Blisk machining method for narrow-channel ultra-large-length-width-ratio blade

Abstract

The invention discloses an efficient machining method for an aeroengine blisk. Outer end blades of the blisk are of a structure arranged in an outer closed ring. A processing mode of layered rough milling and finish milling is adopted, a customized straight shank milling cutter is adopted for rough milling, a lollipop-shaped milling cutter is adopted for finish milling, the processing precision of a milling blade profile is improved, and part deformation is reduced; when the blade profile is roughly milled, the allowance of 0.8 + / -0.3 mm is reserved between the blade profile and the runner surface; and then, a stress removing mode is added, internal stress generated by rough milling is eliminated, specifically, the workpiece is subjected to heat treatment at the temperature of 300-450 DEG C and then cooled to the room temperature so as to reduce part deformation, then a lollipop milling cutter is used for small-allowance multiple cutting for finish milling, the deformation of the part is controlled, and the size of the part is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of engines, and particularly to a method for machining an integrally bladed disk of a narrow-channel super-large aspect ratio blade for an aeroengine. Background Art

[0002] The working process of an aero turbofan engine is as follows: The air flowing into the engine is compressed by the blades of the first stage and above to form high-pressure air, which is then mixed with fuel to form high-temperature and high-pressure gas and ejected to generate thrust to propel the aircraft to fly. Since a higher compression ratio means higher economy of the turbofan engine. Therefore, in order to meet the higher supercharging requirements, it is required that the blades inside the turbofan engine can not only better pressurize the air pressure, but also block the high-pressure air from flowing back to the front end of the engine. Therefore, installing more blades per unit area can not only meet the greater supercharging requirements, but also well force the air with increasing pressure to flow to the rear end of the engine to be mixed with fuel and burned and ejected.

[0003] Therefore, the design and manufacture of an integrally bladed ring of a narrow-channel super-large aspect ratio blade are necessary choices. The structural characteristics of the integrally bladed ring of the super-large aspect ratio blade are that it consists of a rotating disk body, a circle of 70-100 evenly distributed blades (length 180 mm × channel i.e., flow path width 8.5 mm), and a 1.8-mm-thick blade crown (the blade crown is located at the top of the turbine blade and is a thin structure as a part of the structure; such as Figure 1 )

[0004] Difficulties in machining narrow-channel super-large aspect ratio blades: The material is a superalloy GH4169: It has high hardness, and large internal stress is generated during the milling of the blade profile, causing the part to deform. The blade profile tolerance and position accuracy requirements are high, and the machining difficulty is large; the blade profile torque is large, and it cannot be machined in the vertical direction, and it needs to be machined by the method of tilting the tool angle; the machining blade profile length is 180 mm, the channel width is 8.5 mm, and the number of blades is large. The spacing between the blades is small and the throat is narrow, and the machining difficulty is large (such as Figure 2 )

[0005] CN115586750B proposes a method for machining blades of an aero-engine integral blisk in the whole process of milling, including the following steps: Step 1, the rough milling process of the blade without interference in the whole process: Step 2, the finish milling process of the blade without interference in the whole process: Step 2.1, before starting the numerical control machining program, the operator installs the cutting tools used in the machining process and puts them into the equipment tool magazine; Step 2.2, start the numerical control machining program, first automatically update the machining status of the blade and the tool life; Step 2.3, confirm the current machining step of the blade; Step 2.4, confirm the tool life and complete the machining of all blades. Remove the artificial interference in the machining process, realize automatic tool setting and tool change, automatically identify the blade serial number, automatically judge the tool life, and automatically judge whether the tool is correctly installed, improve the machining efficiency, reduce the manufacturing cost, and improve the product quality.

[0006] However, the stress in blade machining cannot be solved by tool change. Especially when machining a 1.8-mm-thick blade crown, the stress of the milling cutter on the blade during machining will cause deformation of the blade. Moreover, fundamental improvements need to be made to the tool fixture and machining process for machining the integral blisk of narrow-channel super-large aspect ratio blades in order to completely machine the integral blisk of narrow-channel super-large aspect ratio blades. Summary of the Invention

[0007] The present invention proposes a machining process for the integral blisk of narrow-channel super-large aspect ratio blades of an aero-engine: especially for the outer end blades of the integral blisk with a closed-loop structure, the present invention scheme is used for machining.

[0008] The technical solution of the present invention is an efficient machining method for an aero-engine integral blisk, adopting a machining method of layer-by-layer rough and finish milling. For rough milling, a customized straight-shank milling cutter is used, and for finish milling, a "lollipop"-type milling cutter is used to improve the machining accuracy of the milled blade profile and reduce part deformation;

[0009] When rough milling the blade profile, a margin of 0.8±0.3 mm is left on the blade profile and the flow path surface; then, a stress relief method is added to eliminate the internal stress generated by rough milling. The internal stress generated by rough milling is eliminated by heat-treating the workpiece at a temperature of 380-580°C and then cooling it to room temperature to reduce part deformation. Then, finish milling is carried out by using the "lollipop" milling cutter for multiple cuts with a small margin to control the part deformation amount and ensure the part dimensions;

[0010] The outer end blades of the integral blisk are in a structure within an outer closed loop; for the integral blisk of narrow and long blades, the outer ends of the blades are fixed to the inner side of the outer closed loop, the channels between the blades are narrow, and the blades have a large twist angle (the blade cross-section has a large-curvature arc, and a straight cutting tool cannot penetrate through all the exposed surfaces of the channel from one side of the channel to machine the channel). The blade profile can be a narrow-channel super-large aspect ratio blade; when finish milling, a machining method of turning over on both sides is adopted, that is, the cutter feeds from both sides of the closed loop respectively. For rough milling, a special straight-shank milling cutter is used ( Figure 3) For finish milling, a specially customized lollipop-shaped milling cutter is used.

[0011] The machining method is to machine layer by layer from the center of the blade to both ends of the blade (the contact points with the central ring and the edge ring) until the root of the blade. When feeding from each side, the feed starts from the central part of the blade. After each layer of machining is completed, it is machined layer by layer towards both ends of the blade, with at least 20 layers. After each layer in the length direction of the blade is machined, the next layer is machined. This is the same for both rough machining and finish machining until the machining of the root layer of the blade is completed. The characteristic of the machining method of the present invention is that even when the central part of the blade reaches the thin dimension after machining, since both ends of the blade have not been machined yet, there is a relatively thick dimension to support the machining, so that the thin dimension will not be deformed during milling until the machining is completed.

[0012] During rough machining, feeding can also be done from each side, starting from the central part of the blade; during finish machining, feeding is done separately from both sides of the ring, starting from the central part of the blade; after each layer of machining is completed, it is machined layer by layer towards both ends of the blade, with at least 20 layers.

[0013] Adopt a machining method of layer-by-layer rough and finish milling. For rough milling, a customized straight shank milling cutter is used, and for finish milling, a "lollipop" - shaped milling cutter is used to improve the machining accuracy of the blade profile and reduce part deformation;

[0014] When rough milling the blade profile, a margin of 0.8 ± 0.3 mm is left on the blade profile and the flow passage surface; then, by adding a stress relief method, the internal stress generated by rough milling is eliminated. To eliminate the internal stress generated by rough milling, the workpiece is heat-treated at a temperature of 300 - 450 °C and then cooled to room temperature to reduce part deformation. Then, finish milling is carried out with a "lollipop" milling cutter by multiple cuts with a small margin to control the part deformation amount and ensure the part dimensions.

[0015] The machining method is to machine layer by layer from the center of the blade to both ends of the blade (the contact points with the central ring and the edge ring) until the root of the blade. When feeding from each side, the feed starts from the central part of the blade. After each layer of machining is completed, it is machined layer by layer towards both ends of the blade, with at least 20 layers. After each layer in the length direction of the blade is machined, the next layer is machined. This is the same for both rough machining and finish machining. The characteristic of the machining method of the present invention is that even when the central part of the blade reaches the thin dimension after machining, since both ends of the blade have not been machined yet, there is a relatively thick dimension to support the machining, so that the thin dimension will not be deformed during milling until the machining is completed.

[0016] During rough machining, feeding can also be done from each side, starting from the central part of the blade;

[0017] During finish machining, feeding is done separately from both sides of the ring, starting from the central part of the blade; after each layer of machining is completed, it is machined layer by layer towards both ends of the blade, with at least 20 layers.

[0018] The cutting head diameter of the tool of the "lollipop" type milling cutter is based on the slot width of the blade profile and the twist angle in the machining process, and as much cutting as possible should be carried out. At the same time, the tool life should be considered. Therefore, the cutting head and the tool shank are prepared into a tapered structure, which should not only ensure rigidity but also, in the case of a large twist angle, machine all blade profiles and meet the accuracy requirements.

[0019] The reference for finish milling the blade profile and finish turning must be kept consistent. Therefore, after finish milling the blade profile, the measured value from the blade profile stacking axis to the reference end is measured by a three-coordinate measuring device and recorded. When finish turning, the machining allowance of the machining surface is judged according to the recorded measured value to eliminate the reference deviation caused by the cumulative tolerance.

[0020] The outer end blades of the integral blisk are structured within an outer closed ring; it is an integral blisk with narrow and long blades. The outer ends of the blades are fixed to the inner side of the outer closed ring, the channels between the blades are narrow, and the blades have a large twist angle (the blade cross-section has a large-curvature arc) with a large blade profile. It can be a blade with an extremely large length-width ratio in a narrow channel. When finish milling, a machining method of turning the workpiece over on both sides is adopted, that is, cutting from both sides of the closed ring respectively. For rough milling, a special straight shank milling cutter ( Figure 3 ) is used, and for finish milling, a specially customized "lollipop" type milling cutter is used to improve the machining accuracy of the blade profile and reduce part deformation ( Figure 4 ).

[0021] Beneficial effects: The present invention is a processing implementation process for an integral blisk of narrow-channel blades with an extremely large length-width ratio in an aero-engine. In particular, the outer end blades of the integral blisk are structured within a closed ring and processed using the solution of the present invention. Only one tool change is required. During the tool change, heat treatment of the workpiece is carried out. When reinstalling the workpiece, as long as the reference is aligned, the stress in the blade machining can be eliminated, and the stress of the milling cutter on the blade during machining will not cause deformation of the blade. With the addition of the heat treatment process, it is possible to machine narrow-channel blades with an extremely large length-width ratio, especially the integral blisk of narrow-channel blades with an extremely large length-width ratio. The outer ends of the blades of this kind of blisk are structured within an outer closed ring. Brief Description of the Drawings

[0022] Figure 1 It is a schematic diagram of the blade profile structure of the present invention;

[0023] Figure 2 It is a schematic diagram of the structure of the present invention;

[0024] Figure 3 It is a schematic diagram of rough milling using a special straight shank milling cutter according to the present invention; Figure 3 The left and right figures in it correspond to cutting from two sides of the ring;

[0025] Figure 4 It is a schematic diagram of the machining of the "lollipop" type milling cutter according to the present invention; Figure 4 The left and right figures in it correspond to cutting from two sides of the ring;

[0026] Figure 5 Schematic diagram of the processing structure for supporting the blade shoulder and blade crown by using a spacer ring according to the present invention. Specific embodiments

[0027] As shown in the figure, a processing method of rough and finish milling in layers is adopted. For rough milling, a customized straight shank milling cutter (such as Figure 3 ) is used, and for finish milling, a specially customized "lollipop" type milling cutter is used to improve the machining accuracy of the blade profile and reduce part deformation (such as Figure 4 ).

[0028] The material is GH4169, with high hardness and high requirements for blade profile accuracy. Therefore, after rough milling the blade profile (leaving a 0.5 mm allowance on the blade profile and the flow path surface), a stress relief method is adopted to eliminate the internal stress generated by rough milling, reduce part deformation, and then use the "lollipop" milling cutter to perform finish milling with small allowances for multiple cuts to control the part deformation and ensure the part dimensions (see the following table for processing parameters).

[0029] Since the blade length is 180 mm, the blade will deform radially during milling. When rough and finish milling the blade profile, a tooling equal-height spacer ring is used to support the blade shoulder and blade crown. The tooling is made according to the measured values of the part. The number of blade profiles is 89. When roughing, a symmetric and layered milling method is selected for processing to reduce deformation (such as Figure 5 ).

[0030] The reference for finish milling the blade profile and finish turning must be kept consistent. Therefore, after finish milling the blade profile, the measured value from the blade profile stacking axis to the reference end is measured by a coordinate measuring machine and recorded. When finish turning, the allowance of the machining surface is judged according to the recorded measured value to eliminate the reference deviation caused by cumulative tolerance.

[0031] Overall blisk processing implementation process plan for narrow-channel ultra-large aspect ratio blades of an aeroengine: Especially, the outer-end blades of the overall blisk are of a closed-loop structure. For the narrow and long overall blisk, its outer-end blades are of a closed-loop structure, the channel is too narrow, and the twist angle of the blade profile is relatively large. Therefore, the machining of the entire circle of blade profiles is extremely difficult and the existing technology has a long processing cycle. Group processing is adopted. When finish milling, a processing method of turning over both sides is used. For rough milling, a special straight shank milling cutter ( Figure 3 ) is used, and for finish milling, a specially customized bar-shaped milling cutter is used to improve the machining accuracy of the blade profile and reduce part deformation ( Figure 4) For the cutter head diameter of the "lollipop" type milling cutter, it is based on the slot width of the blade profile and the twist angle during the machining process, aiming to cut as much as possible while considering the tool life. Therefore, the cutter head and the tool shank are prepared in a tapered structure to ensure rigidity and, in the case of a large twist angle, machine all blade profiles and meet the accuracy requirements. The structure of the "lollipop" type milling cutter is such that the cutting edge of the lollipop is located at the cutter head (sugar head) of the lollipop. Two to four cutting edges are acceptable. The cutter head is connected to the rear of the tool body through a thinner neck, so that the machining will not be affected by the diameter of the tool shank during processing. The cutter head cutting edge of the lollipop has a long machining life.

[0032] The machining method is to layer process from the center of the blade to both ends of the blade (where it contacts the central ring and the edge ring) to the root of the blade. Especially during finish machining, when feeding on each side, the machining starts from the central part of the blade first. After each layer of machining is completed, it is processed layer by layer towards both ends of the blade. During rough machining, feeding can also be done on each side, and it also starts from the central part of the blade first.

[0033] During finish machining, feeding is done separately on both sides of the ring: starting from the central part of the blade first; after each layer of machining is completed, it is processed layer by layer towards both ends of the blade, preferably with more than 50 layers of better layering (the feed per layer is 1 ± 0.3 mm). After each layer of machining in the length direction of the blade is completed, then proceed to the machining of the next layer. Both rough machining and finish machining can be done in this way until the machining of the root layer of the blade is completed. When machining each blade, the central part of the blade is machined first. First, machine half of the length of the blade in the outer ring direction, and then machine half of the length of the blade in the axial direction, with at least 40 layers of layering; this can overcome the influence of stress deformation during the machining of each blade; during rough machining, water can also be fed from the center of the blade (at this time, the influence on stress is relatively small). The characteristic of the machining method of the present invention is that even when the central part of the blade reaches the final size of the thin sheet after machining, since both ends of the blade have not been machined yet, there is a relatively thick size to support the machining, so that the thin size will not be deformed during milling until the machining is completed. Feeding separately on both sides of the ring can machine all the surfaces that need to be machined.

[0034] Overall blade ring machining process route for narrow-channel ultra-large aspect ratio blades:

[0035] A10 Incoming material inspection → A20 Rough turning of the intake end → A30 Rough turning of the exhaust end → A40 Drilling and boring positioning holes → A50 Rough milling of the blade profile and flow channel → A60 Stress relief heat treatment, treated at 550 °C for 2 hours and then cooled → A70 Turning the reference → A80 Semi-finish turning of the intake end → A90 Semi-finish turning of the exhaust end → A100 Boring and enlarging the positioning holes → A110 Finish milling of the blade profile and flow channel →

[0036] A120 Sampling inspection of blade profile and flow path → A130 Polishing of blade profile and flow path → A140 Inspection of blade profile and flow path → A150 Precision turning of exhaust end → A160 Precision turning of intake end → A170 Drilling and milling of intake end holes → A180 Benchwork repair → A190 Fluorescent penetrant inspection

[0037] → A200 Final inspection.

[0038] (See the following table for processing parameters)

[0039] Processing parameters for milling blade profile

[0040]

[0041]

[0042] As described above, it is only a specific embodiment of the present invention and cannot limit the scope of the invention implementation. Therefore, the replacement of equivalent components or equivalent changes and modifications made according to the protection scope of the present invention should still fall within the scope covered by this application.

Claims

1. An efficient machining method for an integral blisk of an aeroengine, characterized in that, The outer blades of the blisk are structured within the outer closed ring; for the blisk with narrow and long blades, the outer ends of the blades are fixed to the inner side of the outer closed ring, the inter-blade channels are narrow, and the blades have a large twist angle profile. A layered roughing and finishing milling process is adopted. For rough milling, a customized straight shank milling cutter is used, and for finishing milling, a "lollipop" type milling cutter is used to improve the machining accuracy of the blade profile and reduce part deformation. When rough milling the blade profile, a 0.8 ± 0.3 mm allowance is left on the blade profile and the flow path surface; then, a stress relief method is added to eliminate the internal stress generated during rough milling. To eliminate the internal stress generated during rough milling, the workpiece is heat-treated at a temperature of 380 - 580 °C and then cooled to room temperature to reduce part deformation. Then, a "lollipop" milling cutter is used for multiple cuts with a small allowance for finishing milling to control the part deformation and ensure the part dimensions; a two-sided turning-over machining method is adopted during finishing milling, that is, the cutter feeds from both sides of the closed ring respectively. A special straight shank milling cutter is used for rough milling, and a lollipop type milling cutter is used for finishing milling.

2. The high-efficiency machining method of the integral blisk of an aeroengine according to claim 1, characterized in that, The machining method is from the center of the blade to both ends respectively, and is processed layer by layer to the root of the blade. When feeding from each side, the cutter feeds first at the central part of the blade. After each layer of machining is completed, it is processed layer by layer towards both ends of the blade. At least 20 layers are required for layering. After each layer of machining in the length direction of the blade is completed, the machining of the next layer is entered.

3. The high-efficiency machining method of the integral blisk of an aeroengine according to claim 2, characterized in that The feed amount for each layer is 1 ± 0.3 mm.

4. The high-efficiency machining method of the integral blisk of an aeroengine according to claim 1, characterized in that, The reference for finishing milling the blade profile and finishing turning must be kept consistent. The measured value from the blade profile stacking axis to the reference end is measured by a three-coordinate measuring machine and recorded. During finishing turning, the allowance of the machining surface is judged according to the recorded measured value to eliminate the reference deviation caused by cumulative tolerance.

5. The high-efficiency machining method of the integral blisk of an aeroengine according to claim 1, characterized in that, The structure of the "lollipop" type milling cutter is that the cutting edge of the lollipop is set at the position of the lollipop cutter head. Two to four cutting edges can be provided, and the cutter head is connected to the rear part of the cutter body through a thinner cutter neck.

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