Grinding method and clamp for high and narrow long type sealing teeth of turbine working blade

Abstract

The application discloses a grinding method and clamp for high and narrow long type sealing teeth of turbine working blades, and aims to solve the problems of grinding burn and size precision caused by poor heat conduction of DD5 single crystal alloy, easy deformation of thin wall, and difficult cooling of deep and narrow structure. The method comprises the following steps: selecting a five-axis grinding center and configuring a high-pressure cooling system, designing a special clamp with combined positioning of tenon tooth main positioning, end surface axial limiting and blade body auxiliary support, selecting a grinding wheel with high porosity ceramic bond and online dressing; the sealing tooth processing is divided into three steps, a symmetric decreasing type circulating tool is adopted, and the remaining amount of the air inlet side and the air outlet side is removed alternately according to rough machining, semi-finishing and finishing; in the grinding process, high-pressure cooling jet is continuously applied, and the linear velocity and the feed speed are controlled in a process parameter window optimized through orthogonal test. The application realizes high-precision grinding processing without burn and recrystallization by synergistic control of heat generation and heat dissipation.

Description

Technical Field

[0001] This invention relates to the field of precision machining technology for gas turbine blades, specifically to a grinding method for high-narrow-long sealing teeth of single-crystal cast high-temperature alloy turbine working blades for gas turbines. It is particularly suitable for high-precision, non-destructive grinding of DD5 single-crystal cast high-temperature alloy material, thin-walled, high aspect ratio sealing teeth. Background Technology

[0002] Turbine blades are the core power-generating components of gas turbines, subjected to the impact of high-temperature combustion gases and high-speed rotational loads in the combustion chamber for extended periods, thus requiring extremely high material heat resistance and structural precision. Currently, my country's new gas turbine turbine blades are manufactured using DD5 single-crystal cast high-temperature alloy. This material possesses excellent high-temperature mechanical properties and structural stability, but it has high hardness and poor toughness, making it a typical difficult-to-machine material.

[0003] The turbine blades of gas turbines are equipped with tall, narrow, and long sealing teeth at the blade crown for sealing the gas passage. This structure has significant processing bottlenecks: the thinnest part of the sealing tooth has a wall thickness of only 0.5 mm and a tooth height of about 5 mm. It has a large length-to-diameter ratio and extremely poor rigidity, making it prone to elastic and plastic deformation during the grinding process; the sealing tooth cavity is narrow, and under conventional cooling methods, the coolant is difficult to effectively flush to the grinding area. The accumulation of grinding heat can easily lead to defects such as surface burns and recrystallization of the parts; at the same time, the entire contour of the sealing tooth is a curved surface, making it difficult to consistently guarantee dimensional accuracy and geometric tolerances.

[0004] Current technologies generally employ five-axis grinding centers to process these sealing teeth. However, they fail to optimize equipment selection, fixture positioning, grinding steps, and process parameters specifically for the characteristics of DD5 single-crystal alloy and its high-narrow-length, thin-walled structure. This results in low yield rates and poor stability, severely hindering the mass production and delivery schedule of gas turbine blades. Therefore, there is an urgent need to develop a grinding method for high-narrow-length sealing teeth that is compatible with single-crystal cast high-temperature alloys, can control deformation and burns, and ensures the accuracy of the arc dimensions. Summary of the Invention

[0005] This invention addresses the problems of easy deformation, burns, poor dimensional accuracy of arcs, and difficulties in cooling and chip removal during the machining of high-narrow-long sealing teeth of DD5 single-crystal cast high-temperature alloy turbine blades for gas turbines. It provides a grinding method and fixture for high-narrow-long sealing teeth of single-crystal cast high-temperature alloy turbine blades for gas turbines, achieving high-precision machining of sealing teeth without deformation, burns, or recrystallization, thus meeting the needs of mass production.

[0006] This invention is achieved through the following technical solution: A grinding method for the high, narrow, and long sealing teeth of turbine working blades includes the following steps: The blade is clamped onto the fixture, which uses the blade tenon as the main positioning reference, the exhaust side end face as the axial auxiliary reference, and a damping auxiliary support is provided on the blade body to tilt the surface to be processed of the sealing tooth by a preset angle. A grinding wheel with a ceramic bond having high porosity is selected, and diamond roller online contour dressing is performed after each profile grinding is completed during the grinding process. Symmetrical decreasing cyclic grinding is performed on the intake and exhaust sides of the sealing teeth, and the material is removed by alternating cyclic grinding in the order of roughing one side, roughing the other side, semi-finishing one side, semi-finishing the other side, finishing one side, and finishing the other side. During the cyclic grinding process, a cooling jet with a pressure of not less than 10 atmospheres is applied to the grinding zone through a high-pressure cooling system, and the grinding wheel linear velocity is controlled within the range of 15-25m / s and the feed rate is controlled within the range of 150-350mm / min.

[0007] Preferably, the preset angle of the profile to be processed of the sealing tooth is such that the normal direction of the profile forms a non-zero spatial angle with the axis of the grinding wheel spindle.

[0008] Preferably, the linear speed is 20m / s and the feed rate is 200-300mm / min in the roughing stage, and the linear speed is 18m / s and the feed rate is 180-200mm / min in the finishing stage.

[0009] Preferably, during the cyclic grinding process, the grinding of the sealing teeth is divided into three steps: the first step is to process the bottom arc of the intake side vane, the second step is to process the exhaust side vane to ensure the wall thickness and flatten the bottom, and the third step is to process the top arc of the vane. All three steps follow the symmetrical decreasing cyclic grinding sequence.

[0010] Preferably, the online profile trimming of the diamond roller is performed simultaneously with the cyclic grinding.

[0011] Preferably, the cooling jet provided by the high-pressure cooling system is injected into the contact arc area between the grinding wheel and the workpiece along the tangential direction of the grinding wheel circumference.

[0012] A jig for grinding the tall, narrow, and long sealing teeth of turbine blades, comprising: Base; A toothed positioning block is fixedly installed on the base. The toothed positioning block has a toothed positioning surface that matches the blade tenon teeth, which is used for main positioning of the blade tenon teeth. An end face positioning block is fixedly installed on the base and is used to abut against the exhaust side end face of the blade for axial positioning. A wedge-shaped positioning block is fixedly installed on the base and is used to assist in positioning the blade wedge surface. A clamping assembly, mounted on the base, is used to clamp and fix the blade to the positioning surfaces of the toothed positioning block, the end face positioning block, and the wedge face positioning block; An auxiliary support assembly, mounted on the base, is used to support the weak areas of the blade body to suppress deformation and vibration during the grinding process.

[0013] Preferably, the clamping assembly includes a hinge clamping mechanism and a screw clamping mechanism; The hinge clamping mechanism includes a hinge support, a cross hinge pressure plate, a pressure block, a hinge bolt, and a shouldered hexagonal nut. The hinge support is fixed to the base. The cross hinge pressure plate is hinged to the hinge support. The pressure block is fixedly installed on the front working surface of the cross hinge pressure plate. The lower end of the hinge bolt is hinged to the hinge support, and the upper end passes through the cross hinge pressure plate and is threadedly connected to the shouldered hexagonal nut. The screw tightening mechanism includes a support plate, a first pressure plate, a support block, a second pressure plate, and hexagonal head clamping screws. The support plate and the support block are both fixed on the base. The first pressure plate is supported on the support plate, and the second pressure plate is supported on the support block. The hexagonal head clamping screws are threaded into the threaded holes of the first pressure plate and the second pressure plate, respectively, and their ends are used to tighten the blades.

[0014] Preferably, the auxiliary support assembly includes a first cylindrical head adjustment support and a second cylindrical head adjustment support, both of which are height-adjustable cylindrical head support structures, respectively installed on the base corresponding to the weak area of ​​the blade body; each cylindrical head adjustment support is equipped with a hexagonal thin nut for locking its height position, and a tapered end set screw for tightening the adjustment support body to prevent loosening.

[0015] Preferably, the base, through the cooperation of the toothed positioning block, the end face positioning block and the wedge face positioning block, restricts the six degrees of freedom of the blade to achieve fully constrained positioning of the blade.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects: This invention reveals the core mechanism of "synergistic control of grinding heat generation and forced heat dissipation, ensuring that the peak temperature in the grinding zone is below the critical temperature for thermal damage to the workpiece material," organically coupling five key elements—grinding wheel selection, workpiece posture control, high-pressure cooling, cyclic grinding path, and process parameter window—into a thermal balance system. After machining, the sealing tooth surface of the blade shows no grinding burns or macroscopic cracks, and metallographic testing confirms the absence of recrystallization layer formation, fundamentally guaranteeing the reliability and service life of the DD5 single-crystal cast high-temperature alloy turbine blades. This invention employs a symmetrical decreasing cyclic tool arrangement strategy, alternately removing material in the sequence of "roughing one side, roughing the other side, semi-finishing one side, semi-finishing the other side, finishing one side, and finishing the other side," ensuring that the remaining material on both sides of the sealing tooth is always removed symmetrically and synchronously, and that internal stress is released uniformly. Simultaneously, the blade auxiliary support structure set in the special fixture effectively enhances the rigidity of the thin-walled sections. The synergistic effect of these two factors suppresses grinding deformation from both process and clamping perspectives, allowing the sealing tooth wall thickness and arc dimensions to be stably controlled within the design tolerance range. This invention forms a complete end-to-end system solution, encompassing equipment selection, grinding wheel selection, fixture design, process division, tool path optimization, and parameter optimization. The roughing stage prioritizes material removal efficiency, while the finishing stage prioritizes surface quality. All stages work in concert with a unified objective, ensuring both processing quality and production efficiency, thus resolving the inherent contradiction in existing technologies where grinding single-crystal high-temperature alloy sealing teeth is difficult to balance in terms of both quality and efficiency.

[0017] Furthermore, this invention specifically designs the inclined clamping posture of the workpiece, so that the normal direction of the sealing tooth's surface to be machined forms a spatial angle with the axis of the grinding wheel spindle, ensuring that the high-pressure cooling jet can penetrate the entire grinding arc zone without interference. Combined with a high-pressure cooling system of no less than 10 atmospheres, the coolant can penetrate the airflow transition layer on the grinding wheel surface, directly acting on the grinding point and quickly flushing away grinding debris. This overcomes the bottlenecks of traditional methods, such as the difficulty of coolant entry in deep and narrow structures and the burning caused by grinding debris clogging the grinding wheel pores. Attached Figure Description Figure 1 is a schematic diagram of the overall assembly structure of the special fixture of the present invention; Figure 2 is a schematic diagram of the overall assembly structure of the special fixture of the present invention from another perspective; Figure 3 is a schematic diagram of the positioning and auxiliary support part of the special fixture of the present invention, showing the EROWA center, positioning dimensions and matching structure; Figure 4 is a schematic diagram of the reference and axis system of the special fixture of the present invention, showing the center of the process ball, coordinate axis system, positioning angle and dimensional tolerance; Figure 5 is a view of the special fixture of the present invention from direction B, showing the positioning angle, surface dimensions and tolerance markings; Figure 6 is a schematic diagram of the DD cross-sectional structure of the special fixture of the present invention; Figure 7 is a schematic diagram of the specific grinding process of the present invention.

[0018] In the diagram: Base plate 1, Toothed positioning block 2, End face positioning block 3, Wedge face positioning block 4, Cross hinge pressure plate 5, Hinge support 6, Pressure block 7, First pressure plate 8, Support plate 9, Second pressure plate 10, Support block 11, Nylon cap 12, First cylindrical pin 13, Second cylindrical pin 14, Third cylindrical pin 15, Fourth cylindrical pin 16, Fifth cylindrical pin 17, Sixth cylindrical pin 18, Hexagonal head clamping screw 19, Pull stud 20, Positioning plate 21, First internal hexagonal head screw 22, Second internal hexagonal head screw 23, Shoulder hexagonal nut 24, Flexible bolt 25, Tapered end set screw 26, Hexagonal thin nut 27, Third internal hexagonal head screw 28, First cylindrical head adjusting support 29, Hexagonal thin nut 30, Fourth internal hexagonal head screw 31, Second cylindrical head adjusting support 32, First washer 33, Second washer 34. Detailed Implementation

[0019] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0020] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0021] This invention provides a grinding method for high-narrow-long sealing teeth of single-crystal cast high-temperature alloy turbine blades for gas turbines. Based on active control of the temperature in the grinding zone, the method uses collaborative design of grinding wheel characteristics, workpiece posture, cooling strategy and grinding process parameters to ensure that the highest temperature during the grinding process is always lower than the critical temperature for thermal damage of the workpiece material.

[0022] The method specifically includes the following steps: Step 1: Construct a processing environment conducive to forced cooling Equipment and Cooling Conditions: A five-axis CNC grinding center with a high-pressure cooling system and tool magazine is selected. High-pressure nozzles integrated into the tool magazine allow coolant to be precisely injected into the contact arc area between the grinding wheel and the workpiece at a pressure of no less than 10 atmospheres, tangentially along the circumference of the grinding wheel. This high-pressure jet not only achieves efficient heat exchange but also breaks through the airflow transition layer on the grinding wheel surface, directly scouring the grinding point and preventing heat accumulation.

[0023] Step 2: Determine the characteristics of the grinding wheel to reduce grinding heat generation. Grinding wheel selection: A D300×25×76.2, 86A46-3E16-QV36-50S grinding wheel was selected. The combination of corundum abrasive and ceramic binder achieves low-heat, sharp cutting. The combination of medium grit size and loose structure provides high porosity and self-sharpening properties. A safe speed limit of 50 m / s ensures that the process parameters operate within a safe window. These characteristics, along with the process parameter window of 15-25 m / s linear velocity and 150-350 mm / min used in this embodiment, and the high-pressure cooling jet of no less than 10 atmospheres, work synergistically to ensure that the peak temperature in the grinding zone is effectively suppressed below the thermal damage critical temperature of the DD5 single-crystal cast high-temperature alloy.

[0024] This grinding wheel has the following synergistic effects: High porosity: Provides larger chip space and coolant permeation channels, enhancing convective heat transfer.

[0025] Abrasive wheels: with a hardness far exceeding that of alloy carbides, they provide sharp cutting edges and can significantly reduce grinding energy, thereby reducing heat generation at the source.

[0026] Self-sharpening: After the abrasive grains are micro-fractured, new sharp cutting edges are continuously formed, maintaining a low grinding force.

[0027] Step 3: Design the workpiece clamping posture and optimize coolant accessibility. like Figures 1-6 As shown, a special fixture design is proposed: a special fixture is designed to achieve composite positioning and attitude control.

[0028] Positioning method: The blade tenon teeth are used as the main positioning reference, the exhaust side end face is used as the auxiliary axial reference, and damping auxiliary support is set on the blade body to form a stable and reliable clamping.

[0029] Attitude control concept: The blade is clamped in a fixture, which is tilted at a preset angle around the machine tool's A-axis. This angle creates a spatial angle between the normal direction of the surface to be machined on the sealing tooth and the axis of the grinding wheel spindle. This attitude ensures that the high-pressure cooling jet penetrates the entire grinding zone without interference and rapidly throws away the grinding debris and heat under centrifugal force.

[0030] Step 4: Implement a temperature-controlled cyclic grinding strategy like Figure 7 As shown, the process allocation and tool arrangement are as follows: The sealing tooth profile machining is divided into three steps: intake side vane crown, exhaust side vane crown, and top, to ensure uniform wall thickness and effective cooling.

[0031] The "symmetrical decreasing cyclic machining" tool arrangement method is adopted: instead of completing one side alone, both sides are machined alternately, i.e., rough machining one side → rough machining the other side → semi-finish machining one side → semi-finish machining the other side → finish machining one side → finish machining the other side. This method allows the allowance on both sides to be removed synchronously and symmetrically, releasing stress evenly and fundamentally controlling deformation.

[0032] Step 5: Implement grinding parameter control based on critical temperature Parameter window establishment: Through orthogonal experiments and infrared thermal imaging monitoring of grinding temperature, a set of linear velocity and feed rate process windows is determined to ensure that the peak temperature is below the material's critical thermal damage temperature (e.g., 900℃).

[0033] Specific parameter control: During the entire processing, the grinding wheel linear speed is controlled at 15-25m / s, and the feed speed is controlled at 150-350mm / min.

[0034] Roughing stage: Select a higher linear speed (e.g., 20m / s) and feed rate (200-300mm / min) within the window, prioritizing material removal efficiency.

[0035] Finishing stage: Simultaneously reduce the linear speed (e.g., 18m / s) and feed rate (180-200mm / min) to reduce grinding heat input and ensure surface accuracy.

[0036] Online correction throughout the entire process: During the machining process, after the grinding wheel completes the grinding of each profile, the built-in diamond roller performs an online profile dressing to ensure that the grinding wheel is always in a sharp state and to avoid a sharp increase in grinding force and temperature due to grinding wheel dulling.

[0037] This invention also discloses a special fixture for grinding the high-narrow-long sealing teeth of single-crystal cast high-temperature alloy turbine blades for gas turbines, such as... Figure 1 As shown, the fixture includes a base plate 1, a toothed positioning block 2, an end face positioning block 3, a wedge-shaped positioning block 4, a cross hinge pressure plate 5, a hinge support 6, a pressure block 7, a first pressure plate 8, a support plate 9, a second pressure plate 10, a support block 11, a nylon cap 12, a first cylindrical pin 13, a second cylindrical pin 14, a third cylindrical pin 15, a fourth cylindrical pin 16, a fifth cylindrical pin 17, a sixth cylindrical pin 18, a hexagonal head clamping screw 19, a pull stud 20, a positioning piece 21, a first internal hexagonal head screw 22, a second internal hexagonal head screw 23, a shouldered hexagonal nut 24, a hinge bolt 25, a tapered set screw 26, a hexagonal thin nut 27, a third internal hexagonal head screw 28, a first cylindrical head adjusting support 29, a hexagonal thin nut 30, a fourth internal hexagonal head screw 31, a second cylindrical head adjusting support 32, a first washer 33, and a second washer 34.

[0038] like Figure 1 and Figure 2 As shown, the base plate 1 is the overall mounting base of the fixture, which adopts a rigid flat plate structure. EROWA center reference, positioning holes and mounting threaded holes are machined on it. Toothed positioning block 2, end face positioning block 3, wedge face positioning block 4, hinge support 6, support plate 9, support block 11, first cylindrical head adjusting support 29 and second cylindrical head adjusting support 32 are all fixedly installed on the upper surface of the base plate 1. Pull pin 20 is fixedly installed at the bottom of the base plate 1 at the position corresponding to the EROWA center. Pull pin 20 is used to achieve fast and high-precision positioning docking between the fixture and the CNC grinding center, ensuring that the fixture and the machine tool coordinate system remain coaxial.

[0039] like Figure 3 As shown, the toothed positioning block 2 is arranged on the base plate 1 corresponding to the installation position of the blade tenon. The toothed positioning block 2 is provided with a precision toothed positioning surface that matches the blade tenon. The first cylindrical pin 13, the second cylindrical pin 14, the third cylindrical pin 15, the fourth cylindrical pin 16, the fifth cylindrical pin 17, and the sixth cylindrical pin 18 are inserted into the mating positioning holes of the toothed positioning block 2 and the base plate 1 to realize the radial and circumferential positioning and anti-rotation of the toothed positioning block 2. The toothed positioning block 2 is fastened to the base plate 1 by screws and is used for the main positioning of the blade tenon, restricting the six degrees of freedom of the blade and ensuring the core accuracy of blade clamping.

[0040] The end face positioning block 3 is fixedly installed on the base plate 1 at the position corresponding to the exhaust side end face of the blade. The end face positioning block 3 is a planar rigid positioning structure used to axially limit the exhaust side end face of the blade, so that the exhaust side end face of the blade is perpendicular to the central axis of the fixture, ensuring the stability of the axial dimension during processing.

[0041] The wedge positioning block 4 is fixedly installed on the base plate 1 on one side corresponding to the blade wedge surface. The positioning piece 21 is attached and fixed to the working contact surface of the wedge positioning block 4. The positioning piece 21 is a precision thin-plate positioning component. The wedge positioning block 4 and the positioning piece 21 cooperate with each other to assist in the precise positioning of the blade wedge surface, compensate for blade profile errors, and improve the consistency of blade clamping.

[0042] like Figure 4 As shown, the hinge support 6 is fixed to the blade clamping station on the base plate 1 by an internal hex screw. The cross hinge plate 5 is hinged to the hinge support 6 and can rotate around the hinge point. The pressure block 7 is fixedly installed on the front working surface of the cross hinge plate 5. The lower end of the hinge bolt 25 is hinged to the hinge support 6. The upper end of the hinge bolt 25 passes through the cross hinge plate 5 and forms a threaded connection with the shouldered hex nut 24. Tightening the shouldered hex nut 24 can lock and fix the cross hinge plate 5. The pressure block 7 directly contacts the blade surface to achieve non-damaging clamping of the blade.

[0043] like Figure 6 and Figure 2As shown, the support plate 9 is fixedly installed on the base plate 1, the first pressure plate 8 is supported on the upper part of the support plate 9, the support block 11 is fixedly installed on the base plate 1, the second pressure plate 10 is supported on the upper part of the support block 11, and the hexagonal head clamping screw 19 is threaded through the threaded holes of the first pressure plate 8 and the second pressure plate 10 respectively. The end of the hexagonal head clamping screw 19 presses against the blade, and the nylon cap 12 is fitted on the clamping end of the hexagonal head clamping screw 19 to isolate the screw from the blade and prevent the blade surface from being crushed or scratched during the clamping process.

[0044] like Figure 3 As shown, the first cylindrical head adjusting support 29 and the second cylindrical head adjusting support 32 are both installed on the base plate 1 corresponding to the weak areas of the blade body. Both are height-adjustable cylindrical head support structures. The hexagonal thin nut 27 is threaded onto the first cylindrical head adjusting support 29 to lock the height position of the first cylindrical head adjusting support 29. The hexagonal thin nut 30 is threaded onto the second cylindrical head adjusting support 32 to lock the height position of the second cylindrical head adjusting support 32. The tapered end set screw 26 is threaded onto the base plate 1 and presses against the first cylindrical head adjusting support 29 and the second cylindrical head adjusting support 32 to prevent the adjusting supports from loosening or shifting. The first cylindrical head adjusting support 29 and the second cylindrical head adjusting support 32 are used to support the blade body and suppress the deformation and vibration of the blade during the grinding process.

[0045] like Figure 4 and Figure 5 As shown, the first hexagon socket head cap screw 22, the second hexagon socket head cap screw 23, the third hexagon socket head cap screw 28, and the fourth hexagon socket head cap screw 31 respectively rigidly fasten the toothed positioning block 2, the end face positioning block 3, the wedge face positioning block 4, the hinge support 6, the support plate 9, the support block 11, the first cylindrical head adjusting support 29, and the second cylindrical head adjusting support 32 to the base plate 1. The first washer 33 and the second washer 34 are respectively fitted on the outside of each screw and nut to distribute the clamping force, protect the contact surface of the components, and prevent the connection from loosening.

[0046] This fixture uses base plate 1 as the overall positioning reference. It achieves precise clamping of the blade through tenon main positioning, end face axial positioning, and wedge auxiliary positioning. The multi-point non-destructive clamping structure and double-point auxiliary support structure enhance the machining rigidity of the blade. It can effectively suppress deformation and vibration problems during the grinding process of high, narrow and long sealing teeth, and fully meet the five-axis grinding clamping requirements of high, narrow and long sealing teeth of gas turbine single crystal cast high temperature alloy turbine working blades.

[0047] This fixture is used for grinding the high-narrow-long sealing teeth of single-crystal cast high-temperature alloy turbine blades for gas turbines. The specific working process is as follows: Before clamping, the fixture is quickly aligned with the EROWA reference of the CNC grinding center via the pull stud 20 at the bottom of the base plate 1. The fixture coordinate system is then calibrated to be coaxial with the X, Y, Z, A, and B axis coordinate systems of the machine tool, completing the positioning and installation of the fixture on the machine tool. The tenon of the turbine working blade is aligned with the precision tooth positioning surface of the tooth positioning block 2 and placed stably, ensuring that the blade tenon is fully engaged with the tooth positioning block 2. The tooth positioning block 2, positioned by the first cylindrical pin 13, the second cylindrical pin 14, the third cylindrical pin 15, the fourth cylindrical pin 16, the fifth cylindrical pin 17, and the sixth cylindrical pin 18, achieves the main positioning of the blade, restricting all six degrees of freedom of the blade and completing the core positioning of the tenon. The blade is pushed so that the exhaust side end face is tightly against the end face positioning block 3, achieving axial limit of the blade and ensuring that the exhaust side end face is perpendicular to the central axis of the fixture. At the same time, the blade wedge surface is aligned with the positioning piece 21 on the wedge surface positioning block 4, completing the wedge surface auxiliary precision positioning and ensuring that the blade clamping angle and position are uniform and accurate. Adjust the height of the first cylindrical head adjusting support 29 and the second cylindrical head adjusting support 32 so that the tops of the two adjusting supports evenly support the weak areas of the blade body. After adjustment, tighten the hexagonal thin nuts 27 and 30 respectively to lock the support height. Then tighten the cone end set screw 26 to tighten the adjusting support body to prevent the support from loosening or shifting, providing stable auxiliary support for the thin-walled part of the blade and suppressing the grinding deformation of the sealing teeth from the root. After completing the positioning and support adjustment, first rotate the cross hinge pressure plate 5 to press down around the hinge support 6 so that the pressure block 7 is stably attached to the blade surface. Insert the hinge bolt 25 into the corresponding slot of the cross hinge pressure plate 5 and tighten the shouldered hexagonal nut 24 to lock the hinge-type clamping mechanism. Then adjust the position of the first pressure plate 8 and the second pressure plate 10, and tighten the hexagonal head clamping screw 19 so that the screw with the nylon cap 12 at the end evenly clamps the blade crown and blade body, achieving multi-point non-damaging clamping and avoiding scratching the blade surface throughout the process. Use a feeler gauge to check the contact gap between the blade and each positioning and support surface, ensuring the gap is no greater than 0.03mm. Tighten all clamping connections with a torque-limiting wrench to the specified torque to complete the final clamping of the blade. During machining, according to the grinding steps, rotate the A-axis of the machine tool control fixture to 15°, and coordinate with the B-axis rotation and Z-axis feed to machine the intake side blade crown, ensuring the bottom arc dimension of the sealing tooth; then adjust the A-axis to 10° to machine the exhaust side blade crown, precisely controlling the sealing tooth wall thickness and leveling the tooth bottom; finally, adjust the machine tool axis position to complete the top arc machining of the sealing tooth. The fixture maintains a stable positioning and clamping state throughout the process, and the auxiliary support continuously counteracts the grinding force to avoid blade vibration and deformation. A high-pressure cooling system is used to prevent the sealing tooth from burning or recrystallizing.After grinding, first loosen the shouldered hexagonal nut 24, lift the cross hinge pressure plate 5 upward to release the hinge clamping, then loosen the hexagonal head clamping screw 19, remove the clamping force of the first pressure plate 8 and the second pressure plate 10, lower the first cylindrical head adjusting support 29 and the second cylindrical head adjusting support 32 to release the auxiliary support, and finally remove the blade from the toothed positioning block 2, the end face positioning block 3, and the positioning piece 21 to complete the workpiece unloading. After the fixture is reset, the next blade can be clamped and ground.

[0048] Example 1 This embodiment provides a grinding method for the high, narrow, and long sealing teeth of turbine blades made of single-crystal cast high-temperature alloy (DD5) for gas turbines. The overall technical concept of this method is to systematically solve the processing problems such as grinding burns, recrystallization, and loss of dimensional accuracy caused by the poor thermal conductivity of DD5 single-crystal cast high-temperature alloy, thin and easily deformable sealing tooth walls, and difficulty in cooling due to its deep and narrow structure.

[0049] I. Equipment Selection and Cooling Configuration This embodiment selects the MFP50.65.65 CNC grinding center as the machining equipment. This equipment is a five-axis linkage CNC grinding center with five motion axes: X, Y, Z, A, and B. It can achieve continuous trajectory machining of arc dimensions through B-axis rotation and precisely control the wall thickness of the sealing teeth through Z-axis movement, fully meeting the dual precision requirements of the arc surface and wall thickness tolerance of the sealing teeth. Simultaneously, this equipment is equipped with a tool magazine, enabling multi-station integrated machining to be completed in a single setup, reducing positioning errors caused by multiple setups.

[0050] To address the issues of low thermal conductivity and easy heat accumulation in the grinding zone of DD5 single-crystal cast high-temperature alloy, as well as the difficulty of coolant entering the grinding arc zone due to the narrow and deep sealed tooth structure (wall thickness of only 0.5mm at the thinnest point and tooth height of approximately 5mm), this embodiment configures the equipment cooling system as follows: a high-pressure cooling system is adopted, with a coolant supply pressure of not less than 10 atmospheres (approximately 1MPa). This high-pressure cooling jet has a dual function: firstly, it rapidly removes the cutting heat generated in the grinding zone through forced convection, suppressing the rise in grinding temperature at its source and preventing grinding burns and recrystallization layers on the part surface; secondly, it uses a high-momentum jet to flush the working surface of the grinding wheel and the grinding area, promptly removing grinding debris and metal chips embedded in the grinding wheel pores, keeping the grinding wheel chip space unobstructed, and avoiding abnormal increases in grinding force and a sharp rise in grinding heat caused by grinding wheel blockage.

[0051] II. Specialized Fixture Design and Clamping Positioning Method Because the turbine blades processed in this embodiment need to simultaneously ensure the arc dimension and wall thickness of the sealing teeth, and the sealing teeth are tall, narrow, long, and thin-walled structures with poor clamping rigidity and sensitivity to processing deformation, a special fixture with composite positioning and auxiliary support was designed and manufactured. The specific structure of this fixture has been described in detail in the above fixture implementation embodiments; here, only the clamping and usage method in its grinding process will be further explained.

[0052] The positioning scheme of this fixture adopts the following composite positioning system: Main positioning: The blade's tenon teeth are used as the main positioning reference. The main positioning is achieved by a toothed positioning block that precisely matches the tenon tooth profile, which restricts the blade's six spatial degrees of freedom and ensures the core accuracy of blade clamping.

[0053] Axial auxiliary positioning: The exhaust side end face of the blade is used as the axial auxiliary reference. By closely fitting with the end face positioning block, the exhaust side end face is made perpendicular to the central axis of the fixture, ensuring the stability and consistency of the axial dimensions.

[0054] Wedge-assisted positioning: The wedge surface of the blade is used as an auxiliary positioning surface. The wedge-shaped positioning block and precision positioning piece are used for fitting and positioning to compensate for the surface differences of the blade casting blank and improve the consistency and repeatability of batch clamping.

[0055] Auxiliary support: A first cylindrical head adjustment support and a second cylindrical head adjustment support are set in the weak area of ​​the blade. By adjusting the height of the support, it supports the back side of the blade, which enhances the processing rigidity of the blade and effectively suppresses the elastic deflection and vibration of the thin-walled area under the action of grinding force.

[0056] During clamping, the fixture is quickly aligned with the EROWA reference system of the CNC grinding center's worktable via the pull studs on the bottom of the base plate, completing the alignment of the fixture with the machine tool coordinate system. Then, the tenon teeth of the turbine blade are aligned with the toothed locating block and placed smoothly and pressed tightly against it. Next, the exhaust side end face of the blade is placed against the end face locating block, and the wedge surface is aligned with the locating piece on the wedge face locating block. Afterward, the two cylindrical head adjustment supports are adjusted to an appropriate height, ensuring their tips evenly contact the weakest areas of the blade body, and the hexagonal thin nuts and tapered set screws are tightened respectively. After positioning and support are completed, the hinge clamping mechanism and screw tightening mechanism are operated to clamp and fix the blade. After clamping, a feeler gauge is used to check the contact gap between the blade and each locating and support surface, ensuring the gap is no greater than 0.03mm. Then, a torque-limiting wrench is used to tighten all clamping connections to the specified torque, completing the final clamping of the part.

[0057] To accommodate the different process requirements in various grinding areas, the fixture is designed with two pre-set tilt angles of 15° and 10° on the machine tool's A-axis. Specifically, when the A-axis is tilted at 15°, it is used to machine the intake-side vane; when the A-axis is tilted at 10°, it is used to machine the exhaust-side vane. This tilt angle allows the normal direction of the area to be machined in the sealing gear to form an optimized spatial angle with the grinding wheel spindle axis, thereby improving the penetration and coverage of the high-pressure cooling jet in the grinding arc area and enhancing cooling and chip removal effects.

[0058] III. Grinding wheel selection and dressing method This embodiment uses a grinding wheel of model D300×25×76.2, 86A46-3E16-QV36-50S. This type of grinding wheel has the following advantages: the combination of corundum abrasive and ceramic binder achieves sharp cutting with low heat generation; the combination of medium grain size and loose structure provides high porosity and self-sharpening properties, facilitating the removal of grinding debris, and also promoting the penetration and flow of coolant in the pores of the grinding wheel, enhancing heat exchange efficiency; the ceramic binder has good self-sharpening properties, and after the abrasive grains become dull, they can be micro-fractured in a timely manner, continuously exposing new sharp cutting edges.

[0059] Before grinding begins, diamond rollers are used to dress the grinding wheel until a precise profile matches the sealing tooth profile. Throughout the grinding process, the diamond rollers perform synchronous online dressing of the grinding wheel; that is, after each surface is ground, the grinding wheel is immediately dressed by the rollers to restore its sharp cutting state and precise profile. This prevents the grinding force and temperature from increasing due to grinding wheel wear and dulling, thus ensuring the stability of machining accuracy and surface quality.

[0060] IV. Grinding Step Design To effectively control the wall thickness of the sealing teeth and increase the scouring coverage of the machining area by the coolant during grinding, the grinding process of the entire sealing teeth is divided into the following three steps: Step 1: Tilt the A-axis of the fixture at 15° to machine the intake-side blade crown, mainly completing the forming grinding of the bottom arc dimension of the sealing teeth. This posture facilitates the entry of coolant from the intake side and its penetration through the grinding zone.

[0061] Step 2: Adjust the A-axis of the fixture to 10° and machine the exhaust side blade crown. The core objective of this step is to precisely control the wall thickness of the sealing teeth and smoothly connect the exhaust side tooth root with the intake side tooth root machined in Step 1 to ensure the continuity of the tooth root profile.

[0062] Step 3: Adjust the machine tool axis position, machine the top arc dimension of the sealing tooth, and complete the final forming of the sealing tooth profile.

[0063] The three steps are executed sequentially, completing the full-surface grinding of the sealing tooth's inlet side, exhaust side, and top section by section. The division of labor is clear, which not only facilitates the full entry of coolant into each processing area but also makes it easy to accurately control each key dimension.

[0064] V. Blade Layout To reduce the deformation of the sealing teeth during grinding, this embodiment adopts a symmetrical decreasing cycle machining tool arrangement strategy. By controlling the order of allowance distribution and machining cycle, the sealing teeth are subjected to uniform force on both sides and the internal stress is released symmetrically.

[0065] The specific execution sequence of this tool arrangement method is as follows: station 1 roughing → station 2 roughing → station 1 semi-finishing → station 2 semi-finishing → station 1 finishing → station 2 finishing. Among them, "station 1" and "station 2" correspond to the intake and exhaust side machining areas of the sealing teeth, respectively.

[0066] The core of the aforementioned cutting method lies in "cyclical alternation" and "reduced removal": instead of the traditional method of "completely machining one side first, then machining the other side," the roughing, semi-finishing, and finishing stages of the intake and exhaust sides are alternated. The roughing stage alternately removes most of the excess material from both sides; the semi-finishing stage alternately corrects the shape and further releases stress; and the finishing stage alternately completes the final dimensional shaping. This alternating cyclical method ensures that material removal on both sides remains symmetrical and balanced at all times, allowing processing stress to be released synchronously, thereby fundamentally suppressing stress accumulation and thin-wall plastic deformation caused by continuous machining on one side.

[0067] VI. Grinding Parameters For the machining allowance of approximately 1.5mm on the surface of DD5 single-crystal cast high-temperature alloy parts, considering the physical and mechanical properties of the workpiece material, equipment performance, and the characteristics of the selected grinding wheel, the grinding parameters were iteratively optimized through multiple rounds using orthogonal experimental design. The comprehensive evaluation criteria were that the surface after grinding should be free of burns and recrystallization layers, and the dimensional accuracy should be qualified. The final grinding parameters for each machining station are shown in Table 1 below.

[0068] The selection of the above parameters follows these principles: In the roughing stage, material removal efficiency is prioritized, employing a higher linear speed (20 m / s) and a higher feed rate (200-300 mm / min) to quickly remove excess material while ensuring controllable grinding temperature. In the semi-finishing and finishing stages, the linear speed (18 m / s) and feed rate (180-200 mm / min) are simultaneously reduced to decrease the heat input per grinding cycle. A lower feed rate also helps improve surface accuracy and quality. This stepwise reduction in parameters between the roughing and finishing stages results in a gradual decrease in heat load throughout the grinding process, effectively preventing thermal damage caused by improper parameters in the finishing stage.

[0069] VII. Detailed Operating Procedures Based on the above implementation elements, the complete operation flow of the high-narrow-long sealing tooth grinding method for single-crystal cast high-temperature alloy turbine blades of gas turbines in this embodiment is as follows: (1) Fixture installation and calibration: Connect the special fixture to the EROWA reference system of the MFP50.65.65 CNC grinding center worktable through the bottom pull pin and lock it. Calibrate the fixture coordinate system to keep it coaxial with the X, Y, Z, A, B axis coordinate system of the machine tool.

[0070] (2) Part clamping: Align the tenon teeth of the turbine working blade with the toothed positioning block of the fixture, place it smoothly and press it tightly so that the exhaust side end face of the blade abuts against the end face positioning block and the wedge surface abuts against the positioning piece on the wedge surface positioning block, thus completing the main positioning and auxiliary positioning. Adjust the height of the first cylindrical head adjusting support and the second cylindrical head adjusting support so that their tops evenly support the weak area of ​​the blade body and lock it. Operate the clamping assembly to clamp and fix the blade. After clamping, use a feeler gauge to check the contact gap between the blade and each positioning surface and support surface to ensure that the gap is not greater than 0.03mm. Use a torque-limiting wrench to tighten each clamping connection bolt to the specified torque.

[0071] (3) Grinding wheel dressing: Start the grinding wheel and use a diamond roller to dress the profile of the grinding wheel until the required sealing tooth profile is accurately replicated.

[0072] (4) Grinding: According to the above-mentioned process design, tool arrangement and grinding parameter table, the sealing teeth are ground sequentially. In the roughing stage, alternating rough grinding is performed between station 1 and station 2; in the semi-finishing stage, alternating semi-finishing grinding is performed between station 1 and station 2; and in the finishing stage, alternating fine grinding is performed between station 1 and station 2. Throughout the grinding process, the high-pressure cooling system continuously supplies coolant at a pressure of not less than 10 atmospheres, and the diamond roller synchronously dresses the grinding wheel online.

[0073] (5) Disassembly and inspection: After the grinding process is completed, loosen each clamping mechanism in sequence and remove the parts. Perform appearance quality inspection and dimensional accuracy inspection on the finished sealing teeth.

[0074] The DD5 single-crystal cast high-temperature alloy turbine blade with high, narrow, and long sealing teeth obtained by the method described in this embodiment has no grinding burn marks or macroscopic cracks on the machined surface after visual inspection. Metallographic testing shows that no recrystallization layer was found on the machined surface. The arc dimension and wall thickness are within the design tolerance range after measurement by a coordinate measuring machine, which meets the requirements for installation and use of gas turbine blades.

[0075] The method described in this embodiment, through the synergistic application of the functional utilization of a five-axis CNC grinding center, the composite positioning and auxiliary support design of a special fixture, the selection of grinding wheels with high porosity, the deformation control of the symmetrical cyclic tool arrangement, and the step grinding parameters optimized by orthogonal experiments, successfully solves the difficult machining problem of high-narrow-long sealing teeth of DD5 single-crystal cast high-temperature alloy. Under limited machining resources, it achieves stable and high-quality machining of such parts.

[0076] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0077] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or it can be in a centered component. When a component is said to be "connected to" another component, it can be directly connected to the other component or it may also be in a centered component. When a component is said to be "set to" another component, it can be directly set on the other component or it may also be in a centered component.

[0078] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0079] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Those skilled in the art can readily implement the present invention based on the accompanying drawings and the above description. However, any modifications, alterations, or variations made by those skilled in the art without departing from the scope of the present invention, utilizing the disclosed technical content, are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, or variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. A grinding method for high, narrow, and long sealing teeth on turbine working blades, characterized in that, Includes the following steps: The blade is clamped onto the fixture, which uses the blade tenon as the main positioning reference, the exhaust side end face as the axial auxiliary reference, and a damping auxiliary support is provided on the blade body to tilt the surface to be processed of the sealing tooth by a preset angle. A grinding wheel with a ceramic bond having high porosity is selected, and diamond roller online contour dressing is performed after each profile grinding is completed during the grinding process. Symmetrical decreasing cyclic grinding is performed on the intake and exhaust sides of the sealing teeth, and the material is removed by alternating cyclic grinding in the order of roughing one side, roughing the other side, semi-finishing one side, semi-finishing the other side, finishing one side, and finishing the other side. During the cyclic grinding process, a cooling jet with a pressure of not less than 10 atmospheres is applied to the grinding zone through a high-pressure cooling system, and the grinding wheel linear velocity is controlled within the range of 15-25m / s and the feed rate is controlled within the range of 150-350mm / min.

2. The grinding method for the high-narrow-long sealing teeth of turbine working blades according to claim 1, characterized in that, The preset angle of the profile to be processed of the sealing tooth is such that the normal direction of the profile forms a non-zero spatial angle with the axis of the grinding wheel spindle.

3. The grinding method for the high-narrow-long sealing teeth of turbine working blades according to claim 1, characterized in that, For the roughing stage, select a linear speed of 20m / s and a feed rate of 200-300mm / min. For the finishing stage, select a linear speed of 18m / s and a feed rate of 180-200mm / min.

4. The grinding method for the high-narrow-long sealing teeth of turbine working blades according to claim 1, characterized in that, During the cyclic grinding process, the grinding of the sealing teeth is divided into three steps: the first step is to process the bottom arc of the intake side vane, the second step is to process the exhaust side vane to ensure the wall thickness and flatten the bottom, and the third step is to process the top arc of the vane. All three steps follow the symmetrical decreasing cyclic grinding sequence.

5. The grinding method for high-narrow-long sealing teeth of turbine working blades according to claim 1, wherein the online profile dressing of the diamond roller is performed synchronously with the cyclic grinding.

6. The grinding method for a high-narrow-long sealing tooth of a turbine working blade according to claim 1, wherein the cooling jet provided by the high-pressure cooling system is injected into the contact arc area between the grinding wheel and the workpiece along the tangential direction of the grinding wheel circumference.

7. The fixture for grinding the high, narrow, and long sealing teeth of turbine working blades according to claim 1, characterized in that, include: Base (1); Toothed positioning block (2) is fixedly installed on the base (1). The toothed positioning block (2) is provided with a toothed positioning surface that matches the blade tenon teeth, and is used for main positioning of the blade tenon teeth. The end face positioning block (3) is fixedly installed on the base (1) and is used to abut against the exhaust side end face of the blade for axial positioning; The wedge positioning block (4) is fixedly installed on the base (1) and is used to assist in positioning the blade wedge surface; A clamping assembly is installed on the base (1) and is used to clamp and fix the blade to the positioning surfaces of the toothed positioning block (2), the end face positioning block (3) and the wedge face positioning block (4); An auxiliary support assembly is installed on the base (1) to support the weak areas of the blade body in order to suppress deformation and vibration during the grinding process.

8. The fixture for grinding the high, narrow, and long sealing teeth of turbine working blades according to claim 7, characterized in that, The clamping assembly includes a hinge clamping mechanism and a screw tightening mechanism; The hinge clamping mechanism includes a hinge support (6), a cross hinge plate (5), a pressure block (7), a hinge bolt (25), and a shouldered hexagonal nut (24). The hinge support (6) is fixed on the base (1). The cross hinge plate (5) is hinged to the hinge support (6). The pressure block (7) is fixedly installed on the front working surface of the cross hinge plate (5). The lower end of the hinge bolt (25) is hinged to the hinge support (6), and the upper end passes through the cross hinge plate (5) and is threaded to the shouldered hexagonal nut (24). The screw tightening mechanism includes a support plate (9), a first pressure plate (8), a support block (11), a second pressure plate (10), and a hexagonal head clamping screw (19). The support plate (9) and the support block (11) are both fixed on the base (1). The first pressure plate (8) is supported on the support plate (9), and the second pressure plate (10) is supported on the support block (11). The hexagonal head clamping screw (19) is threaded into the threaded holes of the first pressure plate (8) and the second pressure plate (10), and its end is used to tighten the blade.

9. The fixture for grinding the high, narrow, and long sealing teeth of turbine working blades according to claim 7, characterized in that, The auxiliary support assembly includes a first cylindrical head adjustment support (29) and a second cylindrical head adjustment support (32), both of which are height-adjustable cylindrical head support structures, respectively installed on the base (1) corresponding to the weak area of ​​the blade body; each cylindrical head adjustment support is equipped with a hexagonal thin nut for locking its height position, and a tapered end set screw (26) for tightening the adjustment support body to prevent loosening.

10. A fixture for grinding the high, narrow, and long sealing teeth of turbine working blades according to claim 7, characterized in that, The base (1) works in conjunction with the toothed positioning block (2), the end face positioning block (3) and the wedge-shaped positioning block (4) to restrict the six degrees of freedom of the blade and achieve full constraint positioning of the blade.

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