Hot forming method and integral forming die for ultra-long thin-wall conical cylindrical part

Abstract

The invention provides a hot forming die and method for an ultra-long thin-wall conical cylindrical part. The forming die comprises an upper female die unit, a lower female die unit, a die assembly guide unit and a core die unit. In the machining process, the core mold unit is used for installing and positioning an unfolding working procedure piece of the conical cylinder-shaped part to be machined. The lower female die units are installed in the supporting structures at the two ends of the die assembly guiding unit. The core die unit is located in an inner cavity formed after the lower female die unit and the upper female die unit are closed, and the two ends of the core die unit are supported through supporting structures at the two ends of the die closing guide unit. Under a high-temperature state, the ultra-long small-diameter conical cylinder is integrally pressed and formed through opposite movement and mold closing of the upper female mold and the lower female mold and a fixed core mold forming mold, and precise forming of the conical cylinder part is completed in the one-time mold closing process.

Description

Technical Field

[0001] The invention relates to a hot forming method for an ultra-long tapered cylindrical part and a double-station integral die, belonging to the field of sheet metal and hot forming technology equipment. Background Art

[0002] Currently, titanium alloy parts are widely used in aerospace and other product applications, and production requirements for these parts are evolving towards higher efficiency, lower costs, and larger batch sizes. High-strength titanium alloys have a low elastic modulus, resulting in significant springback after forming. Conventional sheet metal cold-formed cone forming processes cannot meet these requirements, resulting in localized cracking of the cone, making it impossible to form these parts. The structural characteristics of thin-walled, ultra-long, small-diameter cones make existing hot forming processes unable to meet the overall forming accuracy requirements; the forming accuracy is too low to meet the requirements of subsequent welding processes. Summary of the Invention

[0003] The technical problem solved by the present invention is: in order to solve the problem of integral forming of ultra-long thin-walled conical cylindrical parts, the present invention provides an ultra-long thin-walled conical cylindrical part hot forming method and an integral forming mold. Under high temperature conditions, the upper and lower concave molds move toward each other to close the mold and the fixed core mold forming mold is used to integrally press and form the ultra-long small-diameter conical cylinder, so that the conical cylinder parts can be accurately formed in one closing process.

[0004] The technical solution adopted by the present invention is: a thermoforming die for an ultra-long thin-walled conical cylindrical part, comprising an upper die unit, a lower die unit, a clamping guide unit, and a core die unit;

[0005] During the processing, the core mold unit is used to install and position the unfolded process parts of the conical cylindrical parts to be processed; the lower die unit is installed in the supporting structures at both ends of the mold closing guide unit; the core mold unit is located in the inner cavity after the lower die unit and the upper die unit are closed, and the two ends are supported by the supporting structures at both ends of the mold closing guide unit.

[0006] Furthermore, the upper die unit includes an upper die unit mounting platform, upper and lower die closing guide wedges, pre-positioning pin avoidance holes, a forming process part die surface, an upper die and core die closing guide seat, and a temperature measuring hole; the forming process part die surface is arranged inward on the lower surface of the upper die unit mounting platform, and upper and lower die closing guide wedges are respectively arranged at the center positions of the two side surfaces of the upper die unit mounting platform, and temperature measuring holes are respectively arranged on the upper and lower die closing guide wedges; pre-positioning pin avoidance holes are respectively arranged at both ends of the upper surface of the upper die unit mounting platform along the central symmetry axis of the forming process part die surface; and the upper die and core die closing guide seats are respectively arranged at the large end and the small end of the forming process part die surface.

[0007] Furthermore, the lower die unit includes a number of bosses for docking the lower die unit with the lower top cylinder of the hot forming equipment, upper and lower die closing guide wedge grooves, a concave model surface of the forming process part, a closing guide surface and a temperature measuring hole; a number of bosses are respectively arranged on the bottom surface of the lower die unit; a concave model surface of the forming process part is arranged inwardly on the upper surface of the lower die unit, and a closing guide surface is respectively arranged at the large end and the small end of the concave model surface of the forming process part; upper and lower die closing guide wedge grooves are respectively arranged on both sides of the lower die unit for cooperating with the upper and lower die closing guide wedge blocks, and temperature measuring holes are arranged at the positions of the upper and lower die closing guide wedge grooves.

[0008] Furthermore, the mold closing guide unit includes a clamping groove for installing the lower mold closing guide unit and the thermoforming equipment, a core mold mounting positioning boss, a lower push rod through-hole, a lower concave mold closing guide wedge surface, and a reinforcing rib plate. The end faces at both ends of the bottom flat plate structure of the mold closing guide unit are respectively provided with transverse clamping grooves, and a number of lower push rod through-holes corresponding to the boss positions are distributed on the flat plate structure; two supporting structures are respectively provided at both ends of the upper surface of the flat plate structure, and arc-shaped grooves are respectively provided on the top of the supporting structures; core mold mounting positioning bosses are respectively provided on the outer sides of the supporting structures, and reinforcing rib plates are symmetrically provided on both sides of the core mold mounting positioning bosses; lower concave mold closing guide wedge surfaces are respectively provided on the inner sides of the supporting structures for cooperating with the mold closing guide surface.

[0009] Furthermore, the core mold unit includes a lifting ring, a positioning pin hole, a core mold outer surface, a lifting ring mounting threaded hole, and a positioning groove; the core mold unit is conical, with a lifting ring provided at the large end and a lifting ring mounting threaded hole along the center axis provided on the small end face; positioning pin holes are respectively provided at both ends of one side of the core mold outer surface of the core mold unit, and positioning grooves are respectively provided at both ends of the other side.

[0010] Furthermore, the material of the hot forming mold is medium silicon molybdenum cast iron material.

[0011] A method for hot forming an ultra-long, thin-walled, conical cylindrical part using the forming die, comprising:

[0012] Preparation of conical cylindrical parts forming process parts;

[0013] According to the outer dimensions of the forming process part of the conical cylindrical part, the outer dimensions of the unfolded process part of the conical cylindrical part are calculated by using a parallel line unfolding method, and the flat plate is cut according to the outer dimensions of the unfolded process part;

[0014] The flat sheet metal is partially formed into the required arc radius of the cone cylinder by the sheet metal bending method;

[0015] The thermoforming mold is mounted on the thermoforming equipment platform and preheated. When the mold temperature stabilizes to the set temperature, the partially formed expanded workpiece is placed on the core mold unit. After heat preservation, the upper platform of the thermoforming equipment descends. After the inner surface of the upper die unit of the thermoforming mold is coupled with the outer surface of the core mold unit, the lower die unit of the thermoforming mold is coupled with the core mold unit along the mold closing guide unit under the action of the lower ejector pins on the thermoforming equipment, and is closed with the upper die unit while maintaining pressure. The thermoforming of the conical cylindrical part is completed.

[0016] The hot forming workbench is controlled to move upward, and at the same time, the lower ejector rods are controlled to move downward, so that the upper die unit and the lower die unit are opened, and the conical cylindrical part is removed from the core mold unit to perform closed forming of the conical cylindrical part.

[0017] Furthermore, the forming process of preparing the conical cylindrical part includes: preparing a cone according to the size of the conical cylindrical part, increasing the process allowance at both ends of the cone to lengthen the length of the cone body; adding ears for forming positioning at both ends of the cone, setting a positioning pin hole on one end ear, and setting a U-shaped notch on the other ear.

[0018] Furthermore, the method for hot forming ultra-long thin-walled conical cylindrical parts also includes: after placing the partially formed expansion process parts on the core mold unit, positioning is achieved by using the positioning pins at the front and rear ends of the core mold unit and the positioning pin holes and U-shaped slots on the expansion process parts.

[0019] Furthermore, the method for hot forming ultra-long thin-walled conical cylindrical parts also includes: when removing the conical cylindrical part from the core mold unit, the formed conical cylindrical part needs to be lifted and removed together with the core mold unit, and the positioning pin at the small end of the core mold unit is removed before removing the conical cylindrical part from the core mold unit.

[0020] The advantages of the present invention compared with the prior art are:

[0021] The present invention optimizes the forming process of the closed super-long conical cylinder part by rationally arranging the forming process method, obtains its expanded process parts through calculation and analysis, arranges local pre-forming before overall forming, and pre-forms the process part shape more reasonably and feasible. At the same time, the mold adopts an integrated structural design scheme: the hot forming mold completes the cone shape forming at the same time after completing one closure, that is, the closed forming of the super-long conical cylinder is completed. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the super-long tapered cylindrical part of the present invention;

[0023] Figure 2 This is a schematic diagram of the process of the super-long tapered cylindrical part of the present invention;

[0024] Figure 3 This is a schematic diagram of the process of developing the super-long tapered cylindrical part of the present invention;

[0025] Figure 4 This is a schematic diagram of the preforming process of the ultra-long tapered cylindrical part of the present invention;

[0026] Figure 5 This is a schematic diagram of the pre-forming thermoforming mold scheme of the present invention.

[0027] Figure 6 Schematic diagram of the upper die unit of the thermoforming mold of the present invention.

[0028] Figure 7 Schematic diagram of the lower die unit of the thermoforming mold of the present invention.

[0029] Figure 8 Schematic diagram of the clamping guide unit of the thermoforming mold of the present invention.

[0030] Figure 9 Schematic diagram of the core mold unit of the thermoforming mold of the present invention. DETAILED DESCRIPTION

[0031] The present invention will be described with reference to the accompanying drawings.

[0032] Example:

[0033] In view of the above shortcomings, the present invention takes a high-strength titanium alloy thin-walled, ultra-long, small-diameter conical cylindrical part as an example. The method includes the following steps:

[0034] 1. Pre-forming process solution for ultra-long conical cylindrical parts

[0035] The wall thickness of the super-long tapered cylindrical part is 2mm, the outer diameter of the large end is Φ200mm, the outer diameter of the small end is Φ144mm, and the cylinder height is 720mm; its aspect ratio is ≥6, which belongs to the super-long small diameter tapered cylinder. Figure 1 This utilizes the shortest and most efficient process flow to minimize springback deformation during the closed-body forming process during the step-by-step forming process, utilizing a minimum number of specialized forming molds for a single-step closing process. The expanded part shape is designed based on the external dimensions of the ultra-long tapered cylindrical part during the forming process.

[0036] (1) First, according to the structural characteristics of the extra-long conical cylindrical parts, the forming process parts of the conical cylindrical parts are designed. That is, the process allowance of 5mm is added at both ends of the conical cylinder to lengthen the conical cylinder to 720+5+5=730mm and the ear piece used for forming positioning is 40mm wide; and the positioning pin hole is Φ16.5 and the U-shaped notch has a center distance of 757mm. Figure 2 shown.

[0037] (2) Based on the outer dimensions of the forming process parts described above, the neutral layer of the super-long conical cylindrical part is used as the basis for its expansion calculation, and the outer dimensions of the expanded process parts of the conical cylindrical part are calculated using the parallel line expansion method; and the flat sheet is cut according to the outer dimensions of the expanded material, and the burrs are removed by grinding, and the surface quality of the polished end is Ra6.3um; see Figure 3 shown.

[0038] (3) In order to facilitate the closing of the upper and lower dies, a pre-forming process is added before hot forming, which is characterized by partially forming the sheet metal into the required arc radius of the cylinder through sheet metal bending; see Figure 4 shown.

[0039] (4) After the technical status of the thermoforming mold is checked to meet the use requirements, it is installed on the thermoforming equipment platform. After the installation is checked and qualified, the preheating program is started. When the mold temperature stabilizes at 700℃, the expanded material is placed on the core mold unit, with the pre-forming arc direction mentioned above facing downward. The positioning pins at the front and rear ends of the core mold unit are used to accurately position it before forming through the positioning pin holes and U-shaped slots on the pre-forming process. After a holding time of 10 minutes, the upper platform of the thermoforming equipment moves downward. After the inner surface of the upper die unit of the thermoforming mold is coupled with the outer surface of the core mold unit, the lower die unit of the thermoforming mold is coupled with the core mold unit along the mold guide under the action of the 5 lower ejector pins of the thermoforming equipment, and is completely closed with the upper die, and the pressure is maintained for 5 minutes. The thermoforming of the ultra-long conical cylindrical part is completed.

[0040] (5) After the mold is closed and the pressure is maintained for 5 minutes, the hot forming workbench moves upward and the five lower ejector pins move downward, and the upper and lower dies are opened; the qualified conical cylinder part is hoisted together with the core mold unit and removed. After removing the positioning pin at the small end of the core mold unit, the conical cylinder part can be smoothly removed from the core mold unit. The closed forming of the super-long conical cylinder is completed.

[0041] 2. Closed forming solution for ultra-long conical cylindrical parts

[0042] According to the dimensional characteristics of the extra-long conical cylindrical parts, welding + heat correction and other process methods are subsequently used to achieve its complete closure.

[0043] 3. Thermoforming mold solution for ultra-long conical parts

[0044] The present invention includes a thermoforming mold composed of an upper concave mold unit 2, a lower concave mold unit 3, a mold guide unit 4, a core mold unit 1 and the like. Figure 5 shown.

[0045] (1) Upper die unit of thermoforming die

[0046] According to the technical status of the ultra-long conical cylindrical part obtained through calculation and analysis, a hot forming die pressing process is adopted. According to the performance requirements of the high-strength titanium alloy TA15 material, the material is heated to 700℃±30℃, so the mold material is selected as medium silicon molybdenum cast iron. Among them, the upper die unit 2 of the hot forming die includes an upper die unit mounting platform 21, upper and lower die closing guide wedges 22, pre-positioning pin avoidance holes 23, forming process part die surface 24, upper die and core die closing guide seat 25, and temperature measuring hole 26. Figure 6 As shown. A forming process part concave mold surface 24 is provided inwardly on the lower surface of the upper die unit mounting platform 21. Upper and lower die closing guide wedges 22 are provided at the center positions of the two side surfaces of the upper die unit mounting platform 21. Temperature measuring holes 26 are provided on the upper and lower die closing guide wedges 22. Pre-positioning pin avoidance holes 23 are provided at both ends of the upper surface of the upper die unit mounting platform 21 along the central symmetric axis of the forming process part concave mold surface 24. Upper die and core mold closing guide seats 25 are provided at the large and small ends of the forming process part concave mold surface 24, respectively.

[0047] (2) Lower die unit of thermoforming die

[0048] The lower die unit and the core die unit of the thermoforming die can be coupled to form a space cone shape with uniform forming gaps that meets the requirements of the slender cone profile shape. In order to ensure that the forming gaps of the space cone shape are uniform, high-precision mold guide surfaces must be set at the mold closing positions of the upper and lower die units and the core die unit to achieve accurate positioning of the relative positions of the three and unique positions. Among them, the mold material of the lower die unit 3 of the thermoforming die is selected as medium silicon molybdenum cast iron material, including 5 bosses 31 at the docking of the lower die unit and the lower top cylinder of the thermoforming equipment, upper and lower die closed guide wedge grooves 32, the concave model surface 33 of the forming process part, the mold closing guide surface 34, and the temperature measuring hole 35. Figure 7 As shown, the bottom surface of the lower die unit 3 is provided with a plurality of bosses 31; the upper surface of the lower die unit 3 is provided with a forming process part concave model surface 33 facing inward, and the large and small ends of the forming process part concave model surface 33 are provided with mold closing guide surfaces 34 respectively; upper and lower die closing guide wedge grooves 32 are provided on both sides of the lower die unit 3 for mating with the upper and lower die closing guide wedge blocks 22, and temperature measuring holes 35 are provided at the positions of the upper and lower die closing guide wedge grooves 32.

[0049] (3) Clamping guide unit

[0050] The mold closing guide unit of the thermoforming mold is used to support and fix the core mold unit while ensuring that the upper and lower die units of the thermoforming mold move up and down along the mold closing guide surface during the mold closing process. The mold closing guide unit in the present invention serves as the mounting base of the core mold while taking into account the mold closing guide of the lower die, thereby ensuring that the final mold closing gap between the upper and lower dies and the core shaft mold is uniform and consistent, and the contour size of the super-long cone after thermoforming meets the accuracy requirement of ±0.2mm. The mold material is selected as medium silicon molybdenum cast iron material, wherein the mold closing guide unit 4 of the thermoforming mold includes a clamping groove 41 for mounting the lower mold guide unit and the thermoforming equipment, a core mold mounting positioning boss 42, a lower push rod through hole 435, a lower die closing guide wedge surface 44, and a reinforcing rib plate 45, see Figure 8 As shown, the bottom flat plate structure of the mold closing guide unit 4 has transverse compression grooves 41 disposed on both ends of the end surface, and a number of lower ejector holes 43 corresponding to the positions of the bosses 31 are distributed on the flat plate structure. Two support structures are disposed at both ends of the upper surface of the flat plate structure, and arc-shaped grooves are disposed on the top of each support structure. The outer sides of the support structures are provided with core mold mounting and positioning bosses 42, and reinforcing ribs 45 are symmetrically disposed on both sides of the core mold mounting and positioning bosses 42. The inner sides of the support structures are provided with lower concave mold closing guide wedge surfaces 44 for mating with the mold closing guide surfaces 34.

[0051] (4) Core mold unit

[0052] The core mold unit of the hot forming mold is installed and fixed on the front and rear supports of the mold closing guide unit. It is provided with positioning grooves for installation and positioning at the front and rear to ensure that the final mold closing forming gap between the inner surface of the upper and lower concave molds and the outer surface of the core shaft mold is uniform. The core mold unit is provided with pin holes for installing positioning pins, which are used to install and fix the forming position of the super-long conical cylindrical parts. The large end of the core mold unit is provided with a lifting ring structure for lifting and installation, and the small end is provided with a threaded hole for installing the lifting ring bolt. The mold material is selected as medium silicon molybdenum cast iron material, wherein the core mold unit 1 of the hot forming mold includes a lifting ring 11 of the core mold unit, a positioning pin hole 12, a core mold outer surface 13, a lifting ring installation threaded hole 14, and a positioning groove 15. Figure 9 The core mold unit 1 is tapered, with a lifting ring 11 at the large end and a threaded hole 14 for the lifting ring along the central axis at the small end. Positioning pin holes 12 are provided at both ends of one side of the core mold outer surface 13 of the core mold unit 1, and positioning grooves 15 are provided at both ends of the other side.

[0053] During the processing, the core mold unit 1 is used to install and position the unfolded process parts of the conical cylindrical parts to be processed; the lower die unit 3 is installed in the supporting structure at both ends of the mold closing guide unit 4; the core mold unit 1 is located in the inner cavity after the lower die unit 3 and the upper die unit 2 are closed, and the two ends are respectively connected by the mold closing guide.

[0054] Supported by the supporting structure at both ends of unit 4.

[0055] Parts of the present invention that are not described in detail belong to the common knowledge of those skilled in the art.

Claims

1. A thermoforming die for ultra-long thin-walled conical cylindrical parts, characterized in that: It comprises an upper concave die unit (2), a lower concave die unit (3), a mold clamping guide unit (4), and a core die unit (1); During the processing, the core mold unit (1) is used to install and position the unfolded process piece of the conical cylindrical part to be processed; the lower die unit (3) is installed in the support structures at both ends of the mold closing guide unit (4); the core mold unit (1) is located in the inner cavity after the lower die unit (3) and the upper die unit (2) are closed, and the two ends are supported by the support structures at both ends of the mold closing guide unit (4).

2. The thermoforming die for ultra-long thin-walled conical cylindrical parts according to claim 1, characterized in that: The upper die unit (2) comprises an upper die unit mounting platform (21), upper and lower die closing guide wedges (22), a pre-positioning pin avoidance hole (23), a forming process part die surface (24), an upper die and core die closing guide seat (25), and a temperature measuring hole (26); the forming process part die surface (24) is arranged inwardly on the lower surface of the upper die unit mounting platform (21); the upper and lower die closing guide wedges (22) are respectively arranged at the center positions of the two side surfaces of the upper die unit mounting platform (21); and the temperature measuring holes (26) are respectively arranged on the upper and lower die closing guide wedges (22); the pre-positioning pin avoidance holes (23) are respectively arranged at both ends of the upper surface of the upper die unit mounting platform (21) along the central symmetry axis of the forming process part die surface (24); and the upper die and core die closing guide seats (25) are respectively arranged at the large end and the small end of the forming process part die surface (24).

3. The thermoforming die for ultra-long thin-walled conical cylindrical parts according to claim 2, characterized in that: The lower die unit (3) comprises a plurality of bosses (31) for docking the lower die unit with the lower top cylinder of the thermoforming equipment, upper and lower die closing guide wedge grooves (32), a forming process part concave model surface (33), a closing guide surface (34) and a temperature measuring hole (35); a plurality of bosses (31) are respectively arranged on the bottom surface of the lower die unit (3); a forming process part concave model surface (33) is arranged inwardly on the upper surface of the lower die unit (3), and a closing guide surface (34) is respectively arranged at the large end and the small end of the forming process part concave model surface (33); upper and lower die closing guide wedge grooves (32) are respectively arranged on both sides of the lower die unit (3) for cooperating with the upper and lower die closing guide wedge blocks (22), and a temperature measuring hole (35) is arranged at the position of the upper and lower die closing guide wedge grooves (32).

4. The thermoforming die for ultra-long thin-walled conical cylindrical parts according to claim 3, characterized in that: The mold closing guide unit (4) comprises a clamping groove (41) for installing the lower mold closing guide unit and the thermoforming equipment, a core mold mounting positioning boss (42), a lower push rod through hole (43), a lower concave mold closing guide wedge surface (44), and a reinforcing rib plate (45). The end surfaces of the two ends of the bottom flat plate structure of the mold closing guide unit (4) are respectively provided with a transverse clamping groove (41), and a plurality of lower push rod through holes (43) corresponding to the positions of the bosses (31) are distributed on the flat plate structure; two support structures are respectively provided at both ends of the upper surface of the flat plate structure, and arc grooves are respectively provided on the top of the support structures; the outer side of the support structure is respectively provided with a core mold mounting positioning boss (42), and reinforcing rib plates (45) are symmetrically provided on both sides of the core mold mounting positioning boss (42); the inner side of the support structure is respectively provided with a lower concave mold closing guide wedge surface (44) for matching with the mold closing guide surface (34).

5. The thermoforming die for ultra-long thin-walled conical cylindrical parts according to claim 4, characterized in that: The core mold unit (1) comprises a lifting ring (11), a positioning pin hole (12), a core mold outer surface (13), a lifting ring mounting threaded hole (14), and a positioning groove (15); the core mold unit (1) is conical, with a lifting ring (11) provided at the large end and a lifting ring mounting threaded hole (14) along the central axis provided on the small end surface; the positioning pin holes (12) are respectively provided at two ends of one side of the core mold outer surface (13) of the core mold unit (1), and the positioning grooves (15) are respectively provided at two ends of the other side.

6. The thermoforming die for ultra-long thin-walled conical cylindrical parts according to claim 1, characterized in that: The material of the hot forming mold is medium silicon molybdenum cast iron material.

7. A method for thermoforming an ultra-long, thin-walled, conical cylindrical part using the forming die according to any one of claims 1 to 6, characterized in that: include: Preparation of conical cylindrical parts forming process parts; According to the outer dimensions of the forming process part of the conical cylindrical part, the outer dimensions of the unfolded process part of the conical cylindrical part are calculated by using a parallel line unfolding method, and the flat plate is cut according to the outer dimensions of the unfolded process part; The flat sheet metal is partially formed into the required arc radius of the cone cylinder by the sheet metal bending method; The thermoforming mold is mounted on the thermoforming equipment platform and preheated. When the mold temperature stabilizes to the set temperature, the partially formed expanded workpiece is placed on the core mold unit (1); after heat preservation, the upper platform of the thermoforming equipment descends, and after the inner surface of the upper die unit (2) of the thermoforming mold is coupled with the outer surface of the core mold unit (1), the lower die unit (3) of the thermoforming mold is coupled with the core mold unit (1) along the mold guide unit (4) under the action of the lower ejector rods on the thermoforming equipment, and is closed with the upper die unit (2) and pressure maintained; thus completing the thermoforming of the conical cylindrical part; The hot forming workbench is controlled to move upward, and at the same time, each lower ejector rod is controlled to move downward, so that the upper die unit (2) and the lower die unit (3) are opened, and the conical cylindrical part is removed from the core die unit (1) to perform closed forming of the conical cylindrical part.

8. The method for hot forming an ultra-long thin-walled conical cylindrical part according to claim 7, characterized in that: The forming process of preparing a conical cylindrical part includes: preparing a conical cylinder according to the size of the conical cylindrical part, increasing process allowances at both ends of the conical cylinder to lengthen the length of the conical cylinder; adding ears for forming and positioning at both ends of the conical cylinder, providing a positioning pin hole on one end ear and providing a U-shaped notch on the other ear.

9. The method for hot forming an ultra-long thin-walled conical cylindrical part according to claim 8, characterized in that: Also includes: After the partially formed expansion process piece is placed on the core mold unit (1), positioning is achieved by using the positioning pins at the front and rear ends of the core mold unit (1) and the positioning pin holes and U-shaped slots on the expansion process piece.

10. The method for hot forming an ultra-long thin-walled conical cylindrical part according to claim 9, characterized in that: Also includes: When removing the conical cylindrical part from the core mold unit (1), it is necessary to lift the formed conical cylindrical part together with the core mold unit (1) and remove the positioning pin at the small end of the core mold unit (1), and then remove the conical cylindrical part from the core mold unit (1).

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