Guide reamer for machining fork pin holes of steam turbine rotor and its application method

Abstract

This invention discloses a guide reamer for machining fork-shaped pin holes on a steam turbine rotor and its application method, belonging to the field of steam turbine machining technology. The reamer includes a cutter body, which is provided with a front guide section, a reaming section, a boring section, a rear guide section, and a neck located at the rear end of the guide section from the machining end to the rear end. Based on the design of integrating the front guide section, the reaming section, the boring section, and the rear guide section, the invention completes the reaming and boring processes in one operation, achieving high machining efficiency. For working conditions where the rotor fork-shaped pin hole is deep, the cutter overhang is long, and there is misalignment between the blade bottom hole and the impeller bottom hole, front and rear guide sections are added before and after the cutter cutting part (reaming and boring) to guide and straighten the cutter, resisting the cutter deviation caused by misalignment and thus solving the problem of the hole diameter becoming larger and elliptical.

Description

Technical Field

[0001] This invention relates to a guide reamer for machining fork-shaped pin holes in a steam turbine rotor and its application method, belonging to the field of steam turbine machining technology. Background Technology

[0002] The fork-shaped pin hole of a steam turbine rotor is a deep hole formed after the assembly of the rotor grooves and the blade roots of multiple layers of plates, with a maximum length-to-diameter ratio of 30. Currently, the process involves drilling pilot holes on both the rotor grooves and blade roots, assembling the blades with the rotor, enlarging the pin hole, and finally reaming for precision machining. However, this process results in significant misalignment of the pilot holes after the blades are assembled with the rotor impeller, uneven machining allowances during enlargement and reaming, insufficient blade root rigidity, and tool deflection during enlargement. Therefore, this misalignment cannot be completely eliminated after enlargement, and significant misalignment still exists during reaming. Furthermore, the fork-shaped pin hole of a steam turbine rotor is a high-precision hole with a large length-to-diameter ratio within a limited space, with a diameter tolerance of 0.018 mm. After the blades and rotor grooves are assembled, other parts of the rotor and blades significantly interfere with the precision machining of this hole. Enlargement and reaming can only be performed using customized specialized equipment, resulting in poor system rigidity under the conditions of a large length-to-diameter ratio and limited space.

[0003] Under the dual pressures of high-precision machining requirements and the actual working conditions of misaligned bottom hole assembly and a weak-rigidity process system, the current turbine rotor fork pin holes consistently suffer from problems of excessively large hole diameters and elliptical deformation after reaming. Furthermore, the pin hole machining process is lengthy, and under a weak-rigidity process system, cutting parameters are low, resulting in low machining efficiency, which is incompatible with the rapidly evolving requirements of new turbines and the retrofitting market. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned problems by providing a guide reamer for machining fork-shaped pin holes in steam turbine rotors and its method of use. This method completes the reaming process of the pin hole in one operation, significantly improving the machining efficiency of the pin hole. At the same time, the front and rear guide structures effectively improve the problem of the hole diameter being too large and becoming elliptical.

[0005] The technical solution adopted in this invention is as follows:

[0006] A guide reamer for machining fork-shaped pin holes of a steam turbine rotor includes a cutter body. The cutter body is provided with a front guide section, a reaming section, a boring section, a rear guide section, and a neck located at the rear end of the guide section from the machining end to the rear end. The cutter body has a right-hand spiral chip removal groove.

[0007] The length of the front guide portion is longer than the distance between the rotor fork-shaped pin hole blade or the two forks of the impeller. The front end of the front guide portion is provided with an end blade for correcting the cylindricity of the hole, and the outer wall of the guide portion is provided with a front guide blade strip.

[0008] The hole-reaming section is provided with a hole-reaming tapered blade, a hole-reaming cutting edge, and a hole-reaming back face for hole-reaming cutting.

[0009] The front end of the hinge hole portion is provided with a hinge hole conical blade and a hinge hole blade strip provided on the outer side wall.

[0010] The outer wall of the rear guide section is provided with a rear guide blade.

[0011] Furthermore, the outer sidewalls of the front guide portion are provided with a front guide blade, and there is a transition arc between the end blade and the front guide blade.

[0012] Furthermore, the connecting section between the front guide portion and the enlarged hole portion is provided with a groove whose diameter is smaller than that of the front guide portion;

[0013] A groove with a diameter smaller than that of the reaming cone is provided between the reaming cone and the reaming section.

[0014] Furthermore, there is a transition arc between the reaming cone and the reaming blade, and there is a transition arc between the hole-expanding cone and the hole-expanding blade.

[0015] Furthermore, the length of the rear guide portion is longer than the width of the blade or impeller fork;

[0016] A tapered ramp and a transition arc are provided between the rear guide portion and the reaming portion, and between the rear guide portion and the neck located at the rear end.

[0017] Furthermore, the front guide portion, the enlarged hole portion, the reaming hole portion, the rear guide portion, and the neck located at the rear end of the guide portion are supported by cemented carbide, and the shank located at the rear end of the cutter body is made of steel.

[0018] Furthermore, the outer diameter of the front guide portion is determined to be 0.15-0.25 mm smaller than the borehole diameter, based on the borehole diameter and the misalignment of the blades and impeller.

[0019] The outer diameter of the enlarged section is 0.15-0.25 mm smaller than the final hole diameter;

[0020] The outer diameter of the hinged hole is matched with the median value of the final hole diameter tolerance;

[0021] The outer diameter of the rear guide portion is 0.04-0.06 mm smaller than the final bore diameter.

[0022] Furthermore, the angle of the expanding cone is 45°–75°;

[0023] The angle of the hinge cone is 20°–60°.

[0024] Furthermore, the helix angle of the right-hand spiral chip removal groove is 20°–30°.

[0025] A method for using a guide reamer for machining fork-shaped pin holes in a steam turbine rotor, characterized by the following steps:

[0026] After assembling the tool body and clamping and positioning the workpiece, the tool body is fed to the specified position according to the positioning. During the feeding process, the tool body is quickly withdrawn to the hole opening after each specified machining depth, and the chips are washed down and the tool body is cooled by the external cooling cutting fluid. Then, the tool body is fed rapidly to the retraction position to continue machining.

[0027] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0028] 1. The present invention provides a guide reamer for machining fork-shaped pin holes of a steam turbine rotor. Based on the design of integrating a front guide section, a reaming section, a boring section, and a rear guide section, the present invention completes the reaming and boring processes in one operation, resulting in high machining efficiency. In response to the working conditions of deep rotor fork-shaped pin holes, long tool overhang, and misalignment between the bottom hole of the blade and the bottom hole of the impeller, front and rear guide sections with guiding and straightening functions are added before and after the tool cutting parts (reaming and boring) to resist tool skew caused by misalignment and thus solve the problem of increased hole diameter and ellipticity.

[0029] 2. The present invention provides a guide reamer for machining fork-shaped pin holes of a steam turbine rotor. The guide reamer with a wide cylindrical blade guides the front and rear to correct the force deviation caused by the misalignment of the blade and the bottom hole of the impeller. The hole expansion part then corrects the assembly misalignment, and finally the reaming part finishes reaming the pin hole, thereby improving the machining accuracy of the hole diameter.

[0030] 3. A method for using a guide reamer for machining fork-shaped pin holes of a steam turbine rotor according to the present invention. The reamer completes the reaming and boring in one machining operation. Although the pecking drilling method with multiple retractions to remove chips consumes a certain amount of time, it can still improve the machining efficiency by 30% compared with the separate machining method of reaming and boring. Attached Figure Description

[0031] The present invention will be described by way of example and with reference to the accompanying drawings, wherein:

[0032] Figure 1 This is a schematic diagram of the structure of the present invention;

[0033] Figure 2 yes Figure 1 Enlarged schematic diagram of the structure within the Chinese frame;

[0034] Figure 3 This is a schematic diagram of the advance and retraction of a multi-functional reamer during drilling.

[0035] The markings in the diagram are: 1 - shank, 2 - neck, 3 - rear guide section, 31 - rear guide cutting edge, 4 - reaming section, 41 - reaming cone cutting edge, 42 - reaming cutting edge, 5 - enlarging section, 51 - enlarging cone cutting edge, 52 - enlarging cutting edge, 53 - enlarging back face, 6 - front guide section, 61 - end cutting edge, 62 - front guide cutting edge. Detailed Implementation

[0036] All features disclosed in this specification, or all steps in all disclosed methods or processes, may be combined in any way, except for mutually exclusive features and / or steps.

[0037] Any feature disclosed in this specification, unless otherwise stated, may be replaced by other equivalent or similar features. That is, unless otherwise stated, each feature is merely one example of a series of equivalent or similar features.

[0038] Example 1

[0039] A guide reamer for machining fork-shaped pin holes in a steam turbine rotor, such as... Figures 1 to 3 As shown, the tool includes a cutting body, which is provided with a front guide portion 6, a reaming portion 5, a boring portion 4, a rear guide portion 3, and a neck 2 located at the rear end of the guide portion from the machining end to the rear end; the cutting body has a right-hand spiral chip removal groove.

[0040] The length of the front guide portion 6 is longer than the distance between the rotor fork-shaped pin hole blade or the two forks of the impeller. The front end of the front guide portion 6 is provided with an end blade 61 for correcting the cylindricity of the hole, and the outer wall of the guide portion is provided with a front guide blade strip 62.

[0041] The hole-reaming section 5 is provided with a hole-reaming tapered blade 51, a hole-reaming cutting edge 52, and a hole-reaming back face 53 for hole-reaming cutting.

[0042] The front end of the hinge hole portion 4 is provided with a hinge hole conical blade 41 and a hinge hole blade strip 42 provided on the outer side wall.

[0043] The rear guide section 3 is provided with a rear guide blade 31 on its outer side wall.

[0044] In this embodiment, in terms of specific structural design, the tool design adopts an integrated design of front guide part 6, hole reaming part 5, hole boring part 4, and rear guide part 3, which completes the reaming and boring processes in one operation, resulting in high processing efficiency. For the working conditions of deep rotor fork pin hole, long tool overhang, and misalignment between the bottom hole of the blade and the bottom hole of the impeller, front and rear guide parts 3 with guiding and straightening functions are added before and after the tool cutting part (reaming and boring) to resist the tool deviation caused by misalignment and thus solve the problem of the hole diameter becoming larger and more elliptical.

[0045] Based on the above specific structural design, and considering the overall tool life and the effect of the overall structure on machining efficiency, as a more specific design, the outer side wall of the front guide part 6 is provided with a front guide blade 62, and there is a transition arc between the end blade 61 and the front guide blade 62.

[0046] Based on the design of the front guide section 6, the frontmost end of the front guide section 6 has a cutting edge 61 that can perform cutting. The cutting edge 61 can remove the misalignment of the blade impeller that is smaller than its diameter and correct the cylindricity of the hole. The outer circle of the front guide section 6 is entirely cylindrical with no back angle, so as to have a larger guiding and support area and better perform the guiding and support function. The small arc transition between the cutting edge 61 and the cylindrical cutting edge enhances the strength of the shoulder connecting the two parts and also prevents the shoulder from chipping during the cutting process.

[0047] As a more specific design, for the further design of the hole-enlarging part 5, the connecting section between the front guide part 6 and the hole-enlarging part 5 is provided with a groove with a diameter smaller than that of the front guide part 6, so as to lengthen the hole-enlarging cone blade 51 so that it can completely cover the cutting area from the diameter of the front guide part 6 to the diameter of the hole-enlarging part 5.

[0048] More specifically, a groove with a diameter smaller than that of the reaming cone and the enlarged hole 5 is provided between the reaming cone and the enlarged hole 5.

[0049] As a more specific design, there is a transition arc between the reaming cone and the reaming blade, and there is a transition arc between the hole-expanding cone 51 and the hole-expanding blade 52.

[0050] Based on the above specific structural design, the length of the rear guide 3 is longer than the width of the blade or impeller fork;

[0051] A tapered slope and a transition arc are provided between the rear guide portion 3 and the reaming portion, and between the rear guide portion 3 and the neck 2 located at the rear end.

[0052] In terms of specific parameter design, the outer diameter of the front guide part 6 is determined to be 0.15-0.25 mm smaller than the borehole diameter, based on the borehole diameter and the misalignment of the blades and impeller.

[0053] The outer diameter of the enlarged section 5 is 0.15-0.25 mm smaller than the final hole diameter;

[0054] The outer diameter of the hinged hole 4 matches the median value of the final hole diameter tolerance.

[0055] The outer diameter of the rear guide part 3 is 0.04-0.06 mm smaller than the final hole diameter.

[0056] With further optimized design, the angle of the expanding cone 51 is 45°–75°;

[0057] The angle of the hinge cone 41 is 20°–60°.

[0058] Based on the above detailed design, the design of each part is further described below, specifically for the reaming section 5. The diameter of the reaming section 5 is 0.2mm smaller than the final hole diameter, serving as a reaming allowance. The reaming section 5 has a reaming tapered cutting edge 51 for reaming cutting. The angle of the reaming tapered cutting edge 51 can be determined according to the actual working conditions, generally 45°–75° to reduce radial force. The connecting section between the front guide section 6 and the reaming section 5 has a groove with a diameter smaller than that of the front guide section 6, to lengthen the reaming tapered cutting edge 51 so that it can completely cover the cutting area from the diameter of the front guide section 6 to the diameter of the reaming section 5. The reaming section 5 has a narrow cylindrical cutting edge, the width of which is determined according to the actual situation, and a flank face with a flank angle size determined according to the actual situation. A rounded transition is used between the reaming tapered cutting edge 51 and the cylindrical cutting edge to enhance the strength of the transition sharp corner and prevent it from being damaged by force during machining.

[0059] Further description of the reaming section 4: The diameter of the reaming section 4 is preferably in the middle of the final hole diameter tolerance, so that the machined hole diameter is within the tolerance range; the front end of the reaming section 4 has a reaming tapered cutting edge 41, and there is still a groove with a diameter smaller than that of the reaming section 5 between the reaming tapered cutting edge 41 and the reaming section 5. The cutting cone angle of the reaming tapered cutting edge 41 is selected as 20°-60° to reduce the radial force of the reaming tapered cutting edge 41. The reaming section 4 has a cylindrical cutting edge and a flank face. To improve the hole wall roughness, the cutting edge can be slightly wider than that of the reaming section 5, and the size of the flank angle is determined according to the actual situation. The reaming tapered cutting edge 41 and the reaming cutting edge 42 still use a rounded transition to prevent damage to the sharp corner. The reaming section 4 may have a small inverted cone to reduce the friction and torque during the reaming process.

[0060] Based on the design of the reaming section 4, the rear guide section 3 is further described. The diameter of the rear guide section 3 is 0.05mm smaller than the final nominal size of the hole, serving a guiding function. The length of the rear guide section 3 is also longer than the width of one fork of the blade or impeller, allowing it to span the distance between the forks during machining and thus providing guidance. The rear guide section 3 also has no clearance angle; its outer diameter is entirely cylindrical to increase the area of ​​the guiding support, thereby better fulfilling its guiding function. The rear guide section 3, along with the reaming section and the neck 2, all transition with small taper slopes and rounded corners to increase the strength of each part, preventing damage during machining and avoiding tool breakage due to snagging on the hole wall during retraction.

[0061] Based on the above structural design and related parameter design, the reamer is straightened by the front and rear guides, and then the misalignment of the blade and impeller bottom hole is corrected by the reaming part 5. Finally, the fork-shaped pin hole is finished by the reaming part, thereby improving the stability of the pin hole diameter and completing the reaming hole in one operation, thus improving the processing efficiency.

[0062] Furthermore, in terms of material design, the front guide part 6, the enlarged hole part 5, the reamed hole part 4, the rear guide part 3, and the neck 2 located at the rear end of the guide part are supported by cemented carbide, and the shank 1 located at the rear end of the blade body is made of steel.

[0063] Specifically, the cutting part is made of cemented carbide, and the shank 1 is made of steel, which are connected by butt welding. The reaming allowance is large, resulting in a large amount of chips. Furthermore, the unmachined holes are small, while the machined holes are large. A left-handed tool cannot handle the chip removal, so a right-handed tool is used, with the chips discharged backward. A helix angle of 20-30° is suitable, ensuring sufficient backward thrust for chip removal while minimizing the chip discharge path. The reamer uses a cemented carbide butt-welded structure. The front guide, reaming section 5, boring section 4, and rear guide section 3 are made of cemented carbide, while the neck 2 and shank 1 are made of tool steel. The butt-welded bevel is located at the neck 2. This structure improves the hole wall roughness and machining efficiency in pin hole machining, and also provides some elasticity to withstand radial deformation caused by inaccurate tool setting and blade root misalignment during machining, preventing tool breakage. This balances both quality and efficiency.

[0064] Example 2

[0065] A method for using a guide reamer for machining fork-shaped pin holes in a steam turbine rotor, characterized by the following steps:

[0066] After assembling the tool body and clamping and positioning the workpiece, the tool body is fed to the specified position according to the positioning. During the feeding process, the tool body is quickly withdrawn to the hole opening after each specified machining depth, and the chips are washed down and the tool body is cooled by the external cooling cutting fluid. Then, it is quickly fed back to the position where it was withdrawn last time to continue machining.

[0067] A reamer completes both reaming and expanding operations in a single pass. It produces a large cutting allowance and a lot of chips. The backward thrust of the right-hand spiral flute alone is insufficient to remove the chips. Therefore, a CNC machine tool is used, employing a drilling-like machining method. After each 15-30mm advance (e.g., 20mm), the tool is rapidly retracted to the hole opening. External cooling fluid flushes away the chips, and the tool is then rapidly fed back to the retracted position to continue machining. This method ensures both machining quality and effective chip removal, while also allowing the cutting fluid to cool the cutting area of ​​the tool in a timely manner, preventing excessively high tool temperatures and extending tool life.

[0068] This front and rear guided reamer completes both reaming and boring processes in one operation. Although multiple push cuts are used for chip removal, which consumes some time, it still improves machining efficiency by 30% compared to separate reaming and boring operations. Furthermore, the use of front and rear carbide guides significantly improves the quality of fork-shaped pin hole machining, including hole diameter accuracy and hole wall roughness.

[0069] This invention is not limited to the specific embodiments described above. The invention extends to any new feature or combination disclosed in this specification, as well as any new method or process step or combination disclosed herein.

Claims

1. A guide reamer for machining a fork pin hole of a steam turbine rotor, characterized by: The tool body comprises a front guide part, a reaming part, a tapping part, a rear guide part and a neck part at the rear end of the guide part, which are arranged in sequence from the machining end to the rear end. The length of the front guide part is longer than the distance between the two prongs of the rotor or the distance between the two prongs of the impeller, the front end of the front guide part is provided with an end edge for correcting the cylindricity of the hole, and the outer side wall of the front guide part is provided with a front guide edge belt. The reaming part is provided with a reaming taper edge, a reaming edge belt and a reaming rear flank. The front end of the tapping part is provided with a tapping taper edge, and the tapping edge belt is arranged on the outer side wall. The outer side wall of the rear guide part is provided with a rear guide edge belt, and the length of the rear guide part is longer than the width of one prong of the blade or the impeller.

2. A guide reamer for machining fork pin holes in a steam turbine rotor as claimed in claim 1, characterized in that: There is an excessive circular arc between the end edge and the front guide edge belt. There is a groove with a smaller diameter than the diameter of the reaming part between the connection section between the front guide part and the reaming part. There is a groove with a smaller diameter than the diameter of the reaming part between the connection section between the front guide part and the reaming part. There is an excessive circular arc between the tapping taper edge and the tapping edge belt, and an excessive circular arc between the reaming taper edge and the reaming edge belt.

3. A guide reamer for machining fork pin holes in a steam turbine rotor as claimed in claim 1, characterized in that: There is a taper slope and an excessive circular arc between the rear guide part and the tapping part, and between the rear guide part and the neck part at the rear end.

4. A guide reamer for machining fork pin holes in a steam turbine rotor as set forth in claim 1, characterized in that: The front guide part, the reaming part, the tapping part, the rear guide part and the neck part at the rear end of the guide part are made of hard alloy, the handle part at the rear end of the tool body is made of steel material, and the welding bevel is located in the neck part. The outer diameter of the front guide part is determined to be 0.15-0.25mm smaller than the diameter of the drill hole and the misalignment amount of the blade and the impeller; The outer diameter of the reaming part is 0.15-0.25mm smaller than the final hole diameter; The outer diameter of the tapping part matches the intermediate value of the size tolerance of the final hole diameter; 5. A guide reamer for machining fork pin holes in a steam turbine rotor as set forth in claim 1, characterized in that: The outer diameter of the rear guide part is 0.04-0.06mm smaller than the final hole diameter. The angle of the reaming taper edge is 45°-75°; The angle of the tapping taper edge is 20°-60°; 6. A method of using a guide reamer for machining a fork pin hole of a steam turbine rotor, the guide reamer being the guide reamer according to any one of claims 1 to 5, characterized in that: The helix angle of the right-handed helical chip removal groove is 20°-30°. The steps include: Assembling the tool body, clamping and positioning the workpiece to be machined, feeding the tool body according to the specified position for machining, during the feeding process, the tool body is quickly withdrawn to the hole after feeding a specified machining depth, and the chips are flushed down and the tool body is cooled through the external cooling cutting fluid, and then the tool body continues to feed to the retreat position for further machining, and the reaming and tapping processes are completed in one machining process.

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