Repair method for casing hanger point bolt hole

Abstract

The application belongs to the technical field of aero-engines, and discloses a machine case lifting point bolt hole repairing method. The repairing method comprises the following steps: welding a welding wire to the inner wall of the bolt hole and filling the worn part; machining the bolt hole and coaxially forming a mounting hole; performing fluorescent penetration inspection on the mounting hole; and mounting a wear-resistant bushing in the mounting hole, wherein the wear-resistant bushing is made of B335 material and has a threaded hole for mounting a lifting point bolt. Through the machine case lifting point bolt hole repairing method, a threaded hole can be formed at the lifting point to reinstall the lifting point bolt, thereby meeting the fixing requirement of the machine case, and the subsequent maintenance frequency can be reduced, thereby reducing the maintenance cost, improving the economic benefit of the gas turbine, and guaranteeing the maintenance cycle and operation safety.

Description

Technical Field

[0001] This invention relates to the field of aero-engine technology, and in particular to a method for repairing the bolt holes of the casing lifting points. Background Technology

[0002] The gas turbine casing is equipped with lifting points and bolt holes for installing lifting bolts. These bolts provide crucial support for the gas turbine, ensuring its stable fixation. However, during operation, vibrations cause the bolts to rub and collide with the bolt holes and the front frame, leading to wear on the inner walls of the bolt holes over time. This wear not only affects the turbine's proper fixation but also exacerbates vibrations during operation, creating a vicious cycle and further accelerating the wear.

[0003] To address this wear problem, existing technologies typically employ machining to remove the worn portion and re-thread it for repair. However, this repair method reduces the wall thickness at the lifting point, thereby weakening its load-bearing capacity and the structural strength of the casing, posing a potential threat to the stability and safety of the gas turbine.

[0004] Based on the above, there is an urgent need for a method to repair the bolt holes of the casing lifting points in order to solve the aforementioned technical problems. Summary of the Invention

[0005] The purpose of this invention is to provide a method for repairing bolt holes at the lifting points of a casing, which can repair the bolt holes at the lifting points without affecting the load-bearing capacity of the lifting points or the structural strength of the casing.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] Repair methods for the casing lifting point bolt holes include:

[0008] S1. Weld the welding wire to the inner wall of the bolt hole and fill the worn area;

[0009] S2. The bolt holes are machined to form mounting holes coaxially;

[0010] S3. Perform fluorescence penetration testing on the mounting holes;

[0011] S4. Install a wear-resistant bushing in the mounting hole. The wear-resistant bushing is made of B335 material and has a threaded hole for installing a lifting bolt.

[0012] Preferably, before step S1, the method further includes:

[0013] S01. Perform the first heat treatment on the casing to eliminate residual stress.

[0014] Preferably, step S2 further includes removing surface weld scars from the casing.

[0015] Preferably, the base material of the casing is 17-4PH, the welding wire is AMS5825, and the wear area is welded using argon arc welding.

[0016] Preferably, between step S1 and step S2, the following is also included:

[0017] S11. Perform a second heat treatment on the casing to eliminate residual stress.

[0018] Preferably, both the first heat treatment and the second heat treatment include stress-relief annealing of the casing at 635 degrees Celsius for 4 hours.

[0019] Preferably, in step S4, the wear-resistant bushing is subjected to a freeze treatment before installation.

[0020] Preferably, there is an interference fit of 0.04 mm between the wear-resistant bushing and the mounting hole.

[0021] Preferably, step S4 further includes:

[0022] The inner wall of the wear-resistant bushing is machined to meet the connection requirements of the lifting point bolts.

[0023] Preferably, after step S4, the method further includes:

[0024] S5. Verify whether the lifting bolt can be passed through both threaded holes or one threaded hole and one bolt hole simultaneously by manual means. If not, the inner wall of the wear-resistant bushing should be re-machined.

[0025] The beneficial effects of this invention are that, through the method of repairing the casing lifting point bolt holes, not only can threaded holes be formed at the lifting points to reinstall the lifting point bolts, thereby meeting the fixing requirements of the casing, but it can also reduce the frequency of subsequent maintenance, thereby reducing maintenance costs, improving the economic efficiency of the gas turbine, and ensuring maintenance cycle and operational safety. Attached Figure Description

[0026] Figure 1 This is a flowchart illustrating the method for repairing the bolt holes of the casing lifting points provided by the present invention;

[0027] Figure 2 This is a schematic diagram of the installation of the casing and wear-resistant bushing in this invention.

[0028] In the picture:

[0029] 1. Casing; 2. Wear-resistant bushing. Detailed Implementation

[0030] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0031] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0032] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0033] In the description of this embodiment, the terms "upper," "lower," "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0034] The casing 1 is a crucial component of the gas turbine (referred to as the gas turbine in this invention), also known as the CVC (Compressor Vane Carrier), primarily located in the outer shell of the gas turbine's compressor section. The casing 1 is the main load-bearing component of the gas turbine, bearing gas pressure and temperature loads to ensure structural stability during high-speed operation. Internally, the casing 1 connects core components such as the compressor and combustion chamber, while externally it connects auxiliary systems such as exhaust pipes, cooling pipes, and oil lines, forming the "skeleton" of the entire gas turbine system. The casing 1 provides a safe, sealed space for the core components inside the gas turbine, protecting them from external environmental interference while ensuring smooth airflow within the turbine. Numerous functional components are attached to the inner and outer surfaces of the casing 1, such as external exhaust pipes, cooling pipes, and oil lines, as well as internal combustion chambers and compressors. These components work together to complete the processes of gas compression, combustion, and exhaust.

[0035] Because casing 1 needs to withstand enormous pressure and temperature loads during operation, its manufacturing precision requirements are extremely high to ensure the stable and efficient operation of the gas turbine. The main manufacturing processes for casing 1 include precision forging, which yields casing 1 components with high strength and good plasticity through forging. For certain special parts, such as the combustion chamber casing 1, due to their high operating temperature and complex stress distribution, an integral precision casting process is used to ensure good temperature resistance and strength.

[0036] In summary, the casing 1 is an indispensable component of the gas turbine and accounts for a significant proportion of its structural cost. When wear occurs in the lifting point bolt holes (hereinafter referred to as bolt holes), replacing the entire casing 1 would incur substantial maintenance costs and result in waste. Therefore, this invention provides a method for repairing the casing lifting point bolt holes, enabling the treatment of worn bolt holes at a lower cost.

[0037] The following is based on the appendix Figure 1 Appendix Figure 2 This invention introduces a method for repairing the bolt holes at the lifting points of the casing. Specifically, the method includes:

[0038] S1. Weld the welding wire to the inner wall of the bolt hole and fill the worn area.

[0039] Specifically, in step S1, the operator can select the material of the welding wire according to the material of the casing 1 to form a filling structure. For example, in this embodiment, the base material of the casing 1 is 17-4PH, the welding wire is AMS5825, and argon arc welding is used to deposit welds on the worn parts to fill the gap.

[0040] It should be noted that in this embodiment, the welding wire only needs to be able to fill the worn area, and the shape of the structure formed by the filling is not specifically limited in this invention. For example, the inner wall of the bolt hole has a worn area, which includes both wear of the thread structure and recessed structures such as grooves and holes formed on the hole wall. In this case, as long as the welding wire can fill the grooves, holes, and other structures to achieve the effect of eliminating the grooves, holes, and other recessed structures, it falls within the scope of filling the worn area required by this invention.

[0041] S2. Machining the bolt holes and forming mounting holes coaxially.

[0042] Specifically, in step S2, forming a coaxial mounting hole means that the axis of the mounting hole and the axis of the original bolt hole are set in the same direction, so as to avoid deviation in the position of the lifting point after the repair, so that the casing 1 can still be installed in the original fixed position by the lifting point bolt.

[0043] S3. Perform fluorescent penetrant testing on the repaired area.

[0044] Specifically, fluorescent penetrant testing utilizes the capillary action and penetration principle of liquids for detection. During testing, a penetrant containing a fluorescent dye is applied to the surface of the workpiece being tested. Due to capillary action, the penetrant penetrates into open defects on the workpiece surface, such as cracks and pores. After the penetrant has fully penetrated, excess penetrant is washed away from the workpiece surface, and then a developer is applied. The developer adsorbs the penetrant in the defects and emits fluorescence under ultraviolet light. By observing the fluorescence display on the workpiece surface, the location, shape, and size of defects such as cracks and pores can be determined.

[0045] S4. Install the wear-resistant bushing 2 in the mounting hole. The wear-resistant bushing 2 is made of B335 material and has a threaded hole for installing the lifting point bolt.

[0046] Specifically, B335 material has superior toughness and ductility, which prevents the metal material inside the bolt hole from cracking when subjected to compression and impact. During subsequent operation of the gas turbine, it reduces wear and has a longer service life.

[0047] By using this method of repairing the casing lifting point bolt holes, not only can threaded holes be formed at the lifting points to reinstall the lifting point bolts, thereby meeting the fixing requirements of casing 1, but it can also reduce the frequency of subsequent maintenance, thereby reducing maintenance costs, improving the economic efficiency of the gas turbine, and ensuring maintenance cycle and operational safety.

[0048] Preferably, before step S1, the method further includes:

[0049] S01. Perform the first heat treatment on the casing 1 to eliminate residual stress.

[0050] During the long-term use of the gas turbine, the casing 1 will generate residual stress due to heat. During welding, this residual stress will cause varying degrees of deformation between the molten metal formed by the welding wire and the casing 1, resulting in poor bond strength and a tendency to crack, among other safety hazards. Therefore, heat treatment can eliminate residual stress, which helps improve the strength and stability of the welded connection and enhances the quality of the weld. For example, in this embodiment, the casing 1 is subjected to stress-relief annealing at 635 degrees Celsius for 4 hours to eliminate residual stress.

[0051] Furthermore, between steps S1 and S2, i.e. before machining the bolt hole, the process also includes:

[0052] S11. Perform a second heat treatment on the casing 1 to eliminate residual stress.

[0053] Specifically, the second heat treatment is mainly used to eliminate residual stress caused by welding. Optionally, the second heat treatment also involves stress-relief annealing of the casing 1 at 635 degrees Celsius for 4 hours to eliminate residual stress.

[0054] Optionally, step S2 further includes removing surface weld scars from the casing 1. Specifically, these surface weld scars refer to weld scars formed on the outer surface of the casing 1 during the welding process (distinct from the inner wall of the bolt holes). These surface weld scars can affect the installation of the wear-resistant bushing 2, and therefore need to be removed.

[0055] Furthermore, in this embodiment, in step S4, there is an interference fit of 0.04mm between the wear-resistant bushing 2 and the mounting hole, so that the wear-resistant bushing 2 can be interference fitted into the mounting hole, making it fixed and stable, preventing the wear-resistant bushing 2 from moving around, and improving the installation stability of the entire gas turbine.

[0056] Specifically, in step S4, the wear-resistant bushing 2 is installed into the mounting hole using a cryogenic assembly method. That is, before installing the wear-resistant bushing 2, it is cryogenically treated to reduce its outer diameter to be smaller than the mounting hole, thus facilitating its insertion into the mounting hole. Then, as the temperature recovers, the outer diameter of the wear-resistant bushing 2 gradually increases, thereby abutting against the inner diameter of the mounting hole and securing the wear-resistant bushing 2 to the housing 1.

[0057] Cryogenic assembly reduces interference fits and assembly pressure, thereby minimizing the risk of damage to bushings or mounting holes due to excessive assembly force. Cryogenic assembly can achieve high-precision interference fits without damaging components, improving assembly accuracy and meeting the stringent requirements of gas turbines for component fit precision.

[0058] Optionally, step S4 further includes:

[0059] S5. The inner wall of the wear-resistant bushing 2 is machined to meet the connection requirements of the lifting point bolts.

[0060] In some embodiments, after cryogenic assembly of the wear-resistant bushing 2, internal deformation of the wear-resistant bushing 2 may occur, which can be corrected by machining. In other embodiments, the wear-resistant bushing 2 does not yet have internal threads before cryogenic assembly, and tapping is performed after cryogenic assembly to form the required internal threads. Therefore, both correcting the inner wall surface through machining and forming the internal threads through machining fall within the scope of protection of this invention.

[0061] It should be noted that, as Figure 2 As shown, a lifting point on the casing 1 is connected to a lifting bolt via two bolt holes. This method can be used to repair only one bolt hole or to repair both bolt holes of the lifting point simultaneously.

[0062] Optionally, after step S4, verify whether the lifting bolt can be passed through both threaded holes or one threaded hole and one bolt hole simultaneously by manual means. If not, the inner wall of the wear-resistant bushing 2 is re-machined.

[0063] Specifically, if the lifting bolt can be manually passed through two threaded holes or one threaded hole and one bolt hole (i.e., the original bolt hole on the housing 1) simultaneously, it indicates that the two wear-resistant bushings 2 can connect the lifting bolt with good precision and coaxiality, or that the wear-resistant bushing 2 and the original bolt hole can connect the lifting bolt with good precision and coaxiality, while maintaining uniform force. Conversely, if these conditions are not met, the inner wall of the wear-resistant bushing 2 needs to be machined for correction.

[0064] In the description of this specification, references to terms such as "some embodiments," "other embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0065] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art will be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for repairing bolt holes at the lifting points of the casing, characterized in that, include: S1. Weld the welding wire to the inner wall of the bolt hole and fill the worn area; S2. The bolt holes are machined to form mounting holes coaxially; S3. Perform fluorescence penetration testing on the mounting holes; S4. Install a wear-resistant bushing (2) in the mounting hole. The wear-resistant bushing (2) is made of B335 material and has a threaded hole for installing a lifting bolt.

2. The method for repairing the bolt holes of the casing lifting points according to claim 1, characterized in that, Before step S1, the following is also included: S01. Perform the first heat treatment on the casing (1) to eliminate residual stress.

3. The method for repairing the bolt holes of the casing lifting points according to claim 1, characterized in that, Step S2 also includes removing surface weld scars from the casing (1).

4. The method for repairing the bolt holes of the casing lifting points according to claim 1, characterized in that, The base material of the casing (1) is 17-4PH, the welding wire is AMS5825, and argon arc welding is used to overlay the worn parts.

5. The method for repairing the bolt holes of the casing lifting points according to claim 2, characterized in that, Between step S1 and step S2, the following is also included: S11. The casing (1) is subjected to a second heat treatment to eliminate residual stress.

6. The method for repairing the bolt holes of the casing lifting points according to claim 5, characterized in that, Both the first and second heat treatments consist of stress-relief annealing of the casing (1) at 635 degrees Celsius for 4 hours.

7. The method for repairing the bolt holes of the casing lifting points according to claim 1, characterized in that, In step S4, the wear-resistant bushing (2) is subjected to a freeze treatment before installation.

8. The method for repairing the bolt holes of the casing lifting points according to claim 1, characterized in that, There is an interference fit of 0.04 mm between the wear-resistant bushing (2) and the mounting hole.

9. The method for repairing the bolt holes of the casing lifting points according to claim 1, characterized in that, Step S4 also includes: The inner wall of the wear-resistant bushing (2) is machined to meet the connection requirements of the lifting point bolts.

10. The method for repairing the bolt holes of the casing lifting points according to claim 1, characterized in that, After step S4, the following is also included: S5. Verify whether the lifting bolt can be passed through both threaded holes or one threaded hole and one bolt hole simultaneously by manual means. If not, the inner wall of the wear-resistant bushing (2) should be re-machined.

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