JP6204708B2 - Turbine rotor, steam turbine using the same, and method for manufacturing the turbine rotor - Google Patents

Description

  The present invention relates to a turbine rotor having a configuration in which at least two turbine rotor base materials are joined by butt welding at a welded portion, a steam turbine using the turbine rotor, and a method of manufacturing the turbine rotor.

  The rotor of the steam turbine has a long axial length. Moreover, the high pressure side rotor is required to have high temperature creep rupture strength, and the low pressure side rotor is required to have tensile strength and toughness. For this reason, when a steam turbine rotor is formed with one member, each characteristic cannot be satisfied.

  In order to solve this problem, conventionally, a technology has been applied in which the high-pressure rotor is formed of a material having excellent high-temperature creep rupture strength, the low-pressure rotor is formed of a material having excellent tensile strength and toughness, and these are integrated by welding. Has been.

  The turbine rotor is provided with a sealed hollow portion in order to reduce a load applied at the time of starting and stopping the plant. When the turbine rotor is welded, first, the bottom of the butt portion that is grooved in the turbine rotor is welded. In the first layer, it is necessary to completely melt the groove bottom and to penetrate to the inner periphery of the turbine rotor. In general butt welding, when the first layer is penetrated to the back surface of the plate, an inert gas is injected from the back side of the groove bottom portion to be welded in order to suppress oxidation of the surface of the weld bead.

  However, the sealed hollow portion of the turbine rotor is closed by abutting the turbine rotor during welding. Therefore, the inert gas cannot be injected into the sealed hollow portion of the turbine rotor from the back side of the groove bottom portion. For this reason, the inner peripheral side of the turbine rotor in the first layer is excessively oxidized, and surface roughness is generated as a starting point of crack propagation. Furthermore, since the weld bead on the inner periphery of the turbine rotor cannot be observed, the possibility of crack propagation cannot be determined.

  In Patent Document 1, in order to fill the inside with an inert gas without deteriorating the quality of the turbine rotor after welding, a gas introduction hole that penetrates the bottom of the groove portion formed for welding is formed, After said welding, the technique of sealing the said hole by welding is disclosed.

  In Patent Document 2, an inspection hole having a stepped portion at the back and a threaded portion at the entrance is formed in the vicinity of the welded joint portion, and an X-ray source is inserted to perform a radiation transmission test. A method for inspecting a welded joint portion of a welding rotor is disclosed in which a packing is inserted into a portion, a plug is screwed into a screw portion, and caulking is performed on the periphery of the plug.

JP 2012-202225 A Japanese Patent Laid-Open No. 9-108883

  An object of the present invention is to easily inject an inert gas that is a back shield and inspect a welded portion of a welded rotor by a borescope when manufacturing a turbine rotor.

  The present invention provides a turbine rotor having a configuration in which at least two turbine rotor base materials are joined by butt welding at a welded portion, and two recesses provided at the end portions of the two turbine rotor base materials are joined together. A hollow portion is formed in a state, and one of the turbine rotor base material is provided with a hole penetrating obliquely from the outer surface portion to the hollow portion toward the welded portion, and the hole is sealed. Features.

  According to the present invention, when manufacturing a turbine rotor, an inert gas which is a back shield is injected, and the time required for inspection of the welded portion of the welded rotor of the borescope can be shortened. Thereby, the reliability of back wave welding can be improved.

It is a schematic block diagram which shows a steam turbine. 1 is a cross-sectional view illustrating an overall structure of a turbine rotor according to a first embodiment. It is a partial expanded sectional view which shows the welding part of the turbine rotor of FIG. 2A. 1 is a schematic diagram illustrating a turbine rotor welding apparatus according to Embodiment 1. FIG. 1 is a flowchart showing a turbine rotor welding process according to Embodiment 1. FIG. It is a fragmentary sectional view showing change of a welding part concerning Example 3. FIG. 6 is a cross-sectional view showing an example of a turbine welded rotor according to a fourth embodiment. FIG. 6 is a cross-sectional view showing an example of a turbine welded rotor according to a fourth embodiment. FIG. 6 is a cross-sectional view showing an example of a turbine welded rotor according to a fourth embodiment. FIG. 6 is a cross-sectional view illustrating an example of a welding rotor for a low pressure turbine according to a fourth embodiment. FIG. 6 is a cross-sectional view illustrating an example of a welding rotor for a low pressure turbine according to a fourth embodiment. FIG. 6 is a cross-sectional view illustrating an example of a welding rotor for a low pressure turbine according to a fourth embodiment. FIG. 6 is a cross-sectional view illustrating an example of a welding rotor for a low pressure turbine according to a fourth embodiment. It is a fragmentary sectional view which shows the structure (upper limit value of angle θ of a hole) of the welding part and hole which concern on Example 5. FIG. It is a fragmentary sectional view which shows the structure (lower limit of angle θ of a hole) of the weld part and hole which concern on Example 5. FIG.

  A steam turbine is composed of a boiler, a turbine rotor, a moving blade, a generator, and the like.

  FIG. 1 schematically shows the configuration of a steam turbine.

  The turbine rotor 51 shown in this figure is provided with a high-pressure turbine 54, an intermediate-pressure turbine 55, low-pressure turbines 56 a and 56 b, and a generator 57 around the shaft. A main steam pipe 52 is connected to the high pressure turbine 54. A boiler reheater 53 is provided between the high pressure turbine 54 and the intermediate pressure turbine 55.

  Steam flows from the main steam pipe 52 and flows into the high-pressure turbine 54. Thereafter, the steam is heated by the boiler reheater 53 and flows into the intermediate pressure turbine 55 and the low pressure turbines 56a and 56b. The turbine rotor 51 is rotated by the force of these steams, and electric energy is generated in the generator 57 attached to the end of the turbine rotor 51.

  The present invention relates to the high-pressure turbine 54, the intermediate-pressure turbine 55, and the low-pressure turbines 56a and 56b, and particularly to the low-pressure turbines 56a and 56b.

  The present inventor examined the relationship between the shape of the sealed hollow portion and the stress concentration distribution in the turbine rotor having the sealed hollow portion in which the turbine rotor divided into at least two parts is connected via a welded portion by butt welding. As a result, a hole (through hole) that penetrates from the outer surface of the rotor toward the sealed hollow portion is provided, and when sealing it, it is not always necessary to perform caulking after plugging with a plug as in the conventional example. Was revealed. For example, a bolt may be embedded or sealed by welding.

  Furthermore, it was found that by providing the same inner diameter portion in the sealed hollow portion, the stress concentration on the portion is relatively low compared to the others. For this reason, it is desirable to provide the holes in the same inner diameter portion.

  The present inventor has proposed the present invention for these problems, and conducted tests and the like as in the following examples. As a result, the prospect of solving the above-mentioned problem was obtained.

  Table 1 summarizes the construction conditions and specifications in each example.

  Hereinafter, although it demonstrates in detail using a specific Example, this invention is not limited to these Examples.

  In this example, 3.5% Ni—Cr—Mo—V steel was used, but there are no restrictions on the combination of rotor materials. For example, a different material from Ni-base superalloy, 12% Cr steel, or Cr—Mo—V steel, or a combination of the same materials may be used.

  FIG. 2A is a cross-sectional view showing the overall structure of a welding rotor for a low-pressure turbine. In this figure, welding rotor 100 includes turbine rotor base materials 31a and 31b divided into at least two parts. The turbine rotor base materials 31a and 31b are joined together by butt welding. The site where butt welding has been performed is a welded portion 34. A sealed hollow portion 32 is provided between the turbine rotor base materials 31a and 31b. The sealed hollow portion 32 is intended to reduce the heat capacity and the thickness of the welded portion.

  2B is a partially enlarged cross-sectional view showing a welded portion of the turbine rotor of FIG. 2A.

  In this figure, the structure of the welding part 34 couple | bonded by the weld metal 33 is shown. A hole 35 is provided in the turbine rotor base material 31a. The hole 35 penetrates from the outer surface portion of the turbine rotor base material 31a to the sealed hollow portion 32, and the distance from the central axis (rotary axis) of the turbine rotor base material 31a to the inner wall surface (the radius of the sealed hollow portion 32). Is formed obliquely toward the welded portion 34 so as to reach a uniform region 37 (same inner diameter portion). The hole 35 is sealed in the vicinity of the outer surface portion of the turbine rotor base material 31a (sealing portion 36). The sealing portion 36 is desirably formed by welding. This is because when the sealing portion 36 has a threaded portion or a packing, steam may leak into the sealed hollow portion 32 during operation or the like.

  The hole 35 is for injecting a back shield (inert gas) at the time of reverse wave welding and for inserting a borescope at the time of reverse wave shape inspection. By using the former for the purpose, the back wave oxidation can be suppressed and the pressure fluctuation can be reduced, so that the back wave welding can be stably performed. Moreover, since the formation of a back wave can be easily confirmed by using it for the latter purpose, a highly reliable welded rotor can be provided.

  The hole 35 is closed by providing the sealing portion 36 after the welding of the welding portion 34 and the inspection by the borescope are completed.

  As described above, according to the present invention, since the inspection by the borescope is easy, the reliability of the back wave welding can be improved even in a construction environment where the back shield cannot be used, and the welded portion having no defect. Can be provided. Moreover, the inspection time of a welding rotor can be shortened.

  FIG. 3 shows an outline of a tungsten-inert gas welding apparatus used for welding the turbine rotor.

  In this figure, the welding device 40 has a drive device 43, a welding mechanism 44, a torch 48 and a control device 47, and a gas cylinder 49 is connected via a gas hose 152. The inert gas in the gas cylinder 49 is sent to the torch 48 via the gas hose 151. Nitrogen or argon is used as the inert gas. A signal cable 45 for transmitting and receiving signals is provided between the driving device 43 and the control device 47. A signal cable 46 for transmitting and receiving signals is provided between the welding mechanism 44 and the control device 47.

  The turbine rotor 41 is installed in the rotor rotating device 150 and can be rotated around the central axis of the turbine rotor 41. The rotor rotating device 150 is connected to the control device 47 via a signal cable 154, and the control device 47 can control the rotation (rotational speed and direction) of the turbine rotor 41.

  Moreover, the earth cable 153 is connected to the turbine rotor 41, and it can suppress that the electric potential of the turbine rotor 41 changes during welding.

  The welding mechanism 44 can be moved by the drive device 43, and is configured such that welding can be performed by bringing the torch 48 close to the welding portion of the turbine rotor 41.

  The drive device 43 shown in this figure is a self-supporting type that moves in close contact with the turbine rotor 41. However, the drive device 43 may be moved by an external force such as a scanning arm.

  In this embodiment, the low heat input welding method is tungsten inert gas (Tungsten Inert Gas Arc, hereinafter abbreviated as TIG) welding with a heat input of 15 to 25 KJ / cm, but laser welding or electron beam. It may be welding (EBW). Further, the high heat input welding method may be submerged arc welding (SAW), covering arc (SMAW) welding, or mag (MAG) welding with a heat input of 20 to 30 KJ / cm.

  Moreover, in this figure, although the direction of the arc is downward, it may be horizontal.

  FIG. 4 shows an example of the flow of the turbine rotor welding process.

  First, one rotor base material is incorporated into the other rotor base material (S101). Next, the start of the welding process is instructed (S102). In order to relieve the thermal stress in welding, the rotor base material is preheated (S103). Examples of the apparatus used for the preheating include an electric furnace, a gas burner, a high frequency induction heater, and the like, but other apparatuses may be used.

  And welding is performed in order to form the center part of a welding part using the welding apparatus shown in FIG. 3 (S105). Welding is performed to form the surface layer of the weld. (S106).

  Thereafter, annealing is performed to remove residual stress in the welded portion (S108). Examples of the apparatus used at this time include an electric furnace, a gas burner, and a high frequency induction heater, but other apparatuses may be used.

  Thereafter, a weld defect inspection of the weld is performed (S109). Examples of inspection methods include penetration testing (PT), visual inspection (VT), ultrasonic testing (UT), radiation transmission testing (RT), and magnetic particle testing (MT), but other methods may be used. Absent.

  The presence / absence of a defect is determined (S110). If a defect is detected, it is further determined whether the defect size is acceptable from the viewpoint of mechanical strength (S111). If the defect size is not acceptable, the weld is cut (S112). Then, groove processing is performed on the rotor end face (S113), and the process returns to the preheating step (S103).

  When no defect is detected in the determination of the presence or absence of defects (S110), or when the defect size is within an allowable range in the determination of defect size (S111), the hole is sealed (S114), and the welding process Is finished (S115).

  The manufacturing method of the turbine rotor is summarized as follows.

  Turbine rotors are manufactured by passing through one of the two turbine rotor base materials having a recess at the end from the outer surface portion of the turbine rotor base material to the recess, obliquely toward the end of the turbine rotor base material. Holes are formed, hollows are formed by joining the two turbine rotor base materials by butt welding, matching the recesses provided at the ends of the two turbine rotor base materials, and sealing the holes To do. Here, after aligning the recesses, one turbine rotor base material may be provided with holes.

  Furthermore, it is desirable to inspect the weld with a borescope and seal the hole after the inspection.

  In butt welding, it is desirable to inject an inert gas into the hollow portion through the hole.

  In the present embodiment, as compared with the first embodiment, only the rotor base material (the turbine rotor base material 31a in FIG. 2B) having holes is different. Others are the same as those in the first embodiment, and therefore, detailed description is omitted, and only differences are described.

  The combination of the rotor base materials in this example is a Ni-based alloy and CrMoV steel. In this case, the Ni-based alloy cannot sufficiently relieve the residual stress due to the restriction of the heat treatment conditions of the CrMoV steel. Therefore, if the hole is provided at a location having a high residual stress, the risk of crack growth increases. Therefore, when the combination of the rotor base materials is a ferrite base material such as CrMoV steel and a Ni-based alloy as in this embodiment, the holes are provided in the ferrite base rotor base material having a low residual stress.

  This example differs from Example 1 only in the number of holes. Others are the same as those in the first embodiment, and therefore, detailed description is omitted, and only differences are described.

  FIG. 5 shows a cross section in the radial direction of the rotor.

  In this figure, three holes 235 are provided in the same cross section of the turbine rotor base material 231.

  The hole 235 becomes a factor of generation of vibration when the rotor rotates. Therefore, two or more holes 235 are desirable. In this figure, there are three locations. Further, it is desirable that the holes 235 are equally divided in the circumferential angle in the same cross section (circumferential direction). Thereby, generation | occurrence | production of a vibration can be suppressed to the minimum.

  However, considering the time for processing the hole and the ease of inspection, the hole 235 is preferably within 12 locations.

  This embodiment differs from the first embodiment only in the combination of rotor materials and the application site. Others are the same as those in the first embodiment, and therefore, detailed description is omitted, and only differences are described.

  In Example 1, it applied to the low pressure turbine rotor which consists of a 3.5% NiCrMoV steel and a 3.5% NiCrMoV steel rotor.

  However, the combination of the rotor material and the application site is not limited to this, and is a medium comprising a high-pressure turbine rotor base material 60 made of Ni-base alloy as shown in FIG. 6A and a medium-pressure turbine rotor base material 62 made of 12% Cr steel. 6B, a medium pressure turbine rotor composed of a Ni-base alloy high pressure turbine rotor base 60 and a CrMoV steel medium pressure turbine rotor base 62 as shown in FIG. 6B, and a CrMoV steel made as shown in FIG. 6C. The present invention can be similarly applied to an intermediate pressure turbine rotor including the low pressure turbine rotor 61.

  Furthermore, in the low pressure turbine rotor made of 3.5% NiCrMoV steel and 3.5% NiCrMoV steel rotor material as shown in FIGS.

  The present embodiment is different from the first embodiment in that the hole angle and position are limited. Others are the same as those in the first embodiment, and therefore, detailed description is omitted, and only differences are described.

  One purpose of the hole in the rotor is to inspect the back wave with a borescope. Therefore, it is preferable that the hole is close to the back wave on the extended line of the hole. Therefore, it is desirable that the extension line of the hole be in the same radius portion that does not interfere with the protrusion in the rotor sealing hollow portion and extends in the axial direction from the viewpoint of structural strength.

Figure 8A is a partial cross-sectional view showing the configuration of the welded portion and the hole (examples of the upper limit theta _max angle theta of holes).

  In this figure, the angle of the hole 35 provided in the turbine rotor base material 31a shown in FIG. 2B and the dimensions of the periphery thereof are described. Moreover, this figure has shown the case where the hole 35 is provided in linear form.

  In this figure, the hole 35 penetrates from the outer surface portion of the turbine rotor base material 31a to the sealed hollow portion 32, and the distance from the central axis of the turbine rotor base material 31a to the inner wall surface (the radius of the sealed hollow portion 32). Is formed obliquely toward the welded portion 34 so as to reach a uniform region 37 (same inner diameter portion). The hole 35 is sealed in the vicinity of the outer surface portion of the turbine rotor base material 31a (sealing portion 36).

  The turbine rotor base material 31 a has a protruding portion 81 (also referred to as “a raised portion” or “ridge line portion”) on the side of the sealed hollow portion 32. The weld metal 33 has an inner end 82 on the sealed hollow portion 32 side.

  In addition, this figure and FIG. 8B mentioned later are sectional views, and since the end portions of the turbine rotor base materials 31a and 31b forming the sealed hollow portion 32 are ring-shaped, the projecting portion 81 and the like are also ring-shaped. In the following description, there are cases where two-dimensional terms in the cross-sectional view are used.

  In the cross section shown in FIG. 8A, the range of the region 37 is represented as a straight line. On the other hand, outside the region 37 is a shape having a curvature in the central axis direction of the turbine rotor base material 31a.

  In FIG. 8A, the angle between the tangential plane of the outer surface portion of the turbine rotor base material 31a and the central axis of the hole 35 is θ. The inner diameter (diameter) of the hole 35 is d.

For the distance between the center axis direction of the turbine rotor material 31a relative to the central axis of the weld 34, (corner (vertex) in the sectional view) until the L ₁ ridgeline of the protrusion 81, the area 37 projections until the end of the part 81 side and L _2, it has a distance from the center of the outer surface of the turbine rotor material 31a of the holes 35 and L. About L, it can also be said that it is the distance from the center in the outer surface part of a hole to the center cross section of a welding part. Here, the central cross section of the welded part corresponds to the central axis of the welded part 34 in this figure.

In addition, the thickness of the turbine rotor base material 31a in the region 37 (same inner diameter portion) is t. Furthermore, the difference (radius difference) between the distance to the apex of the protrusion 81 and the distance to the region 37 is defined as t ₁ with reference to the central axis of the turbine rotor base material 31a.

  In the drawing, the projection 81 side of the hole 35 in the region 37 coincides with the end of the region 37 on the projection 81 side. In addition, an extension line (broken line) on the protruding portion 81 side of the hole 35 intersects with the apex of the protruding portion 81.

When expressing the definition of the above three-dimensionally, t ₁ is the difference of the radius of the ridge and the same inner diameter portion of the raised portion of the end portion, L ₁ is the distance from the central plane to the ridge line, L ₂ is a central the distance from the cross section to the center section side of the same inner diameter, L ₃ is the distance from the central plane to the other side of the center section side of the same inner diameter.

FIG. 8B is a partial cross-sectional view showing the configuration of the welded part and the hole (an example of the lower limit value θ _min of the hole angle θ).

In this figure, with respect to the distance in the central axis direction of the turbine rotor material 31a relative to the center axis of the welding unit 34, from the protruding portion 81 of the region 37 to the far end as a L _3.

  In this figure, the side of the region 37 far from the projection 81 of the hole 35 coincides with the end of the region 37 far from the projection 81 side. In addition, an extension line (broken line) on the protruding portion 81 side of the hole 35 intersects with the apex of the protruding portion 81.

  According to the definition of the above dimensions and angles, the range of the angle θ of the hole 35 can be defined as the following formulas (1) to (4).

θ _min ≦ θ ≦ θ _max (1)
L _min ≦ L ≦ L _max Formula (2)
tan θ _max = t ₁ / (L ₂ −L ₁ ) = t / (L _min −L ₂ ) (3)
tan θ _min = t ₁ / (L ₃ −L ₁ ) = t / (L _max −L ₃ ) (4)
Here, L _min represents a value corresponding to L in FIG. 8A, and L _max represents a value corresponding to L in FIG. 8B.

  When the above formulas (1) to (4) are arranged, the following formulas (5) and (6) are obtained.

tan ⁻¹ {t ₁ / (L ₃ −L ₁ )} ≦ θ ≦ tan ⁻¹ {t ₁ / (L ₂ −L ₁ )} Equation (5)
t (L ₂ −L ₁ ) / t ₁ + L ₂ ≦ L ≦ t (L ₃ −L ₁ ) / t ₁ + L ₃ Formula (6)
Moreover, the hole 35 may not be a straight line. The hole 35 only needs to have an angle defined by the above formula (5) only at the portion in contact with the sealed hollow portion 32.

  Using these equations, specific numerical values of the sealed hollow portion were calculated based on the actual dimensions of the turbine rotor. As a result, the following equations (7) and (8) were obtained.

10 ≦ θ ≦ 80 (degrees) (7)
30 ≦ L ≦ 900 (mm) (8)
With the above configuration, when the borescope is inserted into the hole 35 to inspect the back welded portion of the welding rotor (projection 81 and inner end portion 82), the front end of the borescope is located near the back welded portion. Since it reaches as it is, it is possible to observe the back welded portion without bending (deforming) the front end of the borescope.

  31a, 31b: Turbine rotor base material, 32: Sealed hollow part, 33: Weld metal, 34: Welded part, 35: Hole, 36: Sealed part, 37: Area, 51: Turbine rotor, 52: Main steam pipe, 53: Boiler reheater, 54: High pressure turbine, 55: Medium pressure turbine, 56a, 56b: Low pressure turbine, 57: Generator, 81: Projection, 82: Inner end, 100: Welding rotor.

Claims (15)

It has a configuration in which at least two turbine rotor base materials are joined by butt welding at a welded portion, and the two concave portions provided at the end portions of the two turbine rotor base materials have a hollow portion in a joined state. One of the turbine rotor base materials is formed with a hole that penetrates obliquely from the outer surface portion to the hollow portion toward the welded portion and that extends inward from the protrusion in the hollow portion. The turbine rotor is characterized in that the hole is sealed.   The turbine rotor according to claim 1, wherein the hollow portion side of the hole is located at the same inner diameter portion of the hollow portion.   3. The turbine rotor according to claim 1, wherein the hole is provided in a lower residual stress of the two coupled turbine rotor base materials. 4.   The turbine rotor according to claim 3, wherein the two turbine rotor base materials are a ferrite system and an austenite system, and the holes are provided in the ferrite system.   The turbine rotor according to claim 1, wherein two or more holes are provided.   The turbine rotor according to claim 5, wherein the plurality of holes arranged in a circumferential direction of the turbine rotor base material equally divide the angle in the circumferential direction.   The turbine rotor according to claim 1, wherein the hole is sealed with a bolt.   The turbine rotor according to claim 1, wherein the hole is sealed by weld overlay.   The two turbine rotor base materials are Ni-base alloy and 12% Cr steel, Ni-base alloy and CrMoV steel, 12% Cr% steel and CrMoV steel, CrMoV steel and 3.5% NiCrMoV steel, or 3.5% 4. The turbine rotor according to claim 3, wherein the turbine rotor is a combination of any of NiCrMoV steel and 3.5% NiCrMoV steel. The angle θ formed between the tangential plane of the outer surface portion and the central axis of the hole, and the range of the distance L from the center of the outer surface portion of the hole to the central cross section of the welded portion are expressed by the following formula (5) and It is represented by (6), The turbine rotor as described in any one of Claims 2-9 characterized by the above-mentioned.
tan ⁻¹ {t ₁ / (L ₃ −L ₁ )} ≦ θ ≦ tan ⁻¹ {t ₁ / (L ₂ −L ₁ )} Equation (5)
t (L ₂ −L ₁ ) / t ₁ + L ₂ ≦ L ≦ t (L ₃ −L ₁ ) / t ₁ + L ₃ Formula (6)
(Where t ₁ is the difference in radius between the ridge line of the raised portion at the end and the same inner diameter part, L ₁ is the distance from the central cross section to the ridge line, and L ₂ is from the central cross section. wherein a distance to the center section side of the same inner diameter, L ₃ is the distance from the central plane to the other side of the center section side of the same inner diameter portion.) The turbine rotor according to claim 10, wherein the range of θ and L is expressed by the following formulas (7) and (8).
10 ≦ θ ≦ 80 (degrees) (7)
30 ≦ L ≦ 900 (mm) (8)   A steam turbine comprising the turbine rotor according to claim 1. In one of the two turbine rotor base materials having a recess at the end, a hole that penetrates obliquely from the outer surface portion of the turbine rotor base material to the recess toward the end of the turbine rotor base material And the step of providing an inward portion from the protrusion in the hollow portion and the recesses provided at the end portions of the two turbine rotor base materials are combined to push the two turbine rotor base materials. A method for manufacturing a turbine rotor, comprising: a step of forming a hollow portion by bonding by means of a mating welding; and a step of sealing the hole.   The method for manufacturing a turbine rotor according to claim 13, further comprising a step of inspecting the welded portion with a borescope, and sealing the hole after the inspection. The method for manufacturing a turbine rotor according to claim 13 or 14, wherein an inert gas is injected into the hollow portion through the hole during the butt welding.

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