JP2012036485A - Ni-BASED ALLOY FOR FORGED PART IN STEAM-TURBINE AND FORGED PART IN STEAM-TURBINE - Google Patents

Ni-BASED ALLOY FOR FORGED PART IN STEAM-TURBINE AND FORGED PART IN STEAM-TURBINE Download PDF

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JP2012036485A
JP2012036485A JP2010180080A JP2010180080A JP2012036485A JP 2012036485 A JP2012036485 A JP 2012036485A JP 2010180080 A JP2010180080 A JP 2010180080A JP 2010180080 A JP2010180080 A JP 2010180080A JP 2012036485 A JP2012036485 A JP 2012036485A
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steam turbine
steam
based alloy
turbine
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JP5525961B2 (en
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Shigekazu Miyashita
重和 宮下
Kiyoshi Imai
潔 今井
Hiroaki Yoshioka
洋明 吉岡
Kuniyoshi Nemoto
邦義 根本
Shogo Iwai
章吾 岩井
Takeo Suga
威夫 須賀
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Toshiba Corp
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Abstract

PROBLEM TO BE SOLVED: To provide an Ni-based alloy for forged parts in a steam-turbine excellent in high-temperature strength and castability and to provide the forged parts in the steam-turbine produced using the Ni-based alloy for forged parts of the steam turbine.SOLUTION: The Ni-based alloy for forged parts in the steam-turbine is composed, by mass, of 0.01-0.15% C, 14-20% Cr, 10-15% Co, 8-12% Mo, 0.5-4% Al, 0.5-4% Ti, 0.001-0.006% B, 0.1-0.7% Ta, 0.1-0.4% Nb, and the balance Ni with inevitable impurities. A relationship of 9.5 mass%≤0.45Cr+Al+Ti≤13 mass% is satisfied.

Description

本発明の実施形態は、鍛造性等に優れた、蒸気タービンの鍛造部品用Ni基合金および蒸気タービンの鍛造部品に関する。   Embodiments of the present invention relate to a Ni-based alloy for forged parts of a steam turbine and a forged part of a steam turbine that are excellent in forgeability and the like.

石炭火力発電設備から排出されるCOを削減する手段として、石炭火力システムの高効率化を図ることが有効な手段であり、例えば、石炭火力発電設備に備えられている蒸気タービンの発電効率を向上させることで実現可能となる。蒸気タービンの発電効率の向上には、タービン蒸気温度を高温化することが最も効果的である。近年の火力発電プラントにおいて、その蒸気温度は600℃以上まで上昇しており、現在、蒸気温度が700℃以上の火力発電システムの開発が世界的に行われている。 As a means for reducing CO 2 emitted from coal-fired power generation equipment, it is effective to improve the efficiency of the coal-fired power generation system. For example, the power generation efficiency of the steam turbine provided in the coal-fired power generation equipment is improved. It can be realized by improving. To improve the power generation efficiency of the steam turbine, it is most effective to raise the turbine steam temperature. In recent thermal power plants, the steam temperature has risen to 600 ° C. or higher, and currently, thermal power generation systems having a steam temperature of 700 ° C. or higher are being developed worldwide.

高温の蒸気に曝される蒸気タービンが備える、タービンロータ、動翼および静翼などの鍛造部品や、蒸気タービンに使用される、ボルトなどの螺合部材および配管などの鍛造部品は、高温になるとともに、高い応力が発生する。そのため、これらを構成する材料として、室温から高温の温度領域まで、優れた、強度、延性、靭性を有するものが求められている。   Forged parts such as turbine rotors, moving blades and stationary blades provided in steam turbines exposed to high-temperature steam, and forged parts such as bolted members and pipes used in steam turbines become high temperature. At the same time, high stress is generated. Therefore, materials having excellent strength, ductility, and toughness are demanded from the room temperature to a high temperature range as materials constituting them.

現在、蒸気タービンを構成する構成部品に使用されている材料は、Feを主成分とし、高温強度を向上させるためにCr、Mo等の元素を添加したFe基合金である。しかしながら、蒸気の温度が700℃以上となると、Fe基合金の耐熱温度を超えるため、さらに耐熱温度が高いNi基合金の適用が検討されている。   The material currently used for the components constituting the steam turbine is an Fe-based alloy containing Fe as a main component and added with elements such as Cr and Mo in order to improve high-temperature strength. However, when the temperature of the steam is 700 ° C. or higher, the heat resistance temperature of the Fe-based alloy is exceeded, so application of a Ni-based alloy having a higher heat resistance temperature is being studied.

Ni基合金の代表例として、インコネル718合金(スペシャルメタル社製)やインコネル617合金(スペシャルメタル社製)が挙げられる。Ni基合金の強化機構は、大きく分けて析出強化型と固溶強化型に分けられる。析出強化型Ni基合金では、NiにAl、Ti、Ta、Nbを添加することによってγ’(ガンマプライム:Ni(Al,Ti))相、あるいはγ”(ガンマダブルプライム:NiNb)相 と呼ばれる析出相を析出させることによって高温での強度を向上させている。代表的な析出強化型Ni基合金としては、上記したインコネル718合金が挙げられる。一方、固溶強化型Ni基合金では、NiにCo、Mo等を添加することによって、母相そのものを強化している。代表的な固溶強化型Ni基合金としては、上記したインコネル617合金が挙げられる。 Typical examples of Ni-based alloys include Inconel 718 alloy (made by Special Metal) and Inconel 617 alloy (made by Special Metal). The strengthening mechanism of the Ni-based alloy is roughly divided into a precipitation strengthening type and a solid solution strengthening type. In a precipitation strengthened Ni-base alloy, by adding Al, Ti, Ta, Nb to Ni, a γ ′ (gamma prime: Ni 3 (Al, Ti)) phase or γ ″ (gamma double prime: Ni 3 Nb) The strength at high temperature is improved by precipitating a precipitation phase called “phase.” As a typical precipitation strengthened Ni-based alloy, the above-mentioned Inconel 718 alloy can be cited, while solid solution strengthened Ni-based alloy. Then, the matrix phase itself is strengthened by adding Co, Mo, etc. to Ni. A typical solid solution strengthened Ni-based alloy includes the above-mentioned Inconel 617 alloy.

特開平7−150277号公報Japanese Unexamined Patent Publication No. 7-150277

上記したように、700℃を超える蒸気環境下において使用される、蒸気タービンの構成部品の材料として、Ni基合金の適用が検討されている。蒸気タービンの構成部品の材料において、700℃を超える蒸気環境下における十分な高温強度が要求され、さらに、高温に長時間曝されるため、長時間に渡る材料の健全性が要求される。   As described above, application of a Ni-based alloy has been studied as a material for components of steam turbines used in a steam environment exceeding 700 ° C. The material of the components of the steam turbine is required to have a sufficiently high temperature strength in a steam environment exceeding 700 ° C. Further, since it is exposed to a high temperature for a long time, the soundness of the material for a long time is required.

また、蒸気タービンの構成部品が、接合、締結または嵌め込みなどの接続部を備える場合、この接続部において、接続部を構成する材料の熱膨張差に起因した熱応力が発生する。   Moreover, when the component of a steam turbine is provided with connection parts, such as joining, fastening, or fitting, in this connection part, the thermal stress resulting from the thermal expansion difference of the material which comprises a connection part generate | occur | produces.

そこで、本発明は、高温強度特性および鍛造性に優れた蒸気タービンの鍛造部品用Ni基合金、この蒸気タービンの鍛造部品用Ni基合金を用いて作製された蒸気タービンの鍛造部品を提供することを目的とする。   Accordingly, the present invention provides a Ni-based alloy for steam turbine forged parts excellent in high-temperature strength characteristics and forgeability, and a steam turbine forged part manufactured using the Ni-based alloy for steam turbine forged parts. With the goal.

本発明の実施形態の蒸気タービンの鍛造部品用Ni基合金は、質量%で、C:0.01〜0.15、Cr:14〜20、Co:10〜15、Mo:8〜12、Al:0.5〜4、Ti:0.5〜4、B:0.001〜0.006、Ta:0.1〜0.7、Nb:0.1〜0.4、残部がNiおよび不可避的不純物からなり、かつ9.5質量%≦0.45Cr+Al+Ti≦13質量%の関係を満たすことを特徴とする。   The Ni-based alloy for forged parts of steam turbines according to an embodiment of the present invention is in mass%, C: 0.01 to 0.15, Cr: 14 to 20, Co: 10 to 15, Mo: 8 to 12, Al : 0.5-4, Ti: 0.5-4, B: 0.001-0.006, Ta: 0.1-0.7, Nb: 0.1-0.4, the balance is Ni and inevitable And 9.5% by mass ≦ 0.45Cr + Al + Ti ≦ 13% by mass.

熱力学計算によって得られた、700℃におけるσ相の析出領域を示す図である。It is a figure which shows the precipitation area | region of the (sigma) phase in 700 degreeC obtained by the thermodynamic calculation.

以下、本発明に係る実施形態を説明する。   Embodiments according to the present invention will be described below.

Co、Moを添加することにより、Ni基の母相を強化(固溶強化)して高温強度の向上が図られた、例えばインコネル617合金において、Al、Ti、TaおよびNbを添加し、高温で安定な金属間化合物であるγ’(Ni(Al,Ti))相を析出させることで、高温強度をさらに向上させることができる。しかしながら、強化元素の過剰な添加は、組織の安定性を悪化させ、機械的特性の低下を引き起こすTCP(Topologically Close-Packed)相の析出を助長する。
本発明に係る実施形態では、TCP相の一つであるσ相の主成分であるCrに着目し、弱化を引き起こす有害相の析出を抑制しつつ、γ’相の析出に寄与するAlおよびTiの添加によって、高温強度の向上を図ったものである。
For example, in Inconel 617 alloy, Al, Ti, Ta, and Nb are added and high temperature strength is improved by strengthening (solid solution strengthening) the Ni-based matrix by adding Co and Mo. By precipitating a γ ′ (Ni 3 (Al, Ti)) phase that is a stable intermetallic compound, the high-temperature strength can be further improved. However, excessive addition of strengthening elements promotes the precipitation of a TCP (Topologically Close-Packed) phase that deteriorates the stability of the structure and causes deterioration of mechanical properties.
In the embodiment according to the present invention, focusing on Cr, which is a main component of the σ phase that is one of the TCP phases, Al and Ti that contribute to the precipitation of the γ ′ phase while suppressing the precipitation of the harmful phase causing the weakening. The high temperature strength is improved by the addition of.

以下、その詳細を説明する。
例えば、従来のインコネル617にAl、Tiを複合添加すると、析出するγ’相量は増加し、クリープ強度は向上するが、過剰量添加することによって母相のCr濃度が濃化し、板状あるいは針状のσ相の析出が促進され、機械的特性が低下する。
Details will be described below.
For example, when Al and Ti are added in combination to conventional Inconel 617, the amount of precipitated γ ′ phase is increased and the creep strength is improved. Precipitation of acicular σ phase is promoted and mechanical properties are deteriorated.

図1は、熱力学計算によって得られた、700℃におけるσ相の析出領域を示す図である。なお、図1において、横軸は、Crの含有量(質量%)、縦軸は、Alの含有量(質量%)とTiの含有量(質量%)を合計した含有量(以下、AlとTiの含有量という)を示している。また、図1において示されたラインLよりも上の領域は、σ相が析出する領域であり、ラインLよりも下の領域は、σ相が析出しない領域である。また、図1に示したNi基合金における、Cr、AlおよびTi以外の組成成分は、質量%で、Cが0.05、Coが12.5、Moが9、Bが0.003、Taが0.1、Nbが0.3、残部がNiおよび不可避的不純物からなる。   FIG. 1 is a diagram showing the precipitation region of the σ phase at 700 ° C. obtained by thermodynamic calculation. In FIG. 1, the horizontal axis represents the Cr content (mass%), and the vertical axis represents the total content of Al (mass%) and Ti (mass%) (hereinafter, Al and Ti content). Further, the region above the line L shown in FIG. 1 is a region where the σ phase is precipitated, and the region below the line L is a region where the σ phase is not precipitated. In the Ni-based alloy shown in FIG. 1, the composition components other than Cr, Al, and Ti are mass%, C is 0.05, Co is 12.5, Mo is 9, B is 0.003, Ta 0.1, Nb 0.3, the balance being Ni and inevitable impurities.

図1に示すように、Crの含有量が増加するに伴って、σ相が析出しない領域におけるAlとTiの含有量の範囲が狭くなる。このような結果に基づいて、Crの含有量と、AlとTiの含有量とを調整し、図1において示されたラインL上、またはその近傍となる領域で、γ’相を最大限析出させることで、組織安定性と高温強度の向上を図ることができる。   As shown in FIG. 1, as the Cr content increases, the range of the Al and Ti content in the region where the σ phase does not precipitate becomes narrower. Based on such results, the Cr content and the Al and Ti contents are adjusted, and the γ ′ phase is precipitated to the maximum in the region on or near the line L shown in FIG. By doing so, it is possible to improve the tissue stability and the high temperature strength.

上記した、熱力学計算によって得られた、ラインL、Crの含有量、およびAlとTiの含有量の関係を考慮して、本発明に係る実施形態における蒸気タービンの鍛造部品用Ni基合金に発明に至った。   In consideration of the relationship between the contents of lines L and Cr and the contents of Al and Ti obtained by thermodynamic calculation, the Ni-based alloy for forged parts of a steam turbine in the embodiment according to the present invention is used. Invented.

本発明に係る実施形態における蒸気タービンの鍛造部品用Ni基合金は、以下に示す組成成分範囲で構成される。なお、以下の説明において組成成分を表す%は、特に明記しない限り質量%とする。   The Ni-based alloy for forged parts of a steam turbine in the embodiment according to the present invention is composed of the following composition component ranges. In the following description, “%” representing a composition component is “% by mass” unless otherwise specified.

本発明に係る実施形態における蒸気タービンの鍛造部品用Ni基合金は、C:0.01〜0.15、Cr:14〜20、Co:10〜15、Mo:8〜12、Al:0.5〜4、Ti:0.5〜4、B:0.001〜0.006、Ta:0.1〜0.7、Nb:0.1〜0.4、残部がNiおよび不可避的不純物からなり、かつ9.5質量%≦0.45Cr+Al+Ti≦13質量%の関係を満たすNi基合金である。   Ni-based alloys for forged parts of steam turbines according to embodiments of the present invention are: C: 0.01 to 0.15, Cr: 14 to 20, Co: 10 to 15, Mo: 8 to 12, Al: 0.00. 5-4, Ti: 0.5-4, B: 0.001-0.006, Ta: 0.1-0.7, Nb: 0.1-0.4, the balance from Ni and inevitable impurities And a Ni-based alloy satisfying the relationship of 9.5% by mass ≦ 0.45Cr + Al + Ti ≦ 13% by mass.

また、上記した不可避的不純物において、その不可避的不純物のうち、少なくとも、Siが0.1%以下、Mnが0.1%以下に抑制されていることが好ましい。なお、不可避的不純物としては、上記した、SiおよびMnの他に、例えば、Cu、FeおよびSなどが挙げられる。   In the inevitable impurities described above, it is preferable that at least Si is suppressed to 0.1% or less and Mn is suppressed to 0.1% or less among the inevitable impurities. In addition, as an unavoidable impurity, Cu, Fe, S etc. are mentioned other than Si and Mn mentioned above, for example.

上記した本発明に係る実施形態のNi基合金は、運転時の温度が680〜750℃となる蒸気タービンの鍛造部品を構成する材料として好適である。蒸気タービンの鍛造部品として、例えば、蒸気タービンのタービンロータ、蒸気タービンの動翼、蒸気タービンの静翼、蒸気タービン用螺合部材、蒸気タービン用配管などが挙げられる。これらの蒸気タービンの鍛造部品は、いずれも高温高圧の環境に設置されるものである。   The above-described Ni-based alloy according to the embodiment of the present invention is suitable as a material constituting a forged part of a steam turbine having a temperature during operation of 680 to 750 ° C. Examples of the forged parts of the steam turbine include a turbine rotor of the steam turbine, a moving blade of the steam turbine, a stationary blade of the steam turbine, a screwed member for the steam turbine, and a pipe for the steam turbine. All of these steam turbine forged parts are installed in a high-temperature and high-pressure environment.

ここで、蒸気タービン用螺合部材として、例えば、タービンケーシングやタービン内部の各種構成部品を固定するボルトやナットなどを例示することができる。また、蒸気タービン用配管として、例えば、蒸気タービンプラントなどに設置され、蒸気タービンに高温高圧の蒸気を供給する配管や、蒸気タービン内部の配管などを例示することができる。蒸気タービン用配管として、具体的には、例えば、ボイラからの蒸気を高圧タービンに導く主蒸気管や、ボイラ再熱器からの蒸気を中圧タービンに導く高温再熱蒸気管などを例示することができる。さらに、蒸気タービン用配管として、蒸気タービンに導入された高温高圧の蒸気をノズルボックスに導く主蒸気導入管などを例示することができる。なお、蒸気タービン用配管は、これらに限定されるものではなく、例えば、温度が680〜750℃の蒸気が流動する配管なども含まれる。   Here, as the screwing member for the steam turbine, for example, a bolt or a nut for fixing various components inside the turbine casing or the turbine can be exemplified. Further, examples of the steam turbine piping include piping installed in a steam turbine plant and the like for supplying high-temperature and high-pressure steam to the steam turbine, piping inside the steam turbine, and the like. Specific examples of steam turbine piping include, for example, a main steam pipe that guides steam from a boiler to a high-pressure turbine, and a high-temperature reheat steam pipe that guides steam from a boiler reheater to an intermediate-pressure turbine. Can do. Furthermore, examples of the steam turbine pipe include a main steam introduction pipe that guides high-temperature and high-pressure steam introduced into the steam turbine to the nozzle box. Note that the steam turbine piping is not limited to these, and includes, for example, piping through which steam having a temperature of 680 to 750 ° C. flows.

なお、上記した蒸気タービンの鍛造部品のすべての部位を上記したNi基合金で構成しても、また、特に高温となる蒸気タービンの鍛造部品の一部の部位を上記したNi基合金で構成してもよい。ここで、蒸気タービンの鍛造部品が高温となる領域として、具体的には、例えば、高圧蒸気タービン部の全領域、または高圧蒸気タービン部から中圧蒸気タービン部の一部分までの領域などが挙げられる。さらに、蒸気タービンの鍛造部品が高温となる領域として、上記した高温高圧の蒸気を各種蒸気タービンに導く、主蒸気管や高温再熱蒸気管などの配管部が挙げられる。なお、蒸気タービンの鍛造部品が高温となる部分は、これらに限られるものではなく、例えば、温度が680〜750℃程度となる部分であればこれに含まれる。   Even if all the parts of the forged parts of the steam turbine described above are composed of the Ni-based alloy described above, some parts of the forged parts of the steam turbine that are particularly hot are composed of the Ni-based alloy described above. May be. Here, as the region where the forged part of the steam turbine becomes high temperature, specifically, for example, the entire region of the high-pressure steam turbine unit or the region from the high-pressure steam turbine unit to a part of the intermediate-pressure steam turbine unit, etc. . Furthermore, examples of the region where the forged parts of the steam turbine are heated include piping sections such as a main steam pipe and a high-temperature reheat steam pipe that guide the above-described high-temperature and high-pressure steam to various steam turbines. In addition, the part from which the forge components of a steam turbine become high temperature is not restricted to these, For example, if it is a part from which temperature becomes about 680-750 degreeC, it will be contained in this.

また、上記した蒸気タービンの鍛造部品において、鍛造部品どうしを接合、締結または嵌め込む接続部を備える場合、それぞれの鍛造部品の少なくとも接続部を本発明に係る実施形態のNi基合金で構成することで、異なる合金の組み合わせの場合と比較して、熱膨張差に起因する熱応力を低減させることができる。このような蒸気タービンの鍛造部品の組み合わせとして、具体的には、例えば、動翼と、この動翼が植設されるタービンロータなどが挙げられる。   In addition, in the forged parts of the steam turbine described above, when the connecting parts for joining, fastening, or fitting the forged parts are provided, at least the connecting parts of the respective forged parts should be composed of the Ni-based alloy according to the embodiment of the present invention. Thus, it is possible to reduce the thermal stress due to the difference in thermal expansion as compared with the case of a combination of different alloys. Specific examples of such combinations of forged parts of the steam turbine include a moving blade and a turbine rotor in which the moving blade is implanted.

また、上記した本発明に係る実施形態のNi基合金は、従来のNi基合金よりも高温強度特性に優れ、かつ鍛造性に優れている。すなわち、このNi基合金を用いて、蒸気タービンのタービンロータ、蒸気タービンの動翼、蒸気タービンの静翼、蒸気タービン用螺合部材、蒸気タービン用配管などの蒸気タービンの鍛造部品を構成することで、高温環境下においても高い信頼性を有する、蒸気タービンのタービンロータ、蒸気タービンの動翼、蒸気タービンの静翼、蒸気タービン用螺合部材、蒸気タービン用配管などの鍛造部品を作製することができる。   In addition, the Ni-based alloy according to the embodiment of the present invention described above is superior in high-temperature strength characteristics and superior in forgeability than conventional Ni-based alloys. That is, using this Ni-based alloy, forging parts of a steam turbine such as a turbine rotor of a steam turbine, a moving blade of a steam turbine, a stationary blade of a steam turbine, a threaded member for a steam turbine, and a pipe for a steam turbine are configured. Therefore, forging parts such as a turbine rotor of a steam turbine, a moving blade of a steam turbine, a stationary blade of a steam turbine, a threaded member for a steam turbine, and a pipe for a steam turbine having high reliability even in a high temperature environment. Can do.

次に、上記した本発明に係る実施形態のNi基合金における各組成成分範囲の限定理由を説明する。   Next, the reason for limitation of each composition component range in the Ni-based alloy according to the embodiment of the present invention described above will be described.

(1)C(炭素)
Cは、強化相である炭化物の構成元素として有用であるとともに、結晶粒界の移動を阻止する、炭化物のピン止め効果によって、高温下における結晶粒の粗大化を抑制する働きがある。Cの含有率が0.01未満の場合には、炭化物による強化が十分でないとともに、炭化物の十分な析出量を確保できないことにより、結晶粒の粗大化を引き起こす恐れがある。一方、Cの含有率が0.15%を超えると、鍛造性が低下する。そのため、Cの含有率を0.01〜0.15%とした。
(1) C (carbon)
C is useful as a constituent element of the carbide that is the strengthening phase, and also has a function of suppressing the coarsening of the crystal grains at a high temperature by the pinning effect of the carbide that prevents the movement of the crystal grain boundary. When the C content is less than 0.01, strengthening with carbides is not sufficient, and a sufficient amount of precipitation of carbides cannot be secured, which may cause coarsening of crystal grains. On the other hand, if the C content exceeds 0.15%, the forgeability decreases. Therefore, the C content is determined to be 0.01 to 0.15%.

(2)Cr(クロム)
Crは、Ni基合金の耐酸化性、耐食性および高温強度特性を高めるのに不可欠な元素である。Crの含有率が14%未満の場合には、耐酸化性および耐食性が低下する。一方、Crの含有率が20%を超えると、σ相の析出が誘起され、衝撃値、クリープ特性、低サイクル疲労寿命などの機械的特性が悪化する。そのため、Crの含有率を14〜20%とした。
(2) Cr (chromium)
Cr is an essential element for enhancing the oxidation resistance, corrosion resistance and high temperature strength characteristics of the Ni-based alloy. When the Cr content is less than 14%, the oxidation resistance and the corrosion resistance decrease. On the other hand, if the Cr content exceeds 20%, precipitation of the σ phase is induced, and mechanical properties such as impact value, creep properties, and low cycle fatigue life are deteriorated. Therefore, the Cr content is determined to be 14 to 20%.

(3)Co(コバルト)
Coは、Ni基合金において、母相内に固溶し、クリープ強度および引張強度を向上させる。Coの含有率が10%未満の場合には、十分な機械的強度が得られない。一方、Coの含有率が15%を超えると、鍛造性が低下する。そのため、Coの含有率を10〜15%とした。
(3) Co (cobalt)
Co dissolves in the matrix phase in a Ni-based alloy, and improves the creep strength and tensile strength. If the Co content is less than 10%, sufficient mechanical strength cannot be obtained. On the other hand, if the Co content exceeds 15%, the forgeability decreases. Therefore, the Co content is determined to be 10 to 15%.

(4)Mo(モリブデン)
Moは、Ni母相中に固溶し、クリープ強度および引張強度を向上させる効果を有し、また、M23型炭化物中に一部が置換することによって炭化物の安定性を高める。Moの含有率が12%を超えると、σ相の析出による機械的強度の低下が顕著になる。一方、Moの含有率が8%未満の場合には、機械的強度の向上が得られない。そのため、Moの含有率を8〜12%とした。
(4) Mo (molybdenum)
Mo dissolves in the Ni matrix and has the effect of improving the creep strength and tensile strength, and also increases the stability of the carbide by partially replacing the M 23 C 6 type carbide. When the Mo content exceeds 12%, the mechanical strength is significantly lowered due to precipitation of the σ phase. On the other hand, when the Mo content is less than 8%, the mechanical strength cannot be improved. Therefore, the Mo content is determined to be 8 to 12%.

(5)Al(アルミニウム)
Alは、Niとともにγ’(NiAl)相を生成し、析出によるNi基合金の機械的強度を向上させる。Alの含有率が0.5%未満の場合には、Ni母相に完全に固溶するため、γ’相の析出による効果が発揮されない。一方、Alの含有率が4%を超えると、σ相の析出が助長され、機械的特性が低下するとともに、γ’相の固溶温度が上昇するため、熱間加工性が著しく低下する。そのため、Alの含有率を0.5〜4%とした。
(5) Al (aluminum)
Al forms a γ ′ (Ni 3 Al) phase together with Ni, and improves the mechanical strength of the Ni-based alloy by precipitation. When the Al content is less than 0.5%, the effect of precipitation of the γ ′ phase is not exhibited because it is completely dissolved in the Ni matrix. On the other hand, when the Al content exceeds 4%, precipitation of the σ phase is promoted, the mechanical properties are lowered, and the solid solution temperature of the γ ′ phase is raised, so that the hot workability is significantly lowered. Therefore, the Al content is determined to be 0.5 to 4%.

(6)Ti(チタン)
Tiは、Alと同様、Niとともにγ’(NiTi)相を生成し、Ni基合金の機械的強度を向上させる。Tiの含有率が0.5%未満の場合には、γ’相の析出による効果が発揮されない。一方、Tiの含有率が4%を超えると、σ相の析出が助長され、機械的特性が低下するとともに、γ’相の固溶温度が上昇するため熱間加工性が著しく低下する。そのため、Tiの含有率を0.5〜4%とした。
(6) Ti (titanium)
Ti, like Al, produces a γ ′ (Ni 3 Ti) phase together with Ni, and improves the mechanical strength of the Ni-based alloy. When the Ti content is less than 0.5%, the effect of precipitation of the γ ′ phase is not exhibited. On the other hand, if the Ti content exceeds 4%, precipitation of the σ phase is promoted, the mechanical properties are lowered, and the solid solution temperature of the γ ′ phase is raised, so that the hot workability is remarkably lowered. Therefore, the Ti content is determined to be 0.5 to 4%.

(7)B(ホウ素)
Bは、粒界に偏析して高温強度特性を向上させる。Bの含有率が0.001%未満の場合には、この高温強度特性を向上させる効果が発揮されない。一方、Bの含有率が0.006%を超えると、粒界脆化を招く。そのため、Bの含有率を0.001〜0.006%とした。
(7) B (boron)
B segregates at the grain boundaries and improves the high temperature strength characteristics. When the B content is less than 0.001%, the effect of improving the high temperature strength characteristics is not exhibited. On the other hand, if the B content exceeds 0.006%, grain boundary embrittlement is caused. Therefore, the B content is determined to be 0.001 to 0.006%.

(8)Ta(タンタル)
Taは、γ’(Ni(Al,Ti))相に固溶して、このγ’相の析出強度を安定させる。Taの含有率が0.1%未満の場合には、上記した効果において従来鋼と比べて向上がみられず、Taの含有率が0.7%を超えると、鍛造性が低下する。そのため、Taの含有率を0.1〜0.7%とした。
(8) Ta (tantalum)
Ta dissolves in the γ ′ (Ni 3 (Al, Ti)) phase and stabilizes the precipitation strength of the γ ′ phase. When the Ta content is less than 0.1%, the above effect is not improved as compared with the conventional steel. When the Ta content exceeds 0.7%, the forgeability decreases. Therefore, the Ta content is determined to be 0.1 to 0.7%.

(9)Nb(ニオブ)
Nbは、Taと同様に、γ’(Ni(Al,Ti))相に固溶して、このγ’相の析出強度を安定させる。Nbの含有率が0.1%未満の場合には、上記した効果において従来鋼と比べて向上がみられず、Nbの含有率が0.4%を超えると、溶解や鋳造時において偏析を招く。そのため、Nbの含有率を0.1〜0.4%とした。
(9) Nb (Niobium)
Nb, like Ta, dissolves in the γ ′ (Ni 3 (Al, Ti)) phase and stabilizes the precipitation strength of the γ ′ phase. When the Nb content is less than 0.1%, the above effects are not improved as compared with the conventional steel. When the Nb content exceeds 0.4%, segregation occurs during melting and casting. Invite. Therefore, the Nb content is determined to be 0.1 to 0.4%.

(10)Si(ケイ素)、Mn(マンガン)、Cu(銅)、Fe(鉄)およびS(硫黄)
Si、Mn、Cu、FeおよびSは、本発明に係る実施形態のNi基合金においては、不可避的不純物に分類されるものである。これらの不可避的不純物は、可能な限りその残存含有率を0%に近づけることが望ましい。また、これらの不可避的不純物のうち、少なくとも、SiおよびMnは、0.1%以下に抑制されることが好ましい。
(10) Si (silicon), Mn (manganese), Cu (copper), Fe (iron) and S (sulfur)
Si, Mn, Cu, Fe and S are classified as inevitable impurities in the Ni-based alloy according to the embodiment of the present invention. It is desirable that the residual content of these inevitable impurities is as close to 0% as possible. Of these inevitable impurities, at least Si and Mn are preferably suppressed to 0.1% or less.

Siは、普通鋼の場合、耐食性を補うため添加される。しかしながら、Ni基合金はCr含有量が多く、十分に耐食性を確保できることから、本発明に係る実施形態のNi基合金では、Siの残存含有率を0.1%以下とし、可能な限りその残存含有率を0%に近づけることが望ましい。   In the case of plain steel, Si is added to supplement the corrosion resistance. However, since the Ni-based alloy has a high Cr content and can sufficiently secure corrosion resistance, the Ni-based alloy of the embodiment according to the present invention has a residual content of Si of 0.1% or less, and the residual content is as much as possible. It is desirable to bring the content closer to 0%.

Mnは、普通鋼の場合、脆性に起因するS(硫黄)をMnSとして脆性を防止する。しかしながら、Ni基合金におけるSの含有量は極めて少なく、Mnを添加する必要はない。そのため、本発明に係る実施形態のNi基合金では、Mnの残存含有率を0.1%以下とし、可能な限りその残存含有率を0%に近づけることが望ましい。   In the case of ordinary steel, Mn prevents brittleness by using S (sulfur) due to brittleness as MnS. However, the content of S in the Ni-based alloy is extremely small, and it is not necessary to add Mn. Therefore, in the Ni-based alloy of the embodiment according to the present invention, it is desirable that the residual content of Mn is 0.1% or less and that the residual content is as close to 0% as possible.

(11)0.45Cr+Al+Ti
上記した図1において、σ相が析出する領域と、σ相が析出しない領域との境界線であるラインLは、Crの含有量(質量%)と、AlとTiの含有量(質量%)との関係式(0.45Cr+Al+Ti=10.5質量%)によって示される。そして、0.45Cr+Al+Tiの値が10.5以下の場合、σ相の析出を完全に防ぐことができるが、0.45Cr+Al+Tiの値が9.5を下回ると、十分なγ’相の析出が得られず、機械的特性の向上する効果が小さくなる。
(11) 0.45Cr + Al + Ti
In FIG. 1 described above, the line L, which is the boundary line between the region where the σ phase precipitates and the region where the σ phase does not precipitate, is the Cr content (mass%) and the Al and Ti contents (mass%). (0.45Cr + Al + Ti = 10.5% by mass). When the value of 0.45Cr + Al + Ti is 10.5 or less, the precipitation of the σ phase can be completely prevented, but when the value of 0.45Cr + Al + Ti is less than 9.5, sufficient precipitation of the γ ′ phase is obtained. In other words, the effect of improving the mechanical characteristics is reduced.

一方、ラインLよりも上の領域である、σ相が析出する領域であっても、0.45Cr+Al+Tiの値が13以下の場合には、σ相が析出しても、機械的特性が低下することはない。また、0.45Cr+Al+Tiの値が13を超えると、σ相の析出量が増加し、機械的特性の低下が顕著となる。そのため、0.45Cr+Al+Tiを9.5〜13質量%の範囲とした。   On the other hand, even in the region above the line L where the σ phase precipitates, when the value of 0.45Cr + Al + Ti is 13 or less, the mechanical characteristics are degraded even if the σ phase is precipitated. There is nothing. On the other hand, when the value of 0.45Cr + Al + Ti exceeds 13, the amount of precipitation of the σ phase increases, and the mechanical properties are significantly deteriorated. Therefore, 0.45Cr + Al + Ti was made into the range of 9.5-13 mass%.

ここで、本発明に係る実施形態の蒸気タービンの鍛造部品用Ni基合金、およびこの鍛造部品用Ni基合金を用いて製造される蒸気タービンの鍛造部品の製造方法について説明する。   Here, a Ni-based alloy for a forged part of a steam turbine according to an embodiment of the present invention and a method for manufacturing a forged part of a steam turbine manufactured using the Ni-based alloy for a forged part will be described.

上記した本発明に係る実施形態の蒸気タービンの鍛造部品用Ni基合金は、例えば、Ni基合金を構成する組成成分を真空誘導溶解(VIM)し、その溶湯を所定の型枠に注入して鋳塊を形成し、その鋳塊をソーキング処理し、圧延などによって鍛造し、溶体化処理、時効処理などを施すことで作製される。   The above-described Ni-based alloy for forged parts of a steam turbine according to an embodiment of the present invention includes, for example, vacuum induction melting (VIM) of composition components constituting the Ni-based alloy and injecting the molten metal into a predetermined mold. An ingot is formed, the ingot is soaked, forged by rolling or the like, and subjected to a solution treatment, an aging treatment, or the like.

また、本発明に係る実施形態の鍛造部品である蒸気タービンのタービンロータは、例えば次のように作製される。   Moreover, the turbine rotor of the steam turbine which is a forged part of embodiment which concerns on this invention is produced as follows, for example.

例えば、1つの方法(ダブルメルト)として、本発明に係る実施形態の蒸気タービンの鍛造部品用Ni基合金を構成する組成成分を真空誘導溶解(VIM)し、エレクトロスラグ再溶解(ESR)し、所定の型に流し込む。続いて、ソーキング処理、鍛造処理、溶体化処理、時効処理などを施しタービンロータを作製する。   For example, as one method (double melt), vacuum induction melting (VIM) and electroslag remelting (ESR) are performed on the composition components constituting the Ni-based alloy for forged parts of the steam turbine according to the embodiment of the present invention, Pour into a predetermined mold. Subsequently, a soaking process, a forging process, a solution treatment, an aging process, and the like are performed to produce a turbine rotor.

他の方法(ダブルメルト)として、本発明に係る実施形態の蒸気タービンの鍛造部品用Ni基合金を構成する組成成分を真空誘導溶解(VIM)し、真空アーク再溶解(VAR)し、所定の型に流し込む。続いて、ソーキング処理、鍛造処理、溶体化処理、時効処理などを施しタービンロータを作製する。   As another method (double melt), the composition components constituting the Ni-based alloy for forged parts of the steam turbine according to the embodiment of the present invention are vacuum induction melted (VIM), vacuum arc remelted (VAR), predetermined Pour into the mold. Subsequently, a soaking process, a forging process, a solution treatment, an aging process, and the like are performed to produce a turbine rotor.

さらに、他の方法(トリプルメルト)として、本発明に係る実施形態の蒸気タービンの鍛造部品用Ni基合金を構成する組成成分を真空誘導溶解(VIM)し、エレクトロスラグ再溶解(ESR)し、真空アーク再溶解(VAR)し、所定の型に流し込む。続いて、ソーキング処理、鍛造処理、溶体化処理、時効処理などを施しタービンロータを作製する。なお、上記方法によって作製されたタービンロータは、超音波検査等が行われる。   Furthermore, as another method (triple melt), the composition components constituting the Ni-based alloy for forged parts of the steam turbine according to the embodiment of the present invention are vacuum induction melted (VIM), electroslag remelted (ESR), Vacuum arc remelting (VAR) and pouring into a predetermined mold. Subsequently, a soaking process, a forging process, a solution treatment, an aging process, and the like are performed to produce a turbine rotor. In addition, ultrasonic inspection etc. are performed for the turbine rotor produced by the said method.

上記した蒸気タービンのタービンロータの製造方法によって、タービンロータの少なくとも所定部位が製造される。所定部位として、タービンロータのうち、例えば、700℃以上の高温に曝される部位などが挙げられる。この場合、タービンロータのうち、例えば、600℃程度の温度に曝される部位は、従来の耐熱合金によって製造する。そして、上記した製造方法によって製造された本発明に係る実施形態のNi基合金からなる部品と、従来の耐熱合金からなる部品とを、例えば溶接により接合してタービンロータが構成される。   At least a predetermined portion of the turbine rotor is manufactured by the above-described method for manufacturing a turbine rotor of a steam turbine. Examples of the predetermined portion include a portion of the turbine rotor that is exposed to a high temperature of 700 ° C. or higher. In this case, the part exposed to a temperature of, for example, about 600 ° C. in the turbine rotor is manufactured by a conventional heat-resistant alloy. And the component which consists of Ni base alloy of embodiment which concerns on this invention manufactured by the above-mentioned manufacturing method, and the component which consists of conventional heat-resistant alloys are joined by welding, for example, and a turbine rotor is comprised.

なお、本発明に係る実施形態のNi基合金からなる部品と、従来の耐熱合金からなる部品との接合方法は、溶接に限らず、例えばボルトおよびナットによって締結してもよい。このように、使用される温度条件に基づいて材料を選択し、タービンロータを構成する部品を分割して作製することで、小鋼塊のNi基合金においても、700℃以上の高温環境中で使用可能なタービンロータを製造することができる。なお、使用される温度条件によっては、タービンロータのすべてを上記した蒸気タービンのタービンロータの製造方法によって製造してもよい。   In addition, the joining method of the component which consists of Ni base alloy of embodiment which concerns on this invention, and the component which consists of the conventional heat-resistant alloy is not restricted to welding, For example, you may fasten with a volt | bolt and a nut. In this way, by selecting materials based on the temperature conditions to be used and dividing and manufacturing the components that make up the turbine rotor, even in Ni-based alloys of small steel ingots in a high temperature environment of 700 ° C. or higher A usable turbine rotor can be produced. Depending on the temperature conditions used, all of the turbine rotor may be manufactured by the above-described method for manufacturing a turbine rotor of a steam turbine.

また、本発明に係る実施形態の鍛造部品である蒸気タービンの動翼、蒸気タービンの静翼、蒸気タービン用螺合部材は、例えば次のように作製される。   Moreover, the moving blade of the steam turbine, the stationary blade of the steam turbine, and the screwing member for the steam turbine, which are the forged parts according to the embodiment of the present invention, are manufactured as follows, for example.

まず、本発明に係る実施形態の蒸気タービンの鍛造部品用Ni基合金を構成する組成成分を真空誘導溶解(VIM)し、エレクトロスラグ再溶解(ESR)し、減圧雰囲気で所定の型に流し込み鋳塊を作製し、ソーキング処理を施す。そして、この鋳塊を上記鍛造部品の形状に対応する型に配置して圧延などの鍛造処理、溶体化処理、時効処理などを施すことで蒸気タービンの動翼、蒸気タービンの静翼、蒸気タービン用螺合部材が作製される。すなわち、蒸気タービンの動翼、蒸気タービンの静翼、蒸気タービン用螺合部材は、型鍛造によって作製される。   First, the composition components constituting the Ni-based alloy for forged parts of a steam turbine according to an embodiment of the present invention are vacuum induction melted (VIM), remelted by electroslag (ESR), and poured into a predetermined mold in a reduced-pressure atmosphere. A lump is made and soaked. The ingot is placed in a mold corresponding to the shape of the forged part and subjected to a forging process such as rolling, a solution treatment, an aging process, etc., so that a moving blade of a steam turbine, a stationary blade of a steam turbine, a steam turbine A screwing member is produced. That is, the moving blade of the steam turbine, the stationary blade of the steam turbine, and the screwed member for the steam turbine are produced by die forging.

また、蒸気タービンの動翼、蒸気タービンの静翼、蒸気タービン用螺合部材は、例えば、本発明に係る実施形態の蒸気タービンの鍛造部品用Ni基合金を構成する組成成分を真空誘導溶解(VIM)し、真空アーク再溶解(VAR)し、減圧雰囲気で所定の型に流し込み鋳塊を作製し、ソーキング処理を施し、鍛造処理、溶体化処理、時効処理などを施す方法で作製されてもよい。   In addition, the moving blade of the steam turbine, the stationary blade of the steam turbine, and the screwed member for the steam turbine, for example, vacuum induction melting (for example, the composition component constituting the Ni-based alloy for forged parts of the steam turbine of the embodiment according to the present invention) VIM), vacuum arc remelting (VAR), pouring into a predetermined mold in a reduced pressure atmosphere to produce an ingot, soaking treatment, forging treatment, solution treatment, aging treatment, etc. Good.

さらに、蒸気タービンの動翼、蒸気タービンの静翼、蒸気タービン用螺合部材は、例えば、本発明に係る実施形態の蒸気タービンの鍛造部品用Ni基合金を構成する組成成分を真空誘導溶解(VIM)し、エレクトロスラグ再溶解(ESR)し、真空アーク再溶解(VAR)し、減圧雰囲気で所定の型に流し込み鋳塊を作製し、ソーキング処理を施し、鍛造処理、溶体化処理、時効処理などを施す方法で作製されてもよい。   Furthermore, the moving blade of the steam turbine, the stationary blade of the steam turbine, and the screwed member for the steam turbine are, for example, vacuum induction melting (for example) the composition components constituting the Ni-based alloy for forged parts of the steam turbine according to the embodiment of the present invention ( VIM), electroslag remelting (ESR), vacuum arc remelting (VAR), casting into a predetermined mold in a reduced pressure atmosphere, producing an ingot, soaking treatment, forging treatment, solution treatment, aging treatment It may be produced by a method of applying the above.

また、本発明に係る実施形態の鍛造部品である蒸気タービン用配管は、例えば次のように作製される。   Moreover, the piping for steam turbines which is a forged part of embodiment which concerns on this invention is produced as follows, for example.

まず、本発明に係る実施形態の蒸気タービンの鍛造部品用Ni基合金を構成する組成成分を電気炉溶解(EF)し、アルゴン−酸素脱炭(AOD)を行い、鋳塊を作製し、ソーキング処理を施す。この鋳塊を縦型プレスで穿孔しコップ状の素管を作製し、横型プレスでマンドレルとダイスによる加工と再加熱を繰り返し、蒸気タービン用配管の形状に成型することで蒸気タービン用配管が作製される。この加工方法は、エルハルト−プッシュベンチ製管法である。そして、溶体化処理、時効処理などが施される。   First, the composition components constituting the Ni-based alloy for forged parts of a steam turbine according to an embodiment of the present invention are melted in an electric furnace (EF), subjected to argon-oxygen decarburization (AOD) to produce an ingot, and soaked Apply processing. This ingot is perforated with a vertical press to produce a cup-shaped tube, and processing with a mandrel and a die and reheating are repeated with a horizontal press, and then molded into the shape of a steam turbine piping to produce a steam turbine piping. Is done. This processing method is the Erhard-push bench pipe manufacturing method. And a solution treatment, an aging treatment, etc. are given.

ここで、上記した、蒸気タービンの鍛造部品用Ni基合金および蒸気タービンの鍛造部品を製造する際における、ソーキング処理、溶体化処理および時効処理は、次のように行われる。なお、各処理における温度や時間は、処理される鍛造部品などに応じて、以下に示すそれぞれの範囲内において設定される。   Here, the soaking process, the solution treatment, and the aging process in manufacturing the Ni-based alloy for the forged part of the steam turbine and the forged part of the steam turbine are performed as follows. In addition, the temperature and time in each process are set in the following ranges according to the forged parts to be processed.

ソーキング処理では、熱拡散によって化学成分の偏析を減少させるために、金属または合金を高温で十分な時間加熱する必要がある。そのため、1000〜1250℃の温度範囲で3〜72時間維持することが好ましい。また、鍛造は、材料の十分な変形能を得られる温度からゼロ延性温度までの範囲で行う必要があるため、950〜1100℃の温度範囲で行われることが好ましい。   In the soaking process, it is necessary to heat a metal or alloy at a high temperature for a sufficient time in order to reduce segregation of chemical components by thermal diffusion. Therefore, it is preferable to maintain in the temperature range of 1000 to 1250 ° C. for 3 to 72 hours. Moreover, since it is necessary to perform forging in the range from the temperature which can obtain sufficient deformability of material to zero ductility temperature, it is preferable to be performed in the temperature range of 950-1100 degreeC.

溶体化処理では、1000〜1200℃の温度範囲で3〜24時間維持することが好ましい。ここで、溶体化処理温度は、γ’相析出物を均質に固溶化するために行われ、温度が1000℃を下回る温度では十分に固溶されず、1200℃を上回る温度では結晶粒の粗大化により強度が低下する。これらの熱処理は、上記した温度範囲内で段階を分けていくつかの設定条件で処理されてもよい。溶体化処理後の冷却は、水冷または強制空冷などで行われる。   In the solution treatment, it is preferably maintained in a temperature range of 1000 to 1200 ° C. for 3 to 24 hours. Here, the solution treatment temperature is carried out in order to form a solid solution of the γ ′ phase precipitate. When the temperature is below 1000 ° C., the solution is not sufficiently dissolved, and at a temperature above 1200 ° C., the crystal grains are coarse. As a result, the strength decreases. These heat treatments may be performed under several set conditions in stages within the above temperature range. Cooling after the solution treatment is performed by water cooling or forced air cooling.

時効処理では、炭化物やγ’相などの析出温度範囲である、700〜1050℃の温度範囲で3〜30時間維持することが好ましい。この時効処理を行うことによって、析出物の形態制御と早期析出を達成することが可能となる。なお、この時効処理は、多段に行うものであってもよい。   In the aging treatment, it is preferable to maintain for 3 to 30 hours in a temperature range of 700 to 1050 ° C., which is a precipitation temperature range of carbide, γ ′ phase and the like. By performing this aging treatment, it is possible to achieve morphology control and early precipitation of precipitates. This aging treatment may be performed in multiple stages.

なお、上記した、蒸気タービンのタービンロータ、蒸気タービンの動翼、蒸気タービンの静翼、蒸気タービン用螺合部材、蒸気タービン用配管を作製する方法は、上記した方法に限定されるものではない。   The above-described method for producing the steam turbine turbine rotor, the steam turbine rotor blade, the steam turbine stationary blade, the steam turbine screw member, and the steam turbine pipe is not limited to the above method. .

以下に、本発明に係る実施形態の蒸気タービンの鍛造部品用Ni基合金が、高温強度特性および鍛造性に優れていることを説明する。   Below, it demonstrates that the Ni base alloy for forge components of the steam turbine of embodiment which concerns on this invention is excellent in a high temperature strength characteristic and forgeability.

(高温強度特性および鍛造性の評価)
表1は、高温強度特性および鍛造性の評価に用いられた試料1〜試料25の化学組成を示し、表2は、高温強度特性および鍛造性の評価に用いられた試料26〜試料48の化学組成を示す。なお、表1に示された試料1〜試料25は、本発明に係る実施形態の化学組成範囲にあるNi基合金であり、表2に示された試料26〜試料48は、その組成が本発明に係る実施形態の化学組成範囲にないNi基合金であり、比較例である。なお、ここで使用した本発明に係る実施形態の化学組成範囲にあるNi基合金には、不可避的不純物として、Si、Mn以外に、Fe、Cu、Sが含まれている。
(Evaluation of high temperature strength characteristics and forgeability)
Table 1 shows the chemical compositions of Sample 1 to Sample 25 used for the evaluation of the high temperature strength characteristics and forgeability, and Table 2 shows the chemistry of Sample 26 to Sample 48 used for the evaluation of the high temperature strength characteristics and forgeability. The composition is shown. Note that Sample 1 to Sample 25 shown in Table 1 are Ni-based alloys in the chemical composition range of the embodiment according to the present invention, and Sample 26 to Sample 48 shown in Table 2 have the same composition. It is a Ni-based alloy that is not within the chemical composition range of the embodiment according to the invention, and is a comparative example. The Ni-based alloy in the chemical composition range of the embodiment according to the present invention used here contains Fe, Cu, and S in addition to Si and Mn as unavoidable impurities.

Figure 2012036485
Figure 2012036485

Figure 2012036485
Figure 2012036485

高温強度特性をクリープ破断試験によって評価した。クリープ破断試験では、表1および表2に示す化学組成を有する試料1〜試料48のNi基合金20kgをそれぞれ真空誘導溶解炉にて溶解し、鋳塊を作製した。   High temperature strength properties were evaluated by creep rupture test. In the creep rupture test, 20 kg of the Ni-based alloys of Samples 1 to 48 having the chemical compositions shown in Table 1 and Table 2 were respectively melted in a vacuum induction melting furnace to produce an ingot.

続いて、この鋳塊に対して、1050℃で5時間ソーキング処理を行った。その後、950〜1100℃(再加熱温度が1100℃)の温度範囲で500kgfハンマー鍛造機にて鍛造した。鍛造後、1180℃で4時間加熱し、その後、強制空冷により冷却して溶体化処理を施した。溶体化処理後、750℃で30時間加熱して時効処理を施し、鍛造鋼とした。そして、この鍛造鋼から所定のサイズの試験片を作製した。   Subsequently, the ingot was subjected to a soaking process at 1050 ° C. for 5 hours. Then, it forged with a 500 kgf hammer forging machine in the temperature range of 950-1100 degreeC (reheating temperature is 1100 degreeC). After forging, it was heated at 1180 ° C. for 4 hours, and then cooled by forced air cooling to give a solution treatment. After solution treatment, aging treatment was performed by heating at 750 ° C. for 30 hours to obtain forged steel. And the test piece of the predetermined size was produced from this forged steel.

そして、各試料による試験片に対して、温度が700℃、10万時間におけるクリープ破断強度を測定した。なお、クリープ破断試験は、JIS Z 2271の規格に準じて行われた。   Then, the creep rupture strength at a temperature of 700 ° C. and 100,000 hours was measured for the test piece of each sample. The creep rupture test was performed according to the standard of JIS Z 2271.

ここで、クリープ破断試験における温度条件である700℃は、蒸気タービンの通常の運転時の温度条件およびそれに安全率を見込んだ温度を考慮して設定した。クリープ破断試験の測定結果を表2に示す。   Here, 700 ° C., which is a temperature condition in the creep rupture test, was set in consideration of a temperature condition during normal operation of the steam turbine and a temperature in consideration of the safety factor. Table 2 shows the measurement results of the creep rupture test.

また、各試料に対して、鍛造性の評価を行った。鍛造性の評価は、上記したソーキング処理後の試料を、500kgfハンマー鍛造機にて鍛造し、直径が63mm、長さが500〜570mmの円柱状の試験片を作製した。また、鍛造処理は、鍛造比(JIS G 0701(鋼材鍛錬作業の鍛錬成形比の表わし方)に基づく鍛造比)が3となるまで行った。なお、鍛造処理は、950〜1100℃の範囲で行い、鍛造被対象物である試験片の温度が低下したとき、すなわち鍛造被対象物が硬化してきたときには、再加熱温度1100℃まで再度加熱して鍛造処理を繰り返し行った。鍛造性の評価は、円柱状の試料を冷却後に、鍛造割れの有無を目視観察することで行った。   Moreover, forgeability was evaluated with respect to each sample. Evaluation of forgeability forged the sample after the above-mentioned soaking treatment with a 500 kgf hammer forging machine to produce a cylindrical test piece having a diameter of 63 mm and a length of 500 to 570 mm. Further, the forging process was performed until the forging ratio (forging ratio based on JIS G 0701 (how to express the forging forming ratio of steel forging work)) was 3. Note that the forging process is performed in the range of 950 to 1100 ° C., and when the temperature of the test piece that is the forging object decreases, that is, when the forging object has hardened, it is heated again to the reheating temperature of 1100 ° C. The forging process was repeated. Evaluation of forgeability was performed by visually observing the presence or absence of forging cracks after cooling a cylindrical sample.

ここで、鍛造比とは、鍛造処理を施す前における、鍛造被対象物が伸長される方向に垂直な鍛造被対象物の断面積を、鍛造処理後における、鍛造被対象物が伸長された方向に垂直な鍛造被対象物の断面積で除したものである。   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.

鍛造性の評価結果を表3に示す。表3に示されたリヒート回数は、鍛造処理において鍛造比を3とするまでの間に、鍛造被対象物が再加熱された回数である。ここで、表3において、鍛造割れがない場合には「無」と示し、さらに、鍛造性が優れていることを示すため、鍛造性の評価を「○」で示す。一方、鍛造割れがある場合には「有」と示し、さらに、鍛造性が劣ることを示すため、鍛造性の評価を「×」で示す。   The evaluation results of forgeability are shown in Table 3. The number of reheats shown in Table 3 is the number of times that the forging object is reheated until the forging ratio is set to 3 in the forging process. Here, in Table 3, when there is no forging crack, it is indicated as “none”, and further, the forging property is indicated by “◯” in order to indicate that the forgeability is excellent. On the other hand, when there is a forging crack, it is indicated as “present”, and further, the forgeability is indicated by “x” in order to indicate that the forgeability is inferior.

Figure 2012036485
Figure 2012036485

表3に示すように、試料1〜試料25は、試料26〜試料48に比べて、高いクリープ破断強度が得られることがわかった。さらに、試料1〜試料25は、鍛造性も優れていることがわかった。試料1〜試料25において、クリープ破断強度が高い値となったのは、析出強化と固溶強化が図られたためと考えられる。   As shown in Table 3, it was found that Sample 1 to Sample 25 had higher creep rupture strength than Sample 26 to Sample 48. Furthermore, it was found that Sample 1 to Sample 25 were excellent in forgeability. It is considered that the reason why the creep rupture strength was high in Samples 1 to 25 was that precipitation strengthening and solid solution strengthening were achieved.

一方、比較例の試料において、例えば、試料32、試料42および試料44の比較例に係る試料では、高いクリープ破断強度を示したが、鍛造性が劣っていることがわかった。また、試料46の比較例に係る試料では、高いクリープ破断強度を示したが、鍛造可能な温度範囲が狭いため、リヒート回数が多くなった。このような材料は、鍛造プロセス中に再加熱を必要とする可能性が高いことのみならず、鍛造中に致命的な割れが発生する可能性が高い。このように、比較例に係る試料では、高温強度特性および鍛造性の双方に優れた結果は得られなかった。   On the other hand, in the sample of the comparative example, for example, the samples according to the comparative example of the sample 32, the sample 42, and the sample 44 showed high creep rupture strength, but it was found that the forgeability was inferior. Moreover, although the sample which concerns on the comparative example of the sample 46 showed high creep rupture strength, since the temperature range which can be forged was narrow, the frequency | count of reheating increased. Such materials are not only likely to require reheating during the forging process, but are also more likely to experience fatal cracking during forging. Thus, in the sample according to the comparative example, results excellent in both high temperature strength characteristics and forgeability were not obtained.

本発明のいくつかの実施形態を説明したが、これらの実施形態は、例として提示したものであり、発明の範囲を限定することは意図していない。これら新規な実施形態は、その他の様々な形態で実施されることが可能であり、発明の要旨を逸脱しない範囲で、種々の省略、置き換え、変更を行うことができる。これら実施形態やその変形は、発明の範囲や要旨に含まれるとともに、特許請求の範囲に記載された発明とその均等の範囲に含まれる。   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.

L…ライン。   L ... Line.

Claims (3)

質量%で、C:0.01〜0.15、Cr:14〜20、Co:10〜15、Mo:8〜12、Al:0.5〜4、Ti:0.5〜4、B:0.001〜0.006、Ta:0.1〜0.7、Nb:0.1〜0.4、残部がNiおよび不可避的不純物からなり、かつ9.5質量%≦0.45Cr+Al+Ti≦13質量%の関係を満たすことを特徴とする蒸気タービンの鍛造部品用Ni基合金。   In mass%, C: 0.01 to 0.15, Cr: 14 to 20, Co: 10 to 15, Mo: 8 to 12, Al: 0.5 to 4, Ti: 0.5 to 4, B: 0.001 to 0.006, Ta: 0.1 to 0.7, Nb: 0.1 to 0.4, the balance is made of Ni and inevitable impurities, and 9.5% by mass ≦ 0.45Cr + Al + Ti ≦ 13 A Ni-based alloy for steam turbine forged parts, characterized by satisfying a mass% relationship. 前記不可避的不純物のうち、少なくとも、Siを0.1質量%以下、Mnを0.1質量%以下に抑制したことを特徴とする請求項1記載の蒸気タービンの鍛造部品用Ni基合金。   The Ni-based alloy for steam turbine forged parts according to claim 1, wherein among the inevitable impurities, at least Si is suppressed to 0.1 mass% or less and Mn is controlled to 0.1 mass% or less. 請求項1または2記載の蒸気タービンの鍛造部品用Ni基合金を用いて、少なくとも所定部位が鍛造により作製されたことを特徴とする蒸気タービンの鍛造部品。   A forged component of a steam turbine, wherein at least a predetermined portion is made by forging using the Ni-based alloy for forged components of a steam turbine according to claim 1 or 2.
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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2012255424A (en) * 2011-06-10 2012-12-27 Toshiba Corp Ni-BASED ALLOY FOR CASTING USED FOR STEAM TURBINE AND CASTING COMPONENT OF STEAM TURBINE
JP2013216939A (en) * 2012-04-06 2013-10-24 Nippon Steel & Sumitomo Metal Corp Nickel-based heat-resistant alloy
JP2014122385A (en) * 2012-12-21 2014-07-03 Hitachi Ltd Forging member and steam turbine rotor using the same, steam turbine moving blade, boiler piping, boiler tube and steam turbine bolt using the same
JP2015030916A (en) * 2013-08-07 2015-02-16 株式会社東芝 Ni-BASED ALLOY FOR FORGING, METHOD OF PRODUCING THE SAME AND TURBINE COMPONENT
US10590508B2 (en) 2014-10-10 2020-03-17 Mitsubishi Hitachi Power Systems, Ltd. Method for manufacturing shaft body

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2012255424A (en) * 2011-06-10 2012-12-27 Toshiba Corp Ni-BASED ALLOY FOR CASTING USED FOR STEAM TURBINE AND CASTING COMPONENT OF STEAM TURBINE
JP2013216939A (en) * 2012-04-06 2013-10-24 Nippon Steel & Sumitomo Metal Corp Nickel-based heat-resistant alloy
JP2014122385A (en) * 2012-12-21 2014-07-03 Hitachi Ltd Forging member and steam turbine rotor using the same, steam turbine moving blade, boiler piping, boiler tube and steam turbine bolt using the same
JP2015030916A (en) * 2013-08-07 2015-02-16 株式会社東芝 Ni-BASED ALLOY FOR FORGING, METHOD OF PRODUCING THE SAME AND TURBINE COMPONENT
US10590508B2 (en) 2014-10-10 2020-03-17 Mitsubishi Hitachi Power Systems, Ltd. Method for manufacturing shaft body

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