Method for machining high-temperature alloy turbine with end teeth and closed blades

Abstract

The invention relates to the technical field of machining, in particular to a machining method of a high-temperature alloy turbine with end teeth and a closed blade, which is characterized in that the traditional turbine blade needing a large amount of numerical control milling is changed into precision casting molding, so that the machining amount is greatly reduced, and the machining period is remarkably shortened; the special end tooth milling tool is designed according to the high-precision requirement of turbine end tooth machining, accurate positioning and clamping are achieved in a conical surface expansion mode, high-precision milling of the end teeth at the two ends is completed at a time on a five-axis numerical control machine tool, the coaxiality of the end teeth relative to an inner hole is effectively controlled, and the machining precision is guaranteed. Meanwhile, a special taper mandrel and an overspeed test tool are respectively designed for dynamic balance correction and overspeed test, so that the actual assembly state is effectively simulated, the test is prevented from loosening, and a complete, efficient and reliable special tool guarantee system is formed; therefore, the problems of long processing period, difficulty in precision control and lack of special tool guarantee are systematically solved.

Description

Technical Field

[0001] This invention relates to the field of machining technology, and in particular to a method for machining a high-temperature alloy turbine with end teeth and enclosed blades. Background Technology

[0002] With the rapid development of industry, steam turbines are widely used in petrochemical, energy recovery, and other fields. As a key component of the steam turbine rotor system, the turbine's machining accuracy and operational reliability are of paramount importance. Traditional steam turbine connections often employ a hot-sleeve keyed positioning and anti-rotation structure, which carries the risk of the hot-sleeve getting stuck. Furthermore, to withstand the harsh environments of petrochemical plants and other industries, turbine blades need to possess stronger corrosion resistance. Therefore, there is an urgent need for a high-temperature alloy turbine with end teeth that is easy to assemble and disassemble and has strong corrosion resistance.

[0003] However, such turbines have complex structures (combining end teeth and enclosed blades), and are mostly made of difficult-to-machine high-temperature alloys such as GH4169. Their machining process involves multiple stages, including casting, high-precision turning, milling, dynamic balancing, and overspeed testing. The process route is complex, and there are special requirements for tooling, fixtures, and machining sequence. Existing general machining methods have the following problems: 1. Traditional blades are machined using CNC milling, which involves numerous processes, long cycles, and high costs; 2. The end tooth structure requires high precision, and there is a lack of dedicated tooling to ensure consistent machining. 3. Dynamic balancing and overspeed testing are difficult to perform, posing safety hazards; 4. The entire processing lacks a systematic process route and quality control points.

[0004] Therefore, it is necessary to develop a complete, efficient, and reliable specialized processing method to solve the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of this invention is to provide a method for machining a high-temperature alloy turbine with end teeth and enclosed blades, which solves the problems of long machining cycle, difficult precision control, and lack of dedicated tooling in the existing technology for high-temperature alloy turbines with end teeth that have strong corrosion resistance.

[0006] To achieve the above objectives, the present invention provides a method for machining a high-temperature alloy turbine with end teeth and closed blades, the method comprising the following steps: Blank preparation: A turbine blank with enclosed blades is obtained by precision casting, and then scribing is performed to determine the reference. Initial machining: The short end and long end of the turbine are rough machined in sequence, with allowance for finishing. Preliminary flaw detection: Ultrasonic testing is performed on the workpiece after rough machining to check for casting and machining defects; Finishing: The short end and long end of the turbine are finished sequentially. The positioning inner hole, end teeth and outer gas seal structure of the short end are finished in one clamping. Then the total length and end teeth of the long end are finished with the machined surface as a reference. CNC milling: The workpiece is clamped using a special end-tooth milling fixture, and the end tooth profiles at both ends of the turbine are milled on a five-axis CNC machine tool. Fitter processing: Remove burrs from the workpiece and mark it with lettering; Dynamic balancing correction: The turbine is clamped using a tapered mandrel tooling to perform double-sided dynamic balancing correction; Overspeed verification: The turbine is clamped using a dedicated overspeed test fixture to conduct an overspeed reliability test; Secondary flaw detection: Surface penetrant testing is performed on the turbine after the overspeed test as a final quality inspection.

[0007] In the blank preparation step, the dimensional accuracy of the precision-cast closed blade reaches CT4 level, and the surface roughness is Ra3.2.

[0008] The specific contents of the initial turning process are as follows: the turbine blank is clamped in a three-jaw chuck on a lathe, and after alignment, the short end of the turbine is rough turned using coated carbide tools, the spindle speed is 40m / min, the cutting depth is 0.5mm, and a 1mm finishing allowance is reserved on each side; then the turbine blank is turned around and clamped, and the long end of the turbine is rough turned using the same process parameters.

[0009] The specific contents of the precision turning process are as follows: first, precision turn the short end, and complete the precision turning of the positioning inner hole, the inner and outer circles and the slope of the end tooth part, and the outer circle air seal in one clamping, so as to ensure that the coaxiality of the outer circle relative to the inner hole is not greater than 0.015mm and the coaxiality of the air seal relative to the inner hole is not greater than 0.025mm. Next, use the already precision-machined short end outer circle for positioning, and employ a soft three-jaw clamp to ensure that the workpiece end face is flat. Align the machined inner hole and ensure that the end face runout is no more than 0.01mm. Then, precision machine the total length of the turbine, the inner and outer circles and the camber of the long end teeth to ensure that the positional runout between the long end teeth and the short end teeth meets the requirements of the drawing.

[0010] In the CNC milling process, the special end-tooth milling fixture used includes a base, an inner pressure sleeve, and a clamping screw. The inner pressure sleeve has a positioning surface that mates with the inner bore and end face of the turbine, as well as a conical surface structure for clamping. By applying force with the clamping screw, the conical surface of the inner pressure sleeve is made to expand and tighten the inner bore of the workpiece. During milling, it is necessary to ensure that the coaxiality of the end teeth at both ends relative to the inner hole is no greater than 0.015mm.

[0011] The dynamic balancing tooling used in the dynamic balancing correction step is a tapered mandrel. The mandrel is tightened to fit the inner hole of the turbine by tapping, and the dynamic balancing accuracy needs to reach the G1 level.

[0012] The specific content of the overspeed verification step is as follows: using a special overspeed test fixture including a mandrel, a first-stage washer, a second-stage washer, a butterfly spring washer, a first-stage locking nut, and a second-stage locking nut, the turbine is clamped and run on an overspeed test machine at a speed of 1.2 times the turbine's operating speed for no less than 3 minutes.

[0013] The preliminary flaw detection step is performed using ultrasonic testing according to GB / T1786-2000 standard, with a quality acceptance level of A; the secondary flaw detection step is performed using penetrant testing according to JB / T5000.15-2007 standard, with an acceptance level of not less than 1.

[0014] This invention discloses a high-temperature alloy turbine machining method with end teeth and enclosed blades. By replacing the traditional turbine blades, which require extensive CNC milling, with precision casting, the amount of machining is significantly reduced, and the machining cycle is shortened considerably. To address the high-precision requirements of turbine end tooth machining, a dedicated end tooth milling fixture is designed. Precise positioning and clamping are achieved through a conical surface expansion method, enabling high-precision milling of both end teeth in a single operation on a five-axis CNC machine tool. This effectively controls the coaxiality of the end teeth relative to the inner hole, ensuring machining accuracy. Simultaneously, dedicated tapered mandrels and overspeed testing fixtures are designed for dynamic balancing and overspeed testing, effectively simulating actual assembly conditions and preventing loosening during testing. This forms a complete, efficient, and reliable dedicated tooling support system, systematically solving the problems of long machining cycles, difficult precision control, and lack of dedicated tooling support. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the turbine structure processed by the high-temperature alloy turbine with end teeth and closed blades provided by the present invention.

[0017] Figure 2 This is a schematic diagram of the structure of the special end-tooth milling fixture provided by the present invention.

[0018] Figure 3 This is a schematic diagram of the base in the special end-tooth milling fixture provided by the present invention.

[0019] Figure 4 This is a schematic diagram of the inner pressure sleeve in the special end-tooth milling fixture provided by the present invention.

[0020] Figure 5 This is a schematic diagram of the structure of the balancing mandrel of the tapered mandrel tooling provided by the present invention.

[0021] Figure 6 This is a schematic diagram of the structure of the special overspeed testing fixture provided by the present invention.

[0022] Figure 7 This is a schematic diagram of the mandrel in the special overspeed testing fixture provided by the present invention.

[0023] Figure 8 This is a schematic diagram of the structure of the primary washer in the special overspeed testing fixture provided by the present invention.

[0024] Figure 9 This is a schematic diagram of the secondary washer in the special overspeed testing fixture provided by the present invention.

[0025] Figure 10 This is a schematic diagram of the line-drawing steps provided by the present invention.

[0026] Figure 11 This is a schematic diagram of the roughing short end step provided by the present invention.

[0027] Figure 12 This is a schematic diagram of the rough machining of the long end provided by the present invention.

[0028] Figure 13 This is a schematic diagram of the precision machining of the short end provided by the present invention.

[0029] Figure 14 This is a schematic diagram of the precision machining process for the long end provided by the present invention.

[0030] 1. Base, 2. Inner pressure sleeve, 3. Clamping screw, 4. Mandrel, 5. Primary washer, 6. Secondary washer, 7. Butterfly spring washer, 8. Primary locking nut, 9. Secondary locking nut. Detailed Implementation

[0031] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0032] Please see Figures 1 to 14 This invention provides a method for machining a high-temperature alloy turbine with end teeth and closed blades, the method comprising the following steps: Blank preparation: A turbine blank with enclosed blades is obtained by precision casting, and then scribing is performed to determine the reference. Initial machining: The short end and long end of the turbine are rough machined in sequence, with allowance for finishing. Preliminary flaw detection: Ultrasonic testing is performed on the workpiece after rough machining to check for casting and machining defects; Finishing: The short end and long end of the turbine are finished sequentially. The positioning inner hole, end teeth and outer gas seal structure of the short end are finished in one clamping. Then the total length and end teeth of the long end are finished with the machined surface as a reference. CNC milling: The workpiece is clamped using a special end-tooth milling fixture, and the end tooth profiles at both ends of the turbine are milled on a five-axis CNC machine tool. Fitter processing: Remove burrs from the workpiece and mark it with lettering; Dynamic balancing correction: The turbine is clamped using a tapered mandrel tooling to perform double-sided dynamic balancing correction; Overspeed verification: The turbine is clamped using a dedicated overspeed test fixture to conduct an overspeed reliability test; Secondary flaw detection: Surface penetrant testing is performed on the turbine after the overspeed test as a final quality inspection.

[0033] In this embodiment, by replacing the traditional turbine blades, which require extensive CNC milling, with precision casting, the amount of machining is significantly reduced, and the machining cycle is considerably shortened. To address the high-precision requirements of turbine end-tooth machining, a dedicated end-tooth milling fixture was designed. This fixture uses a tapered surface tightening method to achieve precise positioning and clamping, enabling high-precision milling of both end teeth in a single operation on a five-axis CNC machine tool. This effectively controls the coaxiality of the end teeth relative to the inner hole, ensuring machining accuracy. Simultaneously, dedicated tapered mandrels and overspeed testing fixtures were designed for dynamic balancing and overspeed testing, effectively simulating actual assembly conditions and preventing loosening during testing. This forms a complete, efficient, and reliable dedicated tooling support system, systematically solving the problems of long machining cycles, difficult precision control, and lack of dedicated tooling support.

[0034] Furthermore, in the blank preparation step, the dimensional accuracy of the precision-cast closed blade reaches CT4 level, and the surface roughness is Ra3.2.

[0035] In this embodiment, precision casting technology (wax pattern making, shell forming, casting, and post-processing) is used to directly form the closed blade, which significantly reduces the amount of machining compared to traditional blade milling. The dimensional accuracy of CT4 and surface roughness of Ra3.2 are sufficient to meet aerodynamic performance requirements, while saving considerable CNC machining time and tooling costs. The scribing process uses the air inlet side of the blade as a reference to ensure consistent reference for subsequent machining.

[0036] Furthermore, the specific content of the initial turning process is as follows: the turbine blank is clamped in a three-jaw chuck on a lathe, and after alignment, the short end of the turbine is rough turned using coated carbide tools, the spindle speed is 40m / min, the cutting depth is 0.5mm, and a 1mm finishing allowance is reserved on each side; then the turbine blank is turned around and clamped, and the long end of the turbine is rough turned using the same process parameters.

[0037] In this embodiment, since the turbine material is GH4169 high-temperature alloy, which is a difficult-to-machine material, a lower cutting speed and a smaller depth of cut parameter can reduce tool wear and work hardening. A 1mm finishing allowance on each side ensures sufficient machining accuracy while avoiding excessive material waste and machining time. This step lays a good foundation for subsequent finishing.

[0038] Furthermore, the specific content of the precision turning process is as follows: first, precision turn the short end, and complete the precision turning of the positioning inner hole, the inner and outer circles and the slope of the end tooth part, and the outer circle air seal in one clamping, ensuring that the coaxiality of the outer circle relative to the inner hole is not greater than 0.015mm, and the coaxiality of the air seal relative to the inner hole is not greater than 0.025mm. Next, use the already precision-machined short end outer circle for positioning, and employ a soft three-jaw clamp to ensure that the workpiece end face is flat. Align the machined inner hole and ensure that the end face runout is no more than 0.01mm. Then, precision machine the total length of the turbine, the inner and outer circles and the camber of the long end teeth to ensure that the positional runout between the long end teeth and the short end teeth meets the requirements of the drawing.

[0039] In this embodiment, multiple machining operations are completed in a single clamping during the precision turning of the short end, minimizing clamping errors and ensuring the positional accuracy between key features such as the inner hole, outer diameter, and air seal. The soft three-jaw chuck better adapts to the machined surface, avoiding scratches and deformation. The runout of the inner hole and end face is controlled within 0.01mm, providing a precise reference for the machining of the end teeth.

[0040] Furthermore, in the CNC milling process, the dedicated end milling fixture used includes a base, an inner pressure sleeve, and a clamping screw; The inner pressure sleeve has a positioning surface that mates with the inner bore and end face of the turbine, as well as a conical surface structure for clamping. By applying force with the clamping screw, the conical surface of the inner pressure sleeve is made to expand and tighten the inner bore of the workpiece. During milling, it is necessary to ensure that the coaxiality of the end teeth at both ends relative to the inner hole is no greater than 0.015mm.

[0041] In this embodiment, the base is used to install and fix it on the machine tool worktable; the inner pressure sleeve is disposed on the base and has a cylindrical positioning surface that mates with the inner hole of the turbine, an end face positioning surface that mates with the end face of the turbine, and an outer conical surface clamping structure; the clamping screw is threaded to the base, and its end acts on the inner pressure sleeve, causing the inner pressure sleeve to generate axial displacement and radially tighten the inner hole of the workpiece through the conical surface structure. The taper of the inner pressure sleeve is 20°. The turbine is clamped by the special end milling fixture, which can generate a uniform radial tightening force through axial pressure and achieve accurate axial positioning, avoiding clamping deformation that may be caused by traditional fixtures. It is particularly suitable for thin-walled and high-precision parts.

[0042] Furthermore, the dynamic balancing tooling used in the dynamic balancing correction step is a tapered mandrel. The mandrel is tightened to fit the inner hole of the turbine by tapping, and the dynamic balancing accuracy needs to reach the G1 level.

[0043] In this embodiment, since the turbine operates at a speed as high as 13750 rpm, the dynamic balancing accuracy directly affects the smoothness and lifespan of the equipment. The tapered mandrel design is simple and reliable, achieving a tight fit with a slight tap, and is easy to assemble and disassemble. The G1 level of balancing accuracy is suitable for high-precision rotating machinery. By grinding away weight at designated locations on the wheel, the imbalance is eliminated, providing assurance for subsequent overspeed tests and actual operation.

[0044] Furthermore, the specific content of the overspeed verification step is as follows: using a special overspeed test fixture including a mandrel, a primary washer, a secondary washer, a butterfly spring washer, a primary locking nut, and a secondary locking nut, the turbine is clamped and run on an overspeed test machine at a speed of 1.2 times the turbine's operating speed for no less than 3 minutes.

[0045] In this embodiment, the mandrel passes through the turbine's inner bore and provides end-face positioning. The primary washer and the secondary washer are respectively fitted onto the mandrel to press against the simulated impeller contact surface. The disc spring washer is fitted onto the mandrel and located between the washer and the locking nut. The primary locking nut and the secondary locking nut are threaded to the end of the mandrel to press against the entire assembly. Overspeed testing is a crucial step in verifying the structural strength and safety of the turbine. The specialized overspeed testing fixture simulates the turbine's assembly state during actual operation, with the primary and secondary washers corresponding to the clamping surfaces of different impellers. The disc spring washer provides continuous preload during high-speed rotation, preventing loosening due to vibration and avoiding the risk of instantaneous spindle breakage. An overspeed condition of 13750 rpm (1.2 times the operating speed) and a duration of 3 minutes fully verify the turbine's reliability under extreme operating conditions.

[0046] Furthermore, the preliminary flaw detection step is performed using ultrasonic testing according to GB / T1786-2000 standard, with a quality acceptance level of A; the secondary flaw detection step is performed using penetrant testing according to JB / T5000.15-2007 standard, with an acceptance level of not less than 1.

[0047] In this embodiment, the two flaw detection processes are arranged after rough machining and after the overspeed test, respectively, forming a comprehensive quality control system. The ultrasonic flaw detection after rough machining mainly checks for internal defects in the blank, avoiding ineffective finishing of defective parts. The penetrant testing after the overspeed test mainly checks for microcracks on the surface and near the surface, ensuring the structural integrity of the turbine after high-speed rotation.

[0048] Furthermore, in the precision turning step and the CNC milling step, coated carbide tools or cubic boron nitride (CBN) tools are selected for high-temperature alloy materials. In summary, the overall process route for machining the high-temperature alloy turbine with end teeth and enclosed blades provided in this technical solution is as follows: Precision casting: Turbine blades are precision cast (wax pattern making, shell forming, pouring, post-processing), saving the machining and assembly process of common turbine blades and greatly shortening the subsequent processing cycle.

[0049] Marking: The blades do not require machining. Using the air intake side of the blade as a reference, mark the end face lines on both sides to check the precision casting allowance, identify any allowance issues in advance, and avoid unnecessary subsequent machining.

[0050] Rough turning of the short end: Clamp the short end with a three-jaw chuck, align it, and then turn to remove the excess material from the short end to prepare for finish turning (leave a 1mm finish turning allowance). Use carbide inserts, spindle speed S=40, depth of cut 0.5.

[0051] Rough turning of the long end: Clamp the long end with a three-jaw chuck, align it, and then turn to remove the excess material from the long end to prepare for finish turning (leave a 1mm finish turning allowance). Use carbide inserts, spindle speed S=40, depth of cut 0.5.

[0052] Preliminary flaw detection: Ultrasonic testing, performed according to GB / T1786-2000, with a quality acceptance level of A. This checks for casting defects, allowing for early detection and prevention of unnecessary subsequent processing.

[0053] Finish turning of the short end: finish turning the positioning inner hole, the inner and outer circles and the taper of the end teeth, and the outer circle gas seal (carbide inner hole turning tool, speed S=30-35, feed F=0.1-0.12; carbide outer circle turning tool, speed S=25-30, feed F=0.1-0.15; carbide grooving tool, speed S=25-30, feed F=0.05-0.08), complete the machining in one clamping, and ensure the overall consistency of the machining as much as possible (coaxiality of the outer circle relative to the inner hole 0.015, coaxiality of the gas seal relative to the inner hole 0.025).

[0054] Finish turning the long end: Clamp the outer diameter with a soft three-jaw chuck, flatten the end face, align the already machined inner hole and end face runout to no more than 0.01, finish turning the total length, inner and outer diameters and chamfers of the end teeth (carbide inner hole turning tool, speed S=30-35, feed F=0.1-0.12; carbide outer diameter turning tool, speed S=25-30, feed F=0.1-0.15), ensuring the runout requirements of the end teeth on the other side.

[0055] CNC milling: Using a five-axis milling fixture, the outer diameter runout of the teeth at both ends is checked to be no greater than 0.01 mm. The teeth at both ends are then milled to ensure that the coaxiality of the teeth at both ends relative to the inner hole is 0.015 mm. The teeth are first rough milled (using a carbide end mill, speed S=800 rpm, feed F=60 rpm), and then finish milled with a carbide form end mill (speed S=800 rpm, feed F=60 rpm) to the requirements of the drawing.

[0056] Fitter work: Deburring and engraving.

[0057] Dynamic balancing correction: Perform double-sided dynamic balancing as required, grind off the weight on both sides of the wheel to achieve a precision grade of G1, and ensure stable operation in subsequent overspeed tests.

[0058] Overspeed verification: An overspeed test is conducted to ensure the reliable operation of the entire machine. The equipment is a BI5U overspeed testing machine; overspeed tools are attached. Figure 6 Overspeed rotation speed 13750rpm (1.2 times the theoretical working speed), error ±5%, duration 3min, overspeed tool tightening torque 720N.m.

[0059] Secondary flaw detection: Surface penetrant testing to check for defects. Performed according to JB / T5000.15-2007, with an acceptance level no lower than Level 1.

[0060] In this technical solution, the machining of a high-temperature alloy turbine with end teeth and enclosed blades was successfully completed through the arrangement of the casting structure of the blank, a reasonable process route, and the design of a special fixture. This solution replaces milling blades with precision casting, which greatly shortens the machining cycle. Through the reasonable process route arrangement and the design of milling tools, the consistency of the turbine as a whole and the end teeth at both ends is ensured. Dynamic balancing and overspeed tests ensure the reliability of subsequent operation.

[0061] The above description discloses only one preferred embodiment of the present invention, and should not be construed as limiting the scope of the present invention. Those skilled in the art will understand that all or part of the processes of the above embodiments can be implemented, and equivalent changes made in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A method for machining a high-temperature alloy turbine with end teeth and closed blades, characterized in that, Includes the following steps: Blank preparation: A turbine blank with enclosed blades is obtained by precision casting, and then scribing is performed to determine the reference. Initial machining: The short end and long end of the turbine are rough machined in sequence, with allowance for finishing. Preliminary flaw detection: Ultrasonic testing is performed on the workpiece after rough machining to check for casting and machining defects; Finishing: The short end and long end of the turbine are finished sequentially. The positioning inner hole, end teeth and outer gas seal structure of the short end are finished in one clamping. Then the total length and end teeth of the long end are finished with the machined surface as a reference. CNC milling: The workpiece is clamped using a special end-tooth milling fixture, and the end tooth profiles at both ends of the turbine are milled on a five-axis CNC machine tool. Fitter processing: Remove burrs from the workpiece and mark it with lettering; Dynamic balancing correction: The turbine is clamped using a tapered mandrel tooling to perform double-sided dynamic balancing correction; Overspeed verification: The turbine is clamped using a dedicated overspeed test fixture to conduct an overspeed reliability test; Secondary flaw detection: Surface penetrant testing is performed on the turbine after the overspeed test as a final quality inspection.

2. The method for machining a high-temperature alloy turbine with end teeth and closed blades as described in claim 1, characterized in that, In the blank preparation step, the dimensional accuracy of the precision-cast closed blade reaches CT4 level, and the surface roughness is Ra3.

2.

3. The method for machining a high-temperature alloy turbine with end teeth and closed blades as described in claim 2, characterized in that, The specific steps of the initial machining process are as follows: the turbine blank is clamped in a three-jaw chuck on a lathe, and after alignment, the short end of the turbine is rough machined using coated carbide tools, with a spindle speed of 40 m / min, a cutting depth of 0.5 mm, and a 1 mm finishing allowance on each side; then the turbine blank is turned around and clamped, and the long end of the turbine is rough machined using the same process parameters.

4. The method for machining a high-temperature alloy turbine with end teeth and closed blades as described in claim 3, characterized in that, The specific contents of the precision turning process are as follows: First, precision turn the short end, and complete the precision turning of the positioning inner hole, the inner and outer circles and the slope of the end tooth part, and the outer circle air seal in one clamping, so as to ensure that the coaxiality of the outer circle relative to the inner hole is not greater than 0.015mm and the coaxiality of the air seal relative to the inner hole is not greater than 0.025mm. Next, use the already precision-machined short end outer circle for positioning, and employ a soft three-jaw clamp to ensure that the workpiece end face is flat. Align the machined inner hole and ensure that the end face runout is no more than 0.01mm. Then, precision machine the total length of the turbine, the inner and outer circles and the camber of the long end teeth to ensure that the positional runout between the long end teeth and the short end teeth meets the requirements of the drawing.

5. The method for machining a high-temperature alloy turbine with end teeth and closed blades as described in claim 4, characterized in that, In the CNC milling process, the special end milling fixture used includes a base, an inner pressure sleeve, and a clamping screw; The inner pressure sleeve has a positioning surface that mates with the inner bore and end face of the turbine, as well as a conical surface structure for clamping. By applying force with the clamping screw, the conical surface of the inner pressure sleeve is made to expand and tighten the inner bore of the workpiece. During milling, it is necessary to ensure that the coaxiality of the end teeth at both ends relative to the inner hole is no greater than 0.015mm.

6. The method for machining a high-temperature alloy turbine with end teeth and closed blades as described in claim 5, characterized in that, The dynamic balancing tooling used in the dynamic balancing correction step is a tapered mandrel. The mandrel is tightened to fit the inner hole of the turbine by tapping, and the dynamic balancing accuracy needs to reach the G1 level.

7. The method for machining a high-temperature alloy turbine with end teeth and closed blades as described in claim 6, characterized in that, The specific content of the overspeed verification step is as follows: the turbine is clamped using a special overspeed test fixture including a mandrel, a primary washer, a secondary washer, a butterfly spring washer, a primary lock nut, and a secondary lock nut, and the turbine is run on an overspeed test machine at a speed of 1.2 times the turbine's operating speed for no less than 3 minutes.

8. The method for machining a high-temperature alloy turbine with end teeth and closed blades as described in claim 7, characterized in that, The preliminary flaw detection step is performed using ultrasonic testing according to GB / T1786-2000 standard, with a quality acceptance level of A. The secondary flaw detection step is performed using penetrant testing according to JB / T5000.15-2007 standard, with an acceptance level of not less than 1.

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