JP2016065265A - Heat resistant steel for steam turbine rotor blade and steam turbine rotor blade - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat resistant steel for steam turbine rotor blade capable of achieving enhancement of long term creep rupture life and excellent in high temperature property, durability or the like, and a steam turbine rotor blade.SOLUTION: The heat resistant steel for steam turbine rotor blade of the embodiment contains, by mass%, C: 0.05 to 0.13%, Si: 0.01 to 0.1%, Mn: over 0.15% and 0.5% or less, Ni: 0.01 to 0.4%, Cr: 9 to 11.5%, Mo: 0.01 to 0.5%, V: 0.15 to 0.3%, Co: 1.5 to 4%, W: 1 to 3%, N: 0.001 to less than 0.01%, Nb: 0.01 to 0.15%, B: 0.005 to 0.015%, Re: 0.001 to 0.3% with the balance Fe and inevitable impurities.SELECTED DRAWING: None

Description

  Embodiments described herein relate generally to heat resistant steel for steam turbine blades and steam turbine blades.

  Thermal power generation systems tend to increase the steam temperature of the steam turbine in order to improve power generation efficiency. As a result, the high temperature characteristics required for the heat-resistant steel used in the steam turbine become even more severe.

  Many proposals have been made so far as heat-resistant steel for steam turbine blades. However, even these heat-resistant steels do not necessarily have sufficient long-term creep rupture strength. In order to contribute to the improvement of power generation efficiency as a heat-resistant steel for steam turbine blades, it is necessary to improve the long-time creep rupture life more than ever.

JP-A-8-176749 Japanese Patent No. 4284010

  The problem to be solved by the present invention is to provide a heat resistant steel for steam turbine rotor blades and a steam turbine rotor blade capable of improving the creep rupture life for a long time and having excellent high temperature characteristics and durability. .

  The heat-resistant steel for steam turbine rotor blades of the embodiment is, in mass%, C: 0.05 to 0.13%, Si: 0.01 to 0.1%, Mn: more than 0.15% and 0.5% Hereinafter, Ni: 0.01 to 0.4%, Cr: 9 to 11.5%, Mo: 0.01 to 0.5%, V: 0.15 to 0.3%, Co: 1.5 to 4%, W: 1 to 3%, N: 0.001 to less than 0.01%, Nb: 0.01 to 0.15%, B: 0.005 to 0.015%, Re: 0.001 It contains 0.3% and the balance consists of Fe and inevitable impurities.

  In the embodiment according to the present invention, the inventors have made it possible to increase the power generation efficiency in the power generation system, improve the long-term durability of the steam turbine, etc. As a result of diligent research aimed at improving the long-term creep rupture life, it has been found that it is effective to optimize the N content in order to improve the above characteristics.

  The heat-resistant steel for steam turbine rotor blades of the embodiment is, in mass%, C: 0.05 to 0.13%, Si: 0.01 to 0.1%, Mn: more than 0.15% and 0.5% Hereinafter, Ni: 0.01 to 0.4%, Cr: 9 to 11.5%, Mo: 0.01 to 0.5%, V: 0.15 to 0.3%, Co: 1.5 to 4%, W: 1 to 3%, N: 0.001 to less than 0.01%, Nb: 0.01 to 0.15%, B: 0.005 to 0.015%, Re: 0.001 It contains 0.3% and the balance consists of Fe and inevitable impurities.

  The reason for limitation of each composition component range in the heat resistant steel for steam turbine rotor blades of the above-described embodiment will be described. In the following description, “%” representing a composition component is “% by mass” unless otherwise specified.

  Examples of inevitable impurities in heat-resistant steel for steam turbine blades include P and S.

(1) C (carbon)
C secures hardenability and promotes martensitic transformation, forms M ₂₃ C ₆ type carbide with Fe, Cr, Mo, etc. in the alloy, and MX type charcoal with Nb, V, N, etc. It is an indispensable element for forming nitrides and increasing high temperature creep strength by precipitation strengthening. C contributes to improvement in yield strength and is an indispensable element for suppressing the formation of δ ferrite and BN. In order to exhibit these effects, it is necessary to contain 0.05% or more of C. On the other hand, if the C content exceeds 0.13%, the agglomeration and coarsening of carbides and carbonitrides easily occur and the high temperature creep rupture strength decreases. Therefore, the C content is determined to be 0.05 to 0.13%. For the same reason, the C content is preferably 0.08 to 0.12%.

(2) Si (silicon)
Si is an element effective as a deoxidizer for molten steel. If the Si content exceeds 0.1%, segregation inside the steel ingot increases and the temper embrittlement sensitivity becomes extremely high. And notch toughness is impaired, and by maintaining for a long time at high temperature, the change of a precipitate form is promoted and toughness deteriorates with time. On the other hand, when Si contains a trace amount, segregation decreases conversely, so that it is necessary to contain 0.01% or more of Si in order to exert these effects. Therefore, the Si content is determined to be 0.01 to 0.1%. For the same reason, the Si content is preferably 0.03 to 0.1%.

(3) Mn (manganese)
Mn is an element that is effective as a deoxidizing agent and a desulfurizing agent at the time of dissolution, and also effective in improving hardenability and improving strength. In order to exhibit this effect, it is necessary to contain 0.15% or more of Mn. On the other hand, when the Mn content exceeds 0.5%, Mn combines with S to form non-metallic inclusions of MnS, lowering the toughness, promoting toughness deterioration with time, and high-temperature creep rupture. Reduce strength. Therefore, the Mn content is more than 0.15% and 0.5% or less. For the same reason, the Mn content is preferably more than 0.15% and 0.3% or less.

(4) Ni (nickel)
When the Ni content exceeds 0.4%, the agglomeration and coarsening of carbides and Laves phases are promoted, and the reduction in high temperature creep rupture strength is promoted. On the other hand, since Ni is an element that suppresses the formation of δ ferrite and is useful for improving toughness, it is preferably contained in an amount of 0.01% or more. Therefore, the Ni content is determined to be 0.01 to 0.4%. For the same reason, the Ni content is preferably 0.01 to 0.3%.

(5) Cr (chrome)
Cr is an indispensable element for improving oxidation resistance and high-temperature corrosion resistance and for increasing high-temperature creep rupture strength by precipitation strengthening with M ₂₃ C ₆ type carbide. In order to exert these effects, it is necessary to contain 9% or more of Cr. On the other hand, as the Cr content increases, the tensile strength at room temperature and the short-time creep rupture strength on the high stress side increase, but on the other hand, the long-term creep rupture strength on the low stress side tends to decrease. This is considered to be a cause of the bending phenomenon of long creep rupture life on the low stress side. When the Cr content increases, the disappearance of the MX type carbonitride accelerates in a long time region, and the aggregation and coarsening of the M ₂₃ C ₆ type carbide accelerates, so that the substructure (microstructure) of the martensite structure This is due to significant changes. These tendencies increase rapidly when the Cr content exceeds 11.5%. Therefore, the Cr content is determined to be 9 to 11.5%. For the same reason, the Cr content is preferably 9 to 11%.

(6) Mo (molybdenum)
Mo is dissolved in the alloy to strengthen the matrix, and fine carbides and a fine Laves phase are generated to improve the high temperature creep rupture strength. Mo is an element effective for suppressing temper embrittlement. In order to exhibit these effects, it is necessary to contain Mo 0.01% or more. On the other hand, if the Mo content exceeds 0.5%, δ ferrite is generated and the toughness is significantly reduced. Therefore, the Mo content is determined to be 0.01 to 0.5%. For the same reason, the Mo content is preferably set to 0.01 to 0.4%.

(7) V (Vanadium)
V is an element effective for forming fine carbides and carbonitrides and improving high temperature creep rupture strength. In order to exhibit this effect, it is necessary to contain V 0.15% or more. On the other hand, if the content of V exceeds 0.3%, excessive precipitation of carbide occurs, leading to a decrease in high-temperature creep rupture strength. Therefore, the V content is determined to be 0.15 to 0.3%. For the same reason, the V content is preferably 0.17 to 0.27%.

(8) Co (Cobalt)
Co suppresses the formation of δ ferrite and improves high temperature tensile strength and high temperature creep rupture strength by solid solution strengthening. This is because the Ac ₁ transformation point is hardly changed by the addition of Co. In order to exhibit these effects, it is necessary to contain 1.5% or more of Co. On the other hand, excessive addition of Co reduces the solid solubility limit of W, thereby promoting aggregation and coarsening of the Laves phase and μ phase and causing a decrease in creep strength for a long time. Therefore, from the viewpoint of suppressing a decrease in long-term creep strength, the Co content is set to 4% or less. For the same reason, the Co content is preferably 1.5 to 3%.

(9) W (tungsten)
W suppresses aggregation and coarsening of M ₂₃ C ₆ type carbide. W is an element effective for improving high-temperature tensile strength and high-temperature creep rupture strength by solid-solution strengthening in the alloy by dissolving in the alloy to disperse and precipitate the Laves phase on the lath boundary. In order to exhibit these effects, it is necessary to contain 1% or more of W. On the other hand, if the W content exceeds 3%, δ ferrite and a coarse Laves phase are likely to be generated, ductility and toughness are lowered, and high-temperature creep rupture strength is also lowered. Therefore, the W content is determined to be 1 to 3%. For the same reason, the W content is preferably 2.6 to 3%.

(10) N (nitrogen)
N combines with C, Nb, V, etc. to form carbonitrides and improves high temperature creep rupture strength. If the N content is less than 0.001%, sufficient tensile strength and high temperature creep rupture strength cannot be obtained. On the other hand, N has a strong connection with B, and when the N content is 0.01% or more, a nitride of BN is generated, which makes it difficult to produce a healthy steel ingot, and hot working Decreases in ductility and toughness. Moreover, since the content of the solid solution B effective for the high temperature creep rupture strength decreases due to the precipitation of the BN phase, the high temperature creep rupture strength decreases. Therefore, the N content was lowered as compared with the prior art to improve the high temperature creep rupture strength. Therefore, the N content is determined to be less than 0.001 to 0.01%. For the same reason, the N content is preferably 0.008 to less than 0.01%.

(11) Nb (Niobium)
Nb is effective in improving the tensile strength at room temperature, forms fine carbides and carbonitrides, and improves high temperature creep rupture strength. Moreover, Nb produces | generates fine NbC, promotes refinement | miniaturization of a crystal grain, and improves toughness. Part of Nb also has the effect of precipitating MX type carbonitride compounded with V carbonitride to improve the high temperature creep rupture strength. In order to exhibit these effects, it is preferable to contain Nb 0.01% or more. On the other hand, when the Nb content exceeds 0.15%, coarse carbides and carbonitrides are precipitated, and ductility and toughness are lowered. Therefore, the Nb content is determined to be 0.01 to 0.15%. For the same reason, the Nb content is preferably 0.01 to 0.1%.

(12) B (boron)
B increases hardenability and improves toughness when added in a small amount. In addition, B has the effect of suppressing aggregation and coarsening of carbide, carbonitride, and Laves phase in the martensite packet, martensite block, martensite lath and martensite lath of the austenite grain boundary and its substructure for a long time at high temperature. Have. Further, B is an element effective for improving the high temperature creep rupture strength by being added in combination with W, Nb or the like. In order to exhibit these effects, it is necessary to contain B 0.005% or more. On the other hand, if the B content exceeds 0.015%, B and N are combined to precipitate a BN phase, hot workability is impaired, and high temperature creep rupture ductility and toughness are greatly reduced. In addition, precipitation of the BN phase reduces the content of solid solution B effective for high-temperature creep rupture strength, so that the high-temperature creep rupture strength decreases. Therefore, the B content is determined to be 0.005 to 0.015%. For the same reason, the B content is preferably 0.007 to 0.012%.

(13) Re (Rhenium)
Re is an element effective for improving the solid solution amount of W in the matrix as well as strengthening the solid solution by dissolving in the alloy. Re is an element that contributes to maintaining high temperature creep characteristics for a long time by suppressing diffusion of W at high temperature and delaying precipitation of the Laves phase and aggregation coarsening. is there. In order to exhibit these effects, it is preferable to contain Re 0.001% or more. Further, when the Re content is 0.3% or less, these effects can be remarkably exhibited. Therefore, the Re content is determined to be 0.001 to 0.3%. For the same reason, the Re content is preferably 0.001 to 0.25%.

(14) P (phosphorus), S (sulfur)
P and S are classified as inevitable impurities in the heat-resistant steel for steam turbine rotor blades of the embodiment. These inevitable impurities are preferably made to have a residual content as close to 0% as possible.

  The heat-resistant steel for steam turbine rotor blades having the above-described composition component range is suitable as a material constituting the steam turbine rotor blades.

  The heat-resistant steel for steam turbine rotor blades having the above-described composition range is excellent in long-term creep rupture life particularly in a high temperature region. Therefore, a rotor blade used in a high temperature region of 600 ° C. or more, for example, 550 to 650 ° C. It is suitable for the heat-resistant steel to be constructed. Specifically, for example, a moving blade used at a high temperature of 566 to 610 ° C. at the maximum steady-state steam temperature, or a maximum steam temperature at the normal time of 593 to 630 ° C. It is suitable for heat-resistant steel that constitutes moving blades used at high temperatures.

  Here, the heat-resistant steel for steam turbine rotor blades of the embodiment and the method for manufacturing the rotor blades of a steam turbine manufactured using this heat-resistant steel will be described.

  The heat-resistant steel for steam turbine rotor blades of this embodiment is manufactured as follows, for example.

  The raw materials necessary for obtaining the compositional components constituting the heat-resistant steel are melted in a melting furnace such as an arc electric furnace or a vacuum induction electric furnace, and are refined and degassed. Thereafter, the molten metal is poured into a mold of a predetermined size and solidified over time to form a steel ingot. The ingot that has been solidified is heated to 1100 to 1250 ° C., subjected to forging (hot working), and then subjected to quenching and tempering. Through such processes, heat-resistant steel is manufactured.

  The moving blade of the steam turbine is manufactured as follows, for example.

  First, the raw materials necessary for obtaining the composition components constituting the heat-resistant steel constituting the steam turbine rotor blade are melted in a melting furnace such as an arc electric furnace or a vacuum induction electric furnace, and then refined and degassed. I do. Thereafter, the molten metal is poured into a mold of a predetermined size and solidified over time to form a steel ingot. In addition, when pouring in a vacuum environment, since vacuum degassing is performed, the gas component in the steel ingot is further reduced, leading to a reduction in non-metallic inclusions.

  The ingot that has been solidified is heated to 1100 to 1250 ° C. and subjected to forging (hot working) to the shape of the turbine blade by a large press. After the forging process, a quenching process and a tempering process are performed. Through these steps, the turbine blades of the steam turbine are manufactured.

  Here, it is preferable to set the heating temperature in the forging process to a temperature range of 1100 to 1250 ° C. If the temperature is less than 1100 ° C., the hot workability of the material cannot be sufficiently obtained, and the center portion of the turbine blade The forging effect is not sufficient, or may cause forging cracks during forging deformation. When the temperature exceeds 1250 ° C., crystal grain coarsening and crystal grain non-uniformity become significant, This is because deformation due to forging becomes uneven and causes crystal grain coarsening and non-uniformity during the quenching process performed after forging.

  Here, the quenching process and the tempering process will be described.

(Quenching process)
Most of the carbides and carbonitrides generated in the material by quenching heating are once dissolved in the matrix, and then the carbides and carbonitrides are finely and uniformly precipitated in the matrix by subsequent tempering treatment. As a result, the high temperature creep rupture strength can be improved, and the creep rupture ductility and toughness can be improved.

  The quenching temperature is preferably set to a temperature range of 1070 to 1180 ° C. When the quenching temperature is less than 1070 ° C., solid solution of the relatively coarse carbide or carbonitride precipitated by the forging process is not sufficient in the matrix, and coarse undissolved solution after the subsequent tempering treatment. Remains as carbide or non-solid carbonitride. Therefore, it is difficult to obtain good high temperature creep rupture strength, ductility and toughness.

  In the heat-resistant steel according to the embodiment, Nb is added in order to improve the high temperature creep rupture strength by finely depositing MX type carbonitride in the matrix. In order to fully exhibit the effect of Nb, it is necessary to completely dissolve Nb in the austenite matrix when heated to the quenching temperature. However, when the quenching temperature is less than 1070 ° C., Nb remains in an insoluble state as a coarse carbonitride generated during solidification, and the effect of improving the creep rupture strength cannot be sufficiently obtained, and ductility and toughness are not obtained. It may cause a decrease in fatigue strength. In order to dissolve such coarse carbonitrides once and effectively precipitate them in large quantities as fine carbonitrides after quenching, it is necessary to set the quenching temperature to 1070 ° C. or higher.

  On the other hand, when the quenching temperature exceeds 1180 ° C., a δ ferrite phase is generated in the austenite phase, and the crystal grains are coarsened, and the ductility and toughness are greatly reduced.

  In the quenching process, after quenching, the forging material is preferably cooled at a cooling rate of air cooling or higher in order to obtain a predetermined microstructure. As a cooling rate in the quenching treatment, it is more preferable that the quenching is performed at a cooling rate of 100 ° C./hour or more after quenching. As a cooling method for obtaining a cooling rate in this range, for example, oil cooling can be employed.

  The cooling rate described above can be a cooling rate at a portion where the cooling rate is the smallest in the forging material. Moreover, you may define a cooling rate as a cooling rate of the center part of a forge raw material, for example. In this case, the central portion of the forging material refers to the center in the axial direction on the central axis, for example. Further, if the forging material is made of a structure having a predetermined thickness, the central portion of the forging material may be the central portion of the thickness.

(Tempering treatment)
The tempering process decomposes the residual austenite structure generated by the above-described quenching process to form a tempered martensite structure, and uniformly disperses and precipitates carbides and carbonitrides in the matrix and restores the dislocation structure to an appropriate level. . This provides the necessary high temperature creep rupture strength, rupture ductility and toughness.

  This tempering treatment is performed in a temperature range of 670 to 710 ° C. for the purpose of obtaining the necessary high temperature creep rupture strength, fracture ductility and toughness by making the entire material a tempered martensite structure. Is preferred.

  When the temperature of the tempering treatment is less than 670 ° C., precipitates such as carbides and carbonitrides do not precipitate in a stable state, and thus high-temperature creep rupture strength, ductility, and toughness cannot obtain predetermined characteristics. Further, when the temperature of the tempering treatment is less than 670 ° C., the transformation of the quenched martensite structure into the tempered martensite structure does not proceed sufficiently, and the precipitation of carbides and carbonitrides does not sufficiently reach the equilibrium state. Aggregation and coarsening become prominent when creep proceeds at a high temperature exceeding ℃.

  On the other hand, when the temperature of the tempering treatment exceeds 710 ° C., coarse precipitation of carbides and carbonitrides occurs, and the required high temperature creep rupture strength cannot be obtained. When the temperature of the tempering process exceeds 710 ° C., the tempering process proceeds excessively, and the strength characteristics such as tensile strength and proof stress do not satisfy the required values.

  Among the above temperature ranges, particularly when tempering is performed at 670 to 690 ° C., a heat resistant steel exhibiting excellent creep strength under high stress conditions can be obtained and tempered at 690 to 710 ° C. When the treatment is performed, a heat resistant steel exhibiting excellent creep strength under low stress conditions can be obtained. Thus, in the temperature range of 670 to 710 ° C., it is possible to obtain heat resistant steel suitable for the intended use by appropriately selecting the treatment temperature and performing the tempering treatment.

  In the tempering treatment, the forging material is preferably cooled at a cooling rate of 20 to 60 ° C./hour so as not to generate strain in a stress concentration portion such as a shape change portion during cooling.

  The cooling rate in the tempering process can be defined in the same manner as described in the quenching process.

  In addition, the method for producing the moving blade of the steam turbine is not limited to the method described above.

  According to the heat-resistant steel of the above-described embodiment, the creep rupture life can be improved by setting the chemical composition constituting the heat-resistant steel in the above-described range. Wings can be provided. Therefore, by applying this turbine rotor blade, the steam temperature can be increased in the steam turbine, and the power generation efficiency can be improved.

  Below, it demonstrates that the heat resistant steel for steam turbine rotor blades of one embodiment which concerns on this invention is excellent in the high temperature creep rupture life.

(sample)
Table 1 shows chemical composition components of each sample (sample 1 to sample 56) used for the material property evaluation. Samples 1 to 48 are examples of heat-resistant steel for steam turbine blades according to the embodiment of the present invention. Samples 49 to 56 are heat-resistant steel for steam turbine blades of the embodiment according to the present invention. It is a heat resistant steel not in the chemical composition range, and is a comparative example.

  These samples were formed as follows.

  Raw materials constituting each sample were melted in a vacuum induction melting furnace (VIM), degassed, and poured into a mold. And it solidified in the metal mold | die and produced the 20kg steel ingot.

  Subsequently, each solidified ingot was heated to 1200 ° C., and forging was performed at a working ratio of 3 forging ratio. Subsequently, a quenching process and a tempering process were performed.

  Here, the forging ratio refers to the cross-sectional area of the forged object perpendicular to the direction in which the forged object is elongated before the forging process, and the direction in which the forged object is elongated after the forging process. Is divided by the cross-sectional area of the forging object perpendicular to.

  In the quenching treatment, the steel ingot was heated and held at a temperature of 1100 ° C. for 5 hours, and then the steel ingot was cooled at a cooling rate of 100 ° C./hour (cooling rate at the center of the steel ingot). In the tempering process, the steel ingot was heated and held at a temperature of 680 ° C. for 20 hours, and then the steel ingot was cooled at a cooling rate of 50 ° C./hour. Here, the cooling rate after the tempering treatment was the cooling rate at the center of the steel ingot.

(Creep rupture test)
Using the samples 1 to 56 described above, a creep rupture test was performed under the conditions of 625 ° C. and 20 kgf / mm ² . The test piece was produced from each steel ingot described above.

  The creep rupture test was carried out according to JIS Z 2271 (Creep of metal material and creep rupture test method). Table 2 shows the result (creep rupture life) of the creep rupture test for each sample.

  As shown in Table 2, Samples 1 to 48 satisfy the creep rupture life of 10,000 hours or more and have excellent characteristics, but Samples 49 to 56 are greatly inferior in creep rupture life.

(Effect of quenching temperature and tempering temperature)
The effects of quenching and tempering temperatures on creep rupture life were investigated.

  Here, a steel ingot having the composition shown in Sample 1 was used, and quenching and tempering were performed under the following conditions. As quenching temperatures in the quenching treatment, four conditions of 1050 ° C., 1100 ° C., 1150 ° C., and 1200 ° C. were performed, and the respective quenching temperatures were heated and held for 5 hours. After heating and holding for 5 hours, cooling was performed at a cooling rate of 100 ° C./hour (cooling rate at the center of the steel ingot).

  As the tempering temperature in the tempering treatment, four conditions of 650 ° C., 680 ° C., 700 ° C., and 730 ° C. were performed, and each tempering temperature was heated and held for 20 hours. After heating and holding for 20 hours, cooling was performed at a cooling rate of 50 ° C./hour. Here, the cooling rate after the tempering treatment was the cooling rate at the center of the steel ingot.

Then, a test piece is prepared from each steel ingot, a creep rupture test is performed under the conditions of 625 ° C., 20 kgf / mm ² , 650 ° C., and 15 kgf / mm ^{2 in} the same manner as described above, and the creep rupture life is evaluated. did. Table 3 shows the test results of the creep rupture test.

  As shown in Table 3, the creep rupture life of a sample heat-treated at a quenching temperature of 1100 ° C. or 1150 ° C. and a tempering temperature of 680 ° C. or 700 ° C. is compared with a sample heat-treated at other conditions. It is understood that the creep rupture characteristics are excellent.

  Thus, it can be seen that the creep rupture properties are affected by the heat treatment conditions of the quenching treatment and the tempering treatment, and by applying appropriate heat treatment conditions, a heat resistant steel excellent in the creep rupture properties can be obtained.

In addition, those heat-treated at 680 ° C. in the tempering treatment showed particularly excellent characteristics of the creep rupture life under the creep conditions of 625 ° C. and 20 kgf / mm ² . It can be seen that the creep rupture life under a creep condition of 650 ° C. and 15 kgf / mm ² shows particularly excellent characteristics. Therefore, it can be seen that by appropriately selecting the heat treatment conditions, it is possible to obtain a heat-resistant steel having more excellent characteristics suitable for each application.

  According to at least one embodiment described above, it is excellent in high temperature characteristics, durability, etc., and it is possible to improve the long-term creep rupture life.

  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.

Claims (4)

In mass%, C: 0.05 to 0.13%, Si: 0.01 to 0.1%, Mn: more than 0.15% and 0.5% or less, Ni: 0.01 to 0.4% Cr: 9 to 11.5%, Mo: 0.01 to 0.5%, V: 0.15 to 0.3%, Co: 1.5 to 4%, W: 1 to 3%, N: 0.001 to less than 0.01%, Nb: 0.01 to 0.15%, B: 0.005 to 0.015%, Re: 0.001 to 0.3%, the balance being Fe and Heat-resistant steel for steam turbine blades, which consists of inevitable impurities.   The heat-resistant steel for steam turbine rotor blades according to claim 1, wherein the quenching temperature is 1070 to 1180 ° C, and the tempering treatment temperature is 670 to 710 ° C.   The heat-resistant steel for steam turbine rotor blades according to claim 1 or 2, wherein a cooling rate after the quenching is set to 100 ° C / hour or more.   A steam turbine rotor blade produced using the heat-resistant steel for steam turbine rotor blades according to claim 1.