Selective laser melting forming method for two-stage axial swirler with complex structure

Abstract

The invention provides a selective laser melting forming method for a two-stage axial swirler of a complex structure. The selective laser melting forming method comprises the following steps that a blank model is made; placing parts and adding supports; the most end area of an outlet of a part convergence section is of a uniform annular expanding structure, at the moment, no matter the swirler rotates by any angle along a center shaft, the condition that the part printing growth direction is opposite to the scraper direction exists, and in other words, the scraper collision and powder bouncing risks exist at the position. Forming process; a small-layer-thickness, low-power and multi-time outer contour scanning process is adopted in a cavity and blade height area of a swirler part. A uniform annular expansion type structure height area is arranged at the most end part area of an outlet of a convergence section of the part, and a lower powder scraping speed is adopted. The method has the advantages that the surface roughness requirement in the blade and the cavity in the forming process is met, meanwhile, powder cleaning is more thorough after printing is completed, part scraper collision and powder bouncing risks are avoided, meanwhile, support removal is facilitated, and compared with a casting process, the product percent of pass is effectively increased.

Description

Technical Field

[0001] The invention relates to the field of metal additive manufacturing, and in particular to a laser selective melting forming method for a two-stage axial vortex flow device with a complex structure. Background Art

[0002] The vortex finder is a rotating body structure with reverse double-stage blades evenly distributed in the inner cavity. The parts are located at the head of the flame tube. The functions of the vortex finder parts in aircraft engines are: first, to form a low-pressure recirculation zone at the head of the flame tube to stabilize the flame; second, to generate vortex air in the combustion chamber to achieve the purpose of full combustion of the fuel by mixing the fuel and air.

[0003] In the traditional vortex finder manufacturing process, a single mold can only produce one product, with low production efficiency and long production cycle. Due to the sudden change of cross-sectional area in the vortex finder parts and the complex structure, it is easy to have defects such as looseness and insufficient pouring, resulting in a low qualified rate of the casting process.

[0004] Additive manufacturing technology, also known as 3D printing technology, is based on digital drive and achieves three-dimensional near-net shape of objects through layer-by-layer deposition. There are many types of metal additive manufacturing technologies, among which laser selective melting forming technology can realize the preparation of complex structural parts and is widely used in the field of aviation engines.

[0005] The present invention adopts laser selective melting forming technology to prepare vortex finder parts. This method can make up for the shortcomings of traditional casting processes, has certain advantages in forming difficult-to-process alloys and complex structure parts with complex structure casting processes, and can realize the preparation of complex structure two-stage axial vortex finders. The present invention fully considers the sufficient powder cleaning inside the vortex finder parts, the scraper buffering in the forming process of the reverse scraper part of the rotating body structure, and the high surface finish printing of the part cavity and blades. Summary of the invention

[0006] The purpose of the present invention is to provide a laser selective melting forming method suitable for a two-stage axial vortex flow device with a complex structure, to transition from a traditional process to a laser selective melting forming process, and to achieve high-quality manufacturing of nozzle-type parts through an additive manufacturing process. In addition, the present invention takes into account the scraper collision during the printing process, the high-precision printing of the cavity and the blades, the powder cleaning after printing, and designs special supports and specific printing process parameters according to the working conditions and structural characteristics of the parts.

[0007] The present invention provides a method for laser selective melting of a complex structure two-stage axial vortex generator, comprising the following steps: (1) preparing a blank model;

[0008] According to the design requirements, the upper and lower surfaces of the installation edge need to be assembled with other parts, and the surface roughness requirement is Ra1.6. Normal printing of laser selective melting cannot guarantee this surface roughness. Therefore, a certain margin is reserved on the upper and lower surfaces of the installation edge. The surface roughness is improved by machining the installation edge margin later.

[0009] (2) Parts placement and support addition

[0010] When the outlet end of the convergent section of the vortex finder part is placed vertically downward, there is a large area of ​​suspended surface inside the cavity, and the height distance is large. A large number of supports need to be added, and the support is deep inside the part. It is relatively difficult to remove the support and polish the support surface. When the outlet end of the convergent section of the vortex finder part is placed vertically upward, the blades inside it are at an angle of 45°-65° with the horizontal direction. If it is greater than 45°, self-forming can be achieved. At this time, the inner ring channel edge, outer ring channel edge, inner ring blade edge, and outer ring blade edge of the vortex finder need to add support, but the support height is small and it is easy to remove later. This placement method is feasible. The support adopts full grid support. The contact surface between the grid support and the part is serrated, and the part is inserted 0.1mm, which is convenient for removal and can ensure a firm connection. In order to effectively remove the residual powder during the printing process, the side surface of the grid support is set as a hollow structure. In addition, on each annular surface composed of the lower support, self-supporting powder cleaning hole structures are set at an average interval of a certain angle along the circle. The above two measures ensure that the parts are thoroughly cleaned of powder. The self-supporting wall thickness of the conformal cavity structure in the present invention is 1-2 mm.

[0011] The end area of ​​the part convergence section outlet presents a uniform annular expansion structure. At this time, no matter how the vortex finder rotates along the central axis, the part printing growth direction is opposite to the scraper direction, that is, there is a risk of scraper collision and powder rebound. To alleviate this risk, multiple inclined plate supports are set in the risk area. The inclination direction of the support is the same as the scraper powder spreading direction, which can effectively alleviate the impact of the scraper on the powder and parts, ensuring that there is no printing risk in this area.

[0012] (3) Forming process

[0013] The specific part setting parameters are shown in Table 1.

[0014] Table 1 Main process parameters of vortex laser selective melting

[0015]

[0016] During the part forming process, the part scanning path is to scan the inner core first and then the outer contour; the plate-shaped solid support only scans the inner core; the grid support is only a single-pass interlayer scan. The above scanning method can ensure the forming accuracy and forming efficiency of the part, and the support is also easier to remove, which improves manufacturing efficiency. In the cavity and blade height area of ​​the vortex flow device part, a small layer thickness, low power and multiple outer contour scanning process is adopted. In the end area of ​​the uniform annular expansion structure height area at the outlet of the convergent section of the part, a lower scraping speed is adopted.

[0017] The present invention provides a laser selective melting forming solution for a two-stage axial vortex flow device with a complex structure. With the corresponding placement method, support setting, process parameter control, etc., the surface roughness requirements of the blades and the cavity during the forming process can be guaranteed. At the same time, the powder can be cleaned more thoroughly after printing, avoiding the risks of scraper collision and powder rebound of parts, and facilitating the removal of supports.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] The surface roughness requirements of the blades and the cavity are guaranteed during the forming process. At the same time, the powder is cleaned more thoroughly after printing, avoiding the risks of scraper collision and powder rebound of parts. It is also convenient to remove the support, which effectively improves the product qualification rate compared with the casting process. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments:

[0021] Figure 1 : Schematic diagram of vortex flow device parts;

[0022] Figure 2 Side view of vortex finder parts;

[0023] Figure 3 : Schematic diagram of the internal cavity and blades of the vortex finder;

[0024] Figure 4 : Schematic diagram of adding allowance to eddy current collector parts;

[0025] Figure 5 : Schematic diagram of adding support for vortex flow generator parts;

[0026] Figure 6 : Schematic diagram of the self-supporting conformal cavity structure of vortex flow device parts. DETAILED DESCRIPTION

[0027] The present invention will be further explained below in conjunction with specific implementation plans, but the present invention is not limited thereto. The structures, proportions, sizes, etc. illustrated in the drawings of the specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the restrictive conditions under which the present invention can be implemented. Therefore, they have no substantive technical significance. Any structural modification, change in proportional relationship or adjustment of size should still fall within the scope of the technical content disclosed by the present invention without affecting the effects and purposes that can be achieved by the present invention.

[0028] like Figure 1-3 As shown, the vortex finder is a rotating body structure as a whole. The part has an inner ring channel and an outer ring channel. The inner ring blades and the outer ring blades are inside the channel. The middle of the part is the installation edge, and the bottom of the part is the convergent section outlet.

[0029] Step 1: Use modeling software to perform 3D modeling of the vortex finder, and stretch the upper and lower surfaces of the mounting edge by 1 mm respectively, that is, the mounting edge of the part is thickened by 2 mm. Figure 4 shown.

[0030] Step 2: Import the part digital model into the model processing software to add support.

[0031] The laser selective melting forming technology is used to manufacture the part. The part placement and overall support addition scheme are as follows: Figure 5 As shown, the outlet end of the convergent section of the vortex finder part is placed vertically upward, and supports are added to the edges of the inner ring channel, the outer ring channel, the inner ring blades, and the outer ring blades of the vortex finder. The support adopts full grid support. The contact surface between the grid support and the part is serrated and inserted into the part by 0.1mm. The side surface of the grid support is set as a hollow structure. In addition, on each annular surface composed of the lower support, a self-supporting powder cleaning hole structure is set at an average interval of 30°-60° along the circle, as shown in FIG. Figure 6 As shown, the above two measures ensure that the parts are completely cleaned of powder, and the thickness of the self-supporting structure is 2mm.

[0032] A number of inclined plate supports are set at the end of the convergence section of the part. The inclination direction of the support is the same as the direction of the scraper spreading the powder, which can effectively alleviate the impact of the scraper on the powder and parts, ensuring that there is no printing risk at this location. The thickness of the inclined plate support is 3-7mm.

[0033] Step 3: Use the software to slice and fill the vortex flow machine model after adding supports, set specific process parameters, and generate a processing file in .cli format.

[0034] The specific printing parameters are shown in Table 2.

[0035] Table 2 Main process parameter settings of vortex laser selective melting

[0036]

[0037] The first layer of powder formed by laser selective melting is exposed and sintered twice to ensure that the part entity is fully connected to the substrate after laser sintering. The powder spreading ratio of the first 5 layers of forming is set to 300%, and the powder spreading ratio after that is set to 150%; at the beginning of each layer of powder spreading, the scanning direction rotates 67° clockwise to minimize the number of overlaps, prevent internal stress and cracks in the parts, and ensure the accuracy of part forming.

[0038] During the part forming process, the part scanning path is to scan the core first and then the outer contour; the plate-shaped solid support only scans the core; the grid support is only a single-pass interlayer scan. The above scanning method can ensure the forming accuracy and forming efficiency of the part, and the support is also easier to remove, which improves manufacturing efficiency. In the cavity and blade height area of ​​the vortex flow device part, a low layer thickness of 30μm, a low power of 110W and 3 outer contour scanning processes are adopted. In the end area of ​​the outlet of the convergent section of the part, a uniform annular expansion structure height area is formed, and a powder scraping speed of 60mm / s is adopted.

[0039] Step 4: Import the processing file described in step 3 into the laser selective melting forming equipment to form the parts.

[0040] Step 5: Clean the powder on the surface of the formed parts and the support. Use a rubber hammer to knock on the substrate, and then use an air gun to clean the powder holes. Repeat the knocking and air blowing process until the powder is completely cleaned.

[0041] Step 6: Perform stress relief annealing on the formed body. The heat treatment system is: 600-700℃, keep warm for 1-3h, and cool to room temperature with Ar2 gas.

[0042] Step 7: Use wire cutting to separate the support from the substrate and the parts from the support.

[0043] Step 8: Manually remove the support on the parts. During the support removal process, the parts must be prevented from deformation and must not be damaged or bumped.

[0044] Step nine: Solution treat the vortex finder parts, the heat treatment system is: 1150 ~ 1250 ℃, keep warm for 1 ~ 3h, and cool to room temperature with Ar2 gas.

[0045] Step 10: The surface of the part is polished as a whole, and there must be no defects visible to the naked eye on the surface of the part.

[0046] Step 11: Sandblast the surface of the parts evenly. No stains, bumps or scratches are allowed on the surface of the parts.

[0047] Step 12: Machine the mounting edge of the part to increase the allowance.

[0048] Step 13: Ultrasonic cleaning of the surface of the parts.

[0049] Matters not covered by the present invention are known technologies.

[0050] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A laser selective melting forming method for a complex structure two-stage axial vortex generator, characterized in that: The following steps are involved: (1) Blank model preparation The upper and lower surfaces of the installation edge need to be assembled with other parts. A certain margin is reserved on the upper and lower surfaces of the installation edge. The surface roughness can be improved by machining the margin of the installation edge later. (2) Parts placement and support addition When the outlet end of the convergent section of the vortex flow device part is placed vertically downward, there is a large area of ​​suspended surface inside the cavity, and the height distance is large, so a large number of supports need to be added, and the supports penetrate deep into the part, making it relatively difficult to remove the supports and grind the support surfaces; when the outlet end of the convergent section of the vortex flow device part is placed vertically upward, the blades inside it form an angle of 45°-65° with the horizontal direction, and self-forming can be achieved when the angle is greater than 45°; the support adopts full grid support, and the contact surface between the grid support and the part is serrated, and the part is inserted 0.1mm, which is convenient for removal while ensuring a firm connection; the side surface of the grid support is set as a hollow structure, and self-supporting powder cleaning hole structures are set at an average interval of a certain angle along the circle of each annular surface composed of the lower support. The above two measures ensure that the parts are thoroughly cleaned of powder; The end area at the outlet of the convergent section of the part presents a uniform annular expansion structure. At this time, no matter how the vortex finder rotates along the central axis, the printing growth direction of the part is opposite to the scraper direction, that is, there is a risk of scraper collision and powder rebound. To alleviate this risk, multiple inclined plate supports are set in the risk area. The inclination direction of the support is the same as the scraper powder spreading direction, which can effectively alleviate the impact of the scraper on the powder and parts, ensuring that there is no printing risk at this location. (3) Forming process During the part forming process, the part scanning path is to scan the inner core first and then the outer contour; the plate-shaped solid support only scans the inner core; the grid support only scans a single layer; In the cavity and blade height area of ​​the vortex finder part, a small layer thickness, low power and multiple outer contour scanning processes are adopted; in the end area of ​​the convergent section outlet of the part, which is a uniform annular expansion structure height area, a lower scraping speed is adopted.

2. The method for forming a two-stage axial vortex flow device with a complex structure by laser selective melting according to claim 1, characterized in that: The (2) parts placement and support addition, the self-supporting wall thickness of the conformal cavity structure is 1-2mm.

3. The method for forming a two-stage axial vortex flow device with a complex structure by laser selective melting according to claim 1, characterized in that: In the forming process (3), the endmost area at the outlet of the convergent section of the part presents a uniform annular expansion structure height area, and a powder scraping speed of 50-70 mm / s is adopted.

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