A laser forming method of an aero-engine casing

Abstract

The application belongs to the technical field of laser cladding, and provides a laser forming method for an aero-engine casing, which is used for solving the problems of low machining precision and low yield rate when the casing is machined by laser cladding technology. The application comprises the following steps: (1) preparing a graphite profiling tool, wherein the graphite profiling tool is formed with a forming cavity which is matched with the shape and size of the casing; and (2) fixing the graphite profiling tool on a rotary worktable of a coaxial powder feeding laser cladding device, and gradually forming the casing in the forming cavity of the graphite profiling tool by a laser cladding process. After the casing is formed, the graphite tool can be quickly disassembled and removed, which greatly improves the part forming precision, size stability and yield rate. After simple post-processing, the formed casing can meet the assembly requirements.

Description

Technical Field

[0001] This invention belongs to the field of laser cladding technology, specifically relating to a laser forming method for an aero-engine casing. Background Technology

[0002] As the "skeleton" of an aero-engine, the engine casing serves as the load-bearing and force-transmitting framework, safety barrier, and aerodynamic channel for internal engine components, making it an indispensable and crucial part of the aero-engine. However, due to the thin walls, large curved surfaces, and overhanging structures, the molding and processing of the casing is exceptionally difficult, mainly in the following aspects: (1) Since the casing is mostly thin-walled, large curved surface and overhang structure, traditional laser cladding requires a lot of support (such as metal support, ceramic support, resin support, plaster support, etc.). These support materials are not only difficult to remove, but also very easy to scratch the surface of the casing during the removal process.

[0003] In addition, the support material also has problems such as poor high temperature resistance, easy adhesion, high hardness, difficult processing, and high cost, which in turn affect the processing efficiency of the casing and cannot meet the requirements of efficient casing forming.

[0004] (2) Due to the thin wall and weak rigidity of the casing, heat accumulation during laser cladding can easily lead to warping, poor roundness, and unstable dimensions, resulting in low forming accuracy and low yield.

[0005] (3) Traditional laser cladding + eight-axis linkage machining housing is difficult to process at right-angle overhangs of parts.

[0006] (4) Using 3D printing technology to make the casing is costly and wasteful for printing powder for large-sized thin-walled parts.

[0007] (5) When the casing is made by casting machine, defects such as porosity, looseness and coarse grains are easy to occur, and the density and mechanical properties are difficult to meet the high reliability requirements of aviation.

[0008] (6) Using traditional forging machines to manufacture the gate results in low material utilization, long processing cycle, thin walls that are easily deformed, and complex curved surfaces and overhanging structures that are difficult to form as a whole. In addition, the production cost is high and the manufacturing efficiency is low. Summary of the Invention

[0009] To address the problems of low processing accuracy and low yield in laser cladding technology for processing engine casings, this invention provides a laser forming method for aero-engine casings. The method uses graphite contouring fixtures to provide stable support for the casing, which not only constrains the casing and improves processing accuracy and yield, but also allows for rapid removal of the graphite contouring fixtures after processing, avoiding scratches on the casing surface.

[0010] To solve the technical problem, the technical solution adopted by this invention is as follows: A laser forming method for an aircraft engine casing includes: (1) Prepare a graphite molding tooling, wherein the graphite molding tooling has a molding cavity that matches the shape and size of the casing; (2) Fix the graphite profiling fixture on the rotary table of the coaxial powder feeding laser cladding equipment, and gradually form the casing in the forming cavity of the graphite profiling fixture through the laser cladding process.

[0011] In some embodiments, the graphite contouring tooling is a detachable, modular structure.

[0012] In some embodiments, the graphite profiling tooling includes multiple graphite profiling tooling segments divided along the length of the casing. Adjacent graphite profiling tooling segments are detachably connected, and each graphite profiling tooling segment together forms a molding cavity that matches the shape and size of the casing. Each graphite profiling tooling segment is a detachable assembly structure.

[0013] In some embodiments, when the molding cavity of the graphite contouring tooling is formed into a housing by laser cladding process: after the laser cladding of the molding cavity of the previous graphite contouring tooling section is completed, the next graphite contouring tooling section is spliced ​​at the front end of the previous graphite contouring tooling section and the laser cladding continues; this cycle is repeated until the laser cladding process is completed in the molding cavity to form the housing.

[0014] In some embodiments, the graphite contouring tooling is preheated and homogenized before laser cladding is performed in the forming cavity of the graphite contouring tooling.

[0015] In some embodiments, the graphite profiling tool is pre-treated before being clamped on the rotary table. The pre-treatment includes removing oil and impurities, drying, and deburring.

[0016] In some embodiments, the cladding powder used in the laser cladding process is TC4 alloy powder. Before laser cladding, the TC4 alloy powder is dried to remove moisture from the powder.

[0017] In the specific implementation process, the particle size of TC4 alloy powder is 38-53μm.

[0018] In some embodiments, the process parameters of the laser cladding process are: laser power 500-800W, scanning speed 4-6mm / s, powder feeding rate 2-5g / min, and overlap rate 53-57%; when laser cladding is performed in the forming cavity of the graphite contouring tool, the single-layer cladding thickness is 0.2-0.4mm, and the width of the heat-affected zone is ≤0.5mm.

[0019] In some embodiments, after the housing is formed by laser cladding in the molding cavity of the graphite contouring tooling and then naturally cooled to room temperature, the housing is obtained after the graphite contouring tooling is removed.

[0020] In some embodiments, the forming cavity of the graphite conforming tooling includes a first forming cavity for forming an inner casing support ring of an aero-engine, a second forming cavity for forming a middle casing flow equalization ring of an aero-engine, and a third forming cavity for forming an outer casing load-bearing ring of an aero-engine. The third forming cavity is located around the second forming cavity, and the second forming cavity is located around the first forming cavity.

[0021] Compared with the prior art, the present invention has the following beneficial effects: The laser forming method for an aero-engine casing of the present invention uses TC4 titanium alloy powder as the cladding material, graphite contouring tooling for surface constraint and support, and coaxial powder feeding laser cladding equipment. Through the coordinated design of process and materials, the aero-engine casing is formed. After forming, the graphite tooling can be quickly disassembled and removed, which greatly improves the forming accuracy, dimensional stability and yield of the parts. The formed part (i.e., the formed casing) can meet the assembly requirements after simple post-processing (i.e., small-scale deburring).

[0022] Targeting the diverse structural characteristics of casings, such as thin walls, complex curved surfaces, irregular shapes, holes, sandwich structures, and hollow layers, a graphite-based contouring tooling constraint forming system was pioneered. This system addresses industry pain points such as high manufacturing costs, long cycles, and difficult processing. In particular, it provides new processing and forming options for some traditionally unmachinable structures, greatly expanding the scope of structural design.

[0023] Since the present invention forms the casing directly through laser cladding, it can reduce or eliminate the welding structure of the casing, thereby reducing the deformation and welding risks caused by welding.

[0024] The segmented, detachable graphite contour tooling of this invention features high splicing accuracy, convenient assembly and disassembly, non-stick metal, no damage to workpiece, and significantly improved demolding efficiency.

[0025] The process of this invention is simple, stable and controllable, requires no complex equipment modification, is highly versatile, can be quickly adapted to the molding of different specifications of casings, is highly practical and easy to promote.

[0026] In summary, this invention utilizes graphite contouring tooling for surface constraint and support, combined with coaxial powder feeding laser cladding equipment, to achieve aircraft casing forming through the coordinated design of processes and materials; it can improve the finished product accuracy and yield of the casing, and reduce the manufacturing cost and cycle of the casing. Attached Figure Description

[0027] Figure 1This is a schematic diagram of the main view structure of an embodiment of the graphite contouring tooling of the present invention. In this schematic diagram, the graphite contouring tooling is composed of three graphite contouring tooling segments spliced ​​together. Figure 2 This is a top view structural schematic diagram of an embodiment of the graphite contouring tooling of the present invention; Figure 3 This is a schematic diagram of a casing manufactured using the present invention; Reference numerals: 1. Graphite contouring fixture; 11. Graphite contouring fixture section; 111. Graphite contouring fixture unit; 112. Connector; 101. Inner casing support ring graphite contouring fixture; 102. Middle casing flow equalization ring graphite contouring fixture; 103. Outer casing load-bearing ring graphite contouring fixture; 2. Molding cavity; 21. First molding cavity; 22. Second molding cavity; 23. Third molding cavity; 3. Graphite rod or graphite block. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The described embodiments are some, but not all, of the embodiments of the present invention. The following embodiments are only for specific illustration of the implementation methods of the present invention and do not limit the scope of protection of the present invention.

[0029] Referring to the accompanying drawings, the laser forming method for the aircraft engine casing of the present invention includes: (1) Prepare a graphite molding tool 1, wherein the graphite molding tool 1 forms a molded cavity 2 that matches the shape and size of the casing; In the specific implementation process, the preparation method of graphite contouring tooling 1 includes: using 3D software (such as UG) to perform offset contouring design on the 3D model of the aero-engine casing, generating a 3D model of graphite contouring tooling with inner and outer double-sided constraints, wherein the inner and outer double-sided constraints are used to form the forming cavity 2; then, the machining program is generated by CNC programming software, and the graphite blank is precision milled by CNC milling machine to obtain graphite contouring tooling 1 with forming cavity 2.

[0030] (2) Fix the graphite profiling tool 1 on the rotary table of the coaxial powder feeding laser cladding equipment, and gradually form the casing in the forming cavity of the graphite profiling tool through the laser cladding process.

[0031] The laser forming method for an aero-engine casing of the present invention uses TC4 titanium alloy powder as the cladding material, graphite contouring tooling for surface constraint and support, and coaxial powder feeding laser cladding equipment. Through the coordinated design of process and materials, the aero-engine casing is formed. After forming, the graphite tooling can be quickly disassembled and removed, which greatly improves the forming accuracy, dimensional stability and yield of the parts. The formed part (i.e., the formed casing) can meet the assembly requirements after simple post-processing (i.e., small-scale deburring).

[0032] Addressing the diverse structural characteristics of casings, such as thin walls, complex curved surfaces, irregular shapes, holes, sandwich structures, and hollow layers, a novel graphite-based contour-containment forming method was pioneered. This method solves industry pain points such as high manufacturing costs, long production cycles, and difficult processing. In particular, it provides new processing and forming options for some traditionally unmachinable structures, greatly expanding the scope of structural design.

[0033] Since the present invention forms the casing directly through laser cladding, it can reduce or eliminate the welding structure of the casing, thereby reducing the deformation and welding risks caused by welding.

[0034] The segmented, detachable graphite contour tooling of this invention features high splicing accuracy, convenient assembly and disassembly, non-stick metal, no damage to workpiece, and significantly improved demolding efficiency.

[0035] The process of this invention is simple, stable and controllable, requires no complex equipment modification, is highly versatile, can be quickly adapted to the molding of different specifications of casings, is highly practical and easy to promote.

[0036] In summary, this invention utilizes graphite contouring tooling for surface constraint and support, combined with coaxial powder feeding laser cladding equipment, to achieve aircraft casing forming through the coordinated design of processes and materials; it can improve the finished product accuracy and yield of the casing, and reduce the manufacturing cost and cycle of the casing.

[0037] Combined with appendix Figure 1 and attached Figure 2 In some embodiments, the graphite contouring tool 1 is a detachable assembly structure.

[0038] Combined with appendix Figure 1 and attached Figure 2 The graphite profiling tool 1 includes multiple graphite profiling tooling sections 11 divided along the length of the casing. Adjacent graphite profiling tooling sections 11 are detachably connected. Each graphite profiling tooling section 11 together forms a molded cavity 2 that matches the shape and size of the casing. Each graphite profiling tooling section 11 is a detachable assembly structure.

[0039] In the specific implementation process, each graphite contouring tooling segment 11 is spliced ​​together from multiple graphite contouring tooling units 111. For example, each graphite contouring tooling segment 11 is spliced ​​together from 4 or 6 graphite contouring tooling units 111 through connectors 112. The graphite contouring tooling segments 11 are spliced ​​together through connectors 112, thus forming a complete graphite contouring tooling 1.

[0040] In the specific implementation process, in order to facilitate the splicing between graphite contour tooling units 111 and between different graphite contour tooling sections 11, the connecting parts 112 are common bolts and nuts.

[0041] The specific number of segments of the graphite profiling fixture 1 (i.e., how many graphite profiling fixture segments a single graphite profiling fixture consists of) can be comprehensively determined based on the length (or height) of the housing, ultimately ensuring that the laser cladding equipment can perform laser cladding processing within the forming cavity 2. Those skilled in the art will understand this, and it will not be elaborated further here.

[0042] In the specific implementation process, the length (or height) of each graphite contour tooling section 11 is 1.8-2.2mm, so as to avoid the forming cavity 2 of the graphite contour tooling section 11 being too deep and affecting the forming quality of laser cladding, thereby ensuring the quality of the laser cladding formed casing.

[0043] In some embodiments, when the molding cavity 2 of the graphite contouring tooling 1 is formed into a housing by laser cladding process: after the laser cladding of the molding cavity of the previous graphite contouring tooling section 11 is completed, the next graphite contouring tooling section 11 is spliced ​​at the front end of the previous graphite contouring tooling section 11 and the laser cladding continues; this cycle is repeated until the laser cladding process is completed in the molding cavity to form the housing.

[0044] In the specific implementation process, when splicing the next section of graphite contour tooling 11, the laser cladding equipment should maintain laser irradiation, but not spray cladding powder, so as to maintain the temperature.

[0045] Since laser cladding is performed inside the forming cavity 2, while the splicing of adjacent graphite contouring tooling sections is performed outside the graphite contouring tooling 1, the splicing of graphite contouring tooling section 11 and the laser cladding process do not conflict with each other.

[0046] In some embodiments, the graphite contouring tooling is preheated and homogenized before laser cladding is performed inside the forming cavity of the graphite contouring tooling. Preheating and homogenization allow the casing to be uniformly preheated during the laser cladding process, significantly reducing thermal stress and temperature gradient during cladding, and effectively suppressing defects such as warping deformation, out-of-roundness, cracks, and porosity in the thin-walled parts of the casing.

[0047] In the specific implementation process, induction heating can be used to preheat and homogenize the graphite contouring tooling as a whole. Specifically, the preheating temperature of the graphite contouring tooling is 300-350℃, and then the graphite contouring tooling is kept at 300-350℃ for homogenization.

[0048] In laser cladding, an argon atmosphere chamber is used. The chamber is filled with argon gas to ensure that the oxygen content is less than 0.1 ppm. The need for argon protection during laser cladding is understood by those skilled in the art. However, for applications where materials are highly susceptible to oxidation, where high quality requirements for the cladding layer (such as porosity and inclusions) are necessary, or where cladding in air would lead to severe defects, an argon atmosphere chamber (also known as an argon protection chamber) is required.

[0049] Therefore, the preheating and homogenization treatment of the graphite contouring tool 1 of the present invention, as well as the laser cladding process performed in the forming cavity 2 of the graphite contouring tool 1, are all carried out in an argon atmosphere chamber (argon protection chamber).

[0050] In some embodiments, the graphite profiling fixture 1 is pre-treated before being clamped on the rotary table. The pre-treatment includes removing oil and impurities, drying, and deburring to ensure that the graphite profiling fixture 1 is clean and dry.

[0051] In some embodiments, the cladding powder used in the laser cladding process is TC4 alloy powder. Before laser cladding, the TC4 alloy powder is dried to remove moisture, thereby preventing the formation of pores during the cladding process.

[0052] In the specific implementation process, the particle size of TC4 alloy powder is 38-53μm.

[0053] In some embodiments, the process parameters of the laser cladding process are: laser power 500-800W, scanning speed 4-6mm / s, powder feeding rate 2-5g / min, and overlap rate 53-57%. Specifically, when the laser power is below 500W, the molten pool temperature is insufficient, the cladding powder (i.e., TC4 alloy powder) does not melt sufficiently, and incomplete fusion defects are easily generated; while when the laser power is above 800W, the heat input is too large, and the thin-walled structure of the casing is prone to warping and deformation.

[0054] In practical implementation, when performing laser cladding within the forming cavity of the graphite contouring fixture, the single-layer cladding thickness is 0.2-0.4 mm, and the heat-affected zone width is ≤0.5 mm. The preferred scanning speed is 4-6 mm / s, matched with the laser power to ensure that the single-layer cladding thickness is controlled within 0.2-0.4 mm and the heat-affected zone width is ≤0.5 mm, effectively controlling the heat accumulation effect.

[0055] In the specific implementation process, taking the forming cavity 2 of the graphite contour tooling 1 as the boundary, TC4 alloy powder is fed into the laser melting pool through the coaxial powder feeding system, and the casing is gradually formed in the forming cavity of the graphite contour tooling by a layer-by-layer cladding deposition method.

[0056] In some embodiments, after the housing is formed by laser cladding within the molding cavity of a graphite contouring fixture and then naturally cooled to room temperature, the housing is obtained after removing the graphite contouring fixture. By fully utilizing the non-wetting property of graphite and titanium alloy, the formed housing can be removed without damage. Compared to existing technologies using traditional materials such as metal supports, ceramic supports, resin supports, and plaster supports, graphite has significant advantages as a contouring support material: high temperature resistance, no deformation, and suitability for the high-temperature conditions of laser cladding; it does not wet the titanium alloy metal, allowing for easy demolding without damaging the part surface; even if some parts adhere to the part surface, they can be easily removed through simple machining.

[0057] Furthermore, graphite profiling fixtures offer advantages such as easy processing, rapid profilometry of complex curved surfaces, high forming accuracy, and good thermal stability. Their close fit with the part (i.e., the housing) increases heat dissipation area, reducing thermal stress and deformation. They are also low-cost, economical, and highly practical. For graphite profiling fixtures where parts are difficult to remove directly after forming, demolding can be achieved by hammering or crushing due to the soft and brittle nature of graphite.

[0058] Combined with appendix Figure 1 Appendix Figure 2 and attached Figure 3 In some embodiments, the forming cavity 2 of the graphite conforming tooling 1 includes a first forming cavity 21 (adapted to the inner casing support ring 01) for forming the inner casing support ring of the aero-engine, a second forming cavity 22 (adapted to the middle casing flow equalization ring 02) for forming the middle casing flow equalization ring of the aero-engine, and a third forming cavity 23 (adapted to the outer casing load-bearing ring 03) for forming the outer casing load-bearing ring of the aero-engine. The third forming cavity 23 is located around the second forming cavity 22, and the second forming cavity 22 is located around the first forming cavity 21.

[0059] In some embodiments, the graphite contouring fixture 1 is further equipped with a graphite rod 3 that is compatible with the flow equalization hole of the flow equalization ring in the middle casing. That is, the graphite contouring fixture is equipped with a graphite rod corresponding to the position of the flow equalization hole in the flow equalization ring in the middle casing. After the laser cladding is completed, the graphite rod can be removed to form the flow equalization hole.

[0060] In some specific implementation processes, the graphite contouring fixture 1 includes an inner casing support ring graphite contouring fixture 101, a middle casing flow equalization ring graphite contouring fixture 102, and an outer casing load-bearing ring graphite contouring fixture 103. The outer casing load-bearing ring graphite contouring fixture 103 is fitted around the middle casing flow equalization ring graphite contouring fixture 102, while the middle casing flow equalization ring graphite contouring fixture 102 is fitted around the inner casing support ring graphite contouring fixture 101. That is to say, the inner casing support ring graphite contouring fixture 101 (which is compatible with the inner casing support ring 101) The graphite contouring tooling 1 is composed of the inner casing support ring graphite contouring tooling 101, the inner casing flow equalization ring graphite contouring tooling 102 (which is compatible with the inner casing flow equalization ring 02) and the outer casing load-bearing ring graphite contouring tooling 103 (which is compatible with the outer casing load-bearing ring 03). The inner casing support ring graphite contouring tooling 101, the inner casing flow equalization ring graphite contouring tooling 102 and the outer casing load-bearing ring graphite contouring tooling 103 are respectively spliced ​​from multiple graphite contouring tooling segments 11, and each graphite contouring tooling segment 11 is spliced ​​from multiple graphite contouring tooling units 111.

[0061] In the specific implementation process, the forming cavity 2 of the graphite contour tooling 1 is determined according to the structural design of the casing, ensuring that the shape and size of the forming cavity 2 are compatible with those of the casing, which can be understood by those skilled in the art.

[0062] Correspondingly, when this invention is applied to holes in other types of casings, graphite rods or graphite blocks 3 of similar dimensions can also be provided to facilitate the formation of holes at corresponding positions on the casing. In other words, the graphite profile tooling and the matching graphite rods or graphite blocks 3 together form a constraint on the casing.

[0063] It should be understood that the above description of the preferred embodiments is quite detailed, but it should not be considered as a limitation on the scope of protection of this invention. Those skilled in the art, under the guidance of this invention, can make substitutions or modifications without departing from the scope of protection of the claims of this invention, and all such substitutions or modifications fall within the scope of protection of this invention. The scope of protection of this invention should be determined by the appended claims.

Claims

1. A laser forming method for an aero-engine casing, characterized in that, include: (1) Prepare a graphite molding tool (1), which has a molding cavity (2) that matches the shape and size of the casing. (2) Fix the graphite profiling fixture (1) on the rotary table of the coaxial powder feeding laser cladding equipment, and gradually form the casing in the forming cavity (2) of the graphite profiling fixture (1) through the laser cladding process.

2. The laser forming method for an aero-engine casing according to claim 1, characterized in that, The graphite profiling fixture (1) is a detachable assembly structure.

3. The laser forming method for an aero-engine casing according to claim 2, characterized in that, The graphite contouring tooling (1) includes multiple graphite contouring tooling segments (11) divided along the length of the casing. Adjacent graphite contouring tooling segments (11) are detachably connected. Each graphite contouring tooling segment (11) together forms a molded cavity (2) that matches the shape and size of the casing. Each graphite contouring tooling segment (11) is a detachable assembly structure.

4. The laser forming method for an aero-engine casing according to claim 3, characterized in that, When the molding cavity (2) of the graphite molding tooling (1) is formed into a casing by laser cladding process: after the laser cladding of the molding cavity of the previous graphite molding tooling section (11) is completed, the next section of graphite molding tooling section (11) is spliced ​​at the front end of the previous section of graphite molding tooling section (11) and the laser cladding continues; this cycle continues until the laser cladding process is completed in the molding cavity (2) to form the casing.

5. The laser forming method for an aero-engine casing according to any one of claims 1-4, characterized in that, Before performing laser cladding in the forming cavity (2) of the graphite contouring tooling (1), the graphite contouring tooling (1) is preheated and homogenized.

6. The laser forming method for an aero-engine casing according to any one of claims 1-4, characterized in that, Before the graphite profiling fixture (1) is clamped on the rotary worktable, the graphite profiling fixture (1) is pre-treated, and the pre-treatment includes removing oil and impurities, drying and deburring.

7. The laser forming method for an aero-engine casing according to claim 1, characterized in that, The cladding powder used in the laser cladding process is TC4 alloy powder. Before laser cladding, the TC4 alloy powder is dried to remove moisture from the powder.

8. The laser forming method for an aero-engine casing according to claim 1, characterized in that, The process parameters of the laser cladding process are as follows: laser power 500-800W, scanning speed 4-6mm / s, powder feeding rate 2-5g / min, and overlap rate 53-57%; when laser cladding is performed in the forming cavity (2) of the graphite contouring tool (1), the single-layer cladding thickness is 0.2-0.4mm, and the width of the heat-affected zone is ≤0.5mm.

9. The laser forming method for an aero-engine casing according to claim 1, characterized in that, After the casing is formed by laser cladding in the molding cavity (2) of the graphite molding tooling (1), it is naturally cooled to room temperature, and the casing is obtained after the graphite molding tooling (1) is removed.

10. The laser forming method for an aero-engine casing according to claim 1, characterized in that, The forming cavity (2) of the graphite conforming tooling (1) includes a first forming cavity (21) for forming the inner casing support ring of the aero-engine, a second forming cavity (22) for forming the middle casing flow equalization ring of the aero-engine, and a third forming cavity (23) for forming the outer casing load-bearing ring of the aero-engine. The third forming cavity (23) is located around the second forming cavity (22), and the second forming cavity (22) is located around the first forming cavity (21).

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