A method for repairing the size of a high-pressure turbine second-stage blade retaining ring

Abstract

The application discloses a high-pressure turbine two-stage rotating blade retaining ring size repairing method, which comprises the following steps: step 1, surface of the two-stage rotating blade is subjected to decontamination treatment; step 2, whether the A surface of the two-stage rotating blade has been subjected to repairing treatment before is detected, if yes, the two-stage rotating blade is subjected to scrap treatment, if not, step 3 is continued; step 3, a repairing layer is sprayed on the A surface of the two-stage rotating blade; step 4, the two-stage rotating blade subjected to the treatment in step 3 is subjected to aging heat treatment; step 5, whether the roundness of the A surface and the flatness of the B surface of the two-stage rotating blade subjected to the treatment in step 4 meet the requirements is detected, if yes, step 6 is carried out, if not, polishing treatment is carried out until the requirements are met; step 6, whether the two-stage rotating blade has cracks is detected, if yes, the two-stage rotating blade is subjected to scrap treatment, if not, step 7 is continued; and step 7, the surface of the two-stage rotating blade is subjected to strengthening treatment.

Description

Technical Field

[0001] This invention belongs to the field of gas turbine maintenance technology, and particularly relates to a method for repairing the size of the retaining ring of the second stage rotor blade of a high-pressure turbine. Background Technology

[0002] During major or intermediate overhauls of gas turbines, the high-pressure turbine second-stage rotor retaining ring needs to be disassembled into individual components. The structural diagram of the high-pressure turbine second-stage rotor retaining ring is shown below. Figure 1 and Figure 2 As shown, dimensional measurements are performed according to the working range requirements, typically on its inner ring A surface (which is...). Figure 2 The measured dimension of one of the annular surfaces (A) is smaller than the standard size range specified in the manual. The function of the high-pressure turbine second-stage rotor retaining ring is to connect the high-pressure turbine second-stage disk and the second-stage rotor retaining ring together. The retaining ring presses against the high-pressure turbine second-stage rotor, fixing it to the high-pressure turbine second-stage disk and preventing axial displacement of the high-pressure turbine second-stage rotor during operation. The second-stage rotor retaining ring and the second-stage disk operate at high speeds, reaching a maximum speed of 9700 r / min. Due to the reduced size of the retaining ring, its fit with the second-stage disk changes from a tight fit to a clearance fit, increasing the stress on the connecting bolts and posing a risk of shear fracture. According to the manual standard, the second-stage rotor retaining ring is scrapped, resulting in an economic loss of 500,000 yuan per unit. Analysis shows that the material of the second-stage rotor retaining ring is nickel-based alloy 718. During gas turbine operation, the high temperature and pressure alter the metallic properties of the material, producing a "shrinkage" effect, leading to a reduction in the overall size of the second-stage rotor retaining ring. Summary of the Invention

[0003] In order to solve the above-mentioned technical problems, the purpose of this invention is to provide a repair method that can increase the size of the retaining ring of the second stage rotor blade of a high-pressure turbine.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows: A method for repairing the dimensions of a high-pressure turbine second-stage rotor retaining ring, comprising the following steps:

[0005] Step 1: Clean the surface of the secondary rotor blades;

[0006] Step 2: Check whether the A surface of the second-stage rotor blade has been repaired before. If so, scrap it. If not, continue to step 3.

[0007] Step 3: Spray a repair layer onto surface A of the secondary rotor blade;

[0008] Step 4: Perform aging heat treatment on the secondary blades after Step 3;

[0009] Step 5: Check whether the roundness of surface A and the flatness of surface B of the secondary blade processed in Step 4 meet the requirements. If they meet the requirements, proceed to Step 6. If they do not meet the requirements, perform grinding until they meet the requirements.

[0010] Step 6: Check if there are cracks in the secondary rotor blade. If there are, scrap it. If not, continue to step 7.

[0011] Step 7: Strengthen the surface of the secondary rotor blade.

[0012] The specific method for cleaning in step 1 of the above technical solution is to use an alkaline solution with a concentration of 1-4wt% for cleaning until there are no obvious stains on the surface of the secondary rotor blades, then rinse with clean water and air dry.

[0013] The alkaline solution mentioned in the above technical solution is one of NaOH solution and KOH solution or a mixture of both.

[0014] The detection method in step 2 and / or step 4 of the above technical solution is to use a fluorescent penetrant testing device for flaw detection.

[0015] The repair layer described in the above technical solution is made of 718 nickel-based alloy.

[0016] The specific method of step 4, aging heat treatment, in the above technical solution is as follows: place the secondary blade face down and horizontally, then keep it at 954±14℃ for 0.5-1.5h for solution heat treatment, and then keep it at 719±14℃ for 7-9h for aging heat treatment.

[0017] The specific method for the aging heat treatment in step 4 of the above technical solution is as follows: place the secondary blade face down and horizontally, then keep it at 954℃ for 1 hour for solution heat treatment, and then keep it at 719℃ for 8 hours for aging heat treatment.

[0018] In step 5 of the above technical solution, the dimensional inspection is as follows: in the free state, the roundness of surface A is not greater than 0.76 mm, and the flatness of surface B is not greater than 1.01 mm.

[0019] In step 7 of the above technical solution, the strengthening treatment involves shot peening the secondary rotor retaining ring.

[0020] The beneficial effects of this embodiment are as follows: This embodiment can repair the second-stage rotor retaining ring, and the repair effect is good. The repaired second-stage rotor retaining ring has been assembled on the #189 gas turbine and is in good condition, meeting the assembly size requirements. Attached Figure Description

[0021] Figure 1An elevation view of the secondary rotor retaining ring;

[0022] Figure 2 This is a cross-sectional view of the secondary rotor retaining ring CC. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 are within the scope of protection of the present invention. Furthermore, it should be understood that the specific embodiments described herein are only for illustration and explanation of the present invention and are not intended to limit the present invention. In the present invention, unless otherwise stated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of the device in actual use or operation, specifically the drawing directions in the accompanying drawings; while "inner" and "outer" refer to the outline of the device.

[0024] This invention provides a method for repairing the dimensions of the retaining ring of a second-stage turbine rotor, characterized by the following steps:

[0025] Step 1: Clean the surface of the secondary rotor retaining ring;

[0026] Step 2: Check whether the A surface of the secondary rotor retaining ring has been repaired before. If so, scrap it. If not, continue to step 3.

[0027] Step 3: Spray a repair layer onto surface A of the secondary rotor retaining ring;

[0028] Step 4: Perform aging heat treatment on the secondary blade retaining ring after Step 3;

[0029] Step 5: Check whether the roundness of surface A and the flatness of surface B of the secondary blade retaining ring after step 4 meet the requirements. If they meet the requirements, proceed to step 6. If they do not meet the requirements, perform grinding until they meet the requirements.

[0030] Step 6: Check if there are cracks in the secondary rotor retaining ring. If there are, scrap it. If not, continue to step 7.

[0031] Step 7: Strengthen the surface of the secondary rotor retaining ring.

[0032] The specific method for cleaning in step 1 is to use an alkaline solution with a concentration of 1-4 wt% for cleaning until there are no obvious stains on the surface of the secondary rotating blade retaining ring, then rinse with clean water and air dry.

[0033] The alkaline solution is one of NaOH solution and KOH solution, or a mixture of both.

[0034] The detection method in step 2 and / or step 4 is to use a fluorescent penetrant testing device for flaw detection.

[0035] The repair layer is made of 718 nickel-based alloy.

[0036] The specific method for the aging heat treatment in step 4 is as follows: place the secondary blade retaining ring with its front side facing down and horizontally, then keep it at 954±14℃ for 0.5-1.5h for solution heat treatment, and then keep it at 719±14℃ for 7-9h for aging heat treatment.

[0037] The specific method for the aging heat treatment in step 4 is as follows: place the secondary blade retaining ring with its front side facing down and horizontally, then keep it at 954℃ for 1 hour for solution heat treatment, and then keep it at 719℃ for 8 hours for aging heat treatment.

[0038] In step 5, the dimensional inspection is as follows: in the free state, the roundness of surface A is no greater than 0.76 mm, and the flatness of surface B is no greater than 1.01 mm.

[0039] The strengthening treatment in step 7 involves shot peening the secondary rotor retaining ring.

[0040] In this embodiment, after heat treatment of the secondary rotor retaining ring, the flatness of its A and B surfaces needs to be measured. The measurement results are as follows: A surface diameter (OD): 579.879 mm, mating dimension (ID) with the secondary disk is 579.868 mm, the two are tightly fitted, and the mating clearance is -0.011 mm; A surface diameter roundness: 0.134 mm, within the required range of 0.76 mm; B surface flatness: 0.074 mm, within the required range of 1.01 mm.

[0041] Heat treatment mechanism

[0042] The microstructure of 718 nickel-based alloy consists of γ phase, γ′ phase, γ” phase, and δ phase, among which γ′ and γ” are strengthening phases, and δ is the equilibrium phase (this is prior art and will not be elaborated here). During the operation of a gas turbine, the operating temperature of the second-stage rotor retaining ring is above 600℃, while the γ′ and γ” phases in the 718 nickel-based alloy precipitate in the range of 600-800℃. As the γ′ and γ” phases continue to precipitate, the proportion of the γ phase continuously decreases. Under stress-free conditions, taking the γ' phase as an example, the lattice constant of the γ' phase is approximately a = 0.35508 nm, while the lattice constant of the γ matrix is ​​approximately a = 0.35678 nm. The lattice constant of the γ matrix is ​​greater than that of the γ' phase, meaning that when there are a certain number of metal atoms, the volume of the γ' phase will be smaller than that of the γ matrix. Therefore, as the γ′ and γ″ phases precipitate continuously, the size of the 718 nickel-based alloy will decrease slightly. When the 718 nickel-based alloy is subjected to solution heat treatment at a temperature of around 960℃, the γ′ phase dissolves above 840℃ and the γ″ phase dissolves above 870℃. As the γ′ and γ″ phases continue to dissolve, the proportion of the γ phase gradually increases, resulting in a slight increase in the size of the 718 nickel-based alloy, thus achieving the goal of restoring the size of the secondary rotor retaining ring.

[0043] The secondary rotor retaining ring must be freely placed on a horizontal plane (i.e., the end closest to surface A is facing upwards). A vacuum heat treatment furnace is used, with the furnace pressure evacuated to 1.0 micrometers of mercury. The heat treatment temperature is strictly implemented according to the solution heat treatment and aging heat treatment regime. Shot peening significantly improves the fatigue resistance of the material, increases the surface strength and hardness, and enhances its resistance to high-temperature oxidation. In this embodiment, the shot peening process in step 7 uses S110 cast steel shot, with an impact angle of less than 35°, a minimum coverage of 125%, and an intensity of 0.006-0.012N.

[0044] Currently, the second-stage rotor retaining ring has been installed on the #189 gas turbine and is in good condition, meeting the assembly dimensional requirements. The self-maintenance cost of this project is 40,000 yuan. Through the development of independent maintenance technology, the second-stage rotor retaining ring has been transformed from "scrapped" to "usable," saving approximately 460,000 yuan in maintenance costs per gas turbine.

[0045] The embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for repairing the dimensions of the retaining ring of a second-stage turbine rotor, characterized in that, Includes the following steps: Step 1: Clean the surface of the secondary rotor retaining ring; Step 2: Check whether the A surface of the secondary rotor retaining ring has been repaired before. If so, scrap it. If not, continue to step 3. Step 3: Spray a repair layer onto surface A of the secondary rotor retaining ring. The repair layer is made of 718 nickel-based alloy. Step 4: Perform aging heat treatment on the secondary blade retaining ring after Step 3; Step 5: Check whether the roundness of surface A and the flatness of surface B of the secondary blade retaining ring after step 4 meet the requirements. If they meet the requirements, proceed to step 6. If they do not meet the requirements, perform grinding until they meet the requirements. Step 6: Check if there are cracks in the secondary rotor retaining ring. If there are, scrap it. If not, continue to step 7. Step 7: Strengthen the surface of the secondary rotor retaining ring; The specific method for the aging heat treatment in step 4 is as follows: using a vacuum heat treatment furnace, the secondary blade retaining ring is placed horizontally with its front side facing down, and then held at 954±14℃ for 0.5-1.5h for solution heat treatment, and then held at 719±14℃ for 7-9h for aging heat treatment.

2. The method for repairing the size of the retaining ring of the second stage blade of a high-pressure turbine according to claim 1, characterized in that, The specific method for cleaning in step 1 is to use an alkaline solution with a concentration of 1-4wt% for cleaning until there are no obvious stains on the surface of the secondary rotating blade retaining ring, then rinse with clean water and air dry.

3. The method for repairing the size of the retaining ring of the second stage blade of a high-pressure turbine according to claim 2, characterized in that, The alkaline solution is one of NaOH solution and KOH solution, or a mixture of both.

4. The method for repairing the size of the retaining ring of the second stage blade of a high-pressure turbine according to claim 1, characterized in that, The detection method in step 2 and / or step 4 is to use a fluorescent penetrant testing device for flaw detection.

5. The method for repairing the size of the retaining ring of the second stage blade of a high-pressure turbine according to claim 1, characterized in that, The specific method for the aging heat treatment in step 4 is as follows: place the secondary blade retaining ring with its front side facing down and horizontally, then keep it at 954℃ for 1 hour for solution heat treatment, and then keep it at 719℃ for 8 hours for aging heat treatment.

6. The method for repairing the size of the retaining ring of the second stage blade of a high-pressure turbine according to claim 1, characterized in that, In step 5, the dimensional inspection is as follows: in the free state, the roundness of surface A is no greater than 0.76 mm, and the flatness of surface B is no greater than 1.01 mm.

7. The method for repairing the size of the retaining ring of the second stage blade of a high-pressure turbine according to claim 1, characterized in that, The strengthening treatment in step 7 involves shot peening the secondary rotor retaining ring.

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