JP2010084167A - Nickel-based alloy and high-temperature member for turbine using the same - Google Patents
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本発明は、フェライト鋼との接合に適したＮｉ基合金、及び、Ｎｉ基合金を用いた蒸気タービン用高温部材に関する。 The present invention relates to a Ni-based alloy suitable for joining with ferritic steel, and a high-temperature member for a steam turbine using the Ni-based alloy.
産業用ガスタービンや航空機用ジェットエンジン等の高温部材には、Ｎｉ基耐熱合金が利用されている。Ｎｉ基耐熱合金は、Ｗ，Ｍｏ，Ｃｏなどの固溶強化元素、またＡｌ，Ｔｉ，Ｎｂ，Ｔａなどの析出強化元素を多く含有するため、優れた高温強度を有している。主要な強化相であるγ′Ｎｉ3(Ａｌ，Ｔｉ)相は、温度上昇に伴って強度も上昇する性質があるため、高温における強度特性の向上に極めて効果的であり、γ′相をいかに多く析出させるかに主眼を置いて合金開発がなされている。 Ni-based heat-resistant alloys are used for high-temperature members such as industrial gas turbines and aircraft jet engines. The Ni-base heat-resistant alloy has excellent high-temperature strength because it contains many solid-solution strengthening elements such as W, Mo, and Co and precipitation strengthening elements such as Al, Ti, Nb, and Ta. The γ'Ni 3 (Al, Ti) phase, which is the main strengthening phase, has the property that the strength increases with increasing temperature, so it is extremely effective in improving the strength properties at high temperatures. Alloys are being developed with a focus on whether to deposit a lot.
一方、石炭火力発電に利用される蒸気タービン部材には、従来、高Ｃｒフェライト系耐熱鋼が利用されてきた。フェライト系耐熱鋼は、一般的にＮｉ基合金よりも製造性に優れており、タービンロータのような２０トンを超える大型鍛造材の製造も可能である。Ｎｉ基合金では、現在の製造技術によってフェライト系耐熱鋼と同等の大型材を製造することは困難である。ＣＯ2削減，省資源などの観点から、より高効率な発電を実現するために蒸気温度を上昇させることが要求されている。現在実用されているフェライト系耐熱鋼の耐用温度は６００℃程度であるが、さらに蒸気温度を上昇させるためには、より耐用温度の高いＮｉ基耐熱合金を使用する必要がある。 On the other hand, high Cr ferritic heat-resistant steel has been used for steam turbine members used for coal-fired power generation. Ferritic heat-resisting steel is generally more manufacturable than Ni-based alloys, and can produce large forgings exceeding 20 tons such as turbine rotors. With Ni-based alloys, it is difficult to produce large materials equivalent to ferritic heat-resistant steel by current production technology. From the viewpoints of CO 2 reduction, resource saving, etc., it is required to raise the steam temperature in order to realize more efficient power generation. The useful temperature of ferritic heat-resistant steel currently in practical use is about 600 ° C., but in order to further increase the steam temperature, it is necessary to use a Ni-based heat-resistant alloy having a higher service temperature.
しかし前述のように、Ｎｉ基合金でフェライト系耐熱鋼と同等の大型材を製造することは困難であるため、最も高温になり、材料として過酷な条件に曝される部分のみをＮｉ基合金とし、他の部分は従来のフェライト系耐熱鋼からなる構造が提案されている。 However, as mentioned above, it is difficult to produce a large material equivalent to ferritic heat-resistant steel using a Ni-based alloy, so only the portion that is the highest temperature and is exposed to harsh conditions as a material is a Ni-based alloy. In other parts, a structure made of conventional ferritic heat resistant steel has been proposed.
このような構造では、Ｎｉ基合金とフェライト系耐熱鋼を溶接などの手法で接合する必要がある。従って、両者の特性の相違に起因する問題が懸念されており、それを解決することを目的とした発明が報告されている。特開平９−１５７７７９号公報（特許文献１），特開２０００−２５６７７０号公報（特許文献２）には、熱膨張係数差に起因する熱応力の緩和を目的とした低熱膨張係数のＮｉ基合金が提案されている。 In such a structure, it is necessary to join the Ni-based alloy and the ferritic heat resistant steel by a technique such as welding. Therefore, there are concerns about problems caused by the difference in characteristics between the two, and an invention for solving the problem has been reported. Japanese Laid-Open Patent Publication Nos. 9-157777 (Patent Document 1) and 2000-256770 (Patent Document 2) describe a Ni-based alloy having a low thermal expansion coefficient for the purpose of mitigating thermal stress caused by a difference in thermal expansion coefficient. Has been proposed.
継手構造を作製するための溶接に関して、一般的にＮｉ基合金はフェライト系耐熱鋼に比べて溶接が難しい。Ｎｉ基合金は１０００〜１１００℃で溶体化処理を行った後に、７５０〜１０００℃程度で時効処理を行い、強化相のγ′相を析出させるが、γ′相が析出した状態で溶接すると熱応力による割れが生じやすい。そのため、溶接作業はγ′相ができるだけ析出していない状態で行うことが望ましい。しかし、フェライト系耐熱鋼の７００℃以上の熱処理を行うと、強度が著しく損なわれるため、溶接後の熱処理温度は６００〜７００℃程度に制限される。そのため、６００〜７００℃程度の熱処理によってγ′相を多く析出させることができれば、高強度な継手構造が可能となるが、従来のＮｉ基合金はこの温度域でのγ′相析出量が少なく十分な強度が得られない。 Regarding welding for producing a joint structure, it is generally difficult to weld a Ni-based alloy as compared to a ferritic heat resistant steel. The Ni-based alloy is subjected to solution treatment at 1000 to 1100 ° C. and then subjected to aging treatment at about 750 to 1000 ° C. to precipitate the strengthening phase γ ′ phase. Cracks due to stress are likely to occur. Therefore, it is desirable to perform the welding operation in a state where the γ ′ phase is not precipitated as much as possible. However, if the heat treatment of the ferritic heat resistant steel at 700 ° C. or higher is performed, the strength is remarkably impaired, so the heat treatment temperature after welding is limited to about 600 to 700 ° C. Therefore, if a large amount of γ ′ phase can be precipitated by heat treatment at about 600 to 700 ° C., a high-strength joint structure is possible, but conventional Ni-based alloys have a small amount of γ ′ phase precipitation in this temperature range. Sufficient strength cannot be obtained.
そこで本願発明の課題は、溶接性と低温時効特性に優れ、フェライト系耐熱鋼と信頼性の高い溶接継手構造を可能にするフェライト鋼との接合に適したＮｉ基合金を提供すること、このようなＮｉ基合金を使用した蒸気タービン用高温部材を提供することにある。 Accordingly, an object of the present invention is to provide a Ni-based alloy that is excellent in weldability and low-temperature aging characteristics, and suitable for joining a ferritic heat resistant steel and a ferritic steel that enables a highly reliable welded joint structure. Another object of the present invention is to provide a high-temperature member for a steam turbine using a simple Ni-based alloy.
上記課題を解決するための本願発明の特徴点は、Ｃｏ：１２〜２５質量％，Ｃｒ：１０〜１８質量％，Ａｌ：２.０〜３.６質量％、ＷまたはＭｏの少なくともいずれかを含み、Ｗ，Ｍｏの合計量：５.０〜１０質量％，Ｃ：０.０１〜０.１５質量％，Ｂ：０.００１〜０.０３質量％を含み、残部がＮｉと不可避不純物からなるＮｉ基合金にある。 The feature of the present invention for solving the above problems is that Co: 12 to 25% by mass, Cr: 10 to 18% by mass, Al: 2.0 to 3.6% by mass, at least one of W or Mo. Including W and Mo in total amount: 5.0 to 10% by mass, C: 0.01 to 0.15% by mass, B: 0.001 to 0.03% by mass, the balance being Ni and inevitable impurities This is a Ni-based alloy.
本発明者らは、強度評価や熱力学計算等によってＮｉ基合金の研究を行い、特にＮｉ基合金の強化相であるγ′相の相安定性について詳細な調査を行った。その結果、γ′相の固溶温度（析出が起こる上限温度）が低く、溶接性に優れていると共に、６００〜７００℃におけるγ′相の析出量が多く、時効処理によって高強度が得られるＮｉ基合金の発明に至った。 The inventors of the present invention have studied Ni-based alloys by strength evaluation, thermodynamic calculation, and the like, and have conducted detailed investigations on the phase stability of the γ ′ phase, which is a strengthening phase of Ni-based alloys. As a result, the solid solution temperature (upper limit temperature at which precipitation occurs) of the γ ′ phase is low, the weldability is excellent, the amount of precipitation of the γ ′ phase at 600 to 700 ° C. is large, and high strength is obtained by aging treatment. The invention of the Ni-based alloy has been reached.
以下に、これらの合金元素の効果と合金組成の限定理由を述べる。 The effects of these alloy elements and the reasons for limiting the alloy composition will be described below.
Ｃｏは、Ｎｉと置換して母相に固溶して高温強度を向上させる効果があり、高温耐食性にも寄与する。本発明の合金組成範囲では、これらの効果が顕著に認められるのは１２％以上であるが、過剰な添加はσ相やμ相といった有害相の析出を助長するため、上限は２５％とした。好ましい範囲は１５〜２０％である。 Co has the effect of replacing Ni with solid solution in the matrix and improving the high temperature strength, and also contributes to high temperature corrosion resistance. In the alloy composition range of the present invention, these effects are remarkably observed at 12% or more, but excessive addition promotes precipitation of harmful phases such as σ phase and μ phase, so the upper limit was set at 25%. . A preferred range is 15-20%.
Ｃｒは、表面にＣｒ2Ｏ3からなる緻密な酸化皮膜を形成して耐酸化性，高温耐食性を向上させる元素である。本発明で対象とする高温部材に利用するためには少なくとも１２％を含有することが必要である。しかし１８％以上添加すると、σ相が析出して材料の延性，破壊靭性が悪化するため１８％を超えない範囲とする。特に好適な範囲は１３〜１７％である。 Cr is an element that improves the oxidation resistance and high-temperature corrosion resistance by forming a dense oxide film made of Cr 2 O 3 on the surface. In order to utilize for the high temperature member made into object by this invention, it is necessary to contain at least 12%. However, if added in an amount of 18% or more, the σ phase precipitates and the ductility and fracture toughness of the material deteriorate, so the range does not exceed 18%. A particularly preferred range is 13 to 17%.
Ａｌはγ′Ｎｉ3(Ａｌ，Ｔｉ)相を形成する元素であり、γ′相強化型耐熱合金の強化には不可欠な元素である。また、Ａｌ2Ｏ3を形成して耐酸化性にも寄与する。本合金では、Ａｌ量はγ′相の固溶温度，析出量を支配する主要な因子であり、不足の場合には時効によるγ′相析出量が少なく、十分な強度が得られない。反面、Ａｌ量が過剰になると、溶接性を阻害する。そのため、Ａｌ量の下限，上限はそれぞれ２.０％，３.６％とした。好ましい範囲は２.４〜３.５％である。 Al is an element that forms a γ'Ni 3 (Al, Ti) phase, and is an indispensable element for strengthening a γ 'phase strengthened heat-resistant alloy. In addition, Al 2 O 3 is formed to contribute to oxidation resistance. In this alloy, the amount of Al is a major factor governing the solid solution temperature and precipitation amount of the γ 'phase. If the amount is insufficient, the precipitation amount of γ' phase due to aging is small and sufficient strength cannot be obtained. On the other hand, if the Al amount is excessive, weldability is hindered. Therefore, the lower limit and upper limit of the Al amount are set to 2.0% and 3.6%, respectively. A preferable range is 2.4 to 3.5%.
Ｍｏ，Ｗは固溶強化によって母相を強化する効果がある。本発明の合金は、通常のＮｉ基耐熱合金で強化元素として添加されるＴｉ，Ｎｂ，Ｔａといった元素を含まないため、Ｍｏ，Ｗは比較的多量に添加している。十分な強化が得られるためには、５.０％以上の添加が必要であるが、１０％を超えると、硬質で脆い金属間化合物相の生成を助長したり、高温鍛造性の悪化を招いたりする。より好ましい範囲は、６〜９％である。 Mo and W have the effect of strengthening the matrix phase by solid solution strengthening. Since the alloy of the present invention does not contain elements such as Ti, Nb, and Ta which are added as strengthening elements in ordinary Ni-base heat-resistant alloys, Mo and W are added in relatively large amounts. In order to obtain sufficient strengthening, addition of 5.0% or more is necessary. However, if it exceeds 10%, formation of a hard and brittle intermetallic compound phase is promoted or high temperature forgeability is deteriorated. I'll be there. A more preferable range is 6 to 9%.
Ｃは母相に固溶して高温での引張強さを向上させると共に、ＭＣ，Ｍ23Ｃ6などの炭化物を形成することで粒界強度を向上させる。これらの効果は０.０１％程度から顕著になるが、過剰なＣの添加は粗大な共晶炭化物の原因となり、靭性の低下を招くため０.１５％を上限とする。０.０５〜０.１２％の添加量が好ましい。 C dissolves in the matrix and improves the tensile strength at high temperatures, and improves the grain boundary strength by forming carbides such as MC and M 23 C 6 . These effects become remarkable from about 0.01%, but excessive addition of C causes coarse eutectic carbides and causes toughness reduction, so 0.15% is made the upper limit. An addition amount of 0.05 to 0.12% is preferable.
Ｂは微量の添加で粒界を強化し、クリープ強度を改善する効果を有する。しかし、過剰な添加は有害相の析出や融点の低下による部分溶融の原因となることから、その適正範囲はＢ：０.００１〜０.０３とした。 B has the effect of strengthening the grain boundaries and improving the creep strength with a small amount of addition. However, excessive addition causes partial melting due to precipitation of harmful phases and a decrease in melting point, so the appropriate range was set to B: 0.001 to 0.03.
通常のＮｉ基耐熱合金は強化元素としてＴｉ，Ｎｂ，Ｔａといった元素を添加されているが、本発明の合金はこれらの元素を含まない。Ｔｉ，Ｎｂ，Ｔａは、γ′相を安定化して高温強度の上昇に寄与する元素であるが、固溶温度を高くする。本発明は溶接性と低温時効特性の両立を達成するため、固溶温度をなるべく低くし、かつγ′相析出量を増やすようにＡｌを使用してγ′相を安定化する。 Although ordinary Ni-base heat-resistant alloys are added with elements such as Ti, Nb, and Ta as strengthening elements, the alloy of the present invention does not contain these elements. Ti, Nb, and Ta are elements that stabilize the γ ′ phase and contribute to an increase in high-temperature strength, but increase the solid solution temperature. In the present invention, in order to achieve both weldability and low temperature aging characteristics, Al is used to stabilize the γ ′ phase so as to lower the solid solution temperature as much as possible and increase the amount of γ ′ phase precipitation.
図１は、各合金元素を１重量％増加させた場合のγ′相固溶温度の変化量と、７００℃におけるγ′相析出量の変化量を示している。Ｃｏ，Ｃｒ，Ｍｏ，Ｗに比べてＡｌ，Ｔｉ，Ｎｂ，Ｔａはγ′相安定化の効果が大きい。また、Ｔｉ，Ｎｂ，Ｔａは、固溶温度を大幅に上昇させるものの、析出量の増加に関してはＡｌには及ばないことが図から読み取れる。溶接性と時効特性を両立するためには、固溶温度をなるべく低くし、かつγ′相析出量を増やすようにＴｉ，Ｎｂ，Ｔａを添加せずにＡｌのみでγ′相を安定化した方が効果的である。 FIG. 1 shows the amount of change in the γ ′ phase solid solution temperature and the amount of change in the amount of γ ′ phase precipitation at 700 ° C. when each alloy element is increased by 1% by weight. Compared to Co, Cr, Mo, and W, Al, Ti, Nb, and Ta are more effective in stabilizing the γ 'phase. Further, it can be seen from the figure that Ti, Nb, and Ta greatly increase the solid solution temperature, but the amount of precipitation does not reach that of Al. In order to achieve both weldability and aging characteristics, the γ 'phase was stabilized with Al alone without adding Ti, Nb, or Ta so as to reduce the solid solution temperature as much as possible and increase the amount of γ' phase precipitation. Is more effective.
また、本発明では、γ′相の安定性を評価するパラメータを以下のように規定した。各元素の量はいずれも質量％である。 In the present invention, the parameters for evaluating the stability of the γ ′ phase are defined as follows. The amount of each element is mass%.
Ｆ＝１５.４５×（Ａｌ量）＋０.１×（Ｃｏ量）＋０.８×（Ｃｒ量）＋１.１５
×（Ｍｏ量）＋１.３×（Ｗ量） ・・・（１）
パラメータＦは７００℃におけるγ′相の析出量に関するパラメータである。式中の係数は、各元素がγ′相析出量に及ぼす影響を種々調査した結果から決定している。Ｃｏ，Ｃｒ，Ｍｏ，Ｗといった元素はＡｌに比べると、係数が小さくγ′相の析出量への影響は小さい。
F = 15.45 × (Al amount) + 0.1 × (Co amount) + 0.8 × (Cr amount) +1.15
× (Mo amount) + 1.3 × (W amount) (1)
The parameter F is a parameter relating to the precipitation amount of the γ ′ phase at 700 ° C. The coefficient in the formula is determined from the results of various investigations on the effect of each element on the amount of γ 'phase precipitation. Elements such as Co, Cr, Mo, and W have a smaller coefficient and less influence on the precipitation amount of the γ ′ phase than Al.
このパラメータを用いることで、高温に置けるγ′相の析出量を見積もることが可能である。また、Ｆの値が大きくなるほどγ′相が多くなるため合金の強度が上昇する。蒸気タービン材料としては、７００℃において１０％以上のγ′相の析出が望ましく、そのためにはＦが５４より大きくなるように各元素の成分を調整する必要がある。より好適な範囲としては、Ｆ＞５６となる組成が望ましい。 By using this parameter, it is possible to estimate the amount of precipitation of the γ ′ phase at high temperatures. Also, as the value of F increases, the γ 'phase increases and the strength of the alloy increases. As the steam turbine material, it is desirable that the γ ′ phase precipitates at 10% or more at 700 ° C. For this purpose, it is necessary to adjust the components of each element so that F is larger than 54. As a more preferable range, a composition satisfying F> 56 is desirable.
Ｔ＝１０８×（Ａｌ量）−（Ｃｏ量）＋４.５×（Ｃｒ量）＋９×（Ｍｏ量）
＋１０.５×（Ｗ量） ・・・（２）
一方、パラメータＴはγ′相の固溶温度に関するパラメータである。Ｔの値が大きくなると、γ′相の固溶温度が上昇することによって溶接が難しくなる。適当な溶接性を確保するためにはγ′相固溶温度が８５０℃より低いことが望ましく、そのためにはＴの値が５０５を上回らないようにする必要がある。より好適な範囲としては、Ｔ＜４８０であることが望ましい。
T = 108 × (Al amount) − (Co amount) + 4.5 × (Cr amount) + 9 × (Mo amount)
+ 10.5 × (W amount) (2)
On the other hand, the parameter T is a parameter relating to the solid solution temperature of the γ ′ phase. When the value of T is increased, welding becomes difficult due to an increase in the solid solution temperature of the γ ′ phase. In order to ensure appropriate weldability, it is desirable that the γ ′ phase solid solution temperature is lower than 850 ° C. For this purpose, it is necessary that the value of T does not exceed 505. As a more preferable range, it is desirable that T <480.
Ｆ，ＴはいずれもＡｌ，Ｃｏ，Ｃｒ，Ｍｏ，Ｗの関数であるため、両者を独立に制御することはできない。ＦとＴの望ましい範囲を同時に満たす組成を選択することによって、接合部の強度・信頼性と溶接性を両立した合金が可能となる。 Since F and T are all functions of Al, Co, Cr, Mo, and W, they cannot be controlled independently. By selecting a composition that satisfies the desired range of F and T at the same time, an alloy that achieves both strength and reliability of the joint and weldability becomes possible.
なお、各式の係数は、各元素が１％増減したときのγ′析出量，固溶温度の変分をもとに定めた。 The coefficient of each formula was determined based on the amount of precipitation of γ ′ and the variation of the solid solution temperature when each element increased or decreased by 1%.
本発明により、溶接性と時効特性に優れ、フェライト鋼との接合に適したＮｉ基耐熱合金を提供することができる。 According to the present invention, it is possible to provide a Ni-base heat-resistant alloy that has excellent weldability and aging characteristics and is suitable for joining with ferritic steel.
表１に、本発明合金と本発明にいたる過程で実験に供した比較合金の化学組成を示す。 Table 1 shows the chemical composition of the alloy of the present invention and the comparative alloy subjected to the experiment in the process leading to the present invention.
Ｎo.１〜８が本発明であり、Ｎo.９〜１２は比較合金である。Ｎo.１３〜１６は実用化されているＮｉ基合金を公知合金として示した。公知合金にはＴｉ，Ｎｂ，Ｔａが合金元素として添加されている点で異なる。表１には各合金のパラメータＦ，Ｔもあわせて示している。比較例９〜１０，１１〜１２はそれぞれＦ，Ｔの値が請求範囲から外れている。 Nos. 1 to 8 are the present invention, and Nos. 9 to 12 are comparative alloys. Nos. 13 to 16 show Ni-based alloys in practical use as known alloys. A known alloy is different in that Ti, Nb, and Ta are added as alloy elements. Table 1 also shows the parameters F and T of each alloy. In Comparative Examples 9 to 10 and 11 to 12, the values of F and T are out of the claims.
図２，図３はそれぞれ、表中のγ′相析出量（７００℃）とパラメータＦ、γ′相固溶温度とパラメータＴの相関を示した図である。パラメータＦが大きくなるほど析出量も多くなる傾向が現れている。Ｆ＞５４の合金では、７００℃において１０％以上の析出量が得られている。また同様に、固溶温度とパラメータＴにも明らかな相関が見られ、Ｔ＜５０５であれば固溶温度は８４０℃以下になっている。 2 and 3 are graphs showing the correlation between the γ ′ phase precipitation amount (700 ° C.) and the parameter F, the γ ′ phase solid solution temperature and the parameter T in the table, respectively. There is a tendency that the amount of precipitation increases as the parameter F increases. In the case of F> 54, an amount of precipitation of 10% or more is obtained at 700 ° C. Similarly, there is a clear correlation between the solid solution temperature and the parameter T. If T <505, the solid solution temperature is 840 ° C. or lower.
これらの組成の合金インゴットを真空溶解により１０kg作製し、１０００〜１１５０℃における熱間加工によりφ１５mmの丸棒形状に加工した。溶体化処理：９８０℃２時間，一次時効処理：８４０℃８時間，二次時効処理：６００〜７３０℃での各温度で２４時間を施した後に、機械加工により引張クリープ試験片（平行部長さ：３０mm，直径：６mm）を作製した。 10 kg of alloy ingots having these compositions were produced by vacuum melting and processed into a round bar shape of φ15 mm by hot working at 1000 to 1150 ° C. Solution treatment: 980 ° C. for 2 hours, Primary aging treatment: 840 ° C. for 8 hours, Secondary aging treatment: After applying 24 hours at each temperature of 600 to 730 ° C., tensile creep test piece (parallel part length) : 30 mm, diameter: 6 mm).
図４は、発明合金（Ｎo.１）と比較合金（Ｎo.９，１１）の時効特性を示している。Ｎo.１は溶体化処理後のビッカース硬さの値がＨｖ＝２２０であり、一次時効を行っても硬さの上昇は見られない。これは、Ｔ値が低く、一次時効温度でγ′相が析出しないためである。一次時効は、Ｎｉ基合金の延性改善に効果的であるが、フェライト鋼をこの温度域に加熱すると特性を著しく損なうため、接合前に実施することが必須である。しかし、Ｎo.１１のようにＴ値の高い合金では、一次時効によってγ′相が析出して硬さが上昇してしまうため、溶接性が悪化する。発明合金ではＴが規定する値以下であるため一次時効を行っても硬さの上昇は見られず良好な溶接性が維持される。 FIG. 4 shows the aging characteristics of the inventive alloy (No. 1) and the comparative alloys (No. 9, 11). In No. 1, the value of Vickers hardness after solution treatment is Hv = 220, and no increase in hardness is observed even when primary aging is performed. This is because the T value is low and the γ ′ phase does not precipitate at the primary aging temperature. Primary aging is effective in improving the ductility of Ni-based alloys, but it is essential to perform it before joining because heating the ferritic steel to this temperature range significantly impairs the properties. However, in an alloy having a high T value such as No. 11, weldability deteriorates because the γ 'phase precipitates due to primary aging and the hardness increases. In the alloy according to the invention, since T is not more than a specified value, even if primary aging is performed, no increase in hardness is observed and good weldability is maintained.
Ｎo.１合金はその後の二次時効によって析出強化し、硬さが上昇している。時効温度６５０℃以上での硬さの上昇が顕著であり、他の発明合金も６５０〜７００℃において硬さが最も上昇した。Ｎo.９合金は一次時効後の硬さの上昇は見られないものの、二次時効による硬さの上昇も発明合金に比べて小さい。Ｆ値が小さく、γ′相の析出量が少ないためである。 The No. 1 alloy is precipitation strengthened by the subsequent secondary aging, and the hardness is increased. The increase in hardness was remarkable at an aging temperature of 650 ° C. or higher, and the hardness of other invention alloys also increased most at 650 to 700 ° C. The No. 9 alloy shows no increase in hardness after primary aging, but the increase in hardness due to secondary aging is also smaller than that of the invention alloy. This is because the F value is small and the amount of precipitation of the γ ′ phase is small.
図５は、各合金のγ′相の固溶温度と析出量の相関を示している。発明合金と比較合金に比べて、Ｔｉ，Ｎｂ，Ｔａを強化元素として含む公知合金は、同程度の析出量であっても固溶温度が高く、溶接性の観点で発明合金の方が優れている。フェライト鋼との溶接による接合を対象とした場合、固溶温度は８４０℃以下であることが望ましく、またクリープ強度の観点からはγ′析出量が１０％以上であることが必要である。発明合金はいずれもこの範囲に入っている。（１）（２）式で表されるパラメータＦ，ＴがそれぞれＦ＞５４，Ｔ＜５０５を満たすように合金組成を選定してγ′相の固溶温度と析出量を適切に制御することで、溶接性と時効特性に優れ、フェライト鋼との接合に適したＮｉ基合金が得られた。 FIG. 5 shows the correlation between the solid solution temperature and precipitation amount of the γ ′ phase of each alloy. Compared with the invention alloy and the comparative alloy, the known alloy containing Ti, Nb, Ta as a strengthening element has a higher solid solution temperature even with the same amount of precipitation, and the invention alloy is superior from the viewpoint of weldability. Yes. In the case of joining with ferritic steel by welding, the solid solution temperature is desirably 840 ° C. or less, and from the viewpoint of creep strength, the γ ′ precipitation amount is required to be 10% or more. All inventive alloys fall within this range. (1) The alloy composition should be selected so that the parameters F and T represented by the formula (2) satisfy F> 54 and T <505, respectively, and the solid solution temperature and precipitation amount of the γ ′ phase should be controlled appropriately. Thus, a Ni-based alloy excellent in weldability and aging characteristics and suitable for joining with ferritic steel was obtained.
図６，図７に、各合金のクリープ破断時間と伸びとをそれぞれ示す。供試材の二次時効温度は６５０℃とし、クリープ試験条件は７００℃，２９４ＭＰａである。 6 and 7 show the creep rupture time and elongation of each alloy, respectively. The secondary aging temperature of the test material is 650 ° C., and the creep test conditions are 700 ° C. and 294 MPa.
図６に示したように、発明合金の破断時間はいずれも３００時間程度である。これは、蒸気タービンの耐用温度では約７００℃に相当する。したがって、従来のフェライト系耐熱鋼の耐用温度６３０℃に比べて高温強度に優れていることが明らかであり、継手構造を作製した場合にも十分な信頼性が得られる。 As shown in FIG. 6, the break times of the inventive alloys are all about 300 hours. This corresponds to about 700 ° C. in the service temperature of the steam turbine. Therefore, it is clear that the high-temperature strength is superior to the service temperature of 630 ° C. of conventional ferritic heat-resistant steel, and sufficient reliability can be obtained even when a joint structure is produced.
また、図７より明らかなように、発明合金では２０％前後のクリープ伸びが得られており、高温延性の面でも実用上問題ない程度であることを確認した。比較例のうちＮo.１１，１２は、γ′相による析出強化が十分でないため破断時間が短く、十分な継手強度が得られていない。 Further, as apparent from FIG. 7, it was confirmed that the inventive alloy had a creep elongation of about 20%, and that there was no practical problem in terms of high temperature ductility. Of the comparative examples, Nos. 11 and 12 are not sufficiently strengthened by precipitation by the γ 'phase, so that the fracture time is short and sufficient joint strength is not obtained.
図８は、γ′相析出量とクリープ破断時間の相関を示す図である。γ′相析出量が増加するにしたがって破断時間も大きくなる傾向が見られる。Ｎo.１１，１２およびＴｉ，Ｎｂ，Ｔａを添加したＮo.１３〜１６合金はいずれもクリープ破断時間は長く強度には優れているものの、その反面、図５から分かるようにγ′相固溶温度が高くなるため、溶接は困難になる。 FIG. 8 is a diagram showing the correlation between the amount of γ ′ phase precipitation and the creep rupture time. As the amount of γ 'phase precipitation increases, the fracture time tends to increase. Nos. 11 and 12 and Nos. 13 to 16 alloys added with Ti, Nb, and Ta all have a long creep rupture time and excellent strength, but on the other hand, as shown in FIG. Because of the high temperature, welding becomes difficult.
本発明合金は、発電用蒸気タービンのロータシャフト，中間リングとして利用する他、溶接ワイヤ、あるいは溶接棒に加工して、溶接金属として利用することも可能である。 The alloy of the present invention can be used as a weld metal by being processed into a welding wire or a welding rod, in addition to being used as a rotor shaft and an intermediate ring of a steam turbine for power generation.
本発明におけるＮｉ基合金は、フェライト系耐熱鋼との接合性に優れ、蒸気タービン部材に利用可能である。 The Ni-based alloy in the present invention is excellent in bondability with a ferritic heat resistant steel and can be used for a steam turbine member.
Claims (6)
各成分を質量で、Ｃｏ：１２〜２５％，Ｃｒ：１０〜１８％，Ａｌ：２.０〜３.６％，Ｃ：０.０１〜０.１５％，Ｂ：０.００１〜０.０３％含有し、タングステンとモリブデンの合計量がＷ＋Ｍｏ：５.０〜１０％であるＮｉ基合金。 Ni-based alloy containing cobalt, chromium, aluminum, carbon, boron, containing at least one of tungsten and molybdenum, the balance being nickel and inevitable impurities,
By weight, each component is Co: 12-25%, Cr: 10-18%, Al: 2.0-3.6%, C: 0.01-0.15%, B: 0.001-0. A Ni-based alloy containing 03% and having a total amount of tungsten and molybdenum of W + Mo: 5.0 to 10%.
各成分を質量で、Ｃｏ：１５〜２０％，Ｃｒ：１３〜１７％，Ａｌ：２.４〜３.５％，タングステンとモリブデンの少なくともいずれかを含み、タングステンおよびモリブデンの合計量Ｗ＋Ｍｏ：６〜９％，Ｃ：０.０５〜０.１２％，Ｂ：０.００１〜０.０３含むことを特徴とするＮｉ基合金。 The Ni-based alloy according to claim 1,
Each component contains, by mass, Co: 15 to 20%, Cr: 13 to 17%, Al: 2.4 to 3.5%, at least one of tungsten and molybdenum, and the total amount of tungsten and molybdenum W + Mo: 6 Ni-base alloy characterized by containing -9%, C: 0.05-0.12%, B: 0.001-0.03.
Ｆ＝１５.４５×（Ａｌ量）＋０.１×（Ｃｏ量）＋０.８×（Ｃｒ量）＋１.１５
×（Ｍｏ量）＋１.３×（Ｗ量）（各元素量の単位は質量％） ・・・（１）
Ｔ＝１０８×（Ａｌ量）−（Ｃｏ量）＋４.５×（Ｃｒ量）＋９×（Ｍｏ量）
＋１０.５×（Ｗ量）（各元素量の単位は質量％） ・・・（２） The Ni-based alloy according to claim 1 or 2, wherein the composition parameter F represented by the following equation (1) is F> 54, and the composition parameter T represented by the following equation (2) is: Ni-base alloy characterized by T <505.
F = 15.45 × (Al amount) + 0.1 × (Co amount) + 0.8 × (Cr amount) +1.15
X (Mo amount) + 1.3 x (W amount) (unit of each element amount is mass%) (1)
T = 108 × (Al amount) − (Co amount) + 4.5 × (Cr amount) + 9 × (Mo amount)
+ 10.5 × (W amount) (unit of each element amount is mass%) (2)
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| EP09169007.3A EP2172299B1 (en) | 2008-09-09 | 2009-08-31 | Welded rotor for turbine and method for manufacturing the same |
| US12/551,884 US8883072B2 (en) | 2008-09-09 | 2009-09-01 | Ni-base alloy, high-temperature member for steam turbine and welded rotor for turbine using the same, and method for manufacturing the same |
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| CN103358050A (en) * | 2012-03-30 | 2013-10-23 | 株式会社日立制作所 | An Ni-based alloy for a welding material, a welding wire and a welding rod employing the material, and a welding power |
| JP2013216939A (en) * | 2012-04-06 | 2013-10-24 | Nippon Steel & Sumitomo Metal Corp | Nickel-based heat-resistant alloy |
| CN105422185A (en) * | 2014-09-16 | 2016-03-23 | 霍尼韦尔国际公司 | Turbocharger shaft and wheel assembly |
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| JP2004136301A (en) * | 2002-10-16 | 2004-05-13 | Hitachi Ltd | Welding material, welded structure, blade of gas turbine, and method for repairing rotary blade or stationary blade of gas turbine |
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| JP2004136301A (en) * | 2002-10-16 | 2004-05-13 | Hitachi Ltd | Welding material, welded structure, blade of gas turbine, and method for repairing rotary blade or stationary blade of gas turbine |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103358050A (en) * | 2012-03-30 | 2013-10-23 | 株式会社日立制作所 | An Ni-based alloy for a welding material, a welding wire and a welding rod employing the material, and a welding power |
| EP2677053A1 (en) | 2012-03-30 | 2013-12-25 | Hitachi Ltd. | Ni-based alloy for welding material and welding wire, rod and powder |
| US9878403B2 (en) | 2012-03-30 | 2018-01-30 | Mitsubishi Hitachi Power Systems, Ltd. | Ni-based alloy for welding material and welding wire, rod and power |
| JP2013216939A (en) * | 2012-04-06 | 2013-10-24 | Nippon Steel & Sumitomo Metal Corp | Nickel-based heat-resistant alloy |
| CN105422185A (en) * | 2014-09-16 | 2016-03-23 | 霍尼韦尔国际公司 | Turbocharger shaft and wheel assembly |
| CN105422185B (en) * | 2014-09-16 | 2019-10-22 | 盖瑞特交通一公司 | Turbo-charger shaft and impeller assembly |
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