JP3891920B2 - Welding material, welding method using the same, and turbine rotor - Google Patents

Description

【００４５】
本形態においては、図１に示すロータ材Ａに開先部を形成し、上記各溶接材を用いて溶接部Ｃを形成した。前記ロータ材Ａの成分は表１の最下欄に示す通りである。これは従来より公知の低合金鋼ロータ材の一種である。
【００４６】
また、本形態では、前記溶接部Ｃを形成した後、溶接部分に対し５８０℃で１０時間の焼き戻し処理を行った。
【００４７】
上述の如き溶接工程及び焼き戻し工程を経た、各溶接材料毎に形成した試験材である各ロータ材Ａに対して常温引張試験，衝撃試験，応力腐食割れ試験を実施し、表２の結果を得た。なお、同表中の引張り試験のデータは、図１に示す各試験片の両端部に左右方向の引張力をそれぞれ作用させて計測したものであり、また応力腐食割れ試験は、図２に示す装置で前記各試験片であるロータ材Ａの中央部に図中下方から上方に向かう荷重を作用させた状態で特定の地熱蒸気雰囲気に晒し、５０００時間経過後の割れの発生状況を調査したものである。同表中、○印は割れなし、△印は微細な割れの発生、×印は亀裂発生をそれぞれ示している。
【００４８】
【表２】

【００４９】
上記表２を参照すれば、本形態に係るＮｏ，１〜Ｎｏ，５の各溶接材料で上述の如き溶接及び焼き戻し処理を行った場合は、機械的強度，衝撃特性及び応力腐食割れ特性など、Ｎｏ，６〜Ｎｏ，１４の各比較材に比べて優れた特性を示すことがわかる。
【００５０】
＜第２の実施の形態＞
本形態に係る溶接材料の成分は表３に示す通りである。なお、表３中に記した成分の残部は、Ｆｅ及び付随的不純物であり、比較のため前記第１の実施の形態に係る溶接材料の成分も併せて記載している。
【００５１】
本形態においては、Ｎｏ，１５〜Ｎｏ，１９の５種類の溶接材料を形成した。これらの成分構成は、何れも〔請求項４〕で特定した溶接材料の成分範囲に含まれている。すなわち、Ｎｏ，１〜Ｎｏ，５の溶接材料には含まれない、Ｎを含有するものである。このように、Ｎを微量含有させることにより材料強度の向上を図ると同時に、良好な耐食性も確保した。この際、靱性を低下させることがないよう、Ｎの含有量の上限を０．０７％とした。
【００５２】
【表３】

【００５３】
本形態に関しても、図１に示すロータ材Ａに開先部を形成し、上記各溶接材を用いて溶接部Ｃを形成し、同様の条件で常温引張試験，衝撃試験，応力腐食割れ試験を実施した。その結果を表４に示す。
【００５４】
【表４】

【００５５】
上記表４を参照すれば、本形態に係るＮｏ，１５〜Ｎｏ，１９の各溶接材料で上述の如き溶接及び焼き戻し処理を行った場合は、機械的強度，衝撃特性及び応力腐食割れ特性などが、Ｎｏ，６〜Ｎｏ，１４（表２参照。）の各比較材に比べて優れた特性を示すのは勿論、第１の実施の形態に係るＮｏ，１〜Ｎｏ，５の溶接材料を用いた場合よりも機械的強度を高くすることができる。したがって、本形態に係る溶接材料は、高強度を必要とする、例えば蒸気タービンの最終段翼根部の補修などに有用である。
【００５６】
第１の実施の形態に示す各溶接材で溶接部Ｃを形成した各ロータ材Ａについて５６０℃から６４０℃の各温度で１０時間焼もどしを行ったときの溶接部熱影響部の最高硬さ及びロータ材Ａ自体の硬さ測定結果について表５に示す。
【００５７】
【表５】

【００５８】
溶接部熱影響部に極端に硬い部分が存在すると、その部分が応力腐食割れを起こし、再使用中に損傷が発生してしまう。これを防止する観点から考えると、熱影響部の最高硬さはビッカース硬さで３５０以下にすることが望ましい。表５を参照すれば、焼きもどし温度が５６０℃以下であるとビッカース硬さが３５０以上になり、不適切な熱処理となる。一方、焼もどし温度を上げることによってロータ材Ａ（母材）の硬さは低下していく。ロータ材Ａの強度が低下すると蒸気タービンロータとして必要な機械的強度が満足できなくなる。このためには、焼もどし温度を必要以上に高くすることはできない。材料強度としても目安はビッカース硬さで２４０以上を確保することが望ましく、かかる観点からは６２０℃以下の温度での焼き戻しが望ましいことが分かる。
【００５９】
上述の如き結果を踏まえれば、Ｎｏ，１〜Ｎｏ，５又はＮｏ，１５〜Ｎｏ，１９の溶接材を用いて低合金鋼であるロータ材Ａを母材とするタービンロータの肉盛溶接補修を行い、その後焼き戻し温度が５８０°Ｃ乃至６００°Ｃの焼き戻し処理を行えば十分な機械的強度及び耐食性を有するタービンロータとして再生し得る。
【００６０】
＜第３の実施の形態＞
表１の最下欄にその成分を示すロータ材Ａは、上述の如き温度（５８０°Ｃ）の焼き戻し処理でもロータ材Ａの溶接による熱影響部の硬さを緩和して実用に供し得る程度の機械的強度を確保することはできる。ロータ材Ａは比較的Ｎｉの含有量が多いからである。すなわち、Ｎｉの含有量が多ければ多い程、低い温度の焼き戻し処理で前記熱影響部の機械的強度の回復を図ることができる。ただ、この場合でも溶接前の機械的強度を回復する迄には至らない。
【００６１】
一方、Ｎｉの含有量が減少した場合には、前記熱影響部の硬さが増し、上述の如き温度（５８０°Ｃ）の焼き戻し処理では当該熱影響部が溶接処理前の機械的強度を回復するのは当然困難であるとして、実用に供し得る程度の機械的強度を回復することも困難である場合がある。この場合、単純に焼き戻し温度を上げた場合には、今度はこの焼き戻し処理により溶接部Ｃが軟化してその機械的強度を保持することが困難になる。すなわち、タービンロータの熱影響部の機械的強度を回復させるための要件と、溶接部の機械的強度を確保するための要件とは、二律背反する要件となっている。
【００６２】
本形態は表１又は表２に示す成分の溶接材を用いる溶接補修処理において、前記二律背反する要件の調和を図り、例えＮｉの含有量が少ない低合金鋼を母材とするタービンロータであっても、その熱影響部の機械的強度を回復させると同時に、溶接部の機械的強度を十分確保することができる溶接方法を提供するものである。本形態では、ロータ材Ａに較べてＮｉの含有量が少ないロータ材Ｂを考える。このロータ材Ｂは表６に示す成分を含有するものである。
【００６３】
【表６】

【００６４】
本形態に係る溶接方法では、低合金鋼であるロータ材Ｂを母材とするタービンロータの補修部に、まず表１乃至表２に示す成分の各溶接材を用いて一回目の溶接処理により最初の数層（例えば３層乃至４層）の溶接層を形成する。その後、第１及び第２の実施の形態に関連して示す溶接方法における焼き戻し温度（５８０°Ｃ）よりも高温の焼き戻し温度６２０°Ｃ乃至６６０°Ｃで一回目の焼き戻し処理を行う。続いて、同様の溶接材を用いて残りの全層の溶接を前記第一回目の溶接層に重畳して行う。最後に、前記一回目の焼き戻し温度よりも低温の焼き戻し温度である５８０°Ｃ乃至６００°Ｃで二回目の焼き戻し処理を行う。
【００６５】
かかる溶接方法によれば、高温で行う一回目の焼き戻し処理で、一回目の溶接処理による熱影響部を十分軟化させることができ、当該熱影響部に関しては応力腐食割れの発生懸念を除去し得る適切な熱処理とすることができる。
【００６６】
一方、この熱処理により溶接層は軟化するが、これは二回目の溶接処理により焼入れがなされて硬化する。そして、二回目の溶接処理に続く一回目の焼き戻し処理よりも低温で行う二回目の焼き戻し処理により所定の機械的強度を確保することができる。このとき、一回目の溶接処理に伴うロータ材Ｂの熱影響部は、二回目の溶接処理による熱的な影響を受けることはない。溶接時には、溶接部から十分に離れていることから焼きが入って硬くなる等の熱影響はないし、また二回目の焼き戻し時には、一回目の焼き戻し処理の温度よりも温度が低いために二回目の焼き戻しで機械的強度が低下することはないためである。
【００６７】
なお、ここで一回目の焼き戻し処理の温度は補修するタービンロータの材質で異なるが、何れにしても補修するタービンロータの製造時の焼き戻し温度よりも低い温度にする必要かある。例えば、当該焼き戻し温度よりも４０°Ｃ程度低温とする。また、ロータ材Ｂ等の低合金鋼の場合には、６２０°Ｃ乃至６６０°Ｃが適当である。
【００６８】
一方、二回目の焼き戻し温度は、溶接材料により異なる。本形態では、第１及び第２の実施の形態と同様の溶接材料を用いているので、５８０°Ｃ乃至６００°Ｃが適当である。
【００６９】
表７は、表６に示すロータ材（ＣｒＭｏＶ鋼製ロータ材）Ｂについて表５と同様のデータを収集したものである。すなわち、前記Ｎｏ，１〜Ｎｏ，３の各溶接材を用いてロータ材Ｂに関する図１に示す試験材と同様の試験材を形成し、これを５６０°Ｃ乃至６４０°Ｃの各温度で１０時間熱処理した場合の試験結果を示すものである。
【００７０】
【表７】

【００７１】
表７を参照すれば、ロータ材ＢがＮｉの含有量を減じた材質である場合には、熱影響部の最高硬さは６４０℃以上の高温で焼もどしを行わないとビッカース硬さが３５０以下にはならないことが分かる。
【００７２】
また、表８には溶接金属の常温引張試験結果を示すが、焼もどし温度を５８０℃以下にしないと０．２％耐力の仕様である６４０ＭＰａを満足できない。すなわち、単純な焼もどしでは、熱影響部の最高硬さを下げること（応力腐食割れを起こさないため）と溶接金属の材料強度を満足させること（十分な機械的強度を得ること）の２つの仕様を両立させることはできない。
【００７３】
【表８】

【００７４】
そこで、表９に示す溶接及び熱処理を行い、熱影響部最高硬さ及び溶接継手の常温引張試験における０．２％耐力の測定を行った。その結果を同表に併せて示す。
【００７５】
【表９】

【００７６】
表９を参照すれば、本形態に係る溶接方法によって、溶接層の層数が３層乃至４層の場合、熱影響部最高硬さ＜３５０Ｈｖ及び溶接継手の０．２％耐力の仕様を満足することができることが分かる。
【００７７】
＜第４の実施の形態＞
上記第１乃至第３の実施の形態は、タービンロータの肉盛補修に最適な溶接材料及びこれを用いた溶接方法に関するものであるが、従来公知の低合金鋼を母材とするタービンロータの表面に第１乃至第３の実施の形態に記載する溶接材料及び溶接方法により肉盛溶接層をコーティングすることにより新製ロータを形成することもできる。これを第４の実施の形態に係るタービンロータとする。
【００７８】
かかるタービンロータには、第１乃至第３の実施の形態に示す補修ロータと同様の機械的強度及び耐食性を期待し得る。
【００７９】
表１０に示す成分系のロータ材Ｄについて同表に示す溶接材を用いて図３に示す新製ロータを製造した。このときのロータ材Ｄはロータ材Ｂと同様の成分をほぼ同様の割合で含有する従来公知の低合金鋼であり、溶接部Ｆは〔請求項４〕に記載する発明に係る成分を含有する溶接材Ｅで形成したものである。また、製造に当たっては、ロータ材Ｄに第３の実施の形態と同様の溶接方法により溶接部Ｆを形成した。すなわち、小径部が１１００ｍｍφで長さが１０００ｍｍ、また大径部が１７００ｍｍφで長さが１０００ｍｍのロータ材Ｄに、第１の溶接処理で数層の溶接部Ｅを形成し、その後６４０°Ｃで１０時間の第１の焼き戻し処理を行う。続いて、第２の溶接処理で前記溶接部Ｆに重畳して同様の溶接材Ｄを肉盛溶接する。その後、その後５８０°Ｃで１０時間の第２の焼き戻し処理を行い、最後に溶接部Ｆを研削加工してその厚みを１００ｍｍとした。
【００８０】
【表１０】

【００８１】
当該ロータは安価な低合金鋼であるロータ材Ｄの蒸気が触れる裏面のみに１２Ｃｒ鋼を溶接肉盛したロータである。本ロータを切断調査し、各種特性評価試験を実施した結果を表１１に示す。
【００８２】
【表１１】

【００８３】
表１１を参照すれば、機械的強度及びビッカース硬さ、共に良好な値を有していることが分かる。すなわち、機械的強度及び耐食性に優れるロータであることが分かる。このことは、高価な１２Ｃｒロータ材でロータ全体を製造する必要はなく、安価な低合金鋼を母材とする場合であっても適切なコーテッングを施すことによりこれと等価なロータを形成することができる。
【００８４】
【発明の効果】
以上実施の形態とともに具体的に説明した通り、〔請求項１〕に記載する発明は、
重量％で、Ｃ：０．０１〜０．０８％、Ｓｉ：０．０３〜０．３０％、Ｍｎ：０．１〜１．０％、Ｎｉ：４．０〜６．０％、Ｃｒ：１１．５〜１２．５％、Ｍｏ：０．１〜１．２％、Ｖ：０．０１〜０．１０％を含有し、残部がＦｅ及び付随的不純物よりなる溶接材料であるので、
既存のタービンロータに発生した腐食性欠陥を容易に補修し、しかも元々のロータ材よりも優れた耐食性を有するロータに変えることができる。
【００８５】
〔請求項２〕に記載する発明は、
重量％で、Ｃ：０．０３〜０．０６％、Ｓｉ：０．１５〜０．２５％、Ｍｎ：０．３〜０．７％、Ｎｉ：５．０〜５．５％、Ｃｒ：１１．５〜１２．５％、Ｍｏ：０．３〜１．０％、Ｖ：０．０１〜０．１０％を含有し、残部がＦｅ及び付随的不純物よりなる溶接材料であるので、
既存のタービンロータに発生した腐食性欠陥を容易に補修し、しかも元々のロータ材よりも優れた耐食性を有するロータに変えることができるという効果をより顕著に得ることができる。
【００８６】
〔請求項３〕に記載する発明は、
重量％で、Ｃ：０．０４〜０．０５％、Ｓｉ：０．１８〜０．２２％、Ｍｎ：０．３〜０．７％、Ｎｉ：５．０〜５．５％、Ｃｒ：１１．５〜１２．５％、Ｍｏ：０．３〜１．０％、Ｖ：０．０１〜０．１０％を含有し、残部がＦｅ及び付随的不純物よりなる溶接材料であるので、
既存のタービンロータに発生した腐食性欠陥を容易に補修し、しかも元々のロータ材よりも優れた耐食性を有するロータに変えることができるという効果を最も顕著な形で得ることができる。
【００８７】
〔請求項４〕に記載する発明は、
重量％で、Ｃ：０．０１〜０．０８％、Ｓｉ：０．０３〜０．３０％、Ｍｎ：０．１〜１．０％、Ｎｉ：４．０〜６．０％、Ｃｒ：１１．５〜１２．５％、Ｍｏ：０．１〜１．２％、Ｖ：０．０１〜０．１０％、Ｎ：０．００１％〜０．０７０％を含有し、残部がＦｅ及び付随的不純物よりなる溶接材料であるので、
既存のタービンロータに発生した腐食性欠陥を容易に補修し、しかも元々のロータ材よりも優れた耐食性を有するロータに変えることができる。
さらに、Ｎを微量含有するので、耐食性を向上させるべくＣを減じても、Ｃに代わって十分な機械的強度も確保し得る。
【００８８】
〔請求項５〕に記載する発明は、
重量％で、Ｃ：０．０３〜０．０６％、Ｓｉ：０．１５〜０．２５％、Ｍｎ：０．３〜０．７％、Ｎｉ：５．０〜５．５％、Ｃｒ：１１．５〜１２．５％、Ｍｏ：０．３〜１．０％、Ｖ：０．０１〜０．１０％、Ｎ：０．０３５〜０．０７０％を含有し、残部がＦｅ及び付随的不純物よりなる溶接材料であるので、
既存のタービンロータに発生した腐食性欠陥を容易に補修し、しかも元々のロータ材よりも優れた耐食性を有するロータに変えることができる。
さらに、Ｎを微量含有するので、耐食性を向上させるべくＣを減じても、Ｃに代わって十分な機械的強度も確保し得るという効果をより顕著なものとして得ることができる。
【００８９】
〔請求項６〕に記載する発明は、
重量％で、Ｃ：０．０４〜０．０５％、Ｓｉ：０．１８〜０．２２％、Ｍｎ：０．３〜０．７％、Ｎｉ：５．０〜５．５％、Ｃｒ：１１．５〜１２．５％、Ｍｏ：０．３〜１．０％、Ｖ：０．０１〜０．１０％、Ｎ：０．０５〜０．０７％を含有し、残部がＦｅ及び付随的不純物よりなる溶接材料であるので、
既存のタービンロータに発生した腐食性欠陥を容易に補修し、しかも元々のロータ材よりも優れた耐食性を有するロータに変えることができる。
さらに、Ｎを微量含有するので、耐食性を向上させるべくＣを減じても、Ｃに代わって十分な機械的強度も確保し得るという効果を最も顕著なものとして得ることができる。
【００９０】
〔請求項７〕に記載する発明は、
低合金鋼で形成したタービンロータの損傷部分を肉盛溶接により補修する場合の溶接方法において、
〔請求項１〕乃至〔請求項６〕に記載する何れか一つの溶接材料を使用して損傷部分を肉盛溶接で補修する溶接工程と、
その後当該補修部分を所定温度まで加熱する焼き戻し工程とを有する溶接方法であるので、
補修したタービンロータの機械的強度と耐食性とを同時に備えたものとすることができ、その分寿命を延ばすことより当該タービンロータを有する蒸気タービンの稼働効率を向上させることができ、ランニングコストの低減等により良好な経済性を有するタービンを構築するのに資することができる。
【００９１】
〔請求項８〕に記載する発明は、
〔請求項７〕に記載する溶接方法において、
焼き戻し工程における加熱温度を、５８０°Ｃ乃至６００°Ｃとした溶接方法であるので、
溶接部の硬さを好適なものとして〔請求項７〕に記載する発明と同様の効果を奏する。
【００９２】
〔請求項９〕に記載する発明は、
低合金鋼で形成したタービンロータの損傷部分を肉盛溶接により補修する場合の溶接方法において、
〔請求項１〕乃至〔請求項６〕に記載する何れか一つの溶接材料を使用して損傷部分を肉盛溶接で補修する第１の溶接工程と、
その後当該補修部分を所定温度まで加熱する第１の焼き戻し工程と、
前記第１の溶接工程で用いたのと同じ溶接材料を使用し、前記第１の溶接工程で形成した溶接層に重畳してさらに肉盛溶接を行うことにより当該部分の補修を行う第２の溶接工程と、
その後前記第１の焼き戻し工程よりも低温の所定温度まで、前記補修部分を加熱する第２の焼き戻し工程とを含むこ溶接方法であるので、
従来二律背反する要件とされていたロータ母材の硬さを適正にする要件と、溶接部の機械的強度を適正にするための要件との調和をとり、両者を同士に適正なものとして十分な機械的強度を有し、同時に十分な耐食性も有するタービンロータを肉盛り補修により提供することができる。
【００９３】
〔請求項１０〕に記載する発明は、
〔請求項９〕に記載する溶接方法において、
第１の焼き戻し工程における加熱温度を、補修するタービンロータの製造時の焼き戻し温度よりも低い温度にするとともに、
第２の焼き戻し工程における加熱温度を、前記第１の焼き戻し工程よりも低温の５８０°Ｃ乃至６００°Ｃとした溶接方法であるので、
〔請求項９〕に記載する発明の効果を確実に得ることができる。
【００９４】
〔請求項１１〕に記載する発明は、
〔請求項９〕に記載する溶接方法において、
第１の焼き戻し工程における加熱温度を、６２０°Ｃ乃至６６０°Ｃにするとともに、
第２の焼き戻し工程における加熱温度を、５８０°Ｃ乃至６００°Ｃにする溶接方法であるので、
〔請求項９〕に記載する発明の効果を確実に得ることができる。
【００９５】
〔請求項１２〕に記載する発明は、
低合金鋼で形成した母材の表面に、〔請求項７〕に記載する溶接方法により、〔請求項１〕乃至〔請求項６〕に記載する何れか一つの溶接材料を肉盛溶接して形成するコーティング層を設けたタービンロータであるので、
機械的強度に優れ、同時に耐食性にも優れるタービンロータを安価に製造することができる。すなわち、高価な１２Ｃｒロータ材を全体に使用する必要はなく、その結果として極めて廉価な高品質のタービンロータを提供し得る。この結果、当該タービンロータを適用するタービンの稼働率を向上させ、ランニングコストの低減等と相俟って極めて効率の良い地熱プラントを構築し得る。
【００９６】
〔請求項１３〕に記載する発明は、
低合金鋼で形成した母材の表面に、〔請求項８〕に記載する溶接方法により、〔請求項１〕乃至〔請求項６〕に記載する何れか一つの溶接材料を肉盛溶接して形成するコーティング層を設けたタービンロータであるので、
〔請求項１２〕に記載する発明よりもさらに耐食性及び機械的強度に優れるタービンロータとすることができ、〔請求項１２〕に記載する発明と同様の効果をより顕著なものとして得ることができる。
【図面の簡単な説明】
【図１】溶接部の強度及び耐食性を調べるために作製したロータ材を示す説明図である。
【図２】図１に示すロータ材の応力腐食割れを調べるための試験の態様を示す説明図である。
【図３】本発明の実施の形態に係るタービンロータの性能を調べるために作製した試験ロータを概念的に示す説明図である。
【符号の説明】
Ａ、Ｂ、Ｄ ロータ材
Ｃ、Ｆ 溶接部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a welding material, a welding method using the same, and a turbine rotor, and is particularly useful when applied to a turbine rotor used in a geothermal power plant.
[0002]
[Prior art]
As a material for steam turbines used in geothermal power generation, that is, turbine rotors of steam turbines used in an environment containing a large amount of corrosive gas, so-called low alloy steel in which an alloy element is slightly added to iron is widely used. . When a steam turbine made of such low alloy steel is used in a corrosive environment such as in geothermal steam, the turbine rotor will crack due to stress corrosion cracking and corrosion fatigue, making it impossible to continue operation. There is a case.
[0003]
The simplest countermeasure when the operation cannot be continued due to stress corrosion cracking or corrosion fatigue in the turbine rotor is to replace the turbine rotor. However, replacing only the part of the turbine rotor that is damaged results in an economic disadvantage.
[0004]
For this reason, it uses for subsequent use by repairing welding about the generation | occurrence | production part of a crack etc. When performing such welding repair, conventionally, it is dealt with by overlay welding using the same welding material as the base material (low alloy steel) of the turbine rotor.
[0005]
There is Patent Document 1 as a well-known document disclosing alloy steel for turbine rotor having sufficient corrosion resistance in a geothermal steam environment and having necessary strength and toughness. This Patent Document 1 is based on a predetermined amount of Cr in order to ensure corrosion resistance, and lowers C to improve toughness and corrosion resistance, thereby ensuring the reduced hardenability by adding a large amount of Ni and greatly improving toughness. In addition, a rotor material in which Cu is further added to improve strength and corrosion resistance is disclosed.
[0006]
[Patent Document 1]
JP-A-8-3695
[0007]
[Problems to be solved by the invention]
As described above, in the welding repair according to the prior art, the same kind of low alloy steel as the turbine rotor material is used as the repair material, so that cracks will occur again during use after welding repair.
[0008]
On the other hand, by repairing a defective part by welding using martensitic stainless steel (12Cr steel), which has better corrosion resistance than low alloy steel, a turbine rotor having better corrosion resistance than that at the time of manufacturing the turbine rotor is obtained. There is a possibility. However, in this case, if the welding material and the construction method are not appropriate, the corrosion resistance is inferior to that of the low alloy steel. Also, when making the entire rotor with 12Cr steel with excellent corrosion resistance from the beginning, the manufacturing method is limited, and more alloying elements are required, so the construction period is longer than the low alloy steel rotor material, and the cost is also low. There is a problem of soaring.
[0009]
In view of the above prior art, the present invention provides a welding material having sufficient corrosion resistance and low cost even when used in a harsh environment exposed to corrosive gas such as geothermal power generation, a welding method and a turbine using the same. The object is to provide a rotor.
[0010]
[Means for Solving the Problems]
The configuration of the present invention that achieves the above object is characterized by the following points.
[0011]
<Welding material>
1) By weight, C: 0.01 to 0.08%, Si: 0.03 to 0.30%, Mn: 0.1 to 1.0%, Ni: 4.0 to 6.0%, It contains Cr: 11.5 to 12.5%, Mo: 0.1 to 1.2%, V: 0.01 to 0.10%, and the balance is made of Fe and incidental impurities.
[0012]
2) By weight, C: 0.03-0.06%, Si: 0.15-0.25%, Mn: 0.3-0.7%, Ni: 5.0-5.5%, It contains Cr: 11.5 to 12.5%, Mo: 0.3 to 1.0%, V: 0.01 to 0.10%, and the balance is made of Fe and incidental impurities.
[0013]
3) By weight, C: 0.04 to 0.05%, Si: 0.18 to 0.22%, Mn: 0.3 to 0.7%, Ni: 5.0 to 5.5%, It contains Cr: 11.5 to 12.5%, Mo: 0.3 to 1.0%, V: 0.01 to 0.10%, and the balance is made of Fe and incidental impurities.
[0014]
4) By weight, C: 0.01 to 0.08%, Si: 0.03 to 0.30%, Mn: 0.1 to 1.0%, Ni: 4.0 to 6.0%, Cr: 11.5 to 12.5%, Mo: 0.1 to 1.2%, V: 0.01 to 0.10%, N: 0.001% to 0.070%, the balance being Consists of Fe and incidental impurities.
[0015]
5) By weight, C: 0.03-0.06%, Si: 0.15-0.25%, Mn: 0.3-0.7%, Ni: 5.0-5.5%, Cr: 11.5 to 12.5%, Mo: 0.3 to 1.0%, V: 0.01 to 0.10%, N: 0.035 to 0.070%, the balance being Fe And incidental impurities.
[0016]
6) By weight, C: 0.04 to 0.05%, Si: 0.18 to 0.22%, Mn: 0.3 to 0.7%, Ni: 5.0 to 5.5%, Cr: 11.5 to 12.5%, Mo: 0.3 to 1.0%, V: 0.01 to 0.10%, N: 0.05 to 0.07%, the balance being Fe And incidental impurities.
[0017]
The reasons for limiting the components of the welding material described in the above 1) to 6) are as shown in the following a) to h).
[0018]
a) C (carbon): C is one of the most important elements in the welding material according to the present invention, and greatly affects the material strength and corrosion resistance. If it is less than 0.01%, sufficient material strength cannot be obtained. Moreover, when the quantity exceeding 0.08% is added, the quantity of Cr carbide will increase and corrosion resistance will fall.
[0019]
For this reason, 0.01 to 0.08% (see the above 1) and 4). ). In addition, a preferable range is 0.03-0.06% (above 2) See 5). ), Particularly preferred range is from 0.04 to 0.05% (above 3) and 6). ).
[0020]
b) Si (silicon): Si is an element useful as a deoxidizer, but as its amount increases, toughness and ductility decrease. If it is less than 0.03%, sufficient deoxidation cannot be performed. Moreover, when the amount exceeding 0.8% is added, toughness (impact characteristics) deteriorates.
[0021]
For this purpose, see 0.03-0.3% (above 1), 4). ). In addition, a preferable range is 0.15-0.25% (above 2) See 5). ), Particularly preferred range is from 0.18 to 0.22% (above 3), 6). ).
[0022]
c) Mn (manganese): Mn is also an element useful as a deoxidizer. Further, it is combined with the impurity S to prevent embrittlement. If it is less than 0.1%, the effect is not sufficient, and if it is added more than 1%, the toughness decreases due to its presence.
[0023]
For this reason, refer to 0.1 to 1% (above 1) and 4). ). The preferred range is 0.3 to 0.7% (see 2), 3), 5) and 6). ).
[0024]
d) Ni (nickel): Ni is an important element constituting the matrix metal together with Cr and Fe. Ni dissolves in the matrix, thereby making the weld metal structure dense martensite. If it is less than 4%, a stable martensite structure cannot be obtained due to the balance with other elements, and δ-ferrite appears in part, thereby reducing ductility and toughness. Further, even if an amount exceeding 6% is added, the martensite structure becomes unstable and sufficient material strength cannot be obtained. This is due to the partial appearance of the austenite phase.
[0025]
For this purpose, see 4-6% (1) above, 4). ). The preferred range is 5 to 5.5% (see 2), 3), 5) and 6). ).
[0026]
e) Cr (chromium): Cr is an element that forms a matrix together with Ni and Fe. Cr is an element important for corrosion resistance, and if it is less than 11.5%, sufficient corrosion resistance cannot be obtained. If an amount exceeding 12.5% is added, δ-ferrite is generated and ductility and toughness are lowered.
[0027]
For this purpose, see 11.5 to 12.5% (1) to 6) above. ).
[0028]
f) Mo (molybdenum): Mo improves mechanical strength and is also useful for improving corrosion resistance. If it is less than 0.1%, the effect is not sufficient, and if it exceeds 1.2%, ductility and toughness are lowered.
[0029]
For this purpose, see 0.1-1.2% (above 1), 4). ). The preferred range is 0.3 to 1% (see 2), 3), 5) and 6). ).
[0030]
g) V (Vanadium): V constitutes fine carbides and contributes to improvement of mechanical strength. If it is less than 0.01%, the effect is not sufficient, and if it exceeds 0.1%, toughness is reduced.
[0031]
For this purpose, refer to 0.01 to 0.1% (above 1) to 6). ).
[0032]
h) N (nitrogen): N contributes to the improvement of material strength together with C. When it is necessary to increase the material strength, N is added as necessary. Although it is possible to secure strength by adding C instead of adding N, it is actually impossible to obtain a high strength material with C, since adding more C reduces corrosion resistance. . For this reason, N is added when a high-strength material is required.
However, when N is added by 0.07% or more, the toughness is lowered.
[0033]
For this purpose, see 0.001 to 0.0070 (above 4). ). A preferred range is 0.035 to 0.07% (see 5 above). ), Particularly preferred range is from 0.05 to 0.07% (see 6 above). ).
[0034]
<Welding method>
7) In a welding method for repairing a damaged portion of a turbine rotor formed of low alloy steel by overlay welding,
A welding process of repairing a damaged portion by overlay welding using any one of the welding materials described in 1) to 6) above;
And a tempering step for heating the repaired part to a predetermined temperature.
[0035]
8) In the welding method described in 7) above,
The heating temperature in the tempering step was 580 ° C to 600 ° C.
[0036]
9) In a welding method for repairing a damaged portion of a turbine rotor formed of low alloy steel by overlay welding,
A first welding step of repairing a damaged portion by overlay welding using any one of the welding materials described in 1) to 6) above;
A first tempering step after which the repaired portion is heated to a predetermined temperature;
Second repair is performed by using the same welding material as that used in the first welding step and overlaying the weld layer formed in the first welding step and performing overlay welding. Welding process;
And a second tempering step of heating the repaired part to a predetermined temperature lower than that of the first tempering step.
[0037]
10) In the welding method described in 9) above,
The heating temperature in the first tempering step is set to a temperature lower than the tempering temperature at the time of manufacturing the turbine rotor to be repaired,
The heating temperature in the second tempering step is 580 ° C. to 600 ° C., which is lower than that in the first tempering step.
[0038]
11) In the welding method described in 9) above,
The heating temperature in the first tempering step is set to 620 ° C. to 660 ° C.,
The heating temperature in the second tempering step is set to 580 ° C. to 600 ° C.
[0039]
<Turbine rotor>
12) By the welding method described in [Claim 7], any one welding material described in [Claim 1] to [Claim 6] is overlay welded to the surface of the base material formed of low alloy steel. A coating layer to be formed is provided.
[0040]
13) A coating layer formed by overlay welding one of the welding materials described in 1) to 6) on the surface of the base material formed of low alloy steel by the welding method described in 8) above. It was provided.
[0041]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0042]
<First Embodiment>
The components of the welding material and the comparative material according to this embodiment are as shown in Table 1. The balance of the components described in Table 1 is Fe and incidental impurities.
[0043]
In this embodiment, five types of welding materials No, 1 to No, 5 were formed. All of these component configurations are included in the component range of the welding material specified in [Claim 1]. Moreover, nine types of welding materials No, 6 to No, 14 were prepared as comparative materials. In the numerical values shown in Table 1, the underlined values are not included in the numerical range specified in the above [Claim 1].
[0044]
[Table 1]

[0045]
In this embodiment, a groove portion was formed in the rotor material A shown in FIG. 1, and a welded portion C was formed using each of the welding materials. The components of the rotor material A are as shown in the bottom column of Table 1. This is a kind of conventionally known low alloy steel rotor material.
[0046]
Moreover, in this embodiment, after forming the welded portion C, the welded portion was tempered at 580 ° C. for 10 hours.
[0047]
A normal temperature tensile test, an impact test, and a stress corrosion cracking test were performed on each rotor material A, which is a test material formed for each welding material, through the welding process and the tempering process as described above. Obtained. The tensile test data in the table are measured by applying a tensile force in the left-right direction to both ends of each test piece shown in FIG. 1, and the stress corrosion cracking test is shown in FIG. Examine the occurrence of cracks after 5000 hours by exposing to a specific geothermal steam atmosphere with the load applied from the bottom to the top in the figure acting on the central part of the rotor material A, which is each test piece. It is. In the table, ◯ indicates no crack, Δ indicates the occurrence of fine cracks, and X indicates the occurrence of cracks.
[0048]
[Table 2]

[0049]
Referring to Table 2 above, when the welding and tempering treatments described above were performed on the welding materials No, 1 to No, 5 according to this embodiment, mechanical strength, impact characteristics, stress corrosion cracking characteristics, etc. , No, 6 to No, 14, it can be seen that excellent characteristics are shown compared to the comparative materials.
[0050]
<Second Embodiment>
The components of the welding material according to this embodiment are as shown in Table 3. The balance of the components described in Table 3 is Fe and incidental impurities, and the components of the welding material according to the first embodiment are also shown for comparison.
[0051]
In this embodiment, five types of welding materials No, 15 to No, 19 were formed. All of these component configurations are included in the component range of the welding material specified in [Claim 4]. That is, it contains N, which is not included in No, 1 to No, 5 welding materials. In this way, by containing a small amount of N, the material strength was improved, and at the same time, good corrosion resistance was secured. At this time, the upper limit of the N content was set to 0.07% so as not to reduce toughness.
[0052]
[Table 3]

[0053]
Also in this embodiment, a groove portion is formed in the rotor material A shown in FIG. 1, and a weld portion C is formed using each of the above-mentioned welding materials, and a normal temperature tensile test, an impact test, and a stress corrosion cracking test are performed under the same conditions. Carried out. The results are shown in Table 4.
[0054]
[Table 4]

[0055]
Referring to Table 4 above, when the welding and tempering treatments described above were performed on the welding materials No, 15 to No, 19 according to the present embodiment, mechanical strength, impact characteristics, stress corrosion cracking characteristics, etc. However, the welding materials of No, 1 to No, 5 according to the first embodiment are of course shown to be superior to the comparative materials of No, 6 to No, 14 (see Table 2). Mechanical strength can be made higher than when it is used. Therefore, the welding material according to this embodiment is useful for, for example, repairing the last stage blade root of a steam turbine that requires high strength.
[0056]
The maximum hardness of the heat affected zone of the welded part when tempering at 560 ° C. to 640 ° C. for 10 hours with respect to each rotor material A in which the welded part C is formed with each welded material shown in the first embodiment Table 5 shows the measurement results of the hardness of the rotor material A itself.
[0057]
[Table 5]

[0058]
If an extremely hard part exists in the heat affected zone of the welded part, the part causes stress corrosion cracking, and damage occurs during reuse. From the viewpoint of preventing this, it is desirable that the maximum hardness of the heat affected zone is Vickers hardness of 350 or less. Referring to Table 5, when the tempering temperature is 560 ° C. or less, the Vickers hardness is 350 or more, which is an inappropriate heat treatment. On the other hand, increasing the tempering temperature decreases the hardness of the rotor material A (base material). When the strength of the rotor material A is lowered, the mechanical strength necessary for the steam turbine rotor cannot be satisfied. For this purpose, the tempering temperature cannot be increased more than necessary. As a guide, it is desirable that the material strength should be 240 or more in terms of Vickers hardness. From this viewpoint, it is understood that tempering at a temperature of 620 ° C. or less is desirable.
[0059]
Based on the results as described above, overlay welding repair of the turbine rotor using the rotor material A which is a low alloy steel as a base material using the welding materials of No, 1 to No, 5 or No, 15 to No, 19 is performed. If it is performed, and then tempering is performed at a tempering temperature of 580 ° C. to 600 ° C., it can be regenerated as a turbine rotor having sufficient mechanical strength and corrosion resistance.
[0060]
<Third Embodiment>
The rotor material A whose components are shown in the bottom column of Table 1 can be put to practical use by reducing the hardness of the heat-affected zone caused by the welding of the rotor material A even in the tempering treatment at the temperature (580 ° C.) as described above. A degree of mechanical strength can be ensured. This is because the rotor material A has a relatively high Ni content. That is, as the Ni content increases, the mechanical strength of the heat-affected zone can be recovered by tempering at a lower temperature. However, even in this case, the mechanical strength before welding cannot be recovered.
[0061]
On the other hand, when the Ni content decreases, the hardness of the heat-affected zone increases, and in the tempering process at the temperature (580 ° C.) as described above, the heat-affected zone increases the mechanical strength before the welding process. As a matter of course, it is difficult to recover, and it may be difficult to recover a mechanical strength that can be practically used. In this case, when the tempering temperature is simply raised, the tempering process softens the welded portion C and it becomes difficult to maintain the mechanical strength. That is, the requirements for recovering the mechanical strength of the heat-affected zone of the turbine rotor and the requirements for ensuring the mechanical strength of the weld zone are contradictory requirements.
[0062]
This embodiment is a turbine rotor using a low alloy steel with a low Ni content as a base material in order to harmonize the contradictory requirements in the welding repair processing using the welding materials having the components shown in Table 1 or Table 2. However, the present invention also provides a welding method that can restore the mechanical strength of the heat-affected zone and at the same time sufficiently ensure the mechanical strength of the weld zone. In this embodiment, a rotor material B having a lower Ni content than the rotor material A is considered. This rotor material B contains the components shown in Table 6.
[0063]
[Table 6]

[0064]
In the welding method according to the present embodiment, first, a first welding process is performed using each welding material having the components shown in Tables 1 and 2 on the repair portion of the turbine rotor using the rotor material B, which is a low alloy steel, as a base material. First several layers (for example, 3 to 4 layers) of weld layers are formed. Thereafter, the first tempering process is performed at a tempering temperature of 620 ° C. to 660 ° C. higher than the tempering temperature (580 ° C.) in the welding method shown in relation to the first and second embodiments. . Subsequently, welding of all remaining layers is performed using the same welding material so as to be superimposed on the first welding layer. Finally, a second tempering process is performed at 580 ° C. to 600 ° C., which is a lower tempering temperature than the first tempering temperature.
[0065]
According to such a welding method, the heat-affected zone due to the first welding process can be sufficiently softened by the first tempering process performed at a high temperature, and the concern about the occurrence of stress corrosion cracking is eliminated for the heat-affected zone. Appropriate heat treatment can be obtained.
[0066]
On the other hand, the weld layer is softened by this heat treatment, but this is hardened by being quenched by the second welding process. And predetermined mechanical strength is securable by the 2nd tempering process performed at low temperature rather than the 1st tempering process following the 2nd welding process. At this time, the heat-affected zone of the rotor material B that accompanies the first welding process is not affected thermally by the second welding process. At the time of welding, there is no thermal effect such as hardening and hardening because it is sufficiently away from the weld, and at the time of the second tempering, the temperature is lower than the temperature of the first tempering treatment. This is because the mechanical strength is not lowered by the second tempering.
[0067]
Here, the temperature of the first tempering process differs depending on the material of the turbine rotor to be repaired, but in any case, the temperature needs to be lower than the tempering temperature at the time of manufacturing the turbine rotor to be repaired. For example, the temperature is about 40 ° C. lower than the tempering temperature. In the case of a low alloy steel such as the rotor material B, 620 ° C. to 660 ° C. is appropriate.
[0068]
On the other hand, the second tempering temperature varies depending on the welding material. In this embodiment, since the same welding material as in the first and second embodiments is used, 580 ° C. to 600 ° C. is appropriate.
[0069]
Table 7 is a collection of data similar to Table 5 for the rotor material (CrMoV steel rotor material) B shown in Table 6. That is, a test material similar to the test material shown in FIG. 1 relating to the rotor material B is formed by using the welding materials of No, 1 to No, 3, and is formed at each temperature of 560 ° C. to 640 ° C. The test result at the time of heat-processing for a time is shown.
[0070]
[Table 7]

[0071]
Referring to Table 7, when the rotor material B is made of a material with a reduced Ni content, the maximum hardness of the heat-affected zone is 350 Vickers hardness unless tempering is performed at a high temperature of 640 ° C. or higher. It can be seen that this is not the case.
[0072]
Table 8 shows the results of the normal temperature tensile test of the weld metal, but unless the tempering temperature is set to 580 ° C. or lower, 640 MPa which is a 0.2% proof stress specification cannot be satisfied. That is, in simple tempering, the maximum hardness of the heat affected zone is lowered (because stress corrosion cracking does not occur) and the material strength of the weld metal is satisfied (obtaining sufficient mechanical strength). The specifications cannot be made compatible.
[0073]
[Table 8]

[0074]
Therefore, welding and heat treatment shown in Table 9 were performed, and the heat affected zone maximum hardness and 0.2% proof stress in a normal temperature tensile test of the welded joint were measured. The results are also shown in the table.
[0075]
[Table 9]

[0076]
Referring to Table 9, when the number of weld layers is 3 to 4 by the welding method according to the present embodiment, the heat affected zone maximum hardness <350Hv and the 0.2% proof stress specification of the welded joint are satisfied. You can see that you can.
[0077]
<Fourth embodiment>
The first to third embodiments described above relate to a welding material that is optimal for build-up repair of a turbine rotor and a welding method using the same, but a turbine rotor that uses a conventionally known low alloy steel as a base material. A new rotor can also be formed by coating the surface with a build-up weld layer using the welding material and welding method described in the first to third embodiments. This is the turbine rotor according to the fourth embodiment.
[0078]
Such a turbine rotor can be expected to have the same mechanical strength and corrosion resistance as the repair rotor shown in the first to third embodiments.
[0079]
A new rotor shown in FIG. 3 was produced using the welding materials shown in Table 10 for the rotor material D of the component system shown in Table 10. At this time, the rotor material D is a conventionally known low alloy steel containing components similar to those of the rotor material B in substantially the same proportion, and the weld zone F contains the components according to the invention described in [Claim 4]. It is formed of the welding material E. In manufacturing, the welded portion F was formed on the rotor material D by the same welding method as in the third embodiment. That is, several layers of welded portions E are formed by the first welding process on the rotor material D having a small diameter portion of 1100 mmφ and a length of 1000 mm, and a large diameter portion of 1700 mmφ and a length of 1000 mm, and then at 640 ° C. A first tempering process for 10 hours is performed. Subsequently, the same welding material D is superimposed and welded to the welding portion F in the second welding process. Then, the 2nd tempering process for 10 hours was performed at 580 degreeC after that, and the welding part F was finally ground and the thickness was 100 mm.
[0080]
[Table 10]

[0081]
The rotor is a rotor in which 12Cr steel is welded on only the back surface where the steam of the rotor material D, which is an inexpensive low alloy steel, comes into contact. Table 11 shows the results of cutting this rotor and conducting various characteristic evaluation tests.
[0082]
[Table 11]

[0083]
Referring to Table 11, it can be seen that both mechanical strength and Vickers hardness have good values. That is, it can be seen that the rotor is excellent in mechanical strength and corrosion resistance. This means that it is not necessary to manufacture the entire rotor with an expensive 12Cr rotor material, and even if an inexpensive low alloy steel is used as a base material, an equivalent rotor can be formed by applying an appropriate coating. Can do.
[0084]
【The invention's effect】
As specifically described above with the embodiment, the invention described in [Claim 1]
By weight, C: 0.01 to 0.08%, Si: 0.03 to 0.30%, Mn: 0.1 to 1.0%, Ni: 4.0 to 6.0%, Cr: 11.5 to 12.5%, Mo: 0.1 to 1.2%, V: 0.01 to 0.10%, the balance is a welding material consisting of Fe and incidental impurities,
A corrosive defect generated in an existing turbine rotor can be easily repaired, and the rotor can have a corrosion resistance superior to that of the original rotor material.
[0085]
The invention described in [Claim 2]
By weight, C: 0.03-0.06%, Si: 0.15-0.25%, Mn: 0.3-0.7%, Ni: 5.0-5.5%, Cr: Because it is a welding material containing 11.5 to 12.5%, Mo: 0.3 to 1.0%, V: 0.01 to 0.10%, the balance being Fe and incidental impurities,
The effect that the corrosive defect generated in the existing turbine rotor can be easily repaired and can be changed to a rotor having corrosion resistance superior to that of the original rotor material can be obtained more remarkably.
[0086]
The invention described in [Claim 3]
By weight, C: 0.04 to 0.05%, Si: 0.18 to 0.22%, Mn: 0.3 to 0.7%, Ni: 5.0 to 5.5%, Cr: Because it is a welding material containing 11.5 to 12.5%, Mo: 0.3 to 1.0%, V: 0.01 to 0.10%, the balance being Fe and incidental impurities,
The most prominent effect is that the corrosive defects generated in the existing turbine rotor can be easily repaired, and the rotor can be converted to a rotor having better corrosion resistance than the original rotor material.
[0087]
The invention described in [Claim 4]
By weight, C: 0.01 to 0.08%, Si: 0.03 to 0.30%, Mn: 0.1 to 1.0%, Ni: 4.0 to 6.0%, Cr: 11.5 to 12.5%, Mo: 0.1 to 1.2%, V: 0.01 to 0.10%, N: 0.001% to 0.070%, the balance being Fe and Because it is a welding material consisting of incidental impurities,
A corrosive defect generated in an existing turbine rotor can be easily repaired, and the rotor can have a corrosion resistance superior to that of the original rotor material.
Further, since a small amount of N is contained, even if C is reduced to improve corrosion resistance, sufficient mechanical strength can be secured instead of C.
[0088]
The invention described in [Claim 5]
By weight, C: 0.03-0.06%, Si: 0.15-0.25%, Mn: 0.3-0.7%, Ni: 5.0-5.5%, Cr: 11.5 to 12.5%, Mo: 0.3 to 1.0%, V: 0.01 to 0.10%, N: 0.035 to 0.070%, the balance being Fe and accompanying Because it is a welding material consisting of impurities
A corrosive defect generated in an existing turbine rotor can be easily repaired, and the rotor can have a corrosion resistance superior to that of the original rotor material.
Furthermore, since a small amount of N is contained, even if C is reduced to improve the corrosion resistance, the effect that sufficient mechanical strength can be secured in place of C can be obtained as a more remarkable effect.
[0089]
The invention described in [Claim 6]
By weight, C: 0.04 to 0.05%, Si: 0.18 to 0.22%, Mn: 0.3 to 0.7%, Ni: 5.0 to 5.5%, Cr: 11.5 to 12.5%, Mo: 0.3 to 1.0%, V: 0.01 to 0.10%, N: 0.05 to 0.07%, the balance being Fe and accompanying Because it is a welding material consisting of impurities
A corrosive defect generated in an existing turbine rotor can be easily repaired, and the rotor can have a corrosion resistance superior to that of the original rotor material.
Furthermore, since N is contained in a small amount, even if C is reduced to improve corrosion resistance, the effect that sufficient mechanical strength can be secured in place of C can be obtained as the most prominent.
[0090]
The invention described in [Claim 7]
In the welding method when repairing the damaged part of the turbine rotor formed of low alloy steel by overlay welding,
A welding step of repairing a damaged portion by overlay welding using any one of the welding materials described in [Claim 1] to [Claim 6];
Since this is a welding method having a tempering step for heating the repaired part to a predetermined temperature,
The mechanical strength and corrosion resistance of the repaired turbine rotor can be provided at the same time, and the operating efficiency of the steam turbine having the turbine rotor can be improved by extending the life, thereby reducing the running cost. This can contribute to the construction of a turbine having good economic efficiency.
[0091]
The invention described in [Claim 8]
In the welding method according to claim 7,
Since it is a welding method in which the heating temperature in the tempering step is 580 ° C to 600 ° C,
The effect similar to that of the invention described in [Claim 7] is obtained by making the hardness of the welded portion suitable.
[0092]
The invention described in [Claim 9]
In the welding method when repairing the damaged part of the turbine rotor formed of low alloy steel by overlay welding,
[Claim 1] to (Claim 6) using any one welding material described in the first welding step of repairing the damaged portion by overlay welding;
A first tempering step after which the repaired portion is heated to a predetermined temperature;
Second repair is performed by using the same welding material as that used in the first welding step and overlaying the weld layer formed in the first welding step and performing overlay welding. Welding process;
And then a second tempering step for heating the repaired part to a predetermined temperature lower than that of the first tempering step.
Harmonize the requirements for the proper hardness of the rotor base material, which had been considered a contradiction in the past, with the requirements for the appropriate mechanical strength of the welds. A turbine rotor having mechanical strength and at the same time sufficient corrosion resistance can be provided by overlay repair.
[0093]
The invention described in [Claim 10]
In the welding method according to claim 9,
The heating temperature in the first tempering step is set to a temperature lower than the tempering temperature at the time of manufacturing the turbine rotor to be repaired,
Since it is a welding method in which the heating temperature in the second tempering step is 580 ° C to 600 ° C, which is lower than the first tempering step,
The effect of the invention described in claim 9 can be obtained with certainty.
[0094]
The invention described in [Claim 11]
In the welding method according to claim 9,
The heating temperature in the first tempering step is set to 620 ° C. to 660 ° C.,
Since the heating method in the second tempering step is a welding method of 580 ° C to 600 ° C,
The effect of the invention described in claim 9 can be obtained with certainty.
[0095]
The invention described in [Claim 12]
On the surface of a base material formed of low alloy steel, any one of the welding materials described in [Claim 1] to [Claim 6] is overlay welded by the welding method described in [Claim 7]. Since it is a turbine rotor provided with a coating layer to be formed,
A turbine rotor having excellent mechanical strength and at the same time excellent corrosion resistance can be manufactured at low cost. That is, it is not necessary to use expensive 12Cr rotor material as a whole, and as a result, a very inexpensive high-quality turbine rotor can be provided. As a result, it is possible to improve the operating rate of the turbine to which the turbine rotor is applied, and to construct an extremely efficient geothermal plant in combination with reduction of running cost.
[0096]
The invention described in (Claim 13)
The welding material described in [Claim 1] to [Claim 6] is overlay welded to the surface of the base material formed of low alloy steel by the welding method described in [Claim 8]. Since it is a turbine rotor provided with a coating layer to be formed,
It can be set as the turbine rotor which is further excellent in corrosion resistance and mechanical strength than the invention described in [Claim 12], and the effect similar to the invention described in [Claim 12] can be obtained more notably. .
[Brief description of the drawings]
FIG. 1 is an explanatory view showing a rotor material manufactured for examining the strength and corrosion resistance of a welded portion.
FIG. 2 is an explanatory view showing a test mode for examining stress corrosion cracking of the rotor material shown in FIG. 1;
FIG. 3 is an explanatory view conceptually showing a test rotor produced for examining the performance of a turbine rotor according to an embodiment of the present invention.
[Explanation of symbols]
A, B, D Rotor material
C, F weld

Claims (13)

  By weight, C: 0.01 to 0.08%, Si: 0.03 to 0.30%, Mn: 0.1 to 1.0%, Ni: 4.0 to 6.0%, Cr: Welding material comprising 11.5 to 12.5%, Mo: 0.1 to 1.2%, V: 0.01 to 0.10%, the balance being Fe and incidental impurities .   By weight, C: 0.03-0.06%, Si: 0.15-0.25%, Mn: 0.3-0.7%, Ni: 5.0-5.5%, Cr: Welding material comprising 11.5 to 12.5%, Mo: 0.3 to 1.0%, V: 0.01 to 0.10%, the balance being Fe and incidental impurities .   By weight, C: 0.04 to 0.05%, Si: 0.18 to 0.22%, Mn: 0.3 to 0.7%, Ni: 5.0 to 5.5%, Cr: Welding material comprising 11.5 to 12.5%, Mo: 0.3 to 1.0%, V: 0.01 to 0.10%, the balance being Fe and incidental impurities .   By weight, C: 0.01 to 0.08%, Si: 0.03 to 0.30%, Mn: 0.1 to 1.0%, Ni: 4.0 to 6.0%, Cr: 11.5 to 12.5%, Mo: 0.1 to 1.2%, V: 0.01 to 0.10%, N: 0.001% to 0.070%, the balance being Fe and A welding material comprising incidental impurities.   By weight, C: 0.03-0.06%, Si: 0.15-0.25%, Mn: 0.3-0.7%, Ni: 5.0-5.5%, Cr: 11.5 to 12.5%, Mo: 0.3 to 1.0%, V: 0.01 to 0.10%, N: 0.035 to 0.070%, the balance being Fe and accompanying Welding material characterized by comprising impurities.   By weight, C: 0.04 to 0.05%, Si: 0.18 to 0.22%, Mn: 0.3 to 0.7%, Ni: 5.0 to 5.5%, Cr: 11.5 to 12.5%, Mo: 0.3 to 1.0%, V: 0.01 to 0.10%, N: 0.05 to 0.07%, the balance being Fe and accompanying Welding material characterized by comprising impurities. In the welding method when repairing the damaged part of the turbine rotor formed of low alloy steel by overlay welding,
A welding step of repairing a damaged portion by overlay welding using any one of the welding materials described in [Claim 1] to [Claim 6];
And a tempering step of heating the repaired part to a predetermined temperature. In the welding method according to claim 7,
A welding method characterized in that the heating temperature in the tempering step is 580 ° C to 600 ° C. In the welding method when repairing the damaged part of the turbine rotor formed of low alloy steel by overlay welding,
[Claim 1] to (Claim 6) using any one welding material described in the first welding step of repairing the damaged portion by overlay welding;
A first tempering step after which the repaired portion is heated to a predetermined temperature;
Second repair is performed by using the same welding material as that used in the first welding step and overlaying the weld layer formed in the first welding step and performing overlay welding. Welding process;
And a second tempering step of heating the repaired part to a predetermined temperature lower than that of the first tempering step. In the welding method according to claim 9,
The heating temperature in the first tempering step is set to a temperature lower than the tempering temperature at the time of manufacturing the turbine rotor to be repaired,
The welding method characterized in that the heating temperature in the second tempering step is 580 ° C to 600 ° C, which is lower than the first tempering step. In the welding method according to claim 9,
The heating temperature in the first tempering step is set to 620 ° C. to 660 ° C.,
A welding method, wherein the heating temperature in the second tempering step is 580 ° C to 600 ° C.   On the surface of the base material formed of low alloy steel, any one of the welding materials described in [Claim 1] to [Claim 6] is overlay welded by the welding method described in [Claim 7]. A turbine rotor provided with a coating layer to be formed.   On the surface of the base material formed of low alloy steel, any one of the welding materials described in [Claim 1] to [Claim 6] is overlay welded by the welding method described in [Claim 8]. A turbine rotor provided with a coating layer to be formed.

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