An outer spinning method for a cylindrical part with an in-line step

Abstract

This invention discloses a method for external spinning of cylindrical parts with internal steps, belonging to the field of spinning forming. The method involves designing a dedicated spinning mandrel with concave steps, a spinning blank with convex steps that matches the mandrel, and a tail cap to fix the spinning blank. Through the selection and heat treatment of the spinning blank, the spinning blank, mandrel, and tail cap are processed. The spinning blank is then clamped on a spinning machine, and the straight cylindrical section of the cylinder is spun. After spinning, it undergoes heat treatment and annealing. A series of processes are then performed, including turning the outer diameter of the inner platform stage and removing the sprue. This method achieves external spinning of cylindrical parts with internal steps, solving the problems of increased weld seams, low processing efficiency, and difficulty in guaranteeing quality caused by the need to process and weld the inner platform stage and straight cylindrical section as separate parts in existing external spinning methods for cylindrical parts with internal steps.

Description

Technical Field

[0001] This invention belongs to the field of spinning forming, and specifically relates to a method for external spinning forming of cylindrical parts with internal steps. Background Technology

[0002] Solid rocket motor combustion chamber shell typically consists of a front connector 1, a cylinder 3, and a rear connector 4, such as... Figure 1 As shown. The cylinder 3 is a thin-walled spun part, generally made of ultra-high strength steel, and is formed by high-pressure spun forming; the front and rear connecting parts are generally machined; and then connected by welding.

[0003] For the spinning of the cylinder body 3, external spinning equipment is generally used. If the cylinder body has internal steps, it is difficult to support the internal steps when using external spinning equipment. Therefore, the inner platform stage 32 and the straight cylinder section 31 of the cylinder body 3 are usually processed as two separate parts, and then connected by welding or other methods. This method will increase the number of welds on the cylinder body 3, resulting in one weld 2 on each side of the inner platform stage 32. Especially for combustion chamber shells with multiple internal steps, each additional inner platform stage 32 will add two welds, increasing the difficulty of welding the combustion chamber shell, increasing the processing cycle and cost, and making it more difficult to control the coaxiality of the shell, thus increasing the difficulty of subsequent heat treatment.

[0004] To avoid increasing weld seams, specialized internal spinning equipment can be used for cylindrical body spinning. However, due to the high specialization, scarcity, and cost of such equipment, its widespread use is difficult. Therefore, it is worthwhile to study how to use more versatile external spinning equipment to achieve external spinning of cylindrical parts with internal steps. Summary of the Invention

[0005] The technical problem to be solved:

[0006] To overcome the shortcomings of existing technologies, this invention provides a method for external spinning of cylindrical parts with internal steps. By designing a special spinning mandrel with concave internal steps, and a spinning blank with convex internal steps that matches the spinning mandrel, and in conjunction with appropriate process methods, the external spinning of cylindrical parts with internal steps can be achieved. This solves the problem of increased weld seams caused by the need to process and weld the inner platform stage and the straight cylinder section as separate parts in existing external spinning methods for cylindrical parts with internal steps.

[0007] The technical solution of the present invention is: a method for external spinning of a cylindrical part with an inner step, comprising the following steps:

[0008] Step 1. Based on the dimensions of the finished cylindrical part with an inner platform, design a spinning mandrel with an inner concave step, design a spinning blank with an inner convex step that matches the spinning mandrel, and design a special tail tip based on the spinning mandrel and the spinning blank.

[0009] The spinning mandrel is a stepped shaft, which is provided in sequence with a mandrel mounting section, a mandrel straight cylinder section and a mandrel inner platform stage;

[0010] The spinning blank is a cylindrical part, which is provided in sequence with a straight cylindrical section, an inner platform section and a tail section.

[0011] Step 2. Soften and heat treat the spun blank;

[0012] Step 3. Process the blank after heat treatment in Step 2 to obtain the spinning blank designed in Step 1; complete the spinning mandrel and tail top designed in Step 1;

[0013] Step 4. Assemble the spinning mandrel, spinning blank, and tail tip on the external spinning equipment; fit the straight section of the cylinder onto the straight section of the mandrel, with the inner platform stage of the cylinder mating with the inner platform stage of the mandrel, and the inner end face of the tail tip section of the cylinder abutting against the outer end face of the inner platform stage of the mandrel; fix the spinning blank by pressing the outer end of the inner platform stage of the mandrel and the outer end face of the tail tip section of the cylinder with the tail tip;

[0014] Step 5. Use a forward spin method to spin the straight section of the cylinder to the finished size of that section, without spinning the inner middle section and the tail section of the cylinder, to obtain a spun semi-finished product;

[0015] Step 6. Heat-treat and anneal the spun semi-finished product;

[0016] Step 7. Turn the outer diameter of the inner step of the spun semi-finished product after step 6 so that it is flush with the outer diameter of the straight cylinder section after step 5. Then turn and remove the tail section of the cylinder and the process material head at the end away from the tail section to obtain the finished cylindrical part with inner step.

[0017] A further technical solution of the present invention is as follows: the core mold mounting section is designed to cooperate with the external spinning equipment for installing the spinning core mold; the diameter of the core mold straight section is 0.1-0.2 mm smaller than the inner diameter of the finished cylindrical section, and the axial length of the core mold straight section is 200-300 mm greater than the length of the finished cylindrical section; the diameter of the core mold inner platform stage is smaller than the inner diameter of the finished cylindrical step, and the axial length of the core mold inner platform stage is 20-30 mm greater than the length of the finished cylindrical step.

[0018] A further technical solution of the present invention is: the center position of the outer end face of the inner platform stage of the core mold is provided with an inner concave hole along the axial direction of the spinning core mold, for coaxial docking and cooperation with the tail top.

[0019] A further technical solution of the present invention is as follows: the inner diameter of the straight cylindrical section of the cylinder is 0.1-0.2 mm larger than the diameter of the straight cylindrical section of the mandrel; the outer diameter of the straight cylindrical section of the cylinder is calculated based on the thickness of the finished straight cylindrical section of the cylindrical part and the spinning thinning rate; the axial length of the straight cylindrical section of the cylinder is calculated based on its thickness before spinning, the spinning thinning rate, and the length of the finished straight cylindrical section of the cylindrical part; the step surface and dimensions of the inner platform stage of the cylinder are consistent with the inner step of the finished cylindrical part; a 10 mm straight section is added to each side of the step of the inner platform stage of the cylinder for transition to both sides; the outer diameter of the inner platform stage of the cylinder is 2-3 mm larger than the outer diameter of the finished cylindrical part, and transitions with the outer diameter of the straight cylindrical section of the cylinder at a 20° slope; the outer diameter of the tail section of the cylinder is the same as the outer diameter of the inner platform stage of the cylinder, its inner diameter is 20-30 mm smaller than the diameter of the inner platform stage of the mandrel, and its axial length is 10 mm.

[0020] A further technical solution of the present invention is as follows: In step 3, the spinning blank is an integral structure or a separate welded assembly structure; the integral structure is: the blank processed in step 2 is machined into a straight cylindrical section, an inner platform stage, and a tail section; the separate welded assembly structure is: the blank processed in step 2 is machined into a straight cylindrical section and an inner platform stage, and the tail section is made of a separate annular plate, which is welded and fixed to the inner platform stage.

[0021] A further technical solution of the present invention is as follows: one end of the tail top is a working end, used to clamp the spinning core mold and the spinning blank, and the other end is a clamping end, used for installation and connection with the external spinning equipment; the working end of the tail top is a stepped shaft, with an outwardly protruding boss at its center, the boss and the peripheral edge forming a stepped surface; the boss is embedded in the concave hole at the outer end of the inner platform stage of the core mold, and the end face of the boss contacts the bottom surface of the concave hole; the stepped surface abuts against the outer end face of the tail top section of the cylinder.

[0022] A further technical solution of the present invention is: the blank for the spinning blank in step 2 is selected from tubular material or forged cylindrical blank.

[0023] A further technical solution of the present invention is: the softening heat treatment in step 2 is spheroidizing annealing, and the spheroidizing annealing temperature is determined according to the material of the spinning blank.

[0024] Beneficial effects

[0025] The beneficial effects of this invention are as follows: This invention provides an external spinning processing method for cylindrical parts with internal steps. Based on the product's structural dimensions, a spinning mandrel and a spinning blank with internal steps are designed. A dedicated tail jack is designed to clamp the spinning mandrel onto a general-purpose external spinning equipment. The spinning blank is coaxially fitted onto the spinning mandrel, ensuring the internal steps of both are aligned. The dedicated tail jack fixes the spinning blank, thus achieving the spinning processing of the straight cylindrical section of the spinning blank. Since the internal steps, identical to those of the product, are pre-machined in the spinning blank, only the outer diameter of the inner platform stage needs to be machined to the outer diameter of the straight cylindrical section after spinning to complete the inner platform stage processing. The tail jack section, used for clamping, serves to fix the spinning blank during the spinning process and can be removed during the machining of the outer diameter of the inner platform stage. Simultaneously, the process material head at the other end is machined to ensure the axial length of the product.

[0026] This method processes cylindrical parts with internal steps that require spin forming as a single structure. Compared to existing technologies that process the straight cylindrical section and the inner step section as independent parts and then weld them together, this method reduces the number of welds. When used for spin forming of straight cylindrical parts with internal steps, such as solid rocket motor casings, it effectively reduces the number of welds, improves processing efficiency, and significantly enhances overall coaxiality. It is also suitable for spin forming of cylindrical parts with internal steps made of alloy structural steel and ultra-high strength steel in the aerospace and petroleum industries. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the combustion chamber shell structure of a solid rocket motor;

[0028] Figure 2 This is a flowchart of the process method of the present invention;

[0029] Figure 3 This is a schematic diagram of the spinning process of the present invention.

[0030] Figure 4 This is a schematic diagram of the spinning core die structure;

[0031] Figure 5 This is a schematic diagram of the structure of the spinning blank;

[0032] Figure 6 This is a schematic diagram of the finished cylindrical part with an internal step after the spinning blank has been processed.

[0033] Figure 7 This is a schematic diagram of a solid rocket engine combustion chamber shell structure manufactured using the process method of the present invention in an embodiment.

[0034] Explanation of reference numerals in the attached drawings: 1. Front connector, 2. Weld, 3. Cylinder, 31. Straight cylinder section, 32. Inner platform stage, 4. Rear connector, 5. Spinning mandrel, 51. Mandrel mounting section, 52. Straight cylinder section of mandrel, 53. Inner platform stage of mandrel, 531. Concave hole, 6. Spinning blank, 61. Straight cylinder section of cylinder, 62. Inner platform stage of cylinder, 63. Tail top section of cylinder, 7. Tail top, 71. Boss, 72. Stepped surface, 8. Spinning wheel, 9. Finished cylindrical part with inner step, 91. Straight cylinder section of finished cylindrical part, 92. Inner step of finished cylindrical part, V. indicates spinning direction. Detailed Implementation

[0035] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0036] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0037] This embodiment uses processing Figure 7 Taking the cylindrical portion of a solid rocket motor combustion chamber shell as an example, this invention details the external spinning method for machining cylindrical parts with internal steps. If existing external spinning processes are used... Figure 7 The intermediate cylindrical section shown has three inner steps, requiring it to be divided into four straight cylindrical sections and three inner step sections for independent processing and welding. Welds would exist on both sides of the inner steps, resulting in six welds in the cylindrical section alone (excluding the welds of the front and rear connecting parts at both ends). However, by using the processing method of this invention, the cylindrical section can be divided into four sections: three sections with inner steps and one straight cylindrical section. After welding, the cylindrical section has only three welds, reducing the number of welds, improving shell processing efficiency, and ensuring the overall coaxiality requirement of the shell.

[0038] The following is about processing Figure 7 The external spinning processing method of the present invention is introduced using a cylindrical part with an inner step as an example. The process flow diagram is as follows: Figure 2As shown. The product information for the finished cylindrical part 9 with internal steps is as follows: the material is D406A ultra-high strength steel, the thin-wall dimension of the straight section 91 of the finished cylindrical part is φ500×t3mm (outer diameter×wall thickness), and the length of the straight section 91 of the finished cylindrical part is 500mm.

[0039] Step 1. Based on the dimensions of the finished cylindrical part 9 with inner platform, design the spinning core mold 5, spinning blank 6, and tail top 7.

[0040] Specifically, such as Figure 4 As shown, the spinning mandrel 5 is a concentric stepped shaft, with a mandrel mounting section 51, a mandrel straight cylinder section 52, and a mandrel inner platform section 53 arranged sequentially from left to right. The dimensions of the mandrel mounting section 51 are designed to match the external spinning equipment and are used to install the spinning mandrel 5.

[0041] The diameter of the mandrel straight section 52 is 0.1 to 0.2 mm smaller than the inner diameter of the finished cylindrical section 91. In this embodiment, the diameter of the mandrel straight section 52 is φ493.8 mm, and the axial length of the mandrel straight section 52 is 200 to 300 mm greater than the length of the finished cylindrical section 91 to ensure the spinning stroke. In this embodiment, this dimension is 300 mm.

[0042] The diameter of the inner platform stage 53 of the mandrel is smaller than the inner diameter of the inner step 92 of the finished cylindrical part, and the axial length of the inner platform stage 53 is 20-30 mm longer than the length of the inner step 92 of the finished cylindrical part, to ensure that the two do not interfere with each other during assembly. In this embodiment, the axial length of the inner platform stage 53 of the mandrel is 20 mm longer than the length of the inner step of the finished cylindrical part. A concave hole 531 is provided at the center of the outer end face of the inner platform stage 53 along the axial direction of the spinning mandrel, for coaxial docking with the top end of the tail fin 7.

[0043] like Figure 5 As shown, the spinning blank 6 is a cylindrical part, which is provided from left to right as a straight cylindrical section 61, an inner platform section 62, and a tail section 63.

[0044] The inner diameter of the cylindrical section 61 is 0.1–0.2 mm larger than the diameter of the mandrel section 52. In this embodiment, the inner diameter of the cylindrical section 61 is φ494 mm. The outer diameter of the cylindrical section 61 is calculated based on the thickness of the finished cylindrical section 91 and the spinning thinning rate. The formula for calculating the outer diameter of the cylindrical section 61 is:

[0045]

[0046] In the formula: D is the outer diameter of the straight section 61 of the cylinder, d is the inner diameter of the straight section 61 of the cylinder, which is φ494mm; t is the thickness of the finished straight section 91 of the cylindrical part, which is 3mm; f is the thinning rate.

[0047] In this embodiment, the thinning rate f is determined to be 75% based on the material, process route and spinning equipment, and the outer diameter of the straight section 61 of the cylinder is calculated to be φ518mm according to formula (1).

[0048] The axial length of the straight cylindrical section 61 is calculated based on its thickness before spinning, the spinning thinning rate, and the length of the finished straight cylindrical section 91. The specific calculation method is as follows:

[0049]

[0050] In the formula: L is the length of the straight cylindrical section 61; t is the thickness of the finished straight cylindrical section 91 of the cylindrical part, which is 3mm; l is the length of the finished straight cylindrical section 91 of the cylindrical part, which is 500mm; D is the outer diameter of the straight cylindrical section 61 of the cylindrical part, which is φ518mm; d is the inner diameter of the straight cylindrical section 61 of the cylindrical part, which is φ494mm; e is the process allowance, which is 200mm in this embodiment. The excess process allowance will be removed as a material head in the final processing step. According to formula (2), the length of the straight cylindrical section 61 of the cylindrical part is calculated to be 175mm.

[0051] The step shape and dimensions of the inner platform stage 62 of the cylinder are consistent with the inner step of the finished cylindrical part. A 10mm straight section is added to each side of the step of the inner platform stage 62 of the cylinder for transition to both sides.

[0052] The outer diameter of the inner platform stage 62 of the cylinder is 2-3 mm larger than the outer diameter of the finished cylindrical part 9. In this embodiment, the outer diameter of the inner platform stage 62 of the cylinder is φ502 mm. The outer diameter of the inner platform stage 62 of the cylinder and the outer diameter of the straight section 61 of the cylinder form a 20° slope transition, which facilitates subsequent processing.

[0053] The outer diameter of the tail section 63 of the cylinder is the same as the outer diameter of the inner platform stage 62 of the cylinder. Its inner diameter is 20-30mm smaller than the diameter of the inner platform stage 53 of the core mold. Its axial length is 10mm. In this embodiment, the inner diameter of the tail section 63 of the cylinder is 30mm smaller than the diameter of the inner platform stage 53 of the core mold, and is used to be stuck on the outer end face of the inner platform stage 53 of the core mold.

[0054] The tail tip 7 is used to secure the spinning blank 6, and its top end dimensions are designed to match the spinning mandrel 5 and the spinning blank 6. One end of the tail tip 7 is the working end, which serves as the top end to hold the spinning mandrel 5 and the spinning blank 6 in place; the other end is the clamping end, used for installation and connection with external spinning equipment. The top end of the tail tip 7 is a stepped shaft, and its center has a cylindrical boss 71 that protrudes outward along its axial direction. The boss 71 and the peripheral edge of this end of the tail tip 7 form a stepped surface 72.

[0055] The design of the spinning mandrel 5, the spinning blank 6, and the tail tip 7 ensures the following fit during subsequent spinning: the spinning blank 6 is coaxially fitted into the spinning mandrel 5; the inner platform stage 62 of the spinning blank 6 mates with the inner platform stage 53 of the spinning mandrel 5; the tail tip 63 of the spinning blank 6 is held against the outer end face of the inner platform stage 53, and the inner wall of the tail tip 63 contacts the outer end face of the inner platform stage 53. The boss 71 at the top of the tail tip 7 is embedded in the concave hole 531 at the outer end of the inner platform stage 53, and the end face of the boss 71 contacts the bottom surface of the concave hole 531. At the same time, the stepped surface 72 abuts against the outer end face of the tail tip 63. The tail tip 63 is sandwiched between the spinning mandrel 5 and the tail tip 7, fixing the position of the spinning blank 6.

[0056] Step 2. Selection of blank for spinning blank 6 and pretreatment before machining. The blank can be a tube material directly cut or a cylindrical material forged. In this embodiment, the blank is a D406A seamless steel pipe as the blank for spinning blank 6.

[0057] The selected billet is subjected to spheroidizing annealing: the billet is placed in a heating furnace and heated to 860℃±10℃ and held for 4 hours, then cooled to 720℃±10℃ and held for 6 hours, and then cooled in the furnace to below 600℃ and air cooled.

[0058] Step 3. Process the blank after heat treatment in Step 2 to obtain the spinning blank 6 designed in Step 1. And complete the spinning mandrel 5 and tail top 7 designed in Step 1.

[0059] The blank is machined by CNC turning to produce the straight cylindrical section 61, the inner platform section 62, and the tail section 63 of the spun blank 6. The wall thickness of the straight cylindrical section 61 is 12mm, and the wall thickness difference is guaranteed to be no more than 0.08mm.

[0060] In another embodiment of the present invention, the tail section 63 of the spun blank 6 is achieved by welding. That is, the blank after heat treatment in step 2 is turned to produce only the straight cylindrical section 61 and the inner platform stage 62 of the spun blank 6. The tail section 63 is made of a ring-shaped bottom plate of a corresponding size, which is coaxially welded and fixed to the inner platform stage 62 of the cylinder.

[0061] Step 4. Assemble the spinning mandrel 5, spinning blank 6, and tail tip 7 on the external spinning equipment.

[0062] like Figure 3As shown, the spinning mandrel 5 is placed horizontally, and its mandrel mounting section 51 is installed on the external spinning equipment. The spinning blank 6 is coaxially fitted onto the spinning mandrel 5, so that the straight cylindrical section 61 of the cylinder is fitted onto the straight cylindrical section 52 of the mandrel. The inner platform stage 62 of the cylinder mates with the inner platform stage 53 of the mandrel. The inner end face of the tail top section 63 of the cylinder contacts the outer end face of the inner platform stage 53 of the mandrel. The tail top 7 is used to press against the outer end of the inner platform stage 53 of the mandrel and the outer end face of the tail top section 63 of the cylinder, thus fixing the spinning blank 6.

[0063] Step 5. Perform spinning processing on the straight cylindrical section 61 of the spun blank 6.

[0064] Using a three-wheel CNC high-power spinning machine, the spinning wheel has 8 edges Figure 3 The V-shaped motion shown reduces the wall thickness of the straight cylindrical section 61 from 12mm to 3mm ± 0.10mm. This process only spins the straight cylindrical section 61, omitting the inner platform stage 62 and the tail section 63. Therefore, the inner platform stage 62 is avoided during spinning. After step 5, a spun semi-finished product is obtained.

[0065] Step 6. Heat-treat and anneal the spun semi-finished product. Annealing temperature and time requirements: 400℃±10℃, hold for 240 minutes.

[0066] Step 7. For the spun semi-finished product from Step 6, machine the outer diameter of the inner platform stage 62 of the cylinder to make it flush with the outer diameter of the spun straight cylinder section. Then, machine away the tail section 63 of the cylinder and the process material head at the end furthest from the tail section 63 to obtain... Figure 6 The cylindrical part 9 shown has an internal step. When machining the blank, the axial length of the straight cylindrical section 91 of the finished cylindrical part must be ensured.

[0067] Processing Figure 7 When manufacturing the solid rocket motor combustion chamber shell, the three cylindrical finished products 9 processed through the above steps and a straight section are sequentially coaxially welded together to form a total of three weld seams 2. The front connecting part 1 and the rear connecting part 4 are welded at both ends, so that the entire combustion chamber shell finished product has only five weld seams 2, which reduces the number of weld seams, improves the shell processing efficiency, effectively ensures the coaxiality requirements of the overall shell welding, and also helps to reduce the difficulty of the shell's subsequent heat treatment.

[0068] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A method for external spinning of a cylindrical part with an inner step, characterized in that, Includes the following steps: Step 1. Based on the dimensions of the finished cylindrical part with an inner platform, design a spinning mandrel with an inner concave step, design a spinning blank with an inner convex step that matches the spinning mandrel, and design a special tail tip based on the spinning mandrel and the spinning blank. The spinning mandrel is a stepped shaft, which is provided in sequence with a mandrel mounting section, a mandrel straight cylinder section and a mandrel inner platform stage; The spinning blank is a cylindrical part, which is provided in sequence with a straight cylindrical section, an inner platform section and a tail section. Step 2. Soften and heat treat the spun blank; Step 3. Process the blank after heat treatment in Step 2 to obtain the spinning blank designed in Step 1; complete the spinning mandrel and tail top designed in Step 1; Step 4. Assemble the spinning mandrel, spinning blank, and tail tip on the external spinning equipment; The straight section of the cylinder is fitted onto the straight section of the core mold. The inner platform stage of the cylinder mates with the inner platform stage of the core mold, and the inner end face of the tail top section of the cylinder abuts against the outer end face of the inner platform stage of the core mold. The spinning blank is fixed by pressing the outer end of the inner platform stage of the core mold and the outer end face of the tail top section of the cylinder against the tail top. Step 5. Use a forward spin method to spin the straight section of the cylinder to the finished size of that section, without spinning the inner platform section and the tail section of the cylinder, to obtain a spun semi-finished product; Step 6. Heat-treat and anneal the spun semi-finished product; Step 7. Turn the outer diameter of the inner step of the spun semi-finished product after step 6 to make it flush with the outer diameter of the straight section after step 5, and turn to remove the tail section of the cylinder and the process material head at the end away from the tail section to obtain the finished cylindrical part with inner step. The core mold mounting section is designed to work in conjunction with the external spinning equipment to mount the spinning core mold. The diameter of the core mold's straight cylindrical section is 0.1–0.2 mm smaller than the inner diameter of the finished cylindrical section, and its axial length is 200–300 mm longer than the finished cylindrical section. The diameter of the core mold's inner platform stage is smaller than the inner diameter of the finished cylindrical step, and its axial length is 20–30 mm longer than the finished cylindrical step. A recessed hole is provided at the center of the outer end face of the core mold's inner platform stage along the spinning core mold's axial direction for coaxial docking with the tailstock. The inner diameter of the cylindrical body's straight cylindrical section is 0.1–0.2 mm larger than the diameter of the core mold's straight cylindrical section. The outer diameter of the cylindrical section is calculated based on the thickness of the straight cylindrical section of the finished cylindrical part and the spinning thinning rate. The axial length of the straight cylindrical section is calculated based on its thickness before spinning, the spinning thinning rate, and the length of the straight cylindrical section of the finished cylindrical part. The step surface and dimensions of the inner platform stage of the cylindrical part are consistent with the inner step of the finished cylindrical part. A 10mm straight section is added to each side of the step of the inner platform stage of the cylindrical part for transition to both sides. The outer diameter of the inner platform stage of the cylindrical part is 2-3mm larger than the outer diameter of the finished cylindrical part and transitions with the outer diameter of the straight cylindrical section of the cylindrical part at a 20° slope. The outer diameter of the tail section of the cylindrical part is the same as the outer diameter of the inner platform stage of the cylindrical part, and its inner diameter is 20-30mm smaller than the diameter of the inner platform stage of the core mold. Its axial length is 10mm.

2. The method according to claim 1, characterized in that, In step 3, the spinning blank is either an integral structure or a separate welded assembly structure; the integral structure is: the blank processed in step 2 is machined into a straight cylindrical section, an inner platform stage, and a tail section; the separate welded assembly structure is: the blank processed in step 2 is machined into a straight cylindrical section and an inner platform stage, and the tail section is made of a separate annular plate, which is welded and fixed to the inner platform stage.

3. The method according to claim 2, characterized in that, One end of the tail is a working end, used to clamp the spinning core mold and the spinning blank, and the other end is a clamping end, used for installation and connection with the external spinning equipment; the working end of the tail is a stepped shaft, with a protruding boss at its center, and the boss and the peripheral edge form a stepped surface; the boss is embedded in the concave hole at the outer end of the inner stage of the core mold, and the end face of the boss is in contact with the bottom surface of the concave hole; the stepped surface abuts against the outer end face of the tail section of the cylinder.

4. The method according to claim 1, characterized in that, The blank for the spinning blank in step 2 is selected from tubular material or forged cylindrical blank.

5. The method according to claim 1, characterized in that, The softening heat treatment described in step 2 is spheroidizing annealing, and the spheroidizing annealing temperature is determined according to the material of the spinning blank.

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