JP2019104978A - Nozzle, and method for producing the same - Google Patents

Abstract

To provide a nozzle having excellent high-temperature properties.SOLUTION: A nozzle according to an embodiment has a nozzle plate disposed between a diaphragm outer ring and a diaphragm inner ring and is used for a steam turbine. The diaphragm outer ring and diaphragm inner ring are each formed of cast steel containing, in mass%, C: 0.10-0.15, Si: 0.60 or less, Mn: 0.40-0.60, Ni: 0.60 or less, Cr: 9.0-10.5, Mo: 0.80-1.10, V: 0.15-0.25, W: 0.80-1.10, Nb: 0.05-0.10 with the balance being Fe and inevitable impurities.SELECTED DRAWING: Figure 1

Description

  Embodiments of the present invention relate to a nozzle and a method of manufacturing the same.

  In the steam turbine, the nozzles have a plurality of nozzle plates (vanes) disposed between the diaphragm outer ring and the diaphragm inner ring, and form a vane cascade. In the nozzle, the nozzle plate is fixed to the diaphragm outer ring and the diaphragm inner ring.

  The nozzle plate is fixed by welding at least one of the outer ring side and the inner ring side of the nozzle plate. Besides, the outer ring side of the nozzle plate is fitted to the fitting portion such as a groove formed on the diaphragm outer ring, and the inner ring side of the nozzle plate is fitted to a fitting portion such as a groove formed on the diaphragm inner ring Thereby, the nozzle plate is fixed.

Patent No. 4040922 Patent No. 3106130 JP, 2010-242221, A JP-A-5-125471 JP, 2007-092122, A

  Usually, the diaphragm outer ring and the diaphragm inner ring are manufactured by cutting a ring material formed by forging, or a material such as a bent plate. Moreover, about the diaphragm outer ring | wheel and diaphragm inner ring which comprise the nozzle installed in the low temperature part of a steam turbine, it manufactures by cutting about the raw material formed by casting.

  In recent years, in a steam turbine, the temperature (inlet temperature) of steam introduced as a working medium to an inlet has been increased. For this reason, in order to cope with the increase in inlet temperature, a nozzle excellent in high temperature characteristics is required. Specifically, there is a need for a nozzle that is high in creep strength and resistant to deformation at high temperatures.

  Therefore, the problem to be solved by the present invention is to provide a nozzle excellent in high temperature characteristics and a method of manufacturing the same.

  The nozzle of the embodiment has a nozzle plate disposed between the diaphragm outer ring and the diaphragm inner ring, and is used for a steam turbine. The diaphragm outer ring and the diaphragm inner ring are, by mass%, C: 0.10 to 0.15, Si: 0.60 or less, Mn: 0.40 to 0.60, Ni: 0.60 or less, Cr: 9.0 0.510.5, Mo: 0.80 to 1.10, V: 0.15 to 0.25, W: 0.80 to 1.10, Nb: 0.05 to 0.10, the balance being It is formed of cast steel consisting of Fe and unavoidable impurities.

Drawing 1 is a figure showing the important section of the steam turbine concerning an embodiment. FIG. 2 is a cross-sectional view schematically showing a surface portion of the nozzle plate 25 in a modification of the embodiment.

  First, the cast steels (M1) and (M2) of the embodiment will be described. The components of the cast steels (M1) and (M2) are in the ranges shown below. Although details will be described later, cast steels (M1) and (M2) are used when forming the diaphragm outer ring and the diaphragm inner ring in a nozzle used for a steam turbine.

  The composition of the cast steel (M1) is, in 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. 0 to 0.5, Mo: 0.80 to 1.10, V: 0.15 to 0.25, W: 0.80 to 1.10, Nb: 0.05 to 0.10, the balance Is composed of Fe and unavoidable impurities.

  The composition of the cast steel (M2) is, in 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 0.5, 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. It contains 0 to 3.0, B: 0.005 to 0.009, and the balance consists of Fe and unavoidable impurities.

  In the above, “C: 0.10 to 0.15” and the like indicate that the content of the C element is 0.10 mass% or more and 0.15 mass% or less. “Si: 0.60 or less” or the like indicates that the content of Si element is 0.60 mass% or less, and includes the case where the content of Si element is zero (the same applies hereinafter) .

  The reasons for setting the proportions (content rates) of the respective components in the cast steels (M1) and (M2) of the embodiment to the above range will be described.

(1) C (carbon) [(M1) ... 0.10 to 0.15, (M2) ... 0.10 to 0.15]
C is a component necessary for securing the hardenability and the fluidity of the molten metal at the time of casting, and is an essential component as a constituent element constituting a carbide contributing to precipitation strengthening. In the cast steels (M1) and (M2), when the content of C is less than the lower limit value of the above range, the above-described action and effect become smaller. When the content of C exceeds the upper limit value of the above range, the aggregation of carbides is promoted, and the segregation tendency at the time of casting is increased, so that the weldability including the repair is deteriorated. For this reason, in the cast steels (M1) and (M2), the content of C is set to the above range.

(2) Si (silicon) [(M1) ... 0.60 or less, (M2) ... 0.30 or less]
Si is a component that is useful as a deoxidizer and improves the fluidity of the molten metal. In the cast steel (M1), when the content of Si exceeds the upper limit value of the above range, the reduction in toughness and the embrittlement are significantly promoted. In addition, since the cast steel (M2) contains a large amount of ferrite forming elements, stabilization of the structure can be realized by setting the content of Si to the upper limit value of the above range or less. For this reason, in cast steel (M1) and (M2), the content rate of Si is set to the said range.

(3) Mn (manganese) [(M1) ... 0.40 to 0.60, (M2) ... 0.40 to 0.60]
Mn is a component useful as a desulfurizing agent. In the cast steels (M1) and (M2), when the content of Mn exceeds the upper limit of the above range, the amount of non-metallic inclusions increases and the toughness decreases and the creep rupture strength decreases There is. Moreover, in cast steel (M1) and (M2), stabilization of a structure | tissue can be implement | achieved by making the content rate of Mn more than the lower limit of the said range. For this reason, in cast steel (M1) and (M2), the content rate of Mn is set to the said range.

(4) Ni (nickel) [(M1) ... 0.60 or less, (M2) ... 0.30 or less]
Ni is a component that improves the hardenability and toughness and also has an effect of suppressing the formation of ferrite. In the cast steel (M1), when the Ni content exceeds the upper limit value of the above range, a decrease in creep strength may occur. Since the cast steel (M2) contains a Co (cobalt) component, lowering the creep strength is suppressed by making the Ni content at least the lower limit of the above range, and the structure is stabilized and the high temperature is excellent. Characteristics can be realized. For this reason, in cast steel (M1) and (M2), the content rate of Ni is set to the said range.

(5) Cr (chromium) [(M1) ... 9.0 to 10.5, (M2) ... 9.0 to 10.5]
Cr is an effective component for improving oxidation resistance and corrosion resistance, and is an essential component as a constituent element of carbonitrides contributing to precipitation strengthening. In the cast steels (M1) and (M2), when the content of Cr is less than the lower limit value of the above range, the number of precipitates (carbonitrides) that deposit Cr as a constituent element in the implementation of the tempering heat treatment decreases. In some cases, high temperature stability can not be secured sufficiently. When the content of Cr exceeds the upper limit value of the above range, ferrite is formed and aggregation and coarsening of carbonitrides are accelerated. For this reason, in cast steel (M1) and (M2), the content rate of Cr is set to the said range.

(6) Mo (molybdenum) [(M1) ... 0.80 to 1.10, (M2) ... 0.50 to 0.80]
Mo is a component that contributes to solid solution strengthening, is a constituent element of carbonitrides, and is a component that contributes to precipitation strengthening. Mo is a constituent element of the precipitate deposited when heat treatment is performed for a long time in a high temperature environment. In the cast steel (M1), when the content of Mo is less than the lower limit value of the above range, it becomes difficult to keep the amount of Mo contributing to solid solution strengthening high for a long time. When the content of Mo exceeds the upper limit of the above range, the toughness is lowered and the formation of ferrite is promoted. For this reason, in the cast steel (M1) of the embodiment, the content of Mo is set to the above range. Since the cast steel (M2) of the embodiment has a large content ratio of W (tungsten) component, the content of Mo is more than that of the cast steel (M1) in order to maintain high temperature characteristics and to suppress the formation of ferrite. The proportion is small.

(7) V (vanadium) [(M1) ... 0.15 to 0.25, (M2) ... 0.15 to 0.25]
V is a component that contributes to solid solution strengthening and is a component that contributes to the formation of fine carbonitrides. In the cast steels (M1) and (M2), when the content of V is less than the lower limit value of the above range, the above-described action and effect are not sufficient. If the V content exceeds the upper limit of the above range, a decrease in toughness occurs. For this reason, in the cast steels (M1) and (M2) of the embodiment, the V content is in the above range.

(8) W (tungsten) [(M1) ... 0.80 to 1.10, (M2) ... 1.60 to 1.90]
W is a component that contributes to solid solution strengthening, is a constituent element of carbonitrides, and is a component that contributes to precipitation strengthening. W can significantly enhance the high temperature stability of the precipitate, particularly when added in combination with Mo. W is a constituent element of the precipitate when heat treatment is performed for a long time in a high temperature environment. In the cast steel (M1), when the content of W is less than the lower limit value of the above range, it becomes difficult to keep the amount of W contributing to solid solution strengthening high for a long time. When the content of W exceeds the upper limit value of the above range, the toughness is lowered and the formation of ferrite is promoted. For this reason, in the cast steel (M1) of the embodiment, the content of W is set to the above range. In addition, in cast steel (M2), since the content rate of W is larger than the case of cast steel (M1), it is possible to implement | achieve a still more favorable high temperature characteristic. For this reason, in the cast steel (M2), in order to suppress the formation of ferrite, as described above, the content ratio of Mo is smaller than in the case of the cast steel (M1).

(9) Nb (niobium) [(M1) ... 0.05 to 0.10, (M2) ... 0.015 to 0.025]
Nb is a component that contributes to solid solution strengthening, and also contributes to the formation of fine carbonitrides. In the cast steel (M1), when the content of Nb is less than the lower limit value of the above range, the above-described action and effect are not sufficient. When the content of Nb exceeds the upper limit value of the above range, the amount of coarse Nb carbonitrides formed increases. For this reason, in the cast steel (M1) of the embodiment, the content of Nb is in the above range. The cast steel (M2) contains a B element, and the content ratio of the Nb component is smaller than that of the cast steel (M1) in order to improve the structural stability.

(10) Co (cobalt) [(M1) ... 0, (M2) ... 1.0 to 3.0]
Co is a component that contributes to the effect of suppressing the formation of ferrite. In the cast steel (M2) of the embodiment, when the content of Co is less than the lower limit value of the above range, the above-described action and effect are not sufficient. If the content of Co exceeds the upper limit value of the above range, precipitation of intermetallic compounds is promoted, and creep strength is reduced. For this reason, in the cast steel (M2) of the embodiment, the content of Co is in the above range.

(11) B (boron) [(M1) ... 0, (M2) ... 0.005 to 0.009]
B is a component that enhances deformation resistance near grain boundaries and contributes to the improvement of high-temperature creep strength. In the cast steel (M2), when the content of B is less than the lower limit value of the above range, the improvement of the high temperature creep strength is not sufficient. If the B content exceeds the upper limit of the above range, cracking may occur during welding. For this reason, in the cast steel (M2), the content of B was in the above range.

  Hereinafter, in the present embodiment, a steam turbine provided with a nozzle formed using the above-described cast steel (M1) or cast steel (M2) will be described with reference to FIG. FIG. 1 shows a cross section along the vertical plane (yz plane).

  As shown in FIG. 1, the steam turbine 1 is a rotary machine and is configured to rotate a turbine rotor 22 by supplying steam as a working fluid. Here, the steam turbine 1 is an axial flow turbine, and 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 of a multi-stage type, and a plurality of stages of turbine stages configured by moving blades 21 and a nozzle plate 25 are arranged in the axial direction along the rotation axis AX, and steam is generated in each of the plurality of turbine stages. Do the work. Thereby, 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 rotation of the turbine rotor 22 drives the generator (not shown) to generate power. A plurality of rotor disks 221 are provided on the outer peripheral surface of the turbine rotor 22. The moving blades 21 are installed on the outer peripheral surface of a rotor disk 221 provided on the turbine rotor 22. A plurality of moving blades 21 are arranged at intervals 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 form a moving blade cascade. The blade cascade is a plurality of stages, and each of the blade cascades of the plurality of stages is arranged along the rotation axis AX of the turbine rotor 22.

  The nozzle 10 is installed inside the casing 20. The nozzle 10 is composed of a diaphragm outer ring 23, a diaphragm inner ring 24 and a nozzle plate 25. In the nozzle 10, the diaphragm outer ring 23 has a ring shape and is disposed on the inner peripheral surface of the casing 20. The diaphragm outer ring 23 is configured by combining an upper half and a lower half. The diaphragm inner ring 24 has a ring shape similar to the diaphragm outer ring 23 and is installed inside the diaphragm outer ring 23 at a distance from the diaphragm outer ring 23. Like the diaphragm outer ring 23, the diaphragm inner ring 24 is configured by combining an upper half portion and a lower half portion. A plurality of nozzle plates 25 are provided between the diaphragm outer ring 23 and the diaphragm inner ring 24.

  Here, the plurality of nozzle plates 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 vane cascade. The stator blade cascade is a plurality of stages as in the case of the rotor blade cascade, and a plurality of stages of stator blade cascades are provided 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 as a working fluid into the interior of the casing 20 through the steam inlet pipe 28.

  In the nozzle 10 of the present embodiment, the diaphragm outer ring 23 and the diaphragm inner ring 24 are formed of the above-described cast steel (M1) or cast steel (M2).

  Below, in an embodiment, a method of manufacturing the above-mentioned nozzle 10 using above-mentioned cast steel (M1) or cast steel (M2) is explained.

  In manufacturing the above-described nozzle 10, first, cast steel (M1) or cast steel (M2) is formed into a ring shape by centrifugal casting or ordinary casting (sand casting) (first step). Here, cast steel (M1) or cast steel (M2) is formed by pouring a molten metal into a mold or a sand mold. Thereby, cast steel (M1) or cast steel (M2) is formed in the state to which excess thickness was provided rather than the final shape. Then, a tempering heat treatment is performed on the cast steel (M1) or the cast steel (M2). In the present embodiment, annealing, normalizing, quenching (cooling) and tempering are sequentially performed as the tempering heat treatment.

  Next, the diaphragm outer ring 23 and the diaphragm inner ring 24 are formed from the ring-shaped cast steel (M1) or cast steel (M2) (second step). Here, by performing machining (finishing such as cutting) on ring-shaped cast steel (M1) or cast steel (M2), the diaphragm outer ring 23 is formed into a final shape, and the diaphragm inner ring 24 is formed into a final shape. Do.

  Next, the nozzle plate 25 is disposed between the diaphragm outer ring 23 and the diaphragm inner ring 24 (third step). Here, the nozzle plate 25 is joined to each of the diaphragm outer ring 23 and the diaphragm inner ring 24 by welding. In addition to the above, the outer ring side of the nozzle plate 25 is inserted into and fitted to a fitting portion (not shown) such as a groove formed in the diaphragm outer ring 23, and a groove formed in the diaphragm inner ring 24 is fitted The nozzle plate 25 may be fixed by inserting and fitting the inner ring side of the nozzle plate 25 into a portion (not shown).

  The nozzle 10 is completed by sequentially performing each process as described above.

  In the present embodiment, when the nozzle 10 is formed using cast steel (M1), the nozzle 10 continues for a long time even under a high temperature environment where the steam temperature at steady state is 580 to 610 ° C. It has sufficient strength. Also, when the nozzle 10 is formed using cast steel (M2), the nozzle 10 has sufficient strength over a long period of time, even in a high temperature environment where the steam temperature at steady state is 610 to 630 ° C. Have. For this reason, in this embodiment, stable operation can be realized in the steam turbine 1.

  In this embodiment, after forming cast steel (M1) or cast steel (M2) into a ring shape by centrifugal casting or ordinary casting, the diaphragm outer ring 23 and the diaphragm inner ring 24 are formed from the ring shaped cast steel (M1) or cast steel (M2). Form. For this reason, in the present embodiment, bending is not necessary in manufacturing the diaphragm outer ring 23 and the diaphragm inner ring 24, and the time required for cutting can be shortened. As a result, in the present embodiment, the production time of the nozzle 10 can be shortened. Specifically, when manufacturing the diaphragm outer ring 23 and the diaphragm inner ring 24 by forging, it takes two to three months from the formation of the material to the formation. On the other hand, in the case of this embodiment, the diaphragm outer ring 23 and the diaphragm inner ring 24 can be manufactured in one day. Furthermore, in the present embodiment, the outer peripheral surface, the side surface, the fitting portion, and the like of each of the diaphragm outer ring 23 and the diaphragm inner ring 24 can be integrally processed from ring-shaped cast steel (M1) or cast steel (M2). An improvement in dimensional accuracy can be realized. Accordingly, the assembling accuracy when assembling the nozzle 10 by attaching the nozzle plate 25 to each of the diaphragm outer ring 23 and the diaphragm inner ring 24 can be improved, and the assembling accuracy when assembling the nozzle 10 to the casing 20 can be improved. It is.

  FIG. 2 is a cross-sectional view schematically showing a surface portion of the nozzle plate 25 in a modification of the embodiment.

As shown in FIG. 2, the erosion prevention layer 70 may be formed on the surface of the nozzle plate 25. The formation of the erosion prevention layer 70 is performed by thermally spraying a coating material on the nozzle plate 25 disposed between the diaphragm outer ring 23 and the diaphragm inner ring 24 (fourth step). The coating material preferably comprises 80 parts by weight of CrC (Cr ₃ C ₂ ) and 20 parts by weight of NiCr. When CrC and NiCr are in the above proportions, adhesion to the base material (nozzle plate 25) is high, which is preferable in that peeling by flying objects during operation can be suppressed.

The formation of the erosion prevention layer 70 described above is carried out by spraying the powder of the above material by a spraying method such as high velocity flame spraying (HVOF; High Velocity Oxy-Fuel). In this case, the erosion prevention layer 70 immediately after the thermal spraying has a Vickers hardness of about 800. However, since the Cr ₃ C ₂ in the erosion preventing layer 70 is transformed to Cr ₇ C ₃ after the erosion preventing layer 70 is heated in the operation of the steam turbine 1, the erosion preventing layer 70 has an increased Vickers hardness. . Specifically, when the corrosion prevention layer 70 was heated for 60 hours under the temperature conditions of 580 ° C., 610 ° C., and 640 ° C., the Vickers hardness increased to about 1000, and the state was maintained. . For this reason, in the present embodiment, the erosion preventing layer 70 can effectively suppress the occurrence of the erosion due to the solid particles colliding with the nozzle plate 25 in the operation of the steam turbine 1.

  The erosion prevention layer 70 is formed to cover the surface of the portion of the nozzle plate 25 located on the rear edge side. The erosion prevention layer 70 may be formed to cover a part of the surface of the nozzle plate 25 or may be formed to cover the entire surface of the nozzle plate 25.

  In addition, if necessary, the corrosion prevention layer 70 may be formed by spraying a coating material on the surfaces of the diaphragm outer ring 23 and the diaphragm inner ring 24 in addition to the surface of the nozzle plate 25.

  In addition, the nozzle plate 25 may be formed of cast steel (M1) or cast steel (M2).

  Hereinafter, Examples and Comparative Examples of the above-described cast steel (M1) or cast steel (M2) will be described using Tables 1 and 2.

  In Tables 1 and 2, P1 to P5 are examples, and C1 to C4 are comparative examples. Here, with respect to the cast steel (M1), the examples are P1 to P3 and the comparative examples are C1 and C2. With respect to the cast steel (M2), the examples are P4 and P5, and the comparative examples are C3 and C4.

[A] Production of cast steel The cast steel (test cast steel) of each example was produced so that each component had the value shown in Table 1.

  Here, first, the materials of the respective components constituting the cast steel of each example were mixed at a ratio shown in Table 1 and melted to form a molten metal. Next, the cast steel of each example was formed into a ring shape by performing centrifugal casting or ordinary casting (sand casting) using the molten metal.

  And heat treatment heat treatment was performed about the cast steel. Here, annealing, normalizing, quenching (cooling) and tempering were sequentially performed as the tempering heat treatment. The tempering heat treatment was performed under the conditions shown below. The cast steel of each example was produced so that the tensile strength at normal temperature after the tempering heat treatment would be about 700 MPa.

(Annealing)
・ Temperature ... 1100 ° C
・ Time ... 3 hours

(Normalized)
Temperature: 1070 ° C
・ Time ... 3 hours

(Hardening (cooling))
・ Hengd cooling

(Tempered)
・ Temperature ... 700 ° C
・ Time ... 3 hours

[B] Test Details As shown in Table 2, various tests were conducted on the cast steel of each example.

  Here, with respect to the cast steel of each example, tensile strength (JIS Z 2241) and creep rupture strength (JIS Z 2271) for 100,000 hours were determined. The tensile strength was determined by conducting a tensile test at 600 ° C. using a JIS No. 4 test piece. The 100,000 hour creep rupture strength was calculated from the results of the creep rupture test. The creep rupture test was performed at each temperature condition shown in Table 2.

In addition to this, as shown in Table 2, a test of “welding construction” was conducted on the cast steels of the respective examples. The test of "welding construction" was performed in the following procedures. The cast steel was processed into a flat plate having a thickness of 10 mm. Then, the flat plate was preheated to 250 ° C., and a welding 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 occurrence of the crack was confirmed about the welding part among the flat plates. In Table 2, the case where a crack does not generate | occur | produce in a weld part at the time of welding is shown by "(circle)", and the case where a crack generate | occur | produced in a weld part is shown by "x" at the time of welding.

[C] Test Results [C-1] Cast Steel (M1) Comparing the test results between P1 to P3 and C1 and C2, “tensile strength” is C1 and C2 for P1 to P3. Higher than in the case of.

  "100,000 hour creep rupture strength" is higher in the case of P1 to P3 than in the case of C1 and C2. C2 is used for a nozzle having a maximum temperature of 600 ° C. in an actual steam turbine, and is confirmed to have a sufficient “100,000 hour creep rupture strength”. C2 has a “100,000 hour creep rupture strength” at 600 ° C. of 75 MPa. In P1 to P3, “100,000 hour creep rupture strength” is 75 MPa or more at 610 ° C. or less. Therefore, P1 to P3 can have sufficient strength for a long time even under a steam environment of 610 ° C.

  In the test of "welding construction", although P1-P3 did not have a crack in a welding part, C1 has a crack in a welding part.

  The content ratio of each component constituting P1 to P3 is within the range of the content ratio of each component constituting the cast steel (M1) different from the case of C1 and C2. Thus, P1 to P3 corresponding to the cast steel (M1) have excellent mechanical properties as described above.

[C-2] Comparison of test results between P4, P5 and C3, C4 for cast steel (M2), “tensile strength” is equivalent between P4, P5 and C3, C4 .

  “100,000 hour creep rupture strength” is equivalent between P4, P5 and C3 at 600 ° C., but at 630 ° C., P4, P5 is higher than C3. In P4 and P5, “100,000 hour creep rupture strength” is 75 MPa or more at 630 ° C. or less. For this reason, P4 and P5 can have sufficient strength for a long time even under a steam environment of 630 ° C.

  In "welding construction", although P4 and P5 did not have a crack in a welding part, C3 has a crack in a welding part.

  The content ratio of each component constituting P4 and P5 is different from that in the case of C3 and C4, and is within the range of the content ratio of each component constituting the cast steel (M2) described above. Thus, P4 and P5 corresponding to the cast steel (M2) have excellent mechanical properties as described above.

  From the above results, it can be seen that the cast steels (M1) and (M2) have excellent mechanical properties in a high temperature environment. That is, in cast steels (M1) and (M2), in a high temperature environment, "tensile strength" and "100,000 hour creep rupture strength" are sufficiently high, and no crack occurs in the welded portion in "welding construction" Can be seen.

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

DESCRIPTION OF SYMBOLS 1 ... steam turbine, 10 ... nozzle, 20 ... casing, 21 ... moving blade, 22 ... turbine rotor, 221 ... rotor disk, 23 ... diaphragm outer ring, 24 ... diaphragm inner ring, 25 ... nozzle plate (stationary blade), 28 ... steam Inlet pipe, 70 ... Erosion prevention layer, AX ... rotation axis

Claims (4)

A nozzle plate is disposed between the diaphragm outer ring and the diaphragm inner ring, and is a nozzle used for a steam turbine,
The diaphragm outer ring and the diaphragm inner ring are
In mass%,
C: 0.10 to 0.15,
Si: 0.60 or less,
Mn: 0.40 to 0.60,
Ni: 0.60 or less,
Cr: 9.0-10.5,
Mo: 0.80 to 1.10,
V: 0.15 to 0.25,
W: 0.80 to 1.10,
Nb: 0.05 to 0.10
Is made of cast steel, the balance of which contains Fe and unavoidable impurities,
nozzle. A nozzle plate is disposed between the diaphragm outer ring and the diaphragm inner ring, and is a nozzle used for a steam turbine,
The diaphragm outer ring and the diaphragm inner ring are
In mass%,
C: 0.10 to 0.15,
Si: 0.30 or less,
Mn: 0.40 to 0.60,
Ni: 0.30 or less,
Cr: 9.0-10.5,
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
Is made of cast steel, the balance of which contains Fe and unavoidable impurities,
nozzle. A method of manufacturing a nozzle according to claim 1 or 2, wherein
A first step of forming the cast steel into a ring shape by centrifugal casting or ordinary casting;
A second step of forming the diaphragm outer ring and the diaphragm inner ring from the cast steel;
And a third step of disposing the nozzle plate between the diaphragm outer ring and the diaphragm inner ring.
Method of manufacturing a nozzle. The method further comprises a fourth step of forming an erosion prevention layer on the surface of the nozzle plate by spraying a coating material on the nozzle plate disposed between the diaphragm outer ring and the diaphragm inner ring.
The coating material comprises 80 parts by weight of CrC and 20 parts by weight of NiCr
The method of manufacturing a nozzle according to claim 3.

Images