Method for machining a gas turbine casing and aircraft engine

Abstract

This invention discloses a machining method for gas turbine casings and an aero-engine, comprising the following steps: obtaining a workpiece blank; rough machining the shape of the workpiece; forming a first support surface on the small end face of the rough-machined workpiece; forming a second support surface on the large end face of the rough-machined workpiece, leaving machining allowance; semi-finishing the large end face of the workpiece to form a machining reference surface; supporting the second support surface, semi-finishing the small end face and inner circumferential end groove of the workpiece; supporting the first support surface, semi-finishing the large end face and inner circumferential hook groove of the workpiece; supporting the first support surface, finish milling the inner ring edge; supporting the second support surface, finish machining the outer circular film holes; spraying; precision turning; electrical discharge machining. Based on this optimized machining method, the process route solves the problems of long machining cycles and part deformation in gas turbine casing parts, and adopts more reasonable cutting parameters, resulting in a limited improvement in the machining quality and cutting efficiency of the parts.

Description

Technical Field

[0001] This invention relates to the field of aero-engine machining technology, and in particular, to a machining method for a gas turbine casing and an aero-engine. Background Technology

[0002] The gas turbine casing is used to assemble the gas turbine guide vanes and turbine outer rings. Its complex structure makes it prone to tool interference during machining, and its poor overall rigidity makes it susceptible to deformation. The gas turbine casing for a certain type of engine is made of a high-temperature alloy. The part has a total height of approximately 116mm, a maximum outer diameter of approximately Φ330mm, and its thinnest point is located in the middle, with a wall thickness of approximately 2mm. This structure results in poor rigidity, leading to low dimensional accuracy rates at critical locations such as mounting edges, precision stops, precision stop roundness, mounting edge flatness, and mounting edge parallelism due to machining deformation (see attached diagram for details). Figure 1 (As shown). Simultaneously, there are 8 slots that are assembled with the gas turbine guide. The slots are approximately 17mm wide and 5mm deep. The traditional machining method for these slots is to use electrical discharge machining (EDM) to process each slot individually. This method results in rapid electrode wear, low machining efficiency, and poor machining quality, making it difficult to meet the part machining requirements.

[0003] The existing gas turbine casing machining process is as follows: CNC rough machining - stabilization treatment - CNC machining of the spraying groove position - spraying - CNC finish machining - CNC milling finish machining - EDM - fitter work - inspection. Due to part deformation during the cutting process, the existing process cannot meet the part's precision requirements. Specifically, the precision stop dimensions, roundness, flatness, parallelism of the mounting edge, and the eight slots at the large end of the part cannot meet the precision requirements due to cutting deformation.

[0004] Therefore, how to effectively improve the machining quality of gas turbine casings, solve the problem of cutting deformation of parts, and improve the machining efficiency and quality of parts are the technical problems that need to be solved at present. Summary of the Invention

[0005] This invention provides a machining method for gas turbine casings and an aero-engine, to solve the technical problem that the machining accuracy of gas turbine casings and similar workpieces cannot be met due to cutting deformation in the prior art.

[0006] The technical solution adopted in this invention is as follows:

[0007] A method for machining a gas turbine casing includes the following steps:

[0008] S1. Obtain the workpiece blank, rough machine the shape of the workpiece, the small end face of the rough machined workpiece forms the first support surface, the large end face of the rough machined workpiece forms the second support surface, leaving machining allowance.

[0009] S2. The large end face of the semi-finished workpiece forms the machining reference surface;

[0010] S3. Supported by the second support surface, the small end face and inner circumferential end groove of the semi-finished workpiece; supported by the first support surface, the large end face and inner circumferential hook groove of the semi-finished workpiece.

[0011] S4. Support the first support surface and precision mill the inner ring lace edge;

[0012] S5. Support the second support surface and finish the outer circular air film hole;

[0013] S6. Spraying;

[0014] S7. Fine machining;

[0015] S8. Electrical Discharge Machining.

[0016] As a further improvement to the above technical solution, in step S1, the shape of the rough-machined workpiece includes the outer ring hook groove of the rough-machined workpiece. When rough-machined the outer ring hook groove, the tool is mounted by using a transfer tool holder in conjunction with a square tool holder, and the finish turning command is selected to machine it in one cut.

[0017] As a further improvement to the above technical solution, in step S1, after rough machining the outer ring hook groove, the side margin of the outer ring hook groove is 0.15mm and the bottom margin of the outer ring hook groove is 0.05mm.

[0018] As a further improvement to the above technical solution, step S7 includes:

[0019] S71. Support the second support surface and precision machine the small end face of the workpiece;

[0020] S72. Support the first support surface and precision machine the outer ring hook groove of the large end face and the inner circumference of the workpiece.

[0021] S73. Support the first support surface and precision mill the workpiece's slot.

[0022] As a further improvement to the above technical solution, in step S72, when precision machining the outer ring hook groove on the inner circumference surface of the workpiece, a precision machining command is selected, and after machining the radial dimension of the outer ring hook groove to the required position, the width dimension is machined.

[0023] As a further improvement to the above technical solution, step S8 includes: supporting the second support surface and the positioning groove of the inner mounting edge of the workpiece for electrical discharge machining.

[0024] As a further improvement to the above technical solution, in step S8, the positioning groove of the workpiece is precision-machined using an electrical discharge fixture and machining components. The electrical discharge fixture includes:

[0025] The first base plate is used for positioning and mounting on the electrical discharge machining tool;

[0026] The first positioning plate is used for positioning and mounting on the first base plate. The first positioning plate has a first positioning groove for cooperating with the mounting edge of the workpiece.

[0027] The first pressure plate is connected to the first base plate and is used to press against the end face of the mounting edge of the workpiece to press and fix the workpiece onto the first positioning plate.

[0028] As a further improvement to the above technical solution, the processing component includes a zero-point positioning device, an electrode disk, and electrode heads uniformly arranged circumferentially on the electrode disk.

[0029] As a further improvement to the above technical solution, the processing method further includes: during rough machining, a machining allowance of 1.5mm is left on one side of the workpiece; during finish machining, a machining allowance of 0.5mm is left on one side of the workpiece.

[0030] According to another aspect of the present invention, an aircraft engine is also provided, which applies any of the above-described processing methods for gas turbine casings.

[0031] The present invention has the following beneficial effects:

[0032] This machining method, during the rough machining of the workpiece, forms a first support surface on its small end face and a second support surface on its large end face. In the semi-finishing stage, a fixture is used to support the second support surface while semi-finishing the small end face and inner circumferential end groove of the workpiece. This prioritizes ensuring the machining rigidity of difficult processes and increases the support surface to improve workpiece clamping reliability. In the semi-finishing stage, a fixture is used to support the first support surface while semi-finishing the large end face and inner circumferential hook groove of the workpiece. This improves the machining rigidity of the part and solves the problem of deformation caused by large cutting forces during rough machining of the outer ring hook groove in CNC turning. In the finishing stage, a fixture is used to support the small end face while finish milling the inner ring decorative edge, solving the problem of large cutting forces causing part deformation during CNC milling of the inner cavity decorative edge. Furthermore, the optimized process route based on this method solves the problems of long machining cycles and part deformation in gas turbine casing parts, and the use of more reasonable cutting parameters leads to a limited improvement in the machining quality and cutting efficiency of the parts.

[0033] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0034] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0035] Figure 1This is a half-sectional view of a gas turbine casing in the prior art;

[0036] Figure 2 This is a schematic diagram of the electrical discharge fixture structure according to a preferred embodiment of the present invention;

[0037] Figure 3 yes Figure 2 Sectional view along direction A;

[0038] Figure 4 This is a schematic diagram of the processing component structure according to a preferred embodiment of the present invention;

[0039] Figure 5 yes Figure 4 Sectional view along direction B;

[0040] Figure 6 This is a schematic diagram of the digital lathe fixture structure according to a preferred embodiment of the present invention;

[0041] Figure 7 yes Figure 6 Sectional view along line C;

[0042] Figure 8 This is a schematic diagram of the CNC milling fixture structure according to a preferred embodiment of the present invention;

[0043] Figure 9 yes Figure 8 Sectional view along direction D;

[0044] Figure 10 This is a process flow diagram of a preferred embodiment of the present invention;

[0045] 11. First base plate; 12. First positioning disc; 121. First positioning groove; 13. First pressure plate; 14. First double-ended stud; 15. First nut; 16. First adjusting support; 17. First limiting nut; 18. Diamond pin; 19. First fastening screw; 21. Electrode disc body; 22. Electrode head; 31. Second base plate; 32. Second positioning disc; 321. Second positioning groove; 33. Second pressure plate; 34. Second fastening screw; 35. Lifting ring; 36. Positioning bushing; 41. Third base plate; 42. Third positioning disc; 421. Positioning structure; 43. Third pressure plate; 44. Third fastening screw. Detailed Implementation

[0046] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0047] Reference Figures 1 to 10 A preferred embodiment of the present invention provides a method for machining a gas turbine casing, comprising the following steps:

[0048] S1. Obtain the workpiece blank, rough machine the shape of the workpiece, the small end face of the rough machined workpiece forms the first support surface, the large end face of the rough machined workpiece forms the second support surface, leaving machining allowance.

[0049] S2. The large end face of the semi-finished workpiece forms the machining reference surface;

[0050] S3. Supported by the second support surface, the small end face and inner circumferential end groove of the semi-finished workpiece; supported by the first support surface, the large end face and inner circumferential hook groove of the semi-finished workpiece.

[0051] S4. Support the first support surface and precision mill the inner ring lace edge;

[0052] S5. Support the second support surface and finish the outer circular air film hole;

[0053] S6. Spraying;

[0054] S7. Fine machining;

[0055] S8. Electrical Discharge Machining.

[0056] This machining method, during the rough machining of the workpiece, forms a first support surface on its small end face and a second support surface on its large end face. In the semi-finishing stage, a fixture is used to support the second support surface while semi-finishing the small end face and inner circumferential end groove of the workpiece. This prioritizes ensuring the machining rigidity of difficult processes and increases the support surface to improve workpiece clamping reliability. In the semi-finishing stage, a fixture is used to support the first support surface while semi-finishing the large end face and inner circumferential hook groove of the workpiece. This improves the machining rigidity of the part and solves the problem of deformation caused by large cutting forces during rough machining of the outer ring hook groove in CNC turning. In the finishing stage, a fixture is used to support the small end face while finish milling the inner ring decorative edge, solving the problem of large cutting forces causing part deformation during CNC milling of the inner cavity decorative edge. Furthermore, the optimized process route based on this method solves the problems of long machining cycles and part deformation in gas turbine casing parts, and the use of more reasonable cutting parameters leads to a limited improvement in the machining quality and cutting efficiency of the parts.

[0057] In this embodiment, in step S1, the rough-machined workpiece includes the outer ring hook groove, the outer circumferential surface, the inner circumferential surface, the small end face, and the large end face. A CNC program for machining the outer ring hook groove is compiled using Mastercam. When rough-machined, a tool holder with a square tool holder is used for tool mounting, and a finishing command is selected to machine in one pass to ensure chip continuity and facilitate chip removal. Specifically, the machining parameters are: feed F 0.1 mm / r, constant linear speed S 30~35 m / min. After rough-machined outer ring hook groove, the side margin of outer ring hook groove is 0.15 mm, and the bottom margin of outer ring hook groove is 0.05 mm, effectively avoiding vibration at the bottom of the groove during finishing.

[0058] In addition, during the rough machining of the workpiece, a machining allowance of 1.5mm is left on each side of the workpiece;

[0059] It should be noted that after the rough machining in step S1 is completed, the workpiece is stabilized to eliminate stress.

[0060] In this embodiment, the outer cover of the workpiece is welded before step S6;

[0061] In this embodiment, step S6 includes:

[0062] S61. Support the first support surface, and finish the position of the spray painting groove;

[0063] S62. Spraying;

[0064] In this embodiment, step S7 includes:

[0065] S71. Support the second support surface, and precision machine the small end face of the workpiece. That is, complete the small end machining of the workpiece before machining the precision dimensions of the mounting edge of the workpiece, and improve the flatness of the first support surface of the workpiece, thereby reducing the problem of deformation during subsequent pressing processes.

[0066] S72. Support the first support surface, and finish machine the outer ring hook groove of the workpiece's large end face and inner circumference surface; specifically, when finishing machine the outer ring hook groove of the workpiece's inner circumference surface, select the finish machine command, and after machining the radial dimension of the outer ring hook groove to the required position, machine the width dimension; specifically, when finishing machine the outer ring hook groove of the workpiece's inner circumference surface, do not select the groove command, select the finish machine command, and set the machining parameters as follows: feed F 0.1mm / r, constant linear speed S 30~35m / min; the toolpath first machines the radial dimensions of the two grooves to the required position, and then machines the groove width dimension to avoid repeated adjustments of tool compensation during machining.

[0067] S73. Support the first support surface and precision mill the workpiece's slot;

[0068] During finishing, a machining allowance of 0.5mm is left on each side of the workpiece. If the allowance is greater than 0.5mm, the cutting force is large, the tool wear is severe, and tool deflection and vibration are likely to occur. If the allowance is less than 0.5mm, tool drift is likely to occur, resulting in vibration.

[0069] It should be noted that before finishing, the cutting tool should be replaced with a new one to avoid the worn-out tool becoming too sharp, which would result in poor surface quality and unacceptable appearance. This would also prevent the dimensional accuracy requirements from being met, and would require repeated tool compensation, which could lead to the part's dimensions being out of tolerance.

[0070] In this embodiment, step S8 includes: supporting the second support surface and the positioning groove of the inner mounting edge of the workpiece for electrical discharge machining.

[0071] In step S8, the positioning groove of the workpiece is finished by electrical discharge machining using an electrical discharge fixture and machining components. The electrical discharge fixture includes:

[0072] The first base plate 11 is used for positioning and mounting on the electrical discharge machining tool, and the bottom surface of the first base plate 11 is the reference surface;

[0073] The first positioning plate 12 is used for positioning and mounting on the first base plate 11. The first base plate 11 has a mounting groove for embedding the first positioning plate 12. The first base plate 11 is provided with a first fastening screw 19 that is threadedly connected to the first positioning plate 12 to fix it. The first positioning plate 12 has a first positioning groove 121 for cooperating with the mounting edge of the workpiece.

[0074] The first pressure plate 13 is connected to the first base plate 11 and is used to press against the end face of the mounting edge of the workpiece to press and fix the workpiece onto the first positioning plate 12.

[0075] Specifically, it also includes a first double-ended stud 14, one end of which is threaded to the first base plate 11, and the other end passes through the middle of the first pressure plate 13 and is connected to the first nut 15; the first base plate 11 is also threaded with a first adjusting support 16, which is located between the end of the first pressure plate 13 away from the center of the EDM fixture and the first pressure plate 13. The first adjusting support 16 is threaded with a first limiting nut 17. By rotating the first adjusting support 16, its height extending out of the pressure plate surface can be adjusted, and it can be locked and fixed by the first nut 15 and the first limiting nut 17, so as to realize the support adjustment of the end of the first pressure plate 13 away from the workpiece, and to realize the adjustment of the clamping force applied by the first pressure plate 13 to the workpiece. Then tighten the first nut 15 to ensure the processing rigidity of the workpiece and the fixed stability; in addition, a diamond-shaped pin 18 is also installed on the first positioning plate 12 at a preset position so as to align the positioning angle with the hole according to the process requirements when clamping and positioning the workpiece.

[0076] The processing components include a zero-point positioning device, an electrode disk 21, and electrode heads 22 evenly distributed circumferentially on the electrode disk 21. The electrode heads 22 are detachably connected to the electrode disk 21. The position and number of the electrode heads 22 correspond to the position and number of the positioning slots on the workpiece. The zero-point positioning device enables high-precision installation and rapid positioning of the electrode disk 21, avoiding repeated clamping and alignment, and improving processing accuracy. The electrode heads 22 are made of copper and are detachably connected to the electrode disk 21, allowing the electrode disk 21 to be reused. The electrode heads 22 can be replaced individually according to wear, thereby improving processing efficiency and reducing processing costs.

[0077] When performing CNC machining on a workpiece, a CNC machining fixture is used to clamp and position the workpiece. The CNC machining fixture includes a second base plate 31, a second pressure plate 33, and a second positioning plate 32. The second base plate 31 is matched with the clamping structure of the CNC lathe, and the bottom surface of the second base plate 31 is the reference surface. The second positioning plate 32 is embedded in a mounting groove opened on the second base plate 31. The second positioning plate 32 has a second positioning groove 321 for cooperating with the mounting edge of the workpiece. Multiple second pressure plates 33 are evenly distributed along the circumference of the second base plate 31. A second fastening screw 34 is provided on the second base plate 31 to fasten the workpiece. The two positioning discs 32 are threaded together to fix the workpiece. The connection structure between the second pressure plate 33 and the second base plate 31, as well as the clamping and fixing method for the workpiece, are implemented with reference to the connection structure between the first pressure plate 13 and the first base plate 11. In addition, a lifting ring 35 is provided on the second base plate 31 to mount the fixture onto the CNC lathe. A positioning bushing 36 is also provided at the center of the second positioning disc 32 to center the fixture and the machine tool flange. After adjusting the screws to loosen the second pressure plate 33, the workpiece is placed in the positioning groove of the second positioning disc 32 and aligned according to the process requirements. The nuts / screws are then tightened to complete the workpiece clamping and positioning.

[0078] When performing CNC milling on a workpiece, a CNC milling fixture is used to clamp and position the workpiece. The CNC milling fixture includes a third base plate 41, a third pressure plate 43, and a third positioning plate 42. The third positioning plate 42 is embedded in a mounting groove on the third base plate 41. The third positioning plate 42 has a positioning structure 421 for matching with the workpiece. Multiple third pressure plates 43 are evenly distributed around the circumference of the third base plate 41. A third fastening screw 44 is provided on the third base plate 41 and threadedly connected to the third positioning plate 42 to fix it. The connection structure between the third pressure plate 43 and the third base plate 41, as well as the clamping and fixing method of the workpiece, are implemented with reference to the connection structure of the first pressure plate 13 and the first base plate 11. In addition, one side of the third base plate 41 is a reference surface. After the third base plate 41 is installed on the CNC milling machine, the reference surface is leveled. The workpiece is clamped and the nuts / screws are tightened to complete the workpiece clamping and alignment, referring to the clamping method of the CNC milling fixture.

[0079] This machining method aims to quickly remove excess material and prioritize the rigidity of difficult machining processes. It improves clamping reliability by increasing the support surface and develops a more efficient machining route, maximizing the machining rigidity of the gas turbine casing workpiece. It also allows for rapid removal of excess material from the blank workpiece, employs more reasonable cutting parameters, and utilizes a dedicated fixture and replaceable dedicated electrodes to enhance workpiece machining rigidity. This effectively improves workpiece machining quality and significantly increases cutting efficiency. Based on this method, roughing takes approximately 2 hours and 10 minutes, finishing takes approximately 2 hours and 30 minutes, and the total machining time is approximately 4 hours and 40 minutes. Its machining efficiency is more than 50% higher than existing methods.

[0080] On the other hand, this embodiment also provides an aero engine that uses the above-mentioned processing method.

[0081] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for machining a gas turbine casing, characterized in that, Includes the following steps: S1. Obtain the workpiece blank, rough machine the shape of the workpiece, the small end face of the rough machined workpiece forms the first support surface, the large end face of the rough machined workpiece forms the second support surface, leaving machining allowance. S2. The large end face of the semi-finished workpiece forms the machining reference surface; S3. Supported by the second support surface, the small end face and inner circumferential end groove of the semi-finished workpiece; supported by the first support surface, the large end face and inner circumferential hook groove of the semi-finished workpiece. S4. Support the first support surface and precision mill the inner ring lace edge; S5. Support the second support surface and finish the outer circular air film hole; S6. Spraying; S71. Support the second support surface and precision machine the small end face of the workpiece; S72. Support the first support surface, finish machine the large end face of the workpiece and the outer ring hook groove of the inner circumference of the workpiece; when finish machining the outer ring hook groove of the inner circumference of the workpiece, select the finish machining command, and after machining the radial dimension of the outer ring hook groove to the required position, machine the width dimension. S73. Support the first support surface and precision mill the workpiece's groove; S8. Electrical Discharge Machining.

2. The processing method for a gas turbine casing according to claim 1, characterized in that, In step S1, the rough-machined workpiece includes the outer ring hook groove. When rough-machined the outer ring hook groove, the tool is mounted by using a transfer tool holder in conjunction with a square tool holder, and the finish turning command is selected to machine it in one pass.

3. The processing method for a gas turbine casing according to claim 2, characterized in that, In step S1, after rough machining the outer ring hook groove, the side margin of the outer ring hook groove is 0.15mm and the bottom margin of the outer ring hook groove is 0.05mm.

4. The processing method for a gas turbine casing according to claim 1, characterized in that, Step S8 includes: supporting the second support surface and the positioning groove of the inner mounting edge of the workpiece for electrical discharge machining.

5. The processing method for a gas turbine casing according to claim 4, characterized in that, In step S8, the positioning groove of the workpiece is finished by electrical discharge machining using an electrical discharge fixture and machining components. The electrical discharge fixture includes: The first base plate (11) is used for positioning and installation on the electrical discharge machining tool; The first positioning plate (12) is used for positioning and mounting on the first base plate (11). The first positioning plate (12) has a first positioning groove (121) for cooperating with the mounting edge of the workpiece. The first pressure plate (13) is connected to the first base plate (11) and is used to press against the end face of the mounting edge of the workpiece to press and fix the workpiece onto the first positioning plate (12).

6. The method for machining a gas turbine casing according to claim 5, characterized in that, The processing components include a zero-point positioning device, an electrode disk (21), and electrode heads (22) uniformly arranged circumferentially and mounted on the electrode disk (21).

7. The method for machining a gas turbine casing according to any one of claims 1-6, characterized in that, The processing method further includes: during rough machining, a machining allowance of 1.5mm is left on one side of the workpiece; during finish machining, a machining allowance of 0.5mm is left on one side of the workpiece.

8. An aircraft engine, characterized in that, The application has the processing method for a gas turbine casing as described in any one of claims 1-7.

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