JP2004036469A

JP2004036469A - Steam turbine rotor

Info

Publication number: JP2004036469A
Application number: JP2002194076A
Authority: JP
Inventors: Shinya Konno; 今野　晋也; Hiroyuki Doi; 土井　裕之; Masahiko Arai; 新井　将彦; Isao Takehara; 竹原　　勲; Takeshi Onoda; 小野田　武志
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 2002-07-03
Filing date: 2002-07-03
Publication date: 2004-02-05

Abstract

<P>PROBLEM TO BE SOLVED: To provide a large-scale rotor for a steam turbine having a main steam temperature ranging from 675°C to 700°C. <P>SOLUTION: The rotor is divided into a plurality of parts in the axial direction, which are each formed of a proper material and metallurgically or mechanically connected together into one rotor unit. It has a portion whose metal temperature becomes 675°C containing Al, Ti, Nb, Mo, Cr and Fe and the remainder containing Ni and impurities, wherein the contents of Al, Ti, Nb and Mo have a raltionship of 1.33×(Al wt%+Ti wt%)+8<(Nb wt%+Mo wt%)<1.33×(Al wt%+Ti wt%)+12. It is formed of a Ni base alloy consisting of Fe having a content of 30 wt% or less and Cr having a content of 10-24 wt%. The rotor can be manufactured using the Ni base alloy having high strength at a high temperature. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、蒸気タービンロータ及び蒸気タービンに関する。
【０００２】
【従来の技術】
蒸気タービンは、効率向上の点から主蒸気温度が高くなってきている。また、蒸気タービンのロータは大型化する傾向にある。主蒸気温度が６００℃以下のときには、ロータ材には１２Ｃｒ鋼のようにフェライト鋼を用いることができた。しかし、主蒸気温度が６５０℃を超えるようになってきた今日ではフェライト鋼では強度不足であり、Ｎｉ基合金が用いられる。
【０００３】
Ｎｉ基合金は、大型鋼塊の製造が難しく、高温強度が高いＮｉ基合金ほど大型化が難しい。
【０００４】
特開２０００−２８２８０８号公報には、異種材料よりなる複数個の分割ロータを一体に連結してロータを形成し、６５０℃以上の温度にさらされる分割ロータをＮｉを３５％以上含むＮｉ基合金によって代表されるオーステナイト系鉄鋼材料によって形成することが記載されている。特開平２０００−６４８０５号公報には、ロータを軸受部と高温部と低温部に分割して異種材料により形成し、これらを溶接により接合することが記載されている。ロータを複数個の分割ロータから形成して一体にすることは特開平３−２３７２０５号公報にも記載されている。
【０００５】
【発明が解決しようとする課題】
蒸気タービンの主蒸気温度は、６７５℃以上７００℃にも及ぼうとしており、このような超高温蒸気タービンに適するロータの開発が望まれる。
【０００６】
本発明の目的は、主蒸気温度が６７５℃以上の蒸気タービンに適用するのに適したロータを提供することにある。
【０００７】
【課題を解決するための手段】
本発明は、複数の分割ロータを冶金的又は機械的に連結することによって一体にし、その際にメタル温度が６７５℃以上になる部分を１つの分割ロータとして、その部分を特定のＮｉ基合金によって形成したものである。
【０００８】
本発明では、メタル温度が６７５℃以上になる部分を、Ａｌ，Ｔｉ，Ｎｂ，Ｍｏ，Ｃｒ及びＦｅを含み、残部がＮｉ及び不純物よりなり、ＡｌとＴｉとＮｂ及びＭｏの含有量が１．３３　×（Ａｌ重量％＋Ｔｉ重量％）＋８＜（Ｎｂ重量％＋Ｍｏ重量％）＜１．３３　×（Ａｌ重量％＋Ｔｉ重量％）＋１２の関係にあり、Ｆｅの含有量が３０重量％以下、Ｃｒの含有量が１０〜２４重量％よりなるＮｉ基合金によって形成する。あるいはその部分を、Ｆｅ量３５〜４５重量％，Ｃｒ量１４〜１８重量％，Ｔｉ量１．５〜２．０重量％，Ｎｂ量１．８〜２．２重量％，Ａｌ量１．０〜１．２５重量％，Ｃ量０．０５重量％以下、残部がＮｉ及び不純物よりなり、γ′相により析出強化されたＮｉ基合金により形成される。前記した何れの場合も、分割ロータは鍛造材によって形成される。
【０００９】
本発明のロータは、少なくとも２種の材料によって形成される。好ましいロータは、３種の材料から形成される。更に好ましい分割ロータは４種の材料から形成される。
【００１０】
２種の材料からロータが構成される場合は、メタル温度が６７５℃以上になる部分を特定の材料にて形成し、その他の部分を別の材料にて形成する。
【００１１】
３種類の材料にてロータを形成する場合は、メタル温度が６７５℃以上になる部分を特定の材料で形成し、６７５℃未満の部分を更に２種の材料にて形成する。この場合、メタル温度が６６０℃以上６７５℃未満の部分を１つの材料で形成し、メタル温度が６６０℃未満の部分を別の材料で形成することが望ましい。
【００１２】
４種類の材料にてロータを形成する場合は、メタル温度が６７５℃以上になる部分及びメタル温度が６６０℃以上６７５℃未満の部分をそれぞれ特定の材料で形成し、その他を更に２種類の材料で形成する。この場合、メタル温度６３０℃〜６６０℃の部分とメタル温度６３０℃未満の部分とに分けてそれぞれを特定の材料により形成することが望ましい。
【００１３】
以下、説明を簡略化するために、メタル温度が６７５℃以上になる部分を形成する分割ロータを超高温度域ロータと呼ぶ。同様にメタル温度が６６０℃以上
６７５℃未満の部分を形成する分割ロータを高温度域ロータ，メタル温度が６３０℃以上６６０℃未満の部分を形成する分割ロータを中温度域ロータ，メタル温度が６３０℃未満の部分を形成する分割ロータを低温度域ロータと呼ぶことにする。
【００１４】
高温度域ロータは、Ａｌ，Ｔｉ，Ｎｂ，Ｍｏ，Ｃｒ及びＦｅを含み、残部が
Ｎｉ及び不純物よりなり、ＡｌとＴｉとＮｂ及びＭｏの含有量が１．３３×（Ａｌ重量％＋Ｔｉ重量％）＋２＜（Ｎｂ重量％＋Ｍｏ重量％）＜１．３３　×（Ａｌ重量％＋Ｔｉ重量％）＋４の関係にあり、Ｆｅの含有量が４５〜６０重量％、Ｃｒの含有量が１４〜１６重量％よりなるＮｉ基合金、特にその鍛造材によって形成されることが望ましい。
【００１５】
中温度域ロータは、ＡｌとＴｉとＮｂ及びＭｏの含有量が１．３３　×（Ａｌ重量％＋Ｔｉ重量％）＋２＜（Ｎｂ重量％＋Ｍｏ重量％）＜１．３３　×（Ａｌ重量％＋Ｔｉ重量％）＋４の関係にあり、Ｆｅの含有量が４５〜６０重量％、Ｃｒの含有量が１４〜１６重量％よりなるＮｉ基合金、特に鍛造材によって形成することが望ましい。
【００１６】
低温度域ロータは、中温度域ロータと同じ材料で形成することもできるが、
１２Ｃｒ鋼の鍛造材によって形成するのが特に望ましい。
【００１７】
Ｎｉ基合金として知られているＩＮ７１８は、超高温度域ロータの材料として好適である。ＩＮ７０６は、高温度域ロータの材料として適する。Ａ２８６は中温度域ロータ及び低温度域ロータの材料として適する。低温度域ロータは、１２Ｃｒ鋼とすることもできる。
【００１８】
超高温度域ロータに使用される、Ｆｅ量３５〜４５重量％，Ｃｒ量１４〜１８重量％，Ｔｉ量１．５〜２．０重量％，Ｎｂ量１．８〜２．２　重量％，Ａｌ量１．０〜１．２５重量％，Ｃ量０．０５重量％以下、残部がＮｉ及び不純物よりなり、
γ′相により析出強化されたＮｉ基合金は、本発明者らの開発による材料であり、有害なδ相の析出を抑え、ＩＮ７０６と同程度の強度が得られるようにしたものである。
【００１９】
本発明によれば、前記した複数個の分割ロータによって形成されたロータを具備し、主蒸気温度が６７５℃以上である蒸気タービンが提供される。
【００２０】
【発明の実施の形態】
大型鍛造品の製造性と高温強度は反比例の関係にある。図１は、Ｎｉ基合金を強度と製造性の観点から３つに分類した図を示している。Ｎｉ基合金は、主にＡｌとＴｉによる析出強化とＮｂとＭｏによる固溶強化とによって材質強化がなされる。このことから、ＮｂとＭｏによる固溶強化を縦軸とし、ＡｌとＴｉによる析出強化を横軸として分類した。図１中にＡＧで示されているＡグループは、７００℃の温度域まで使用可能であるが、１０トン以上の鋼塊を製造するのが難しい領域である。このＡグループに含まれるＮｉ基合金は、超高温度域ロータの部分に使用することができる。ＢＧで示されているＢグループは、使用可能な温度域が６７５℃未満であり、１５トン以下の鋼塊までなら製造できる領域である。このＢグループに含まれるＮｉ基合金は、高温度域ロータの部分に使用することができる。ＣＧで示されているＣグループは、使用可能な温度域が６６０℃未満であり、２０トン以上の大型鋼塊を製造できる領域を示している。このＣグループに含まれるＮｉ基合金は中温度域ロータ及び低温度域ロータの部分に使用することができる。
【００２１】
表１は、図１中に示されているＮｉ基合金の化学成分を示したものである。図１のＡグループに含まれる代表的なＮｉ基合金はＩＮ７１８である。Ｂグループに含まれる代表的なＮｉ基合金はＩＮ７０６である。Ｃグループに含まれる代表的なＮｉ基合金はＡ２８６である。
【００２２】
【表１】

【００２３】
図２に、表１に示したＮｉ基合金について、６５０℃におけるクリープラプチュア強度とＦｅ含有量との関係を示した。析出強化及び固溶強化の違いによって強度に違いは出るものの、強度の最大値はＦｅ含有量が多いほど低下する。したがって、メタル温度が高い部位に使用される材料ほど、Ｆｅ含有量を低くする必要がある。
【００２４】
図３は、蒸気タービンロータの模式図をロータ内のメタル温度分布と共に示した。超高温度域部位１はメタル温度が６７５℃以上になる部分であり、図１のＡグループに属するＮｉ基合金を使用する。ただし、Ｆｅ含有量が多いと強度が低下するため、Ｆｅ含有量は３０重量％以下にする。メタル温度が６７５℃以上の部位がロータ全体に占める比率は低く、５トン鋼塊で十分である。
【００２５】
高温度域部位２はメタル温度が６６０℃以上６７５℃未満の部分であり図１のＢグループのＮｉ基合金を使用する。この部位はメタル温度が６７５℃以上の部位に比べるとロータ全体に占める割合は大きくなるが、それでも１０トン以下である。したがって、図１のＢグループに属するＮｉ基合金を使用することができる。強度維持の観点から、この部位に使用されるＮｉ基合金のＦｅ含有量は４５重量％以下にすべきであり、材料コストを高めないために下限量は３０重量％以上にするのがよい。
【００２６】
中温及び低温度域部位３はメタル温度が６６０℃未満の部分であり、図１のＣグループに属するＮｉ基合金が使用される。この部位はジャーナル部を含むため、大型鋼塊を用いる必要があるが、図１のＣグループに属するＮｉ基合金は、
２０トンを超える大型鋼塊を製造可能であるので、この部位の材料に適する。強度維持と材料コスト低減の観点から、Ｆｅ含有量は４５〜５５重量％にするのが望ましい。なお、メタル温度が６３０℃を下回る部分は、１２Ｃｒ鋼を用いることも可能である。
【００２７】
図４（ａ）は、ＩＮ７１８とＩＮ７０６とＡ２８６の３種類のＮｉ基合金によってロータを形成した例を示している。本実施例のロータは７つの部位に分割されている。ロータは中央部を境にして左右対称になっており、左半分あるいは右半分のロータ材耐用温度とメタル温度は図示のようになっている。
【００２８】
図４（ｂ）は、ＩＮ７１８とＩＮ７０６の２種類のＮｉ基合金にてロータを形成した例を示している。図４（ｃ）はＩＮ７０６とＡ２８６にてロータを形成した例を示している。
【００２９】
表２に示した３鋼種について、大型鋼塊を作製し鍛造及び熱処理後、切断して組織観察を行った。また、クリープ試験を行いクリープ破断した試験片の組織観察を行った。
【００３０】
【表２】

【００３１】
図５は、熱処理後の光学顕微鏡組織のスケッチである。従来材の鋼種１はＮｂＣが帯状に多量に析出している。従来材の鋼種２はＮｂを低減しているため、鋼種１に比較するとＮｂＣは少ない。しかし、Ｃ量が多いため、鋼種３にくらべるとＮｂＣの析出量は多い。鋼種３は、本発明による改良材であり、Ｎｂ，Ｃ共に減量しているため、ＮｂＣの析出量が少ない。鋼種１，２及び３の結晶粒度は、それぞれ４．０，３．５，３．０　であった。図６は鋼種１，鋼種３のクリープ試験結果である。図７はクリープ破断材のＴＥＭ（透過型電子顕微鏡像）である。鋼種３では、偏析元素であるＮｂが２％まで低減されているにもかかわらず、高温クリープ強度が鋼種１と同等であり、クリープ破断に至るまで強化相であるγ′相が残留し、有害な相が見られない。鋼種３は、本発明において超高温度域の部位を形成するのに極めて好適である。
【００３２】
【発明の効果】
本発明により、主蒸気温度が６７５℃以上、７００℃に及ぶ蒸気タービン向けの大型のロータを実現できた。
【図面の簡単な説明】
【図１】Ｎｉ基鍛造合金を、Ｎｂ，Ｍｏによる固溶強化とＡｌ，Ｔｉによる析出強化の観点から分類した図。
【図２】Ｎｉ基鍛造合金のＦｅ含有量とクリープ強度の関係を示す図。
【図３】本発明による蒸気タービンロータの模式図。
【図４（ａ）】本発明の実施例を示すロータの模式図。
【図４（ｂ）】本発明の実施例を示すロータの模式図。
【図４（ｃ）】本発明の実施例を示すロータの模式図。
【図５】Ｎｉ基合金の溶解熱処理後の光学顕微鏡組織をスケッチした図。
【図６】Ｎｉ基合金のクリープ破断試験結果を示す図。
【図７】Ｎｉ基合金のクリープ破断試験後のＴＥＭ組織をスケッチした図。
【符号の説明】
１…超高温度域部位、２…高温度域部位、３…中温及び低温度域部位。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a steam turbine rotor and a steam turbine.
[0002]
[Prior art]
In steam turbines, the main steam temperature is increasing from the viewpoint of improving efficiency. Further, the rotor of a steam turbine tends to be large. When the main steam temperature was 600 ° C. or lower, ferrite steel such as 12Cr steel could be used for the rotor material. However, today when the main steam temperature has exceeded 650 ° C., the strength of ferrite steel is insufficient, and a Ni-based alloy is used.
[0003]
It is difficult to produce large ingots of Ni-based alloys, and it is difficult to increase the size of Ni-based alloys having higher high-temperature strength.
[0004]
Japanese Patent Application Laid-Open No. 2000-282808 discloses a Ni-based alloy in which a plurality of divided rotors made of different materials are integrally connected to form a rotor, and the divided rotor exposed to a temperature of 650 ° C. or more contains 35% or more of Ni. Is formed of an austenitic steel material represented by Japanese Patent Application Laid-Open No. 2000-64805 describes that a rotor is divided into a bearing portion, a high-temperature portion, and a low-temperature portion, formed of different materials, and these are joined by welding. The formation of the rotor from a plurality of split rotors to be integrated is also described in JP-A-3-237205.
[0005]
[Problems to be solved by the invention]
The main steam temperature of a steam turbine is approaching 675 ° C. or more and 700 ° C., and development of a rotor suitable for such an ultra-high-temperature steam turbine is desired.
[0006]
An object of the present invention is to provide a rotor suitable for application to a steam turbine having a main steam temperature of 675 ° C. or higher.
[0007]
[Means for Solving the Problems]
The present invention integrates a plurality of divided rotors by metallurgically or mechanically connecting them, and in that case, a part where the metal temperature becomes 675 ° C. or more is defined as one divided rotor, and the part is formed of a specific Ni-based alloy. It was formed.
[0008]
In the present invention, the portion where the metal temperature becomes 675 ° C. or higher contains Al, Ti, Nb, Mo, Cr and Fe, and the remainder consists of Ni and impurities, and the content of Al, Ti, Nb and Mo is 1. 33 × (Al wt% + Ti wt%) + 8 <(Nb wt% + Mo wt%) <1.33 × (Al wt% + Ti wt%) + 12, Fe content is 30 wt% or less, Cr Is formed from a Ni-based alloy having a content of 10 to 24% by weight. Alternatively, the portion may be composed of 35 to 45% by weight of Fe, 14 to 18% by weight of Cr, 1.5 to 2.0% by weight of Ti, 1.8 to 2.2% by weight of Nb, and 1.0% of Al. 1.25% by weight, C content of 0.05% by weight or less, with the balance being Ni and impurities, formed of a Ni-based alloy precipitation-strengthened by a γ 'phase. In each case described above, the split rotor is formed of a forged material.
[0009]
The rotor of the present invention is formed of at least two kinds of materials. Preferred rotors are formed from three materials. More preferred split rotors are formed from four materials.
[0010]
When the rotor is composed of two types of materials, a portion where the metal temperature is 675 ° C. or higher is formed of a specific material, and the other portions are formed of another material.
[0011]
When the rotor is formed of three types of materials, a portion where the metal temperature is 675 ° C. or higher is formed of a specific material, and a portion where the metal temperature is lower than 675 ° C. is further formed of two types of materials. In this case, it is desirable that a portion having a metal temperature of 660 ° C. or more and less than 675 ° C. is formed of one material, and a portion having a metal temperature of less than 660 ° C. is formed of another material.
[0012]
When the rotor is formed of four types of materials, a portion where the metal temperature is 675 ° C. or more and a portion where the metal temperature is 660 ° C. or more and less than 675 ° C. are each formed of a specific material, and the other portions are further two types of materials. Formed. In this case, it is desirable to divide a portion having a metal temperature of 630 ° C. to 660 ° C. and a portion having a metal temperature of less than 630 ° C. and form each of them with a specific material.
[0013]
Hereinafter, for the sake of simplicity, the split rotor that forms a portion where the metal temperature becomes 675 ° C. or higher is referred to as an ultra-high temperature range rotor. Similarly, a divided rotor forming a portion having a metal temperature of 660 ° C. or more and less than 675 ° C. is a high temperature region rotor, and a divided rotor forming a portion having a metal temperature of 630 ° C. or more and less than 660 ° C. is a medium temperature region rotor. The divided rotor that forms a portion having a temperature lower than C is referred to as a low-temperature region rotor.
[0014]
The high-temperature region rotor contains Al, Ti, Nb, Mo, Cr and Fe, and the balance consists of Ni and impurities, and the content of Al, Ti, Nb and Mo is 1.33 × (Al wt% + Ti wt%). ) +2 <(Nb wt% + Mo wt%) <1.33 × (Al wt% + Ti wt%) + 4, where the Fe content is 45 to 60 wt% and the Cr content is 14 to 16 wt. % Of the Ni-based alloy, particularly a forged material thereof.
[0015]
The medium temperature rotor has a content of Al, Ti, Nb and Mo of 1.33 × (Al weight% + Ti weight%) + 2 <(Nb weight% + Mo weight%) <1.33 × (Al weight% + Ti weight) %) + 4, and is preferably formed of a Ni-based alloy having a Fe content of 45 to 60% by weight and a Cr content of 14 to 16% by weight, particularly a forged material.
[0016]
The low temperature range rotor can be made of the same material as the medium temperature range rotor,
It is particularly desirable to form it with a 12Cr steel forging.
[0017]
IN718, which is known as a Ni-based alloy, is suitable as a material for an ultra-high temperature range rotor. IN706 is suitable as a material for a high temperature range rotor. A286 is suitable as a material for the medium temperature range rotor and the low temperature range rotor. The low temperature rotor may be 12Cr steel.
[0018]
35 to 45% by weight of Fe, 14 to 18% by weight of Cr, 1.5 to 2.0% by weight of Ti, 1.8 to 2.2% by weight of Nb used in an ultra-high temperature range rotor, An Al content of 1.0 to 1.25% by weight, a C content of 0.05% by weight or less, and the balance of Ni and impurities
The Ni-based alloy precipitation-strengthened by the γ 'phase is a material developed by the present inventors, and suppresses precipitation of a harmful δ phase so that the same strength as IN706 can be obtained.
[0019]
According to the present invention, there is provided a steam turbine including a rotor formed by the plurality of split rotors and having a main steam temperature of 675 ° C. or higher.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Manufacturability and high-temperature strength of large forgings are in inverse proportion. FIG. 1 shows a diagram in which a Ni-based alloy is classified into three from the viewpoint of strength and manufacturability. The quality of the Ni-based alloy is strengthened mainly by precipitation strengthening by Al and Ti and solid solution strengthening by Nb and Mo. From this, the solid solution strengthening by Nb and Mo was classified as the vertical axis, and the precipitation strengthening by Al and Ti was classified as the horizontal axis. Group A indicated by AG in FIG. 1 can be used up to a temperature range of 700 ° C., but is an area where it is difficult to produce a steel ingot of 10 tons or more. The Ni-based alloy included in the group A can be used for a part of a rotor in an ultra-high temperature range. Group B indicated by BG is an area where the usable temperature range is less than 675 ° C. and can be manufactured up to a steel ingot of 15 tons or less. The Ni-based alloy included in the group B can be used for a high temperature range rotor. Group C indicated by CG indicates an area where the usable temperature range is lower than 660 ° C. and a large ingot of 20 tons or more can be produced. The Ni-based alloy included in the C group can be used for the middle temperature range rotor and the low temperature range rotor.
[0021]
Table 1 shows the chemical components of the Ni-based alloy shown in FIG. A typical Ni-based alloy included in the group A in FIG. 1 is IN718. A typical Ni-based alloy included in the B group is IN706. A representative Ni-based alloy included in the C group is A286.
[0022]
[Table 1]

[0023]
FIG. 2 shows the relationship between the creep rupture strength at 650 ° C. and the Fe content of the Ni-based alloys shown in Table 1. Although the strength differs depending on the difference between precipitation strengthening and solid solution strengthening, the maximum strength decreases as the Fe content increases. Therefore, it is necessary to lower the Fe content as the material is used in a portion where the metal temperature is higher.
[0024]
FIG. 3 shows a schematic view of a steam turbine rotor together with a metal temperature distribution in the rotor. The ultrahigh temperature region 1 is a portion where the metal temperature becomes 675 ° C. or higher, and uses a Ni-based alloy belonging to the group A in FIG. However, if the Fe content is large, the strength is reduced. Therefore, the Fe content is set to 30% by weight or less. The ratio of the portion where the metal temperature is 675 ° C. or more to the entire rotor is low, and a 5-ton steel ingot is sufficient.
[0025]
The high temperature region 2 is a portion having a metal temperature of 660 ° C. or more and less than 675 ° C., and uses the Ni-based alloy of the group B in FIG. Although this portion accounts for a larger proportion of the entire rotor than a portion where the metal temperature is 675 ° C. or higher, it still occupies 10 tons or less. Therefore, a Ni-based alloy belonging to the group B in FIG. 1 can be used. From the viewpoint of maintaining the strength, the Fe content of the Ni-based alloy used in this portion should be 45% by weight or less, and the lower limit is preferably 30% by weight or more so as not to increase the material cost.
[0026]
The middle and low temperature region 3 is a portion where the metal temperature is lower than 660 ° C., and a Ni-based alloy belonging to the group C in FIG. 1 is used. Since this part includes a journal part, it is necessary to use a large steel ingot, but the Ni-based alloy belonging to the C group in FIG.
Since a large steel ingot exceeding 20 tons can be manufactured, it is suitable for the material in this part. From the viewpoint of maintaining strength and reducing material costs, the Fe content is desirably 45 to 55% by weight. In addition, 12Cr steel can also be used for the part where the metal temperature is lower than 630 ° C.
[0027]
FIG. 4A shows an example in which the rotor is formed of three types of Ni-based alloys, IN718, IN706, and A286. The rotor of this embodiment is divided into seven parts. The rotor is symmetrical with respect to the center part, and the left half or right half rotor material service temperature and metal temperature are as shown in the figure.
[0028]
FIG. 4B shows an example in which the rotor is formed of two types of Ni-based alloys, IN718 and IN706. FIG. 4C shows an example in which the rotor is formed by IN706 and A286.
[0029]
For the three steel types shown in Table 2, large ingots were prepared, forged and heat-treated, and then cut to observe the structure. In addition, a creep test was performed, and the structure of the test piece that had undergone creep rupture was observed.
[0030]
[Table 2]

[0031]
FIG. 5 is a sketch of the optical microscope structure after the heat treatment. Conventional steel type 1 has a large amount of NbC precipitated in a band shape. Since the steel type 2 of the conventional material has reduced Nb, the NbC is smaller than that of the steel type 1. However, since the amount of C is large, the precipitation amount of NbC is larger than that of steel type 3. Steel type 3 is an improved material according to the present invention, and since both Nb and C are reduced, the precipitation amount of NbC is small. The grain sizes of

steel types

1, 2, and 3 were 4.0, 3.5, and 3.0, respectively. FIG. 6 shows the results of a creep test of steel type 1 and steel type 3. FIG. 7 is a TEM (transmission electron microscope image) of the creep rupture material. In steel type 3, although the segregation element Nb is reduced to 2%, the high-temperature creep strength is equivalent to that of steel type 1, and the γ 'phase as the strengthening phase remains until creep rupture occurs, and is harmful. I can't see any phases. Steel type 3 is extremely suitable for forming a part in an ultra-high temperature range in the present invention.
[0032]
【The invention's effect】
According to the present invention, a large-sized rotor for a steam turbine having a main steam temperature of 675 ° C. or more and 700 ° C. can be realized.
[Brief description of the drawings]
FIG. 1 is a diagram in which Ni-based forged alloys are classified in terms of solid solution strengthening by Nb and Mo and precipitation strengthening by Al and Ti.
FIG. 2 is a view showing the relationship between the Fe content of a Ni-based forged alloy and creep strength.
FIG. 3 is a schematic view of a steam turbine rotor according to the present invention.
FIG. 4A is a schematic view of a rotor showing an embodiment of the present invention.
FIG. 4B is a schematic view of a rotor showing an embodiment of the present invention.
FIG. 4C is a schematic view of a rotor showing an embodiment of the present invention.
FIG. 5 is a diagram showing a sketch of an optical microscopic structure of a Ni-based alloy after a melting heat treatment.
FIG. 6 is a view showing a creep rupture test result of a Ni-based alloy.
FIG. 7 is a diagram illustrating a sketch of a TEM structure after a creep rupture test of a Ni-based alloy.
[Explanation of symbols]
1. Ultra-high temperature region, 2 ... High temperature region, 3 ... Medium temperature and low temperature region.

Claims

In a rotor used in a steam turbine having a main steam temperature of 675 ° C. or higher, the rotor is divided into a plurality of portions according to a metal temperature and connected,
The portion where the metal temperature becomes 675 ° C. or higher contains Al, Ti, Nb, Mo, Cr and Fe, and the remainder consists of Ni and impurities, and the content of Al, Ti, Nb and Mo is 1.33 × (Al weight % + Ti wt%) + 8 <(Nb wt% + Mo wt%) <1.33 × (Al wt% + Ti wt%) + 12, where the Fe content is 30 wt% or less and the Cr content is 10 A steam turbine rotor made of a Ni-based alloy comprising up to 24% by weight.

In claim 1, the portion where the metal temperature is 675 ° C. or higher is 50 to 55% by weight of Ni, 17 to 21% by weight of Cr, 0.65 to 1.15% by weight of Ti, and 4.75 to 5% of Nb + Ta. .50% by weight, Al amount 0.2-0.8% by weight, Mo 2.8-3.3% by weight, C amount 0.05% by weight or less The balance is made of a Ni-based alloy made of Fe. Characteristic steam turbine rotor.

2. The steam turbine rotor according to claim 1, wherein a portion where the metal temperature becomes 675 ° C. or higher is formed by a forged material of the Ni-based alloy. 3.

A rotor formed by connecting split rotors made of different materials in the axial direction and used for a steam turbine having a main steam temperature of 675 ° C. or more,
Each divided rotor is formed by a portion where the metal temperature is 675 ° C. or more, a portion where the metal temperature is 660 to 675 ° C., and a portion where the metal temperature is less than 660 ° C.
The split rotor that forms the portion where the metal temperature is 675 ° C. or higher contains Al, Ti, Nb, Mo, Cr, and Fe, and the remainder consists of Ni and impurities, and the content of Al, Ti, Nb, and Mo is 1. 33 × (Al wt% + Ti wt%) + 8 <(Nb wt% + Mo wt%) <1.33 × (Al wt% + Ti wt%) + 12, Fe content is 30 wt% or less, Cr Formed by a Ni-based alloy having a content of 10 to 24% by weight,
The split rotor forming the portion where the metal temperature is 660 to 675 ° C. contains Al, Ti, Nb, Mo, Cr and Fe, the remainder is made of Ni and impurities, and the content of Al, Ti, Nb and Mo is 1%. 0.33 × (Al wt% + Ti wt%) + 4 <(Nb wt% + Mo wt%) <1.33 × (Al wt% + Ti wt%) + 8, and the Fe content is 30 to 45 wt% A steam turbine rotor made of a Ni-based alloy having a Cr content of 14 to 18% by weight.

5. The rotor according to claim 4, wherein the split rotor forming the portion where the metal temperature is 660 to 675 [deg.] C. comprises 35 to 45% by weight of Fe, 14 to 18% by weight of Cr, 1.5 to 2.0% by weight of Ti, and Nb. 2.5 to 3.0% by weight, 0.1 to 0.5% by weight of Al, 0.05% by weight or less of C. The balance is made of a Ni-based alloy forging made of Ni and impurities. A steam turbine rotor.

5. The split rotor according to claim 4, wherein the divided rotor forming the portion having a metal temperature of less than 660 ° C. contains Al, Ti, Nb, Mo, Cr and Fe, and the remainder consists of Ni and impurities, and contains Al, Ti, Nb and Mo. The amount is 1.33 × (Al wt% + Ti wt%) + 2 <(Nb wt% + Mo wt%) <1.33 × (Al wt% + Ti wt%) + 4, and the Fe content is 45 to 45%. A steam turbine rotor made of a Ni-based alloy having 60% by weight and a Cr content of 14 to 16% by weight.

7. The steam turbine rotor according to claim 6, wherein the split rotor forming the portion having a metal temperature of less than 660 ° C. is formed of a Ni-based alloy forging made of A286.

5. The steam turbine rotor according to claim 4, wherein the plurality of divided parts are connected to adjacent parts by one of metallurgical coupling and mechanical coupling.

5. The divided rotor according to claim 4, wherein the portion having a metal temperature of less than 660 ° C. is further divided into a portion having a metal temperature of 630 ° C. or more and a portion having a metal temperature of less than 630 ° C. , Ti, Nb, Mo, Cr and Fe, with the balance being Ni and impurities, the content of Al, Ti, Nb and Mo being 1.33 × (Al wt% + Ti wt%) + 2 <(Nb wt% + Mo wt%) <1.33 × (Al wt% + Ti wt%) + 4, and a Ni-based alloy having a Fe content of 45 to 60 wt% and a Cr content of 14 to 16 wt% A steam turbine rotor formed of a forged material.

10. The split rotor according to claim 9, wherein the divided rotor forming the portion having a metal temperature of 630 ° C. or higher has a Ni content of 23 to 29% by weight, a Cr content of 14 to 16% by weight, a Mo content of 1.0 to 1.5% by weight, 0.1-0.3% by weight, 0.7-1.3% by weight of Ti, 1.0-1.5% by weight of Mn, 0.25-0.75% by weight of Si , C in an amount of 0.03 to 0.07% by weight, and a balance made of a forged Ni-Fe-based alloy comprising Fe and impurities.

The steam turbine rotor according to claim 9, wherein the divided rotor forming the portion where the metal temperature is lower than 630 ° C is formed of a forged material made of 12Cr steel.

10. The divided rotor forming a portion having a metal temperature of 630 ° C. or higher and the split rotor forming a portion having a metal temperature lower than 630 ° C. are connected by one of metallurgical coupling and mechanical coupling. A steam turbine rotor.

In a rotor used in a steam turbine having a main steam temperature of 675 ° C. or higher and formed by axially connecting split rotors made of different kinds of materials,
One of the split rotors is formed at a portion where the metal temperature becomes 675 ° C. or higher, and the split rotor has an Fe content of 35 to 45 wt%, a Cr content of 14 to 18 wt%, a Ti content of 1.5 to 2.0 wt%, Nb content 1.8-2.2% by weight, Al content 1.0-1.25% by weight, C content 0.05% by weight or less, balance Ni and impurities, precipitation strengthened by γ 'phase Ni A steam turbine rotor formed of a forged material of a base alloy.

14. The method according to claim 13, wherein the portion having a metal temperature of 660 ° C. to 675 ° C. further forms one split rotor, the split rotor including Al, Ti, Nb, Mo, Cr and Fe, and the balance being Ni and impurities. , Al, Ti, Nb and Mo content: 1.33 × (Al wt% + Ti wt%) + 4 <(Nb wt% + Mo wt%) <1.33 × (Al wt% + Ti wt%) + 8 A steam turbine rotor formed of a Ni-based alloy having a Fe content of 30 to 45% by weight and a Cr content of 14 to 18% by weight.

15. The method according to claim 14, wherein the portion having a metal temperature of less than 660 ° C. further forms one split rotor, wherein the split rotor contains Al, Ti, Nb, Mo, Cr and Fe, and the balance consists of Ni and impurities. And the contents of Ti, Nb and Mo are 1.33 × (Al wt% + Ti wt%) + 2 <(Nb wt% + Mo wt%) <1.33 ×
(Al wt% + Ti wt%) + 4, wherein the steam is formed by a Ni-based alloy having an Fe content of 45 to 60 wt% and a Cr content of 14 to 16 wt%. Turbine rotor.

The split rotor according to claim 14, wherein one of the portions having a metal temperature of 630 ° C or higher among the portions having a metal temperature of lower than 660 ° C, the split rotor includes Al, Ti, Nb, Mo, Cr, and Fe; The balance consists of Ni and impurities,
The relationship of Al, Ti, Nb and Mo content is 1.33 × (Al wt% + Ti wt%) + 2 <(Nb wt% + Mo wt%) <1.33 × (Al wt% + Ti wt%) + 4 A steam turbine rotor comprising a Ni-based alloy having an Fe content of 45 to 60% by weight and a Cr content of 14 to 16% by weight.

17. The steam turbine rotor according to claim 16, wherein the split rotor forming the portion having a metal temperature of 630 ° C. or more is formed of a forged Ni-based alloy made of A286.

17. The steam turbine rotor according to claim 16, wherein the split rotor forming the portion having a metal temperature of less than 630 ° C is formed of a forged material made of 12Cr steel.

In a steam turbine having a rotor having a main steam temperature of 675 ° C. or more and a weight of 10 tons or more,
The rotor is divided into a plurality according to metal temperature, and is integrally formed by being connected in the axial direction,
A split rotor for forming a portion having a metal temperature of 675 ° C. or higher, the split rotor containing Al, Ti, Nb, Mo, Cr and Fe, the balance being Ni and impurities, and Al, Ti, Nb and Mo content is 1.33 × (Al wt% + Ti wt%) + 8 <(Nb wt% + Mo wt%) <1.33 × (Al wt% + Ti wt%) + 12, and Fe content Is formed of a Ni-based alloy containing 30% by weight or less and a Cr content of 10 to 24% by weight.

20. The method according to claim 19, further comprising a split rotor forming a portion having a metal temperature of 660 ° C. or more and less than 675 ° C., wherein the split rotor contains Al, Ti, Nb, Mo, Cr, and Fe, and the balance is made of Ni and impurities; The content of Al, Ti, Nb and Mo is 1.33 × (Al wt% + Ti wt%) + 4 <(Nb wt% + Mo wt%) <1.33 × (Al wt% + Ti wt%) + 8 A steam turbine comprising a Ni-based alloy having an Fe content of 30 to 45% by weight and a Cr content of 14 to 18% by weight.