Rotor repair method

Abstract

To maintain a shape and performance of a rotor stably even after repairing.SOLUTION: A rotor repair method is a repair method of a rotor including: a rotor body which extends in an axial direction, centered on an axis; and a plurality of impellers arranged in the axial direction and fixed to the rotor body. The rotor repair method includes: a step in which welding is performed to a repair area of the rotor body and a damaged portion is filled with a welding part; a step in which heat treatment is performed only to the repair area in the rotor after the welding is performed; and a step in which a part of the welding part is scraped to form a processing surface connected smoothly with an outer surface after the heat treatment is performed.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a method for repairing a rotor. [Background technology]

[0002] Generally, a centrifugal compressor includes a rotor having multiple impellers and a casing that covers the impellers from the outside to form a flow path between the impellers. In a centrifugal compressor, a fluid supplied from the outside through a flow path formed in the casing is compressed by the rotation of the impeller. When the rotor of such a compressor is damaged, it may be possible to repair it without making a new rotor.

[0003] For example, Patent Document 1 describes a repair method in which a thermal spray coating is formed on the damaged portion to be repaired. Specifically, in the repair method described in Patent Document 1, first, the damaged portion of the rotor that occurs at the portion supported by the bearing is removed and shaped by machining or the like. Then, the removed and shaped surface is roughened by blasting, and a coating is formed by high-velocity flame spraying. The formed coating is processed, finished, and inspected to obtain a repaired rotor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2004-256903 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above-mentioned rotor repair, if the welded portion is not heat treated, the strength of the welded portion may be insufficient or the hardness may be excessive, compared to the other non-welded portions. As a result, the rotor after repair may not satisfy the required performance. On the other hand, if heat treatment is performed on a large part such as a rotor, the dimensions of the rotor may change before and after the repair, making it difficult to obtain a rotor with the same shape as before the repair. Thus, when repairing a rotor, it is required to maintain the shape and performance of the rotor before and after the repair.

[0006] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a rotor repair method that can stably maintain the shape and performance of the rotor after repair. [Means for solving the problem]

[0007] In order to solve the above problems, the rotor repair method disclosed herein is a method for repairing a rotor having a rotor body extending in an axial direction centered on an axis, and a plurality of impellers aligned in the axial direction and fixed to the rotor body, and includes the steps of: welding a repair area of ​​the rotor body and filling a damaged area formed so as to be recessed from the outer surface of the rotor body with a weld; after performing the welding, performing a heat treatment on only the repair area of ​​the rotor; and, after performing the heat treatment, removing a portion of the weld to form a machined surface that is smoothly connected to the outer surface. Effect of the Invention

[0008] According to the rotor repair method of the present disclosure, the shape and performance of the repaired rotor can be stably maintained. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic diagram showing a rotor to be repaired according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a flow chart showing a rotor repair method according to the present embodiment. [Diagram 3] 10 is an enlarged view of a main part of a rotor body for explaining a step of checking a damaged portion according to the present embodiment. FIG. [Figure 4] 5 is an enlarged view of a main part of the rotor body illustrating a step of machining a damaged portion according to the present embodiment. FIG. [Diagram 5] 4 is an enlarged view of a main portion of the rotor body illustrating a step of welding a repair area according to the embodiment. FIG. [Figure 6] 10 is an enlarged view of a main portion of the rotor body, illustrating how a heater is attached in a step of performing partial heat treatment according to the embodiment; FIG. [Figure 7] 10 is an enlarged view of a main portion of the rotor body illustrating how a heat-insulating material is attached in the step of performing partial heat treatment according to the present embodiment. FIG. [Figure 8] 5 is an enlarged view of a main part of the rotor body for explaining a step of forming a machined surface according to the present embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment for carrying out the rotor repair method S1 according to the present disclosure will be described with reference to the accompanying drawings. However, the present disclosure is not limited to only this embodiment.

[0011] The rotor repair method S1 is a method for repairing a shaft end region 100 including an end portion of a rotor 1. The rotor 1 to be repaired is a rotating component of a rotary machine such as a compressor or a steam turbine. The rotor 1 in this embodiment is a rotor 1 of a multi-stage centrifugal compressor.

[0012] (Rotor configuration) 1, the rotor 1 is a component that is rotatable about an axis O within a casing (not shown). The rotor 1 includes a rotor body 10 and an impeller 20. The rotor body 10 extends in an axial direction Da with the axis O as its center.

[0013] In the following description, the direction in which the axis O extends is referred to as the axial direction Da. When the rotor 1 is installed in a rotary machine, the axis O extends horizontally. The direction perpendicular to the axial direction Da is referred to as the radial direction Dr. In other words, the radial direction Dr of the rotor 1 based on the axis O is simply referred to as the radial direction Dr.

[0014] The impellers 20 are arranged in a line at intervals in the axial direction Da. Each impeller 20 is fixed to the rotor body 10. Each impeller 20 is rotatable around the axis O integrally with the rotor body 10. In this embodiment, for example, six impellers 20 are provided in total. These impellers 20 are arranged in the center of the rotor body 10 in the axial direction Da between a side closer to the first end 11 of the rotor body 10 (first end side Da1, one side) and a side closer to the second end 12 of the rotor body 10 (second end side Da2, the other side).

[0015] The rotor body 10 has an axial end region 100 including an end of the rotor body 10 in the axial direction Da. The axial end region 100 is a region of a certain range from the end in the axial direction Da. The rotor body 10 of this embodiment has a first axial end region 110 including a first end 11 which is one end in the axial direction Da, and a second axial end region 120 including a second end 12 which is the other end in the axial direction Da. The first axial end region 110 and the second axial end region 120 are formed apart from each other in the axial direction Da with a central portion therebetween. The first axial end region 110 and the second axial end region 120 are formed at positions not overlapping with the impeller 20 in the axial direction Da.

[0016] Furthermore, the rotor body 10 can be rotatably supported on the casing by the bearing 8. The rotor body 10 has a bearing region 130 supported by the bearing 8. The bearing 8 supporting the rotor body 10 has a thrust bearing 81 that restricts displacement of the rotor body 10 in the thrust direction, and a pair of journal bearings 82 that rotatably support the rotor body 10. In other words, the rotor body 10 has a thrust supported region 140 supported by the thrust bearing 81, and a journal supported region 150 supported by the journal bearing 82.

[0017] The thrust supported region 140 is formed as a part of the second shaft end region 120. The thrust supported region 140 is formed at a position away from the second end 12 in the axial direction Da. The journal supported region 150 has a first journal supported region 151 and a second journal supported region 152, which are separated in the axial direction Da. The first journal supported region 151 is formed as a part of the first shaft end region 110. The first journal supported region 151 is formed at a position away from the first end 11 in the axial direction Da. The second journal supported region 152 is formed as a part of the second shaft end region 120. The second journal supported region 152 is formed at a position away from the second end 12 and the thrust supported region 140 in the axial direction Da.

[0018] Further, a coupling member 9 can be attached to the first end 11 of the rotor body 10. The coupling member 9 can be attached and detached not only to the first end 11 of the rotor body 10 but also to another rotating machine (not shown) arranged outside the casing. The rotor body 10 has a coupling fixed region 160 to which the coupling member 9 can be fixed. The coupling fixed region 160 is formed as a part of the first shaft end region 110. The coupling fixed region 160 is formed at a position away from the first end 11 in the axial direction Da. The coupling fixed region 160 is formed at a position between the first journal supported region 151 and the first end 11 in the axial direction Da.

[0019] (Rotor repair method) The rotor repair method S1 will be described with reference to Fig. 2. The rotor repair method S1 of this embodiment is performed on the rotor 1 removed from the casing. The rotor repair method S1 repairs a damaged area D including scratches and the like formed on the outer surface F of the rotor 1 in the shaft end region 100. The rotor repair method S1 includes a damaged area confirmation step S2, a damaged area processing step S3, a repair area welding step S4, a partial heat treatment step S5, and a processed surface formation step S6.

[0020] (Damage confirmation step) In the damaged area confirmation step S2, a damaged area D formed in the shaft end region 100 of the rotor 1 is confirmed. For example, an operator visually checks the rotor 1 and confirms whether the damaged area D is formed in the shaft end region 100. In this embodiment, as shown in FIG. 3, a case where the damaged area D exists in the coupling fixed area 160 of the first shaft end region 110 will be described as an example. The damaged area in the coupling fixed area 160 is formed by attaching and detaching the coupling member 9 to the rotor body 10 because the coupling member 9 is fixed to the rotor body 10 by hydraulic fitting, shrink fitting, or the like. The damaged area D is formed so as to be recessed from the outer surface F of the rotor body 10. In addition, the repair area A to be repaired is formed in the shaft end region 100. The repair area A to be repaired is an area in the rotor body 10 that includes the damaged area D. That is, in this embodiment, a predetermined range including the area in which the damaged area D exists in the coupling fixed area 160 is set as the repair area A.

[0021] (Damaged area processing step) The damaged area processing step S3 is performed after the damaged area confirmation step S2, as shown in FIG. 2. As shown in FIG. 4, in the damaged area processing step S3, the damaged area D is cut away to form a repair area A as a recess C recessed from the outer surface F. The recess C is formed over the entire circumference of the rotor body 10. The recess C is formed so as to completely cut away the damaged area D from the rotor body 10. The recess C is formed over a range larger than the position where the damaged area D is formed. In other words, when the recess C is formed, the damaged area D is not present in the rotor body 10. In this embodiment, the recess C is formed in the coupling fixed area 160.

[0022] (Repair area welding step) In the repair area welding step S4, welding is performed on the repair area A. As shown in FIG. 2, the repair area welding step S4 in this embodiment is performed after the damaged area processing step S3. In the repair area welding step S4, as shown in FIG. 5, welding is performed on the repair area A of the shaft end region 100, and the damaged area D is filled with a welded portion M. In this embodiment, welding is performed so that the welded portion M fills the recessed portion C formed in the coupling fixed region 160. That is, the welded portion M is formed over the entire circumference of the rotor body 10. The welded portion M is formed by building up the entire circumference of the recessed portion C by laser welding. The welded portion M is formed to a thickness that protrudes from the outer surface F in the radial direction Dr.

[0023] (Partial heat treatment step) The partial heat treatment step S5 is performed after the repair area welding step S4, as shown in FIG. 2. In the partial heat treatment step S5, after welding, only the shaft end region 100 of the rotor 1 is heat treated. Specifically, as shown in FIG. 6, only the first shaft end region 110 is heat treated. More specifically, in this embodiment, only the coupling fixed region 160, which is the repair area A, is treated. The heat treatment is performed by annealing. That is, the coupling fixed region 160 is gradually heated to a specified temperature at a constant speed, kept warm for a predetermined time, and then gradually cooled at a constant speed. In this embodiment, a heater H made of a nichrome wire or the like is wound around only the coupling fixed region 160, which is the region to be heat treated, without any gaps. Then, as shown in FIG. 7, a heat insulating material T is wound around the coupling fixed region 160 so as to cover the heater H. In this manner, with the heater H and the heat insulating material T attached to the coupling fixed region 160 including the welded portion M, only the coupling fixed region 160 is annealed over the entire circumference with respect to the rotor 1. At this time, the annealing conditions during the heat treatment are preferably set so that the coupling fixed region 160 after the heat treatment satisfies the Charpy value required for a low-temperature material.

[0024] The partial heat treatment step S5 is preferably performed after the influence of heat due to welding has been completely removed from the rotor 1. The partial heat treatment step S5 is preferably performed with the rotor 1 standing so that the axis O extends in the vertical direction.

[0025] (machining surface formation step) The machined surface forming step S6 is performed after the partial heat treatment step S5, as shown in Fig. 2. In the machined surface forming step S6, after the heat treatment, a part of the welded portion M is cut to form the machined surface GF, as shown in Fig. 8. The machined surface GF is formed by polishing the welded portion M. The machined surface forming step S6 is not performed before the partial heat treatment step S5.

[0026] The machined surface GF is a surface that is smoothly connected to the outer surface F. The machined surface GF is formed in a position in the axial direction Da that overlaps the position where the welded portion M is formed. The machined surface GF is a smooth surface that is connected to the outer surface F in a position in the axial direction Da where the recess C is not formed. The machined surface GF is formed over the entire circumference of the rotor body 10 at a constant distance from the axis O in the radial direction Dr.

[0027] (Action and effect) In the rotor repair method S1 having the above configuration, the damaged portion D is welded to form a welded portion M. As a result, the damaged portion D is filled with the welded portion M and repaired. However, by only performing welding, the strength of the heat-affected portion, which is the welded portion M and its periphery, may be insufficient compared to the required strength, or the hardness of the heat-affected portion may exceed the required hardness. In response to this, by performing heat treatment, the strength of the heat-affected portion can be increased and the hardness can be reduced to meet the required value. At that time, the heat treatment is performed only on the first shaft end region 110 including the repair area A where the welded portion M is formed, without performing heat treatment on the entire rotor 1 or the entire rotor body 10. Since the entire rotor 1 or the entire rotor body 10 is not heated, the effects of thermal expansion, thermal contraction, distortion, and the like due to the heat treatment can be limited to the vicinity of the repair area A. In other words, the range in which changes in dimensions and surface roughness occur due to the effects of heat treatment can be limited to the vicinity of the repair area A. Furthermore, after a partial heat treatment is performed only on the first shaft end region 110 including the repair area A, a part of the welded portion M is cut off to form the machined surface GF. Therefore, any changes in dimensions and surface roughness that occur only in the first shaft end region 110 can be corrected by cutting off. Also, since no heat treatment is performed after the machined surface GF is formed, changes in dimensions and surface roughness are suppressed from occurring on the machined surface GF once it has been formed. As a result, a rotor 1 of the same quality and shape as before the repair can be stably obtained. Therefore, the shape and performance of the rotor 1 after the repair can be stably maintained.

[0028] Particularly in this embodiment, the heat treatment is applied only to the first shaft end region 110. This makes it possible to limit the effects of thermal expansion, thermal contraction, distortion, and the like caused by the heat treatment to the first shaft end region 110. In other words, the range in which changes in dimensions and surface roughness occur due to the effects of the heat treatment can be limited to only the first shaft end region 110.

[0029] Furthermore, the machined surface GF is formed so as to be at a constant distance in the radial direction Dr from the axis O over the entire circumference of the rotor body 10. Therefore, the repair area A where the welded portion M is formed (the area where the damaged portion D originally existed) can be machined to match the original shape over the entire circumference with high precision. Therefore, a rotor 1 having the same shape as before the repair can be more reliably obtained.

[0030] Moreover, the welded portion M is formed by laser welding. In particular, laser welding is performed on the entire circumference of the rotor body 10. Therefore, the thermal effect of welding on the rotor body 10 is greater than when only a portion of the rotor body 10 is welded. Furthermore, in a welding method with a large amount of heat input, such as TIG welding, the thermal effect on the rotor body 10 is greater. However, by employing laser welding, the amount of heat input during welding can be reduced, and the thermal effect on the rotor body 10 can be reduced. This makes it possible to reduce deformation of the rotor body 10 due to welding.

[0031] In addition, annealing is performed when only the coupling fixed region 160 is partially heat-treated. Therefore, it is possible to remove residual stress and the like that occurs in the coupling fixed region 160 due to the formation of the welded portion M. As a result, the crystal structure of the repair region A where the welded portion M is formed can be made uniform and soft, and the workability and toughness can be improved.

[0032] Annealing is performed by wrapping a heater H and a heat insulating material T around the coupling fixed region 160. After heating with the heater H, the coupling fixed region 160 is kept warm by the heat insulating material T. This makes it difficult for heat to be transferred to regions other than the coupling fixed region 160 that are not wrapped with the heat insulating material T, and makes it difficult for the heat treatment to affect regions other than the coupling fixed region 160. This makes it possible to effectively anneal the coupling fixed region 160 while minimizing the effect on the entire rotor body 10.

[0033] Moreover, the repair area A is an area including a damaged area D formed so as to be recessed from the outer surface F of the rotor body 10. Therefore, the damaged area D, such as a scratch formed on the rotor body 10, can be completely removed before repair.

[0034] Furthermore, a recess C is formed by scraping away the damaged area D. Additionally, a weld M is formed to fill in the recess C. Therefore, no matter what shape the damaged area D is formed in, the damaged area D can be reliably removed and repaired. Furthermore, because the recess C is formed by scraping away from the outer surface F, the weld M can be more easily adhered to the repair area A compared to when the weld M is formed directly on the damaged area D, and the weld M can be formed stably.

[0035] (Other embodiments) Although the embodiments of the present disclosure have been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes and the like that do not depart from the gist of the present disclosure are also included.

[0036] For example, the rotor 1 to be repaired is not limited to the rotor 1 having the above-mentioned structure. The rotor 1 may have a different shape as long as it is a rotor 1 of a rotating machine. Therefore, the number of impellers 20 provided on the rotor body 10 and the orientation of the impellers 20 are not limited to those exemplified above and can be changed as appropriate.

[0037] Furthermore, the rotor repair method S1 is not limited to being performed only when the damaged area D is formed in the coupling fixed area 160. The damaged area D may be formed in the bearing area 130 or the second shaft end area 120 as long as it is formed in the shaft end area 100.

[0038] In the rotor repair method S1, the damaged area processing step S3 is not necessarily performed. For example, the damaged area processing step S3 does not have to be performed. In that case, in the repair area welding step S4, welding is performed directly on the damaged area D, and the weld M is formed so as to directly cover the damaged area D.

[0039] Furthermore, the rotor repair method S1 is not limited to performing the partial heat treatment step S5 only once as in the present embodiment. The partial heat treatment step S5 may be performed multiple times as long as it is performed before the machined surface forming step S6.

[0040] <Additional Notes> The rotor repair method S1 described in the embodiment can be understood, for example, as follows.

[0041] (1) A rotor repair method S1 according to a first aspect is a method S1 for repairing a rotor having a rotor body 10 extending in an axial direction Da centered on an axis O, and a plurality of impellers 20 fixed to the rotor body 10 in a line in the axial direction Da, and includes the steps of: welding a repair area A of the rotor body 10 and filling the damaged area D formed so as to be recessed from an outer surface F of the rotor body 10 with a weld M; after performing the welding, performing a heat treatment only on the repair area A on the rotor 1; and, after performing the heat treatment, removing a portion of the weld M to form a machined surface GF that is smoothly connected to the outer surface F.

[0042] In such a rotor repair method S1, the damaged area D is welded to form a welded portion M. As a result, the damaged area D is filled with the welded portion M and repaired. However, when welding is performed only, the strength of the heat-affected area, which is the welded portion M and its periphery, may be insufficient compared to the required strength, or the hardness of the heat-affected area may exceed the required hardness. In response to this, by performing heat treatment, the strength of the heat-affected area can be increased and the hardness can be reduced to meet the required value. At this time, the heat treatment is performed only on the repair area A where the welded portion M is formed, without performing heat treatment on the entire rotor 1 or the entire rotor body 10. Since the entire rotor 1 or the entire rotor body 10 is not heated, the effects of thermal expansion, thermal contraction, distortion, etc. due to the heat treatment can be limited to the repair area A. In other words, the range in which changes in dimensions and surface roughness occur due to the effects of heat treatment can be limited to only the repair area A. Furthermore, after performing partial heat treatment only on the repair area A, a part of the welded portion M is cut to form a processed surface GF. Therefore, any changes in dimensions or surface roughness that occur only in the repair area A can be corrected by scraping it off. Also, because no heat treatment is performed after the machined surface GF is formed, changes in dimensions or surface roughness are suppressed from occurring on the machined surface GF once it has been formed. As a result, it is possible to reliably obtain a rotor 1 with the same quality and shape as before repair. Therefore, it is possible to stably maintain the shape and performance of the rotor 1 after repair.

[0043] (2) A rotor repair method S1 according to a second aspect is the rotor repair method S1 of (1), in which the repair area A is formed in an axial end region 100 including the end portion of the rotor body 10 in the axial direction Da.

[0044] This makes it possible to limit the effects of thermal expansion, thermal contraction, distortion, and the like caused by the heat treatment to the shaft end region 100. In other words, the range in which changes in dimensions and surface roughness occur due to the effects of the heat treatment can be limited to the shaft end region 100.

[0045] (3) A rotor repair method S1 relating to a second aspect is a rotor repair method S1 of (1) or (2), wherein the machined surface GF is formed at a constant distance from the axis O around the entire circumference of the rotor body 10.

[0046] This allows the repair area A where the welded portion M is formed to be processed to match the original shape with high precision over the entire circumference. Therefore, a rotor 1 having the same shape as before the repair can be obtained more reliably.

[0047] (4) A rotor repair method S1 according to a third aspect is any one of the rotor repair methods S1 of (1) to (3), in which the welded portion M is formed by laser welding.

[0048] By employing laser welding in this manner, it is possible to reduce the amount of heat input during welding, thereby suppressing the thermal effects on the rotor body 10. This makes it possible to suppress deformation of the rotor body 10 due to welding.

[0049] (5) A rotor repair method S1 according to a fourth aspect is any one of the rotor repair methods S1 of (1) to (4), in which the heat treatment is annealing.

[0050] This makes it possible to remove residual stress and the like that occurs in the repair area A due to the formation of the welded portion M. As a result, the crystal structure of the repair area A where the welded portion M is formed can be made uniform and soft, thereby improving the workability and toughness.

[0051] (6) A rotor repair method S1 relating to a fifth aspect is any one of the rotor repair methods S1 of (1) to (5), further including a step of removing the damaged area D to form the repair area A as a recess C recessed from the outer surface F, and the welding is performed so as to fill the recess C with the welded area M.

[0052] This allows the damaged area D to be reliably removed and repaired regardless of the shape of the damaged area D. Furthermore, by forming the recess C by scraping from the outer surface F, the weld M can be more easily attached to the repair area A than when the weld M is formed directly on the damaged area D, and the weld M can be formed stably. [Explanation of symbols]

[0053] 1...Rotor O…Axis line 20…Impeller 10...Rotor body 11...first end 12…Second end 100...Shaft end area 110...First shaft end area 120…Second shaft end area 130...Bearing area 140...Thrust supported area 150…Journal supported area 151...First journal supported area 152...Second journal supported area 160...Coupling fixed area F...Outer surface 8...Bearing 81...Thrust bearing 82...Journal bearing 9...Coupling member D...Damaged area Da…Axial direction Da1…first end side Da2…Second end side Dr…Radial direction S1...Rotor repair method S2: Damage confirmation step S3: Damaged area processing step S4: Repair area welding step S5…Partial heat treatment step S6: Surface preparation step A: Repair area C…Concave M: Welded part H: Heater T…Insulation material GF…Processing surface

Claims

1. A method for repairing a rotor including a rotor body extending in an axial direction about an axis line, and a plurality of impellers fixed to the rotor body and aligned in the axial direction, comprising the steps of: welding the repair area of ​​the rotor body to fill a damaged area recessed from an outer surface of the rotor body with a weld; after performing the welding, subjecting the rotor to a heat treatment only in the repair area; after performing the heat treatment, removing a portion of the welded portion to form a machined surface that is smoothly connected to the outer surface.

2. The rotor repair method according to claim 1 , wherein the repair area is formed in a shaft end area including an end portion in the axial direction of the rotor body.

3. 3. The rotor repair method according to claim 1, wherein the machined surface is formed at a constant distance from the axis over the entire circumference of the rotor body.

4. 3. The rotor repair method according to claim 1, wherein the welded portion is formed by laser welding.

5. 3. The method for repairing a rotor according to claim 1, wherein the heat treatment is annealing.

6. The method further includes the step of forming the repair area as a recess recessed from the outer surface by scraping the damaged area; 3. The method for repairing a rotor according to claim 1, wherein the welding is performed so as to fill the recess with the welded portion.

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