A method for warm extrusion composite forming of hemispherical parts

Abstract

This invention discloses a warm extrusion composite forming method for hemispherical parts. The part is a thin-walled high-strength steel profile, and its structure includes a curved surface, a uniform wall thickness with flanges, and a straight section. The forming method includes: Step 1: blanking; Step 2: punching holes in the blank; Step 3: hole enlargement and flange turning; Step 4: reverse flange turning; Step 5: thinning and spinning: installing the spinning blank and adjusting the full runout, calculating the thinning and spinning wall thickness and maximum outer diameter based on the area and volume of the thin-walled hemispherical profile, performing the first thinning and spinning, installing the limiting fixture, and performing the second thinning and spinning; Step 6: stamping and bending to form a typical hemispherical part. This invention simplifies the production and processing procedures through the above technical solution, avoids cumbersome long-cycle processes such as forging and heat treatment, effectively improves production efficiency, increases material utilization, and reduces production costs.

Description

Technical Field

[0001] This invention belongs to the field of solid rocket engine processing and manufacturing technology, specifically relating to a warm extrusion composite forming method for hemispherical parts. Background Technology

[0002] The hemispherical part is a typical component of the solid rocket motor combustion chamber shell in the aerospace field. Currently, such parts are mainly produced by forging and turning, which results in low processing efficiency and significant material waste. Furthermore, since forging and turning usually require subsequent annealing, the production cycle is extended, further reducing efficiency. At the same time, when the workpiece is large in size, thin in wall thickness, and has high performance requirements, traditional forging cannot adequately guarantee the part's performance, easily leading to forging defects such as overheating and burning. These defects severely affect the performance of the solid rocket motor combustion chamber shell and pose safety hazards. Summary of the Invention

[0003] The technical problem solved by this invention is to overcome the shortcomings of the prior art and propose a warm extrusion composite forming method for hemispherical parts. This method can effectively avoid the disadvantages of low material utilization and low processing efficiency caused by forging, turning and other processes. After warm extrusion composite forming, there are fewer processing steps, production efficiency is effectively guaranteed, material utilization is higher and the performance of parts is better.

[0004] The solution of the present invention is:

[0005] A method for warm extrusion composite forming of a hemispherical part, wherein the hemispherical part is a thin-walled high-strength steel profile, and its structure includes a curved surface, a flange with uniform wall thickness, and a straight section, comprising:

[0006] Step 1: Blanking, select round cake-shaped raw material as the initial blank;

[0007] Step 2: Use a punching die to punch and shape the initial blank, turning the blank into a round disc-shaped structure with holes, the diameter of the center hole being smaller than the center hole size of the final workpiece;

[0008] Step 3: Use a hole-expanding and flanging die to expand and flanging the hole to form a "T"-shaped blank structure with a central hole;

[0009] Step 4: Use a reverse flanging die to perform reverse flanging forming, forming a reverse flanging blank with an arc-shaped flanging structure consistent with the final workpiece;

[0010] Step 5: Using the first and second thinning spinning dies, the variable wall thickness profile of the hemispherical part is formed by secondary thinning spinning.

[0011] Step 6: Use a stamping bending die to perform stamping bending forming to complete the bending forming of the variable wall thickness surface structure, and finally obtain the hemispherical part structure.

[0012] Furthermore, the punching die includes a first lower die (21), a first limiting plate (22), and a first warm extrusion core die (23);

[0013] The initial blank is punched and formed, specifically as follows:

[0014] The initial blank is placed in the cavity of the first lower die (21), the first limiting plate (22) is placed above the initial blank, the initial blank is pressed, the initial blank is heated to an appropriate temperature below the recrystallization temperature of the metal, and the first extrusion core die (23) is used to punch the initial blank through the central through hole of the first limiting plate (22). Due to the space limitation of the upper and lower dies, the initial blank forms a disc-shaped structure with a central hole during the punching process.

[0015] Furthermore, the enlarged and flanged die includes: a second lower die (31), a second limiting plate (32), and a second temperature extrusion core die (33);

[0016] The process of enlarging and flanging is specifically as follows:

[0017] The blank after punching is placed in the cavity of the second lower die (31), the second limiting plate (32) is placed above the blank, the blank is pressed, the blank is kept heated, and the conical structure at the top of the second temperature extrusion core die (33) moves downward, so that the center hole of the blank is expanded to be consistent with the center hole of the workpiece, forming a T-shaped blank structure with a center hole.

[0018] Furthermore, when heating the initial blank to a suitable temperature below the recrystallization temperature of the metal, such as 800℃~900℃, the second lower mold (31), the second limiting plate (32) and the blank are heated together to 800℃~900℃ during the hole expansion and flanging forming.

[0019] Furthermore, the reverse flanging die includes: a third lower die (41), a third limiting plate (42), a T-shaped punch (43), and a positioning post (44);

[0020] The reverse flanging process is performed as follows:

[0021] The T-shaped blank structure is placed in the third lower die (41), and the blank is restricted in the die by the third limiting plate (42) to prevent the blank from deforming during punching. The positioning pin (44) is used to position the third lower die (41), the third limiting plate (42) and the T-shaped punch (43), while ensuring that the inner hole of the blank remains unchanged during the punching process. The blank is heated to an appropriate temperature below the recrystallization temperature of the metal, and the T-shaped punch (43) is used for reverse flanging punching, thereby forming a reverse flanged blank with an arc-shaped flanged structure consistent with the final workpiece.

[0022] Furthermore, when performing reverse flanging forming, heating the blank to an appropriate temperature below the metal recrystallization temperature specifically means heating the T-shaped blank, the third lower die (41), the third limiting plate (42), and the T-shaped punch (43) together to 800℃~900℃.

[0023] Furthermore, the first thinning spinning die includes: a first core mold (51), a first limiting nut (52), and a first spinning wheel (53);

[0024] The second thinning spinning die includes: a limiting fixture (61), a second core mold (62), a second limiting nut (63), and a second spinning wheel (64);

[0025] The process of completing the secondary thinning spinning of the variable wall thickness surface structure of the hemispherical part is as follows: the reverse flange blank is placed on the first core mold (51), and the reverse flange blank is positioned and restricted by the first limiting nut (52). According to the calculated deformation process parameters, the first spinning wheel (53) executes the predetermined first thinning spinning program to complete the first thinning spinning of the thin-wall curved surface structure of the hemispherical part.

[0026] After the first thinning spinning is completed, the hemispherical part undergoes a second thinning spinning. The blank after the first thinning spinning is placed on the second core mold (62), and the blank is positioned and restricted by the limiting fixture (61). The limiting fixture (61) is pressed to the surface of the blank by the second limiting nut (63). According to the calculated deformation process parameters, the second spinning wheel (64) executes the predetermined second thinning spinning program to complete the second thinning spinning of the hemispherical part with a variable wall thickness profile.

[0027] Furthermore, the use of the stamping bending die includes a forming die (71), a forming punch (72), and a segmented bending die (73);

[0028] The stamping bending forming is specifically performed as follows: when the forming punch (72) moves downward, the thin-walled structure gradually bends until it is completely in contact with the forming die (71) and the forming punch (72) to form a matching three-centered spherical surface structure; when the forming die (71) and the forming punch (72) are not withdrawn, the segmented bending die (73) moves from the outside to the center to complete the bending forming of the variable wall thickness surface structure, and finally obtains the hemispherical part structure.

[0029] Furthermore, the hemispherical part has an outer diameter of 460mm at its large end, an inner diameter of 84mm at its center hole, a workpiece height of 173mm, and a curved surface thickness of 6mm.

[0030] Furthermore, the hemispherical part is designed to be made of 30Cr3SiNiMoVA high-strength steel.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] (1) The present invention can realize the forming of hemispherical parts by using a step-by-step combination mold method. The blank is processed by step-by-step processing method, combining stamping, thinning spinning and sheet metal forming steps, and a hemispherical workpiece with curved surface and equal wall thickness flange structure is obtained.

[0033] (2) The method proposed in this invention uses a simple round blank, which avoids processing steps such as forging and heat treatment, shortens the processing cycle and improves production efficiency.

[0034] (3) The workpiece formed by the present invention has strong versatility and interchangeability. It can be used for the integral forming of thick-walled parts with flanges such as rotating curved surfaces of various types of structures, which can effectively ensure the performance of the workpiece and at the same time greatly improve the material utilization rate. Attached Figure Description

[0035] By reading the detailed description of the preferred embodiments below, various other advantages and benefits will become more apparent to those skilled in the art as illustrated in the figures. The figures are for illustrative purposes only and are not intended to limit the invention. Throughout the figures, the same reference numerals will be used to identify the same parts. In the figures:

[0036] Figure 1 This is a schematic diagram of a typical curved surface, uniform wall thickness, and flanged hemispherical workpiece structure.

[0037] Figure 2 This is a process flow diagram of a warm extrusion composite forming method for hemispherical parts according to the present invention;

[0038] Figure 3 This is a schematic diagram of the initial blank structure of the present invention;

[0039] Figure 4 This is a schematic diagram of the hot extrusion process of the billet according to the present invention;

[0040] Figure 5 This is a schematic diagram of the hot extrusion and flanging process of the billet according to the present invention;

[0041] Figure 6 This is a schematic diagram of the reverse flanging process of the blank in this invention;

[0042] Figure 7 This is a schematic diagram of the first thinning and spinning process of the billet in this invention;

[0043] Figure 8 This is a schematic diagram of the second thinning and spinning process of the billet in this invention;

[0044] Figure 9 This is a schematic diagram of the blank stamping and bending forming process of the present invention. Figure 1 ;

[0045] Figure 10 This is a schematic diagram of the blank stamping and bending forming process of the present invention. Figure 2 . Detailed Implementation

[0046] The following will combine Figures 1-9 The invention will be further described in conjunction with the embodiments, and the features and advantages of the invention will become clearer and more explicit with these descriptions.

[0047] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments. Although various aspects of embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated otherwise.

[0048] This invention proposes a warm extrusion composite forming method for hemispherical parts. The hemispherical part is a thin-walled, high-strength steel profile, and its structure includes curved surfaces, uniform wall thickness with flanges, and straight sections, such as... Figure 1 The diagram shows a typical curved surface, uniform wall thickness, and flanged hemispherical workpiece structure.

[0049] like Figure 2 As shown, the forming method includes the following steps:

[0050] Step 1: Blanking, select round cake-shaped raw material as the initial blank;

[0051] Step 2: Use a punching die to punch and shape the initial blank, turning the blank into a round disc-shaped structure with holes, the diameter of the center hole being smaller than the center hole size of the final workpiece;

[0052] Step 3: Use a hole-expanding and flanging die to expand and flanging the hole to form a "T"-shaped blank structure with a central hole;

[0053] Step 4: Use a reverse flanging die to perform reverse flanging forming, forming a reverse flanging blank with an arc-shaped flanging structure consistent with the final workpiece;

[0054] Step 5: Using the first and second thinning spinning dies, the variable wall thickness profile of the hemispherical part is formed by secondary thinning spinning.

[0055] Step 6: Use a stamping bending die to perform stamping bending forming to complete the bending forming of the variable wall thickness surface structure, and finally obtain the hemispherical part structure.

[0056] The following is a detailed introduction.

[0057] Step 1, as follows Figure 3As shown, the blanking process for the hemispherical part includes: initial blank 1; a disc-shaped raw material is selected as the blank, and the blank design is determined according to the principle of constant volume, based on the final part volume or weight.

[0058] Step two, as Figure 4 As shown, the hemispherical part is formed by punching a blank. The punching die includes a lower die a21, a limiting plate a22, and a warm extrusion die a23. The initial blank 1 is placed in the lower die a21, and the limiting plate a22 restricts the blank within the die to prevent deformation during punching. The blank, the lower die a21, and the limiting plate a22 are heated together to a suitable temperature below the metal recrystallization temperature, approximately 800°C to 900°C. The warm extrusion die a23 passes through the central through hole of the limiting plate a22 to punch the blank into a perforated disc-shaped structure.

[0059] To further optimize, in step two of the forming method described above, the center hole formed by the warm extrusion die a23 should be smaller than the center hole size of the final workpiece, and this should be adjusted and determined according to the final workpiece and subsequent steps.

[0060] Step 3, as Figure 5 As shown, the hemispherical part undergoes hole enlargement and flanging forming. The hole enlargement and flanging mold includes: a lower mold b31, a limiting plate b32, and a warm extrusion core mold b33. The blank after punching in step two is placed in the lower mold b31. The limiting plate b32 restricts the blank within the mold to prevent deformation during punching. The blank, lower mold b31, and limiting plate b32 are heated together to an appropriate temperature below the metal recrystallization temperature, approximately 800°C to 900°C. The conical structure at the top of the warm extrusion core mold b33 expands the center hole of the blank to match the center hole of the workpiece as it moves downward, forming a T-shaped blank structure with a central hole.

[0061] Further optimization involves step 3 of the forming method described above, where the center portion of the side where the blank meets the warm extrusion die b33 will form a rounded flange that matches the outer wall of the warm extrusion die.

[0062] Step four, as Figure 6As shown, the hemispherical part undergoes reverse flanging forming. The reverse flanging mold includes: a lower mold c41, a limiting plate c42, a T-shaped punch 43, and a positioning post 44. The T-shaped blank, after the hole enlargement and flanging in step three, is placed inside the lower mold c41. The limiting plate c42 confines the blank within the mold to prevent deformation during punching. The positioning post 44 passes through the T-shaped blank, the lower mold c41, and the limiting plate c42. The center of the T-shaped punch 43 passes through... Positioning pin 44 ensures that the inner hole of the blank remains unchanged during the stamping process, keeping the axis of the "T"-shaped blank, lower die c41, limiting plate c42, and T-shaped punch 43 aligned, and heating them together to an appropriate temperature below the metal recrystallization temperature, approximately 800℃~900℃. The T-shaped punch 43 moves downward to reverse the "T"-shaped blank, thereby forming a reverse-flanged blank with an arc-shaped flanged structure consistent with the final workpiece.

[0063] To further optimize the process, in step 4 of the forming method described above, the blank and the positioning pin must pass through the blank and all molds simultaneously to accurately position the relative positions of the blank and the molds.

[0064] Step 5, as Figure 7 As shown, the hemispherical part undergoes its first thinning spinning process. The first thinning spinning mold includes a core mold a51, a limiting nut a52, and a spinning wheel a53. The blank, which has been finished by the reverse flanging in step four, is placed on the core mold a51, and the blank is positioned and restricted by the limiting nut a52. According to the calculated deformation process parameters, the spinning wheel a53 executes the predetermined first thinning spinning program to complete the first thinning spinning of the thin-walled curved surface structure of the hemispherical part.

[0065] Figure 8 As shown, after the first thinning spinning process is completed, the hemispherical part undergoes a second thinning spinning process. The second thinning spinning mold includes a core mold b62, a limiting fixture 61, a limiting nut b63, and a spinning wheel b64. The blank after the first thinning spinning process is placed on the core mold b62, and the limiting fixture 61 is used to position and restrict the blank. The limiting nut b63 is used to press the limiting fixture 61 to the surface of the blank. According to the calculated deformation process parameters, the spinning wheel b64 executes the predetermined second thinning spinning program to complete the second thinning spinning process of the hemispherical part with a variable wall thickness profile.

[0066] Further optimization involves step 5 of the forming method described above. Due to the influence of material plasticity, multiple spinning passes can be performed when the thinning amount is insufficient, until the final requirement is met. The number of spinning passes, rotation speed, feed rate, and other parameters are jointly determined by the thickness of the spinning blank, the ultimate thinning rate, and the final wall thickness of the part.

[0067] Step six, as Figure 9As shown, the hemispherical part is formed by stamping and bending. The stamping and bending die includes: a forming die 71, a forming punch 72, and a segmented bending die 73. The blank, after thinning and spinning in step five, is placed on the forming die 71. As the forming punch 72 moves downward, the thin-walled structure gradually bends until it is completely fitted with the forming die 71 and the forming punch 72, forming a matching three-centered spherical surface structure. Without removing the forming die 71 and the forming punch 72, the segmented bending die 73 moves from the outside to the center to complete the bending of the variable wall thickness surface structure, finally obtaining a typical hemispherical part structure, such as... Figure 10 As shown.

[0068] To further optimize this process, in step 6 of the forming method described above, when the segmented bending die is in operation, the blank, forming die, and forming punch should remain in the state they were in when the first stamping bending was completed.

[0069] It cannot be separated or disassembled, and a qualified hemispherical workpiece is finally obtained.

[0070] In this invention, the extrusion core die a 23, the warm extrusion core die b 33, the positioning post 44, the core die a 51, the limiting tooling 61, the forming die 71, the forming punch 72, and the segmented bending die 73 are designed according to the internal and / or external surface structure and dimensions of the hemispherical workpiece.

[0071] Example:

[0072] This embodiment also provides a method for thermoforming a hemispherical structure, such as... Figure 1 As shown, a complex-shaped, uniformly thick-walled, flanged hemispherical part has an outer diameter of 460mm at its large end, an inner diameter of 84mm at its center hole, a workpiece height of 173mm, and a curved surface thickness of 6mm. The designed material is 30Cr3SiNiMoVA high-strength steel. Figures 3-9 As shown, the specific steps include:

[0073] Step 1: Blanking. Select a round, disc-shaped raw material as the blank for the part to be processed. The blank design follows the principle of constant volume and is determined based on the final volume or weight of the part.

[0074] Step 2: Blank punching. The initial blank 1 is placed in the lower die a21. The blank is restricted in the die by the limiting plate a22 to prevent the blank from deforming during punching. The blank, lower die a21 and limiting plate a22 are heated together to an appropriate temperature below the metal recrystallization temperature, about 800℃~900℃. The blank is punched into a perforated disc structure by the warm extrusion core die a23 passing through the central through hole of the limiting plate a22.

[0075] Step 3: Hole enlargement and flanging. Place the blank obtained in step 2 into the cavity of the lower die b31. The blank is restricted in the die by the limiting plate b32 to prevent the blank from deforming during punching. Keep the blank heated to 800℃~900℃. The conical structure at the top of the hot extrusion core die b33 will expand the center hole of the blank to match the center hole of the workpiece as it moves downward, forming a "T" shaped blank structure with a center hole.

[0076] Step 4: Reverse the edge, flip the blank and place it in the cavity of the lower die c41. Keep the blank heated to 800℃~900℃. The blank is restricted in the die by the limiting plate c42. The positioning pin 44 passes through the "T" shaped blank, the lower die c41, and the limiting plate c42. The center of the T-shaped punch 43 passes through the positioning pin 44. The T-shaped punch 43 is used to punch the blank into a short "+" shaped structure with a hole in the center.

[0077] Step 5: Thinning and spinning;

[0078] Step 5.1: First thinning spinning. Install mandrel a51 on the spinning machine spindle and adjust the radial runout of the outer circle of mandrel a51, keeping it within 0.05mm. Install the short "+" shaped blank with a center hole from Step 4 onto mandrel a51. Use the limiting nut a52 to position and limit the blank. Determine the spinning process parameters according to the blank thickness, the ultimate thinning rate, and the final thickness of the part. Set the spinning program based on the designed spinning path trajectory and execute the program steps. The spinning process parameters for each pass in the program are as follows: spindle speed 120r / min, feed rate 1mm / min, spinning fillet radius R4, to perform the first thinning spinning.

[0079] Step 5.2: Second thinning spinning. Install the mandrel b62 on the spinning machine spindle and adjust the radial runout of the outer circle of the mandrel b62, keeping it within 0.05mm. Install the blank from the first thinning spinning onto the mandrel b62. Use the limiting fixture 61 to limit the area formed by the first thinning spinning. Use the limiting nut b63 to press the limiting fixture 61 to the blank surface and keep it fixed. Determine the spinning process parameters according to the blank thickness, the ultimate thinning rate, and the final thickness of the part. Set the spinning program based on the designed spinning path trajectory and execute the program steps. The spinning process parameters for each pass in the program are as follows: spindle speed 120r / min, feed rate 0.8mm / min, spinning fillet radius R4, and perform the second thinning spinning.

[0080] Step 6: Stamping and bending deformation; Place the blank obtained from the thinning and spinning process in Step 5 on the upper cavity of the forming die 71, and use the forming punch 72 to bend the thin-walled area downwards. The blank is gradually bent until it is completely in contact with the forming die 71 and the forming punch 72, forming a matching three-centered spherical surface structure; Without removing the forming die 71 and the forming punch 72, use the segmented bending die 73 to move from the outside to the center to complete the bending and forming of the variable wall thickness surface structure, and finally obtain a typical hemispherical part structure.

[0081] This invention discloses a warm extrusion composite forming method for hemispherical parts, producing workpieces that meet the structural and dimensional requirements of the design drawings. Furthermore, this forming method is highly applicable, with simplified processing steps, avoiding cumbersome long-cycle processes such as forging and heat treatment, effectively improving production efficiency, increasing material utilization, and reducing production costs. Based on the structural characteristics of the workpiece, this forming method combines warm extrusion, thinning spinning, and sheet metal forming. With the assistance of forming dies and limiting dies, it effectively ensures the processing and production of hemispherical workpieces with curved surfaces, uniform wall thickness with flanges, and straight sections.

[0082] The workpieces formed by this invention have strong interchangeability and can be applied to the forming of various similar or related irregular surface parts. The forming method can realize the integral forming of the workpiece, eliminating the need for material reduction methods such as turning. It has good overall performance and high material utilization.

[0083] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for warm extrusion composite forming of a hemispherical part, wherein the hemispherical part is a thin-walled high-strength steel profile, the structure of which includes a curved surface, a flange with equal wall thickness, and a straight section, characterized in that... include: Step 1: Blanking, select round cake-shaped raw material as the initial blank; Step 2: Use a punching die to punch and shape the initial blank, turning the blank into a round disc-shaped structure with holes, the diameter of the center hole being smaller than the center hole size of the final workpiece; Step 3: Use a hole-expanding and flanging die to expand and flanging the hole to form a "T"-shaped blank structure with a central hole; Step 4: Use a reverse flanging die to perform reverse flanging forming to form a reverse flanging blank with an arc-shaped flanging structure consistent with the final workpiece; the reverse flanging die includes: a third lower die (41), a third limiting plate (42), a T-shaped punch (43) and a positioning post (44). The reverse flanging process is performed as follows: The T-shaped blank structure is placed in the third lower die (41), and the blank is restricted in the die by the third limiting plate (42) to prevent the blank from deforming during punching. The positioning pin (44) is used to position the third lower die (41), the third limiting plate (42) and the T-shaped punch (43), while ensuring that the inner hole of the blank remains unchanged during the punching process. The blank is heated to an appropriate temperature below the recrystallization temperature of the metal, and the T-shaped punch (43) is used for reverse flanging punching, thereby forming a reverse flanging blank with an arc-shaped flanging structure consistent with the final workpiece. Step 5: Using the first and second thinning spinning dies, the variable wall thickness profile of the hemispherical part is formed by secondary thinning spinning. Step 6: Use a stamping bending die to perform stamping bending forming to complete the bending forming of the variable wall thickness surface structure, and finally obtain the hemispherical part structure; The stamping bending die includes a forming die (71), a forming punch (72), and a segmented bending die (73); the stamping bending forming is performed by using the forming punch (72) to move downwards so that the thin-walled structure gradually bends until it is completely in contact with the forming die (71) and the forming punch (72) to form a matching three-centered spherical surface structure; without withdrawing the forming die (71) and the forming punch (72), the segmented bending die (73) moves from the outside to the center to complete the bending forming of the variable wall thickness surface structure, and finally obtains the hemispherical part structure.

2. The method for warm extrusion composite forming of a hemispherical part according to claim 1, characterized in that: The punching die includes a first lower die (21), a first limiting plate (22), and a first warm extrusion core die (23). The initial blank is punched and formed, specifically as follows: The initial blank is placed in the cavity of the first lower die (21), the first limiting plate (22) is placed above the initial blank, the initial blank is pressed, the initial blank is heated to an appropriate temperature below the recrystallization temperature of the metal, and the first warm extrusion core die (23) is used to punch the initial blank through the central through hole of the first limiting plate (22). Due to the space limitation of the upper and lower dies, the initial blank forms a disc-shaped structure with a central hole during the punching process.

3. The method for warm extrusion composite forming of a hemispherical part according to claim 2, characterized in that: The enlarged and flanged die includes: a second lower die (31), a second limiting plate (32), and a second temperature extrusion core die (33). The process of enlarging and flanging is specifically as follows: The blank after punching is placed in the cavity of the second lower die (31), the second limiting plate (32) is placed above the blank, the blank is pressed, the blank is kept heated, and the conical structure at the top of the second temperature extrusion core die (33) moves downward, so that the center hole of the blank is expanded to be consistent with the center hole of the workpiece, forming a T-shaped blank structure with a center hole.

4. The warm extrusion composite forming method for a hemispherical part according to claim 3, characterized in that: When heating the initial blank to a suitable temperature below the recrystallization temperature of metal, such as 800℃~900℃, and performing hole expansion and flanging forming, the second lower mold (31), the second limiting plate (32) and the blank are heated together to 800℃~900℃.

5. The method for warm extrusion composite forming of hemispherical parts according to claim 1, in the reverse flanging stage, is characterized in that: When performing reverse flanging forming, heating the blank to an appropriate temperature below the metal recrystallization temperature specifically means heating the T-shaped blank, the third lower die (41), the third limiting plate (42), and the T-shaped punch (43) together to 800℃~900℃.

6. The method for warm extrusion composite forming of hemispherical parts according to claim 1, in the reverse flanging stage, is characterized in that: The first thinning spinning die includes: a first core mold (51), a first limiting nut (52), and a first spinning wheel (53); The second thinning spinning die includes: a limiting fixture (61), a second core mold (62), a second limiting nut (63), and a second spinning wheel (64); The process of completing the secondary thinning spinning of the hemispherical part with a variable wall thickness surface structure is as follows: the reverse flange blank is placed on the first core mold (51), and the reverse flange blank is positioned and restricted by the first limiting nut (52). According to the calculated deformation process parameters, the first spinning wheel (53) executes the predetermined first thinning spinning program to complete the first thinning spinning of the hemispherical part with a thin wall curved surface structure. After the first thinning spinning is completed, the hemispherical part undergoes a second thinning spinning. The blank after the first thinning spinning is placed on the second core mold (62), and the blank is positioned and restricted by the limiting fixture (61). The limiting fixture (61) is pressed to the surface of the blank by the second limiting nut (63). According to the calculated deformation process parameters, the second spinning wheel (64) executes the predetermined second thinning spinning program to complete the second thinning spinning of the hemispherical part with a variable wall thickness profile.

7. The method for warm extrusion composite forming of hemispherical parts according to claim 1, in the reverse flanging stage, is characterized in that: The hemispherical part has an outer diameter of 460mm at its large end, an inner diameter of 84mm at its center hole, a workpiece height of 173mm, and a curved surface thickness of 6mm.

8. The method for warm extrusion composite forming of hemispherical parts according to claim 1, in the reverse flanging stage, is characterized in that: The hemispherical part is designed to be made of 30Cr3SiNiMoVA high-strength steel.

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