JP2004285393A - Heat resistant material - Google Patents
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- JP2004285393A JP2004285393A JP2003077922A JP2003077922A JP2004285393A JP 2004285393 A JP2004285393 A JP 2004285393A JP 2003077922 A JP2003077922 A JP 2003077922A JP 2003077922 A JP2003077922 A JP 2003077922A JP 2004285393 A JP2004285393 A JP 2004285393A
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Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は、自動車の排気系部材や加熱炉、ボイラー、タービン、熱交換器、原子力設備、化学工業装置、燃料電池などの各種耐熱部品に用いて好適な耐酸化性に優れた耐熱材料に関するものである。
【０００２】
【従来の技術】
従来、自動車排気系部材や加熱炉用部材、熱交換器用部材のような耐熱部品には、ＪＩＳのＳＵＳ３１０Ｓ、ＳＵＳ３２１Ｈ、ＳＵＳ３４７Ｈなどのオーステナイト系ステンレス鋼や、ＳＵＨ４０９、ＳＵＳ４４４等の高Ｃｒフェライト鋼やフェライト系ステンレス鋼が用いられてきた。しかし、これらの鋼はいずれも、耐酸化性が不十分であり、要求特性に十分に応えられていない。また、特許文献１には、加熱と冷却を繰り返す各種耐熱部品に適した耐酸化性に優れた耐熱合金として、Ｃｕ，Ｔｉ等を含むＦｅ−Ｎｉ−Ｃｒ合金が開示されているが、Ｎｉを２０〜３５ｗｔ％と多量に含むために、コストが高いという問題がある。そのため、Ｎｉを多量に添加しない耐熱材料の開発が望まれている。
【０００３】
【特許文献１】特開２０００−１９２２０５号公報
【０００４】
【発明が解決しようとする課題】
さて、高温において使用される材料は、耐酸化性を保つために保護性酸化皮膜の生成が不可欠である。中でもＡｌ系酸化物による保護性皮膜は、耐酸化性が非常に高い。しかし、一般に、Ａｌ系酸化物が連続的な保護性皮膜を形成するためには３％以上のＡｌの添加が必要であり、製造性を著しく悪化させたり、コストアップの原因となったりする。
【０００５】
そこで、本発明の目的は、Ｎｉを含まず、かつ低Ａｌの成分組成を有し、製造性が良好で、高温において高強度かつ耐酸化性に優れる耐熱材料を提供することにある。
【０００６】
【課題を解決するための手段】
発明者らは、上述した課題を解決するために耐酸化性に及ぼす添加元素の影響に着目し鋭意検討した。その結果、ＭｏとＮｂを複合添加した場合には、高温・長時間の使用環境下において、多量の金属間化合物が母材の結晶粒界に析出し、これらの析出物がＣｒ，Ｆｅ，Ｓｉ等の元素の拡散を抑制する結果、耐酸化性が著しく向上することを見出した。もちろん、ＭｏまたはＮｂの単独添加によっても金属間化合物は析出するが、耐酸化性向上効果は得られない。つまり、複合添加した場合にのみ、耐酸化性を著しく向上させることができる。さらに、この作用によって、Ａｌ含有量が３．０ｍａｓｓ％と低い場合でも、鋼板表面にＡｌ系酸化物の保護皮膜が生成しやすくなり、さらに耐酸化性が向上することを見出した。さらに、Ｍｏ−Ｎｂ添加鋼特有の、高温時における酸化物の剥離量が増大するという問題も、Ｓｃ，Ｙ，Ｌａ，Ｃｅ，Ｐｒ，Ｎｄ，Ｐｍ，Ｓｍ，Ｚｒ，Ｈｆの添加によって防止できることを見出した。
【０００７】
上記知見に基づき開発された本発明は、Ｃ：０．２０ｍａｓｓ％以下、Ｓｉ：０．０２〜１．０ｍａｓｓ％、Ｍｎ：２．０ｍａｓｓ％以下、Ｃｒ：１０〜４０ｍａｓｓ％、Ａｌ：０．０１〜３．０ｍａｓｓ％、Ｍｏ：０．０３〜５．０ｍａｓｓ％およびＮｂ：０．１〜３．０ｍａｓｓ％を含み、かつＭｏとＮｂとは、
０．１≦Ｍｏ／Ｎｂ≦３０
の関係を満たして含み、さらにＣｒとＡｌとは、
１５≦Ｃｒ＋１０Ａｌ≦５０
の関係を満たして含み、残部がＦｅおよび不可避的不純物からなることを特徴とする耐熱材料である。
【０００８】
また、本発明は、Ｃ：０．２０ｍａｓｓ％以下、Ｓｉ：０．０２〜１．０ｍａｓｓ％、Ｍｎ：２．０ｍａｓｓ％以下、Ｃｒ：１０〜４０ｍａｓｓ％、Ａｌ：０．０１〜３．０ｍａｓｓ％、Ｍｏ：０．０３〜５．０ｍａｓｓ％およびＮｂ：０．１〜３．０ｍａｓｓ％を含み、かつＭｏとＮｂとは、
０．１≦Ｍｏ／Ｎｂ≦３０
の関係を満たして含み、さらにＣｒとＡｌとは、
１５≦Ｃｒ＋１０Ａｌ≦５０
の関係を満たして含み、残部がＦｅおよび不可避的不純物からなり、母材の結晶粒界にはＭｏおよびＮｂを含む金属間化合物が析出し、表面にはＡｌ２Ｏ３系の酸化物層が形成されてなることを特徴とする耐熱材料である。
【０００９】
さらに、本発明は、Ｃ：０．２０ｍａｓｓ％以下、Ｓｉ：０．０２〜１．０ｍａｓｓ％、Ｍｎ：２．０ｍａｓｓ％以下、Ｃｒ：１０〜４０ｍａｓｓ％、Ａｌ：０．０１〜３．０ｍａｓｓ％、Ｍｏ：０．０３〜５．０ｍａｓｓ％およびＮｂ：０．１〜３．０ｍａｓｓ％を含み、かつＭｏとＮｂとは、
０．１≦Ｍｏ／Ｎｂ≦３０
の関係を満たして含み、さらにＣｒとＡｌとは、
１５≦Ｃｒ＋１０Ａｌ≦５０
の関係を満たして含み、残部がＦｅおよび不可避的不純物からなり、露点３０℃の大気中における８００℃で１０００時間の酸化増量が２．０ｇ／ｍ２以下であることを特徴とする耐熱材料である。
【００１０】
なお、本発明の材料は、上記成分組成に加えてさらに、Ｓｃ，Ｙ，Ｌａ，Ｃｅ，Ｐｒ，Ｎｄ，Ｐｍ，Ｓｍ，ＺｒおよびＨｆの中から選ばれる１種または２種以上を合計で１．０ｍａｓｓ％以下含有したものであることが好ましい。
【００１１】
さらに、本発明の材料は、上記母材の結晶粒界に析出したＭｏおよびＮｂを含む金属間化合物の最近接距離の平均が２０μｍ以下であることが好ましい。
【００１２】
【発明の実施の形態】
まず、本発明の耐熱材料が耐熱性を発揮する理由について説明する。
本発明の特徴は、ＭｏとＮｂを複合添加することにより、高温・長時間の使用環境下において、多量の金属間化合物が母材の結晶粒界に析出し、これらの析出物がＣｒ，Ｆｅ，Ｓｉ等の元素の拡散を抑制する結果、鋼板表面にはＣｒ２Ｏ３等を含む主としてＡｌ２Ｏ３からなる酸化皮膜が形成され、その結果、耐酸化性が著しく向上することにある。ここで、上記金属間化合物とは、Ｆｅ−Ｃｒ−Ｓｉ−Ｍｏ−Ｎｂ系の複合金属間化合物のことであり、Ｃｒ，Ｆｅ，Ｓｉ等の元素の拡散を抑制するが、Ａｌの拡散にはさほど影響しない。その結果、Ａｌを３．０ｍａｓｓ％より多く含有していなくとも、高温酸化雰囲気中で鋼板表面にＡｌの拡散のみが進行し、ひいては鋼板表面に耐酸化性に優れたＡｌ２Ｏ３系の酸化皮膜を形成させることができるのである。
【００１３】
なお、Ｆｅ−Ｃｒ−Ｓｉ−Ｍｏ−Ｎｂ系の金属間化合物が上記拡散を抑制する作用を発揮するためには、結晶粒界に密に析出することが必要であり、走査型電子顕微鏡で観察したときに検出される大きさ２００ｎｍ以上の金属間化合物が、相互の最近接距離が２０μｍ以下で析出していることが好ましい。これ以上の間隔では、十分か拡散抑制効果が得られない。なお、この金属間化合物は、本発明鋼板を使用する段階から析出させておくか、あるいは、高温での使用中に結晶粒界に析出させ、鋼板表面に耐酸化性に優れた、主としてＡｌ２Ｏ３からなる酸化皮膜を形成させてもよい。
【００１４】
次に、本発明に係る耐熱材料の成分組成について説明する。
Ｃ：０．２０ｍａｓｓ％以下
Ｃは、炭化物を形成して高温強度を高める作用を有するが、加工性を劣化させ、また、Ｃｒと結合することにより耐酸化性に有効なＣｒ量を減少させるため、０．２０ｍａｓｓ％以下に制限する。より好適には０．１０ｍａｓｓ％以下である。
【００１５】
Ｓｉ：０．０２〜１．０ｍａｓｓ％
Ｓｉは、金属間化合物の析出を促進する作用を有する。しかし、過度の添加は加工性の劣化を招くので、０．０２〜１．０ｍａｓｓ％に限定する。好ましくは０．０５〜１．０ｍａｓｓ％である。
【００１６】
Ｍｎ：２．０ｍａｓｓ％以下
Ｍｎは、酸化皮膜の密着性を向上させるのに必要である。しかし、過度に添加すると、酸化速度の増大を招くため、２．０ｍａｓｓ％以下に限定する。好ましくは、１．５ｍａｓｓ％以下である。
【００１７】
Ｃｒ：１０〜４０ｍａｓｓ％
Ｃｒは、Ｃｒ２Ｏ３皮膜の生成により、耐酸化性を維持するために重要な元素であり、１０ｍａｓｓ％未満では耐酸化性向上効果が得られず、一方、４０ｍａｓｓ％を超えると加工性の劣化を招くので、１０〜４０ｍａｓｓ％に限定する。より好適には１０〜３０ｍａｓｓ％である。
【００１８】
Ａｌ：０．０１〜３．０ｍａｓｓ％でかつ、１５≦Ｃｒ＋１０Ａｌ≦５０
Ａｌは、Ｃｒと同様、耐酸化性を維持するために重要な元素である。しかし、過度の添加は製造性が悪くなりコストの増大を招くので３．０ｍａｓｓ％以下に限定する。より好適には０．０５〜２．０ｍａｓｓ％である。ここでＣｒ＋１０Ａｌの値を１５〜５０の範囲に限定する理由は、まず、ＣｒとＡｌはともに、保護性の酸化皮膜を形成する元素であるため、ＣｒとＡｌはその合計量（Ｃｒ＋１０Ａｌ）で規制する必要があり、このＣｒ＋１０Ａｌの値が１５未満では耐酸化性が不十分であり、一方、その値が５０超えの場合には製造性が著しく悪化するためである。
【００１９】
Ｍｏ：０．０３〜５．０ｍａｓｓ％、Ｎｂ：０．１〜３．０ｍａｓｓ％でかつ０．１≦Ｍｏ／Ｎｂ≦３０
本発明の耐熱材料は、Ｆｅ−Ｃｒ系の合金を基本とし、この成分組成にさらに、ＭｏとＮｂを複合添加することにより、高温・長時間の使用環境において、多量の金属間化合物を母材の粒界に析出させて、Ｃｒ，Ｆｅ，Ｓｉ等の元素の拡散機構を制御し、耐酸化性の向上を図っている。さらに、これらの元素は高温強度を高める作用も有する。しかし、ＭｏおよびＮｂの過剰な添加は加工性を劣化させるため、Ｍｏ：０．０３〜５．０ｍａｓｓ％、Ｎｂ：０．１〜３．０ｍａｓｓ％の範囲に限定する。より好適には、Ｍｏ：０．１〜３．０ｍａｓｓ％、Ｎｂ：０．１〜２．０ｍａｓｓ％である。ここでＭｏとＮｂの比であるＭｏ／Ｎｂの値を０．１〜３０の範囲に限定する理由は、Ｍｏ／Ｎｂは、Ｆｅ−Ｃｒ−Ｓｉ−Ｍｏ−Ｎｂ系の金属間化合物の生成量を表す指標であり、０．１未満の場合、あるいは３０超えの場合には、ＮｂあるいはＭｏの単独添加と同様になり、耐酸化性の向上に有効な金属間化合物の生成量が少なくなるためである。好ましくは０．５≦Ｍｏ／Ｎｂ≦３０である。
【００２０】
Ｓｃ，Ｙ，Ｌａ，Ｃｅ，Ｐｒ，Ｎｄ，Ｐｍ，Ｓｍ，Ｚｒ，Ｈｆ：合計で１．０ｍａｓｓ％以下
Ｓｃ，Ｙ，Ｌａ，Ｃｅ，Ｐｒ，Ｎｄ，Ｐｍ，Ｓｍ，ＺｒおよびＨｆは、少量の添加で酸化皮膜の密着性を向上させることによって耐酸化性を改善する効果を有する。しかし、過度の添加は熱間加工性を劣化させるので、１．０ｍａｓｓ％以下に限定する。より好ましくは、０．００５〜０．５ｍａｓｓ％である。
【００２１】
なお、本発明においては、上記の必須成分のほかに、必要に応じて下記の元素を含有してもよい。
Ｐ：０．０５ｍａｓｓ％以下、Ｓ：０．０５ｍａｓｓ％以下、Ｎ：０．５ｍａｓｓ％以下、Ｃｕ：０．２０ｍａｓｓ％以下、Ｎｉ：１．０ｍａｓｓ％以下、Ｖ：１．０ｍａｓｓ％以下、Ｗ：３．０ｍａｓｓ％以下、Ｔａ：２．０ｍａｓｓ％以下、Ｔｉ：０．５ｍａｓｓ％以下、Ｍｇ：０．０５ｍａｓｓ％以下、Ｃａ：０．０５ｍａｓｓ％以下、Ｃｏ：５．０ｍａｓｓ％以下
【００２２】
次に、本発明の金属材料の製造方法について、簡単に説明する。
本発明に係る金属材料の溶製方法は、通常公知の方法がすべて適用できるので、特に限定する必要はないが、例えば、製鋼工程は、転炉、電気炉等で溶製し、強攪拌・真空酸素脱炭処理（ＳＳ−ＶＯＤ）により２次精錬を行うのが好適である。鋳造方法は、生産性、品質の面から連続鋳造が好ましい。鋳造により得られたスラブは、必要により再加熱し、熱間圧延し、７００〜１２００℃で熱延板焼鈍したのち酸洗する。上記熱延板をさらに冷間圧延し、あるいはさらに７００〜１２００℃の焼鈍・酸洗処理を施しても構わない。
【００２３】
【実施例】
表１に示す成分組成を有する種々の鋼を、転炉−２次精錬により溶製し、連続鋳造により２００ｍｍ厚のスラブとした。これらのスラブを１１００〜１３００℃に加熱したのち、熱間圧延して板厚５ｍｍの熱延板とし、７００〜１２００℃の熱延板焼鈍と酸洗処理を施した。次いで、冷間圧延により板厚１ｍｍの冷延板とし、７００〜１２００℃の焼鈍を行った。この冷延焼鈍板から、１ｍｍ×３０ｍｍ×３０ｍｍのサンプルを切り出し、下記の耐酸化性試験に供した。
【００２４】
・酸化増量測定：上記試験片を、８００℃に加熱された露点３０℃の大気雰囲気の炉中に１０００時間、加熱保持する酸化試験を行い、試験前後の試験片の重量差から酸化増量を測定した。
・耐剥離性評価：ナイロンブラシを用いて上記酸化焼鈍後の試料表面を擦り、剥離が全く無い場合を○、少しでも剥離がある場合を×と評価した。
・金属間化合物の平均間隔測定：酸化試験後の試料断面（３０μｍ×５０μｍ）を走査型電子顕微鏡等で撮影し、大きさ２００ｎｍ以上の金属間化合物が有する最近接金属間化合物との距離を測定し、その平均値を求めた。
【００２５】
上記試験の結果を表２に示した。表２から明らかなように、Ｆｅ−Ｃｒ合金に、Ｍｏ，Ｎｂ，Ａｌを複合添加した本発明の条件を満たすＮｏ．１からＮｏ．１８の材料は、いずれも酸化増量が少なく、耐酸化性向上の効果が顕著に現れている。また、耐酸化性の優れたＮｏ．１からＮｏ．１８の材料はいずれも、析出した金属間化合物の平均間隔が２０μｍ以下となっている。
【００２６】
これに対して、Ｎｏ．１９の材料は、Ｃ量が高いために、ＣがＣｒと結びついて有効Ｃｒ量が減少し、耐酸化性が低下している。また、Ｎｏ．２２の材料は、Ｃｒが少ないために、酸化皮膜の保護性が乏しく、耐酸化性が低下している。同様に、Ｎｏ．２３の材料は、Ａｌが少ないために、耐酸化性が低下している。さらに、１５≦Ｃｒ＋１０Ａｌ≦５０の条件を満たさない場合（Ｎｏ．２４）は、酸化皮膜の保護性が乏しく、耐酸化性が低下している。
【００２７】
Ｍｎは、酸化物の剥離を抑制するが、Ｃｒ２Ｏ３皮膜中の拡散速度が速いために、表層に酸化物を生成する。そのため、Ｎｏ．２１の材料のようにＭｎ量が多いと、酸化速度の増大を招く。また、Ｎｏ．２５の材料のようにＭｏ量が少ないと金属間化合物の析出量が少なく、耐酸化性向上の効果が小さい。また、Ｎｏ．２６の材料のようにＮｂ量が少ないと金属間化合物の析出量が少なく、耐酸化性向上の効果が小さい。また、０．１≦Ｍｏ／Ｎｂ≦３０の条件を満たさない場合（Ｎｏ．２７，Ｎｏ．２８）も、金属間化合物の析出量が少なく、耐酸化性向上の効果が小さい。また、Ｓｉ量の低いＮｏ．２０の材料は、金属間化合物の析出が促進されず、耐酸化性が低下している。
【００２８】
【表１】
【表２】
【発明の効果】
以上説明したように、本発明によれば、Ｆｅ−Ｃｒ合金に、Ｍｏ，Ｎｂ，Ａｌを適正範囲で複合添加することにより、耐酸化性に優れた耐熱材料を得ることができる。さらにこの材料に、Ｓｃ，Ｙ，Ｌａ，Ｃｅ，Ｐｒ，Ｎｄ，Ｐｍ，Ｓｍ，ＺｒおよびＨｆの中から選ばれる１種または２種以上を添加することにより、高温で形成される酸化皮膜の耐剥離性をより向上することができる。そして、本発明の耐熱材料を用いることにより、高温・長時間の使用による材料劣化を抑制できるので、材料費の低減に大きく寄与する。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a heat-resistant material having excellent oxidation resistance suitable for use in various heat-resistant parts such as exhaust system members of automobiles, heating furnaces, boilers, turbines, heat exchangers, nuclear facilities, chemical industry equipment, and fuel cells. It is.
[0002]
[Prior art]
Conventionally, heat-resistant parts such as automobile exhaust system members, heating furnace members, and heat exchanger members include austenitic stainless steels such as JIS SUS310S, SUS321H, and SUS347H, and high Cr ferrite steels and ferrites such as SUH409 and SUS444. Series stainless steels have been used. However, all of these steels have insufficient oxidation resistance and do not sufficiently meet required characteristics. Patent Literature 1 discloses an Fe—Ni—Cr alloy containing Cu, Ti, or the like as a heat-resistant alloy having excellent oxidation resistance suitable for various heat-resistant parts that repeat heating and cooling. Since it is contained in a large amount of 20 to 35 wt%, there is a problem that the cost is high. Therefore, development of a heat-resistant material in which a large amount of Ni is not added is desired.
[0003]
[Patent Document 1] Japanese Patent Application Laid-Open No. 2000-192205
[Problems to be solved by the invention]
Now, for a material used at a high temperature, formation of a protective oxide film is indispensable to maintain oxidation resistance. Above all, a protective film made of an Al-based oxide has extremely high oxidation resistance. However, in general, it is necessary to add 3% or more of Al in order for the Al-based oxide to form a continuous protective film, which significantly deteriorates manufacturability and causes an increase in cost.
[0005]
Accordingly, an object of the present invention is to provide a heat-resistant material that does not contain Ni, has a low Al composition, has good manufacturability, has high strength at high temperatures, and has excellent oxidation resistance.
[0006]
[Means for Solving the Problems]
In order to solve the above-described problems, the inventors have focused on the effects of the added elements on the oxidation resistance and made intensive studies. As a result, when Mo and Nb are added in combination, a large amount of intermetallic compound precipitates at the crystal grain boundary of the base material under a high-temperature and long-time use environment, and these precipitates form Cr, Fe, Si. It has been found that as a result of suppressing the diffusion of elements such as, oxidation resistance is significantly improved. Of course, the intermetallic compound is precipitated even when Mo or Nb is added alone, but the effect of improving oxidation resistance cannot be obtained. That is, the oxidation resistance can be remarkably improved only when the composite is added. Furthermore, it has been found that, even when the Al content is as low as 3.0 mass%, a protective film of an Al-based oxide is easily formed on the steel sheet surface by this action, and the oxidation resistance is further improved. Furthermore, the problem of an increase in the amount of oxide peeling at a high temperature, which is specific to Mo-Nb-added steel, can be prevented by adding Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Zr, and Hf. I found it.
[0007]
The present invention developed on the basis of the above-mentioned findings is as follows: C: 0.20 mass% or less, Si: 0.02 to 1.0 mass%, Mn: 2.0 mass% or less, Cr: 10 to 40 mass%, Al: 0.01 To 3.0 mass%, Mo: 0.03 to 5.0 mass% and Nb: 0.1 to 3.0 mass%, and Mo and Nb are:
0.1 ≦ Mo / Nb ≦ 30
And further includes Cr and Al:
15 ≦ Cr + 10Al ≦ 50
Is a heat-resistant material that satisfies the following relationship, with the balance being Fe and unavoidable impurities.
[0008]
In the present invention, C: 0.20 mass% or less, Si: 0.02 to 1.0 mass%, Mn: 2.0 mass% or less, Cr: 10 to 40 mass%, Al: 0.01 to 3.0 mass%. , Mo: 0.03-5.0 mass% and Nb: 0.1-3.0 mass%, and Mo and Nb are:
0.1 ≦ Mo / Nb ≦ 30
And further includes Cr and Al:
15 ≦ Cr + 10Al ≦ 50
And the balance consists of Fe and unavoidable impurities, intermetallic compounds containing Mo and Nb are precipitated at the crystal grain boundaries of the base material, and an Al 2 O 3 -based oxide layer is formed on the surface. It is a heat-resistant material characterized by being formed.
[0009]
Furthermore, in the present invention, C: 0.20 mass% or less, Si: 0.02 to 1.0 mass%, Mn: 2.0 mass% or less, Cr: 10 to 40 mass%, Al: 0.01 to 3.0 mass%. , Mo: 0.03-5.0 mass% and Nb: 0.1-3.0 mass%, and Mo and Nb are:
0.1 ≦ Mo / Nb ≦ 30
And further includes Cr and Al:
15 ≦ Cr + 10Al ≦ 50
And a balance consisting of Fe and unavoidable impurities, and having an oxidation weight increase of not more than 2.0 g / m 2 at 800 ° C. for 1000 hours in the air having a dew point of 30 ° C. is there.
[0010]
In addition, the material of the present invention further comprises one or more selected from Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Zr and Hf in addition to the above-mentioned composition. It is preferable that the content is 0.0 mass% or less.
[0011]
Further, in the material of the present invention, the average of the closest distances of the intermetallic compounds containing Mo and Nb precipitated at the crystal grain boundaries of the base material is preferably 20 μm or less.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
First, the reason why the heat-resistant material of the present invention exhibits heat resistance will be described.
The feature of the present invention is that by adding Mo and Nb in a complex manner, a large amount of intermetallic compound precipitates at the crystal grain boundary of the base material under a high-temperature and long-time use environment, and these precipitates form Cr, Fe. As a result of suppressing the diffusion of elements such as Si and Si, an oxide film mainly composed of Al 2 O 3 containing Cr 2 O 3 and the like is formed on the surface of the steel sheet, and as a result, the oxidation resistance is significantly improved. Here, the above-mentioned intermetallic compound is a complex intermetallic compound of the Fe—Cr—Si—Mo—Nb system, which suppresses the diffusion of elements such as Cr, Fe, and Si, but the diffusion of Al Does not affect much. As a result, even if Al does not contain more than 3.0 mass%, only diffusion of Al proceeds on the surface of the steel sheet in a high-temperature oxidizing atmosphere, and thus the oxidation of Al 2 O 3 based on the steel sheet surface having excellent oxidation resistance. A film can be formed.
[0013]
In addition, in order for the Fe-Cr-Si-Mo-Nb-based intermetallic compound to exhibit the effect of suppressing the above-mentioned diffusion, it is necessary that the intermetallic compound is densely precipitated at the crystal grain boundaries, and observed with a scanning electron microscope. It is preferable that intermetallic compounds having a size of 200 nm or more, which are detected at the time of precipitation, are precipitated at a closest distance of 20 μm or less. If the interval is longer than this, a sufficient or sufficient diffusion suppressing effect cannot be obtained. The intermetallic compound may be precipitated from the stage of using the steel sheet of the present invention, or may be precipitated at crystal grain boundaries during use at a high temperature, and the surface of the steel sheet may be mainly made of Al 2 O 3 having excellent oxidation resistance. An oxide film made of O 3 may be formed.
[0014]
Next, the component composition of the heat-resistant material according to the present invention will be described.
C: 0.20 mass% or less C has the effect of forming carbides and increasing the high-temperature strength, but causes deterioration of workability and also reduces the amount of Cr effective for oxidation resistance by bonding with Cr. , 0.20 mass% or less. More preferably, it is 0.10 mass% or less.
[0015]
Si: 0.02 to 1.0 mass%
Si has an effect of promoting the precipitation of an intermetallic compound. However, since excessive addition causes deterioration of workability, it is limited to 0.02 to 1.0 mass%. Preferably, it is 0.05 to 1.0 mass%.
[0016]
Mn: 2.0 mass% or less Mn is necessary for improving the adhesion of the oxide film. However, if added excessively, the oxidation rate will increase, so the content is limited to 2.0 mass% or less. Preferably, it is 1.5 mass% or less.
[0017]
Cr: 10 to 40 mass%
Cr is an important element for maintaining the oxidation resistance by forming a Cr 2 O 3 film. If less than 10 mass%, the effect of improving the oxidation resistance cannot be obtained. On the other hand, if it exceeds 40 mass%, the workability is increased. Since deterioration is caused, the content is limited to 10 to 40 mass%. More preferably, it is 10 to 30 mass%.
[0018]
Al: 0.01 to 3.0 mass% and 15 ≦ Cr + 10Al ≦ 50
Al, like Cr, is an important element for maintaining oxidation resistance. However, excessive addition deteriorates manufacturability and leads to an increase in cost. More preferably, it is 0.05 to 2.0 mass%. Here, the reason for limiting the value of Cr + 10Al to the range of 15 to 50 is that Cr and Al are regulated by the total amount (Cr + 10Al) because both Cr and Al are elements forming a protective oxide film. When the value of Cr + 10Al is less than 15, the oxidation resistance is insufficient. On the other hand, when the value exceeds 50, the productivity is significantly deteriorated.
[0019]
Mo: 0.03 to 5.0 mass%, Nb: 0.1 to 3.0 mass%, and 0.1 ≦ Mo / Nb ≦ 30.
The heat-resistant material of the present invention is based on an Fe-Cr-based alloy, and by adding Mo and Nb in combination with this component composition, a large amount of an intermetallic compound can be used in a high-temperature and long-time use environment. To control the diffusion mechanism of elements such as Cr, Fe, and Si, thereby improving oxidation resistance. Further, these elements also have an effect of increasing high-temperature strength. However, since excessive addition of Mo and Nb deteriorates workability, Mo is limited to the range of 0.03 to 5.0 mass% and Nb is limited to the range of 0.1 to 3.0 mass%. More preferably, Mo: 0.1 to 3.0 mass% and Nb: 0.1 to 2.0 mass%. The reason for limiting the value of Mo / Nb, which is the ratio of Mo to Nb, to the range of 0.1 to 30 is that Mo / Nb is the amount of Fe—Cr—Si—Mo—Nb based intermetallic compound generated. When it is less than 0.1 or more than 30, it is similar to the case of adding Nb or Mo alone, and the amount of intermetallic compound effective for improving oxidation resistance is reduced. It is. Preferably, 0.5 ≦ Mo / Nb ≦ 30.
[0020]
Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Zr, Hf: 1.0 mass% or less in total Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Zr, and Hf are small amounts. It has the effect of improving the oxidation resistance by improving the adhesion of the oxide film when added. However, excessive addition degrades hot workability, so the content is limited to 1.0 mass% or less. More preferably, it is 0.005 to 0.5 mass%.
[0021]
In the present invention, the following elements may be contained, if necessary, in addition to the above essential components.
P: 0.05 mass% or less, S: 0.05 mass% or less, N: 0.5 mass% or less, Cu: 0.20 mass% or less, Ni: 1.0 mass% or less, V: 1.0 mass% or less, W: 3.0 mass% or less, Ta: 2.0 mass% or less, Ti: 0.5 mass% or less, Mg: 0.05 mass% or less, Ca: 0.05 mass% or less, Co: 5.0 mass% or less
Next, the method for producing a metal material of the present invention will be briefly described.
The method of smelting a metal material according to the present invention is not particularly limited, since all generally known methods can be applied.However, for example, in the steelmaking process, smelting is performed in a converter, an electric furnace, or the like. It is preferable to perform secondary refining by vacuum oxygen decarburization treatment (SS-VOD). As the casting method, continuous casting is preferable from the viewpoint of productivity and quality. The slab obtained by casting is reheated if necessary, hot-rolled, annealed at 700 to 1200 ° C., and then pickled. The hot-rolled sheet may be further cold-rolled, or may be further subjected to an annealing and pickling treatment at 700 to 1200 ° C.
[0023]
【Example】
Various steels having the component compositions shown in Table 1 were smelted by converter-secondary refining and made into slabs having a thickness of 200 mm by continuous casting. After heating these slabs to 1100 to 1300 ° C, they were hot-rolled into hot-rolled sheets having a thickness of 5 mm, and subjected to hot-rolled sheet annealing at 700 to 1200 ° C and pickling. Next, a cold-rolled sheet having a thickness of 1 mm was formed by cold rolling, and annealed at 700 to 1200 ° C. A sample of 1 mm × 30 mm × 30 mm was cut out from this cold-rolled annealed plate and subjected to the following oxidation resistance test.
[0024]
-Oxidation weight increase measurement: An oxidation test was conducted in which the above test piece was heated and held in a furnace in an air atmosphere with a dew point of 30 ° C. heated to 800 ° C. for 1000 hours, and the oxidation weight gain was measured from the weight difference between the test pieces before and after the test. did.
-Peeling resistance evaluation: The surface of the sample after the above-mentioned oxidation annealing was rubbed with a nylon brush.
・ Measurement of average distance between intermetallic compounds: A cross section (30 μm × 50 μm) of the sample after the oxidation test is photographed with a scanning electron microscope or the like, and the distance to the nearest intermetallic compound of an intermetallic compound having a size of 200 nm or more is measured. Then, the average value was obtained.
[0025]
Table 2 shows the results of the above test. As is evident from Table 2, Mo, Nb, and Al were added to the Fe-Cr alloy in a composite to satisfy the conditions of the present invention. No. 1 to No. All of the materials No. 18 have a small amount of increase in oxidation, and the effect of improving the oxidation resistance is remarkably exhibited. In addition, No. 1 having excellent oxidation resistance. No. 1 to No. In all of the materials No. 18, the average interval between the precipitated intermetallic compounds is 20 μm or less.
[0026]
On the other hand, no. In the material No. 19, since the amount of C is high, C is combined with Cr, the effective Cr amount is reduced, and the oxidation resistance is reduced. No. The material No. 22 has a low Cr content, so the protection of the oxide film is poor and the oxidation resistance is low. Similarly, no. Oxidation resistance of the material No. 23 is low because of a small amount of Al. Further, when the condition of 15 ≦ Cr + 10Al ≦ 50 is not satisfied (No. 24), the protection of the oxide film is poor and the oxidation resistance is low.
[0027]
Mn suppresses the separation of oxides, but generates oxides on the surface layer because the diffusion rate in the Cr 2 O 3 film is high. Therefore, No. When the amount of Mn is large as in the material No. 21, the oxidation rate is increased. No. When the amount of Mo is small as in the case of the material No. 25, the amount of the precipitated intermetallic compound is small, and the effect of improving the oxidation resistance is small. No. When the Nb content is small as in the case of the material No. 26, the precipitation amount of the intermetallic compound is small, and the effect of improving the oxidation resistance is small. Also, when the condition of 0.1 ≦ Mo / Nb ≦ 30 is not satisfied (Nos. 27 and 28), the precipitation amount of the intermetallic compound is small and the effect of improving the oxidation resistance is small. In addition, in the case of No. In the material No. 20, the precipitation of the intermetallic compound was not promoted, and the oxidation resistance was lowered.
[0028]
[Table 1]
[Table 2]
【The invention's effect】
As described above, according to the present invention, a heat-resistant material having excellent oxidation resistance can be obtained by adding Mo, Nb, and Al to the Fe—Cr alloy in an appropriate range. Further, by adding one or more selected from Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Zr and Hf to this material, the resistance of the oxide film formed at a high temperature can be improved. The peelability can be further improved. Further, by using the heat-resistant material of the present invention, material deterioration due to use at high temperature for a long time can be suppressed, which greatly contributes to reduction of material cost.
Claims (5)
Ｍｎ：２．０ｍａｓｓ％以下、Ｃｒ：１０〜４０ｍａｓｓ％、
Ａｌ：０．０１〜３．０ｍａｓｓ％、Ｍｏ：０．０３〜５．０ｍａｓｓ％
およびＮｂ：０．１〜３．０ｍａｓｓ％を含み、かつＭｏとＮｂとは、
０．１≦Ｍｏ／Ｎｂ≦３０
の関係を満たして含み、さらにＣｒとＡｌとは、
１５≦Ｃｒ＋１０Ａｌ≦５０
の関係を満たして含み、残部がＦｅおよび不可避的不純物からなることを特徴とする耐熱材料。C: 0.20 mass% or less, Si: 0.02 to 1.0 mass%,
Mn: 2.0 mass% or less, Cr: 10 to 40 mass%,
Al: 0.01 to 3.0 mass%, Mo: 0.03 to 5.0 mass%
And Nb: 0.1 to 3.0 mass%, and Mo and Nb are:
0.1 ≦ Mo / Nb ≦ 30
And further includes Cr and Al:
15 ≦ Cr + 10Al ≦ 50
Wherein the balance is made of Fe and inevitable impurities.
Ｍｎ：２．０ｍａｓｓ％以下、Ｃｒ：１０〜４０ｍａｓｓ％、
Ａｌ：０．０１〜３．０ｍａｓｓ％、Ｍｏ：０．０３〜５．０ｍａｓｓ％
およびＮｂ：０．１〜３．０ｍａｓｓ％を含み、かつＭｏとＮｂとは、
０．１≦Ｍｏ／Ｎｂ≦３０
の関係を満たして含み、さらにＣｒとＡｌとは、
１５≦Ｃｒ＋１０Ａｌ≦５０
の関係を満たして含み、残部がＦｅおよび不可避的不純物からなり、母材の結晶粒界にはＭｏおよびＮｂを含む金属間化合物が析出し、表面にはＡｌ２Ｏ３系の酸化物層が形成されてなることを特徴とする耐熱材料。C: 0.20 mass% or less, Si: 0.02 to 1.0 mass%,
Mn: 2.0 mass% or less, Cr: 10 to 40 mass%,
Al: 0.01 to 3.0 mass%, Mo: 0.03 to 5.0 mass%
And Nb: 0.1 to 3.0 mass%, and Mo and Nb are:
0.1 ≦ Mo / Nb ≦ 30
And further includes Cr and Al:
15 ≦ Cr + 10Al ≦ 50
And the balance consists of Fe and unavoidable impurities, intermetallic compounds containing Mo and Nb are precipitated at the crystal grain boundaries of the base material, and an Al 2 O 3 -based oxide layer is formed on the surface. A heat-resistant material characterized by being formed.
Ｍｎ：２．０ｍａｓｓ％以下、Ｃｒ：１０〜４０ｍａｓｓ％、
Ａｌ：０．０１〜３．０ｍａｓｓ％、Ｍｏ：０．０３〜５．０ｍａｓｓ％
およびＮｂ：０．１〜３．０ｍａｓｓ％を含み、かつＭｏとＮｂとは、
０．１≦Ｍｏ／Ｎｂ≦３０
の関係を満たして含み、さらにＣｒとＡｌとは、
１５≦Ｃｒ＋１０Ａｌ≦５０
の関係を満たして含み、残部がＦｅおよび不可避的不純物からなり、露点３０℃の大気中における８００℃で１０００時間の酸化増量が２．０ｇ／ｍ２以下であることを特徴とする耐熱材料。C: 0.20 mass% or less, Si: 0.02 to 1.0 mass%,
Mn: 2.0 mass% or less, Cr: 10 to 40 mass%,
Al: 0.01 to 3.0 mass%, Mo: 0.03 to 5.0 mass%
And Nb: 0.1 to 3.0 mass%, and Mo and Nb are:
0.1 ≦ Mo / Nb ≦ 30
And further includes Cr and Al:
15 ≦ Cr + 10Al ≦ 50
Wherein the balance comprises Fe and unavoidable impurities, and the weight gain of oxidation at 800 ° C. for 1000 hours in the atmosphere having a dew point of 30 ° C. is 2.0 g / m 2 or less.
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| JP2003077922A JP4259151B2 (en) | 2003-03-20 | 2003-03-20 | Heat resistant material |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007191739A (en) * | 2006-01-18 | 2007-08-02 | Jfe Steel Kk | Heat resistant material having excellent oxidation resistance and brazability |
| JP2007197779A (en) * | 2006-01-27 | 2007-08-09 | Jfe Steel Kk | Manufacturing method of cr-containing steel sheet having excellent high-temperature strength and toughness, and cr-containing steel sheet |
| JP2016164309A (en) * | 2015-02-27 | 2016-09-08 | ポスコ | Ferritic stainless steel sheet excellent in intergranular corrosion resistance |
| KR20210067474A (en) * | 2019-11-29 | 2021-06-08 | 한국생산기술연구원 | Oxide dispersion strengthened Fe-based superalloy casting material and method of manufacturing the same |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007191739A (en) * | 2006-01-18 | 2007-08-02 | Jfe Steel Kk | Heat resistant material having excellent oxidation resistance and brazability |
| JP4742876B2 (en) * | 2006-01-18 | 2011-08-10 | Ｊｆｅスチール株式会社 | Heat resistant material with excellent oxidation resistance and brazing |
| JP2007197779A (en) * | 2006-01-27 | 2007-08-09 | Jfe Steel Kk | Manufacturing method of cr-containing steel sheet having excellent high-temperature strength and toughness, and cr-containing steel sheet |
| JP4715530B2 (en) * | 2006-01-27 | 2011-07-06 | Ｊｆｅスチール株式会社 | Method for producing Cr-containing steel sheet excellent in high-temperature strength and toughness, and Cr-containing steel sheet |
| JP2016164309A (en) * | 2015-02-27 | 2016-09-08 | ポスコ | Ferritic stainless steel sheet excellent in intergranular corrosion resistance |
| KR20210067474A (en) * | 2019-11-29 | 2021-06-08 | 한국생산기술연구원 | Oxide dispersion strengthened Fe-based superalloy casting material and method of manufacturing the same |
| KR102280609B1 (en) * | 2019-11-29 | 2021-07-23 | 한국생산기술연구원 | Oxide dispersion strengthened Fe-based superalloy casting material and method of manufacturing the same |
| CN115023509A (en) * | 2020-01-31 | 2022-09-06 | 日本制铁株式会社 | Antioxidant for heating alloy material and method for heating alloy material using same |
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