JP2019011501A - Method for producing nozzle plate of steam turbine - Google Patents

Abstract

To achieve high production efficiency and cost reduction.SOLUTION: A method for producing a nozzle plate of a steam turbine according to one embodiment includes a preparation step and a casting step. In the preparation step, a metal material formed by electroslag remelting is prepared. In the casting step, a nozzle plate is formed by casting using the metal material. Here, the metal material has a composition comprising, in mass%, C: 0.10-0.15, Si: 0.60 or less, Mn: 0.60 or less, Ni: 0.60 or less, Cr: 12.0-14.0 with the balance being Fe and inevitable impurities.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a method for manufacturing a nozzle plate of a steam turbine.

  In a steam turbine, a stationary blade cascade is constituted by, for example, a nozzle diaphragm in which a plurality of nozzle plates (stationary blades) are arranged between a diaphragm outer ring and a diaphragm inner ring. In the nozzle diaphragm, the nozzle plate is fixed to each of the diaphragm outer ring and the diaphragm inner ring.

Patent No. 4040922 Japanese Patent No. 3106130 JP 2010-242221 A JP 2000-297606 A Japanese Patent Laid-Open No. 5-125471 Japanese Patent Laid-Open No. 2007-092122

  The nozzle plate of a steam turbine is generally formed by cutting a square bar formed by forging or rolling. For this reason, when producing a nozzle plate as mentioned above, much time is required. Further, since the difference between the weight of the square material as the raw material and the weight of the nozzle plate as the final product is large, the yield is low. Under such circumstances, the production of the nozzle plate is low in manufacturing efficiency, and cost reduction is not easy. In other words, it is not reasonable from the viewpoint of economy.

  Therefore, the problem to be solved by the present invention is to provide a method for manufacturing a nozzle plate of a steam turbine that has high manufacturing efficiency and can easily realize cost reduction.

  The manufacturing method of the nozzle plate of the steam turbine which concerns on embodiment has a preparatory process and a casting process. In the preparation step, a metal material formed by an electroslag remelting method is prepared. In the casting process, a nozzle plate is formed by casting using the metal material. Here, the composition of the metal material is mass%, C: 0.10 to 0.15, Si: 0.60 or less, Mn: 0.60 or less, Ni: 0.60 or less, Cr: 12.0 to 14.0 is contained with the balance being Fe and inevitable impurities.

FIG. 1 schematically shows a steam turbine including a stationary blade cascade composed of nozzle plates (static blades) of the present embodiment.

  First, the nozzle plates (M1) to (M5) of the embodiment will be described. The nozzle plates (M1) to (M5) of the embodiment are in the ranges shown below for each component.

  The composition of the nozzle plate (M1) is mass%, C: 0.10 to 0.15, Si: 0.60 or less, Mn: 0.60 or less, Ni: 0.60 or less, Cr: 12.0 to 14.0, N: 0.01 to 0.03, with the balance being Fe and inevitable impurities.

  The composition of the nozzle plate (M2) is mass%, C: 0.10 to 0.15, Si: 0.60 or less, Mn: 0.40 to 0.60, Ni: 0.60 or less, Cr: 10 0.0 to 11.5, Mo: 0.80 to 1.10, V: 0.15 to 0.25, Nb: 0.05 to 0.20, N: 0.01 to 0.03, The balance consists of Fe and inevitable impurities.

  The composition of the nozzle plate (M3) is mass%, C: 0.10 to 0.15, Si: 0.60 or less, Mn: 0.40 to 0.60, Ni: 0.60 or less, Cr: 9 .2 to 10.2, Mo: 0.80 to 1.10, V: 0.15 to 0.25, W: 0.80 to 1.10, Nb: 0.05 to 0.10, N: 0 0.01 to 0.03, with the balance being Fe and inevitable impurities.

  The composition of the nozzle plate (M4) is mass%, C: 0.10 to 0.15, Si: 0.30 or less, Mn: 0.40 to 0.60, Ni: 0.30 or less, Cr: 9 .0 to 10.5, Mo: 0.50 to 0.80, V: 0.15 to 0.25, W: 1.60 to 1.90, Nb: 0.015 to 0.025, Co: 1 0.0 to 3.0, N: 0.01 to 0.03, with the balance being Fe and inevitable impurities.

  The nozzle plate (M5) is C: 0.10 to 0.15, Si: 0.30 or less, Mn: 0.40 to 0.60, Ni: 0.30 or less, Cr: 9.0 to 10.5 , Mo: 0.50 to 0.80, V: 0.15 to 0.25, W: 1.60 to 1.90, Nb: 0.015 to 0.025, Co: 1.0 to 3.0 , B: 0.005 to 0.009, N: 0.01 to 0.03, with the balance being Fe and inevitable impurities.

  The nozzle plates (M1) to (M5) of the embodiment have almost no anisotropy, have uniform mechanical properties, and are excellent in economic efficiency. In the above, “C: 0.11 to 0.15” or the like indicates that the C element content is 0.11% by mass or more and 0.15% by mass or less. “Si: 0.60 or less” or the like indicates that the Si element content is 0.60 mass% or less, and includes the case where the Si element content is zero (the same applies hereinafter).

  The reason why the ratio (content ratio) contained in each component in the nozzle plates (M1) to (M5) of the embodiment is set in the above range will be described.

C (carbon) [(M1) to (M5) ... 0.10 to 0.15]
C is a component necessary for ensuring hardenability and hot water flow during casting, and is an indispensable component as a constituent element constituting the carbide contributing to precipitation strengthening. In the nozzle plates (M1) to (M5) of the embodiment, when the C content is less than the lower limit of the above range, the above-described functions and effects are reduced. When the C content exceeds the upper limit of the above range, the agglomeration of the carbide is promoted and the segregation tendency at the time of casting is increased, so that weldability including repair is lowered. For this reason, in the nozzle plates (M1) to (M5) of the embodiment, the C content is set in the above range.

Si (silicon) [(M1), (M2), (M3) ... 0.60 or less, (M4), (M5) ... 0.30 or less]
Si is a component that is useful as a deoxidizer and improves the flow of molten metal. In the nozzle plates (M1), (M2), and (M3) of the embodiment, when the Si content exceeds the upper limit of the above range, toughness reduction and embrittlement are significantly promoted. In addition, since the nozzle plates (M4) and (M5) of the embodiment contain a large amount of ferrite-forming elements, the stabilization of the structure is realized by making the Si content not more than the upper limit of the above range. Can do. For this reason, in the nozzle plates (M1) to (M5) of the embodiment, the Si content is set in the above range.

Mn (manganese) [(M1) ... 0.60 or less, (M2) to (M5) ... 0.40 to 0.60]
Mn is a component useful as a desulfurization agent. In the nozzle plates (M1) to (M5) of the embodiment, when the Mn content exceeds the upper limit of the above range, the creep strength is reduced. In the nozzle plates (M2) to (M5) of the embodiment, since the ferrite forming element is contained, the stabilization of the structure can be realized by setting the content of Mn to the lower limit value or more of the above range. When the Mn content is less than the lower limit of the above range, the desulfurization effect is not sufficiently exhibited. For this reason, in the nozzle plates (M1) to (M5) of the embodiment, the Mn content is set in the above range.

Ni (nickel) [(M1), (M2), (M3) ... 0.60 or less, (M4), (M5) ... 0.30 or less]
Ni is a component that improves hardenability and toughness and has an effect of suppressing the formation of ferrite. In the nozzle plates (M1), (M2), and (M3) of the embodiment, when the Ni content exceeds the upper limit of the above range, the creep strength is reduced. In the nozzle plates (M4) and (M5) of the embodiment, a Co (cobalt) component is included, and by making the Ni content equal to or higher than the lower limit of the above range, a decrease in creep strength is suppressed, and the structure Stabilization and excellent high temperature characteristics can be realized. For this reason, in the nozzle plates (M1) to (M5) of the embodiment, the Ni content is set in the above range.

Cr (chromium) [(M1) ... Cr: 12.0 to 14.0, (M2) ... Cr: 10.0 to 11.5, (M3) ... Cr: 9.2 to 10.2, (M4 ), (M5) ... Cr: 9.0 to 10.5]
Cr is an effective component for improving oxidation resistance and corrosion resistance, and is an indispensable component as a constituent element of carbonitride contributing to precipitation strengthening. In the nozzle plates (M1) to (M5) of the embodiment, when the Cr content is less than the lower limit of the above range, a precipitate (carbonitride) that precipitates with Cr as a constituent element in the tempering heat treatment is performed. Therefore, sufficient stability at high temperatures may not be ensured. When the Cr content exceeds the upper limit of the above range, the amount of delta ferrite produced increases. In the nozzle plates (M1) to (M5) of the embodiment, the balance of characteristics is adjusted by controlling the Cr content ratio according to the content ratio of the ferrite forming elements (Mo, W, Nb, V, etc.). doing.

Mo (molybdenum) [(M1) ... 0, (M2), (M3) ... 0.80 to 1.10, (M4), (M5) ... 0.50 to 0.80]
Mo is a component that contributes to solid solution strengthening, and is a constituent element of carbonitride and a component that contributes to precipitation strengthening. Mo is a constituent element of a precipitate that is deposited when a long-time heat treatment is performed in a high-temperature environment. In the nozzle plates (M2) to (M5) of the embodiment, when the Mo content is less than the lower limit of the above range, it is difficult to keep the amount of Mo contributing to solid solution strengthening high for a long time. . When the Mo content exceeds the upper limit of the above range, toughness is reduced and the formation of ferrite is promoted. For this reason, in the nozzle plates (M2) to (M5) of the embodiment, the Mo content is in the above range. The nozzle plates (M4) and (M5) of the embodiment have a large W (tungsten) component content, so that the nozzle plates (M2) and (M2) can be used to maintain high temperature characteristics and suppress the formation of ferrite. The content ratio of Mo is smaller than in the case of M3).

V (Vanadium) [(M1) ... 0, (M2)-(M5) ... 0.15-0.25]
V is a component contributing to solid solution strengthening and a component contributing to the formation of fine carbonitrides. In the nozzle plates (M2) to (M5) of the embodiment, when the V content is less than the lower limit of the above range, the above-described functions and effects are not sufficient. When the V content exceeds the upper limit of the above range, toughness is reduced. For this reason, in the nozzle plates (M2) to (M5) of the embodiment, the V content is in the above range.

W (tungsten) [(M1), (M2) ... 0, (M3) ... 0.80 to 1.10, (M4), (M5) ... 1.60 to 1.90]
W is a component that contributes to solid solution strengthening and is a constituent element of carbonitride and a component that contributes to precipitation strengthening. W can remarkably enhance the high-temperature stability of the precipitate, particularly when added in combination with Mo. W becomes a constituent element of precipitates when long-time heat treatment is performed in a high-temperature environment. In the nozzle plates (M3), (M4), and (M5) of the embodiment, when the W content is less than the lower limit of the above range, the amount of W contributing to solid solution strengthening is maintained high for a long time. Becomes difficult. When the W content exceeds the upper limit of the above range, toughness decreases and the formation of ferrite is promoted. For this reason, in the nozzle plates (M3), (M4), and (M5) of the embodiment, the W content is within the above range. In the nozzle plates (M4) and (M5), since the W content is larger than that in the nozzle plate (M3), it is possible to realize better high temperature characteristics, as described above. In order to suppress the formation of ferrite, the Mo content is smaller than that of the nozzle plate (M3).

Nb (niobium) [(M1) ... 0, (M2) ... 0.05-0.20, (M3) ... 0.05-0.10, (M4), (M5) ... 0.015-0. 025]
Nb is a component that contributes to solid solution strengthening and contributes to the formation of fine carbonitrides. In the nozzle plates (M2) to (M5) of the embodiment, when the Nb content is less than the lower limit of the above range, the above-described functions and effects are not sufficient. When the Nb content exceeds the upper limit of the above range, the amount of coarse Nb carbonitrides generated increases. For this reason, in the nozzle plates (M2) to (M5) of the embodiment, the Nb content is in the above range. In the nozzle plates (M4) and (M5), the content ratio of W is large, and the amount of coarse Nb carbonitride is easily increased. Therefore, the Nb component is higher than that in the nozzle plates (M2) and (M3). The content ratio of is small.

Co (cobalt) [(M1), (M2), (M3) ... 0, (M4), (M5) ... 1.0-3.0]
Co is a component that contributes to the effect of suppressing the formation of ferrite. In the nozzle plates (M4) and (M5) of the embodiment, when the Co content is less than the lower limit of the above range, the above-described functions and effects are not sufficient. When the Co content exceeds the upper limit of the above range, the precipitation of intermetallic compounds is promoted, and the creep strength decreases. For this reason, in the nozzle plates (M4) and (M5) of the embodiment, the Co content is within the above range.

N (nitrogen) [(M1) to (M5) ... 0.01 to 0.03]
N is a component that contributes to precipitation strengthening by forming nitrides or carbonitrides. Further, N remaining in the matrix contributes to solid solution strengthening. For example, N is dissolved and absorbed in the nozzle plate when casting is performed in the atmosphere. In the nozzle plates (M1) to (M5) of the embodiment, when the N content is less than the lower limit of the above range, the amount of carbonitride produced by the tempering heat treatment is reduced, which is sufficient. Disappear. When the N content exceeds the upper limit of the above range, the coarsening of the nitride is promoted and the precipitation strengthening action is reduced. For this reason, in the nozzle plates (M1) to (M5) of the embodiment, the N content is in the above range.

-B (boron) [(M1)-(M4) ... 0, (M5) ... 0.005-0.009]
B is a component that increases the deformation resistance near the grain boundary and contributes to the improvement of the high temperature creep strength.
In the nozzle plate (M5) of the embodiment, when the B content is less than the lower limit of the above range, the high temperature creep strength is not sufficiently improved. If the B content exceeds the upper limit of the above range, cracking may occur during welding. For this reason, in the nozzle plate (M5) of the embodiment, the B content is within the above range.

  Hereinafter, in the embodiment, a method for manufacturing the nozzle plates (M1) to (M5) will be described.

  In the present embodiment, first, a preparation process for preparing a metal material formed by an electroslag remelting method is performed. Here, the composition of the metal material formed by the electroslag remelting method is mass%, C: 0.10 to 0.15, Si: 0.60 or less, Mn: 0.60 or less, Ni: 0.00. 60 or less, Cr: 12.0 to 14.0, with the balance being Fe and inevitable impurities. In the electroslag remelting method, the consumable electrode is immersed in the molten slag and energized, the consumable electrode is remelted by the Joule heat of the slag, and the molten steel droplets that have passed through the molten slag are stacked in a water-cooled mold. By solidifying, an ingot that is a metal material is obtained.

  Next, the casting process which forms nozzle plates (M1) to (M5) by casting is performed using the metal material prepared in the preparation process. Here, the metal material formed by the electroslag remelting method is melted again. At this time, as needed, a metal component is added so that it may become each component of nozzle plate (M1)-(M5), and a molten metal is formed by melting. And nozzle plates (M1) to (M5) are formed by casting using the molten metal.

  In the present embodiment, for example, the nozzle plates (M1) to (M5) are formed by casting in the atmosphere by a precision casting method. Specifically, a prototype is formed in the shape of a nozzle plate with wax. Next, the periphery of the original mold is covered with cast sand and hardened, and then the wax is dissolved and removed to produce a sand mold. Next, after pouring a molten metal in which each component constituting the nozzle plate is poured into a sand mold, the nozzle plates (M1) to (M5), which are castings (cast steel), are formed.

  Thereafter, tempering heat treatment is performed on the nozzle plates (M1) to (M5). Here, annealing, normalizing, quenching (cooling), and tempering are sequentially performed as the tempering heat treatment. Finally, the nozzle plates (M1) to (M5) are completed by finishing.

  As described above, in the preparation step of the present embodiment, a metal material formed by the electroslag remelting method is prepared. For this reason, the nozzle plates (M1) to (M5) have a low impurity content and high homogeneity. That is, in this embodiment, since scrap is not used, it is not necessary to analyze the content ratio of each component element and the content ratio of impurities contained in the scrap at the time of melting and adjust by refining or the like. Since a metal material manufactured by melting on a scale exceeding several tens of tons is used, the nozzle plates (M1) to (M5), which are cast products, are finally manufactured with stable quality. Moreover, in this embodiment, since the composition of the metal material formed by the electroslag remelting method is the above content ratio, the nozzle plates (M1) to (M5) can be efficiently manufactured. Thus, the manufacturing method of the nozzle plate according to the present embodiment has high manufacturing efficiency and can easily realize cost reduction. In addition, the reason for making the above-mentioned content ratio about the composition of the metal material formed by the electroslag remelting method is that the metal material formed by the electroslag remelting method is the basic composition of the nozzle plates (M1) to (M5). Therefore, nozzle plates (M1) to (M5) can be easily formed by adding reinforcing elements such as Mo, V, W, and Nb and diluting the Cr amount. This is because it becomes possible to do this.

  Furthermore, as described above, in the casting process of the present embodiment, the nozzle plate is manufactured by a precision casting method, so that the manufacturing period can be shortened. For example, when a nozzle plate is manufactured by cutting a square bar formed by forging or rolling, a manufacturing period of 7 to 9 months is required. On the other hand, when the nozzle plate is produced by the precision casting method, the production period is 2 to 3 months, and the production period can be effectively shortened.

  Hereinafter, in the present embodiment, a steam turbine including a stationary blade cascade composed of the nozzle plate (static blade) will be described with reference to FIG. FIG. 1 shows a cross section along a vertical plane (yz plane).

  As shown in FIG. 1, the steam turbine 1 is a rotating machine, and is configured such that a turbine rotor 22 rotates when steam is supplied as a working fluid. Here, the steam turbine 1 is an axial turbine, and the steam flows with the horizontal direction y along the rotation axis AX of the turbine rotor 22 as the flow direction. The steam turbine 1 is a multistage type, in which turbine stages composed of moving blades 21 and stationary blades 25 are arranged in a plurality of stages in the axial direction along the rotation axis AX, and the steam is in each of the plurality of turbine stages. Do the job. As a result, the turbine rotor 22 rotates in the steam turbine 1. Below, the detail of each part which comprises the steam turbine 1 is demonstrated.

  The casing 20 accommodates the turbine rotor 22 therein. One end of the turbine rotor 22 is connected to a generator (not shown), and the generator (not shown) is driven by the rotation of the turbine rotor 22 to generate power. The turbine rotor 22 is provided with a plurality of rotor disks 221 on the outer peripheral surface. A rotor blade 21 is installed on the outer peripheral surface of a rotor disk 221 provided in the turbine rotor 22. A plurality of moving blades 21 are arranged in the circumferential direction R (rotational direction) of the turbine rotor 22 so as to surround the outer peripheral surface of the turbine rotor 22, and constitute a moving blade cascade. The moving blade cascade has a plurality of stages, and each of the plurality of moving blade cascades is arranged along the rotation axis AX of the turbine rotor 22.

  A nozzle diaphragm 10 is installed inside the casing 20. The nozzle diaphragm 10 includes a diaphragm outer ring 23, a diaphragm inner ring 24, and a stationary blade 25. In the nozzle diaphragm 10, the diaphragm outer ring 23 is installed on the inner peripheral surface of the casing 20. The diaphragm inner ring 24 is installed inside the diaphragm outer ring 23 and spaced from the diaphragm outer ring 23. A plurality of stationary blades 25 are installed between the diaphragm outer ring 23 and the diaphragm inner ring 24.

  Here, the plurality of stationary blades 25 are arranged at intervals in the circumferential direction R so as to surround the outer peripheral surface of the turbine rotor 22, and constitute a stationary blade cascade. Like the moving blade cascade, the stationary blade cascade is provided in a plurality of stages, and the multiple stages of stationary blade cascades are arranged along the rotation axis AX of the turbine rotor 22.

  In the steam turbine 1, a steam inlet pipe 28 passes through the inlet of the casing 20, and steam is introduced into the casing 20 as a working fluid via the steam inlet pipe 28.

  In the present embodiment, the stationary blade 25 is the nozzle plate described above, and is formed using a nozzle plate corresponding to the operating temperature.

  In addition to arranging a nozzle plate as the stationary blade 25 between the diaphragm outer ring 23 and the diaphragm inner ring 24, a plurality of nozzle plates may be arranged in the circumferential direction R as the stationary blade 25 in the casing 20 (turbine casing). Good.

  Hereinafter, Examples and Comparative Examples of the nozzle plate described above will be described using Tables 1 to 4.

  In Tables 1 to 4, P1 to P14 are examples, and C1 to C8 are comparative examples. Here, with respect to the nozzle element (M1) that does not contain a reinforcing element component (a ferrite forming element other than Cr element in the composition), the examples are P7 to P9, and the comparative examples are C1 and C2 (nozzle plate (M1 ) Is composed of C, Si, Mn, Ni, Cr, N, Fe, and inevitable impurities) For the nozzle plate (M2) that does not include the W (tungsten) component, the examples are P4 to P6. The comparative examples are C3 and C4 (the nozzle plate (M2) is made of C, Si, Mn, Ni, Cr, Mo, V, Nb, N, Fe, and inevitable impurities). Regarding the nozzle plate (M3) containing the (tungsten) component, the examples are P1 to P3, and the comparative examples are C1 and C2 (the nozzle plate (M3) includes C, Si, Mn, Ni, Cr, Mo, V, W, Nb, N, Fe For the nozzle plate (M4) containing a Co (cobalt) component in the composition, the examples are P10 to P12, and the comparative example is C7 (nozzle plate (M4) C, Si, Mn, Ni, Cr, Mo, V, W, Nb, Co, N, Fe, and inevitable impurities) Nozzle containing in its composition a Co (cobalt) component and a boron (B) component Regarding the plate (M5), the examples are P13 and P14, and the comparative examples are C6 and C8 (the nozzle plate (M5) is C, Si, Mn, Ni, Cr, Mo, V, W, Nb. , Co, B, N, Fe, and inevitable impurities).

[Preparation of nozzle plate]
First, in order to produce the nozzle plate of each example, a metal material formed by an electroslag remelting method was prepared. Here, a cylindrical round bar having the components shown in Table 1 and having a diameter of 100 mm was prepared as a metal material.

  Next, the nozzle plate of each example was formed by casting using the prepared metal material. Here, the metal material formed by the electroslag remelting method was melted again. At this time, as shown in Table 2, the metal component was added and dissolved as necessary so as to be a component of the nozzle plate of each example. And the casting of a nozzle plate shape was produced by casting in air | atmosphere. In Table 2, the indication of “<0.01” indicates that it is less than the detection limit of the component analysis, and indicates that it exceeds 0.00 mass% and is less than 0.01 mass%. .

  Next, a tempering heat treatment was performed on the nozzle plate-shaped casting. Here, the nozzle plate of each example was produced by performing annealing, normalization, quenching, and tempering sequentially as the tempering heat treatment. Annealing, normalizing, quenching, and tempering were performed under the conditions shown in Table 3. The nozzle plate of each example was produced so that the tensile strength at room temperature was about 700 MPa.

[test]
Table 4 shows the results of the tests performed on the nozzle plate of each example.

  As shown in Table 4, the tensile strength at 500 ° C. (JIS Z 2241) and the 100,000-hour creep rupture strength at 550 ° C. (JIS Z 2271) were determined for the nozzle plates of each example. Here, a tensile test was performed at 500 ° C. using a JIS No. 4 test piece. Thus, the tensile strength at 500 ° C. was measured, and “100,000 hours creep rupture strength at 550 ° C.” was calculated from the measurement result of the creep rupture strength.

As shown in Table 4, the “welding” test was performed on the nozzle plate of each example. The “welding” test was performed according to the following procedure. The tempered nozzle plate was processed into a flat plate having a thickness of 10 mm. Then, after preheating the flat plate to 250 ° C., a weld bead was applied to the flat plate using a 9% Cr welding rod in a gas shield environment in which Ar gas and CO ₂ gas were mixed. And the presence or absence of generation | occurrence | production of a crack was confirmed about the vicinity of the welding part among the flat plates. In Table 4, the case where no crack occurs in the weld during welding is indicated by “◯”, and the case where a crack occurs in the weld during welding is indicated by “x”.

  When the test results are compared between P1 to P3 and C1 and C2, the “tensile strength at 500 ° C.” is equivalent between the two. However, “100,000 hour creep rupture strength” is higher in P1 to P3 than in C1. In “welding”, P1 to P3 had no cracks in the welded part, but C2 had cracks in the welded part. Unlike the case of C1 and C2, the content rate of each component which comprises P1-P3 is in the range of the content rate of each component which comprises the above-mentioned nozzle plate (M3). For this reason, P1-P3 is equipped with the outstanding mechanical characteristic as mentioned above.

  When test results are compared between P4 to P6 and C3 and C4, “tensile strength at 500 ° C.” is higher in P4 to P6 than in C3 and C4. Similarly, “100,000 hours creep rupture strength” is higher for P4 to P6 than for C3 and C4. In “welding construction”, cracks occurred in the welded part in P4 to P6, but cracked in the welded part in C3. Unlike the case of C3 and C4, the content rate of each component which comprises P4-P6 is in the range of the content rate of each component which comprises the above-mentioned nozzle plate (M2). Therefore, P4 to P6 have excellent mechanical properties as described above.

  When the test results are compared between P7 to P9 and C5, “tensile strength at 500 ° C.” is higher in P7 to P9 than in C5. Similarly, “100,000 hours creep rupture strength” is higher for P4 to P6 than for C5. In “welding construction”, P7 to P9 are not cracked in the welded portion. Unlike the case of C5, the content rate of each component which comprises P7-P9 is in the range of the content rate of each component which comprises the above-mentioned nozzle plate (M1). For this reason, P7-P9 is equipped with the outstanding mechanical characteristic as mentioned above.

  When the test results are compared between P10 to P12 and C7, the “tensile strength at 500 ° C.” is similar to each other, but the “100,000 hour creep rupture strength” is higher for P10 to P12 than for C7. Is also expensive. In “welding”, P10 to P12 are not cracked in the welded portion. Unlike the case of C7, the content ratio of each component constituting P10 to P12 is within the range of the content ratio of each component constituting the nozzle plate (M4). Therefore, P10 to P12 have excellent mechanical properties as described above.

  When test results are compared between P13 and P14 and C6 and C8, “tensile strength at 500 ° C.” and “100,000 hours creep rupture strength” are the same. However, in “welding work”, P13 and P14 have no crack in the welded portion, but C6 and C8 have a crack in the welded portion. Unlike the case of C6 and C8, the content rate of each component which comprises P13 and P14 is in the range of the content rate of each component which comprises the above-mentioned nozzle plate (M5). Therefore, P13 and P14 have excellent mechanical characteristics as described above.

  From the above results, it can be seen that the nozzle plates (M1) to (M5) have excellent mechanical properties. That is, in the nozzle plates (M1) to (M5), “tensile strength at 500 ° C.” and “100,000 hours creep rupture strength” are sufficiently high, and cracks do not occur in the welded part in “welding operation”. I understand that.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 ... Steam turbine, 10 ... Nozzle diaphragm, 20 ... Casing, 21 ... Moving blade, 22 ... Turbine rotor, 221 ... Rotor disc, 23 ... Diaphragm outer ring, 24 ... Diaphragm inner ring, 25 ... Stator blade (nozzle plate), 28 ... Steam inlet pipe, AX ... Rotating shaft

Claims (6)

A preparation step of preparing a metal material formed by an electroslag remelting method;
Forming a steam turbine nozzle plate by casting using the metal material, and
The composition of the metal material is mass%,
C: 0.10 to 0.15,
Si: 0.60 or less,
Mn: 0.60 or less,
Ni: 0.60 or less,
Cr: 12.0 to 14.0
Containing
The balance consists of Fe and inevitable impurities,
A method for manufacturing a nozzle plate of a steam turbine. The composition of the nozzle plate is mass%,
C: 0.10 to 0.15,
Si: 0.60 or less,
Mn: 0.60 or less,
Ni: 0.60 or less,
Cr: 12.0 to 14.0,
N: 0.01-0.03
Containing
The balance consists of Fe and inevitable impurities,
The manufacturing method of the nozzle plate of the steam turbine of Claim 1. The composition of the nozzle plate is mass%,
C: 0.10 to 0.15,
Si: 0.60 or less,
Mn: 0.40 to 0.60,
Ni: 0.60 or less,
Cr: 10.0 to 11.5,
Mo: 0.80 to 1.10,
V: 0.15-0.25,
Nb: 0.05-0.20
N: 0.01-0.03
Containing
The balance consists of Fe and inevitable impurities,
The manufacturing method of the nozzle plate of the steam turbine of Claim 1. The composition of the nozzle plate is mass%,
C: 0.10 to 0.15,
Si: 0.60 or less,
Mn: 0.40 to 0.60,
Ni: 0.60 or less,
Cr: 9.2 to 10.2,
Mo: 0.80 to 1.10,
V: 0.15-0.25,
W: 0.80 to 1.10,
Nb: 0.05 to 0.10,
N: 0.01-0.03
Containing
The balance consists of Fe and inevitable impurities,
The manufacturing method of the nozzle plate of the steam turbine of Claim 1. The composition of the nozzle plate is mass%,
C: 0.10 to 0.15,
Si: 0.30 or less,
Mn: 0.40 to 0.60,
Ni: 0.30 or less,
Cr: 9.0 to 10.5
Mo: 0.50 to 0.80,
V: 0.15-0.25,
W: 1.60 to 1.90,
Nb: 0.015-0.025,
Co: 1.0-3.0,
N: 0.01-0.03
Containing
The balance consists of Fe and inevitable impurities,
The manufacturing method of the nozzle plate of the steam turbine of Claim 1. The composition of the nozzle plate is mass%,
C: 0.10 to 0.15,
Si: 0.30 or less,
Mn: 0.40 to 0.60,
Ni: 0.30 or less,
Cr: 9.0 to 10.5
Mo: 0.50 to 0.80,
V: 0.15-0.25,
W: 1.60 to 1.90,
Nb: 0.015-0.025,
Co: 1.0-3.0,
B: 0.005 to 0.009
N: 0.01-0.03
Containing
The balance consists of Fe and inevitable impurities,
The manufacturing method of the nozzle plate of the steam turbine of Claim 1.

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