JP2004176162A

JP2004176162A - Copper alloy and manufacturing method therefor

Info

Publication number: JP2004176162A
Application number: JP2002346974A
Authority: JP
Inventors: Yasutaka Sugawara; 保孝菅原; Kazuhiko Fukamachi; 一彦深町
Original assignee: Nikko Metal Manufacturing Co Ltd
Current assignee: Nippon Mining Holdings Inc
Priority date: 2002-11-29
Filing date: 2002-11-29
Publication date: 2004-06-24
Anticipated expiration: 2022-11-29
Also published as: JP3729454B2

Abstract

<P>PROBLEM TO BE SOLVED: To realize the superior bendability of a copper alloy and improve the strength further, while respecting the essence of a strengthening mechanism of a copper alloy containing titanium, and adequately securing the superior characteristics. <P>SOLUTION: This copper alloy contains 2.0-4.0 mass% Ti, and 0.01-0.50 mass% one or more elements of Fe, Co, Ni, Cr, V, Zr, B and P as the third element group; and makes 50% or more of the content of the elements exist as second phase particles. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、コネクタ材等に使用する銅合金に関するものであり、特に、優れた曲げ性と強度とを同時に実現した銅合金の製造技術を提供するものである。
【０００２】
【従来の技術】
チタンを含有する銅合金（以下、「チタン銅」と称する。）は、コネクタ材等に使用され、近年その需要は益々増大の傾向にある。この傾向に対処すべく、チタン銅の析出硬化に関する研究開発が種々行われている。従来の銅合金には、チタン銅にＮｉおよびＡｌを添加するものがある（例えば、特許文献１参照。）。また、チタン銅にＡｌおよびＭｇを添加したものもある（例えば、特許文献２参照。）。さらに、チタン銅にＳｎ、ＮｉおよびＣｏを添加したものもある（例えば、特許文献３参照。）。近年においては、チタン銅にＣｒ、Ｚｒ、ＮｉおよびＦｅを添加する技術が提案されている（例えば、特許文献４参照。）。また、結晶粒の微細化に関する技術も開示されている（例えば、特許文献５参照。）。さらに、チタン銅にＺｎ、Ｃｒ、Ｚｒ、Ｆｅ、Ｎｉ、Ｓｎ、Ｉｎ、ＰおよびＳｉを添加する技術も提案されている（例えば、特許文献６参照。）。
【０００３】
【特許文献１】
特開昭４８−１０２６４５号公報
【特許文献２】
特開昭４９−１６８１３号公報
【特許文献３】
特開昭６０−６２０４６号公報
【特許文献４】
特開平４−３０９７４８号公報
【特許文献５】
特開２０００−１２６９４５号公報
【特許文献６】
特開２００２−３１２１９号公報
【０００４】
チタン銅は、溶体化処理によって過飽和固溶体を形成させ、その状態から低温時効を施すと、準安定相である変調構造が発達し、その発達段階の或る時期において著しく硬化する。これが発達し過ぎるといわゆる過時効の状態となり、最終的には安定相であるＴｉＣｕ３が析出し、この相が増えると逆に軟化してしまう。この一連の時効過程において、高い強度を示す変調構造は、不安定な過飽和固溶体から起こり得る変化であり、安定相であるＴｉＣｕ３相から準安定相である変調構造へは変化し得ない。一方、溶体化処理が不十分だった場合、母相中に固溶仕切れなかったチタンは、ＴｉＣｕ３として析出したままの状態で残ることになる。よって時効での硬化を最大限に引き出すには、その前工程の溶体化処理でＴｉＣｕ３相を完全に無くす、言い換えればチタンを完全に母相中に固溶させる必要があり、そのためには、チタンの固溶限がチタン含有量を超える温度まで加熱する必要がある。例えば、銅にチタンを３％含有させた場合には、チタンを完全に固溶させるには、８００℃以上の温度まで加熱して溶体化処理をする必要がある。また、チタン銅は他の金属材料と同様に、焼鈍工程において結晶粒を微細化することで耐力を向上させることができる。チタン銅を製造する場合には、通常の最終製造工程である再結晶焼鈍工程が溶体化処理に相当するため、この溶体化処理中に結晶粒の微細化をいかに実現するかが耐力向上の要因となる。
【０００５】
【発明が解決しようとする課題】
しかしながら、従来のようなチタンが完全に固溶する高温領域では、結晶粒が粗大化し易いので、結晶粒の微細化により耐力向上を実現するには、それより低温側で溶体化処理をしなければならない。例えば、銅にチタンを３％含有させた合金においては、前記８００℃では結晶粒が微細化しないので、７５０〜７７５℃溶体化処理をすることにより、結晶粒を微細化させているのである。このため、従来技術でチタン銅の結晶粒を微細化させたものは、チタンの固溶が十分でなく、安定相であるＴｉＣｕ３が析出してしまう。前述したように、この時点で粒界に析出したＴｉＣｕ３は、後工程の時効で硬化に寄与しないばかりか、曲げ性を悪化させるという欠点があった。またチタン銅に第３元素（Ｆｅ、Ｃｏ、Ｎｉ、Ｃｒ、Ｖ、Ｚｒ、ＢまたはＰ）を添加し、それらの成分を含んだ第２相の析出による析出硬化を狙った従来技術では、析出硬化が十分得られるだけの添加量を確保すると、変調構造の形成が阻害されるという欠点があった。またそれらの元素の析出硬化を最大限に引き出す溶体化条件及び時効条件が、チタン銅本来の変調構造による強化を最大限引き出す溶体化条件及び時効条件との間にずれが生じているため、第３元素の析出硬化とチタン銅の変調構造の発達とを十分に両立することができなかった。このように、従来技術ではチタン銅の優れた強度特性をそのまま生かした上で、プラスαの強度を得ることが難しかった。
【０００６】
本発明は、上記要請に鑑みてなされたものであり、ＴｉＣｕ３の析出を抑制して優れた曲げ性を実現するとともに、チタン銅の強化機構の本質を尊重し、その優れた特性を十分に確保することでさらなる強度向上図ることを目的とするものである。
【０００７】
【課題を解決するための手段】
本発明の銅合金は、Ｔｉを２．０〜４．０質量％含有し、第３元素群としてＦｅ、Ｃｏ、Ｎｉ、Ｃｒ、Ｖ、Ｚｒ、ＢおよびＰの中から１種以上を０．０１〜０．５０質量％含有し、第３元素の合計含有量の５０％以上が第２相粒子として存在することを特徴としている。
【０００８】
本発明では、Ｔｉの含有量を２．０〜４．０質量％としている。Ｔｉの含有量が２．０％未満の場合には、チタン銅本来の変調構造の形成による強化機構を十分に得ることがでないため、チタン銅の優れた強度を得ることができない。また４．０質量％を超える場合には、ＴｉＣｕ３が析出しやすくなり強度が劣るとともに、曲げ性を悪化させる。本発明ではＴｉの含有量を上記のように適正化することで、優れた強度および曲げ性を共に実現することができる。なお、上記強度および曲げ性をさらに高いレベルで両立させるべく、Ｔｉの含有量は２．５〜３．５質量％とするのが望ましい。
【０００９】
また本発明では、溶体化処理において十分な溶体化をなし、ＴｉＣｕ３の析出の促進と粒成長とを抑制する目的で、第２相粒子を構成する元素（第３元素群）の組成を規定している。ここで、第２相粒子とは、ＣｕとＴｉとを主成分とし、第３元素群の構成要素Ｘ（具体的にはＦｅ、Ｃｏ、Ｎｉ、Ｃｒ、Ｖ、Ｚｒ、Ｂ、Ｐ）を含有した場合に生成されるＣｕ−Ｔｉ−Ｘ系粒子をいう。このＣｕ−Ｔｉ−Ｘ系粒子は、溶体化処理中または溶体化処理前に焼鈍を施した場合でも形成することができ、再結晶後の粒成長の抑制に寄与する。なお、このＣｕ−Ｔｉ−Ｘ系粒子は熱的に安定なため、溶体化処理後は、製品までの残りの工程で冷延・時効が施されても、その形態はほとんど変化しない。Ｆｅ、Ｃｏ、Ｎｉ、Ｃｒ、Ｖ、Ｚｒ、ＢおよびＰの合計含有量が０．０１質量％未満の場合には、十分な量の第２相粒子を析出しないため、溶体化処理時に結晶粒の成長を抑制する効果が小さい。また、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｒ、Ｖ、Ｚｒ、ＢおよびＰの合計含有量が０．５０質量％を超えた場合には、第２相粒子が粗大化しやすくなるため曲げ性が悪化する。本発明では上記第３元素群の添加量の適正化を図ることにより、特に優れた曲げ性を得ることができる。
【００１０】
ただし、上記第３元素群の含有量が適正であっても、第３元素群が第２相粒子として析出していなければ、粒成長を抑制する効果が小さいので、溶体化処理時に結晶粒が粗大化し、強度の向上が見込めない。また第３元素群が母相に固溶したままでは、時効したときに変調構造の形成に乱が生じて硬化量が低下する。したがって、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｒ、Ｖ、Ｚｒ、ＢおよびＰの含有量の少なくとも半分が第２相粒子として存在していることが必要である。本発明では、第３元素群の含有量の５０％以上が第２相粒子として存在することとすることで、第３元素群の第２相粒子への含有量の適正化を図っているため、優れた曲げ性の実現と強度向上の達成とを同時に高いレベルで実現することができる。
【００１１】
また本発明の他の銅合金は、Ｔｉを２．０〜４．０質量％含有し、第３元素群としてＦｅ、Ｃｏ、Ｎｉ、Ｃｒ、Ｖ、Ｚｒ、ＢおよびＰの中から１種以上を０．０１〜０．５０質量％含有し、さらに断面検鏡によって観察される面積０．０１μｍ２以上の第２相粒子において、この第２相粒子中の第３元素群の含有率が合金中の第３元素群の含有率の１０倍以上である第２相粒子の個数の割合が、第２相粒子全体の７０％以上であることを特徴としている。
【００１２】
本発明の銅合金は、上記した銅合金と同様に、Ｔｉの含有量の適正化、第３元素群の含有量の適正化を図ることにより、優れた曲げ性の実現と強度向上の達成とを同時に実現することができる。ただし、本発明においても、上記したように、第３元素群の第２相粒子への含有量の適正化を図る必要がある。本発明では、断面検鏡によって観察される面積０．０１μｍ２以上の第２相粒子において、第２相粒子中の第３元素群の含有率が合金中の第３元素群の含有率の１０倍以上である第２相粒子の個数の割合を、第２相粒子全体の７０％以上とすることで、第３元素群の第２相粒子への含有量の適正化を図っている。このため、本発明の銅合金においても、優れた曲げ性の実現と強度向上の達成とを同時に高いレベルで実現することができる。
【００１３】
さらに、本発明の銅合金の製造方法は、上記した２つの本発明の銅合金を好適に製造するための方法であって、Ｃｕに、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｒ、Ｖ、Ｚｒ、ＢおよびＰの中から１種以上を０．０１〜０．５０質量％添加した後にＴｉを２．０〜４．０質量％添加してインゴットを製造する工程と、インゴットを到達温度Ｔ℃まで加熱する場合において、６００℃を超える温度まで昇温速度２０℃／秒以上で加熱しその後Ｔ−１００℃〜Ｔ℃の温度領域で１０秒以上加熱して固溶体を製造する工程と、固溶体に５〜５０％の冷間圧延を施し圧延材を製造する工程と、圧延材に３５０〜４５０℃で時効を施す工程とを備えることを特徴としている。
【００１４】
本発明の銅合金の製造方法によれば、Ｔｉの添加量の適正化、第３元素群の添加量の適正化を図ることにより、優れた曲げ性の実現と強度向上の達成とを同時に実現することができる。
ただし、上記したとおり、Ｔｉの添加量の適正化および第３元素群の添加量の適正化を図ったとしても、第３元素群の第２相粒子への含有量の適正化が達成されなければ所望の曲げ性および強度は得られない。第２相粒子と再結晶粒の成長との関係を明らかにしたＺｅｎｅｒの理論によれば、第２相粒子が均一に微細分散しているほど、粒成長を抑制する効果が大きいとされており、例えば、特開昭５８−２２０１３９号公報においては、このＺｅｎｅｒの理論に基づき、再結晶焼鈍工程前に第２相粒子を微細分散させた状態とする技術が開示されている。これに対し、本発明者らは、再結晶焼鈍前ではなく、まさに再結晶焼鈍工程に相当する溶体化処理の初期段階において、第２相粒子を微細分散させることにより、チタンを完全に固溶させた上で結晶粒を十分に微細化させ、曲げ性と強度とを高いレベルで両立することができるとの知見を得た。具体的には、溶体化処理での昇温速度の適正化を図ることで、上記効果を得ることができるとの知見を得て本発明を完成するに至った。すなわち、本発明では、昇温速度２０℃／秒以上で６００℃を超える温度まで加熱することで実現している。この昇温速度が２０℃／秒未満の場合には、ＴｉＣｕ３相の析出を抑制することができず、このため曲げ性が悪化する。本発明の銅合金では、上記昇温速度の適正化を図ることにより、優れた曲げ性の実現と強度向上の達成とを同時に高いレベルで実現することができる。
【００１５】
【発明の実施の形態】
以下、本発明の実施の形態について、その製造工程を順次説明する。
インゴット製造工程
適当量のＣｕに第３元素群としてＦｅ、Ｃｏ、Ｎｉ、Ｃｒ、Ｖ、Ｚｒ、ＢおよびＰの中から１種以上を０．０１〜０．５０質量％添加し、十分保持した後にＴｉを２．０〜４．０質量％添加する。第３元素群を第２相粒子として有効に作用させるためには、このインゴット製造工程で第３元素群の溶け残りをなくすため、第３元素群を添加後に十分保持する必要があり、また、ＴｉはＣｕ中に第３元素群よりも溶け易いため、第３元素群の溶解後に添加すればよい。
【００１６】
インゴット製造以降の工程
このインゴット製造工程後には、９５０℃以上で１時間以上の均質化焼鈍を行うことが望ましい。偏析をなくし、後述する溶体化処理において、第２相粒子の析出を、微細かつ均一に分散させるためであり、混粒の防止にも効果がある。その後、熱間圧延を行い、冷延と焼鈍を繰り返して、溶体化処理を行なう。途中の焼鈍でも温度が低いと第２相粒子が形成されるので、この第２相粒子が完全に固溶する温度で行う。第３元素群を添加していない通常のチタン銅であれば、その温度は８００℃でよいが、第３元素群を添加したチタン銅はその温度を９００℃以上とすることが望ましい。さらに、溶体化処理直前の冷間圧延においては、その加工度が高いほど、溶体化処理における第２相粒子の析出が均一かつ微細なものになる。なお、溶体化処理前に微細な第２相粒子を析出させるために、前述の冷延後、低温で焼鈍を行なってもよいが、効果が小さいので工程増によるコストアップを考慮すると得策とは言えない。もし上記の目的で、溶体化処理前に低温焼鈍を行う場合には、第２相粒子がオストワルド成長しにくい４５０℃以下の温度で行うことが望ましい。
【００１７】
溶体化工程
上記冷延板製造工程後に溶体化処理を行う。ここで注意すべき点は、Ｔｉの固溶限が添加量よりも大きくなる温度（Ｔｉの添加量が２〜４質量％の範囲では７３０〜８４０℃であり、例えば、Ｔｉの添加量が３質量％では８００℃）まで加熱する必要があり、その昇温過程においてＴｉＣｕ３が最も析出しやすい温度領域を素早く通過するために、少なくとも６００℃までは昇温速度を２０℃／秒以上とすることである。この昇温速度の適正化により、安定相であるＴｉＣｕ３の析出を抑制して曲げ性を向上させることができるとともに、再結晶粒の成長に対して抑制効果が高い第２相粒子、すなわち第３元素を主成分とした微細かつ均一な第２相粒子を形成させることができる。
【００１８】
冷間圧延工程・時効処理工程
上記溶体化工程後、冷間圧延および時効処理を順次行う。これらの加工は銅合金の用途に応じて通常の方法、条件で行うことができる。例えば、銅合金をコネクタ材等として使用する場合には、冷間圧延については、固溶体に５〜５０％の冷間圧延を施すことが望ましい。また時効処理については、例えば４００℃のＡｒガスなどの不活性雰囲気中で２００分程度の時効処理を施すことが望ましい。
【００１９】
【実施例】
次に、本発明の実施例を説明する。
本発明の銅合金を製造するに際しては、活性金属であるＴｉを第２成分として添加することに鑑み、溶製には真空溶解炉を用いた。また、本発明で規定した元素以外の不純物の混入による予想外の副作用の発生を未然に防止するため、原料は純度の高いものを厳選して使用した。
【００２０】
まず、実施例１〜１０および比較例１１〜２０について、Ｃｕに、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｒ、Ｖ、Ｚｒ、ＢおよびＰを表１に示す組成でそれぞれ添加した後、同表に示す組成のＴｉをそれぞれ添加した。添加元素の溶け残りがないよう添加後の保持時間にも十分に配慮した後に、これらをＡｒ雰囲気で鋳型に注入して、それぞれ約２ｋｇのインゴットを製造した。
【００２１】
【表１】

【００２２】
上記インゴットに酸化防止剤を塗布して２４時間の常温乾燥後、９５０℃×２時間の加熱により熱間圧延を施し、板厚１０ｍｍの熱延板を得た。次に偏析を抑制するためこの熱延板に再び酸化防止剤を塗布し、９５０℃×２時間の加熱を施しその後水冷した。また酸化防止材を塗布したのは、粒界酸化および表面から進入してきた酸素が添加元素成分と反応して介在物化する内部酸化を可能な限り防止するためである。各熱延板は、それぞれ機械研磨および酸洗による脱スケール後、板厚０．２ｍｍまで冷間圧延した。その後、この冷間圧延を施した圧延材を急速加熱が可能な焼鈍炉に挿入して、６００℃を超える温度まで表１に示す昇温速度で加熱し、最終的にはＴｉの固溶限が添加量より大きくなる温度（Ｔｉの添加量が３質量％では８００℃）まで加熱し、２分間保持後水冷した。この際、平均結晶粒径（ＧＳ）を切断法により測定した。その後、酸洗により脱スケール後冷間圧延して板厚０．１４ｍｍの圧延材を得た。これを不活性ガス雰囲気中で４００℃×３時間の加熱をして各実施例および各比較例の試験片とした。
【００２３】
次に、各実施例および各比較例について、圧延方向と直角方向（曲げ軸が圧延方向と同一方向）にＷ曲げ試験を行って割れの発生しない最小曲げ半径（ＭＢＲ）の板厚（ｔ）に対する比であるＭＢＲ／ｔ値を測定するとともに、０．２％耐力を測定して実施例の有効性を検証した。
また、第２相粒子の組成の確認は、次の２つの方法で行った。まず一つ目の評価方法としては、一定重量の試験片をりん酸中で溶解したものについて、メンブランフィルタ（０．１μｍメッシュ）によって第２相粒子を分離し、残存溶液中の成分を定量分析することにより、第３元素群が第２相粒子として存在していた割合を計算する方法を採用した。この方法によって、計算された値を便宜上Ａ値（％）とする。Ａ値が高いほど、本発明で添加した第３元素群が第２相粒子として存在する割合が高いことを示し、仮にＡ値が１００％であれば、すべての第３元素群が第２相粒子として存在していたことを示す。実際には、フィルタのメッシュサイズは有限であることから、すべての第２相粒子を抽出分離することは不可能である。しかしながら、分離できなかった第２相粒子を含んだ状態で残存溶液を分析する方法を採用することから、この値が５０％以下であれば、真のＡ値は必ず５０％を超えていることになり、請求項１の発明の範囲内である。もう一つの評価方法としては、電界放射型オージェ電子分光法（ＦＥ−ＡＥＳ）によって、単位面積当たりに存在する長さ０．１μｍ以上の第２相粒子の組成を全て測定し、面積０．０１μｍ２以上の第２相粒子において、第２相粒子中の第３元素群の含有率が合金中の第３元素群の含有率の１０倍以上である粒子の個数をカウントして測定した全粒子数に対する割合を求めた。この値を便宜上Ｂ値とする。さらに、第２相粒子の円相当径を求めて、１個１個の粒子面積とその組成の関係から、第３元素群が第２相粒子として存在する割合を推定し、測定視野面積を十分にとれば、Ａ値を満足するものはＢ値をもほぼ満足することを確認した。ここで、円相当径とは、断面検鏡によって観察される第２粒子と同じ面積を有する円の直径をいう。表２に各実施例および各比較例のＡ値、Ｂ値、結晶粒径（ＧＳ）、０．２％耐力（ＭＰａ）、ＭＢＲ／ｔ値をそれぞれ示す。
【００２４】
【表２】

【００２５】
表２から明らかなように、各実施例においては、いずれもＭＢＲ／ｔ値が１．０以下で０．２％耐力が８５０ＭＰａ以上となっており、優れた曲げ性と強度を同時に実現していることが判る。実施例Ｎｏ．４〜１０では、Ｔｉの添加量を特に好ましい範囲（２．５〜３．５質量％）としたことにより、０．２％耐力が著しく向上し、その値は８７０ＭＰａ以上となっている。また実施例Ｎｏ．４〜６はそれぞれＦｅ、Ｃｏ、Ｎｉに加えＰを、そして実施例Ｎｏ．９、１０はそれぞれＶ、Ｚｒに加えてＢを添加したことにより、結晶粒がさらに微細化して０．２％耐力が極めて向上し、その値は８７５ＭＰａ以上となっている。
【００２６】
一方、各比較例においては、ＭＢＲ／ｔ値が１．０を超えるものとなっているかまたは０．２％耐力が８５０ＭＰａ未満となっており、優れた曲げ性と強度を同時に実現していなことが判る。比較例Ｎｏ．１１は、Ｔｉの添加量が２．０質量％未満であるため、十分な０．２％耐力が得られていない。逆に、比較例Ｎｏ．１２は、Ｔｉの添加量が４．０質量％を超えているため、ＴｉＣｕ３が析出し、曲げ性が悪化している。比較例Ｎｏ．１３は、結晶粒微細化元素である第３元素群が添加されていないので、結晶粒が微細化せず、十分な０．２％耐力が得られていない。また比較例Ｎｏ．１３は、第２相粒子が形成されないため、結晶粒が粗大化し優れた曲げ性を得ることもできない。比較例Ｎｏ．１４〜１７は、第３元素群の添加量の合計値が０．５質量％を超えているために第２相粒子が必要以上に析出してしまい、曲げ性が悪化している。また過剰な第２相粒子の析出によって母相中のＴｉが失われ、時効硬化能が低減して十分な０．２％耐力が得られていない。比較例Ｎｏ．１８〜２０は、第３元素の添加量は適正範囲にあるが、溶体化処理でＴｉが完全に固溶する温度までの昇温速度が遅かったために、第３元素を主成分とする第２相粒子よりＴｉＣｕ３単独の析出の割合が多くなり、その結果、時効硬化能が低下し、十分な０．２％耐力が得られず、曲げ性も好ましい範囲にはない。
【００２７】
【発明の効果】
以上説明したように、本発明によれば、Ｔｉの含有量の適正化、第３元素群の含有量の適正化、および第３元素群の第２相粒子への含有量の適正化をそれぞれ図ることで、優れた曲げ性の実現と強度向上の達成とを同時に高いレベルで実現することができる。よって本発明は、コネクタ材等に好適な銅合金を製造することができる点で有望である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a copper alloy used for a connector material or the like, and more particularly to a technique for producing a copper alloy that simultaneously realizes excellent bending properties and strength.
[0002]
[Prior art]
BACKGROUND ART A copper alloy containing titanium (hereinafter, referred to as “titanium copper”) is used for connector materials and the like, and the demand thereof has been increasing in recent years. In order to cope with this tendency, various researches and developments on precipitation hardening of titanium copper have been conducted. There is a conventional copper alloy in which Ni and Al are added to titanium copper (for example, see Patent Document 1). In addition, there is a type in which Al and Mg are added to titanium copper (for example, see Patent Document 2). Furthermore, there is also a material in which Sn, Ni and Co are added to titanium copper (for example, see Patent Document 3). In recent years, a technique of adding Cr, Zr, Ni and Fe to titanium copper has been proposed (for example, see Patent Document 4). In addition, a technique related to miniaturization of crystal grains is also disclosed (for example, see Patent Document 5). Furthermore, a technique of adding Zn, Cr, Zr, Fe, Ni, Sn, In, P, and Si to titanium copper has been proposed (for example, see Patent Document 6).
[0003]
[Patent Document 1]
JP-A-48-102645 [Patent Document 2]
JP-A-49-16813 [Patent Document 3]
JP-A-60-62046 [Patent Document 4]
JP-A-4-309748 [Patent Document 5]
Japanese Patent Application Laid-Open No. 2000-126945 [Patent Document 6]
JP, 2002-31219, A
Titanium copper forms a supersaturated solid solution by solution treatment, and when subjected to low-temperature aging from that state, a modulated structure that is a metastable phase develops and hardens remarkably at a certain stage during the development stage. If this develops too much, it will be in a so-called overaged state, and eventually TiCu3, which is a stable phase, will precipitate, and if this phase increases, it will soften. In this series of aging processes, the modulated structure exhibiting high strength is a change that can occur from an unstable supersaturated solid solution, and cannot change from the TiCu3 phase, which is a stable phase, to the modulated structure, which is a metastable phase. On the other hand, when the solution treatment is insufficient, the titanium which has not been solid-solution-dissolved in the mother phase remains in a state of being precipitated as TiCu3. Therefore, in order to maximize hardening by aging, it is necessary to completely eliminate the TiCu3 phase in the solution treatment in the previous step, in other words, to completely dissolve titanium in the mother phase. Must be heated to a temperature at which the solid solubility limit exceeds the titanium content. For example, when 3% of titanium is contained in copper, it is necessary to perform a solution treatment by heating to a temperature of 800 ° C. or more to completely dissolve titanium. In addition, titanium copper can improve proof stress by making crystal grains fine in the annealing step, like other metal materials. When producing titanium copper, the recrystallization annealing step, which is the usual final production step, corresponds to the solution treatment, and how to achieve the refinement of crystal grains during this solution treatment is a factor in improving the yield strength. It becomes.
[0005]
[Problems to be solved by the invention]
However, in the high-temperature region where titanium is completely dissolved as in the past, the crystal grains are likely to be coarse. Therefore, in order to improve the yield strength by making the crystal grains fine, the solution treatment must be performed at a lower temperature side. Must. For example, in an alloy containing 3% of titanium in copper, the crystal grains are not refined at the 800 ° C., and the crystal grains are refined by performing a solution treatment at 750 to 775 ° C. For this reason, in the case where the titanium copper crystal grains are refined by the conventional technique, the solid solution of titanium is not sufficient, and TiCu3, which is a stable phase, is precipitated. As described above, TiCu3 precipitated at the grain boundary at this point does not contribute to hardening due to aging in a later step, and also has the disadvantage of deteriorating bendability. Further, in the prior art which adds a third element (Fe, Co, Ni, Cr, V, Zr, B or P) to titanium copper and aims at precipitation hardening by precipitation of a second phase containing those components, precipitation is difficult. If the amount of addition is sufficient to obtain sufficient curing, there is a disadvantage that the formation of the modulation structure is hindered. In addition, the solution and aging conditions for maximizing the precipitation hardening of these elements are different from the solution and aging conditions for maximizing the strengthening due to the titanium copper intrinsic modulation structure. The precipitation hardening of the three elements and the development of the modulated structure of titanium copper could not be sufficiently compatible. As described above, it is difficult to obtain a plus α strength by utilizing the excellent strength characteristics of titanium copper as it is in the prior art.
[0006]
The present invention has been made in view of the above demands, and realizes excellent bendability by suppressing the precipitation of TiCu3, respects the essence of the strengthening mechanism of titanium copper, and sufficiently secures its excellent characteristics. The purpose of this is to further improve the strength.
[0007]
[Means for Solving the Problems]
The copper alloy of the present invention contains Ti in an amount of 2.0 to 4.0% by mass, and contains at least one of Fe, Co, Ni, Cr, V, Zr, B and P as a third element group. It is characterized in that it is contained in an amount of from 0.01 to 0.50% by mass, and 50% or more of the total content of the third element is present as the second phase particles.
[0008]
In the present invention, the content of Ti is set to 2.0 to 4.0% by mass. When the content of Ti is less than 2.0%, it is not possible to obtain a sufficient strengthening mechanism by forming a modulation structure inherent to titanium copper, and thus it is not possible to obtain excellent strength of titanium copper. On the other hand, when the content exceeds 4.0% by mass, TiCu3 tends to precipitate and the strength is deteriorated, and the bendability is deteriorated. In the present invention, by optimizing the content of Ti as described above, both excellent strength and bendability can be realized. In addition, in order to achieve both the above-mentioned strength and bendability at a higher level, the content of Ti is desirably set to 2.5 to 3.5% by mass.
[0009]
Further, in the present invention, the composition of the elements (third element group) constituting the second phase particles is specified for the purpose of performing sufficient solution treatment in the solution treatment, promoting the precipitation of TiCu 3 and suppressing the grain growth. ing. Here, the second phase particles contain Cu and Ti as main components and contain constituent elements X (specifically, Fe, Co, Ni, Cr, V, Zr, B, and P) of the third element group. Refers to the Cu-Ti-X-based particles generated in the above case. The Cu-Ti-X-based particles can be formed even when annealing is performed during the solution treatment or before the solution treatment, and contributes to suppression of grain growth after recrystallization. Since the Cu-Ti-X-based particles are thermally stable, their morphology hardly changes after solution treatment, even if cold rolling and aging are performed in the remaining steps up to the product. If the total content of Fe, Co, Ni, Cr, V, Zr, B, and P is less than 0.01% by mass, a sufficient amount of the second phase particles will not be precipitated, so that the crystal grains during the solution treatment are not performed. The effect of suppressing the growth of is small. If the total content of Fe, Co, Ni, Cr, V, Zr, B, and P exceeds 0.50% by mass, the second phase particles are likely to be coarsened, resulting in poor bendability. In the present invention, particularly excellent bendability can be obtained by optimizing the addition amount of the third element group.
[0010]
However, even if the content of the third element group is appropriate, if the third element group is not precipitated as the second phase particles, the effect of suppressing the grain growth is small. Coarsening and improvement in strength cannot be expected. Further, if the third element group remains in a solid solution in the mother phase, the formation of the modulated structure is disturbed upon aging, and the hardening amount is reduced. Therefore, it is necessary that at least half of the contents of Fe, Co, Ni, Cr, V, Zr, B and P exist as the second phase particles. In the present invention, the content of the third element group in the second phase particles is optimized by determining that 50% or more of the content of the third element group exists as the second phase particles. In addition, the realization of excellent bendability and the improvement of strength can be simultaneously realized at a high level.
[0011]
Further, another copper alloy of the present invention contains 2.0 to 4.0% by mass of Ti, and one or more of Fe, Co, Ni, Cr, V, Zr, B and P as a third element group. In the second phase particles having an area of 0.01 μm 2 or more observed by a cross-sectional microscope, the content of the third element group in the second phase particles in the alloy The ratio of the number of the second phase particles which is 10 times or more the content of the third element group is 70% or more of the whole second phase particles.
[0012]
The copper alloy of the present invention achieves excellent bendability and improvement in strength by optimizing the content of Ti and the content of the third element group, similarly to the copper alloy described above. Can be simultaneously realized. However, in the present invention, as described above, it is necessary to optimize the content of the third element group in the second phase particles. In the present invention, the content of the third element group in the second phase particles is 10 times the content of the third element group in the alloy in the second phase particles having an area of 0.01 μm 2 or more observed by a cross-sectional microscope. By setting the ratio of the number of the second phase particles to 70% or more of the entire second phase particles, the content of the third element group in the second phase particles is optimized. For this reason, also in the copper alloy of the present invention, the achievement of excellent bendability and the improvement of strength can be simultaneously realized at a high level.
[0013]
Further, the method for producing a copper alloy of the present invention is a method for suitably producing the above-mentioned two copper alloys of the present invention, wherein Fe, Co, Ni, Cr, V, Zr, B and A step of adding at least one of P from 0.01 to 0.50% by mass and then adding 2.0 to 4.0% by mass of Ti to produce an ingot, and heating the ingot to an ultimate temperature T ° C. In this case, a step of heating to a temperature exceeding 600 ° C. at a heating rate of 20 ° C./sec or more, followed by heating in a temperature range of T-100 ° C. to T ° C. for 10 seconds or more to produce a solid solution; % Of a cold-rolled material to produce a rolled material, and a process of aging the rolled material at 350 to 450 ° C.
[0014]
ADVANTAGE OF THE INVENTION According to the manufacturing method of the copper alloy of this invention, the realization of the outstanding bending property and the achievement of the strength improvement are simultaneously achieved by optimizing the addition amount of Ti and the addition amount of the third element group. can do.
However, as described above, even if the addition amount of Ti and the addition amount of the third element group are optimized, the content of the third element group in the second phase particles cannot be achieved. However, the desired bendability and strength cannot be obtained. According to Zener's theory clarifying the relationship between the second phase particles and the growth of the recrystallized grains, the more uniformly and finely dispersed the second phase particles are, the greater the effect of suppressing the grain growth is. For example, Japanese Patent Application Laid-Open No. 58-220139 discloses a technique in which the second phase particles are finely dispersed before the recrystallization annealing step based on the Zener's theory. On the other hand, the present inventors disperse the second phase particles finely in the initial stage of the solution treatment corresponding to the recrystallization annealing step, not before the recrystallization annealing, thereby completely dissolving the titanium in the solid solution. It has been found that the crystal grains can be sufficiently refined and the flexibility and the strength can be compatible at a high level. Specifically, the inventors have found that the above effects can be obtained by optimizing the rate of temperature increase in the solution treatment, and have completed the present invention. That is, in the present invention, this is realized by heating to a temperature exceeding 600 ° C. at a heating rate of 20 ° C./sec or more. If the heating rate is less than 20 ° C./sec, the precipitation of the TiCu3 phase cannot be suppressed, and the bendability will deteriorate. In the copper alloy of the present invention, by realizing the above-mentioned rate of temperature rise, it is possible to achieve excellent bendability and strength at the same time at a high level.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the manufacturing steps of the embodiment of the present invention will be sequentially described.
Ingot manufacturing process One or more of Fe, Co, Ni, Cr, V, Zr, B and P as a third element group are added to an appropriate amount of Cu in an amount of 0.01 to 0.50% by mass. After sufficient holding, 2.0 to 4.0% by mass of Ti is added. In order for the third element group to effectively act as the second phase particles, it is necessary to sufficiently retain the third element group after addition in order to eliminate the undissolved residue of the third element group in this ingot manufacturing process. Since Ti is more soluble in Cu than the third element group, it may be added after the third element group is dissolved.
[0016]
After the ingot production process <br/> After the ingot manufacturing process, it is desirable to perform more than one hour homogenization anneal at 950 ° C. or higher. This is for eliminating segregation and dispersing the precipitation of the second phase particles finely and uniformly in the solution treatment described below, and is also effective in preventing mixed particles. Thereafter, hot rolling is performed, and cold rolling and annealing are repeated to perform a solution treatment. If the temperature is low even in the middle of the annealing, the second phase particles are formed, so that the annealing is performed at a temperature at which the second phase particles are completely dissolved. The temperature may be 800 ° C. for ordinary titanium copper to which the third element group is not added, but it is desirable that the temperature of titanium copper to which the third element group is added be 900 ° C. or higher. Furthermore, in the cold rolling immediately before the solution treatment, the higher the workability, the more uniform and fine the precipitation of the second phase particles in the solution treatment becomes. In addition, in order to precipitate fine second phase particles before the solution treatment, annealing may be performed at a low temperature after the above-described cold rolling. However, since the effect is small, considering the cost increase due to an increase in the number of steps, it is a good idea. I can not say. If low-temperature annealing is performed before the solution treatment for the above-described purpose, it is preferable to perform the annealing at a temperature of 450 ° C. or less, at which the second phase particles are less likely to undergo Ostwald growth.
[0017]
Solution treatment step A solution treatment is performed after the cold rolled sheet production step. It should be noted here that the temperature at which the solid solubility limit of Ti is larger than the addition amount is 730 to 840 ° C. when the addition amount of Ti is in the range of 2 to 4% by mass. In order to quickly pass through the temperature range where TiCu3 is most likely to precipitate during the heating process, the heating rate should be at least 20 ° C / sec at least up to 600 ° C. It is. By optimizing the heating rate, the bendability can be improved by suppressing the precipitation of TiCu3, which is a stable phase, and the second phase particles having a high effect of suppressing the growth of recrystallized grains, ie, the third phase particles, can be used. Fine and uniform second phase particles containing an element as a main component can be formed.
[0018]
Cold rolling step / aging treatment step After the above solution treatment step, cold rolling and aging treatment are sequentially performed. These processes can be performed according to ordinary methods and conditions according to the use of the copper alloy. For example, when a copper alloy is used as a connector material or the like, it is preferable that the solid solution be subjected to 5 to 50% cold rolling. As for the aging treatment, it is desirable to perform the aging treatment in an inert atmosphere such as Ar gas at 400 ° C. for about 200 minutes.
[0019]
【Example】
Next, examples of the present invention will be described.
In manufacturing the copper alloy of the present invention, a vacuum melting furnace was used for melting in view of adding Ti as an active metal as a second component. Further, in order to prevent the occurrence of unexpected side effects due to contamination with impurities other than the elements specified in the present invention, raw materials having high purity were carefully selected and used.
[0020]
First, with respect to Examples 1 to 10 and Comparative Examples 11 to 20, Fe, Co, Ni, Cr, V, Zr, B and P were added to Cu at the compositions shown in Table 1, respectively, and then the compositions shown in the table were added. Of Ti were respectively added. After giving sufficient consideration to the retention time after the addition so that the added elements do not remain undissolved, these were injected into a mold in an Ar atmosphere to produce about 2 kg of ingots.
[0021]
[Table 1]

[0022]
An antioxidant was applied to the ingot and dried at room temperature for 24 hours, followed by hot rolling by heating at 950 ° C. × 2 hours to obtain a hot-rolled sheet having a thickness of 10 mm. Next, in order to suppress segregation, an antioxidant was applied again to the hot rolled sheet, heated at 950 ° C. × 2 hours, and then cooled with water. The antioxidant is applied to prevent as much as possible the grain boundary oxidation and the internal oxidation of oxygen entering from the surface, which reacts with the additional element component to form inclusions. Each hot-rolled sheet was descaled by mechanical polishing and pickling, and then cold-rolled to a sheet thickness of 0.2 mm. Thereafter, the cold-rolled rolled material is inserted into an annealing furnace capable of rapid heating, and is heated to a temperature exceeding 600 ° C. at a heating rate shown in Table 1, and finally has a solid solubility limit of Ti. Was heated to a temperature (800 ° C. when the amount of Ti added was 3% by mass), which was maintained for 2 minutes, followed by water cooling. At this time, the average crystal grain size (GS) was measured by a cutting method. Then, it was descaled by pickling and then cold rolled to obtain a rolled material having a thickness of 0.14 mm. This was heated in an inert gas atmosphere at 400 ° C. for 3 hours to obtain test pieces of Examples and Comparative Examples.
[0023]
Next, for each example and each comparative example, a W bending test was performed in a direction perpendicular to the rolling direction (the bending axis is the same direction as the rolling direction), and the thickness (t) of the minimum bending radius (MBR) at which cracks did not occur was determined. In addition to measuring the MBR / t value, which is a ratio to, the 0.2% proof stress was measured to verify the effectiveness of the examples.
The composition of the second phase particles was confirmed by the following two methods. First, as a first evaluation method, a test piece with a fixed weight dissolved in phosphoric acid was used to separate the second phase particles using a membrane filter (0.1 μm mesh), and the components in the remaining solution were quantitatively analyzed. Then, a method of calculating the ratio of the third element group existing as the second phase particles was adopted. The value calculated by this method is referred to as A value (%) for convenience. The higher the A value is, the higher the proportion of the third element group added in the present invention as the second phase particles is. If the A value is 100%, all the third element groups are in the second phase particles. Indicates that it was present as particles. In practice, since the mesh size of the filter is finite, it is impossible to extract and separate all the second phase particles. However, since the method of analyzing the remaining solution containing the second phase particles that could not be separated is adopted, if this value is 50% or less, the true A value always exceeds 50%. Which is within the scope of the first aspect of the present invention. As another evaluation method, the composition of the second phase particles having a length of 0.1 μm or more existing per unit area is measured by field emission Auger electron spectroscopy (FE-AES), and the area is measured to be 0.01 μm 2. In the above second phase particles, the total number of particles measured by counting the number of particles in which the content of the third element group in the second phase particles is at least 10 times the content of the third element group in the alloy Was calculated. This value is referred to as B value for convenience. Further, the circle equivalent diameter of the second phase particles is determined, and the ratio of the third element group existing as the second phase particles is estimated from the relationship between each particle area and the composition thereof, and the measurement visual field area is sufficiently determined. , It was confirmed that those satisfying the A value almost satisfied the B value. Here, the term “equivalent circle diameter” refers to the diameter of a circle having the same area as the second particles observed by a cross-sectional microscope. Table 2 shows the A value, B value, crystal grain size (GS), 0.2% proof stress (MPa), and MBR / t value of each Example and each Comparative Example.
[0024]
[Table 2]

[0025]
As is clear from Table 2, in each of the examples, the MBR / t value was 1.0 or less, and the 0.2% proof stress was 850 MPa or more. It turns out that there is. Example No. In 4 to 10, the 0.2% proof stress is remarkably improved by setting the addition amount of Ti to a particularly preferable range (2.5 to 3.5% by mass), and the value is 870 MPa or more. Also, in Example No. Nos. 4 to 6 each include P in addition to Fe, Co, and Ni. In Nos. 9 and 10, by adding B in addition to V and Zr, the crystal grains are further refined and the 0.2% proof stress is extremely improved, and the value is 875 MPa or more.
[0026]
On the other hand, in each comparative example, the MBR / t value was more than 1.0 or the 0.2% proof stress was less than 850 MPa, and excellent bending properties and strength were not simultaneously realized. I understand. Comparative Example No. In No. 11, a sufficient 0.2% proof stress was not obtained because the amount of Ti added was less than 2.0% by mass. Conversely, in Comparative Example No. In No. 12, since the added amount of Ti exceeds 4.0% by mass, TiCu3 is precipitated and the bendability is deteriorated. Comparative Example No. In No. 13, since the third element group, which is a crystal grain refining element, was not added, the crystal grains were not refined, and a sufficient 0.2% proof stress was not obtained. In Comparative Example No. In No. 13, since the second phase particles are not formed, the crystal grains are coarsened, and excellent bendability cannot be obtained. Comparative Example No. In Nos. 14 to 17, since the total value of the added amount of the third element group exceeds 0.5% by mass, the second phase particles are precipitated more than necessary, and the bendability is deteriorated. Further, Ti in the mother phase is lost due to excessive precipitation of the second phase particles, and the age hardening ability is reduced, so that a sufficient 0.2% proof stress cannot be obtained. Comparative Example No. In Nos. 18 to 20, the addition amount of the third element is within an appropriate range, but the rate of temperature rise to a temperature at which Ti is completely dissolved in the solution treatment was slow, so that the second element mainly containing the third element was used. The rate of precipitation of TiCu3 alone is larger than that of the phase particles, and as a result, the age hardening ability is reduced, sufficient 0.2% proof stress cannot be obtained, and the bendability is not in a preferable range.
[0027]
【The invention's effect】
As described above, according to the present invention, optimization of the content of Ti, optimization of the content of the third element group, and optimization of the content of the third element group in the second phase particles are respectively performed. By achieving this, it is possible to simultaneously achieve excellent bendability and strength improvement at a high level. Therefore, the present invention is promising in that a copper alloy suitable for a connector material or the like can be manufactured.

Claims

A copper-based alloy containing Ti in an amount of 2.0 to 4.0 mass%, wherein at least one of Fe, Co, Ni, Cr, V, Zr, B and P as a third element group is 0.01%. A copper alloy containing 0.50% by mass and at least 50% of the total content of the third element group as second phase particles.

A copper-based alloy containing Ti in an amount of 2.0 to 4.0 mass%, wherein at least one of Fe, Co, Ni, Cr, V, Zr, B and P as a third element group is 0.01%. In the second phase particles having an area of 0.01 μm 2 or more, which are observed by a cross-sectional microscope, the content of the third element group in the second phase particles is the third element in the alloy. A copper alloy, wherein the proportion of the number of the second phase particles that are 10 times or more the group content is 70% or more of the entire second phase particles.

One or more of Fe, Co, Ni, Cr, V, Zr, B and P are added to Cu in an amount of 0.01 to 0.50% by mass, and then Ti is added in an amount of 2.0 to 4.0% by mass. Manufacturing an ingot by
In the solution treatment in which the ingot is heated to the ultimate temperature T ° C, the ingot is heated to a temperature exceeding 600 ° C at a heating rate of 20 ° C / sec or more, and then heated in a temperature range of T-100 ° C to T ° C for 10 seconds or more. A solution treatment step of forming a supersaturated solid solution,
A cold rolling step of performing cold rolling at a working ratio of 5 to 50% from the supersaturated solid solution state;
3. The method for producing a copper alloy according to claim 1, further comprising an aging treatment step of performing a heat treatment at 350 to 450 [deg.] C. on the rolled material.