Self-supporting channel type heat pipe based on selective laser melting and preparation method of self-supporting channel type heat pipe

Abstract

The invention belongs to the technical field of heat transfer, and discloses a self-supporting channel type heat pipe based on selective laser melting and a preparation method thereof.The self-supporting channel type heat pipe based on selective laser melting comprises a heat pipe body and a round pipe, the two ends of the heat pipe body are closed, and a hollow cavity is formed in the round pipe; a plurality of groove teeth are arranged on the inner wall of a hollow cavity of the heat pipe body, a groove with a capillary function is formed between every two adjacent groove teeth, and the heat pipe is characterized in that when the heat pipe body is horizontally placed, the hollow cavity comprises an upper cavity area located on the upper portion and a lower cavity area located below the upper cavity area. The included angle between the inclined face of the groove tooth located in the upper cavity area and the horizontal direction of the position where the groove tooth is located ranges from 45 degrees to 55 degrees, and self-supporting is formed through the layer-by-layer stacking forming technology. According to the self-supporting channel type heat pipe, the problem that the forming effect of a suspension structure is poor in the process of machining and manufacturing the heat pipe through additive manufacturing is solved.

Description

Technical Field

[0001] The invention relates to the technical field of heat transfer, and in particular to a self-supporting channel type heat pipe based on laser selective melting and a preparation method thereof. Background Art

[0002] Heat pipe is an efficient thermal management device that uses the principle of phase change heat transfer and is widely used in electronic equipment, spacecraft and industrial systems. Its core structure includes a sealed tube body and an internal working fluid. The working fluid absorbs heat in the evaporation zone and turns into steam, and then transfers the heat to the condensation zone through gas flow. In the condensation zone, the steam condenses into liquid and releases heat, and the liquid returns to the evaporation zone through capillary action or gravity. This process can achieve extremely low thermal resistance and improve heat conduction efficiency. Heat pipe technology has become a key component of modern thermal control technology due to its excellent thermal management performance and compact design. The heat transfer performance of the heat pipe mainly depends on the capillary capacity and permeability of the wick. The groove wick structure has become a widely used wick structure due to its advantages such as light weight, non-deformation, and no contact thermal resistance.

[0003] At present, the processing process of grooved wick heat pipe mainly includes the manufacturing of wick, assembly of heat pipe, filling and sealing. Among them, the manufacturing of key wick, the processing method of grooved wick is mainly through stamping and laser cutting. The traditional processing method is simple but has limited processing accuracy for micro-size, long production cycle and low material utilization rate. However, with the development of additive manufacturing technology, it provides us with new ideas for processing grooved heat pipes.

[0004] Due to the characteristics of additive manufacturing processing itself, overhanging structures are prone to deformation or sagging. This is because the material will be affected by gravity before it is completely solidified during the deposition process, resulting in inaccurate molding. If support structures are added. However, these support structures need to be removed after printing is completed. The removal process may damage the finished product or leave defects, and the removal of the support structure may not be complete. The remaining support will affect the performance or appearance of the final product. Although laser selective melting technology has unique advantages for processing channel-type wick heat pipes, the problems that may arise in the processing of overhanging structures greatly affect the molding effect of the heat pipe. In response to this situation, it is urgent to propose a new self-supporting channel structure based on additive manufacturing processing to improve the poor processing effect on the overhanging part. Summary of the invention

[0005] In view of the above defects or improvement needs of the prior art, the present invention provides a self-supporting grooved heat pipe based on laser selective melting and a preparation method thereof, so as to improve the problem of poor forming effect of the overhanging structure in the process of manufacturing the heat pipe using additive manufacturing.

[0006] To achieve the above-mentioned purpose, according to one aspect of the present invention, a self-supporting grooved heat pipe based on laser selective melting is provided, comprising a heat pipe body, a round tube with closed ends and a hollow cavity inside, a plurality of groove teeth are provided on the inner wall of the hollow cavity of the heat pipe body, and a groove with capillary effect is formed between two adjacent groups of groove teeth. The heat pipe body is characterized in that when the heat pipe body is placed horizontally, the hollow cavity comprises an upper cavity area located above and a lower cavity area located below the upper cavity area, and the angle between the inclined surface of the groove teeth located in the upper cavity area and the horizontal direction of the position of the groove teeth is 45°-55°, so that self-support is formed by layer-by-layer stacking molding technology.

[0007] Preferably, the angle between the groove teeth located in the lower cavity area and the horizontal direction where the groove teeth are located is between 45° and 90°.

[0008] Preferably, the top of the upper cavity area is in an arc structure to reduce gas flow resistance; the inner wall spacing of the upper cavity area gradually decreases toward the arc structure at the top to facilitate steam flow in the upper cavity area.

[0009] Preferably, in a cross section of any heat pipe body, the grooves and groove teeth are symmetrically distributed on both sides of the hollow cavity.

[0010] Preferably, the groove width of the groove teeth is 0.60-1.00 mm.

[0011] Preferably, the groove depth of the groove teeth is 0.80-1.20 mm.

[0012] To achieve the above object, according to one aspect of the present invention, a method for preparing a self-supporting channel heat pipe based on laser selective melting is provided, wherein the self-supporting channel heat pipe is prepared by an additive manufacturing method, and the method specifically comprises the following steps:

[0013] S1 modeling, build the CAD model of the parts to be processed and obtain the STL format file;

[0014] S2 slicing, importing the STL format model file obtained in step S1 into the forming control device, slicing the model using special software to obtain part contour information;

[0015] S3 plans the scanning path and sets the forming process parameters based on step S2;

[0016] S4 pre-powder, using a scraper or powder roller to spread a uniform layer of powder on the substrate or formed parts;

[0017] S5 forming, according to the graphic slice information obtained in step S2 and the forming parameters set in step S3, controlling the galvanometer to select and melt the metal powder to form a metallurgical bonding entity;

[0018] S6: Powder is spread again and the laser beam is scanned; after the current layer is formed, the forming cylinder descends by a layer thickness, and the powder feeding cylinder rises a certain distance to continue spreading powder, and steps S4 and S5 are repeated until the part processing is completed.

[0019] Preferably, the powder spreading thickness in step S4 is 0.1 mm.

[0020] Preferably, in step S6, the laser beam power is 200 W, the spot diameter is 0.08 mm, the scanning speed is 1400-3000 mm / s, and the scanning interval is 0.06-0.10 mm.

[0021] In general, the above technical solution conceived by the present invention has the following beneficial effects compared with the prior art:

[0022] 1. The heat pipe of the present invention is manufactured based on laser selective melting technology, which has a simple and feasible process, high material utilization, short processing cycle and good micro-size structure processing effect; the heat pipe of the present invention changes the structure of the traditional channel-type liquid absorption core, improves the overhanging structure that is prone to deformation during processing, which is beneficial to improving the forming effect of the heat pipe under the additive manufacturing process and thus improving the heat transfer efficiency of the heat pipe.

[0023] 2. The heat pipe of the present invention adopts a new groove structure design, which improves the forming effect through additive manufacturing technology and allows the design of the heat pipe shape to be more flexible and changeable.

[0024] 3. The heat pipe of the present invention changes the top structure of the upper cavity area of ​​the heat pipe, reduces the flow resistance of the gaseous working medium, is beneficial to improve the circulation efficiency of the gaseous working medium when the heat pipe is working, and thus improves the heat transfer efficiency of the heat pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a cross-sectional view of the self-supporting channel heat pipe of the present invention Figure 1 .

[0026] Figure 2 is a cross-sectional view of the self-supporting channel heat pipe of the present invention Figure 2 .

[0027] Figure 3 It is a structural schematic diagram of the self-supporting channel type heat pipe of the present invention.

[0028] Figure 4 It is a schematic diagram of the cross-sectional structure of a traditional slot heat pipe.

[0029] Figure 5 It is a schematic diagram of the cross-sectional structure of the self-supporting channel type heat pipe of the present invention.

[0030] Figure 6 It is a schematic diagram of a method for preparing a self-supporting channel-type heat pipe of the present invention.

[0031] Figure 7 This is a schematic diagram of the overhang defect that occurs in the groove structure of the upper cavity area during the traditional groove heat pipe laser selective melting process.

[0032] In the attached drawings: 1-heat pipe body, 2-groove, 3-groove teeth, 11-upper cavity area, 12-lower cavity area. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0034] Overhanging structural defects are a common problem in additive manufacturing (e.g. Figure 7 As shown in the figure, the overhang structure refers to the part without support or insufficient support during the printing process, usually extending upward from the printing platform or lower layer. Usually, adding support structure is used to improve this defect. Since the structure of the slot heat pipe is small and complex, adding support structure and removing the support structure later is likely to destroy the original heat pipe structure. Therefore, we choose to optimize the slot structure of the heat pipe.

[0035] See also Figure 1 and Figure 3 The present invention provides a self-supporting grooved heat pipe based on laser selective melting, comprising a heat pipe body 1, which is a round tube with closed ends and a hollow cavity inside. A plurality of groove teeth 3 are arranged on the inner wall of the hollow cavity of the heat pipe body 1, and a groove 2 with a capillary effect is formed between two adjacent groups of groove teeth 3. When the heat pipe body 1 is placed horizontally, the hollow cavity comprises an upper cavity area 11 located above and a lower cavity area 12 located below the upper cavity area 11. The angle between the inclined surface of the groove tooth 3 located in the upper cavity area 11 and the horizontal direction of the position of the groove tooth 3 is 45°-55°, and the self-support is formed by layer-by-layer stacking molding technology.

[0036] When facing the additive manufacturing of non-linear or large heat pipes, it is necessary to place the heat pipe in a horizontal direction for processing. Due to the small structure of the groove heat pipe, the added support structure is not easy to remove and is easy to damage the original structure. The top groove teeth of the upper cavity area are prone to defects during processing. For this reason, the groove teeth of the upper cavity area of ​​the traditional groove heat pipe are changed, and the horizontal angle between the inclined surface of the groove teeth 3 of the upper cavity area 11 and the position of the groove teeth 3 is set to 45°-55°. Because the minimum inclination angle that can form a self-support by layer-by-layer stacking molding technology is usually 45°, when the inclination angle of the part structure is less than 45 degrees, there will be more "suspended parts" during the printing process, that is, there is no direct support material under the printing layer; these suspended parts cannot be stably constructed during the melting process due to the influence of gravity and thermal stress, and are prone to processing defects that affect the processing quality. If the inclination angle of the groove teeth is too large, the actual volume of the groove will be reduced, thereby affecting the efficiency of liquid reflux. Therefore, after comprehensive consideration, the horizontal angle between the inclined surface of the groove teeth 3 of the upper cavity area 11 and the position of the groove teeth 3 is set to 45°-55°.

[0037] The angle between the groove teeth 3 located in the lower cavity area 12 and the horizontal direction where the groove teeth 3 are located is between 45° and 90°, and the specific value is selected according to actual needs; the top of the upper cavity area 11 is an arc structure to reduce the gas flow resistance; specifically, Figure 3 As shown, the inclined surface of the groove tooth 3 located in the upper cavity area 11 includes an angle a with the horizontal direction of the position of the groove tooth 3, and the angle a is 45°-55°; the inclined surface of the groove tooth 3 located in the lower cavity area 14 includes an angle b with the horizontal direction of the position of the groove tooth 3, and the angle b is 45°-90°.

[0038] During the operation of the heat pipe, the working fluid is heated and vaporized and mainly concentrated in the upper cavity area 11 of the heat pipe. During the operation, it flows from the heating end to the condensing end. During the flow, the gaseous working fluid will be rubbed by the pipe wall and the groove, thereby generating flow resistance. Designing the top of the upper cavity area 11 as a smooth round tube wall can make the gaseous working fluid flow more smoothly, reduce the flow resistance of the gaseous working fluid, improve the working fluid circulation efficiency and thus improve the working efficiency of the heat pipe. At the same time, the groove 2 of the lower cavity area 12 produces a capillary effect, which prompts the liquid working fluid to flow back from the condensing section to the heating end.

[0039] The inner wall spacing of the upper cavity area 11 gradually decreases toward the arc structure at the top, so that steam can flow in the upper cavity area 11; on the cross section of any heat pipe body 1, the grooves 2 and the groove teeth 3 are symmetrically distributed on both sides of the hollow cavity.

[0040] The groove width of the groove teeth 3 is 0.60-1.00mm, and the groove depth of the groove teeth 3 is 0.80-1.20mm. Small grooves with capillary action are formed between adjacent groove teeth. Due to the surface tension between the liquid working medium and the groove surface, the working medium can flow along the groove, thereby providing power for the internal circulation of the heat pipe.

[0041] During the laser selective melting process, the common groove heat pipe Figure 4 The ribs in area A can be processed well, while the ribs in area B are all in a suspended state. During the processing, defects are easily formed due to insufficient powder support, such as Figure 7 As shown, the final heat pipe forming effect is affected. The self-supporting channel heat pipe based on laser selective melting in this embodiment is as follows Figure 5 As shown, area C is the solid part of the metal heat pipe during the laser selective melting process, and area D is the internal cavity part of the heat pipe. During the processing, since the angle a between the inclined surface of the groove tooth 3 located in the upper cavity area 11 and the horizontal direction of the position of the groove tooth 3 is 45°-55°, the suspended part of the upper layer relative to the lower layer of powder during the printing process is reduced, and the metal solid part and the metal powder can form a more effective support for the processing layer, which can effectively improve the heat pipe forming effect.

[0042] The self-supporting channel-type heat pipe of the present invention changes the structure of the traditional channel-type liquid-absorbing core, improves the overhanging structure that is prone to deformation during processing, and is beneficial to improving the forming effect of the heat pipe under the additive manufacturing process; the process is simple and feasible, the material utilization is high, the processing cycle is short, and the micro-size structure processing effect is good.

[0043] This embodiment adopts the additive manufacturing method to prepare the self-supporting channel heat pipe. The forming process of laser selective melting is as follows: Figure 6 As shown, a method for preparing a self-supporting channel heat pipe based on laser selective melting specifically comprises the following steps:

[0044] S1 modeling: building a CAD model of the parts to be processed and converting the design model into STL format or other file formats suitable for additive manufacturing;

[0045] S2 slicing, importing the STL format model file obtained in step S1 into the forming control device, and slicing the model using special software. The thickness of each slice layer determines the forming accuracy and provides contour information of the model parts for subsequent processing;

[0046] S3 plans the scanning path and sets the forming process parameters based on step S2;

[0047] S4 pre-powder, using a scraper or powder roller to lay a layer of powder with a thickness of tens of microns on the substrate or formed parts;

[0048] S5 forming, according to the graphic slice information obtained in step S2 and the forming parameters set in step S3, controlling the galvanometer to select and melt the metal powder to form a metallurgical bonding entity;

[0049] S6: Powder is spread again and the laser beam is scanned; after the current layer is formed, the forming cylinder is lowered by a layer thickness, and the powder feeding cylinder is raised by a certain distance to continue spreading powder, and steps S4 and S5 are repeated until the part processing is completed.

[0050] During the forming process, the parameters were set as follows: fixed laser power of 200 W, scanning speed of 1400-3000 mm / s, powder thickness of 0.1 mm, spot diameter of 0.08 mm, and scanning spacing of 0.06-0.10 mm.

[0051] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A self-supporting channel heat pipe based on laser selective melting, comprising a heat pipe body (1), the heat pipe body (1) being a round tube with closed ends and a hollow cavity therein, a plurality of groove teeth (3) being arranged on the inner wall of the hollow cavity of the heat pipe body (1), a groove (2) having a capillary effect being formed between two adjacent groups of groove teeth (3), characterized in that: When the heat pipe body (1) is placed horizontally, the hollow cavity comprises an upper cavity area (11) located above and a lower cavity area (12) located below the upper cavity area (11); the angle between the inclined surface of the groove tooth (3) located in the upper cavity area (11) and the horizontal direction of the position of the groove tooth (3) is 45°-55°, and self-support is formed by layer-by-layer stacking molding technology.

2. A self-supporting channel heat pipe based on laser selective melting as claimed in claim 1, characterized in that: The angle between the inclined surface of the groove tooth (3) located in the lower cavity area (12) and the horizontal direction where the groove tooth (3) is located is between 45° and 90°.

3. A self-supporting channel heat pipe based on laser selective melting as claimed in claim 1, characterized in that: The top of the upper cavity area (11) is in an arc structure to reduce gas flow resistance.

4. A self-supporting channel heat pipe based on selective laser melting as claimed in claim 3, characterized in that: The inner wall spacing of the upper cavity area (11) gradually decreases towards the arc structure at the top, so that steam can flow in the upper cavity area (11).

5. The self-supporting channel heat pipe based on laser selective melting according to claim 1, characterized in that: In the cross section of any heat pipe body (1), the grooves (2) and the groove teeth (3) are symmetrically distributed on both sides of the hollow cavity.

6. A self-supporting channel heat pipe based on selective laser melting as claimed in claim 1, characterized in that: The groove width of the groove teeth (3) is 0.60-1.00 mm.

7. A self-supporting channel heat pipe based on selective laser melting as claimed in claim 1, characterized in that: The groove depth of the groove teeth (3) is 0.80-1.20 mm.

8. A method for preparing a self-supporting channel heat pipe based on laser selective melting, characterized in that: The self-supporting channel heat pipe according to any one of claims 1 to 7 is prepared by an additive manufacturing method, which specifically comprises the following steps: S1 modeling, build the CAD model of the parts to be processed and obtain the STL format file; S2 slicing, importing the STL format model file obtained in step S1 into the forming control device, slicing the model using special software to obtain part contour information; S3 plans the scanning path and sets the forming process parameters based on step S2; S4 pre-powder, using a scraper or powder roller to spread a uniform layer of powder on the substrate or formed parts; S5 forming, according to the graphic slice information obtained in step S2 and the forming parameters set in step S3, controlling the galvanometer to select and melt the metal powder to form a metallurgical bonding entity; S6: Powder is spread again and the laser beam is scanned; after the current layer is formed, the forming cylinder is lowered by a layer thickness, and the powder feeding cylinder is raised by a certain distance to continue spreading powder, and steps S4 and S5 are repeated until the part processing is completed.

9. The method for preparing a self-supporting channel heat pipe based on selective laser melting according to claim 8, characterized in that: The powder spreading thickness in step S4 is 0.1 mm.

10. The method for preparing a self-supporting channel heat pipe based on selective laser melting according to claim 8, characterized in that: In step S6, the laser beam power is 200 W, the spot diameter is 0.08 mm, the scanning speed is 1400-3000 mm / s, and the scanning interval is 0.06-0.10 mm.

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