Spinning additive composite processing method with outer lug cylinder

Abstract

A spinning additive composite processing method with outer lug cylinder, which makes full use of the technical advantages of spinning technology in processing thin-walled rotary parts and the advantages of additive manufacturing technology in local forming, so as to realize efficient and low-cost processing of the cylinder with unequal wall thickness and lug. In view of the shortcomings of the traditional spinning + additive manufacturing method, the invention adopts a split support, accurately controls the laser additive manufacturing parameters, and controls the deformation of the cylinder during the additive process; the additive part is cooled in real time during the laser additive process, which overcomes the problem of coarse grains and ensures the mechanical properties of the additive part, effectively solves the problems of size limitation, high cost, and large deformation of the outer surface of the cylinder during local additive manufacturing, and effectively controls the deformation of the cylinder.

Description

Technical Field

[0001] This invention relates to the spinning and additive manufacturing industry, specifically a method for manufacturing cylindrical tubes with external lifting lugs and unequal wall thicknesses using a combination of spinning and additive manufacturing. Background Technology

[0002] With the development of new weapons, engine casings with lifting lugs are becoming increasingly common. These casings are cylindrical structures with unequal wall thicknesses, typically with a thickness difference of 1-4 mm between the thin and thick walls. Lifting lugs are designed on the outer surface of the thicker wall sections. The dimensions of the connection between the lifting lugs and the cylindrical surface are approximately 40×40 mm, with a height of approximately 20-50 mm. A schematic diagram of this structure is attached. Figure 1 These structures require frequent and repeated hoisting during use, placing extremely high demands on structural strength. Currently, such mechanisms are manufactured using either thick-walled tube machining and welding or integral additive manufacturing. The thick-walled tube machining method involves extensive subtractive manufacturing, resulting in complex processes, slow processing efficiency, and low material utilization. Integral additive manufacturing, on the other hand, has dimensional limitations and higher costs.

[0003] There are currently two manufacturing processes used:

[0004] Machining and welding method: The raw material used is a thick-walled tube; after X-ray flaw detection, the thick-walled tube is rough-cut; the rough-cut thick-walled tube is heat-treated to obtain an excellent microstructure that meets the mechanical property requirements; and then it is finished to obtain a cylinder that meets the precision requirements.

[0005] Integral additive manufacturing method: Using metal powder, integral additive manufacturing is carried out to obtain a cylindrical blank; after flaw detection and heat treatment, the blank is precision machined to obtain a cylinder that meets the precision requirements.

[0006] The machining and welding method has a long processing cycle, complicated procedures, and low material utilization; the integral additive manufacturing method is limited by the volume of additive manufacturing equipment and has high cost and low processing efficiency.

[0007] Beijing Hangxing Machinery Manufacturing Co., Ltd. disclosed a partial additive manufacturing process for extruding preformed aluminum alloys in its patent application No. 201911114222.5. This invention manufactures preformed parts by using partial additive manufacturing on the outside of a machined finished substrate. However, the substrate used in this method is a thick-walled tube, and the partial additive manufacturing is relatively uniform. The company also disclosed a laser powder deposition forming and repair method for thin-walled aluminum alloy cylindrical structures in its patent application No. 202211658784.9. This method uses laser powder to coat the outer surface of the thin-walled aluminum alloy to repair the outer surface of the cylinder. However, this invention only coats a single forming layer on the outer surface, resulting in a small and uniform heat input, and minimal and easily controllable deformation. Therefore, it cannot be used for the laser powder additive manufacturing of external lifting lugs with a certain height as described in this invention.

[0008] To address the aforementioned problems of long processing cycles, cumbersome procedures, low material utilization, and high costs, this invention proposes a composite forming and deformation control method for cylindrical parts with lifting lugs and unequal wall thicknesses. This method fully utilizes the technical advantages of spinning technology in processing thin-walled rotating parts and the advantages of additive manufacturing technology in local forming, thereby achieving efficient and low-cost processing of cylindrical parts with lifting lugs and unequal wall thicknesses.

[0009] However, the difficulty in fabricating cylinders with lugs and unequal wall thickness using the spinning + additive manufacturing method lies in the fact that the laser additive manufacturing process involves a large heat input, which easily leads to deformation. Ensuring the shape accuracy of cylinders with unequal wall thickness is also challenging.

[0010] To address the problem of large deformation during laser additive manufacturing, this invention proposes a method for controlling deformation. This method employs a segmented support device to create a cylindrical shape and a cooling jacket for cooling, while precisely controlling the laser additive manufacturing parameters to manage the deformation of the cylinder during the additive manufacturing process. This is the core of the invention.

[0011] This method has two main challenges: first, excessive heat input leads to large deformation; second, large local deformation occurs in the additive manufacturing area, and the high temperature can cause grain coarsening, affecting local performance. Summary of the Invention

[0012] To improve the manufacturing efficiency of cylindrical cylinders with unequal wall thickness and to control deformation during laser powder feeding additive manufacturing of cylindrical cylinders with unequal wall thickness, this invention proposes a spinning additive composite processing method for cylindrical cylinders with external lifting lugs.

[0013] The specific process of this invention is as follows:

[0014] Step 1: Prepare the spinning blank;

[0015] Step 2, Set the segments of the spinning blank:

[0016] The spinning blank is a cylindrical tube with unequal wall thickness. Three reinforcing sections are located on the outer circumferential surface of the spinning blank, namely the first reinforcing section, the second reinforcing section, and the third reinforcing section. The first reinforcing section is located at one end of the spinning blank where a lifting lug is additively manufactured. The second and third reinforcing sections are distributed sequentially along the axial direction at the other end of the spinning blank, with a thin-walled section between each adjacent reinforcing section. The axial length ratio of the thin-walled section to the reinforcing section is 1:1.

[0017] Each of the thin-walled segments is 50 mm long. The first reinforcing segment is 2 mm thick, the second reinforcing segment is 2.5 mm thick, and the third reinforcing segment is 3 mm thick. The thickness of each thin-walled segment is 1.5 mm.

[0018] Step 3: Spin forming of cylindrical blanks with unequal wall thickness:

[0019] Based on the set structural parameters of the spinning blank, cylindrical blanks with unequal wall thicknesses are produced by high-pressure spinning.

[0020] The spinning parameters are as follows: axial offset of the spinning wheel is 8±1mm, feed ratio is 0.6mm / r, and spindle speed is 80r / min.

[0021] Obtain cylindrical blank

[0022] Step 4: Stress-relieving annealing of the cylindrical billet:

[0023] Preheat the annealing furnace to 300℃, and spray a heat treatment protective coating onto the surface of cylindrical billets with unequal wall thicknesses; allow them to dry naturally for 30 minutes after spraying; vertically place the cylindrical billets with the heat treatment protective coating into the annealing furnace, ensuring that the inclination angle of the cylindrical billets is ≤1°. The annealing furnace is heated uniformly at 2℃ / s to 450–650℃, and held at that temperature for 45–120 minutes; after holding, the billets are cooled with the furnace to below 200℃ before being removed from the furnace.

[0024] The thickness of the heat treatment protective coating is 25–30 μm.

[0025] Step 5: Install the deformation control fixture;

[0026] The controlled deformation fixture consists of a rounding mechanism and a cooling sleeve; the rounding mechanism includes segmented supports, a mandrel, and a cover plate. During installation, the cooling sleeve is inserted into the cylindrical blank, with its outer circumferential surface in contact with the inner circumferential surface of the cylindrical blank. The cooling sleeve has cooling pipes that correspond to the parts of the additive manufacturing lifting lugs. The three segmented supports of the rounding mechanism are inserted into the cooling sleeve, with each segmented support evenly distributed along the inner circumference of the cooling sleeve; the end face of the blank cylinder with the third reinforcing rib is in contact with the upper end face of the blank cylinder positioning platform at the lower end of each segmented support. The mandrel is placed inside the segmented supports, with its outer surface in contact with the inner surface of the segmented supports. The cover plate is fixed to the upper end face of each segmented support to maintain the rounded state of the cylinder.

[0027] Step 6: Preparation for laser powder feeding additive manufacturing:

[0028] The preparation for laser powder feeding additive manufacturing involves locally preheating the area where the lifting lugs will be manufactured on a spun cylindrical blank with unequal wall thickness that is equipped with a control deformation tool and a cooling jacket; the preheating temperature is 300℃ and the preheating time is 60min.

[0029] Step 7: Laser powder feeding additive manufacturing of lifting lugs.

[0030] A 2kW fiber laser was used to additively manufacture lifting lugs on the outer circumferential surface of a preheated, spun cylindrical blank of unequal wall thickness. Specifically:

[0031] An additive manufacturing coordinate system is established on the outer circumferential surface of the spun cylindrical blank with unequal wall thickness. The additive manufacturing coordinate system is based on the designed lifting lug position, with the edge of the designed lifting lug on the upper surface of the first reinforcing section as the origin, the axis of the spun cylindrical blank with unequal wall thickness as the X-axis, the circumferential direction of the spun cylindrical blank with unequal wall thickness as the Y-axis, and the radial direction of the spun cylindrical blank with unequal wall thickness as the Z-axis.

[0032] When using laser powder feeding additive manufacturing, the cooling device is first turned on for full-process cooling, and then the lifting lugs are printed layer by layer until the structural dimensions required by the design are achieved.

[0033] The specific process of layer-by-layer printing is as follows:

[0034] The first layer is printed along the axial direction of the spun cylindrical blank of the same wall thickness, starting at (0, 0, 0), with the path as follows: (0, 0, 0) → (40, 0, 0) → (40, 0.5, 0) → (0, 0.5, 0) → (0, 1, 0) → (40, 1, 0) → (40, 1.5, 0) → (0, 1.5, 0) → (0, 2, 0) → (40, 2, 0) → (40, 2.5, 0) → (0, 2.5, 0), as shown in the attached diagram. Figure 6 The path shown continues until (43, 28, 0);

[0035] After the first layer is printed, the laser returns to the origin and increases by one step in the Z-axis direction, which is (0, 0, 0.5). The second layer is then printed on the surface of the first layer. The starting point of the second layer is (0, 0, 0.5). The printing path is perpendicular to the path of the first layer, which is (0, 0, 0.5)→(0, 25, 0.5)→(0.5, 25, 0.5)→(0.5, 0, 0.5)→(1, 0, 0.5)→(1, 25, 0.5), until (41.5, 26.5, 0.5).

[0036] After the second layer is printed, the laser returns to the origin and increases by one step in the Z-axis direction, which is (0, 0, 1). The third layer is then printed on the surface of the second layer. The starting point of the third layer is (0, 0, 1). The printing path is perpendicular to the path of the second layer, which is (0, 0, 1)→(40, 0, 1)→(40, 0.5, 1)→(0, 0.5, 1)→(0, 1, 1)→(40, 1, 1)→(40, 1.5, 1)→(0, 1.5, 1)→(0, 2, 1)→(40, 2, 1)→(40, 2.5, 1)→(0, 2.5, 1), until (40, 25, 1).

[0037] After the third layer is printed, the laser returns to the origin and increases by one step in the Z-axis direction, which is (0, 0, 1.5). The fourth layer is then printed on the surface of the third layer. The starting point of the fourth layer is (0, 0, 1.5). The printing path is perpendicular to the path of the third layer, which is (0, 0, 1.5) → (0, 25, 1.5) → (0.5, 25, 1.5) → (0.5, 0, 1.5) → (1, 0, 1.5) → (1, 25, 1.5), until (40, 25, 1.5).

[0038] Repeat the printing paths of layer 3 and layer 4 above for additive manufacturing until (40, 25, 50) is reached.

[0039] When printing layer by layer, there are no gaps between layers.

[0040] The process parameters for the additive manufacturing of the lifting lug are as follows: laser spot diameter 1mm, laser power 1000W, scanning speed 15mm / min, inter-channel offset 1.5mm, layer thickness 0.6mm, forming gas flow rate 5L / min, and powder feed rate 4.5g / min. The manufacturing process is carried out in an argon protective atmosphere.

[0041] Step 7: Post-processing:

[0042] The post-processing refers to the grinding and annealing of the thin-walled cylinder with unequal thickness after the additive manufacturing of the lifting lugs is completed.

[0043] A thin-walled cylinder with unequal thickness and lugs is obtained.

[0044] The post-treatment annealing involves preheating the annealing furnace to 300°C; placing the added cylindrical structure with lifting lugs and a supporting mechanism into the annealing furnace. The furnace is heated uniformly at 2°C / s to 450–600°C and held for 30–90 minutes. After holding, the material is cooled in the furnace to below 200°C before being removed from the furnace.

[0045] This invention controls the deformation generated during laser additive manufacturing. The process is simple, the deformation control effect is good, and the deformation can be controlled within a length range. It can effectively solve the problems existing in the prior art with minimal cost and reduce the large deformation and local performance deviation caused by excessive heat input during laser additive manufacturing.

[0046] The objective of this invention is achieved through the following solution:

[0047] A method for composite manufacturing and deformation control of a cylindrical tube with unequal wall thickness and spun additive manufacturing with lifting lugs, characterized by comprising the following steps:

[0048] Fabrication of the spun cylindrical blank. The spun blank is prepared using ring forgings and machining methods according to industry standards.

[0049] Fabricate unequal wall thickness spun cylindrical blanks. Develop a spunting scheme based on the material, specifications, and dimensions of the unequal wall thickness cylinders, and perform high-pressure spunting to complete the spunting process of the unequal wall thickness cylindrical blanks.

[0050] Stress-relief annealing of spun cylinders. Preheat the annealing furnace to 300℃, place the spun cylinder vertically into the annealing furnace with an inclination angle ≤1°, then heat it to the annealing temperature and hold it thereafter. After holding, cool it to below 200℃ and remove it from the furnace. The annealing temperature is 450~650℃, and the annealing time is 45~120min. When the temperature is ≥600℃, an anti-oxidation protective coating should be applied to the surface. After annealing, use sandpaper to remove the oxide scale. The surface roughness of the cylinder should be controlled at Ra1.6, and the straightness of the cylinder should be ≤3mm.

[0051] Installation of the deformation control fixture. The deformation control fixture consists of a rounding mechanism and a cooling jacket. The rounding mechanism includes a segmented support, a mandrel, and a cover plate. The cooling jacket is a soft structure with flow channels that can wrap around the outer surface of the rounding mechanism. Coolant can flow into the flow channels. Place the segmented support inside cylinders of unequal wall thickness, evenly distributed around the circumference, with one end of the cylinder in contact with section A. Wrap the cooling jacket around the outer surface of the rounding mechanism and place it between the segmented support and the cylinder. The inner surface of the cylinder is in contact with the outer surface of the cooling jacket, and the outer surface of the segmented support is in contact with the inner surface of the cooling jacket. Place the mandrel inside the segmented support, with the outer surface of the mandrel in contact with the inner surface of the segmented support. Cover the cylinder with the cover plate and use bolts to connect the cover plate to the segmented support, maintaining the rounded state of the cylinder.

[0052] Preparation for laser powder feeding additive manufacturing: Place the cylinder, deformation control fixture, and cooling jacket into the laser powder feeding additive manufacturing device and align them to ensure that the cylinder's circular runout is ≤0.1mm. Preheat the cylinder using a flame gun for localized heating, with real-time monitoring using an infrared thermometer during the heating process. The temperature should not exceed 300℃, and the heating time should be 30-90 minutes.

[0053] Laser powder feeding additive manufacturing is performed. A 2kW fiber laser is used, with a spot diameter of 1–3mm, laser power of 1000–2000W, scanning speed of 500–1500mm / min, scanning spacing of 0.5–2mm, layer thickness of 0.3–1.2mm, and forming gas flow rate of 5–10L / min. The manufacturing process is carried out in an argon protective atmosphere. The scanning method is a unidirectional scan parallel to the diameter, with no rotation between two consecutive layers. Each layer constitutes one cycle, with no dwell time between cycles. First, a large-scale laser additive manufacturing of the bottom layer is performed. The bottom layer consists of 1–3 layers starting from the outer surface of the cylinder, with a power of 500–1000W and a layer thickness of 0.3–0.6mm. The additive area extends outward from the lifting lug as the center, reaching 3–4 times the area of ​​the lug's base.

[0054] Post-processing. After additive manufacturing, the surface of the cylinder is polished and inspected for flaws. After passing the flaw inspection, it is annealed with the rounding mechanism. The annealing temperature is 450-650℃ and the time is 30-90min.

[0055] This invention fully utilizes the technical advantages of spinning technology in processing thin-walled rotating parts and the advantages of additive manufacturing technology in local forming, thereby achieving efficient and low-cost processing of cylindrical parts with lifting lugs and unequal wall thicknesses.

[0056] This invention presents two challenges in fabricating cylinders with unequal wall thicknesses and lifting lugs using a spin forming + additive manufacturing method. First, the large heat input during laser additive manufacturing easily leads to deformation, making it difficult to guarantee the precision of the cylinders with unequal wall thicknesses. Second, the additive manufacturing area experiences significant localized deformation, and the high temperature can cause grain coarsening, affecting local mechanical properties. To address these challenges, this invention employs a segmented support and precisely controls the laser additive manufacturing parameters to manage cylinder deformation during the additive manufacturing process. Furthermore, a cooling jacket is used during laser additive manufacturing to cool the additive area in real time, overcoming the problem of grain coarsening and ensuring the mechanical properties of the additive area.

[0057] Compared with the integral cutting manufacturing method for thick-walled tubes, this invention effectively improves manufacturing efficiency, increases material utilization, and reduces costs. Taking a cylindrical tube with unequal wall thickness and lifting lugs (diameter 200mm, wall thickness 2.0mm, length 600mm, lug height 50mm) as an example, using the integral cutting manufacturing method for thick-walled tubes, the required material is a thick-walled tube with an inner diameter of 170mm, an outer diameter of 290mm, and a length of 650mm, weighing approximately 70kg. The material cost is approximately 4200 yuan, and the material utilization rate is approximately 3%-5%. The initial machining process requires 200 hours for roughing, 2 hours for flaw detection, 10 hours for heat treatment, and 300 hours for milling and finishing, totaling approximately 510 hours. Using the method described in this invention, the spinning preparation requires a thick-walled tube with an inner diameter of 180mm, an outer diameter of 210mm, and a length of 200mm, requiring 10kg of material powder. Machining the spinning blank takes 20 hours, spinning itself takes 5 hours, annealing after spinning takes 5 hours, laser additive manufacturing takes 10 hours, and annealing takes another 10 hours, totaling approximately 45 hours. Material utilization is approximately 20%–30%. Efficiency is increased by approximately 80%, and material utilization is increased by approximately 15%–20%.

[0058] Compared with integral additive manufacturing, this invention effectively solves the problems of size limitations and high costs. Integral additive manufacturing requires specialized powder materials, the unit price of which is approximately 20-30 times that of traditional forging materials. Currently, the widely used large-scale laser powder-feeding additive manufacturing equipment has a size of 800*800*800mm. Sizes exceeding the maximum volume of the equipment preclude the use of laser additive manufacturing, significantly limiting the manufacturing of cylindrical components with large aspect ratios. Compared with integral laser additive manufacturing, this method employs a spin forming + additive composite manufacturing approach, using forging materials as the main component and requiring less specialized powder material, resulting in cost savings of 30%-40%. Furthermore, the laser powder-feeding additive manufacturing equipment offers greater dimensional flexibility, and this method can be used to manufacture commonly used cylindrical components.

[0059] This invention effectively solves the problem of large deformation in local additive manufacturing of cylindrical outer surfaces with unequal wall thicknesses. The deformation control fixture has a simple structure, short preparation cycle, and can be recycled. Compared to the absence of a deformation control fixture, direct laser additive manufacturing of such cylindrical components with unequal wall thicknesses reduces the cylinder straightness from 5mm to ≤2mm, effectively controlling cylinder deformation. Attached Figure Description

[0060] Figure 1 This is a structural diagram of a cylindrical structure with lifting lugs and unequal wall thicknesses. Figure 1 'a' is the main view. Figure 1 b is a side view.

[0061] Figure 2 This is a schematic diagram of a cylindrical structure with unequal wall thickness.

[0062] Figure 3 This is a schematic diagram of the deformation control tooling;

[0063] Figure 4 These are part drawings of the deformable tooling. Among them, 4a is the split support, 4b is the cover plate, 4c is the side view of 4b, and 4d is the mandrel.

[0064] Figure 5 This is a schematic diagram of the cylinder and tooling after they are assembled.

[0065] Figure 6 yes Figure 5 Sectional view AA.

[0066] Figure 7 This is a schematic diagram of the cooling pipes.

[0067] Figure 8 This is a schematic diagram of the additive manufacturing process.

[0068] Figure 9 This is a coordinate diagram of an additively manufactured lifting lug.

[0069] In the figure: 1. Cylinder with unequal wall thickness; 2. Reinforcing section; 3. Lifting lug; 4. Cover plate; 5. Split support; 6. Mandrel; 7. Cylinder with unequal wall thickness; 8. Cooling jacket; 9. Lifting lug; 10. Cooling pipe; 11. First reinforcing section; 12. Second reinforcing section; 13. Third reinforcing section. Detailed Implementation

[0070] This embodiment describes a method for manufacturing a cylindrical cylinder with lifting lugs and unequal wall thickness using a spin forming and additive manufacturing composite process. The cylinder is as shown in the attached figure. Figure 2 The cylindrical tubes shown have unequal wall thicknesses.

[0071] The specific process is as follows:

[0072] Step 1, Prepare the spinning blank:

[0073] Using ring forgings, a spinning blank is prepared by conventional machining methods: the blank has an inner diameter of 207mm, a wall thickness of 10mm, a length of ≥100mm, and is made of ultra-high strength steel in a spheroidized annealed state with a hardness of HB≤200.

[0074] Step 2, Set the segments of the spinning blank:

[0075] The spun blank is a cylindrical tube 7 with unequal wall thickness. Three reinforcing sections are located on the outer circumferential surface of the spun blank: a first reinforcing section 11, a second reinforcing section 12, and a third reinforcing section 13. The first reinforcing section is located at one end of the spun blank where an additively manufactured lifting lug will be formed. The second and third reinforcing sections are distributed sequentially along the axial direction at the other end of the spun blank, with a thin-walled section between each adjacent reinforcing section. The axial length ratio of the thin-walled section to the reinforcing section is 1:1. In this embodiment, the length of each thin-walled section is 50 mm. The first reinforcing section has a thickness of 2 mm, the second reinforcing section has a thickness of 2.5 mm, and the third reinforcing section has a thickness of 3 mm. Each thin-walled section has a thickness of 1.5 mm.

[0076] Step 3: Spin forming of cylindrical blanks with unequal wall thickness:

[0077] A spinning scheme is formulated based on the material, specifications, and dimensions of cylinders with unequal wall thicknesses. Conventional spinning methods are used to produce cylinder blanks with unequal wall thicknesses through high-pressure spinning according to the set structural parameters of the spinning blank.

[0078] The spinning parameters are as follows: axial offset of the spinning wheel is 8±1mm, feed ratio is 0.6mm / r, and spindle speed is 80r / min.

[0079] A cylindrical blank is obtained. The structural parameters of this cylindrical blank are as follows:

[0080] The thickness of the thin-walled section is 1.5mm, the thickness of the first reinforcing section is 2mm, the thickness of the second reinforcing section is 2.5mm, the thickness of the third reinforcing section is 3mm, the length of each thin-walled section is 50mm, the axial length ratio of the thin-walled section to the reinforcing section is 1:1, and the inner diameter of the cylindrical blank is 207mm.

[0081] Step 4: Stress-relieving annealing of the cylindrical billet:

[0082] The annealing furnace is preheated to 300℃, and a heat treatment protective coating is sprayed onto the surface of cylindrical blanks with unequal wall thicknesses. The coating material is HB / Z 64-1981 No. 3, and the coating thickness is 25-30μm. After spraying, the blanks are allowed to dry naturally for 30 minutes to obtain cylindrical blanks with the heat treatment protective coating on their surface.

[0083] The cylindrical billet coated with protective paint is placed vertically into the annealing furnace, with the inclination angle of the billet ≤1°. The annealing furnace is heated uniformly to 450-600°C at a rate of 2°C / s, and held at that temperature for 45-120 minutes. After holding, the billet is cooled in the furnace to below 200°C before being removed from the furnace. In this embodiment, the annealing temperature is 500°C, and the holding time is 80 minutes.

[0084] After annealing, use sandpaper to remove any remaining coating on the surface and make the surface roughness of the spun cylinders with unequal wall thickness Ra1.6.

[0085] Step 5: Install the deformation control fixture:

[0086] Install the deformation control fixture using conventional methods.

[0087] The deformation control fixture is existing technology, consisting of a rounding mechanism and a cooling sleeve. The rounding mechanism includes segmented supports 5, a mandrel 6, and a cover plate 4. During installation, the cooling sleeve is inserted into the cylindrical blank, with its outer circumferential surface in contact with the inner circumferential surface of the cylindrical blank. The cooling sleeve has cooling pipes that correspond to the parts of the additive manufacturing lifting lugs. The three segmented supports 5 of the rounding mechanism are inserted into the cooling sleeve 8, with each segmented support evenly distributed along the inner circumference of the cooling sleeve. The end face of the blank cylinder with the third reinforcing rib is in contact with the upper end face of the blank cylinder positioning platform at the lower end of each segmented support. The mandrel is placed inside the segmented supports, with its outer surface in contact with the inner surface of the segmented supports. The cover plate is fixed to the upper end face of each segmented support to maintain the rounded state of the cylinder.

[0088] Step 6: Preparation for laser powder feeding additive manufacturing:

[0089] The unequal wall thickness spun cylindrical blank, equipped with a deformation control fixture and a cooling jacket, is placed in a laser powder feeding additive manufacturing device. Alignment is performed to ensure the cylindrical circular runout is ≤0.1mm. The area of ​​the unequal wall thickness spun cylindrical blank containing the additive manufacturing lifting lugs is locally preheated using a flame gun; the preheating process is monitored in real time using an infrared thermometer. The preheating temperature is 300℃, and the preheating time is 60 minutes.

[0090] Step 7: Laser powder feeding additive manufacturing of lifting lugs.

[0091] Lifting lugs are formed by additive manufacturing on the outer circumferential surface of a preheated, spun cylindrical blank of unequal wall thickness. Specifically:

[0092] A 2kW fiber laser with a spot diameter of 1mm, a laser power of 1000W, a scanning speed of 15mm / min, an inter-channel offset of 1.5mm, a layer thickness of 0.6mm, a forming gas flow rate of 5L / min, and a powder feed rate of 4.5g / min was used. The manufacturing process was carried out in an argon protective atmosphere.

[0093] Establish a coordinate system with the designed lifting lug position, using the edge of the designed lifting lug on the upper surface of the first reinforcing section as the origin, the axis of the unequal wall thickness spun cylindrical blank as the X-axis, the circumference of the unequal wall thickness spun cylindrical blank as the Y-axis, and the radial direction of the unequal wall thickness spun cylindrical blank as the Z-axis. During laser powder feeding additive manufacturing, first turn on the cooling device for full-process cooling, and then print layer by layer.

[0094] The first layer is printed along the axial direction of the spun cylindrical blank of the same wall thickness, starting at (0, 0, 0), with the path as follows: (0, 0, 0) → (40, 0, 0) → (40, 0.5, 0) → (0, 0.5, 0) → (0, 1, 0) → (40, 1, 0) → (40, 1.5, 0) → (0, 1.5, 0) → (0, 2, 0) → (40, 2, 0) → (40, 2.5, 0) → (0, 2.5, 0), as shown in the attached diagram. Figure 6 The path shown continues until (43, 28, 0);

[0095] After the first layer is printed, the laser returns to the origin and increases by one step in the Z-axis direction, which is (0, 0, 0.5). The second layer is then printed on the surface of the first layer. The starting point of the second layer is (0, 0, 0.5). The printing path is perpendicular to the path of the first layer, which is (0, 0, 0.5)→(0, 25, 0.5)→(0.5, 25, 0.5)→(0.5, 0, 0.5)→(1, 0, 0.5)→(1, 25, 0.5), until (41.5, 26.5, 0.5).

[0096] After the second layer is printed, the laser returns to the origin and increases by one step in the Z-axis direction, which is (0, 0, 1). The third layer is then printed on the surface of the second layer. The starting point of the third layer is (0, 0, 1). The printing path is perpendicular to the path of the second layer, which is (0, 0, 1)→(40, 0, 1)→(40, 0.5, 1)→(0, 0.5, 1)→(0, 1, 1)→(40, 1, 1)→(40, 1.5, 1)→(0, 1.5, 1)→(0, 2, 1)→(40, 2, 1)→(40, 2.5, 1)→(0, 2.5, 1), until (40, 25, 1).

[0097] After the third layer is printed, the laser returns to the origin and increases by one step in the Z-axis direction, which is (0, 0, 1.5). The fourth layer is then printed on the surface of the third layer. The starting point of the fourth layer is (0, 0, 1.5). The printing path is perpendicular to the path of the third layer, which is (0, 0, 1.5) → (0, 25, 1.5) → (0.5, 25, 1.5) → (0.5, 0, 1.5) → (1, 0, 1.5) → (1, 25, 1.5), until (40, 25, 1.5).

[0098] Repeat the printing paths for layer 3 and layer 4 above for additive manufacturing until (40, 25, 50). There are no gaps between layers.

[0099] Complete the printing of the lifting lug. The structural dimensions of the lifting lug are 50mm × 25mm × 50mm.

[0100] Step 7: Post-processing:

[0101] After additive manufacturing is completed, the surface of the cylinder is polished.

[0102] Preheat the annealing furnace to 300℃. Place the added cylindrical structure with lifting lugs and supporting mechanism into the annealing furnace. The furnace is heated uniformly at 2℃ / s to 450-600℃, and held at that temperature for 30-90 minutes. After holding, cool the cylinder with the furnace to below 200℃ before removing it from the furnace.

[0103] In this embodiment, the annealing temperature is 500℃ and the holding time is 45min.

Claims

1. A spinning additive composite processing method for a cylindrical tube with external lifting lugs, characterized in that, The specific process is as follows: Step 1: Prepare the spinning blank; Step 2, Set the segments of the spinning blank: The spinning blank is a cylindrical tube with unequal wall thickness (7). There are three reinforcing sections on the outer circumferential surface of the spinning blank, namely the first reinforcing section (11), the second reinforcing section (12), and the third reinforcing section (13). The first reinforcing section is located at the part where the lifting lug is additively manufactured at one end of the spinning blank. The second reinforcing section and the third reinforcing section are distributed along the axial direction at the other end of the spinning blank. There is a thin-walled section between each two adjacent reinforcing sections. The axial length ratio of the thin-walled section to the reinforcing section is 1:

1. Each thin-walled section is 50mm long; the first reinforcing section is 2mm thick, the second reinforcing section is 2.5mm thick, the third reinforcing section is 3mm thick; and each thin-walled section is 1.5mm thick. Step 3: Spin forming of cylindrical blanks with unequal wall thickness: According to the set structural parameters of the spinning blank, cylindrical blanks with unequal wall thickness are produced by high-pressure spinning. The spinning parameters are as follows: axial offset of the spinning wheel is 8±1mm, feed ratio is 0.6mm / r, and spindle speed is 80r / min; Obtain cylindrical blanks with unequal wall thicknesses; Step 4: Stress-relieving annealing of cylindrical billets with unequal wall thicknesses: Preheat the annealing furnace to 300℃, and spray a heat treatment protective coating onto the surface of the cylindrical billet with unequal wall thickness; allow it to dry naturally for 30 minutes after spraying; place the cylindrical billet with the heat treatment protective coating onto its surface vertically into the annealing furnace, ensuring that the inclination angle of the cylindrical billet is ≤1°; uniformly raise the temperature of the annealing furnace to 450~650℃ at a rate of 2℃ / s, and hold it for 45~120 minutes; after holding, cool it with the furnace to below 200℃ before removing it from the furnace. The thickness of the heat treatment protective coating is 25~30μm; Step 5: Install the deformation control fixture; The control deformation tooling consists of a rounding mechanism and a cooling sleeve; wherein, the rounding mechanism includes a segmented support (5), a mandrel (6), and a cover plate (4); during installation, the cooling sleeve is inserted into the cylindrical blank with unequal wall thickness, and the outer circumferential surface of the cooling sleeve is in contact with the inner circumferential surface of the cylindrical blank with unequal wall thickness; the cooling sleeve has a cooling pipe, which corresponds to the part of the additive manufacturing lifting lug; the three segmented supports (5) of the rounding mechanism are inserted into the cooling sleeve (8), and each segmented support is evenly distributed along the inner circumference of the cooling sleeve; the end face of the cylindrical blank with the third reinforcing rib is in contact with the upper end face of the positioning platform of the cylindrical blank with unequal wall thickness at the lower end of each segmented support; the mandrel is placed inside the segmented support, and the outer surface of the mandrel is in contact with the inner surface of the segmented support; the cover plate is fixed to the upper end face of each segmented support to maintain the state of rounding the cylindrical blank with unequal wall thickness; Step 6: Preparation for laser powder feeding additive manufacturing: The preparation for laser powder feeding additive manufacturing involves locally preheating the part of the additive manufacturing lifting lug on the cylindrical blank with unequal wall thickness that is equipped with a deformation control fixture. Step 7: Laser powder feeding additive manufacturing of the lifting lugs; A 2kW fiber laser is used to additively manufacture lifting lugs on the outer circumferential surface of preheated cylindrical blanks with varying wall thicknesses. During laser powder feeding additive manufacturing, the laser spot diameter is 1-3mm, the laser power is 1000-2000W, the scanning speed is 500-1500mm / min, the scanning interval is 0.5-2mm, the layer thickness is 0.3-1.2mm, and the forming gas flow rate is 5-10L / min. Specifically: An additive manufacturing coordinate system is established on the outer circumferential surface of the cylindrical blank with unequal wall thickness. The additive manufacturing coordinate system is based on the designed lifting lug position, with the edge of the designed lifting lug on the upper surface of the first reinforcing section as the origin, the axis of the cylindrical blank with unequal wall thickness as the X-axis, the circumferential direction of the cylindrical blank with unequal wall thickness as the Y-axis, and the radial direction of the cylindrical blank with unequal wall thickness as the Z-axis. When using laser powder feeding additive manufacturing, the cooling device is first turned on for full-process cooling, and then the lifting lugs are printed layer by layer until the structural dimensions required by the design are achieved. When printing layer by layer, there are no gaps between layers; Step 8: Post-processing: The post-processing refers to the grinding and annealing of the cylindrical parts with unequal wall thicknesses after the additive manufacturing of the lifting lugs is completed. A cylindrical tube with unequal wall thickness and lugs is obtained.

2. The spinning additive composite processing method for a cylindrical tube with external lifting lugs as described in claim 1, characterized in that, The preheating temperature is 300℃ and the preheating time is 60 minutes.

3. The spinning additive composite processing method for a cylindrical tube with external lifting lugs as described in claim 1, characterized in that, The process parameters for the additive manufacturing of the lifting lug are: laser spot diameter 1mm, laser power 1000W, inter-channel offset 1.5mm, layer thickness 0.6mm, forming gas flow rate 5L / min, and powder feeding rate 4.5g / min. The manufacturing process is carried out in an argon protective atmosphere.

4. The spinning additive composite processing method for a cylindrical tube with external lifting lugs as described in claim 1, characterized in that, The post-processing annealing involves preheating the annealing furnace to 300°C; placing the unequal wall thickness cylinder with lifting lugs and a supporting structure into the annealing furnace; uniformly heating the annealing furnace to 450~600°C at 2°C / s and holding it for 30~90 minutes; and then cooling it to below 200°C after holding it in the furnace before removing it from the furnace.

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