JP2022088828A - High corrosion-resistance stationary blade of geothermal turbine, stationary-blade blade row of geothermal turbine and manufacturing method of high corrosion-resistance stationary blade of geothermal turbine - Google Patents

Abstract

To provide a high corrosion-resistance stationary blade of a geothermal turbine having excellent corrosion resistance, and stably operable under a corrosive environment for a long period of time, a stationary-blade blade row of the geothermal turbine and a manufacturing method of the high corrosion-resistance stationary blade of the geothermal turbine.SOLUTION: A stationary blade 10 in this embodiment is used under a corrosive environment in which a working medium containing a corrosive component flows, and supported between a diaphragm outer ring 113 and a diaphragm inner ring 115 of a geothermal turbine. The stationary blade 10 comprises a blade effective part 20, an outer ring fitment part 30 formed at one end part of the blade effective part 20, and fitted to the diaphragm outer ring 113, and an inner ring fitment part 40 formed at the other end part of the blade effective part 20, and fitted to the diaphragm inner ring 115. The blade effective part 20, the outer ring fitment part 30 and the inner ring fitment part 40 are integrated with one another, and formed of Ni-group alloys.SELECTED DRAWING: Figure 1

Description

Embodiments of the present invention relate to a method for manufacturing a geothermal turbine's highly corrosion-resistant static blade, a geothermal turbine's blade row, and a geothermal turbine's high corrosion-resistant static blade.

Conventionally, in a geothermal turbine operated in a corrosive environment, a technique for reducing contact between a component and a corrosive environment has been adopted by providing a coating layer made of a corrosion-resistant material on the surface of the component.

The steam temperature introduced into the geothermal turbine is lower than, for example, the steam temperature of the steam turbine into which the steam generated by the boiler or the like is introduced. Therefore, conventionally, the constituent members of the geothermal turbine are made of Fe-based alloy steel such as 12Cr steel and CrMoV steel.

The stationary blade (nozzle plate), which is a component of the geothermal turbine, is also made of Fe-based alloy steel such as 12Cr steel. A coating layer (corrosion-resistant coating layer) made of a corrosion-resistant material is formed on the surface of the stationary blade.

Japanese Unexamined Patent Publication No. 2004-270484

The working medium of a geothermal turbine contains a large amount of corrosive components such as carbon dioxide, hydrogen sulfide, chlorine, and ammonia in acidic steam. Geothermal turbine vanes are used in corrosive environments exposed to steam, which is a working medium containing such corrosive components.

Even if the blade is covered with a corrosion-resistant coating layer, if cracks or peeling occur in the coating layer, the entire exposed blade will be corroded, pitted corrosion, and stress corrosion cracking will occur. It is necessary to frequently renew the static wing and repair the static wing.

The problem to be solved by the present invention is the high corrosion-resistant static blade of a geothermal turbine, the static blade row of a geothermal turbine, and the height of a geothermal turbine, which have excellent corrosion resistance and can be operated stably for a long period of time in a corrosive environment. It is to provide a method for manufacturing a corrosion-resistant static wing.

The highly corrosion-resistant static blade of the geothermal turbine of the embodiment is used in a corrosive environment in which a working medium containing a corrosive component flows, and is supported between the outer ring of the diaphragm and the inner ring of the diaphragm of the geothermal turbine.

The highly corrosion-resistant static wing is formed at one end of the wing effective portion and the wing effective portion, and is formed at the outer ring fitting portion fitted to the diaphragm outer ring and the other end of the wing effective portion. The inner ring fitting portion to be fitted to the inner ring of the diaphragm is provided. The blade effective portion, the outer ring fitting portion, and the inner ring fitting portion are integrally formed of a Ni-based alloy.

It is a figure which shows the cross section in the vertical direction of the steam turbine provided with the stationary blade of an embodiment. It is a top view of the stationary wing when the stationary wing of the embodiment is seen from the circumferential direction side. It is a top view of the stationary blade when the stationary blade of the embodiment is viewed from the upstream side. It is a top view of the stationary blade row when the stationary blade row including the stationary blade of the embodiment is viewed from the upstream side. It is a figure which shows the AA cross section of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a vertical cross section of a steam turbine 100 provided with a stationary blade 10 according to an embodiment. The steam turbine described below is a geothermal turbine. Note that FIG. 1 omits the configuration of some turbine paragraphs.

As shown in FIG. 1, the steam turbine 100 includes a casing 110, and a turbine rotor 111 is penetrated in the casing 110. The turbine rotor 111 is formed with a rotor wheel 111a that projects outward in the radial direction over the circumferential direction. The rotor wheel 111a is formed in a plurality of stages in the central axis direction of the turbine rotor 111.

Here, the circumferential direction is a circumferential direction centered on the central axis O of the turbine rotor 111, that is, around the axis of the central axis O. Further, the outer side in the radial direction is a side away from the central axis O in the radial direction. The radial direction is a direction perpendicular to the central axis O with the central axis O as the base point. Further, the central axial direction of the turbine rotor 111 is simply referred to as an axial direction below.

A plurality of blades 112 are planted in the rotor wheel 111a in the circumferential direction. The blade row 51 having a plurality of blades 112 in the circumferential direction is configured in a plurality of stages in the axial direction. The turbine rotor 111 is rotatably supported by a rotor bearing (not shown).

A diaphragm outer ring 113 is installed on the inner circumference of the casing 110. The diaphragm outer ring 113 has, for example, an annular extending portion 114 that extends in an annular shape on the downstream side and surrounds the periphery of the rotor blade 112. Inside the diaphragm outer ring 113, a diaphragm inner ring 115 is installed. The downstream side means the downstream side in the main flow direction of the working fluid.

A plurality of stationary blades 10 are arranged in the circumferential direction between the diaphragm outer ring 113 and the diaphragm inner ring 115 to form a stationary blade row 50. The diaphragm outer ring 113 supports the stationary blade 10 from the outside in the radial direction, and the diaphragm inner ring 115 supports the stationary blade 10 from the inside in the radial direction. Here, the inner side in the radial direction is the side approaching the central axis O in the radial direction (the central axis O side). The stationary blade 10 functions as a highly corrosion-resistant static blade.

The stationary blade row 50 is provided with a plurality of stages alternately with the moving blade row 51 in the axial direction. The stationary blade row 50 and the moving blade row 51 located immediately downstream of the stationary blade row 50 constitute one turbine paragraph. The configuration of the stationary blade 10 will be described in detail later.

An annular steam passage 116 through which the working fluid flows is formed between the diaphragm outer ring 113 and the diaphragm inner ring 115. For example, the cross section of the steam passage 116 gradually expands as it goes downstream.

A ground seal portion 117 is provided between the turbine rotor 111 and the casing 110 in order to prevent steam from leaking to the outside. Further, a seal portion 118 is provided between the turbine rotor 111 and the diaphragm inner ring 115 in order to prevent steam from leaking to the downstream side between the turbine rotor 111 and the diaphragm inner ring 115.

Further, seal fins 117a and 118a are provided on the inner peripheral surfaces of the ground seal portion 117 and the seal portion 118. The gland seal portion 117 and the seal portion 118 are provided in the circumferential direction.

Further, the steam turbine 100 is provided with a steam inlet pipe (not shown) for introducing steam from the steam introduction pipe 120 into the inside of the steam turbine 100 through the casing 110. The steam introduced into the steam turbine 100, which is a geothermal turbine, is an acidic steam containing corrosive components such as carbon dioxide, hydrogen sulfide, chlorine, and ammonia.

An exhaust passage (not shown) for exhausting the steam expanded in each turbine paragraph is provided on the downstream side of the turbine paragraph in the final stage (not shown).

Next, the stationary blade 10 and the stationary blade row 50 of the embodiment will be described in detail.

FIG. 2 is a plan view of the stationary blade 10 of the embodiment when viewed from the circumferential direction side. FIG. 3 is a plan view of the stationary wing 10 when the stationary wing 10 of the embodiment is viewed from the upstream side. FIG. 4 is a plan view of the stationary blade row 50 when the stationary blade row 50 including the stationary blade 10 of the embodiment is viewed from the upstream side. FIG. 5 is a diagram showing a cross section taken along the line AA of FIG.

Here, FIG. 2 is a plan view of the stationary blade 10 in a state of being fitted to the diaphragm outer ring 113 and the diaphragm inner ring 115 when viewed from the circumferential direction side. FIG. 3 is a plan view of the stationary blade 10 in a state of being fitted to the diaphragm outer ring 113 and the diaphragm inner ring 115 when viewed from the upstream side. FIG. 5 shows a meridional cross-sectional view of the stationary blade row 50 in which the fixing pin 150 is located. Further, in FIG. 5, a part of the upper half diaphragm outer ring 113a is omitted.

The stationary blade 10 is used in a corrosive environment in which a working medium containing corrosive components such as carbon dioxide, hydrogen sulfide, chlorine, and ammonia flows.

As shown in FIG. 2, the stationary blade 10 includes a blade effective portion 20, an outer ring fitting portion 30, and an inner ring fitting portion 40. The blade effective portion 20, the outer ring fitting portion 30, and the inner ring fitting portion 40 are integrally configured. That is, the stationary blade 10 is an integral structure in which the blade effective portion 20, the outer ring fitting portion 30, and the inner ring fitting portion 40 are integrally formed.

The blade effective portion 20 is located in the annular steam passage 116 through which the working fluid flows and is exposed to the working fluid. In FIG. 2, the leading edge 20a of the blade effective portion 20 is the left side portion, and the trailing edge 20b of the blade effective portion 20 is the right side portion. The working fluid flows from the leading edge 20a side to the trailing edge 20b side between the blade effective portions 20 located with a predetermined gap in the circumferential direction.

The outer ring fitting portion 30 is formed at one end of the blade effective portion 20. As shown in FIG. 4, the outer ring fitting portion 30 is fitted to the diaphragm outer ring 113. The outer ring fitting portion 30 has a fitting recess 32 for fitting with the diaphragm outer ring 113.

As shown in FIGS. 2 and 3, the fitting recess 32 is composed of, for example, an arcuate groove portion recessed downstream in the circumferential direction from the end surface 31 on the upstream side of the outer ring fitting portion 30. The shape of the fitting recess 32 corresponds to the shape of the fitting convex portion 131 of the diaphragm outer ring 113, which will be described later. The fitting recess 32 is formed so as to penetrate the end surface 31 on the upstream side of the outer ring fitting portion 30 in the circumferential direction.

Here, the upstream side means the upstream side in the flow direction of the main flow of the working fluid. Here, an example is shown in which the cross-sectional shape (cross-section perpendicular to the circumferential direction) of the fitting recess 32 is rectangular.

The inner ring fitting portion 40 is formed at the other end of the blade effective portion 20. The inner ring fitting portion 40 is fitted to the diaphragm inner ring 115 as shown in FIG. The inner ring fitting portion 40 has a fitting convex portion 41 for fitting with the diaphragm inner ring 115.

As shown in FIGS. 2 and 3, the fitting convex portion 41 is composed of, for example, an arc-shaped ridge portion protruding toward the central axis O side in the circumferential direction from the bottom surface 42 of the inner ring fitting portion 40. To. The shape of the fitting convex portion 41 is formed corresponding to the shape of the fitting concave portion 141 of the inner ring 115 of the diaphragm, which will be described later. Here, an example is shown in which the cross-sectional shape (cross-section perpendicular to the circumferential direction) of the fitting convex portion 41 is rectangular.

Here, the stationary blade 10 shown in FIGS. 2 and 3 has a configuration in which one blade effective portion 20 is provided between the outer ring fitting portion 30 and the inner ring fitting portion 40. Then, by arranging the plurality of stationary blades 10 in the circumferential direction between the diaphragm outer ring 113 and the diaphragm inner ring 115, the stationary blade row 50 is configured.

The above-mentioned stationary blade 10 comes into direct contact with a working medium containing a corrosive component. That is, the corrosion-resistant coating layer for preventing corrosion is not formed on the surface of the stationary blade 10 that comes into contact with the working medium containing the corrosion component.

Further, the stationary blade 10 has the following characteristics.

In the radiation flaw detection test according to JIS Z 3104, the stationary wing 10 has no detection of defects inside the stationary wing 10.

In the radiation flaw detection test, no significant defect was detected not only in the final form of the stationary blade 10 but also in the stationary blade structure after casting (the stationary blade structure before the hot isotropic pressure pressurization treatment). As described above, in the radiation flaw detection test, no significant defect was detected inside the final form of the stationary blade 10 subjected to the hot isotropic pressure pressure treatment described later, and it was also significant in the still blade structure after casting. No defects are detected.

Therefore, in the manufacturing process of the stationary blade, it is possible to proceed to the next manufacturing process without disposing of the stationary blade structure or stopping the manufacturing process. As a result, the manufacturing time can be shortened and excellent economic efficiency can be obtained.

Here, the significant defect means a defect of the minimum size that can be detected in the radiation flaw detection test according to JIS Z 3104 and a defect of a size exceeding the minimum size.

The stationary blade 10 has no defect detected on the surface of the stationary blade 10 in the penetrant inspection according to JIS Z 2343.

In the penetrant inspection test, granular defects and linear cracks of a size that cannot be confirmed by the radiation flaw detection test can be clearly confirmed.

Usually, for example, if a defect is detected at the end of the manufacturing process, the defect is repaired by polishing removal or welding. In addition, repair work may be difficult depending on the site where the defect is detected. In this case, the manufactured stationary blade 10 is discarded. Repairing defects or disposing of the stationary blade 10 at the final stage of the manufacturing process of the stationary blade 10 causes a delay in production and a decrease in economic efficiency.

However, since the stationary blade 10 of the embodiment does not detect a defect on the surface of the stationary blade 10, the above-mentioned defect repair or disposal of the stationary blade 10 does not occur. Therefore, in the manufacturing process of the stationary blade 10, the manufacturing time can be shortened and excellent economic efficiency can be obtained.

As described above, the stationary blade 10 of the present embodiment is a stationary blade in which defects on the inside and the surface are not detected in the radiation flaw detection test and the penetrant inspection test.

Next, the stationary blade row 50 including the stationary blade 10 of the above-described embodiment will be described.

The stationary blade row 50 of the embodiment is used in a corrosive environment in which a working medium containing a corrosive component flows.

As shown in FIG. 4, the stationary blade row 50 includes a diaphragm outer ring 113, a diaphragm inner ring 115, and a stationary blade 10. The stationary blade row 50 is composed of a two-divided structure including an upper half stationary blade row 50a and a lower half stationary blade row 50b. The upper half stationary blade row 50a is located vertically above the central axis O of the turbine rotor 111. The lower half stationary blade row 50b is located vertically below the central axis O of the turbine rotor 111.

The diaphragm outer ring 113 includes an upper half diaphragm outer ring 113a and a lower half diaphragm outer ring 113b. By installing the upper half diaphragm outer ring 113a on the lower half diaphragm outer ring 113b, the annular diaphragm outer ring 113 is formed.

The diaphragm inner ring 115 includes an upper half diaphragm inner ring 115a and a lower half diaphragm inner ring 115b. By installing the upper half diaphragm inner ring 115a on the lower half diaphragm inner ring 115b, the annular diaphragm inner ring 115 is formed.

As shown in FIG. 5, the diaphragm outer ring 113 is formed with a kanhe groove portion 130 for fitting the outer ring fitting portion 30 of the stationary blade 10 in the circumferential direction. The mating groove 130 is formed with a fitting convex portion 131 that fits into the fitting recess 32 of the outer ring fitting portion 30. The fitting convex portion 131 is composed of, for example, a ridge portion that protrudes from the end surface 130a on the upstream side of the mating groove portion 130 to the downstream side in the axial direction over the circumferential direction.

By fitting the outer ring fitting portion 30 of the stationary blade 10 into the kanhe groove portion 130, the stationary blade 10 is supported by the diaphragm outer ring 113.

The support structure of the outer ring fitting portion 30 in the diaphragm outer ring 113 is not limited to this structure. For example, the outer ring fitting portion 30 may be provided with a ridge portion, and the diaphragm outer ring 113 may be provided with a fitting recess for fitting the ridge portion.

As shown in FIG. 5, the inner ring 115 of the diaphragm is formed with a kanhe groove portion 140 for fitting the inner ring fitting portion 40 of the stationary blade 10 in the circumferential direction. The fitting groove portion 140 is formed with a fitting recess 141 that fits into the fitting convex portion 41 of the inner ring fitting portion 40. The fitting recess 141 is composed of a groove portion formed in the central axial direction from the bottom portion of the mating groove portion 140 in the circumferential direction.

By fitting the inner ring fitting portion 40 of the stationary blade 10 into the kanhe groove portion 140, the stationary blade 10 is supported by the diaphragm inner ring 115.

Here, the stationary blade 10 is fitted, for example, while sliding between the upper half diaphragm outer ring 113a and the upper half diaphragm inner ring 115a in the circumferential direction. Then, a plurality of stationary blades 10 are fitted in the circumferential direction to form an upper half stationary blade row 50a.

Similarly, the stationary blade 10 is fitted while sliding in the circumferential direction between, for example, the lower half diaphragm outer ring 113b and the lower half diaphragm inner ring 115b. Then, a plurality of stationary blades 10 are fitted in the circumferential direction to form a lower half stationary blade row 50b.

In the above, when the stationary blade 10 is slid, the upper half diaphragm outer ring 113a and the upper half diaphragm inner ring 115a, and the lower half diaphragm outer ring 113b and the lower half diaphragm inner ring 115b form the outer ring fitting portion 30 of the stationary blade 10. They are arranged with a matable gap.

As described above, the stationary blade row 50 is arranged around the turbine rotor 111 inside the casing 110 in the radial direction.

Here, as shown in FIG. 4, in the upper half stationary blade row 50a, the inner ring fitting portions 40 (fitting convex portions 41) of the stationary blades 10 at both ends in the circumferential direction are respectively above by the fixing pin 150. It is fixed to the inner ring 115a of the half diaphragm. The fixing pin 150 functions as a rod-shaped member.

Here, FIG. 5 shows a state in which the inner ring fitting portion 40 (fitting convex portion 41) of the stationary blade 10 at one end of the upper half stationary blade row 50a is fixed by the fixing pin 150. ing.

As shown in FIG. 5, the upper half diaphragm inner ring 115a and the fitting convex portion 41 are formed with insertion holes 151 and 152 for inserting the fixing pin 150. When the fitting convex portion 41 of the inner ring fitting portion 40 is fitted into the fitting recess 141 of the diaphragm inner ring 115, the insertion hole 151 and the insertion hole 152 are configured to communicate with each other in a straight line in the axial direction. .. The insertion hole 151 and the insertion hole 152 are formed, for example, with the same hole diameter.

The fixing pin 150 is composed of a rod-shaped member. The fixing pin 150 is configured to have a length that penetrates the insertion hole 152 from the inlet 151a of the insertion hole 151. The outer diameter of the fixing pin 150 is set so that the inner ring fitting portion 40 of the stationary blade 10 can be fixed so as not to move when the fixing pin 150 is inserted into the insertion holes 151 and 152. For example, the outer diameter of the fixing pin 150 is configured to be slightly smaller than the hole diameters of the insertion holes 151 and 152.

The fixing pin 150 is made of, for example, the same material as the metal material constituting the inner ring 115 of the diaphragm. The fixing pin 150 is made of, for example, stainless steel such as ASTM standard A182 F91, A182 F6a, A217 C12A, low alloy steel such as ASTM standard A193 B16, and carbon steel such as JIS standard SS400.

In the upper half stationary blade row 50a, the inner ring fitting portion 40 (fitting convex portion 41) of the stationary blade 10 at the other end is fixed to the upper half diaphragm inner ring 115a by the fixing pin 150. This is the same as the configuration in which the inner ring fitting portion 40 (fitting convex portion 41) of the stationary blade 10 at one end thereof is fixed to the upper half diaphragm inner ring 115a by the fixing pin 150.

In the above-mentioned example of pin fixing in the upper half stationary blade row 50a, the fixing points by the fixing pins 150 are two places.

The upper half diaphragm inner ring 115a and the inner ring fitting portion 40 (fitting convex portion 41) of the stationary blade 10 are fixed as follows.

First, as described above, in a state where the required number of stationary blades 10 are fitted between the upper half diaphragm outer ring 113a and the upper half diaphragm inner ring 115a, the inlet 151a of the insertion hole 151 is axially from the upstream side. Insert the fixing pin 150 into. The fixing pin 150 is inserted into the insertion holes 151 at both ends of the upper half diaphragm inner ring 115a.

Then, the fixing pin 150 is inserted in the axial direction, and the fixing pin 150 is passed through the insertion hole 152. The fixing pin 150 is inserted into the insertion holes 151 and 152 by driving the end portion on the upstream side of the fixing pin 150 in the axial direction.

By such pin fixing, the stationary blade 10 (inner ring fitting portion 40) is fixed to the upper half diaphragm inner ring 115a. As a result, for example, even if the upper half stationary blade row 50a is lifted vertically upward with both ends of the upper half stationary blade row 50a vertically downward, the stationary blade 10 does not fall downward.

Here, in the upper half stationary blade row 50a, an example of fixing the inner ring fitting portion 40 (fitting convex portion 41) of the stationary blade 10 at both ends in the circumferential direction to the upper half diaphragm inner ring 115a by the fixing pin 150. Although shown, it is not limited to this configuration.

In the upper half stationary blade row 50a, the fixing points by the fixing pins 150 may be at least two places for fixing the stationary wings 10 at both ends in the circumferential direction, as described above. Further, the number of fixing points by the fixing pin 150 may be, for example, three or more.

For example, in addition to the stationary blades 10 at both ends in the circumferential direction, the stationary blades 10 located at the center (90 degree position) of both ends in the circumferential direction may be fixed to the upper half diaphragm inner ring 115a by the fixing pin 150. In this case, there are three fixing points by the fixing pin 150.

Further, in addition to the stationary blades 10 at both ends in the circumferential direction, for example, each stationary blade 10 at a position 45 degrees from the end portion in the circumferential direction may be fixed to the upper half diaphragm inner ring 115a by a fixing pin 150. In this case, there are four fixing points by the fixing pin 150.

Even in the lower half stationary blade row 50b, even if the inner ring fitting portions 40 (fitting convex portions 41) of the stationary blades 10 at both ends in the circumferential direction are fixed to the lower half diaphragm inner ring 115b by the fixing pin 150. good. Further, in the lower half stationary blade row 50b, the stationary blade 10 located at an arbitrary position in the circumferential direction may be fixed by the fixing pin 150 in addition to the stationary blades 10 at both ends in the circumferential direction.

In the stationary blade row 50 of the present embodiment, the inner ring fitting portion 40 (fitting convex portion 41) of the stationary blade 10 at both ends in the circumferential direction is fixed to the upper half diaphragm inner ring 115a by the fixing pin 150. When assembling the stationary blade row, for example, it is possible to prevent the stationary blade 10 from falling off from between the upper half diaphragm outer ring 113a and the upper half diaphragm inner ring 115a.

Further, by adopting the fixing by the fixing pin 150, in addition to preventing the stationary blade 10 from falling off, it becomes easy to disassemble and reassemble.

Further, for example, by fixing the stationary blade 10 at the end in the circumferential direction to the inner ring 115a of the upper half diaphragm by the fixing pin 150, the outer ring fitting of the stationary blades 10 at both ends in the circumferential direction of the upper half stationary blade row 50a is fitted. The portion 30 and the inner ring fitting portion 40 are maintained in contact with the outer ring fitting portion 30 and the inner ring fitting portion 40 of the stationary blades 10 at both ends in the circumferential direction of the lower half stationary blade row 50b, respectively.

As a result, the working fluid containing the corrosive component flows from the steam passage 116 in the stationary blade row 50 to the contact surface between the end face 130a on the upstream side of the mating groove 130 and the outer ring fitting portion 30, and the mating groove portion of the inner ring 115 of the diaphragm. Leakage between the upstream end surface of 140 and the contact surface between the inner ring fitting portion 40 can be suppressed. Therefore, corrosion of turbine components other than the turbine components constituting the steam passage 116 is suppressed. This enables stable operation of the steam turbine 100 for a long period of time.

Here, when the steam turbine 100 is disassembled after a certain period of operation, the contact surface between the upper half stationary blade row 50a and the lower half stationary blade row 50b in the two-divided stationary blade row 50 may be fixed. be. An excessive load is generated in this fixed portion, and the stationary blade 10 may be deformed by disassembling.

However, by fixing the inner ring fitting portion 40 (fitting convex portion 41) of the wing 10 to the upper half diaphragm inner ring 115a by the fixing pin 150 and integrating the inner ring fitting portion 40, the upper half stationary wing row 50a and the lower half static Even when the contact surface with the blade row 50b is fixed, the deformation of the stationary blade 10 can be avoided.

Further, by setting the number of fixing points by the fixing pins 150 to three or more, the rigidity of the entire stationary blade 10 is increased and the load concentration on the thin blade effective portion 20 is avoided. This makes it possible to easily disassemble the steam turbine 100 and the stationary blade row 50.

Here, the stationary blade 10, that is, the blade effective portion 20, the outer ring fitting portion 30, and the inner ring fitting portion 40 are formed of a Ni-based alloy.

The stationary blade 10 is composed of a Ni-based alloy having a composition component range shown below. The Ni-based alloy constituting the stationary blade 10 of the embodiment is Cr: 20.0 to 22.5, Mo: 12.5-14.5, W: 2.5 to 3.5, Fe in mass%. It contains: 2.0 to 6.0, V: 0.05 to 0.35, and the balance consists of Ni and unavoidable impurities.

Here, the method for manufacturing the stationary blade 10 will be described later, but it is manufactured by casting.

Next, the reason for limiting the range of each composition component in the Ni-based alloy constituting the stationary blade 10 of the above-described embodiment will be described. In the following description,% representing the composition shall be mass% unless otherwise specified.

(1) Cr (chromium)
Cr is effective in improving corrosion resistance. The effect is maximized when the Cr content is 20.0 to 22.5% in the Ni-based alloy constituting the stationary blade 10. If the Cr content is less than 20.0%, the corrosion resistance is inferior. When the Cr content exceeds 22.5%, a bcc-Cr phase or a σ phase is formed to promote embrittlement. Therefore, the Cr content was set to 20.0 to 22.5%.

(2) Mo (molybdenum)
Mo dissolves in the Ni matrix and contributes to the improvement of the strength of the alloy. In the Ni-based alloy constituting the stationary blade 10, Mo is useful as a strengthening factor for the Ni matrix because the crystal grains are coarse and no precipitate constituent element other than the metal element is intentionally added. The effect of strengthening the Ni matrix is maximized when the Mo content is 12.5% or more. When the Mo content exceeds 14.5%, Ni ₄ Mo is generated and embrittlement progresses. Therefore, the Mo content was set to 12.5 to 14.5%.

(3) W (tungsten)
W dissolves in the Ni matrix and contributes to the improvement of the strength of the alloy. In the Ni-based alloy constituting the stationary blade 10, W is useful as a strengthening factor for the Ni matrix because the crystal grains are coarse and no precipitate constituent element other than the metal element is intentionally added. When used in combination with Mo, which has a similar effect, the effect of strengthening the Ni matrix phase is maximized when the W content is 2.5% or more. When the W content exceeds 3.5%, Ni ₄ W is generated and embrittlement proceeds. Therefore, the W content was set to 2.5 to 3.5%.

(4) Fe (iron)
As a raw material for dissolving an alloy, in addition to pure metal elements such as pure chromium and pure nickel, compounds with Fe such as ferromolybdenum and ferrotungsten are also widely used. The content of Fe in the Ni alloy needs to be allowed to some extent. If the Fe content is less than 2.0%, the composition of the dissolved raw material is almost pure metal element, which lowers the economic efficiency. On the other hand, when the Fe content exceeds 6.0%, an intermetallic compound composed of Ni and Fe is formed, which promotes embrittlement. Therefore, the Fe content was set to 2.0 to 6.0%.

(5) V (vanadium)
V, which is solid-solved in the Ni matrix, has no particular effect by itself, but V has a strong affinity for C (carbon) and easily forms carbides. In the Ni-based alloy constituting the stationary blade 10, it was decided to take advantage of this property and suppress the formation of Cr carbides at the grain boundaries that promote stress corrosion cracking. In the Ni-based alloy constituting the stationary blade 10, C is not intentionally added, but is mixed as an unavoidable impurity. By adding V to generate V carbides in the crystal grains, the residual amount of C in the Ni matrix can be eliminated and the formation of Cr carbides precipitated at the crystal grain boundaries can be suppressed. This effect is observed when the V content is 0.05% or more. This effect saturates when the V content exceeds 0.35%. Therefore, the V content was set to 0.05 to 0.35%.

(6) C (carbon), Si (silicon), Mn (manganese), N (nitrogen), P (phosphorus) and S (sulfur)
C, Si, Mn, N, P, and S are classified as unavoidable impurities in the Ni-based alloy constituting the stationary blade 10 of the embodiment. It is desirable that the residual content of these unavoidable impurities be as close to 0% as possible.

Further, among these unavoidable impurities, it is preferable that at least the residual content of Si is suppressed to 0.8% or less. By reducing the residual content of Si to 0.8% or less, the decrease in toughness is suppressed.

Next, a method of manufacturing the stationary blade 10 of the embodiment will be described.

First, the Ni-based alloy material of the composition component constituting the stationary blade 10 is dissolved in the atmosphere (dissolution step).

Then, the melted Ni-based alloy material is poured into a mold formed in the stationary blade 10 corresponding to the shape, and the stationary blade structure is cast and formed in the atmosphere (structure forming step). The stationary wing structure is an integrated structure in which the wing effective portion 20, the outer ring fitting portion 30, and the inner ring fitting portion 40 are integrally configured. The stationary blade structure is cast so as to have a margin of several millimeters with respect to the final shape of the stationary blade 10.

Subsequently, after the melted Ni-based alloy material is solidified, the stationary blade structure is taken out from the mold. Then, a hot isostatic pressing (HIP) treatment is applied to the stationary blade structure. In the following, the hot isotropic pressure pressurization process is referred to as a HIP process. The HIP treatment heats the stationary blade structure at a temperature of 1200 to 1250 ° C. under a pressure of 100 MPa ± 5 MPa and an environment of an inert gas (HIP treatment step). Here, as the inert gas, nitrogen gas, argon gas or the like is used. The HIP processing time is, for example, 3 to 5 hours, although it varies depending on the thickness of the thick portion of the stationary blade structure and the like.

By performing the HIP treatment under the above-mentioned pressure and temperature, it is possible to eliminate the casting defects generated in the stationary blade structure. The Ni-based alloy constituting the stationary blade 10 has the best ductility at a temperature of about 1200 ° C. Therefore, by applying isotropic pressure to the entire stationary blade structure in a state where the stationary blade structure is heated to about 1200 ° C. and compressing the structure, the fine casting defects remaining inside the stationary blade structure disappear.

In the HIP treatment, if the temperature is less than 1200 ° C., the diffusion of the segregated portion is insufficient, and if the temperature exceeds 1250 ° C., damage to the equipment is promoted. Therefore, the temperature of the HIP treatment was set to 1200 to 1250 ° C.

Further, by pressurizing to about 100 MPa at the temperature of this HIP treatment, almost all the defects inherent in the stationary blade structure can be eliminated. In a thick structure such as a stationary blade structure, when the pressure of the HIP processing becomes low, the HIP processing takes time and the stationary blade structure may have defects. Therefore, the pressure of the HIP treatment was set to 100 MPa ± 5 MPa.

Subsequently, the stationary blade structure subjected to the HIP treatment is cooled (cooling step). To cool the stationary wing structure, an inert gas such as nitrogen gas or argon gas is blown onto the stationary wing structure to quench the structure. At this time, it is preferable that the inert gas is ejected at high speed to collide with the stationary blade structure to increase the heat transfer coefficient and rapidly cool. The stationary blade structure is cooled to room temperature, for example.

The cooling rate by blowing the inert gas is preferably faster than the cooling rate by air cooling. The cooling rate here refers to a temperature that decreases per unit time at a predetermined location in the stationary blade structure.

Subsequently, the surplus wall of the cooled stationary blade structure is cut and processed into the stationary blade 10 having the final shape (processing step). The cutting of the surplus is performed, for example, by machining.

The stationary blade 10 is manufactured through the above-mentioned manufacturing process.

The above-mentioned manufacturing process of the stationary blade 10 does not include a step of forming a corrosion-resistant coating layer for preventing corrosion on the surface of the stationary blade 10 that comes into contact with the working medium containing the corrosion component.

The stationary blade 10 of the present embodiment described above is a stationary blade in which defects are not detected inside and on the surface in the radiation flaw detection test and the penetrant flaw detection test. The stationary blade 10 is less prone to corrosion, pitting corrosion, stress corrosion cracking, and the like even in a corroded environment. Further, since the stationary blade 10 has excellent corrosion resistance, it is not necessary to provide a corrosion resistant coating layer on the surface of the stationary blade 10 that comes into contact with the working medium containing a corrosive component.

The stationary blade 10 can be operated more stably for a long period of time than the stationary blade of a conventional geothermal turbine. Therefore, the maintenance cycle and the replacement cycle of the stationary blade row 50 provided with the stationary blade 10 of the present embodiment are longer than those of the stationary blade row of the conventional geothermal turbine. Thereby, by providing the stationary blade 10 and the stationary blade row 50 of the present embodiment, the maintenance cost in the geothermal turbine can be reduced.

Further, the stationary blade 10 is an integrated structure in which the blade effective portion 20, the outer ring fitting portion 30, and the inner ring fitting portion 40 are integrally configured. Therefore, the step of welding the outer ring fitting portion 30 and the inner ring fitting portion 40 to the blade effective portion 20 can be reduced, and problems such as defects and stress corrosion cracking in the welded portion can be avoided.

(Evaluation of strength characteristics and toughness)
Hereinafter, it will be described that the stationary blade 10 of the embodiment is excellent in strength characteristics and toughness.

Table 1 shows the chemical compositions of Samples 1 to 6 used for the evaluation of strength characteristics and toughness. Samples 1 to 3 shown in Table 1 are Ni-based alloys within the chemical composition range of the Ni-based alloys constituting the stationary blade 10 of the embodiment. Sample 4 is a steel whose composition is not within the chemical composition range of the Ni-based alloy constituting the stationary blade 10 of the embodiment, and is a comparative example. Samples 5 to 6 are Ni-based alloys whose compositions are not within the chemical composition range of the Ni-based alloys constituting the stationary blade 10 of the embodiment, and are comparative examples.

The strength characteristics were evaluated by a tensile test and the toughness was evaluated by an impact test.

The test pieces used for each test were prepared as follows.

The materials of Samples 1 to 6 having the chemical compositions shown in Table 1 were each dissolved in the atmosphere in a melting furnace. The melted material was poured into a mold to form a casting.

Subsequently, the castings of Samples 1 to 6 were heat-treated and cooled under the following conditions, respectively.

After casting, the castings of Samples 1 to 3 were subjected to HIP treatment in an argon gas (Ar gas) atmosphere. The HIP treatment was performed under the conditions of a temperature of 1205 ° C., a pressure of 100 MPa, and a treatment time of 4 hours. The castings of Samples 1 to 3 after the HIP treatment were sprayed with Ar gas and rapidly cooled.

The casting of Sample 4 was rolled and molded. The rolled cast was normalized in the air at a temperature of 1090 ° C. for 4 hours. The cast after normalizing was tempered in the air at a temperature of 640 ° C. for 8 hours. Then, the casting of the sample 4 after tempering was furnace-cooled.

The casting of Sample 5 was rolled and molded. The cast after rolling formation was subjected to solution treatment in the air at a temperature of 960 ° C. for 1 hour. The solution-treated casting was aged in the air at a temperature of 621 ° C. for 8 hours. Then, the casting of the sample 5 after the aging treatment was furnace-cooled.

After casting, the casting of Sample 6 was subjected to solution treatment under an Ar gas atmosphere. The solution treatment was carried out under the conditions of a temperature of 1180 ° C., a pressure of atmospheric pressure, and a treatment time of 1 hour. The casting of sample 6 after the solution treatment was sprayed with Ar gas and rapidly cooled.

Then, test pieces of predetermined size for tensile test and impact test were produced from this casting.

The tensile test was carried out in accordance with JIS Z 2241 using a JIS No. 4 test piece. A tensile strength (MPa) at room temperature was obtained by a tensile test.

The impact test was carried out in accordance with JIS Z 2242 using a 2 mm V notch test piece. A shock absorption energy (J) of 20 ° C. was obtained by a shock test.

The results of the tensile test and the impact test are shown in Table 2.

Here, the room temperature tensile strength required for the material constituting the stationary blade in the geothermal turbine is a sufficient value if it is 600 MPa or more. Further, the 20 ° C. shock absorption energy required for the material constituting the stationary blade in the geothermal turbine is a sufficient value if it is 100 J or more.

As shown in Table 2, in Samples 1 to 3, the room temperature tensile strength was 600 MPa or more. Further, in Samples 1 to 3, the shock absorption energy at 20 ° C. was 280 J or more.

On the other hand, in Samples 4 to 6, the shock absorption energy at 20 ° C. was 60 J or less.

From these results, it was shown that Samples 1 to 3 have high toughness while having sufficient strength characteristics necessary for designing a geothermal turbine.

(Evaluation of corrosion resistance)
An exposure test was carried out on the above-mentioned Samples 1 to 6. An exposure test was conducted at a dew point temperature in an actual steam environment with a pH of 3.5 and an average temperature of 160 ° C, including corrosive components such as CO ₂ , H ₂ S, H ₃ BO ₃ , Cl ⁻ , and NH ₄₊ ^. did. In the exposure test, the test piece was left in this actual steam environment for one month.

The results of the exposure test are shown in Table 3.

In the exposure test, total corrosion, corrosion weight loss, pitting corrosion, and stress corrosion cracking were evaluated. Full-scale corrosion, pitting corrosion and stress corrosion cracking were visually observed. In Table 3, when the entire surface corrosion, pitting corrosion, and stress corrosion cracking are visually observed, it is shown as “Yes”, and when it is not visually observed, it is shown as “None”. Further, when the corrosion weight loss occurs, it is shown as "Yes", and when the corrosion weight loss cannot occur, it is shown as "No".

Here, the total corrosion is a uniform corrosion that occurs on the entire surface. Pitting corrosion is, for example, non-uniform local corrosion that progresses inward from pinholes generated on the surface of a material. Stress corrosion cracking is a crack that occurs with corrosion in a stressed portion. Corrosion loss is the mass loss of a test piece from which corrosion products adhering to the surface have been removed after the corrosion test.

In addition, Table 3 also shows the corrosion resistance index (PRE) which is an index of the corrosion resistance in each sample. PRE is calculated by the following equation 1. The larger the value of PRE, the better the material for pitting corrosion.
Cr + 3.3 × (Mo + W / 2) + 16 × N ・ ・ ・ (Equation 1)

As shown in Table 3, in Samples 1 to 3, the PRE exceeds 65. Further, in Samples 1 to 3, none of total corrosion, corrosion weight loss, pitting corrosion, and stress corrosion cracking occurred.

On the other hand, in Samples 4 to 6, PRE is less than 50. In sample 4, total corrosion, corrosion weight loss and pitting corrosion occur. Further, in the sample 5, pitting corrosion and stress corrosion cracking occur. In Sample 6, no total corrosion, corrosion weight loss, pitting corrosion, or stress corrosion cracking occurred, but as described above, the sample 6 does not have the toughness required for the design of the geothermal turbine.

From these results, it was shown that Samples 1 to 3 have excellent corrosion resistance even in an actual steam environment.

(Evaluation of defects)
The stationary blade 10 was manufactured by changing the heat treatment conditions using the samples 1 to 3, and the defects of the stationary blade 10 were evaluated. The process of manufacturing the stationary blade structure by casting under atmospheric pressure is the same as the manufacturing method of the stationary blade 10 described above.

Table 4 shows the conditions of heat treatment and cooling applied to the stationary blade structure when the stationary blades A to F are manufactured.

Here, the stationary blade A, the stationary blade D, and the stationary blade F are composed of a Ni alloy having the chemical composition of the sample 1. The vane B and the vane E are composed of a Ni alloy having the chemical composition of Sample 2. The vane C is composed of a Ni alloy having the chemical composition of Sample 3.

The stationary blade structures of the stationary blade A, the stationary blade B, and the stationary blade C were subjected to HIP treatment under an Ar gas atmosphere at a temperature of 1205 ° C. and a pressure of 100 MPa for 4 hours. As a cooling method, a quenching method by spraying Ar gas was adopted.

The stationary blade structures of the stationary blade D and the stationary blade E were subjected to solution treatment under an Ar gas atmosphere at a temperature of 1205 ° C. and an atmospheric pressure for 1 hour. As a cooling method, a quenching method by spraying Ar gas was adopted.

The stationary blade structure of the stationary blade F was subjected to solution treatment under an Ar gas atmosphere at a temperature of 1205 ° C. and an atmospheric pressure for 1 hour. As a cooling method, a quenching method by spraying Ar gas was adopted. Further, the stationary blade F was subjected to HIP treatment for 4 hours at a temperature of 1205 ° C. and a pressure of 100 MPa under an Ar gas atmosphere after the solution treatment. As a cooling method, a quenching method by spraying Ar gas was adopted.

After cooling the stationary blade structure of each stationary blade, the surplus thickness of the stationary blade structure was cut by machining to process the stationary blade into the final shape.

A radiation flaw detection test according to JIS Z 3104 was carried out for each stationary wing. Radiation flaw detection tests were performed on the outer ring fitting part, inner ring fitting part, and wing effective part of the stationary wing.

Here, the maximum wall thickness of the outer ring fitting portion and the inner ring fitting portion was 80 mm, and the maximum wall thickness of the blade effective portion was 30 mm.

Next, a penetrant inspection according to JIS Z 2343 was carried out on the surface of each stationary blade.

Next, each sample was cut by wire-cut electric discharge machining from the outer ring fitting portion toward the inner ring fitting portion at intervals of 15 mm perpendicular to the blade length direction of the stationary blade. After polishing each cut surface, a penetrant flaw detection test according to JIS Z 2343 was performed on each cut surface.

Further, a Ni alloy casting (referred to as Sample F) having the chemical composition of Sample 1 constituting the static blade F was heat-treated and cooled under the same conditions as the heat treatment and cooling in the stationary blade F in Table 4. This sample F was cast under atmospheric pressure. Specimens for tensile test and impact test were produced from the sample F. Then, the tensile test and the impact test were carried out by the method described above.

The results of the radiation flaw detection test and the penetrant flaw detection test are shown in Table 5.

In Table 5, when a defect is detected, it is indicated as “Yes”, and when a defect is not detected, it is indicated as “None”.

As shown in Table 5, no defects were detected in the radiation flaw detection test and the penetrant inspection test (surface, cross section) in the stationary blade A, the stationary blade B, and the stationary blade C.

On the other hand, in the stationary blade D and the stationary blade E not subjected to the HIP treatment, defects were detected in both the radiation flaw detection test and the penetrant flaw detection test (surface, cross section).

In the radiation flaw detection test, a plurality of defects having a size of about 1.5 to 2 mm, which is the size detectable in this test, were detected in each of the stationary blade D and the stationary blade E.

Further, in the penetrant inspection on the surface, a plurality of defects were confirmed in each of the stationary blade D and the stationary blade E. The defects in the penetrant inspection on the surface were located at different sites from the defects confirmed in the radiation flaw detection test, and were minute ones of less than 0.5 mm.

The penetrant inspection on the cross section identified multiple defects, including those found in the radiation flaw detection test.

No defects were detected in the stationary blade F in either the radiation flaw detection test or the penetrant flaw detection test (surface, cross section). However, the normal temperature tensile strength of the sample F was 500 MPa, which was much lower than the normal temperature tensile strength of 600 MPa required for the material constituting the stationary blade. The 20 ° C. shock absorption energy in the sample F was 330 J.

From these results, by applying the HIP treatment to the stationary blade structure having the chemical composition constituting the stationary blade 10 of the present embodiment, the strength characteristics required for the stationary blade are obtained, and both the inside and the surface thereof are formed. It was also shown that it can provide a stationary wing with no defects.

According to the embodiment described above, it has excellent corrosion resistance and enables stable operation for a long period of time in a corrosive environment.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

10 ... stationary blade, 20 ... blade effective portion, 20a ... leading edge, 20b ... trailing edge, 30 ... outer ring fitting portion, 31, 130a ... end face, 32, 141 ... fitting recess, 40 ... inner ring fitting portion, 41. , 131 ... fitting convex, 42 ... bottom surface, 50 ... stationary blade row, 50a ... upper half stationary blade row, 50b ... lower half stationary blade row, 51 ... moving blade row, 100 ... steam turbine, 110 ... casing , 111 ... Turbine rotor, 111a ... Rotor wheel, 112 ... Moving blade, 113 ... Diaphragm outer ring, 113a ... Upper half diaphragm outer ring, 113b ... Lower half diaphragm outer ring, 114 ... Circular extension, 115 ... Diaphragm inner ring, 115a ... upper half diaphragm inner ring, 115b ... lower half diaphragm inner ring, 116 ... steam passage, 117 ... ground seal part, 117a, 118a ... seal fin, 118 ... seal part, 120 ... steam introduction pipe, 130, 140 ... Groove, 150 ... fixing pin, 151, 152 ... insertion hole, 151a ... entrance.

Claims (11)

A highly corrosion-resistant static blade that is used in a corrosive environment in which a working medium containing corrosive components flows and is supported between the outer ring of the diaphragm and the inner ring of the diaphragm of a geothermal turbine.
Wing effective part and
An outer ring fitting portion formed at one end of the blade effective portion and fitted to the diaphragm outer ring, and an outer ring fitting portion.
It is provided with an inner ring fitting portion formed at the other end of the blade effective portion and fitted to the diaphragm inner ring.
A highly corrosion-resistant static blade of a geothermal turbine, wherein the blade effective portion, the outer ring fitting portion, and the inner ring fitting portion are integrally formed of a Ni-based alloy. The Ni-based alloy
By mass%, Cr: 20.0 to 22.5, Mo: 12.5-14.5, W: 2.5 to 3.5, Fe: 2.0 to 6.0, V: 0.05 to The highly corrosion-resistant static blade of the geothermal turbine according to claim 1, which contains 0.35 and the balance is composed of Ni and unavoidable impurities. The highly corrosion-resistant static blade of the geothermal turbine according to claim 1 or 2, wherein the surface of the highly corrosion-resistant static blade that comes into contact with the working medium containing a corrosion component is not provided with a corrosion-resistant coating layer for preventing corrosion. .. The highly corrosion-resistant static blade of the geothermal turbine according to any one of claims 1 to 3, wherein no defect is detected inside the highly corrosion-resistant static blade in a radiation flaw detection test according to JIS Z 3104. The highly corrosion-resistant static blade of the geothermal turbine according to any one of claims 1 to 4, wherein no defect is detected on the surface of the highly corrosion-resistant static blade in the penetrant inspection according to JIS Z 2343. A geothermal turbine vane row used in a corrosive environment in which a working medium containing corrosive components flows.
With the outer ring of the diaphragm,
The inner ring of the diaphragm provided inside the outer ring of the diaphragm and the inner ring of the diaphragm.
The highly corrosion-resistant static blade of the geothermal turbine according to any one of claims 1 to 5, which is provided between the outer diaphragm ring and the inner diaphragm ring in a plurality of circumferential directions.
A geothermal turbine vane row characterized by comprising an inner ring fitting portion of the highly corrosion resistant static blade fitted to the diaphragm inner ring and a rod-shaped member for fixing the diaphragm inner ring. The stationary blade row is composed of a two-divided structure consisting of an upper half stationary blade row and a lower half stationary blade row.
The sixth aspect of claim 6, wherein in the upper half stationary blade row, the inner ring fitting portions of the highly corrosion-resistant static blade at both ends in the circumferential direction are fixed to the inner ring of the diaphragm by the rod-shaped member, respectively. A row of stationary blades of a geothermal turbine. A method for manufacturing a highly corrosion-resistant static blade of a geothermal turbine used in a corrosive environment in which a working medium containing a corrosive component flows.
By mass%, Cr: 20.0 to 22.5, Mo: 12.5-14.5, W: 2.5 to 3.5, Fe: 2.0 to 6.0, V: 0.05 to A melting step in which a Ni-based alloy material containing 0.35 and the balance consisting of Ni and unavoidable impurities is dissolved in the atmosphere.
A structure forming step of pouring the melted Ni-based alloy material into a mold having a predetermined shape in the atmosphere to form a stationary blade structure.
A hot isotropic pressurization step of hot isotropic pressurization treatment of the stationary blade structure at a temperature of 1200 to 1250 ° C. under a pressure of 100 MPa ± 5 MPa and an environment of an inert gas.
A cooling step for cooling the stationary blade structure subjected to the hot isotropic pressure pressurization treatment, and
A method for manufacturing a highly corrosion-resistant static blade of a geothermal turbine, which comprises a processing step of cutting the surplus wall of the cooled stationary blade structure into a highly corrosion-resistant static blade. In the method for manufacturing a highly corrosion-resistant static blade of a geothermal turbine,
The high corrosion resistance of the geothermal turbine according to claim 8, wherein the step of forming a corrosion resistant coating layer for preventing corrosion is not included on the surface of the highly corrosion resistant blade that comes into contact with the working medium containing a corrosion component. How to make wings. The highly corrosion-resistant static blade of the geothermal turbine according to claim 8 or 9, wherein in the radiation flaw detection test according to JIS Z 3104, no defect is detected inside the highly corrosion-resistant static blade processed in the processing step. Production method. The geothermal turbine according to any one of claims 8 to 10, wherein in the penetrant inspection according to JIS Z 2343, there is no detection of defects on the surface of the highly corrosion-resistant static blade machined in the machining step. A method for manufacturing a highly corrosion-resistant static wing.

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