 to form a pre-drawn part 30 with a concave cavity feature.

[0038] The first upper support platform 14 and the first upper mold 15 are driven by the first pressurizing mechanism 12 to move in a vertical straight line under the guidance of the guide columns on all sides, so that the blank 20 is supported circumferentially by the first edge clamping assembly 16, and the first elastic support 11 punches and draws the middle of the blank 20 to form a concave cavity feature in the pre-forming cavity 17; wherein the first edge clamping assembly 16 can cooperate with the first upper mold 15 to press the circumference to prevent the blank 20 from moving; the first upper support platform 14 and the first pressurizing mechanism 12 can be fixed by a detachable pressure plate to facilitate assembly and disassembly.

[0039] In the cold and hot combined forming method of the eccentric negative curvature thin-walled part provided in this embodiment, please refer to Figure 6 and Figure 7 The eccentric drawing die 40 includes a second pressurizing mechanism 42, a second lower support platform 43, a second upper support platform 44, a second upper die 45, a second edge clamping assembly 46 and a second elastic support 41. The second edge clamping assembly 46 and the second elastic support 41 are fixedly arranged on the second lower support platform 43, and an eccentric cavity 47 is arranged on the second upper die 45; the lower end of the second pressurizing mechanism 42 is connected to the second upper support platform 44, the second upper die 45 is arranged above the second elastic support 41 and is fixedly connected to the second pressurizing mechanism 42 through the second upper support platform 44, the second edge clamping assembly 46 is arranged between the second upper die 45 and the second elastic support 41 and is used to press the edge of the pre-drawn part 60; the eccentric cavity 47 has an eccentric feature, the second pressurizing mechanism 42 is used to drive the second upper die 45 to move vertically, and make the pre-drawn part 60 move vertically under the support of the second edge clamping assembly 46, so that the second elastic support 41 can punch the pre-drawn part 30 to form an eccentric part 50 with an eccentric feature.

[0040] The second upper support platform 44 and the second upper mold 45 are driven by the second pressurizing mechanism 42 to move in a vertical straight line under the guidance of the guide columns on all sides, so that the pre-drawn part 60 is supported circumferentially by the second edge clamping assembly 46, and the second elastic support 41 punches and draws the middle of the pre-drawn part 60 to form an eccentric feature in the eccentric cavity 47; the second edge clamping assembly 46 can cooperate with the second upper mold 45 to press circumferentially to prevent the pre-drawn part 60 from moving; the second upper support platform 44 and the second pressurizing mechanism 42 can be fixed by a detachable pressure plate to facilitate assembly and disassembly.

[0041] In the optional scheme provided in this embodiment, it is more preferred that the first edge holding assembly 16 and the second edge holding assembly 46 both include an edge holding ring 90 and a plurality of nitrogen springs 100, and the nitrogen springs 100 are circumferentially supported on the edge holding ring 90 and the first lower support platform 13 or the second lower support platform 43; the edge holding ring 90 is used to support the circumferential edge of the lower side of the blank 20 or the pre-drawn part 60; the edge holding ring 90 facilitates circumferential pressing of the blank 20 or the pre-drawn part 60, and a plurality of nitrogen springs 100 are used to be distributed circumferentially along the edge of the edge holding ring 90, and the specific number is determined according to actual needs, wherein the clamping force of the nitrogen spring can be controlled by controlling the inflation amount of nitrogen, thereby improving the flexibility of use.

[0042] Further preferably, the first elastic support 11 and the second elastic support 41 are made of polyurethane or nylon, etc., and the nearly uniform loading characteristics of the elastomer are utilized to achieve uniform deformation, avoid local thinning, and control the deformation of the preform within a reasonable range.

[0043] In the optional scheme provided in this embodiment, it is more preferred that the bulging mold 70 includes a third pressurizing mechanism 71, a third upper support platform 72, a third lower support platform 73, a third upper mold 74 and a third lower mold 75; the third upper mold 74 is connected to the third upper support platform 72, and the lower end of the third pressurizing mechanism 71 is connected to the third upper support platform 72; the third lower mold 75 is provided with a bulging cavity 76 with a negative curvature characteristic, and the third upper mold 74 and the third lower mold 75 are used to seal and clamp the eccentric piece 50, and the third upper mold 74 is provided with a pressurizing channel 77 connected to the outside, and the third lower mold 75 is provided with an exhaust channel 78 connected to the inflation cavity 76; and the third upper mold 74 and the third lower mold 75 are provided with a heating mechanism 79; the three pressurizing mechanisms are used to drive the third upper mold 74 to move vertically.

[0044] By setting up the third pressurizing mechanism 71, it is convenient to drive the third upper support platform 72 and the third upper mold 74 to move vertically under the guidance of the surrounding guide columns, and to seal and close the mold with the third lower mold 75 through the circumferentially arranged reinforcing ribs. When sealing and closing the mold, hot expanding gas such as inert gas is introduced through the pressurizing channel 77, so that the eccentric piece 50 is expanded and fits to the inner wall of the expansion cavity 76 under the action of gas pressure, and the excess gas in the expansion cavity 76 is discharged through the exhaust channel 78; the heating mechanism 79 can heat the third upper mold 74 and the third lower mold 75 before closing the mold, and then the eccentric piece 50 can be heated after closing the mold.

[0045] Specifically, the heating mechanism 79 can be set as a heating rod, which should be used for smaller molds or molds that require local heating. It can be set as coil heating when the mold is larger or requires overall heating. The third upper mold 74 and the third lower mold 75 can be made of H13 mold steel, Ni7N and other materials to meet the heating requirements.

[0046] In the optional solutions provided in this embodiment, it is more preferred that the outer walls of the third upper mold 74 and the third lower mold 75 are provided with a heat-insulating component 80 to reduce temperature loss and meet the heat-insulating requirements; specifically, the heat-insulating component 80 can be set as a conventional heat-insulating board.

[0047] In the optional scheme provided in this embodiment, it is more preferred that a cooling component is also provided on the third lower mold 75. When the mold is opened, the third lower mold 75 is cooled by the cooling component so that the formed part 60 can be taken out; specifically, the cooling component can be set as a water-cooling pipe, which is arranged in the third lower mold 75.

[0048] Further preferably, the components of the pre-forming drawing die 10, the eccentric drawing die 40 and the bulging die 70 except the first upper die 15 and the first elastic support 11, the second upper die 45 and the second elastic support 41, and the third upper die 74 and the third lower die 75 can be commonly arranged, that is, one set can be used to save costs, wherein the first upper die 15 and the first elastic support 11, the second upper die 45 and the second elastic support 41, and the third upper die 74 and the third lower die 75 can be detachably connected to the corresponding components by conventional means such as pressing plates or bolts; specifically, the first pressurizing mechanism 12, the second pressurizing mechanism 42 and the third pressurizing mechanism 71 can be arranged as electric cylinders or hydraulic cylinders.

[0049] Among the optional schemes provided in this embodiment, it is more preferred that in the step of bulging treatment, the third upper mold 74 and the third lower mold 75 are first heated and kept warm by the heating mechanism 79, and then the eccentric piece 50 is sealed and pressed between the third upper mold 74 and the third lower mold 75 to heat the eccentric piece 50 to improve the plasticity and elongation, and then pressurized fluid is injected through the pressurizing channel 77 to bulge the eccentric piece 50 to fit the inner wall of the bulging cavity 76 and maintain the pressure until the formed piece 60 is formed.

[0050] Specifically, when the material of the blank 20 is steel, the heating temperature is generally 850-930° C., and when the blank 20 is aluminum alloy, the heating temperature is generally 300-450° C.; the following takes aluminum alloy as an example, including:

[0051] The first elastic support 11 of the pre-drawing die 10 is fixed to the first lower support platform 13, the first upper die 15 is connected to the first press mechanism 12, the blank 20 is placed in the first edge clamping assembly 16, and the first press mechanism 12 is controlled to move at a mold closing rate. The mold is closed to obtain a pre-drawn part 30 with a characteristic diameter D1 = 120 mm and a height H = 60 mm;

[0052] The second elastic support 41 of the eccentric drawing die 40 is fixed to the second lower support platform 43, the second upper die 45 is connected to the second press mechanism 42, the pre-drawn part 30 is placed in the second edge clamping assembly 46, and the clamping speed of the second press mechanism 42 is controlled. The mold is closed to obtain an eccentric member 50 with an eccentric distance of D2 = 30 mm;

[0053] The third upper mold 74 and the third lower mold 75 of the bulging mold 70 are heated to a certain temperature in the range of 400 to 450° C. for 30 to 60 minutes;

[0054] The eccentric member 50 is placed in the bulging die 70, and then the pressure rate of the third pressurizing mechanism 71 is controlled. Inflate and pressurize to 8-20 MPa, perform negative curvature forming with a characteristic dimension of D3=20 mm on the eccentric piece 50, and gradually make the eccentric piece 50 stick to the mold, then increase the air pressure in the bulging mold 70, and keep the pressure for 30-120 seconds, so that the eccentric piece 50 after bulging is stuck to the film and shaped to the formed piece 60;

[0055] After the forming is completed, the mold is opened and the formed part 60 is taken out.

[0056] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A hot and cold combined forming method for eccentric negative curvature thin-walled parts, characterized in that: Includes steps: Drawing process: pre-drawing the blank (20) by means of a pre-forming drawing die (10) to obtain a pre-drawn part (30) having a concave cavity feature; the maximum deformation amount of the concave cavity feature of the pre-drawn part (30) does not exceed the maximum deformation amount of the concave cavity feature of the formed part (60); and the pre-forming drawing die (10) comprises a first elastic support (11) for supporting the lower side of the blank (20); Eccentric treatment: the pre-drawn part (30) is eccentrically drawn by an eccentric drawing die (40) to obtain an eccentric part (50) having an eccentric feature, wherein the maximum deformation of the eccentric feature of the eccentric part (50) does not exceed the maximum deformation of the eccentric feature of the formed part (60); and the eccentric drawing die (40) comprises a second elastic support (41) for supporting the lower side of the eccentric part (50); Bulging treatment: The eccentric piece (50) is heated, bulged and pressure-maintained by a bulging die (70) to obtain the formed piece (60) having a negative curvature characteristic; when the material of the blank (20) is steel, the heating temperature is 850-930°C; when the blank (20) is aluminum alloy, the heating temperature is 300-450°C; the bulging die (70) is pressurized to 8-20 MPa, the eccentric piece (50) is negatively curvature-formed, and the eccentric piece (50) is gradually molded in the bulging die (70), and then the pressure in the bulging die (70) is increased to maintain the pressure for 30-120 seconds, so that the eccentric piece (50) is formed into the formed piece (60).

2. The hot and cold combined forming method of the eccentric negative curvature thin-walled part according to claim 1, characterized in that: The preforming drawing die (10) comprises a first pressurizing mechanism (12), a first lower support platform (13), a first upper support platform (14), a first upper die (15), a first edge clamping assembly (16) and the first elastic support (11), wherein the first edge clamping assembly (16) and the first elastic support (11) are fixedly arranged on the first lower support platform (13), and the first upper die (15) is provided with a preforming cavity (17); the lower end of the first pressurizing mechanism (12) is connected to the first upper support platform (14), and the first upper die (15) is arranged above the first elastic support (11) and passes through the first An upper support platform (14) is fixedly connected to the first pressurizing mechanism (12); the first edge clamping assembly (16) is arranged between the first upper mold (15) and the first elastic support (11) and is used to clamp the edge of the blank (20); the pre-forming cavity (17) has a concave cavity feature; the first pressurizing mechanism (12) is used to drive the first upper mold (15) to move vertically, and to move the blank (20) vertically under the support of the first edge clamping assembly (16), so that the first elastic support (11) can punch the blank (20) to form the pre-drawn part (30) with a concave cavity feature.

3. The hot and cold combined forming method of the eccentric negative curvature thin-walled part according to claim 2, characterized in that: The eccentric drawing die (40) comprises a second pressurizing mechanism (42), a second lower support platform (43), a second upper support platform (44), a second upper die (45), a second edge clamping assembly (46) and the second elastic support (41), wherein the second edge clamping assembly (46) and the second elastic support (41) are fixedly arranged on the second lower support platform (43), and an eccentric cavity (47) is arranged on the second upper die (45); the lower end of the second pressurizing mechanism (42) is connected to the second upper support platform (44), and the second upper die (45) is arranged above the second elastic support (41) and is connected to the second upper support platform (44). The support platform (44) is fixedly connected to the second pressurizing mechanism (42); the second edge clamping assembly (46) is arranged between the second upper mold (45) and the second elastic support (41) and is used to press the edge of the pre-drawn part (30); the eccentric cavity (47) has an eccentric feature; the second pressurizing mechanism (42) is used to drive the second upper mold (45) to move vertically, and to move the pre-drawn part (30) vertically under the support of the second edge clamping assembly (46), so that the second elastic support (41) can stamp the pre-drawn part (30) to form the eccentric part (50) with an eccentric feature.

4. The hot and cold combined forming method of the eccentric negative curvature thin-walled part according to claim 3, characterized in that: The first edge holding assembly (16) and the second edge holding assembly (46) both include an edge holding ring (90) and a plurality of nitrogen springs (100), wherein the nitrogen springs (100) are circumferentially supported on the edge holding ring (90) and the first lower support platform (13) or the second lower support platform (43); the edge holding ring (90) is used to support the circumferential edge of the lower side of the blank (20) or the pre-drawn part (30).

5. The hot and cold combined forming method of the eccentric negative curvature thin-walled part according to claim 1, characterized in that: The bulging mold (70) includes a third pressurizing mechanism (71), a third upper support platform (72), a third lower support platform (73), a third upper mold (74) and a third lower mold (75); the third upper mold (74) is connected to the third upper support platform (72), and the lower end of the third pressurizing mechanism (71) is connected to the third upper support platform (72); the third lower mold (75) is provided with a bulging cavity (76) having a negative curvature characteristic, and the third upper mold (74) and the third lower mold (75) are used to seal and press the eccentric piece (50), and the third upper mold (74) is provided with a pressurizing channel (77) connected to the outside, and the third lower mold (75) is provided with an exhaust channel (78) connected to the bulging cavity (76); and the third upper mold (74) and the third lower mold (75) are provided with a heating mechanism (79); the three pressurizing mechanisms are used to drive the third upper mold (74) to move vertically.

6. The hot and cold combined forming method of the eccentric negative curvature thin-walled part according to claim 5, characterized in that: The outer walls of the third upper mold (74) and the third lower mold (75) are provided with heat-insulating components (80).

7. The hot and cold combined forming method of the eccentric negative curvature thin-walled part according to claim 6, characterized in that: The third lower mold (75) is also provided with a cooling component.

8. The hot and cold combined forming method of the eccentric negative curvature thin-walled part according to claim 5, characterized in that: In the step of bulging treatment, the third upper mold (74) and the third lower mold (75) are first heated and kept warm by the heating mechanism (79), and then the eccentric piece (50) is sealed and pressed between the third upper mold (74) and the third lower mold (75), and then pressurized fluid is injected through the pressurized channel (77) to bulge the eccentric piece (50) to fit the inner wall of the bulging cavity (76) and maintain the pressure.

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