Machining method for sectional type turbine outer ring of aero-engine

Abstract

The invention discloses a method for machining a segmented turbine outer ring of an aero-engine, which comprises the following steps of: firstly, integrally machining an annular groove, a weight reducing groove and a precise narrow groove on the turbine outer ring, optimizing a cutting process and parameters, controlling deformation, then carrying out linear cutting on the turbine outer ring, machining a sealing groove on segmented parts, and brazing a honeycomb. And finally, the segmented parts are integrally combined to remove the honeycomb allowance, and the product percent of pass is increased. In the machining process, multiple clamps are combined to restrain the part, control over deformation and machining deviation of the part is guaranteed, and the problems that an existing turbine outer ring is prone to deformation, large in machining deviation, large in machining difficulty and the like in the machining process are solved.

Description

Technical Field

[0001] This invention relates to the field of segmented turbine outer ring machining technology, and more specifically, to a machining method for segmented turbine outer rings of aero-engines. Background Technology

[0002] The low-pressure turbine outer ring is a key stator component of the low-pressure turbine in an aero-engine. Its main function is to form a sealed airflow channel with the blades and to provide positioning, heat insulation and support. A certain low-pressure turbine outer ring has an overall inclined structure with two honeycomb sections brazed on the inclined surface. It has the characteristics of large diameter, thin wall thickness and small dimensional tolerance. The low-pressure turbine outer ring is composed of multiple parts. During the processing, due to the complex groove structure of the low-pressure turbine outer ring parts and the high dimensional precision requirements, the following difficulties exist in the processing: (1) The parts have poor rigidity and are easy to deform during processing. For example, they are easy to deform during groove processing, and the wall thickness is uneven. Or, during the segmented cutting process, the parts shrink and deform, and the angular dimensions exceed the tolerance. (2) The support surface of the parts is greatly deformed, which will lead to deformation of the reference surface and length exceeding the tolerance during the machining process. (3) The end face sealing groove is narrow and deep, and the electrodes are prone to abnormal discharge and processing deformation, resulting in the sealing groove dimensions being unqualified. (4) The turbine outer ring has honeycomb brazing, which increases the difficulty of part processing and makes it difficult to ensure the processing quality of the parts.

[0003] CN114850799B discloses a machining fixture and method for a ceramic matrix composite turbine outer ring. The turbine outer ring machining fixture includes a base, a support ring located on the upper end face of the base, and a pressure plate. The base has a second slot boss along its circumferential direction at its center, which is adapted to a second slot of the turbine outer ring to be machined. The second slot boss is used to engage with the second slot. The axial height of the support ring is consistent with the axial height of the base plate of the turbine outer ring to be machined, and the outer side of the support ring is adapted to the inner side of the base plate of the turbine outer ring to be machined, with the outer side of the support ring used to contact the inner side of the base plate of the turbine outer ring to be machined. The pressure plate includes an annular outer wall and an annular top plate fixed to the upper part of the annular outer wall and extending inward. The lower side of the annular top plate is provided with pressure plate steps in a radial direction from the inside to the outside. The step surface of the pressure plate step is used to contact the upper end surface of the bottom plate of the turbine outer ring to be processed and the upper end surface of the support ring, and the step surface of the pressure plate step is connected to the upper end surface of the support ring. The pressure plate also includes a first slot boss that is adapted to the first slot of the turbine outer ring to be processed. The first slot boss is used to be engaged in the first slot. The inner wall surface of the pressure plate is adapted to the outer surface of the first slot outer wall and the outer surface of the second slot outer wall of the turbine outer ring to be processed. The inner wall surface of the pressure plate is used to contact the outer surface of the first slot outer wall and the outer surface of the second slot outer wall. This patent describes how the tooling, which is perfectly matched to the turbine outer ring structure, "fills" the grooves and surfaces to reduce workpiece deformation and effectively improves the dimensional accuracy of the turbine outer ring. However, it is difficult to adapt to the complex turbine outer ring structure with its surface and groove. At the same time, the tooling's covering of the blank makes it difficult to process the part.

[0004] CN121424011A discloses a method for machining a ceramic matrix composite turbine outer ring, which includes the following steps: first, grinding, inspecting, and cutting the blank to obtain a part with a 1mm margin; then, clamping the part using high-viscosity paraffin wax; and finally, mounting it on a five-axis machining center for one-time machining; after the machine tool aligns the part, the outer ring is machined as a whole, and the five-axis machining center uses a grinding head for grinding. This patent eliminates the traditional clamping structure of pressure plates and bolts by using an adhesive clamping method, reducing machining errors caused by clamping and datum conversion, ensuring dimensional accuracy and stability, and improving production efficiency. However, this patent directly uses segmented blanks to machine the outer ring's bottom arc surface, ribs, rib edges, side end faces, sealing grooves, and holes. However, in machining thin-walled turbine outer rings, adhesive fixing can easily lead to clamping instability, causing deformation during milling or groove machining. Furthermore, segmented machining further increases the difficulty of clamping. Therefore, the existing turbine outer ring machining fixtures or machining methods have significant limitations and make it difficult to control the deformation and machining deviations of complex turbine outer ring parts. Summary of the Invention

[0005] The main technical problem to be solved by this invention is to address the shortcomings of existing segmented turbine outer ring machining processes, such as part deformation, large machining deviations, and low pass rates, and to provide a machining method for segmented turbine outer rings for aero-engines.

[0006] The objective of this invention is achieved through the following technical solution: A method for processing a segmented turbine outer ring for an aero-engine, characterized in that the outer wall of the turbine outer ring is provided with a weight reduction groove, a first annular groove, and a second annular groove, the first annular groove and the second annular groove are provided with air film holes, the groove opening wall of the second annular groove is provided with a precision narrow groove, and the inner wall of the annular ring is provided with a honeycomb structure. The processing steps include: S1. Roughly machine the turbine outer ring blank, and then machine the two end faces of the turbine outer ring blank to obtain the first support surface and the second support surface respectively, and determine the axial reference. S2. Use a support fixture to fix the second support surface, machine the basic profile of the blank wall surface, groove wall thickness and annular groove, and then cut the weight reduction groove and precision narrow groove. S3. Set angular pins in the precision narrow groove, align the outer circle of the mounting edge, and use high-speed electrical discharge to machine air film holes in the first and second annular grooves. S4. Use a wire EDM fixture to clamp the ring part, then use precision wire EDM to cut it into segments, then braze honeycomb on the inner wall of the segmented part, and then remove the honeycomb excess. S5. A multi-dimensional support and clamping fixture is adopted. The large end face and the outer circle of the large end face of the part support the fixture surface. The upper end face of the part to be processed is close to the fixture alignment block. The lower end face of the part is adjusted by adjusting the bottom screw to make the end face close to the stop block. The part is clamped in the axial direction by the arc imitation pressure plate and in the radial direction by the cylindrical head set screw to clamp the middle part and fix it. The end face sealing groove is machined by electrical discharge machining. S6. Support the bottom of the annular groove of the part, set the angular pin for the precision narrow groove, connect the segmented turbine outer ring to the fixture through the sealing plate, adjust so that the runout of the part's datum surface is ≤0.05 and the runout of the inner hole's four symmetrical points is ≤0.05, press the large end face to fix the part, use a circular electrode to process the honeycomb, and then remove the honeycomb allowance through roughing, semi-finishing, and finishing. S7. Once the inspection is passed, the segmented turbine outer ring can be divided.

[0007] Furthermore, after rough machining in S1, the ring-shaped part is pre-brazed at a temperature of 1035°C to remove the internal stress generated after rough machining and effectively reduce thermal damage during subsequent assembly.

[0008] Furthermore, step S1 also includes grinding and shaping the end faces of the first and / or second support surfaces to eliminate the deformation of the parts and avoid the accumulation of deformation in subsequent processing. The flatness of the ground first and / or second support surfaces shall not be less than 0.03 mm.

[0009] Furthermore, the cutting of the weight reduction groove is carried out by processing each segment separately. After the four points of the part are aligned, the initial angular direction is set, and the machine tool probe is used to collect points. The angle is converted according to the number of segments of the outer ring of the turbine. Five points are collected for each segment. After collecting the points, the deformation state of each segment of the part is judged according to the output data, and the zero-point offset is performed for each segment separately.

[0010] Furthermore, the weight-reducing groove is machined using a wide-line contact milling method with the bottom tooth edge of a milling cutter. First, a 10mm diameter alloy milling cutter with a radius of R0.5mm is used for roughing, leaving a 0.2mm allowance. Then, a 3mm diameter alloy milling cutter with a radius of R0.5mm is used for finishing the outer circle using a two-axis machining method with XY linkage. For finishing the conical surface, a 3mm diameter alloy flat-bottom milling cutter is used perpendicular to the generatrix of the conical surface, using a line contact machining method. Two cuts in the radial direction are sufficient to complete the conical surface milling. The roughing and finishing allowances of the weight-reducing groove are allocated, and the deformation of the part during machining is strictly controlled to avoid uneven wall thickness after machining of the weight-reducing groove, which would lead to unqualified precision narrow groove machining.

[0011] Furthermore, the support clamp includes a disc base, on which a positioning block and a pressure plate are provided. The pressure plate is connected to the disc base by a movable bolt, and the positioning block and the pressure plate are used to position, support and press the support surface.

[0012] Furthermore, the precision narrow groove is machined by contacting the bottom edge of a milling cutter. First, the narrow groove is rough machined in layers using the bottom edge of an alloy milling cutter, leaving a 0.1mm allowance. Then, the side and bottom edges of the narrow groove are finished using the side and bottom edges of an alloy iron cutter.

[0013] Furthermore, the wire cutting fixture includes a base plate, on which an angular pin and a pressure plate are provided. Both the angular pin and the pressure plate are connected to the base plate by bolts. The angular pin extends into the precision narrow groove to fix the second annular groove, thereby limiting the displacement of the turbine outer ring. At the same time, the pressure plate presses and fixes the groove wall, which can reduce the deformation caused by the springback of the part after the annular thin-walled part is cut.

[0014] Furthermore, S3 also includes burr and flash removal, and fluorescence detection of defects.

[0015] Furthermore, the electrode used in the electrical discharge machining (EDM) employs a clampable electrode chuck, and the thickness of the EDM electrode is 0.1 mm smaller than the width of the sealing groove.

[0016] Furthermore, during the processing of the sealing groove, a shallow mark 0.2 mm deep is first processed using an electrode. After determining the processing dimensions, the groove is then processed to half its depth. The electrode is then lifted to flush out the carbon deposits in the groove before proceeding with subsequent processing.

[0017] Compared with existing technologies, the beneficial effects are: This invention optimizes the processing technology by first machining the annular groove and basic profile, and controlling the axial reference surface to eliminate deformation during the machining of the profile and groove, thus reducing the accumulation of machining deformation. Then, the weight-reducing groove is machined segment by segment, allocating rough and finish machining allowances to reduce tool wear and control part deformation. Simultaneously, the tool path and parameters are optimized in the precision narrow groove to control tool vibration during machining, ultimately ensuring the required wall thickness and precise narrow groove dimensions of the composite weight-reducing groove. This invention performs segmented brazing after machining the groove structure of the turbine outer ring. Segmented brazing is simpler than full-ring brazing. On the one hand, it avoids the instability and deformation problems associated with complex grooves after segmentation; on the other hand, segmentation eliminates the need to consider honeycomb interference, and the strip honeycomb is easier to fit with the outer ring, reducing the difficulty of the brazing process and improving the brazing pass rate.

[0018] This invention fully utilizes fixtures during processing. Angle pins are used in precision narrow slots to position the outer diameter of the part. During segmented cutting, the angle pins and pressure plates clamp the upper and lower parts to fix the part, reducing deformation caused by springback after the annular thin-walled part is cut. This invention designs multi-dimensional fixing fixtures to fix the part in multiple directions, preventing movement. Simultaneously, a clampable electrode chuck is used to process the sealing groove, avoiding unstable EDM and electrode deformation during sealing groove processing. This invention designs a segmented turbine outer ring fixture, connecting and supporting the segmented turbine outer ring on the fixture via sealing plates. By adjusting the bottom adjustable support, the runout of the part's reference surface and the symmetrical runout of the inner hole meet the requirements. Roughing, semi-finishing, and finishing processes using overall EDM remove honeycomb excess material, ensuring both efficiency and honeycomb quality. Attached Figure Description

[0019] Figure 1 This is a diagram of the segmented turbine outer ring structure; Figure 2 This is a schematic diagram of the clamping fixture, where a is the support surface and b is the clamping surface. Figure 3 This is a schematic diagram of the support clamp; Figure 4 This is a schematic diagram of a wire EDM fixture; Figure 5 Schematic diagram of a multi-dimensional support and clamping fixture; Figure 6 This is a schematic diagram of the cross-section of a multi-dimensional support and clamping fixture; Figure 7 This is a schematic diagram of the cross-section of the multidimensional support and clamping fixture AA.

[0020] Among them, 1 is the weight reduction groove, 2 is the first annular groove, 3 is the honeycomb, 4 is the sealing groove, 5 is the second annular groove, 6 is the groove wall thickness, 7 is the air film hole, 8 is the precision narrow groove, 9 is the disc base, 10 is the positioning block, 11 is the first pressure plate, 12 is the first base plate, 13 is the angular pin, 14 is the second pressure plate, 15 is the second base plate, 16 is the positioning body, 17 is the pressure block, 18 is the alignment block, 19 is the tightening screw, 20 is the support, 21 is the stop block, and 22 is the adjusting screw. Detailed Implementation

[0021] The following examples further explain and clarify the invention, but the specific examples do not limit the invention in any way.

[0022] Example 1 This embodiment provides a segmented turbine outer ring for an aero-engine. The turbine outer ring has an overall inclined structure, with two honeycomb sections 3 brazed on the inclined surface. The inner diameter tolerance of the honeycomb sections 3 is 0.05mm. The two ends of the turbine outer ring are a large end face and a small end face, respectively. The segmented turbine outer ring is formed by dividing a ring-shaped component, with a minimum wall thickness of 1.8mm. Its cross-sectional structure is as follows. Figure 1 As shown, a weight reduction groove 1, a first annular groove 2, and a second annular groove 5 are sequentially provided on the wall surface from the small end face to the large end face. The wall thickness 6 of the groove opening of the first annular groove 2 and the second annular groove 5 has a tolerance of 0.04 mm. An air film hole 7 is provided in the second annular groove 5. The size tolerance of the air film hole 7 is 0.07 mm. A precision narrow groove 8 is provided on the wall thickness 6 of the groove opening of the second annular groove 5. The width and depth tolerance of the precision narrow groove 8 are 0.1 mm.

[0023] The above-mentioned method for machining the segmented turbine outer ring of an aero-engine includes the following steps: S1. Rough machining of the overall part profile: Remove most of the blank material according to the approximate profile of the part, leaving about 1mm of allowance on each side to reduce deformation caused by excessive material removal during finishing.

[0024] S2. Determine the axial reference of the part: First, color the large end face and use a fixture to clamp the large end face. Machin the first support surface on the small end face. Then, color the small end face, clamp the colored points, and turn the large end face and the mounting edge to machine the second support surface, thus realizing the conversion of the axial reference from the small end face to the axial reference of the large end face.

[0025] S3. Turning the part profile and annular groove: Clamp the second support surface, align the outer circle of the mounting edge, and machine the profile, groove wall thickness 6 and annular groove to machine the basic profile of the part.

[0026] S4. Cut the weight reduction groove 1 and the precision narrow groove 8: clamp the second support surface, align the outer circle of the part mounting edge, and use a five-axis horizontal machining center to process the weight reduction groove 1 and the precision narrow groove 8. S41. Weight Reduction Groove 1 Machining: A separate machining method is adopted for each segment. After aligning the part at four points using a dial indicator, an initial angular direction is set. Points are collected using a machine tool probe, and the angle is calculated based on the number of segments in the low-pressure turbine outer ring, resulting in five points for each segment. After point collection, the deformation state of each segment is determined based on the output data, and a zero-point offset is applied to each segment individually. Specifically, a wide-line machining method using the bottom tooth edge contact of a milling cutter is adopted. Roughing is performed using a φ10R0.5 alloy milling cutter, with a 0.2mm allowance for finishing. Finishing of the outer diameter uses a φ3R0.5 alloy milling cutter employing a two-axis machining method with XY linkage. For conical surface finishing, a φ3 alloy flat-bottom milling cutter is used perpendicular to the generatrix of the conical surface, employing a line contact machining method. Two back-and-forth cuts along the radial direction are sufficient to complete the conical surface milling.

[0027] S42. Precision Narrow Slot Machining: First, use the bottom edge of a φ3 alloy milling cutter to rough machine the narrow slot in layers, leaving a 0.1mm allowance. Then, use the side edge / bottom edge of a φ3R0.5 alloy iron cutter to finish the side and bottom surfaces of the narrow slot. Control the vibration of the cutter during the machining process to ensure the dimensional and surface roughness requirements.

[0028] S5. Machining of the film ventilation hole 7: An angular pin 13 is set in the precision narrow groove 8, and the film ventilation hole 7 on the annular groove is machined using high-speed electrical discharge machining to ensure the ventilation and heat dissipation function of the annular groove. Then, the surface of the annular groove is supported, and the small end face is also supported to align the inner hole boss circle. A groove is machined in the middle part of the inner hole boss to reduce the weight of the part.

[0029] S6. Wire EDM Segmentation: The parts are clamped, and the angular pins 13 are set in the precision narrow groove 8 to position the outer circle of the parts and align the outer circle of the mounting edge. The turbine outer ring is segmented into 28 pieces by precision wire EDM.

[0030] S7. Segmented brazing: Braze the segmented parts with honeycomb 3 structure, remove excess honeycomb 3, and level the end face of the parts so that the runout is no more than 0.02.

[0031] S8. Groove machining: Support the small end face, press the large end face, align the left and right positions of the part and center it, ensure that the middle part of the part is consistent with the symmetry line, and use an electrode to machine the groove part of the surface.

[0032] S9. Sealing Groove 4 Machining: Clamp the segmented parts, first use the electrode to machine a shallow mark about 0.2mm deep, measure the size, and after the size is correct, proceed with subsequent machining. After machining to half the depth, the electrode needs to be lifted to flush out the carbon deposits in the groove before proceeding with subsequent machining to ensure the size of sealing groove 4.

[0033] S10. Honeycomb 3 Machining: Supporting the bottom of the annular groove of the part, angular pins 13 are set in the precision narrow groove 8. 28 segmented turbine outer rings are connected and supported on the fixture via sealing plates, ensuring the runout of the part's datum surface is ≤0.05 and the runout of the inner hole's four symmetrical points is ≤0.05. The part is then clamped to secure the large end face. Honeycomb 3 is machined using a circular electrode, and the excess material in honeycomb 3 is removed through roughing, semi-finishing, and finishing.

[0034] S11. Remove all burrs from the parts, check that the parts are free from bumps, scratches, and excess material, check that the appearance of the honeycomb 3 and the damage to the core grid meet the standards, clean the parts and send them for fluorescent testing, and obtain the segmented turbine outer ring after passing the inspection.

[0035] Example 2 This embodiment provides a method for machining a segmented turbine outer ring for an aero-engine, the steps of which include: S1. Rough machining of the overall part profile: Remove most of the blank material according to the approximate profile of the part, leaving about 1mm of allowance on each side to reduce deformation caused by excessive material removal during finishing.

[0036] S2. Pre-brazing: The rough-machined parts are placed in a vacuum furnace and heated to 1035℃ for thermal cycling to perform pre-brazing, which removes the internal stress generated after rough machining and effectively reduces thermal damage during subsequent assembly.

[0037] S3. Determine the axial reference of the part: First, color the large end face and use a fixture to clamp the large end face. Machin the small end face to form the first support surface. Then, color the small end face, clamp the colored points, and turn the large end face and the mounting edge to form the second support surface, thus realizing the conversion from the axial reference of the small end face to the axial reference of the large end face.

[0038] S4. Turning the part profile and annular groove: Clamp the second support surface, align the outer circle of the mounting edge, and machine the profile, groove wall thickness 6 and annular groove to machine the basic profile of the part.

[0039] S5. Grinding the large end face of the axial direction: Use a fixture to support the annular groove surface and auxiliary support the small end face, align the outer circle of the mounting edge, and grind the large end face to eliminate the deformation of the part caused during the machining of the turning part surface and the annular groove. Grind the flatness of the large end face of the part to 0.03 to form a third support surface to avoid the accumulation of deformation in subsequent machining of the part.

[0040] S6. Cut the weight reduction groove 1 and the precision narrow groove 8: clamp the third support surface, align the outer circle of the part mounting edge, and use a five-axis horizontal machining center to process the weight reduction groove 1 and the precision narrow groove 8. S61. Weight Reduction Groove 1 Machining: A separate machining method is adopted for each segment. After aligning the part at four points using a dial indicator, an initial angular direction is set. Points are collected using a machine tool probe, and the angle is calculated based on the number of segments in the low-pressure turbine outer ring, resulting in five points for each segment. After point collection, the deformation state of each segment is determined based on the output data, and a zero-point offset is applied to each segment individually. Specifically, a wide-line machining method using the bottom tooth edge contact of a milling cutter is adopted. Roughing is performed using a φ10R0.5 alloy milling cutter, with a 0.2mm allowance for finishing. Finishing of the outer diameter uses a φ3R0.5 alloy milling cutter employing a two-axis machining method with XY linkage. For conical surface finishing, a φ3 alloy flat-bottom milling cutter is used perpendicular to the generatrix of the conical surface, employing a line contact machining method. Two back-and-forth cuts along the radial direction are sufficient to complete the conical surface milling.

[0041] S62. Precision Narrow Slot Machining: First, use the bottom edge of a φ3 alloy milling cutter to rough machine the narrow slot in layers, leaving a 0.1mm allowance. Then, use the side edge / bottom edge of a 3R0.5 alloy iron cutter to finish the side and bottom surfaces of the narrow slot. Control the vibration of the cutter during the machining process to ensure the dimensional and surface roughness requirements.

[0042] S7. Machining of the film air hole 7: An angular pin 13 is set in the precision narrow groove 8, and the film air hole 7 on the annular groove is machined using high-speed EDM to ensure the ventilation and heat dissipation function of the annular groove. Then, the surface of the annular groove is supported, and the small end face is also supported to align the inner hole boss circle. A groove is machined in the middle part of the inner hole boss to reduce the weight of the part.

[0043] S8. Defect inspection: Remove burrs and flash generated during machining to avoid excess material in the air film holes 7 and annular grooves, and perform fluorescent inspection on the parts.

[0044] S9. Wire EDM Segmentation: The defect-free parts are clamped using a wire EDM fixture. Angle pins 13 are set in the precision narrow groove 8 to position the outer circle of the part and align the outer circle of the mounting edge. The turbine outer ring is segmented into 28 pieces using precision wire EDM.

[0045] S10. Segmented brazing: Braze the segmented parts with honeycomb 3 structure, remove excess honeycomb 3, and level the end face of the parts so that the runout is no more than 0.02.

[0046] S11. Groove machining: Support the small end face, press the large end face, align the left and right positions of the part and center it, ensure that the middle part of the part is consistent with the symmetry line, and use an electrode to machine the groove part of the surface.

[0047] S12. Sealing Groove 4 Machining: Clamp the segmented parts, first use the electrode to machine a shallow mark about 0.2mm deep, measure the size, and after the size is correct, proceed with subsequent machining. After machining to half the depth, the electrode needs to be lifted to flush out the carbon deposits in the groove before proceeding with subsequent machining to ensure the size of sealing groove 4.

[0048] S13. Honeycomb 3 Machining: Supporting the bottom of the annular groove of the part, angular pins 13 are set in the precision narrow groove 8. 28 segmented turbine outer rings are connected and supported on the fixture via sealing plates, ensuring the runout of the part's datum surface is ≤0.05 and the runout of the inner hole's four symmetrical points is ≤0.05. The part is then clamped to secure the large end face. Honeycomb 3 is machined using a circular electrode, and the excess material in honeycomb 3 is removed through roughing, semi-finishing, and finishing.

[0049] S14. Remove all burrs from the parts, check that the parts are free from bumps, scratches, and excess material, check that the appearance of the honeycomb 3 and the damage to the core grid meet the standards, clean the parts and send them for fluorescent testing, and obtain the segmented turbine outer ring after passing the inspection.

[0050] Example 3 This embodiment provides a method for machining a segmented turbine outer ring for an aero-engine, the steps of which include: S1. Rough machining of the overall part profile: Remove most of the blank material according to the approximate profile of the part, leaving about 1mm of allowance on each side to reduce deformation caused by excessive material removal during finishing.

[0051] S2. Pre-brazing: The rough-machined parts are placed in a vacuum furnace and heated to 1035℃ for thermal cycling to perform pre-brazing, which removes the internal stress generated after rough machining and effectively reduces thermal damage during subsequent assembly.

[0052] S3. Determine the axial reference of the part: First, color the large end face and use a fixture to clamp the large end face. Machin the small end face to form the first support surface. Then, color the small end face, clamp the colored points, and turn the large end face and the mounting edge to form the second support surface, thus realizing the conversion from the axial reference of the small end face to the axial reference of the large end face.

[0053] S4. Turning part profiles and annular grooves: Use a support fixture to clamp the second support surface, such as... Figure 3 As shown, the support fixture includes a disc base 9, on which a positioning block 10 and a pressure plate 11 are provided. The positioning block 10 and the pressure plate 11 support and press the support surface of the part, align the outer circle of the mounting edge, and process the profile, groove wall thickness 6 and annular groove to process the basic profile of the part.

[0054] S5. Grinding the large end face of the axial direction: Use a fixture to support the annular groove surface and auxiliary support the small end face, align the outer circle of the mounting edge, and grind the large end face to eliminate the deformation of the part caused during the machining of the turning part surface and the annular groove. Grind the flatness of the large end face of the part to 0.03 to form a third support surface to avoid the accumulation of deformation in subsequent machining of the part.

[0055] S6. Cut the weight reduction groove 1 and the precision narrow groove 8: Use a support fixture to clamp the third support surface, align the outer circle of the mounting edge of the part, and use a five-axis horizontal machining center to process the weight reduction groove 1 and the precision narrow groove 8. S61. Weight Reduction Groove 1 Machining: A separate machining method is adopted for each segment. After aligning the part at four points using a dial indicator, an initial angular direction is set. Points are collected using a machine tool probe, and the angle is calculated based on the number of segments in the low-pressure turbine outer ring, resulting in five points for each segment. After point collection, the deformation state of each segment is determined based on the output data, and a zero-point offset is applied to each segment individually. Specifically, a wide-line machining method using the bottom tooth edge contact of a milling cutter is adopted. Roughing is performed using a φ10R0.5 alloy milling cutter, with a 0.2mm allowance for finishing. Finishing of the outer diameter uses a φ3R0.5 alloy milling cutter employing a two-axis machining method with XY linkage. For conical surface finishing, a φ3 alloy flat-bottom milling cutter is used perpendicular to the generatrix of the conical surface, employing a line contact machining method. Two back-and-forth cuts along the radial direction are sufficient to complete the conical surface milling.

[0056] S62. Precision Narrow Slot Machining: First, use the bottom edge of a φ3 alloy milling cutter to rough machine the narrow slot in layers, leaving a 0.1mm allowance. Then, use the side edge / bottom edge of a 3R0.5 alloy iron cutter to finish the side and bottom surfaces of the narrow slot. Control the vibration of the cutter during the machining process to ensure the dimensional and surface roughness requirements.

[0057] S7. Machining of the film air hole 7: An angular pin 13 is set in the precision narrow groove 8, and the film air hole 7 on the annular groove is machined using high-speed EDM to ensure the ventilation and heat dissipation function of the annular groove. Then, the surface of the annular groove is supported, and the small end face is also supported to align the inner hole boss circle. A groove is machined in the middle part of the inner hole boss to reduce the weight of the part.

[0058] S8. Defect inspection: Remove burrs and flash generated during machining to avoid excess material in the air film holes 7 and annular grooves, and perform fluorescent inspection on the parts.

[0059] S9. Wire EDM Segmentation: The defect-free parts are clamped using a wire EDM fixture. Angle pins 13 are set in the precision narrow groove 8 to position the outer circle of the part and align the outer circle of the mounting edge. The turbine outer ring is segmented into 28 pieces using precision wire EDM.

[0060] like Figure 4 The wire cutting fixture includes a base plate 12, on which an angular pin 13 and a pressure plate 14 are provided. Both the angular pin 13 and the pressure plate 14 are connected to the base plate 12 by bolts. The angular pin 13 in the precision narrow groove 8 can press the upper and lower parts to fix the part. The remaining sections are fixed by pressing the middle part with the pressure plate 14. This fixing and pressing method can reduce the deformation caused by the springback of the part after the annular thin-walled part is cut.

[0061] S9. Segmented brazing: Braze the segmented parts with honeycomb 3 structure, remove excess honeycomb 3, and level the end face of the parts so that the runout is no more than 0.02.

[0062] S10. Groove machining: Support the small end face, press the large end face, align the left and right positions of the part and center it, ensure that the middle part of the part is consistent with the symmetry line, and use an electrode to machine the groove part of the surface.

[0063] S11. Sealing groove 4 machining: Multi-dimensional support and clamping fixtures are used to clamp segmented parts, such as... Figures 5-6 The multidimensional support and clamping fixture includes a base plate 2 15, a positioning body 16 on the base plate 2 15, a mounting position for segmented parts on the positioning body 16, a stop block 21 on the lower side of the mounting position, an adjusting screw 22 on the stop block 21, and an alignment block 18 on the upper side. The stop block 21 and the alignment block 18 fix the cut ends of the segmented parts. A pressure block 17 is provided on the left side of the mounting position. The pressure block 17 is provided with an arc-shaped pressure plate 3 that presses against the second annular groove 5. A support 20 is provided on the right side of the mounting position. The support 20 is provided with a tightening screw 19. The tightening screw 19 presses against the inner side of the segmented parts, and the pressing part corresponds to the position of the pressure plate 3.

[0064] The large end face and outer circle of the segmented part are supported against the fixture surface. The upper end face of the part to be machined is pressed against the fixture alignment block 18. The lower end face of the part is pressed against the stop block 21 by the bottom adjusting screw 22. The part is pressed axially by the pressure plate and radially by the tightening screw 19 to fix the middle part. The part is fixed in multiple directions to prevent movement and reduce clamping deformation. A clampable electrode chuck is used. The thickness of the electrode for the sealing groove 4 made by EDM is 0.1mm smaller than the width of the sealing groove 4. First, a shallow mark of about 0.2mm is machined with the electrode to measure the size. After the size is correct, the subsequent machining is carried out. After machining to half the depth, the electrode needs to be lifted to flush out the carbon deposits in the groove before the subsequent machining is carried out to ensure the size of the sealing groove 4.

[0065] S12. Honeycomb 3 Machining: Supporting the bottom of the annular groove of the part, angular pins 13 are installed in the precision narrow groove 8. 28 segmented turbine outer rings are connected and supported on the fixture via sealing plates, resting on the large end face. A pressure plate is used to tighten them, and the angular pins 13 are inserted into the precision narrow groove 8. Adjustment is made to ensure the runout of the part's datum surface is ≤0.05, and the runout of the four symmetrical points of the inner hole is ≤0.05. The large end face is then tightened to fix the part. Circular electrodes are used to machine the honeycomb 3, removing excess material through roughing, semi-finishing, and finishing.

[0066] S13. Remove all burrs from the parts, check that the parts are free from bumps, scratches, and excess material, check that the appearance of the honeycomb 3 and the damage to the core grid meet the standards, clean the parts and send them for fluorescent testing, and obtain the segmented turbine outer ring after passing the inspection.

[0067] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for machining a segmented turbine outer ring for an aero-engine, characterized in that, The outer wall of the turbine outer ring is provided with a weight reduction groove, a first annular groove, and a second annular groove. The first annular groove and the second annular groove are provided with air film holes. The groove opening wall of the second annular groove is provided with a precision narrow groove, and the inner wall of the annular groove is provided with a honeycomb structure. The processing steps include: S1. Roughly machine the turbine outer ring blank, and then machine the two end faces of the turbine outer ring blank to obtain the first support surface and the second support surface respectively, and determine the axial reference. S2. Use a support fixture to fix the second support surface, machine the basic profile of the blank wall surface, groove wall thickness and annular groove, and then cut the weight reduction groove and precision narrow groove. S3. Set angular pins in the precision narrow groove, align the outer circle of the mounting edge, and use high-speed electrical discharge to machine air film holes in the first and second annular grooves. S4. Use a wire EDM fixture to clamp the ring part, then use precision wire EDM to cut it into segments, then braze honeycomb on the inner wall of the segmented part, and then remove the honeycomb excess. S5. A multi-dimensional support and clamping fixture is adopted. The large end face and the outer circle of the large end face of the part support the fixture surface. The upper end face of the part to be processed is close to the fixture alignment block. The lower end face of the part is adjusted by adjusting the bottom screw to make the end face close to the stop block. The part is clamped in the axial direction by the arc imitation pressure plate and in the radial direction by the cylindrical head set screw to clamp the middle part and fix it. The end face sealing groove is machined by electrical discharge machining. S6. Support the bottom of the annular groove of the part, set the angular pin for the precision narrow groove, connect the segmented turbine outer ring to the fixture through the sealing plate, adjust so that the runout of the part's datum surface is ≤0.05 and the runout of the inner hole's four symmetrical points is ≤0.05, press the large end face to fix the part, use a circular electrode to process the honeycomb, and then remove the honeycomb allowance through roughing, semi-finishing, and finishing. S7. Once the inspection is passed, the segmented turbine outer ring can be divided.

2. The machining method for the segmented turbine outer ring of an aero-engine according to claim 1, characterized in that, After the S1 rough machining, the ring-shaped part is also pre-brazed.

3. The machining method for the segmented turbine outer ring of an aero-engine according to claim 1, characterized in that, Step S1 also includes grinding and shaping the end faces of the first and / or second support surfaces, with the flatness of the first and / or second support surfaces not less than 0.03 mm.

4. The machining method for the segmented turbine outer ring of an aero-engine according to claim 1, characterized in that, The cutting of the weight reduction groove is carried out by processing each segment separately. After the four points of the part are aligned, the initial angular direction is set, and the machine tool probe is used to collect points. The angle is converted according to the number of outer ring segments of the turbine. Five points are collected for each segment. After collecting the points, the deformation state of each segment of the part is judged according to the output data, and the zero-point offset is performed for each segment separately.

5. The machining method for the segmented turbine outer ring of an aero-engine according to claim 1, characterized in that, The support clamp includes a disc base, on which a positioning block and a pressure plate are provided. The pressure plate is connected to the disc base by a movable bolt.

6. The machining method for the segmented turbine outer ring of an aero-engine according to claim 1, characterized in that, The precision narrow groove is machined by contacting the bottom edge of the milling cutter. First, the bottom edge of the alloy milling cutter is used to rough machine the narrow groove in layers, leaving a 0.1mm allowance. Then, the side edge and bottom edge of the alloy iron cutter are used to finish the side and bottom surfaces of the narrow groove.

7. The machining method for the segmented turbine outer ring of an aero-engine according to claim 1, characterized in that, The wire cutting fixture includes a base plate, on which an angular pin and a pressure plate are provided. Both the angular pin and the pressure plate are connected to the base plate by bolts.

8. The machining method for the segmented turbine outer ring of an aero-engine according to claim 1, characterized in that, S3 also includes burr and flash removal, and fluorescence detection of defects.

9. The machining method for the segmented turbine outer ring of an aero-engine according to claim 1, characterized in that, The electrode thickness of the electrical discharge machining is 0.1 mm smaller than the width of the sealing groove.

10. The machining method for the segmented turbine outer ring of an aero-engine according to claim 1, characterized in that, During the machining of the sealing groove, a deep groove is first machined using an electrode. For a shallow mark of 0.2mm, after determining the processing dimensions, process it to half the depth, then lift the electrode, flush out the carbon deposits in the tank, and then proceed with subsequent processing.

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