JP2004124154A

JP2004124154A - Rolled wire rod of magnesium based alloy, and production method therefor

Info

Publication number: JP2004124154A
Application number: JP2002288998A
Authority: JP
Inventors: Yukihiro Oishi; 大石　幸広; Nozomi Kawabe; 河部　望
Original assignee: Sumitomo SEI Steel Wire Corp
Current assignee: Sumitomo SEI Steel Wire Corp
Priority date: 2002-10-01
Filing date: 2002-10-01
Publication date: 2004-04-22

Abstract

<P>PROBLEM TO BE SOLVED: To provide a production method for a long-length rolled wire rod of a magnesium based alloy provided with excellent strength and toughness. <P>SOLUTION: The production method is provided with a stage where a magnesium based alloy stock comprising, by weight, 1.0 to 10.0% Zn is prepared, and a stage where the stock is subjected to rolling by caliber rolls so as to be a wire shape. In the rolling, provided that the rolling temperature is defined as T<SB>r</SB>(°C), and the rolling degree in one pass is defined as R<SB>n</SB>(%), the following relations are satisfied: R<SB>n</SB>≤T<SB>r</SB>/10+7.5 in the case of T<SB>r</SB>≥200, and R<SB>n</SB>≤T<SB>r</SB>/10-2.5 in the case of T<SB>r</SB><200. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、長尺で強度と靭性に優れたマグネシウム基合金の圧延線材、及びその製造方法に関するものである。
【０００２】
【従来の技術】
マグネシウム基合金は、アルミニウムよりも軽く、比強度、比剛性が鋼やアルミニウムよりも優れており、航空機部品、自動車部品などの他、各種電気製品のボディーなどにも広く利用されている。特に、従来は、プレス成形品によく用いられており、このプレス用板材の製造方法として、圧延によるものが知られている（例えば、特許文献１、特許文献２参照）。
【０００３】
【特許文献１】
特開２００１−２００３４９号公報（特許請求の範囲参照）
【特許文献２】
特開平６−２９３９４４号公報（特許請求の範囲参照）
【０００４】
【発明が解決しようとする課題】
マグネシウム基合金は、上記のように様々な特性に優れており板材だけでなく線材や棒材に利用することが望まれているが、最密六方格子構造であるため延性に乏しく、室温での塑性加工性が極めて悪い。そのため、従来、マグネシウム基合金の線材や棒材は、熱間押出による製造が一般的である。しかし、熱間押出は、生産性を考慮すると有効な製法と言いがたく、重量数ｋｇの長尺線材の製造が検討されているが、数１０ｋｇを越えるような長尺線材、特に、線材の直径の１０００倍以上といった長尺な線材を得ることは極めて困難である。
【０００５】
そこで、本発明の目的は、長尺で優れた強度と靭性を具えるマグネシウム基合金の圧延線材を提供することにある。
【０００６】
また、本発明の別の目的は、上記マグネシウム基合金の圧延線材を高い生産性にて製造可能な製造方法を提供することにある。
【０００７】
【課題を解決するための手段】
本発明者らは、室温での加工性が極めて悪く、熱間押出では少量で短尺な棒材や線材しか得られなかったマグネシウム基合金について種々の検討を行った結果、長尺な線材や棒材を効率よく得るには、孔型圧延が好ましいとの知見を得た。特に、圧延時の圧延加工温度や圧延加工度を特定し、更に、これら温度と加工度とを組み合わせることで、強度と靭性に優れる圧延線材を製造できることを見出し、本発明を完成するに至った。
【０００８】
即ち、本発明マグネシウム基合金の圧延線材は、重量％で、Ｚｎ：１．０〜１０．０％を含むマグネシウム基合金素材の孔型圧延による圧延線材であり、以下の特性を満たすことを特徴とする。
圧延線材の直径：３ｍｍ以上１０ｍｍ以下
圧延線材の長さ：前記直径の１０００倍以上
引張強さ：２２０ＭＰａ以上
伸び：５％以上
絞り：３０％以上
【０００９】
また、更に、重量％でＭｎ：０．１〜１．０％、Ｚｒ：０．１〜２．０％から選択される元素を１種以上含むマグネシウム基合金素材も適用できる。
【００１０】
別の本発明マグネシウム基合金の圧延線材は、重量％で、Ｚｎ：１．０〜１０．０％、希土類元素：１．０〜３．０％を含むマグネシウム基合金素材の孔型圧延による圧延線材であり、以下の特性を満たすことを特徴とする。
圧延線材の直径：３ｍｍ以上１０ｍｍ以下
圧延線材の長さ：前記直径の１０００倍以上
引張強さ：１６０ＭＰａ以上
伸び：５％以上
絞り：３０％以上
【００１１】
上記本発明圧延線材に用いられるマグネシウム基合金素材は、鋳造用マグネシウム基合金と展伸用マグネシウム基合金のいずれも利用することができる。より具体的には、例えば、ＡＳＴＭ記号におけるＺＫ系、ＥＺ系などが利用できる。上記化学成分の他にはＭｇおよび不純物が含まれる合金として利用されることが一般的である。不純物には、Ｆｅ、Ｓｉ、Ｃｕ、Ｎｉ、Ｃａなどが挙げられる。
【００１２】
ＺＫ系におけるＺＫ６０はＺｎ：４．８〜６．２％、Ｚｒ：０．４％以上を含有するマグネシウム基合金である。ＥＺ系におけるＥＺ３３はＺｎ：２．０〜３．１％、Ｃｕ：０．１％以下、Ｎｉ：０．０１％以下、ＲＥ：２．５〜４．０％、Ｚｒ：０．５〜１％を含有するマグネシウム基合金である。ここで、ＲＥは希土類元素であり、通常はＰｒとＮｄの混合物が利用されることが多い。
【００１３】
マグネシウム単体では十分な強度を得ることが難しいが、上記の化学成分を含むことで好ましい強度が得られる。また、後述する製造方法により靭性にも優れた圧延線材を得ることができる。
【００１４】
本発明圧延線材は、上記の引張強度、絞り、伸びを具えることで、強度と靭性を兼ね備えることができる。より好ましい引張強度はＺＫ系で２５０ＭＰａ以上、ＥＺ系で１８０ＭＰａ以上である。より好ましい伸びはＺＫ系、ＥＺ系共に１０％以上である。より好ましい絞りはＺＫ系、ＥＺ系共に４０％以上である。
【００１５】
本発明圧延線材の直径を３ｍｍ未満とすると、偏径差が大きくなりやすく安定した形状を得にくく、圧延後に巻き取る際も困難であることから、直径の下限は、３ｍｍ以上とした。また、圧延加工は、一般に、総加工度を大きく採ることが可能であるため、総加工度が大きい加工に適する。この特徴を生かすには、線材の直径が１０ｍｍ以下のものが好ましく、直径の上限を１０ｍｍ以下とする。
【００１６】
そして、強度と靭性に優れる上記本発明マグネシウム基合金の圧延線材を得るために、マグネシウム基合金素材に孔型圧延を施す。孔型圧延は、一般の金属材料において長尺な線材を製造する方法として知られており、生産性に優れ、線材製造に有効な圧延方法である。しかし、従来は、マグネシウム基合金に孔型圧延を適用した例がなく、また、一般の金属材料と同様の条件で孔型圧延を行っても、加工性に乏しいマグネシウム基合金では、長尺な圧延線材を得ることはできない。そこで、本発明者らは、種々検討した結果、以下の圧延条件を規定する。
【００１７】
即ち、本発明製造方法は、重量％で、Ｚｎ：１．０〜１０．０％を含むマグネシウム基合金素材を用意する工程と、前記素材を孔型ロールにより圧延加工することで線状にする工程とを具える。特に、圧延加工は、圧延時の圧延加工温度をＴ_ｒ（℃）、１パスにおける圧延加工度をＲ_ｎ（％）としたとき、以下の関係を満たすよう行うことを特徴とする。
【００１８】
【数２】

【００１９】
孔型圧延とは、溝付きロールを２〜４個用い、ロール面を対向させて配置して溝部により形成される孔型の空間に素材を通して、断面形状を拘束しながら所定の形状に圧延するものである。本発明において、圧延時の圧延加工温度とは、ロールによる加工を受ける直前の素材の温度をいう。圧延加工度とは、圧延前の断面積に対する圧延後の断面積の減少割合であり、本発明では、断面減少率にあたる。
【００２０】
本発明は、上記のように圧延時の圧延加工温度と、１パスにおける圧延加工度とが一定の関係を満たした状態で圧延加工を行うことで、長尺で、かつ強度と靭性に優れたマグネシウム基合金の圧延線材を得ることができる。特に、孔型圧延を行うことで、生産性に優れる。
【００２１】
上記製造方法において、特に、前記圧延加工を多パスで行い、圧延時の総加工度を６０％以上とすることが好ましい。孔型ロールによる圧延加工を多パスで行う場合、総加工度が６０％未満では、加工度が小さく、上記圧延加工における高い加工度が得られるという特徴が発揮されない。そこで、本発明では、孔型圧延を多パスで行う場合、圧延時の総加工度を６０％以上とする。より好ましくは、８０％以上である。
【００２２】
本発明の別の構成として、前記圧延加工は、圧延開始時の圧延加工温度を３００℃以上４５０℃以下で行うことを規定する。マグネシウム基合金に孔型圧延を施す場合、合金素材の温度が高いほど、即ち、圧延加工温度が高いほど加工性が高い傾向にある。そこで、特に、孔型圧延を連続して多パスで行う場合、連続加工を行うパス数や、２パス目以降の１パスにおける加工度などを十分大きく取ることを考慮すると、素材は、圧延開始時において３００℃以上に加熱されていることが好ましい。特に、４００℃以上に加熱することがより好ましい。４００℃以上に加熱すると、合金素材は、鋳造により生じた析出物が固溶することで、圧延加工性がより向上する。また、合金素材の温度は、圧延に伴い低下していくが、予め４００℃以上に加熱された合金素材は、圧延加工途中で素材温度がある程度低下しても圧延可能であり、多パスの加工を連続して行う際に有効である。加熱温度の上限（４５０℃以下）を設けたのは、加熱及び圧延加工中に素材の表面が酸化するのを抑えるためである。
【００２３】
本発明の別の構成として、前記圧延加工は、１パス目の圧延加工度を５％以上１５％以下、圧延加工温度を２００℃以上として行うことを規定する。インゴット（合金素材）の結晶粒が極端に粗大である場合、圧延加工途中で割れなどの不良が発生することがある。本発明者らは、１パス目において加工度が５％〜１５％、圧延加工温度が２００℃以上で圧延した合金素材は、加工後、動的な再結晶を生じて微細な結晶粒となり、割れの起点となる粗大な結晶粒がなくなることで、割れの発生を防ぐことができるとの知見を得た。また、１パス目の圧延加工度が５％未満では、再結晶しにくく、１５％超では、加工度が高すぎて１パス目で割れが発生する可能性があり、圧延加工温度が２００℃未満では、圧延加工が行いにくいとの知見を得た。そこで、本発明では、圧延加工途中の割れ発生を防ぐため、１パス目の圧延加工度を５％以上１５％以下、圧延加工温度を２００℃以上に規定する。なお、上記のように圧延加工温度は、高温であるほど加工性が高い傾向にあるが、高温過ぎると素材の表面が酸化する恐れがある。そこで、圧延加工温度は、４５０℃以下であることが好ましい。特に、好ましい圧延加工温度は、３００℃以上４５０℃以下である。
【００２４】
上記において、合金素材として用いるインゴットの大きさや圧延時の圧延加工温度によっては、動的再結晶の発生が不十分である場合も考えられる。そこで、１パス目の加工の後、再加熱して、十分再結晶をさせた後、２パス目以降の加工を行うことが好ましい。加熱温度は、２００℃以上、特に２５０℃以上が好ましい。
【００２５】
以上本発明製造方法は、重量％でＭｎ：０．１〜２．０％、Ｚｒ：０．１〜２．０％、希土類元素：１．０〜３．０％から選択される元素を１種以上含むマグネシウム基合金素材においても同様に適用することができる。
【００２６】
【発明の実施の形態】
以下、本発明の実施の形態を説明する。
（実施例１）
以下に示すＺＫ６０合金（重量％でＺｎ：５．５％、Ｚｒ：０．４５％を含み、残部がＭｇおよび不純物）のインゴット（試料Ｎｏ．１−１）及び圧延線材（試料Ｎｏ．１−２）を用意し、孔型ロールにより孔型圧延を１パス行い、加工状態を調べてみた。圧延加工は、各試料に対してそれぞれ圧延加工温度、圧延加工度（断面減少率）を変化させて行った。図１に圧延加工温度、圧延加工度、加工状態を示す。また、用いたインゴット、孔型ロールの特性を以下に示す。なお、圧延加工温度は、孔型ロールによる圧延加工を受ける直前のインゴット又は圧延線材の温度とする。以下の実施例２においても同様である。
【００２７】
試料Ｎｏ．１−１：直径φ３０ｍｍのインゴット（本例における孔型圧延が１パス目）
試料Ｎｏ．１−２：直径φ５０ｍｍのインゴットに圧延加工温度約３５０℃で１パスにおける圧延加工度約２０％の孔型圧延を４パス行った直径φ３０ｍｍの圧延線材（同５パス目）
孔型ロール：ロール径φ２１５ｍｍのロールを一対対向させて用いる
【００２８】
図１は、割れの発生の有無から判断した加工の可否を示すグラフである。試料Ｎｏ．１−１及び１−２の双方とも割れが生じていない場合を○、試料Ｎｏ．１−２は割れが生じておらず、試料Ｎｏ．１−１は割れが発生した場合を△、試料Ｎｏ．１−１及び１−２の双方とも割れが発生した場合を×で示す。
【００２９】
その結果、図１に示す○及び△から圧延時の圧延加工温度をＴｒ（℃）、１パスにおける圧延加工度をＲ_ｎ（％）としたとき、以下の関係を保つ場合、割れが生じることなく圧延加工が可能であることが分かる。
【００３０】
【数３】

【００３１】
また、図１に示す△から、インゴットを直接圧延加工したもの（試料Ｎｏ．１−１）よりも、圧延加工を一度行った圧延線材に圧延加工を施したもの（試料Ｎｏ．１−２）の方が、加工性が良好であることが分かる。試料Ｎｏ．１−２は、圧延加工温度が２００℃未満であっても、図１の△に示すように加工度の限界が小さいものの圧延加工を行うことができる。このことから、２パス目以降の加工は、圧延加工温度が２００℃未満でも可能であることが分かる。但し、図１の○で示すように２００℃以上の方が好ましいと思われる。
【００３２】
更に、図１の○で示すように１パス目の圧延加工温度は、２００℃以上、特に３００℃以上とすることが好ましいことが分かる。なお、試料Ｎｏ．１−１において圧延加工温度を５００℃とした場合を調べてみると、圧延加工は可能であったが、圧延線材の表面に酸化膜が形成されていた。一方、圧延加工温度が４５０℃の圧延線材の表面には酸化膜が形成されていなかった。このことから、１パス目の圧延加工温度は、４５０℃以下が好ましいことが分かる。
【００３３】
上記実施例１と同様の調査をＥＺ３３合金（重量％でＺｎ：２．５％、Ｚｒ：０．６％、ＲＥ：２．９％を含み、残部がＭｇと不純物）の試料Ｎｏ．１−３（直径φ３０ｍｍのインゴット）、Ｎｏ．１−４（直径φ５０ｍｍのインゴットに圧延加工温度約３５０℃、１パスにおける圧延加工度約２０％の孔型圧延を４パス行った直径φ３０ｍｍの圧延線材）に対して行ったところ、図１と同様の結果を得た。
【００３４】
これらＺＫ６０合金の試料Ｎｏ．１−１’（１パス目の圧延加工温度３００℃、圧延加工度１５％）及びＥＺ３３合金の試料Ｎｏ．１−３’（１パス目の圧延加工温度３００℃、圧延加工度１５％）に対し、それぞれ圧延加工を継続し（１パスにおける圧延加工度約２５％で１２パス行う）、直径φ５．０ｍｍ、長さ１４０００ｍｍ（重量５００ｇ）の圧延線材を得た（総加工度９９％）。これら圧延線材の引張強度（ＴＳ）、伸び（ＥＬ）、絞り（ＲＡ）を調べてみたところ、試料Ｎｏ．１−１’では、ＴＳ＝２９０ＭＰａ、ＥＬ＝１２％、ＲＡ＝３９．５％であり、試料Ｎｏ．１−３’では、ＴＳ＝１７１ＭＰａ、ＥＬ＝６％、ＲＡ＝３０．６％であった。
【００３５】
また、試料Ｎｏ．１−１、１−３において、１パス目の圧延加工ができたもの（図１において○が付されたもの）に対して、１パスにおける圧延加工度を１０％として、連続して圧延加工を施してみた（５パス）。すると、１パス目の圧延加工温度が３００℃以上である試料は、１パス目の圧延加工度によらず、圧延加工途中に割れなど生じることなく圧延加工が可能であった。
【００３６】
（実施例２）
ＺＫ６０合金（重量％でＺｎ：５．５％、Ｚｒ：０．４５％を含み、残部がＭｇおよび不純物）のインゴット（直径φ３０ｍｍ）を複数準備し、圧延加工温度２００℃にて、５％、１０％、１５％、２０％の各圧延加工度で孔型ロールによる圧延加工を実施した。インゴットは、各圧延加工度に対して５本ずつ用意した。また、孔型ロールは、上記実施例１と同様のものを用いた。
【００３７】
その結果、加工度２０％の試料では、割れの発生率が４０％であった（インゴット５本中２本において割れが発生）。そして、割れが発生したインゴットの結晶状態（組織）を調べてみると、数１００μｍの粗大結晶粒が認められた。
【００３８】
加工度１５％以下の試料では、いずれの試料も５本のインゴットすべてに割れが発生せず圧延加工が可能であった。更に、加工度５％以上１５％以下の試料を２５０℃に再加熱し、種々の加工度（約１０％、約１６％、約２０％、約２５％）で圧延加工を行ったところ、その後の圧延加工では、１パスあたりの加工度が２５％の加工であっても、問題なく加工可能であった。この再加熱した試料の結晶状態を調べたところ、粗大結晶粒が消滅し、１０μｍ以下の微細な結晶粒となっていた。これらのことから、粗大結晶粒を含むインゴット（鋳造材）は、１パス目の圧延加工によって割れが発生する危険を有しているが、１パス目の圧延加工度を１５％以下、圧延加工温度を２００℃以上とすることで、圧延加工中の割れを回避することができることがわかる。また、圧延加工後、２００℃以上に再加熱して再結晶させ、結晶粒を微細にすることで、再加熱後の圧延加工によって割れが生じることを防止できることがわかる。
【００３９】
圧延加工温度を３５０℃として上記実施例２と同様に圧延加工度を変えて圧延加工を２パス行い、圧延加工後の各圧延線材の組織を調べたところ、上記のように再加熱していなくても再結晶化していた。このことから、圧延加工温度によっては、１パス目の圧延加工後の再加熱を行わなくても連続圧延が可能であることがわかる。
【００４０】
【発明の効果】
以上説明したように本発明製造方法によれば、マグネシウム基合金素材に対して所定の条件にて孔型圧延を施すことで、長尺で、強度及び靭性に優れたマグネシウム基合金の圧延線材を得ることができるという優れた効果を奏し得る。特に、本発明製造方法は、マグネシウム基合金において従来から行われていた押出加工と比較して高い生産性を有する。また、得られた本発明圧延線材は、加工性にも優れ、その後の引き抜き加工などの加工素材としても用いることができる。
【図面の簡単な説明】
【図１】ＺＫ６０合金に圧延加工温度と圧延加工度とを変化させて孔型圧延を施した際の圧延加工の可否を示すグラフである。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnesium-based alloy rolled wire having a long length and excellent strength and toughness, and a method for producing the same.
[0002]
[Prior art]
Magnesium-based alloys are lighter than aluminum, have higher specific strength and specific rigidity than steel and aluminum, and are widely used for bodies of various electric products in addition to aircraft parts and automobile parts. In particular, conventionally, it is often used for a press-formed product, and a method of manufacturing this press plate material by rolling is known (for example, see Patent Documents 1 and 2).
[0003]
[Patent Document 1]
JP 2001-200349 A (see claims)
[Patent Document 2]
JP-A-6-293944 (refer to claims)
[0004]
[Problems to be solved by the invention]
Magnesium-based alloys are excellent in various properties as described above and are desired to be used not only for sheets but also for wires and rods.However, since they have a close-packed hexagonal lattice structure, they have poor ductility and are not suitable for use at room temperature. Very poor plastic workability. For this reason, conventionally, wires and bars of magnesium-based alloys are generally manufactured by hot extrusion. However, it is difficult to say that hot extrusion is an effective manufacturing method in consideration of productivity, and production of a long wire having a weight of several kilograms is being studied. It is extremely difficult to obtain a long wire having a diameter of 1000 times or more.
[0005]
Therefore, an object of the present invention is to provide a magnesium-based alloy rolled wire that is long and has excellent strength and toughness.
[0006]
Another object of the present invention is to provide a production method capable of producing a rolled wire of the magnesium-based alloy with high productivity.
[0007]
[Means for Solving the Problems]
The present inventors have conducted various studies on magnesium-based alloys, which were extremely poor in workability at room temperature and could only obtain short rods and wires in a small amount by hot extrusion. It has been found that grooved rolling is preferable for efficiently obtaining a material. In particular, the rolling temperature and the degree of rolling at the time of rolling are specified, and further, by combining these temperatures and the degree of working, it has been found that a rolled wire rod having excellent strength and toughness can be produced, and the present invention has been completed. .
[0008]
That is, the rolled wire of the magnesium-based alloy of the present invention is a rolled wire obtained by groove-rolling a magnesium-based alloy material containing Zn: 1.0 to 10.0% by weight, and satisfies the following characteristics. And
Diameter of rolled wire: 3 mm or more and 10 mm or less Length of rolled wire: 1000 times or more of the above diameter Tensile strength: 220 MPa or more Elongation: 5% or more Drawing: 30% or more
Further, a magnesium-based alloy material containing at least one element selected from Mn: 0.1 to 1.0% and Zr: 0.1 to 2.0% by weight is also applicable.
[0010]
Another rolled wire of the magnesium-based alloy of the present invention is a magnesium-based alloy material containing 1.0 to 10.0% of Zn and 1.0 to 3.0% of a rare earth element by weight, and is rolled by groove rolling. The wire is characterized by satisfying the following characteristics.
Diameter of rolled wire: 3 mm or more and 10 mm or less Length of rolled wire: 1000 times or more of the above diameter Tensile strength: 160 MPa or more Elongation: 5% or more Drawing: 30% or more
As the magnesium-based alloy material used in the rolled wire of the present invention, any of a magnesium-based alloy for casting and a magnesium-based alloy for wrought can be used. More specifically, for example, the ZK system and the EZ system in the ASTM symbol can be used. In general, it is used as an alloy containing Mg and impurities in addition to the above chemical components. The impurities include Fe, Si, Cu, Ni, Ca and the like.
[0012]
ZK60 in the ZK system is a magnesium-based alloy containing 4.8 to 6.2% of Zn and 0.4% or more of Zr. EZ33 in the EZ system is Zn: 2.0 to 3.1%, Cu: 0.1% or less, Ni: 0.01% or less, RE: 2.5 to 4.0%, Zr: 0.5 to 1 % Based magnesium alloy. Here, RE is a rare earth element, and usually a mixture of Pr and Nd is often used.
[0013]
Although it is difficult to obtain sufficient strength with magnesium alone, preferable strength can be obtained by including the above-mentioned chemical components. In addition, a rolled wire excellent in toughness can be obtained by a manufacturing method described later.
[0014]
The rolled wire rod of the present invention can have both strength and toughness by providing the above-described tensile strength, drawing, and elongation. More preferable tensile strength is 250 MPa or more in ZK system and 180 MPa or more in EZ system. More preferred elongation is 10% or more for both ZK and EZ. A more preferable aperture is 40% or more for both the ZK system and the EZ system.
[0015]
If the diameter of the rolled wire of the present invention is less than 3 mm, the difference in eccentricity tends to be large, and it is difficult to obtain a stable shape, and it is difficult to wind up after rolling. Therefore, the lower limit of the diameter is 3 mm or more. In addition, since the rolling process can generally take a large total working degree, it is suitable for processing with a large total working degree. In order to take advantage of this feature, the diameter of the wire is preferably 10 mm or less, and the upper limit of the diameter is 10 mm or less.
[0016]
Then, in order to obtain a rolled wire of the magnesium-based alloy of the present invention having excellent strength and toughness, the magnesium-based alloy material is subjected to groove rolling. Groove rolling is known as a method for producing a long wire from a general metal material, and is a rolling method which is excellent in productivity and is effective for producing a wire. However, conventionally, there has been no example of applying grooved rolling to a magnesium-based alloy, and even if grooved rolling is performed under the same conditions as a general metal material, a magnesium-based alloy with poor workability has a long length. Rolled wire cannot be obtained. The present inventors have determined the following rolling conditions as a result of various studies.
[0017]
That is, in the manufacturing method of the present invention, a magnesium-based alloy material containing Zn: 1.0 to 10.0% by weight is prepared, and the material is linearized by being rolled by a grooved roll. Process. In particular, the rolling is performed so that the following relationship is satisfied when the rolling temperature during rolling is _Tr (° C.) and the degree of rolling in one pass is R _n (%).
[0018]
(Equation 2)

[0019]
With the groove rolling, two to four grooved rolls are used, the roll surfaces are arranged to face each other, and the material is passed through a groove-shaped space formed by the groove, and is rolled into a predetermined shape while restricting the cross-sectional shape. Things. In the present invention, the rolling temperature during rolling refers to the temperature of a material immediately before being processed by a roll. The rolling degree is a reduction ratio of a cross-sectional area after rolling to a cross-sectional area before rolling, and in the present invention, corresponds to a cross-sectional reduction rate.
[0020]
The present invention, as described above, by performing the rolling process in a state where the rolling process temperature at the time of rolling, and the degree of rolling in one pass satisfies a certain relationship, it is long, and excellent in strength and toughness A magnesium-based alloy rolled wire can be obtained. In particular, productivity is excellent by performing groove rolling.
[0021]
In the above-mentioned manufacturing method, it is particularly preferable that the rolling process is performed in multiple passes, and the total working ratio during rolling is 60% or more. In the case of performing rolling by a roll in multiple passes, if the total working degree is less than 60%, the working degree is small, and the feature that a high working degree in the above-described rolling processing is obtained is not exhibited. Therefore, in the present invention, when the groove rolling is performed in multiple passes, the total working ratio at the time of rolling is set to 60% or more. More preferably, it is at least 80%.
[0022]
As another configuration of the present invention, it is specified that the rolling is performed at a rolling temperature of 300 ° C. to 450 ° C. at the start of rolling. When performing groove rolling on a magnesium-based alloy, the higher the temperature of the alloy material, that is, the higher the rolling temperature, the higher the workability tends to be. Therefore, in particular, when the groove rolling is continuously performed in multiple passes, considering the number of passes to be continuously processed and the degree of working in the first pass after the second pass and the like are sufficiently large, the material is not subjected to the rolling start. In some cases, the heating is preferably performed at 300 ° C. or higher. In particular, heating to 400 ° C. or more is more preferable. When the alloy material is heated to 400 ° C. or higher, the precipitate formed by casting is dissolved in the alloy material, so that the rolling processability is further improved. In addition, the temperature of the alloy material decreases with rolling, but the alloy material preheated to 400 ° C. or higher can be rolled even if the material temperature is reduced to some extent during the rolling process. It is effective when performing continuously. The upper limit of the heating temperature (450 ° C. or less) is provided to suppress oxidation of the surface of the material during heating and rolling.
[0023]
As another configuration of the present invention, it is specified that the rolling is performed at a rolling degree of the first pass of 5% or more and 15% or less and a rolling temperature of 200 ° C. or more. If the crystal grains of the ingot (alloy material) are extremely coarse, defects such as cracks may occur during rolling. The present inventors have found that the alloy material rolled at a working degree of 5% to 15% and a rolling processing temperature of 200 ° C. or more in the first pass causes dynamic recrystallization after processing, resulting in fine crystal grains, It has been found that the occurrence of cracks can be prevented by eliminating coarse crystal grains serving as crack starting points. If the rolling degree in the first pass is less than 5%, recrystallization is difficult, and if it exceeds 15%, the degree of working is too high and cracks may occur in the first pass. If it is less than the above, it was found that the rolling process is difficult to perform. Therefore, in the present invention, the rolling degree in the first pass is specified to be 5% or more and 15% or less, and the rolling temperature is specified to be 200 ° C. or more in order to prevent the occurrence of cracks during rolling. As described above, as the rolling temperature is higher, the workability tends to be higher. However, if the temperature is too high, the surface of the material may be oxidized. Therefore, the rolling temperature is preferably 450 ° C. or less. In particular, a preferable rolling temperature is 300 ° C or more and 450 ° C or less.
[0024]
In the above description, depending on the size of the ingot used as the alloy material and the rolling temperature at the time of rolling, the occurrence of dynamic recrystallization may be insufficient. Therefore, it is preferable that after the processing in the first pass, reheating is performed to sufficiently recrystallize, and then the processing in the second and subsequent passes is performed. The heating temperature is preferably 200 ° C. or higher, particularly preferably 250 ° C. or higher.
[0025]
As described above, in the production method of the present invention, one element selected from Mn: 0.1 to 2.0%, Zr: 0.1 to 2.0%, and rare earth element: 1.0 to 3.0% by weight is 1 The same can be applied to a magnesium-based alloy material containing more than one kind.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
(Example 1)
An ingot (sample No. 1-1) and a rolled wire (sample No. 1-) of the following ZK60 alloy (containing 5.5% by weight of Zn and 0.45% of Zr, with the balance being Mg and impurities). 2) was prepared, and the groove rolling was performed by a groove roll for one pass, and the processing state was examined. Rolling was performed by changing the rolling temperature and the degree of rolling (cross-sectional reduction rate) for each sample. FIG. 1 shows the rolling temperature, the rolling degree, and the processing state. In addition, the characteristics of the ingots and the hole type rolls used are shown below. The rolling temperature is the temperature of the ingot or the rolled wire immediately before being subjected to rolling by the grooved roll. The same applies to the following Example 2.
[0027]
Sample No. 1-1: Ingot of φ30 mm in diameter (the first pass of the groove rolling in this example)
Sample No. 1-2: Rolled wire having a diameter of 30 mm (fifth pass) in which an ingot having a diameter of φ50 mm was subjected to four passes of roll forming at a rolling processing temperature of about 350 ° C. and a rolling degree of about 20% in one pass in four passes.
Perforated roll: A pair of rolls having a roll diameter of 215 mm are used to face each other.
FIG. 1 is a graph showing the possibility of processing determined from the presence or absence of cracks. Sample No. In the case where cracks did not occur in both of 1-1 and 1-2, ○, sample No. In Sample No. 1-2, no crack was generated, and in Sample No. 1-2. Sample No. 1-1 shows the case where cracks occurred. The case where cracks occurred in both 1-1 and 1-2 is indicated by x.
[0029]
As a result, when the rolling temperature during rolling is represented by Tr (° C.) and the degree of rolling in one pass is represented by R _n (%), cracks may occur from the circles and circles shown in FIG. It can be seen that the rolling process is possible without any.
[0030]
[Equation 3]

[0031]
In addition, from △ shown in FIG. 1, a rolled wire rod that has been once rolled is processed (sample No. 1-2), compared to a rolled ingot directly (sample No. 1-1). Shows that the workability is better. Sample No. 1-2, even if the rolling temperature is lower than 200 ° C., the rolling process can be performed although the limit of the working degree is small as shown by Δ in FIG. From this, it is understood that the processing after the second pass can be performed even when the rolling processing temperature is lower than 200 ° C. However, it is considered that 200 ° C. or higher is preferable, as indicated by the circle in FIG.
[0032]
Further, as indicated by the circle in FIG. 1, it is understood that the rolling temperature in the first pass is preferably 200 ° C. or more, particularly preferably 300 ° C. or more. The sample No. When the case where the rolling temperature was set to 500 ° C. in 1-1 was examined, rolling was possible, but an oxide film was formed on the surface of the rolled wire. On the other hand, no oxide film was formed on the surface of the rolled wire having a rolling temperature of 450 ° C. This indicates that the rolling temperature in the first pass is preferably 450 ° C. or less.
[0033]
Investigations similar to those in Example 1 were conducted on sample No. EZ33 alloy (containing 2.5% by weight of Zn, 0.6% of Zr, 2.9% of RE, and the balance being Mg and impurities). No. 1-3 (ingot of φ30 mm in diameter), 1 to 4 (rolled wire having a diameter of 30 mm obtained by performing four passes of ingot rolling with a rolling process temperature of about 350 ° C. in one pass on an ingot having a diameter of 50 mm and a rolling degree of about 20% in one pass). Similar results were obtained.
[0034]
These ZK60 alloy sample Nos. Sample No. 1-1 ′ (rolling temperature of the first pass: 300 ° C., rolling degree: 15%) and EZ33 alloy sample no. For 1-3 ′ (rolling temperature of the first pass: 300 ° C., rolling degree: 15%), rolling is continued (12 passes at a rolling degree of about 25% in one pass), and φ5.0 mm in diameter Thus, a rolled wire rod having a length of 14000 mm (weight 500 g) was obtained (total processing degree: 99%). The tensile strength (TS), elongation (EL), and drawing (RA) of these rolled wires were examined. In the case of Sample No. 1-1 ′, TS = 290 MPa, EL = 12%, RA = 39.5%. For 1-3 ′, TS = 171 MPa, EL = 6%, RA = 30.6%.
[0035]
Further, the sample No. In 1-1 and 1-3, the rolling process in the first pass was performed (the circle marked in FIG. 1) and the rolling process in the first pass was 10%, and the rolling process was continued. (5 passes). Then, the sample in which the rolling temperature in the first pass was 300 ° C. or higher was able to be rolled without generating cracks or the like during rolling regardless of the degree of rolling in the first pass.
[0036]
(Example 2)
A plurality of ingots (diameter φ30 mm) of a ZK60 alloy (containing 5.5% by weight of Zn and 0.45% by weight of Zr, with the balance being Mg and impurities) were prepared, and 5% Rolling was performed with a grooved roll at each rolling degree of 10%, 15%, and 20%. Five ingots were prepared for each rolling degree. The same roll as in Example 1 was used as the roll.
[0037]
As a result, in the sample with a workability of 20%, the crack occurrence rate was 40% (cracks occurred in two out of five ingots). When the crystal state (structure) of the cracked ingot was examined, coarse crystal grains of several 100 μm were recognized.
[0038]
With the samples having a working degree of 15% or less, any of the five ingots could be rolled without cracking. Further, a sample having a working degree of 5% or more and 15% or less was reheated to 250 ° C., and rolled at various working degrees (about 10%, about 16%, about 20%, about 25%). In the rolling process, the processing could be performed without any problem even if the processing degree per pass was 25%. Examination of the crystal state of the reheated sample revealed that coarse crystal grains had disappeared and fine crystal grains of 10 μm or less had been formed. From these facts, an ingot (cast material) containing coarse crystal grains has a risk of generating cracks by rolling in the first pass. It is understood that cracking during rolling can be avoided by setting the temperature at 200 ° C. or higher. In addition, it can be seen that, after rolling, re-heating by reheating to 200 ° C. or higher to recrystallize the crystal grains makes it possible to prevent generation of cracks due to rolling after reheating.
[0039]
The rolling process temperature was set to 350 ° C., and the rolling process was performed in two passes while changing the degree of rolling process in the same manner as in Example 2, and the structure of each rolled wire after the rolling process was examined. Even recrystallized. This indicates that continuous rolling is possible depending on the rolling temperature without reheating after the rolling in the first pass.
[0040]
【The invention's effect】
As described above, according to the manufacturing method of the present invention, a magnesium-based alloy material is subjected to grooved rolling under predetermined conditions to obtain a long, rolled magnesium-based alloy wire having excellent strength and toughness. An excellent effect that it can be obtained can be obtained. In particular, the production method of the present invention has higher productivity as compared with the extrusion processing conventionally performed on a magnesium-based alloy. Further, the obtained rolled wire of the present invention is excellent in workability and can be used as a raw material for subsequent drawing or the like.
[Brief description of the drawings]
FIG. 1 is a graph showing whether or not rolling can be performed when a ZK60 alloy is subjected to groove-rolling while changing the rolling temperature and the degree of rolling.

Claims

Weight percent, is a rolled wire rod obtained by groove-rolling a magnesium-based alloy material containing Zn: 1.0 to 10.0%,
The diameter of the rolled wire rod is 3 mm or more and 10 mm or less,
The length of the rolled wire is 1000 times or more of the diameter,
Tensile strength is 220MPa or more,
The elongation is 5% or more,
A rolled wire of a magnesium-based alloy, wherein the reduction is 30% or more.

2. The magnesium-based alloy according to claim 1, further comprising at least one element selected from the group consisting of Mn: 0.1 to 1.0% and Zr: 0.1 to 2.0% by weight. Rolled wire rod.

A weight-% rolled wire rod obtained by groove-rolling a magnesium-based alloy material containing Zn: 1.0 to 10.0% and a rare earth element: 1.0 to 3.0%,
The diameter of the rolled wire rod is 3 mm or more and 10 mm or less,
The length of the rolled wire is 1000 times or more of the diameter,
Tensile strength is 160MPa or more,
The elongation is 5% or more,
A rolled wire of a magnesium-based alloy, wherein the reduction is 30% or more.

Preparing a magnesium-based alloy material containing Zn: 1.0 to 10.0% by weight;
A step of rolling the raw material with a grooved roll to form a linear shape,
The rolling process,
A method for producing a rolled wire of a magnesium-based alloy, wherein the following relationship is satisfied when the rolling temperature during rolling is _Tr (° C.) and the degree of rolling in one pass is R _n (%). .

The method according to claim 4, wherein the rolling is performed in multiple passes, and the total working degree during rolling is 60% or more.

Preparing a magnesium-based alloy material containing Zn: 1.0 to 10.0% by weight;
A step of rolling the raw material with a grooved roll to form a linear shape,
The rolling process,
A method for producing a rolled wire of a magnesium-based alloy, wherein the rolling temperature at the start of rolling is from 300 ° C to 450 ° C.

Preparing a magnesium-based alloy material containing Zn: 1.0 to 10.0% by weight;
A step of rolling the raw material with a grooved roll to form a linear shape,
The rolling process,
A method for producing a magnesium-based alloy rolled wire, wherein the rolling degree in the first pass is 5% or more and 15% or less and the rolling temperature is 200 ° C or more.

The method for producing a magnesium-based alloy rolled wire according to claim 7, wherein the rolling process in the second and subsequent passes is performed by reheating the material to 200 ° C or higher.

Further, a material containing at least one element selected from the group consisting of Mn: 0.1 to 2.0%, Zr: 0.1 to 2.0%, and rare earth element: 1.0 to 3.0% by weight. The method for producing a magnesium-based alloy rolled wire according to any one of claims 4 to 8, which is used.