JP3723924B2 - Heat-resistant cast steel and method for producing the same - Google Patents
Heat-resistant cast steel and method for producing the same Download PDFInfo
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Description
【0001】
【発明の属する技術分野】
本発明は、火力発電プラントにおけるタービンケーシングやバルブ類等に使用される耐熱鋳鋼およびその製造方法に関するものである。
【0002】
【従来の技術】
近年、大型火力発電プラントでは出力を増大させるために、超々臨界圧で使用されるタービンの開発が進められている。このような超々臨界圧下で用いられるタービンケーシング、フランジ、バルブ等の材料としては、蒸気タービン用鋳鋼品が使用されており、この鋳鋼品には、苛酷な使用環境に耐えられるように、高温特性に優れていることは勿論のこと、高靱性で経年劣化の少ないことが要求される。 従来、このような観点から、上記用途に使用される鋳鋼品としては、12Cr−Mo−V−Nb−N鋳鋼や12Cr−Mo−V−Nb−N−W鋳鋼等が使用されている。
【0003】
【発明が解決しようとする課題】
しかし、蒸気温度の高温高圧化に伴い、従来の耐熱鋳鋼では、クリープ破断強度が十分でないため、より高いクリープ破断強度を有し、かつ延靱性が良好で高温強度にも優れた12Cr系耐熱鋳鋼の開発が望まれている。
本発明は、上記事情を背景としてなされたものであり、延靱性、高温強度ともに優れ、特に高温クリープ破断強度に優れた新規の12Cr系の耐熱鋳鋼とその製造方法を提供することを目的とするものである。
【0004】
【課題を解決するための手段】
上記課題を解決するため、本願発明のうち第1の発明の耐熱鋳鋼は、重量%で、C:0.05〜0.15%、Mn:0.10〜1.50%、Ni:1.0%以下、Cr:9.0〜13.0%、Mo:0.65〜1.5%、V:0.1〜0.3%、N:0.005〜0.10%、W:0.1〜5.0%、Co:1.5〜5.0%、B:0.004〜0.022%を含有し、残部がFeおよび不可避不純物からなることを特徴とする。
第2の発明の耐熱鋳鋼は、第1の発明の組成に、さらに重量%で、Nb:0.01〜0.2%、Ta:0.01〜0.2%、Ti:0.1%以下の1種以上を含有することを特徴とする。
【0005】
【作用】
以下に本願発明の作用を、各成分の限定理由とともに説明する。
C:0.05〜0.15%
Cは、炭化物生成元素と結びついて炭化物を形成し、高温強度を向上させるが0.05%未満であると強度が不十分であり、一方、0.15%を超えると炭化物が粗大化し高温性質を低下させるので、その範囲を0.05〜0.15%とした。 なお、同様の理由で下限を0.09%、上限を0.13%とするのが望ましい。
【0006】
Mn:0.10〜1.50%
Mnは、Siとともに脱酸剤として使用される元素であり、十分な脱酸効果を得るためには0.10%以上の含有が必要であるが、1.50%を超えて含有させると靱性を損なうため、0.10〜1.50%に限定した。なお、同様の理由で下限を0.45%、上限を0.70%とするのが望ましい。
Ni:1.0%以下
Niは焼入れ性を向上させ、またFATT、靱性を改善する元素であり、0.25%以上含有させるのが望ましいが、1.0%を超えて含有させると高温クリープ強さが低下するためその許容範囲を1.0%以下とした。なお、望ましくは0.30〜0.70%を含有させる。
一方、主として高温特性の改善を目的とする場合はNiを添加しない。この場合、原材料より不可避的に混入することを考慮し、0.25%未満を不純物として許容する。
【0007】
Cr:9.0〜13.0%
Crは、この鋼種において焼入性、高温強度を高める基本合金成分であり、9.0%以上必要であるが、13.0%を越えて含有させるとδフェライトが晶出して高温性質および切欠靭性を劣化させるので、その上限を13.0%とした。なお、同様の理由で望ましくは下限を9.5、上限を10.5%とする。
Mo:0.65〜1.5%
Moは、焼戻軟化抵抗を高め、また高温強度を改善するために0.65%以上必要であるが、1.5%を超えて含有させても、それ以上の効果は期待できず、また有害なδフェライトが生成しクリープ破断強度を低下させるため0.65〜1.5%に限定した。なお、同様の理由で、上限を0.95%とするのが望ましい。
【0008】
V:0.1〜0.3%
Vは、安定した炭化物を形成しクリープ強度を向上させる作用を有するが、0.1%未満だと効果はなく、一方、0.3%を超えて含有させると延靱性が低下するので0.1〜0.3%に限定した。なお、同様の理由で下限を0.15%、上限を0.25%とするのが望ましい。
N:0.005〜0.10%
Nは、基地を強化するばかりでなく、Moと共存してクリープ強度の向上に有効に作用する。その含有量が0.005%未満では、その効果が認められず、また0.10%を越えて含有させるとブローホールを発生するので、その含有量を0.005〜0.10%とした。なお、同様の理由で下限を0.01%、上限を0.06%とするのが望ましい。
【0009】
W:0.1〜5.0%
Wは、高温強度を向上させるために含有させるが、0.1%未満だと、その効果はなく、一方、5.0%を越えて含有させると偏析傾向が増大し、また延靱性を低下させるので0.1〜5.0%に限定した。なお、同様の理由で下限を1.5%、上限を3.5%とするのが望ましい。
Co:0.1〜5.0%
Coは、δフェライトの析出を抑えることで衝撃性質を向上させ、またクリープ破断強度を向上させるために含有させる。ただし、0.1%未満では、その効果がなく、5.0%を越えて添加すると、その効果が飽和するため、0.1%〜5.0%に限定した。なお、同様の理由で下限を1.5%、上限を3.5%とするのが望ましい。
【0010】
B:0.001〜0.022%
Bは、微量の含有で焼入れ性が増大し、靱性を向上させるとともに粒界および粒内の炭化物の析出凝集を抑え、高温クリープ強さに寄与する。しかし、その含有量は、0.001%未満では、上記効果が不十分である。また、0.022%を越えると高温クリープ延性が著しく低下するため、さらに溶接性を悪化させるためその含有量を0.001〜0.022%に限定した。なお、同様の理由で下限を0.002%、上限を0.015%とするのが望ましい。さらには0.003〜0.007%とするのが一層望ましい。
【0011】
Nb:0.01〜0.2%
Nbは、微細な炭窒化物を形成し高温強度を向上させるので選択成分として含有させる。ただし、0.01%未満の含有では効果はなく、0.2%を越えて含有させると炭窒化物が増大し、延靱性を低下させるため、その範囲を0.01〜0.2%とした。なお、同様の理由で下限を0.03%、上限を0.12%とするのが望ましい。
Ta:0.01〜0.2%
Taは、微細な炭化物を析出し高温強度を向上させるので選択成分として含有させる。ただし、0.01%未満の含有では効果がなく、0.2%を越えて含有させると炭化物が増大し、延靱性を低下させるため、その範囲を0.01〜0.2%とした。なお、同様の理由で下限を0.03%、上限を0.12%とするのが望ましい。
Ti:0.1%以下
Tiは、脱酸剤の一つであり、また炭化物あるいは窒化物を形成し高温特性を向上させるので選択成分として含有させる。ただし、0.1%を越えて含有させると介在物を多く発生させて延靱性を低下させるので上限を0.1%とした。なお、同様の理由で上限を0.05%とするのが望ましい。
【0012】
その他
Siは脱酸剤として使用されるため不可避的に含有される。しかし、その含有量を低減していくとマクロ偏析、特に逆V偏析が軽微となり、肉厚内部における延性および切欠靱性の不均一性が改善される。また、Si含有量が高いと焼戻脆化感受性が極めて大となり、切欠靱性が損なわれる。したがって、Si含有量は低い方が望ましい。しかし脱酸剤として使用される元素であり、その上限を極端に低く定めることは製造上の裕度が小さく実用的でないので0.20%未満を不純物として許容する。
【0013】
本発明の耐熱鋳鋼において対象としているケーシング等は鋳込重量10〜150トン(製品重量が5〜50トン)程度の大型になるので、内部品質の良好な鋳鋼を製作するためには高度な製鋼技術および鋳造技術が必要となる。本発明における耐熱鋳鋼は、合金材料を電気炉にて溶解し、炉外精錬にて精錬、脱ガスを十分行い、また積極的に指向性凝固させる砂型鋳型を使用して、鋳込み成形することにより鋳造欠陥の少ない健全な鋳鋼が製造でき、上記大型のケーシング等に好適な材料が得られる。
【0014】
また、鋳込み成形された耐熱鋳鋼を1000〜1150℃で焼鈍し、1000〜1200℃に加熱し強制冷却する焼準を行い、その後500〜700℃で焼戻、続いて700〜780℃で第2段目の焼戻を行うことで、高いクリープ破断強度が確保できる。
なお、焼鈍および焼準温度は、炭窒化物の固溶およびδフェライトの分解を行うために1000℃以上とする必要があるが、高すぎると結晶粒の粗大化やδフェライトへの再変態が起きるので上限温度1150℃或いは1200℃とした。また2回の焼戻により、残留オーステナイトを完全に分解し、均一なマルテンサイト組織が得られ、さらに炭窒化物を微細析出させクリープ破断強度を向上することができる。
【0015】
なお、本発明鋼は必要に応じて構造溶接、補修溶接等の溶接を行うことができ、例えば、上記した一連の熱処理後、溶接を行い、その後、650℃〜760℃の応力除去焼鈍を行う。
また、該溶接は、上記一連の工程途中、すなわち、焼鈍後であって、焼準の前に行うことができ、その後は、上記工程に従って、焼準、焼戻、第2段目の焼戻が行われる。この場合、上記した応力除去焼鈍は不要となる。また、この工程(熱処理中途の溶接工程を含む)においては、必要に応じて、上記第2段目の焼戻後に、さらに、溶接を行うことも可能であり、該溶接後には、上記した応力除去焼鈍を行う。
上記のように、熱処理工程の中途に溶接工程を含む場合には、構造溶接部や補修溶接部に対しても、上記と同様の焼準、焼戻が行われるため、溶接部においても高いクリープ破断強度と良好な靭性が確保できる。
【0016】
【実施例】
(実施例1)
表1、2に示す組成を有する合金(実施例および比較例)を、真空溶解炉にて溶製し、砂型に鋳込んだyブロック50kg鋼塊を試験材とした。これらの試験材に所定の熱処理を施した後、機械的性質および溶接性を評価し、その結果を表3に示した。
溶接性の評価は図1に示した平板1(280mm長×100mm幅×30mm厚)を製作し、その板面に所定の溶接棒により3パスの溶接を行い、その後、溶接ビード2に垂直な5断面について割れ発生の有無を調査した。この結果をB含有量との関係で整理したものを図2に示した。
表3および図2から明らかなように本発明材はクリープ破断強度と溶接性に優れていることが明らかとなった。
【0017】
【表1】
【0018】
【表2】
【0019】
【表3】
【0020】
(実施例2)
本発明の耐熱鋳鋼を目標達成とする合金原料を電気炉で溶解し、炉外精錬により組成調整後、脱ガス等を行い砂型鋳型で鋳込み成形して、鋳込重量20トン(製品重量約9トン)のモデルケーシングを製作した。この鋳鋼を1070℃で20時間保持後炉冷の焼鈍を行い、1070℃で10時間保持後強制冷却の焼準を行い、さらに第1段焼戻として570℃で8時間保持後空冷し、続いて第2段目の焼戻として740℃で16時間保持後炉冷した。
このモデルケーシングの機械的性質を評価したところ、クリープ破断強度は600℃の105時間で12kgf/mm2、625℃の105時間で9kgf/mm2、FATT60℃を確保できた。
【0021】
【発明の効果】
以上説明したように本発明の耐熱鋳鋼によれば、重量%で、C:0.05〜0.15%、Mn:0.10〜1.50%、Ni:1.0%以下、Cr:9.0〜13.0%、Mo:0.65〜1.5%、V:0.1〜0.3%、N:0.005〜0.10%、W:0.1〜5.0%、Co:1.5〜5.0%、B:0.004〜0.022%を含有し、さらに所望により、Nb:0.01〜0.2%、Ta:0.01〜0.2%、Ti:0.1%以下の1種以上を含有し、残部がFeおよび不可避不純物からなるので、延靭性、高温強度に優れ、特にクリープ破断強度が向上し、また溶接性も優れている。この特性により、より高温高圧化された火力発電プラントでの使用が可能になり、発電プラントでの高効率化、高出力化に寄与することができる。
【0022】
また、上記鋳塊を製造する際に、合金原料を電気炉にて溶解し、炉外精錬にて精錬後、砂型鋳型に鋳込み成形すれば、鋳造欠陥が少なく内部品質の良好な鋳鋼を製造することができ、大型のケーシング等に好適な材料を提供することができる。
【0023】
また、上記工程により鋳込み成形された耐熱鋳鋼を1000〜1150℃で焼鈍し、1000〜1200℃に加熱し強制冷却する焼準を行い、その後500〜700℃で焼戻、続いて700〜780℃で第2段目の焼戻を行えば、高いクリープ破断強度が確保でき、靭性も向上させることができる。
【図面の簡単な説明】
【図1】 溶接評価試験片における切断位置を示す概略図である。
【図2】 B含有量と溶接割れ率との関係を示すグラフである。
【符号の説明】
1 平板
2 溶接ビード[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heat-resistant cast steel used for a turbine casing, valves and the like in a thermal power plant and a method for producing the same.
[0002]
[Prior art]
In recent years, large-scale thermal power plants have been developing turbines that are used at ultra-supercritical pressures in order to increase output. Cast turbine products for steam turbines are used as materials for turbine casings, flanges, valves, etc. used under such super-supercritical pressures, and these cast steel products have high temperature characteristics so that they can withstand harsh usage environments. Of course, it is required to have high toughness and little deterioration over time. Conventionally, from this point of view, 12Cr—Mo—V—Nb—N cast steel, 12Cr—Mo—V—Nb—N—W cast steel, and the like are used as cast steel products used for the above applications.
[0003]
[Problems to be solved by the invention]
However, with the increase in steam temperature, the conventional heat-resistant cast steel has insufficient creep rupture strength, so it has higher creep rupture strength, good ductility and good high-temperature strength. Development is desired.
The present invention has been made against the background described above, and an object thereof is to provide a novel 12Cr heat-resistant cast steel excellent in both ductility and high-temperature strength, particularly excellent in high-temperature creep rupture strength, and a method for producing the same. Is.
[0004]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the heat-resistant cast steel according to the first invention of the present invention is C: 0.05-0.15%, Mn: 0.10-1.50%, Ni: 1. 0% or less, Cr: 9.0 to 13.0%, Mo: 0.65 to 1.5%, V: 0.1 to 0.3%, N: 0.005 to 0.10%, W: It contains 0.1 to 5.0%, Co: 1.5 to 5.0%, B: 0.004 to 0.022%, and the balance is made of Fe and inevitable impurities.
In the heat-resistant cast steel of the second invention, the composition of the first invention is further weight percent, Nb: 0.01 to 0.2%, Ta: 0.01 to 0.2%, Ti: 0.1% It contains one or more of the following .
[0005]
[Action]
The operation of the present invention will be described below together with the reasons for limiting each component.
C: 0.05 to 0.15%
C forms carbides in combination with carbide-forming elements and improves high-temperature strength. However, if it is less than 0.05%, the strength is insufficient. On the other hand, if it exceeds 0.15%, the carbide becomes coarse and high-temperature properties are increased. Therefore, the range was made 0.05 to 0.15%. For the same reason, it is desirable that the lower limit is 0.09% and the upper limit is 0.13%.
[0006]
Mn: 0.10 to 1.50%
Mn is an element used as a deoxidizing agent together with Si. To obtain a sufficient deoxidizing effect, Mn is required to be contained in an amount of 0.10% or more. Therefore, the content is limited to 0.10 to 1.50%. For the same reason, it is desirable to set the lower limit to 0.45% and the upper limit to 0.70%.
Ni: 1.0% or less Ni is an element that improves hardenability and improves FATT and toughness, and is preferably contained in an amount of 0.25% or more. Since the strength decreases, the allowable range is set to 1.0% or less. Desirably, 0.30 to 0.70% is contained.
On the other hand, Ni is not added mainly for the purpose of improving high temperature characteristics. In this case, in consideration of inevitable mixing from the raw material, less than 0.25% is allowed as an impurity.
[0007]
Cr: 9.0 to 13.0%
Cr is a basic alloy component that enhances hardenability and high-temperature strength in this steel type, and is required to be 9.0% or more. However, if it exceeds 13.0%, δ ferrite crystallizes, and high-temperature properties and notches are required. Since the toughness is deteriorated, the upper limit is set to 13.0%. For the same reason, the lower limit is preferably 9.5 and the upper limit is 10.5%.
Mo: 0.65 to 1.5%
Mo needs to be 0.65% or more in order to increase the temper softening resistance and improve the high temperature strength, but even if it exceeds 1.5%, no further effect can be expected. In order to generate harmful δ ferrite and reduce the creep rupture strength, the content was limited to 0.65 to 1.5%. For the same reason , the upper limit is desirably 0.95%.
[0008]
V: 0.1 to 0.3%
V has the effect of forming a stable carbide and improving the creep strength. However, if less than 0.1%, there is no effect. Limited to 1-0.3%. For the same reason, it is desirable to set the lower limit to 0.15% and the upper limit to 0.25%.
N: 0.005-0.10%
N not only strengthens the base, but also effectively coexists with Mo and improves the creep strength. If the content is less than 0.005%, the effect is not recognized, and if it exceeds 0.10%, blowholes are generated, so the content was made 0.005 to 0.10%. . For the same reason, it is desirable to set the lower limit to 0.01% and the upper limit to 0.06%.
[0009]
W: 0.1-5.0%
W is added to improve the high temperature strength, but if it is less than 0.1%, there is no effect. On the other hand, if it exceeds 5.0%, the segregation tendency increases and the ductility decreases. Therefore, it was limited to 0.1 to 5.0%. For the same reason, it is desirable to set the lower limit to 1.5% and the upper limit to 3.5%.
Co: 0.1-5.0%
Co is contained in order to improve the impact properties by suppressing the precipitation of δ ferrite and to improve the creep rupture strength. However, if the content is less than 0.1%, the effect is not obtained. If the content exceeds 5.0%, the effect is saturated, so the content is limited to 0.1% to 5.0%. For the same reason, it is desirable to set the lower limit to 1.5% and the upper limit to 3.5%.
[0010]
B: 0.001 to 0.022%
B is contained in a small amount to increase hardenability, improve toughness, suppress precipitation and aggregation of carbides in grain boundaries and grains, and contribute to high temperature creep strength. However, the content is less than 0.001%, the above effects are insufficient. Moreover, since the high temperature creep ductility will fall remarkably when it exceeds 0.022%, in order to worsen weldability further, the content was limited to 0.001-0.022%. For the same reason, it is desirable that the lower limit is 0.002% and the upper limit is 0.015%. Furthermore, it is more desirable to set it as 0.003 to 0.007%.
[0011]
Nb: 0.01 to 0.2%
Nb is included as a selective component because it forms fine carbonitrides and improves high-temperature strength. However, if the content is less than 0.01%, there is no effect, and if the content exceeds 0.2%, the carbonitride increases and the toughness decreases, so the range is 0.01-0.2%. did. For the same reason, it is desirable that the lower limit is 0.03% and the upper limit is 0.12%.
Ta: 0.01 to 0.2%
Ta precipitates fine carbides and improves the high-temperature strength, so is included as a selective component. However, if the content is less than 0.01%, there is no effect, and if the content exceeds 0.2%, the carbide increases and the ductility is lowered, so the range was made 0.01 to 0.2%. For the same reason, it is desirable that the lower limit is 0.03% and the upper limit is 0.12%.
Ti: 0.1% or less Ti is one of deoxidizers, and forms carbides or nitrides to improve high temperature characteristics, so is included as a selective component. However, if the content exceeds 0.1%, more inclusions are generated and the ductility is lowered, so the upper limit was made 0.1%. For the same reason, it is desirable to set the upper limit to 0.05%.
[0012]
In addition, Si is inevitably contained because it is used as a deoxidizer. However, as the content is reduced, macrosegregation, particularly reverse V segregation, becomes minor, and the nonuniformity of ductility and notch toughness inside the wall thickness is improved. Moreover, when Si content is high, the temper embrittlement sensitivity becomes very large, and notch toughness is impaired. Therefore, a lower Si content is desirable. However, it is an element used as a deoxidizing agent, and setting its upper limit to be extremely low has a small manufacturing margin and is impractical, so that less than 0.20% is allowed as an impurity.
[0013]
Since the casings and the like targeted in the heat-resistant cast steel of the present invention are about 10 to 150 tons in weight (product weight is 5 to 50 tons), advanced steel making is necessary for producing cast steel with good internal quality. Technology and casting technology are required. The heat-resistant cast steel according to the present invention is obtained by casting an alloy material using a sand mold that melts the alloy material in an electric furnace, thoroughly refines it by out-of-furnace refining, sufficiently degasses, and actively solidifies directionally. Sound cast steel with few casting defects can be manufactured, and a material suitable for the large casing and the like can be obtained.
[0014]
Also, the cast heat-resistant cast steel is annealed at 1000 to 1150 ° C., heated to 1000 to 1200 ° C., subjected to forced cooling, then tempered at 500 to 700 ° C., and then second annealed at 700 to 780 ° C. By performing the tempering step, high creep rupture strength can be secured.
The annealing and normalizing temperatures need to be 1000 ° C. or higher in order to dissolve carbonitride and decompose δ ferrite. However, if the temperature is too high, coarsening of crystal grains and retransformation into δ ferrite will occur. Since this occurs, the upper limit temperature is set to 1150 ° C or 1200 ° C. Further, by tempering twice, the retained austenite can be completely decomposed to obtain a uniform martensite structure, and carbonitride can be finely precipitated to improve the creep rupture strength.
[0015]
In addition, this invention steel can perform welding, such as structural welding and repair welding, as needed, for example, after the above-mentioned series of heat treatments, welding is performed, and then stress-relieving annealing at 650 ° C. to 760 ° C. .
Further, the welding can be performed during the above-described series of steps, that is, after annealing and before normalization, and thereafter normalization, tempering, and second-stage tempering according to the above-described steps. Is done. In this case, the above-described stress relief annealing is not necessary. In this step (including a welding step in the middle of heat treatment), if necessary, further welding can be performed after the second stage of tempering. Perform removal annealing.
As described above, when a welding process is included in the middle of the heat treatment process, the same normalization and tempering as described above are performed for structural welds and repair welds. Breaking strength and good toughness can be secured.
[0016]
【Example】
(Example 1)
Alloys (Examples and Comparative Examples) having the compositions shown in Tables 1 and 2 were melted in a vacuum melting furnace and cast into sand molds as y-
The weldability is evaluated by manufacturing the
As is apparent from Table 3 and FIG. 2, the material of the present invention was found to be excellent in creep rupture strength and weldability.
[0017]
[Table 1]
[0018]
[Table 2]
[0019]
[Table 3]
[0020]
(Example 2)
An alloy raw material that achieves the goal of the heat-resistant cast steel of the present invention is melted in an electric furnace, adjusted in composition by out-of-furnace refining, degassed, and cast in a sand mold, resulting in a cast weight of 20 tons (product weight of about 9 Ton) model casing. This cast steel is held at 1070 ° C. for 20 hours, and then furnace-cooled annealing is performed. After holding at 1070 ° C. for 10 hours, forced cooling is normalized, and then maintained at 570 ° C. for 8 hours as the first stage tempering, followed by air cooling. As the second stage tempering, the furnace was cooled at 740 ° C. for 16 hours and then cooled.
When the mechanical properties of this model casing were evaluated, the creep rupture strength was 12 kgf / mm 2 at 10 5 hours at 600 ° C., 9 kgf / mm 2 at 10 5 hours at 625 ° C., and FATT 60 ° C.
[0021]
【The invention's effect】
As described above, according to the heat-resistant cast steel of the present invention, C: 0.05 to 0.15%, Mn: 0.10 to 1.50%, Ni: 1.0% or less, Cr: 9.0~13.0%, Mo: 0.65 ~1.5% , V: 0.1~0.3%, N: 0.005~0.10%, W: 0.1~5. 0%, Co: 1.5 to 5.0%, B: 0.004 to 0.022%, Nb: 0.01 to 0.2%, Ta: 0.01 to 0 if desired .2%, Ti: contain one or more of 0.1% or less, and the balance consists of Fe and inevitable impurities, so excellent toughness and high temperature strength, especially improved creep rupture strength, and excellent weldability ing. This characteristic enables use in a thermal power plant with higher temperature and pressure and contributes to higher efficiency and higher output in the power plant.
[0022]
Also, when producing the above ingot, the alloy raw material is melted in an electric furnace, refined by out-of-furnace refining, and cast into a sand mold to produce cast steel with few casting defects and good internal quality. Therefore, a material suitable for a large casing or the like can be provided.
[0023]
Moreover, the heat-resistant cast steel cast-molded by the above process is annealed at 1000 to 1150 ° C., heated to 1000 to 1200 ° C., forcibly cooled, then tempered at 500 to 700 ° C., and subsequently 700 to 780 ° C. If the second tempering is performed, a high creep rupture strength can be secured and the toughness can be improved.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a cutting position in a weld evaluation test piece.
FIG. 2 is a graph showing the relationship between B content and weld crack rate.
[Explanation of symbols]
1 Flat plate 2 Weld bead
Claims (2)
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JP10470596A JP3723924B2 (en) | 1995-04-03 | 1996-04-02 | Heat-resistant cast steel and method for producing the same |
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JP9946195 | 1995-04-03 | ||
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JP10470596A JP3723924B2 (en) | 1995-04-03 | 1996-04-02 | Heat-resistant cast steel and method for producing the same |
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JP3723924B2 true JP3723924B2 (en) | 2005-12-07 |
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Cited By (2)
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US9284633B2 (en) | 2010-12-28 | 2016-03-15 | Kabushiki Kaisha Toshiba | Heat resistant cast steel, manufacturing method thereof, cast parts of steam turbine, and manufacturing method of cast parts of steam turbine |
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JPH0959747A (en) * | 1995-08-25 | 1997-03-04 | Hitachi Ltd | High strength heat resistant cast steel, steam turbine casing, steam turbine electric power plant, and steam turbine |
JPH10245658A (en) * | 1997-03-05 | 1998-09-14 | Mitsubishi Heavy Ind Ltd | High cr precision casting material and turbine blade |
JPH1136038A (en) * | 1997-07-16 | 1999-02-09 | Mitsubishi Heavy Ind Ltd | Heat resistant cast steel |
JPH11209851A (en) * | 1998-01-27 | 1999-08-03 | Mitsubishi Heavy Ind Ltd | Gas turbine disk material |
JP4262414B2 (en) * | 2000-12-26 | 2009-05-13 | 株式会社日本製鋼所 | High Cr ferritic heat resistant steel |
FR2823226B1 (en) * | 2001-04-04 | 2004-02-20 | V & M France | STEEL AND STEEL TUBE FOR HIGH TEMPERATURE USE |
JP4542491B2 (en) * | 2005-09-29 | 2010-09-15 | 株式会社日立製作所 | High-strength heat-resistant cast steel, method for producing the same, and uses using the same |
JP4664857B2 (en) * | 2006-04-28 | 2011-04-06 | 株式会社東芝 | Steam turbine |
CN101962739A (en) * | 2010-11-15 | 2011-02-02 | 广东省韶铸集团有限公司 | Cast steel material suitable for high-pressure resistant cylinder body and manufacturing method thereof |
US20130323522A1 (en) * | 2012-06-05 | 2013-12-05 | General Electric Company | Cast superalloy pressure containment vessel |
CN108998638B (en) * | 2018-09-13 | 2019-10-08 | 天津重型装备工程研究有限公司 | A kind of heat treatment method of 620 DEG C or more supercritical turbine casting |
-
1996
- 1996-04-02 JP JP10470596A patent/JP3723924B2/en not_active Expired - Lifetime
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
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US9284633B2 (en) | 2010-12-28 | 2016-03-15 | Kabushiki Kaisha Toshiba | Heat resistant cast steel, manufacturing method thereof, cast parts of steam turbine, and manufacturing method of cast parts of steam turbine |
CN112626413A (en) * | 2020-11-28 | 2021-04-09 | 四川维珍高新材料有限公司 | Aviation case product and production process thereof |
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JPH08333657A (en) | 1996-12-17 |
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