A method of forming a variable cross-section tubular part with a boss

Abstract

The application relates to a forming method of a variable cross-section cylindrical part with an inner boss, belongs to the technical field of diffusion connection forming, and solves the problems that, in the prior art, a casting and machining combined mode is used for forming, machining allowance is large, and material utilization rate is low; an additive manufacturing and machining combined mode is used for forming, overall machining time is long, and machining efficiency is low. The forming method of the variable cross-section cylindrical part with the inner boss comprises the following steps: A, preforming; B, mold closing; C, diffusion connection forming; and D, completing diffusion connection forming and demolding. The forming method adopts a rigid mode for diffusion connection of the first boss and the second boss, and adopts a flexible mode for diffusion connection of the first cylindrical section, the second cylindrical section and the third cylindrical section, so that the close connection of each part of the variable cross-section cylindrical part with the inner boss is ensured, and the diffusion connection quality is ensured.

Description

Technical Field

[0001] This invention belongs to the field of metal diffusion bonding forming technology, and in particular relates to a forming method for a cylindrical part with an internal boss and variable cross-section. Background Technology

[0002] In the aerospace field, there is a need to manufacture cylindrical parts with variable cross-sections and internal bosses. For example, when manufacturing the cylindrical outer shell of rockets or aircraft, solid bosses are also needed on the inner wall to reinforce the inner wall of that area and facilitate the subsequent installation of other components on the bosses.

[0003] There are currently two solutions for forming such components: one is a combination of casting and machining, and the other is a combination of additive manufacturing and machining.

[0004] Forming by combining casting and machining has several drawbacks. Casting is prone to stress concentration, which can lead to cracking. Machining also results in large allowances and low material utilization. Forming by combining additive manufacturing and machining, on the other hand, has problems such as long overall processing time and low processing efficiency.

[0005] Therefore, there is an urgent need for a forming method for cylindrical parts with internal bosses and variable cross-sections. This method should employ diffusion bonding technology to replace the combination of casting and machining or additive manufacturing and machining, given the large demand for such products. This would enable high-efficiency and low-cost forming of cylindrical components with internal bosses and variable cross-sections. Summary of the Invention

[0006] Based on the above analysis, the present invention aims to provide a forming method for a cylindrical part with an internal boss and variable cross-section, solving the problems of existing technologies that use a combination of casting and machining for forming, resulting in large machining allowances and low material utilization; and that use a combination of additive manufacturing and machining for forming, resulting in long overall processing time and low processing efficiency.

[0007] The objective of this invention is mainly achieved through the following technical solutions:

[0008] A method for forming a cylindrical component with an internal boss and variable cross-section includes the following steps:

[0009] A. Pre-forming;

[0010] B. Mold closing;

[0011] C. Diffusion bonding and shaping;

[0012] D. Complete the diffusion bonding and demolding.

[0013] Furthermore, step A, preforming, includes: disassembling the cylindrical part into process parts.

[0014] Furthermore, the process component includes a first cylinder, a second cylinder, a third cylinder, a first boss, and a second boss.

[0015] Furthermore, the first boss and the second boss are single bosses.

[0016] Furthermore, step A, preforming, also includes: making a first cylinder, a second cylinder, and a third cylinder.

[0017] Furthermore, step A, preforming, also includes: fabricating the first boss and the second boss.

[0018] Furthermore, step A, preforming, also includes cleaning the workpiece.

[0019] Furthermore, the cleaning process includes: polishing the diffusion surface of the process component and performing alkaline pickling on all process components.

[0020] Furthermore, after step D, completing the diffusion connection forming and demolding, the method further includes the step of machining the cylindrical part and completing the forming.

[0021] Furthermore, the machining of the cylindrical part and the completion of its forming includes: machining the outer diameter of the cylindrical part.

[0022] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0023] (1) The forming method of the present invention uses a rigid method to diffuse the connection between the first boss and the second boss, and a flexible method to diffuse the connection between the first cylindrical section, the second cylindrical section and the third cylindrical section. Both methods can ensure the tight connection of each part of the cylindrical part with the inner boss and ensure the quality of the diffusion connection.

[0024] (2) The core mold of the forming mold of the present invention pushes the intermediate mold to the outer mold, providing clamping force for the intermediate mold. The cylindrical part can be clamped and fixed by the outer mold, the intermediate mold and the limiting ring, and diffused and formed in the forming furnace by relying on the outer mold, the intermediate mold and the limiting ring.

[0025] (3) The intermediate mold of the forming mold of the present invention includes a first limiting block and a second limiting block. The second limiting block includes two connecting end faces, which are parallel and parallel to the central axis. When demolding, the second limiting block is first pushed radially toward the central axis and then taken out axially. Then the first limiting block can be demolded, which facilitates the demolding operation.

[0026] (4) The compensation module of the forming mold of the present invention is a variable compensation module; the compensation module can be filled and released during diffusion connection, and the thickness of the compensation module can be adjusted to compensate for the gap between the intermediate mold and the cylindrical part, so that the intermediate mold maintains the same thrust on the first cylindrical section, the second cylindrical section, the third cylindrical section, the first boss and the second boss; the first air bag and the second air bag enable the compensation module to be disassembled, which facilitates the mold closing and demolding of diffusion connection;

[0027] (5) The outer wall of the cylindrical section of the core mold of the forming mold of the present invention is provided with external threads, and the inner wall of the central hole is provided with internal threads. The core mold can rotate and descend along the internal threads by its own weight, and the top cover can rotate around the central axis on the outer mold. When demolding, the top cover is rotated, and the internal threads decompose the rotational force into the lifting force of the core mold, so that the core mold is lifted and detached from the intermediate mold, which facilitates the demolding of the core mold.

[0028] (6) The drag-reducing groove of the forming mold of the present invention is set on the conical outer surface of the conical section; the drag-reducing groove reduces the contact area between the conical section and the intermediate mold, and the frictional resistance between the core mold and the intermediate mold is also reduced during demolding.

[0029] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the specification or be learned by practicing the invention. The objectives and other advantages of this invention can be realized and obtained from the content specifically pointed out in the text and drawings. Attached Figure Description

[0030] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0031] Figure 1 This is a flowchart illustrating the forming method;

[0032] Figure 2 This is a schematic diagram of the overall structure of the forming mold;

[0033] Figure 3 This is a schematic diagram of the axial cross-section structure of the forming mold;

[0034] Figure 4 This is a schematic diagram of the cross-sectional structure of the forming mold;

[0035] Figure 5 This is a schematic diagram of the overall structure of the airbag;

[0036] Figure 6 A schematic diagram of the overall structure of the air bag and intermediate mold;

[0037] Figure 7 This is a schematic diagram of the overall structure of the cylindrical component;

[0038] Figure 8 This is an exploded structural diagram of the cylindrical component.

[0039] Reference numerals in the attached drawings: 1-Core mold; 2-Outer mold; 3-Intermediate mold; 4-Limiting ring; 5-Compensation module; 6-Top cover; 7-Air guide pipe hole; 11-Conical section; 12-Cylindrical section; 13-Drag reduction groove; 21-First outer cylinder section; 22-Second outer cylinder section; 31-First limiting block; 32-Second limiting block; 33-Air guide pipe; 51-First air bag; 52-Second air bag; 100-Cylindrical component; 101-First cylinder; 102-Second cylinder; 103-Third cylinder; 104-First boss; 105-Second boss; 110-First cylinder section; 120-Second cylinder section; 130-Third cylinder section. Detailed Implementation

[0040] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0041] Example 1

[0042] A specific embodiment of the present invention, such as Figure 1 As shown, a forming method for a cylindrical part with an internal boss and variable cross-section (hereinafter referred to as the forming method) is disclosed. The cylindrical part 100 is formed by diffusion connection using the forming device of Example 2.

[0043] like Figure 7 As shown, the cylindrical component 100 is the variable cross-section cylindrical component with internal bosses that needs to be processed in this invention. It includes a first cylindrical section 110, a second cylindrical section 120, a third cylindrical section 130, a first boss 104, and a second boss 105. The two ends of the second cylindrical section 120 are respectively connected to the first cylindrical section 110 and the third cylindrical section 130, and the first cylindrical section 110, the second cylindrical section 120, and the third cylindrical section 130 are coaxial. The first boss 104 is connected to the inner wall of the first cylindrical section 110, and the second boss 105 is connected to the inner wall of the third cylindrical section 130, and the end face of the second boss 105 is flush with the end face of the third cylindrical section 130. There are four first bosses 104, evenly distributed on the circumference of the first cylindrical section 110, and two second bosses 105, symmetrically distributed on the circumference of the third cylindrical section 130. The outer diameter of the second cylindrical section 120 is greater than the outer diameters of the first cylindrical section 110 and the third cylindrical section 130, and the inner diameter of the third cylindrical section 130 is greater than the inner diameters of the first cylindrical section 110 and the second cylindrical section 120.

[0044] Preferably, such as Figure 8As shown, to facilitate diffusion bonding forming of the cylindrical component 100, the cylindrical component 100 is divided into a first cylinder 101, a second cylinder 102, and a third cylinder 103. Connecting the second cylinder 102 to the outer wall of the first cylinder 101 forms a first cylindrical segment 110 and a second cylindrical segment 120. Connecting the third cylinder 103 to the inner wall of the first cylinder 101 forms a third cylindrical segment 130. The length of the first cylinder 101 is the same as the length of the cylindrical component 100, and the inner diameter of the first cylinder 101 is the same as the inner diameter of the first cylindrical segment 110 and the second cylindrical segment 120. The wall thicknesses of the first cylinder 101, the second cylinder 102, and the third cylinder 103 are all the same.

[0045] The cylindrical part 100 is made of TA15 titanium alloy. The finished cylindrical part 100 has an outer diameter of Φ300mm and a height of 150mm. The first cylindrical section 110 has a wall thickness of 5mm, and the second cylindrical section 120 and the third cylindrical section 130 both have a wall thickness of 10mm. The first boss 104 is a cubic boss, and the second boss 105 is a boss with a trapezoidal longitudinal section.

[0046] The forming method of this embodiment includes the following steps:

[0047] Step 1: Pre-forming cylindrical part 100, including the following sub-steps:

[0048] Step 11: Model disassembly;

[0049] like Figure 8 As shown, in accordance with the principle of saving time and raw materials, the process parts after disassembling the model include the first cylinder 101, the second cylinder 102, the third cylinder 103, the first boss 104 and the second boss 105, where the first boss 104 and the second boss 105 are pre-formed single-unit bosses.

[0050] Preferably, to ensure sufficient machining allowance after forming, the outer diameter of each part of the cylindrical component 100 in the preforming stage is increased by 2mm. Specifically, the second cylinder 102 has an outer diameter of 312mm and a thickness of 5mm, obtained by stacking and rounding five strips of 1mm*964mm*50mm titanium alloy plates; the third cylinder 103 has an inner diameter of 278mm and a thickness of 5mm, obtained by stacking and rounding five strips of 1mm*889mm*50mm titanium alloy plates; and the first cylinder 101 has an outer diameter of 302mm and a thickness of 7mm, obtained by stacking and rounding seven strips of 1mm*927mm*150mm titanium alloy plates.

[0051] Step 12: Make the first cylinder 101, the second cylinder 102 and the third cylinder 103;

[0052] A 1mm thick titanium alloy sheet is laser-cut according to the above-mentioned cutting dimensions. Then, a rounding machine is used to round the cut strips so that they can be joined together to form a cylinder.

[0053] Preferably, in order to be able to nest with each other, the inner layer of the sheet material needs to be 6mm shorter in length than the outer layer of the sheet material, and the surrounding burrs and slag should be removed after the cutting is completed.

[0054] Step 13: Fabricate the first boss 104 and the second boss 105;

[0055] The first boss 104 and the second boss 105 are cut and shaped using a combination of wire cutting and milling.

[0056] Step 14: Clean and pre-shape the workpiece;

[0057] To ensure diffusion quality, the diffusion surface needs to be polished. To ensure surface cleanliness before diffusion, all cylinders and bosses are subjected to alkaline pickling to remove surface contaminants and oxide layers. Then, all cylinders are nested together according to the model, and spot welded to the innermost and outermost rings to form the cylinder body.

[0058] Step 2: Mold closing;

[0059] Place the cylinder into the outer mold 2 and insert the limiting ring 4 into the gap between the cylinder and the outer mold 2;

[0060] Insert the first boss 104 and the second boss 105 into the first and second recesses of the intermediate mold 3, respectively.

[0061] The intermediate mold 3 is inserted into the cylinder.

[0062] Step 3: Diffusion bonding and forming, including the following sub-steps;

[0063] Step 31: Place the forming mold containing the cylindrical part 100 into the vacuum diffusion furnace;

[0064] Step 32: Connect the gas guide pipe 33 to the furnace gas pipe;

[0065] Preferably, the gas guide pipe 33 is welded to the furnace gas pipe to prevent gas leakage.

[0066] Step 33: Raise the temperature to 920℃-930℃;

[0067] Step 34: Apply pressure to the core mold 1 through the upper platform of the vacuum diffusion furnace, and keep it warm and pressurized to ensure the rigid diffusion of the first boss 104 and the second boss 105.

[0068] Preferably, the pressure applied to the core mold 1 is 30t, and the heat and pressure holding time is 1.5h-2h.

[0069] Step 35: Gas is introduced into the compensation module 5 through the furnace gas pipe to form diffusion pressure. The pressure is maintained for 1.5h-2h to ensure the flexible diffusion of the cylindrical part 100.

[0070] Preferably, the diffusion pressure is 1.5MPa-2MPa, and the heat and pressure holding time is 1.5h-2h. While applying air pressure, the compensation tonnage of the upper platform is increased simultaneously to ensure that the core mold 1 will not be ejected, thus affecting the diffusion accuracy.

[0071] Compared with the prior art, the forming method of the present invention uses a rigid diffusion connection for the first boss 104 and the second boss 105, and a flexible diffusion connection for the first cylindrical section 110, the second cylindrical section 120 and the third cylindrical section 130. Both of these methods can ensure the tight connection of each part of the variable cross-section cylindrical component with inner boss during diffusion, thus ensuring the quality of diffusion connection.

[0072] Step 4: Complete the diffusion bonding and demolding;

[0073] Remove the forming mold from the vacuum diffusion furnace and let it stand until the temperature reaches room temperature;

[0074] Rotate the top cover 6 to lift and remove the core mold 1;

[0075] Separate the top cover from the outer mold 2;

[0076] Push the second limiting block 32 radially toward the central axis and then remove it axially; then push the first limiting block 31 radially toward the central axis and then remove it axially.

[0077] Remove the cylindrical part 100 from the outer mold 2;

[0078] Remove the limiting ring 4 from the first cylindrical section 110 to complete the demolding.

[0079] Step 5: Machining the cylindrical part 100 and completing its forming;

[0080] The cylindrical part 100 is machined to achieve its final shape.

[0081] Example 2

[0082] Another specific embodiment of the present invention discloses a forming apparatus for a cylindrical part with an internal boss and variable cross-section, used in Embodiment 1, comprising a forming mold, a vacuum diffusion furnace, and a furnace gas pipe. The furnace gas pipe is disposed on the vacuum diffusion furnace, and the forming mold is disposed inside the vacuum diffusion furnace. The vacuum diffusion furnace is used to diffuse and connect the cylindrical part 100 into shape.

[0083] Preferably, one end of the gas pipe is located inside the vacuum diffusion furnace and connected to the forming mold, for introducing or expelling gas into or out of the forming mold; the other end of the gas pipe is located outside the vacuum diffusion furnace and connected to a gas source, which fills and releases gas for the forming mold.

[0084] The vacuum diffusion furnace includes an upper platform, which is connected to a press to provide downward pressure for the forming mold.

[0085] Preferably, such as Figure 2 and Figure 3 As shown, the forming mold includes a core mold 1, an outer mold 2, an intermediate mold 3, and a limiting ring 4. The core mold 1 can be connected to the intermediate mold 3, and the limiting ring 4 can be connected to the outer mold 2. The core mold 1 pushes the intermediate mold 3 towards the outer mold 2 by gravity, providing clamping force for the intermediate mold 3. A cylindrical component 100 is placed between the outer mold 2 and the intermediate mold 3. The cylindrical component 100 can be clamped and fixed by the outer mold 2, the intermediate mold 3, and the limiting ring 4, and diffuses and forms in the forming furnace by relying on the outer mold 2, the intermediate mold 3, and the limiting ring 4.

[0086] Preferably, the cylindrical component 100 includes a central axis, with the first cylindrical section 110 pointing upwards along the central axis and the third cylindrical section 130 pointing downwards along the central axis. The core mold 1, outer mold 2, intermediate mold 3, and limiting ring 4 are coaxial with the cylindrical component 100.

[0087] Preferably, such as Figure 2 As shown, the core mold 1 includes a conical segment 11 and a cylindrical segment 12, with the cylindrical segment 12 connected to the upper end of the conical segment 11. The axial cross-section of the conical segment 11 is trapezoidal, and the diameter of the upper end of the conical segment 11 is larger than the diameter of the lower end. The upper platform can press down on the core mold 1, pushing the cylindrical part 100 radially towards the outer mold 2. Due to the constraint of the outer mold 2 and the limiting ring 4, the cylindrical part 100 is tightly attached to the outer mold 2, the intermediate mold 3, and the limiting ring 4, thereby pressing the first cylinder 101, the second cylinder 102, the third cylinder 103, the first boss 104, and the second boss 105 together for diffusion connection. The cylindrical segment 12 is used for clamping during the demolding stage, allowing the core mold 1 to detach from the intermediate mold 3, thus facilitating the disassembly of the intermediate mold 3 and demolding.

[0088] Preferably, the conical segment 11 is provided with a drag-reducing groove 13, which is disposed on the conical outer surface of the conical segment 11. The drag-reducing groove 13 reduces the contact area between the conical segment 11 and the intermediate mold 3, and also reduces the frictional resistance between the core mold 1 and the intermediate mold 3 during demolding.

[0089] Preferably, the drag-reducing groove 13 is a longitudinal groove. When the core mold 1 is connected to the intermediate mold 3, air can pass through the drag-reducing groove 13, so that there is no negative pressure attraction between the core mold 1 and the intermediate mold 3.

[0090] Preferably, the outer mold 2 is a cylindrical outer mold. The outer diameter of the second cylindrical section 120 is larger than the outer diameters of the first cylindrical section 110 and the third cylindrical section 130. If the inner surface of the outer mold 2 is exactly the same as the outer surface of the cylindrical part 100, it will cause a situation where the mold cannot be closed. Therefore, the outer mold 2 includes a first outer cylindrical section 21 and a second outer cylindrical section 22, with one end of the first outer cylindrical section 21 connected to one end of the second outer cylindrical section 22. The inner diameter of the second outer cylindrical section 22 is the same as the outer diameter of the third cylindrical section 130, and the inner diameter of the first outer cylindrical section 21 is the same as the outer diameter of the second cylindrical section 120. The cylindrical part 100 can be axially inserted into the outer mold 2 from the upper end of the outer mold 2, and can also be demolded from the outer mold 2 in the axial direction. In order to fill the gap between the first outer cylindrical section 21 and the first cylindrical section 110, a limiting ring 4 is provided at the gap to ensure that after compensation, the first cylindrical section 110, the second cylindrical section 120 and the third cylindrical section 130 can be securely clamped.

[0091] Preferably, such as Figure 4 As shown, the intermediate mold 3 includes a first limiting block 31 and a second limiting block 32. One end of the first limiting block 31 is connected to one end of the second limiting block 32. The second limiting block 32 includes two connecting end faces, which are parallel to each other and parallel to the central axis, facilitating demolding. The first limiting block 31 is provided with a first recess and a second recess. The inner surface of the first recess is the same as the outer surface of the first boss 104, and the first recess is used to accommodate the first boss 104. The inner surface of the second recess is the same as the outer surface of the second boss 105, and the second recess is used to accommodate the second boss 105. The second limiting block 32 is provided with a first recess, which is used to accommodate the first boss 104.

[0092] During demolding, the second limiting block 32 is first pushed radially toward the central axis and then removed axially, after which the first limiting block 31 can be demolded, facilitating the demolding operation.

[0093] Due to machining errors, the intermediate mold 3 may have different contact states with the first cylindrical section 110, the second cylindrical section 120, the third cylindrical section 130, the first boss 104, and the second boss 105 on the cylindrical part 100. For example, when the intermediate mold 3 is tightly connected with the first boss 104 and the second boss 105, there may be gaps between it and the first cylindrical section 110, the second cylindrical section 120, and the third cylindrical section 130.

[0094] Preferably, such as Figure 5 and Figure 6 As shown, the forming mold also includes a compensation module 5, which is disposed on the intermediate mold 3 and is used to compensate for the gaps between the intermediate mold 3 and the first cylindrical section 110, the second cylindrical section 120 and the third cylindrical section 130.

[0095] Preferably, the compensation module 5 is a variable compensation module. Specifically, the compensation module 5 is a gas bag. The compensation module 5 can be connected to the furnace gas pipe, and can be filled and released during diffusion connection. The filling gas pressure can be adjusted, thereby controlling the thickness of the compensation module 5 so that the intermediate mold 3 maintains the same thrust on the first cylindrical section 110, the second cylindrical section 120, the third cylindrical section 130, the first boss 104, and the second boss 105.

[0096] Preferably, the compensation module 5 has multiple holes, the inner surface of which is the same as the outer surface of the first boss 104 or the second boss 105. At room temperature, the compensation module 5 is a rigid body, and the cylindrical part 100 cannot be molded or demolded with the compensation module 5. Preferably, the compensation module 5 includes a first air bag 51 and a second air bag 52, which are not connected. The first boss 104 and the second boss 105 can pass through the holes in the first air bag 51 and the second air bag 52 to connect with the intermediate mold 3. The first air bag 51 and the second air bag 52 allow the compensation module 5 to be disassembled, facilitating mold closing and demolding with diffusion connection.

[0097] Preferably, one end of the first air bag 51 is fixedly connected to the first limiting block 31, and one end of the second air bag 52 is fixedly connected to the second limiting block 32. Both the first limiting block 31 and the second limiting block 32 are provided with air guide pipes 33, through which the first air bag 51 and the second air bag 52 can be inflated or deflated.

[0098] Compared to the prior art, the compensation module 5 of the forming mold in this embodiment is a variable compensation module; the compensation module 5 can be inflated and deflated during diffusion connection, and the thickness of the compensation module 5 can be adjusted to compensate for the gap between the intermediate mold 3 and the cylindrical part 100, so that the intermediate mold 3 maintains the same thrust on the first cylindrical section 110, the second cylindrical section 120, the third cylindrical section 130, the first boss 104 and the second boss 105; the first air bag 51 and the second air bag 52 enable the compensation module 5 to be disassembled, which facilitates the mold closing and demolding of diffusion connection.

[0099] Preferably, such as Figure 3 As shown, the forming mold in this embodiment also includes a top cover 6. The axial section of the top cover 6 is inverted U-shape. The bottom end of the top cover 6 can be locked onto the outer mold 2 and connected to the outer mold 2. The top cover 6 includes a central hole, which is a through hole and is coaxial with the outer mold 2. The cylindrical segment 12 of the core mold 1 can pass through the central hole, which guides the core mold 1, making the core mold 1 coaxial with the outer mold 2.

[0100] After the diffusion connection is completed, the temperature of the forming mold drops to room temperature. The core mold 1 may be held tightly by the cylindrical part 100 through the intermediate mold 3, making demolding difficult. Preferably, the outer wall of the cylindrical section 12 has external threads, and the inner wall of the central hole has internal threads. The core mold 1 can rotate and descend along the internal threads using its own weight, and the top cover 6 can rotate around the central axis on the outer mold 2. During demolding, rotating the top cover 6 decomposes the rotational force into a lifting force for the core mold 1, causing the core mold 1 to detach upwards from the intermediate mold 3, facilitating demolding.

[0101] Preferably, the top cover 6 is also provided with an air guide hole 7, through which the air guide tube 33 can pass. At the same time, the air guide hole 7 can connect the air inside and outside the top cover, facilitating the discharge of air inside the top cover 6 during diffusion connection.

[0102] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for forming a cylindrical part with an internal boss and variable cross-section, characterized in that, The cylindrical part (100) is formed by diffusion connection using a forming mold. The forming mold includes a core mold (1), an outer mold (2), an intermediate mold (3), a limiting ring (4), and a compensation module (5). The intermediate mold (3) includes a first limiting block (31) and a second limiting block (32). The compensation module (5) includes a first air bag (51) and a second air bag (52). The forming method includes the following steps: A. Pre-forming; disassembling the cylindrical part (100) into process parts and forming a cylindrical body, wherein the process parts include a first cylinder (101), a second cylinder (102), a third cylinder (103), a first boss (104), and a second boss (105). B. Mold closing; Place the cylindrical body into the outer mold (2), and insert the limiting ring (4) between the cylindrical body and the outer mold (2); Insert the first boss (104) and the second boss (105) into the first recess and the second recess of the intermediate mold (3) respectively; Insert the intermediate mold (3) into the cylindrical body, so that the core mold (1) and the intermediate mold (3) are connected, and the core mold (1) pushes the intermediate mold (3) towards the outer mold (2), so that the cylindrical part (100) can be clamped and fixed by the outer mold (2), the intermediate mold (3) and the limiting ring (4); C. Diffusion connection forming; the upper platform of the vacuum diffusion furnace applies pressure to the core mold (1) to perform rigid diffusion connection; gas is injected into the compensation module (5) through the furnace gas pipe to expand the first gas bag (51) and the second gas bag (52) to compensate the gap between the intermediate mold (3) and the cylinder and perform flexible diffusion connection; D. Complete diffusion connection forming and demolding; remove the air pressure of the compensation module (5), take out the core mold (1), and take out the second limiting block (32) and the first limiting block (31) in sequence; take out the formed cylindrical part (100) from the outer mold (2).

2. The forming method of the variable cross-section cylindrical part with an internal boss according to claim 1, characterized in that, The core mold (1) includes a conical section (11) and a cylindrical section (12), and the outer wall of the cylindrical section (12) is provided with external threads.

3. The forming method of the variable cross-section cylindrical part with an internal boss according to claim 2, characterized in that, The conical section (11) is provided with a drag-reducing groove (13).

4. The forming method of the variable cross-section cylindrical part with internal boss according to claim 3, characterized in that, The first boss (104) and the second boss (105) are single bosses.

5. The forming method of the variable cross-section cylindrical part with an internal boss according to claim 2, characterized in that, The forming mold also includes a top cover (6), and the inner wall of the center hole of the top cover (6) is provided with an internal thread; in step D, by rotating the top cover (6), the internal thread and the external thread are engaged to drive the core mold (1) to move upward away from the intermediate mold (3).

6. The forming method of the variable cross-section cylindrical part with an internal boss according to claim 1, characterized in that, The outer mold (2) includes a first outer cylinder section (21) and a second outer cylinder section (22). The inner diameter of the second outer cylinder section (22) is the same as the outer diameter of the third cylindrical section (130) of the cylindrical part (100). The inner diameter of the first outer cylinder section (21) is the same as the outer diameter of the second cylindrical section (120) of the cylindrical part (100).

7. The forming method of the variable cross-section cylindrical part with an internal boss according to claim 1, characterized in that, Step A, preforming, also includes cleaning the workpiece.

8. The forming method of the variable cross-section cylindrical part with an internal boss according to claim 7, characterized in that, The cleaning process includes: polishing the diffusion surface of the process parts and performing alkaline pickling on all process parts.

9. The forming method of the variable cross-section cylindrical part with an internal boss according to claim 1, characterized in that, After step D, completing the diffusion connection forming and demolding, the process further includes the step of machining the cylindrical part (100) and completing the forming.

10. The forming method of the variable cross-section cylindrical part with an internal boss according to claim 9, characterized in that, The machining of the cylindrical part (100) and the completion of its forming include: machining the outer diameter of the cylindrical part (100).

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