Additive manufacturing powder cleaning hole blocking method based on electron beam welding

Abstract

The invention provides an additive manufacturing powder cleaning hole blocking method based on electron beam welding, which comprises the following steps: a circular truncated cone-shaped powder cleaning hole is formed in an additive structure, the upper bottom surface is positioned on the inner surface of the additive structure, and the lower bottom surface is positioned on the outer surface of the additive structure; the circular-truncated-cone-shaped blocking block is assembled into the powder clearing hole of the material increasing structure, the blocking block is attached to the assembling face of the powder clearing hole, and the upper bottom face and the lower bottom face protrude out of the two ends of the powder clearing hole; preheating the lower bottom surface of the plugging block by using an electron beam, melting the surface layer of the lower bottom surface of the plugging block into a liquid state, and spreading to the outer surface of the additive structure; formal welding is conducted on the blocking block through electron beam welding, and the blocking block and the additive structure are welded into a whole; and after formal welding is finished, modification welding is conducted on the plugging block. Through structural design optimization of the powder cleaning holes and the blocking blocks and based on an improved electron beam welding method, reliable connection of tiny components is achieved, and the air tightness and the mechanical performance of additive products can be effectively guaranteed.

Description

Technical Field

[0001] This invention belongs to the field of powder cleaning hole sealing technology, and specifically relates to an additive manufacturing method for powder cleaning hole sealing based on electron beam welding. Background Technology

[0002] Additive manufacturing plays a crucial role in advanced manufacturing fields such as aerospace. It enables the rapid production of complex components such as lightweight integral bladed disks, rudders, and lattice structures, effectively reducing aircraft weight, improving fuel efficiency and performance, shortening development cycles, and quickly transforming design concepts into actual products, thus accelerating the development of new products. Furthermore, additive manufacturing allows for customized production of parts, meeting the specific needs of the aerospace manufacturing sector, reducing material waste, and lowering costs.

[0003] In practical applications, process cleaning holes are usually provided to facilitate the removal of residual powder from the inside of parts or complex structures, allowing the powder to be discharged smoothly under gravity or external force. However, the presence of cleaning holes reduces the effective load-bearing area of ​​the parts, disrupts the continuity and uniformity of the material, leads to stress concentration, and affects the performance and reliability of the parts.

[0004] For sealing powder cleaning holes, the following methods are commonly used: 1) Welding sealing: TIG welding is used to fuse the plug block with the surrounding material of the powder cleaning hole to achieve sealing; 2) Mechanical connection sealing: internal threads are machined into the powder cleaning hole, and then suitable bolts are used for sealing; 3) Adhesive sealing: a suitable structural adhesive is selected, applied to the area around the powder cleaning hole or the sealing component, and then the sealing component is bonded to the powder cleaning hole. Although the above methods achieve macroscopic sealing of the powder cleaning hole, they are difficult to effectively guarantee the airtightness and mechanical properties of the product. The use of TIG welding can also weaken the performance of the heat-affected zone structure, affecting the product's service performance. Summary of the Invention

[0005] To address the problem of sealing powder cleaning holes in existing additive manufacturing products, the inventors have conducted intensive research and developed a method for sealing powder cleaning holes in additive manufacturing based on electron beam welding. By optimizing the structural design of the powder cleaning holes and plugs, and based on an improved electron beam welding method, reliable connection of micro-components is achieved, which can effectively ensure the airtightness and mechanical properties of additive manufacturing products.

[0006] The technical solution provided by this invention is as follows: An additive manufacturing method for sealing powder-removed orifices based on electron beam welding, comprising: A frustum-shaped powder cleaning hole is made on the additive structure, with the upper bottom surface located on the inner surface of the additive structure and the lower bottom surface located on the outer surface of the additive structure. The frustum-shaped plug is assembled into the powder cleaning hole of the additive structure. The plug fits the assembly surface of the powder cleaning hole, and the upper and lower bottom surfaces protrude from both ends of the powder cleaning hole. The bottom surface of the block is preheated using an electron beam, melting the surface layer of the bottom surface of the block into a liquid state and spreading it to the outer surface of the additive structure. Electron beam welding was used to formally weld the plug to the additive structure, and the plug was then welded together. After the formal welding was completed, the plug was then finished with finishing welds.

[0007] The additive manufacturing powder removal hole sealing method based on electron beam welding provided by the present invention has the following beneficial effects: This invention provides a method for sealing powder removal holes in additive manufacturing based on electron beam welding. By optimizing the structural design of the powder removal holes and plugs, and based on an improved electron beam welding method, a reliable connection of micro-components is achieved, which can effectively ensure the airtightness and mechanical properties of additive products. Attached Figure Description

[0008] Figure 1 This is a schematic diagram of the powder cleaning hole structure; Figure 2 This is a schematic diagram of the block structure; Figure 3 This is a schematic diagram of the welding preform. Figure 4 Schematic diagram of electron beam welding block; Figure 5 This is a schematic diagram for modifying the welding trajectory. Detailed Implementation

[0009] The features and advantages of the present invention will become clearer and more apparent from the following detailed description.

[0010] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0011] This invention provides an additive manufacturing method for sealing powder-removed holes based on electron beam welding, comprising the following steps: (1) Powder cleaning hole structure design. For example... Figure 1 As shown, the powder cleaning hole is a frustum hole with a trapezoidal cross-section. The angle between the top surface and the two sides is 90° + (10~12)°, which facilitates the subsequent placement of the plug.

[0012] An angle of 10° to 12° ensures that the contact surface between the powder cleaning hole and the plug, i.e. the welding surface, is in a "near-parallel" state with the electron beam, which facilitates welding and ensures welding quality.

[0013] (2) Block structure design. For example... Figure 2As shown, the cross-section of the block is also trapezoidal, and the angle between the two sides and the upper bottom surface is consistent with the powder cleaning hole, ensuring good fit of the assembly surface.

[0014] The bottom surface of the block extends beyond the outer surface of the additive structure by a distance δ. h1 The height is 0.5~1mm. The increased height of the bottom surface ensures good weld back formation and a smooth transition with the additive structure substrate. The top surface of the block protrudes δ above the inner surface of the additive structure. h2 The excess length is 0.2~0.5mm, and the extra dimension on the top surface ensures good weld surface formation after welding.

[0015] (3) Welding pre-forming. For example... Figure 3 As shown, the block is preheated using an electron beam for 2-3 seconds. During this time, the welding current is relatively low, only melting the shallow surface of the block into a liquid state, allowing the liquid metal to spread and form a smooth surface. The preheating location is the center of the bottom surface of the block.

[0016] This step preheats the welding area, effectively reducing subsequent welding spatter and improving the quality of the weld.

[0017] (4) Formal welding. For example... Figure 4 As shown, electron beam welding was used to weld the plug, with the weld center located at a distance δ from the bottom edge of the powder cleaning hole. L / 2 (δ) L (1 / 2 of the difference between the top and bottom surfaces of the block's cross-section), along Figure 4 The circular dashed line trajectory shown in the figure is used for welding.

[0018] (5) Finishing welding. Along Figure 5 The circular dashed line trajectory shown is used for modification welding, and the center of the weld is δ away from the bottom edge of the powder cleaning hole. L / 2 locations. After modification, it can ensure good weld formation and a smooth transition to the body.

[0019] Example Example 1 In this embodiment, the additive structure body material is TA15 titanium alloy, the wall thickness at the powder cleaning hole is 5mm, the bottom diameter is 7mm, the top diameter is 5mm, and the bottom of the plug extends beyond the outer surface of the additive structure by δ. h1 It is 0.8mm thick, and the top is δ higher than the inner surface of the additive structure. h2 It is 0.3mm.

[0020] Pre-forming welding: After the plug is placed in position, it is preheated using an electron beam. The welding parameters are: accelerating voltage 100kV, electron beam current 5mA, X / Y axis scanning width 2 / 2mm, scanning frequency 100Hz, circular scanning waveform, and focusing current at the surface focus. The preheating position is the center of the bottom surface of the plug. After the electron beam is applied, the heating time is 2.5s. This melts the shallow surface of the plug into a liquid state, allowing the liquid metal to spread and form a smooth surface.

[0021] Welding: Electron beam welding was used to weld the block. The weld trajectory was a circular trajectory with a bottom diameter of 6mm. The arc start and end overlap angle was (20~30)°. The welding parameters were: acceleration voltage 100kV, electron beam current 10mA, X / Y axis scanning width 0.5 / 0.5mm, scanning frequency 100Hz, scanning waveform was circular, and focusing current was surface coke.

[0022] Modification welding: Modification welding is performed along the welding trajectory. The welding parameters are: accelerating voltage 100kV, electron beam current 5mA, X / Y axis scanning width 0.5 / 0.5mm, scanning frequency 100Hz, scanning waveform is circular, and focusing current is surface coke +10.

[0023] This completes the sealing of the powder removal holes in the TA15 titanium alloy structure. This embodiment can maintain pressure for more than 10 minutes under a gas pressure of 3.5~4.0MPa, and the mechanical properties of the joint are more than 90% greater than the lower limit of the base material strength.

[0024] Example 2 In this embodiment, the additive structure body material is AlSi10Mg aluminum alloy, the wall thickness at the powder cleaning hole is 6mm, the bottom diameter is 9mm, the top diameter is 7mm, and the bottom of the plug extends beyond the outer surface δ of the additive structure. h1 It is 1mm thick, and the top is δ higher than the inner surface of the additive structure. h2 It is 0.5mm.

[0025] Pre-forming welding: After the plug is placed in position, it is preheated using an electron beam. The welding parameters are: accelerating voltage 100kV, electron beam current 7mA, X / Y axis scanning width 2 / 2mm, scanning frequency 500Hz, circular scanning waveform, and focusing current at the surface focus. The preheating position is the center of the bottom surface of the plug. After the electron beam is applied, the heating time is 3s. This melts the shallow surface of the plug into a liquid state, allowing the liquid metal to spread and form a smooth surface.

[0026] Welding: Electron beam welding was used to weld the block. The weld trajectory was a circular trajectory with a bottom diameter of 8mm. The arc start and end overlap angle was (20~30)°. The welding parameters were: acceleration voltage 100kV, electron beam current 12mA, X / Y axis scanning width 0.5 / 0.5mm, scanning frequency 500Hz, scanning waveform was circular, and focusing current was surface coke.

[0027] Modification welding: Modification welding is performed along the welding trajectory. The welding parameters are: accelerating voltage 100kV, electron beam current 7mA, X / Y axis scanning width 0.5 / 0.5mm, scanning frequency 500Hz, scanning waveform is circular, and focusing current is surface coke +10.

[0028] This completes the sealing of the powder-cleaning holes in the AlSi10Mg aluminum alloy structure. This embodiment can maintain pressure for more than 10 minutes under a gas pressure of 1.5~2.0MPa, and the mechanical properties of the joint are more than 80% greater than the lower limit of the strength of the base material.

[0029] Example 3 In this embodiment, the additive structure body material is GH4099 high-temperature alloy. The wall thickness at the powder cleaning hole location is 6mm, the bottom diameter is 6mm, the top diameter is 4mm, and the bottom of the plug extends beyond the outer surface δ of the additive structure. h1 The thickness is 0.5mm, and the top surface protrudes δ above the inner surface of the additive structure. h2 It is 0.2mm.

[0030] Pre-forming welding: After the plug is placed in position, it is preheated using an electron beam. The welding parameters are: accelerating voltage 200kV, electron beam current 4mA, X / Y axis scanning width 2 / 2mm, scanning frequency 200Hz, circular scanning waveform, and focusing current at the surface focus. The preheating position is the center of the bottom surface of the plug. After the electron beam is applied, the heating time is 3s. This melts the shallow surface of the plug into a liquid state, allowing the liquid metal to spread and form a smooth surface.

[0031] Welding: Electron beam welding was used to weld the block. The weld trajectory was a circular trajectory with a bottom diameter of 5mm. The arc start and end overlap angle was (20~30)°. The welding parameters were: acceleration voltage 100kV, electron beam current 8mA, X / Y axis scanning width 0.5 / 0.5mm, scanning frequency 200Hz, scanning waveform was circular, and focusing current was surface coke.

[0032] Modification welding: Modification welding is performed along the welding trajectory. The welding parameters are: accelerating voltage 100kV, electron beam current 4mA, X / Y axis scanning width 0.5 / 0.5mm, scanning frequency 200Hz, scanning waveform is circular, and focusing current is surface coke +10.

[0033] This completes the sealing of the powder removal holes in the GH4099 high-temperature alloy structure. This embodiment can maintain pressure for more than 10 minutes under a gas pressure of 3.5~4.0MPa, and the mechanical properties of the joint are more than 90% greater than the lower limit of the base material strength.

[0034] Comparative Example Comparative Example 1 Comparative Example 1 is the same as Example 1, except that the powder cleaning hole is a cylindrical hole with a rectangular cross-sectional structure.

[0035] In this comparative example, to prevent the plug from loosening and falling into the structure, it needs to be machined to an interference fit size. The structural restraint stress is relatively large, and the mechanical properties of the joint are 80%~90% of the lower limit of the base material strength. Under a gas pressure of 3.5~4.0MPa, the pressure is maintained for 5min~10min.

[0036] Comparative Example 2 Comparative Example 2 is the same as Example 1, except that the top and bottom surfaces of the block do not extend beyond the inner and outer surfaces of the additive structure.

[0037] In this comparative example, the weld is prone to collapse, the mechanical properties of the joint are 75%~80% of the lower limit of the base metal strength, and the holding time is less than 5 minutes under a gas pressure of 3.5~4.0MPa.

[0038] Comparative Example 3 Comparative Example 3 is the same as Example 1, except that the block was not subjected to a welding pre-forming step, but was directly welded.

[0039] In this comparative example, poor weld formation is likely to occur, and the mechanical properties of the joint are 75%~80% of the lower limit of the base material strength. Under a gas pressure of 3.5~4.0MPa, the holding time is less than 5min.

[0040] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

[0041] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A method for sealing powder-cleaning holes in additive manufacturing based on electron beam welding, characterized in that, include: A frustum-shaped powder cleaning hole is made on the additive structure, with the upper bottom surface located on the inner surface of the additive structure and the lower bottom surface located on the outer surface of the additive structure. The frustum-shaped plug is assembled into the powder cleaning hole of the additive structure. The plug fits the assembly surface of the powder cleaning hole, and the upper and lower bottom surfaces protrude from both ends of the powder cleaning hole. The bottom surface of the block is preheated using an electron beam, melting the surface layer of the bottom surface of the block into a liquid state and spreading it to the outer surface of the additive structure. Electron beam welding was used to formally weld the plug to the additive structure, and the plug was then welded together. After the formal welding was completed, the plug was then finished with finishing welds.

2. The method for sealing powder-removing holes in additive manufacturing based on electron beam welding according to claim 1, characterized in that, The cross-section of the powder cleaning hole is trapezoidal, and the angle between the upper base and the two waists is 90° + (10~12)°.

3. The additive manufacturing powder cleaning hole sealing method based on electron beam welding according to claim 1, characterized in that, The bottom surface of the block extends 0.5-1 mm beyond the outer surface of the additive structure, and the top surface of the block extends 0.2-0.5 mm above the inner surface of the additive structure.

4. The additive manufacturing powder cleaning hole sealing method based on electron beam welding according to claim 1, characterized in that, When using an electron beam to preheat the bottom surface of the block, the preheating position is the center of the bottom surface of the block.

5. The additive manufacturing powder cleaning hole sealing method based on electron beam welding according to claim 1, characterized in that, When performing formal welding on the plug using electron beam welding, the center of the weld is δ away from the bottom edge of the powder cleaning hole. L At / 2, the δ L It is half the difference between the top and bottom surfaces of the block's cross-section.

6. The additive manufacturing powder cleaning hole sealing method based on electron beam welding according to claim 1, characterized in that, When performing the modification welding on the block, the center of the weld is δ away from the bottom edge of the powder cleaning hole. L At / 2, the δ L It is half the difference between the top and bottom surfaces of the block's cross-section.

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