JP3594823B2

JP3594823B2 - Processing method of extruded aluminum alloy

Info

Publication number: JP3594823B2
Application number: JP35363998A
Authority: JP
Inventors: 久男谷川; 紘一大堀
Original assignee: Mitsubishi Aluminum Co Ltd
Current assignee: MA Aluminum Corp
Priority date: 1998-12-11
Filing date: 1998-12-11
Publication date: 2004-12-02
Anticipated expiration: 2018-12-11
Also published as: JP2000178704A

Description

【０００１】
【発明の属する技術分野】
本発明は、Ａｌ合金押出形材の加工方法に関し、特に、スペースフレーム構造のＡｌ製車体構造を構成するサイドメンバ−等のエネルギー吸収特性に優れたＡｌ合金押出形材を製造する際に用いて好適なＡｌ合金押出形材の加工方法に関するものである。
【０００２】
【従来の技術】
自動車のサイドメンバ−は、自動車の前方のエンジン部分と、後方のトランク部分において、衝突時にアコ−ディオン状に座屈変形し、これにより衝突時の衝撃エネルギ−を吸収することにより、乗員の安全性を確保する機能を持つ部材である。
このサイドメンバ−としては、車体前方のエンジンルーム下部から後方に向かって延び客室前方フロアの構造部材に接続されるフロントサイドメンバー、客室後方フロアの構造部材から後方に延びトランクルーム下部に達するリヤサイドメンバー等がある。
【０００３】
従来のサイドメンバ−は、冷延鋼板にプレス成形加工を施し、スポット溶接等を用いて接合した断面矩形状の筒状部材が用いられている。
ところで、近年、地球の温暖化等の環境問題から、排ガス低減や燃費向上等を目的として自動車の軽量化が強く要請されており、この軽量化の一環として、鋼板や鋼管を用いる代わりに、軽量で、かつ複雑形状の構造物を一体で製造できるＡｌやＴｉ等の軽金属を主成分とする軽合金押出形材が検討されている。
このような押出形材に適した軽合金としては、現在は主として押出性、機械的性質、および耐食性などのバランスの良いＪＩＳ６Ｎ０１合金などのＡｌ−Ｍｇ−Ｓｉ系Ａｌ合金が使用されている。
【０００４】
例えば、サイドメンバ−等のスペースフレーム構造のＡｌ製車体構造を構成する部材を製造するには、まず、Ａｌ合金を押出成形することにより各種断面形状を有するＡｌ合金押出材とする。次いで、このＡｌ合金押出材に、該Ａｌ合金の最高強度が得られる時効条件で時効硬化処理を行い、その後曲げ加工を行う。次いで、溶接等の接合加工を行いＡｌ車体構造用部材とする（Ａ工程）。
また、前記Ａｌ合金押出材に曲げ加工を行い、その後該Ａｌ合金の最高強度が得られる時効条件で時効硬化処理を行う点以外は上述したＡ工程と同様としたＢ工程によりＡｌ車体構造用部材を得ることもできる。
【０００５】
【発明が解決しようとする課題】
ところで、上述した従来のＡｌ製車体構造を構成する部材、特に、衝突時にアコ−ディオン状に座屈変形して前後方向から加わるエネルギーを吸収するサイドメンバーにおいては、製造工程中の曲げ加工性が良いと同時に、アコ−ディオン状に座屈変形することで衝突時のエネルギーを充分に吸収し、乗員の被害が最小となるようにする機能も要求される。
【０００６】
従来のＡ工程においては、Ａｌ合金押出材に時効硬化処理を行った後に曲げ加工を行っているために、該押出材の曲げ加工時に割れが生じたり、あるいは軸圧縮荷重負荷時に割れが生じる虞があるという問題点がある。
また、従来のＢ工程においては、Ａｌ合金押出材に曲げ加工を行った後に時効硬化処理を行っているために、該押出材の曲げ加工時に断面変形が大きくなる虞があるという問題点がある。
以上により、上述したＡ工程、Ｂ工程のいずれの工程においても、曲げ加工性とエネルギー吸収特性とを両立させることは困難であり、どちらかが犠牲になってしまうという問題点がある。
【０００７】
本発明は上記の事情に鑑みてなされたものであって、曲げ加工性及びエネルギー吸収特性に優れたＡｌ合金押出形材を製造することのできるＡｌ合金押出形材の加工方法を提供することを目的とする。
【０００８】
【課題を解決するための手段】
本発明者等は、上記課題を解決するために、Ａｌ合金押出材の曲げ加工性及びエネルギー吸収特性に及ぼす製造工程の影響を明らかにすべく種々の実験を行った結果、本発明に係る組成のＡｌ合金押出材に、第１の熱処理、曲げ加工、第２の熱処理を順次行うことにより、曲げ加工性及びエネルギー吸収特性に優れたＡｌ合金押出形材が得られることを知見した。
【０００９】
本発明は以上の知見に基づくものであり、請求項１記載のＡｌ合金押出形材の加工方法は、Ｓｉを０．６〜１．２重量％、Ｍｇを０．５〜１．０重量％、Ｆｅを０．１〜０．４重量％、Ｍｎを０．２〜０．６重量％、Ｔｉを０．００５〜０．１重量％、Ｃｒを０．０５〜０．３重量％および／またはＺｒを０．０５〜０．２５重量％含有し、残部がＡｌ及び不可避不純物からなるＡｌ合金を押出成形し、得られたＡｌ合金押出材に１２０〜１８０℃で１〜２４時間保持の亜時効条件で第１の熱処理を行い、次いで、曲げ加工を行い、その後、第１の熱処理以上の温度でかつ、１５０〜２２０℃で１〜２４時間保持の過時効条件で第２の熱処理を行うことを特徴としている。
【００１０】
請求項２記載のＡｌ合金押出形材の加工方法は、請求項１記載のＡｌ合金押出形材の加工方法において、前記Ａｌ合金は、Ｃｕを０．４〜０．８重量％含有することを特徴としている。
【００１１】
請求項３記載のＡｌ合金押出形材の加工方法は、請求項１または２記載のＡｌ合金押出形材の加工方法において、前記押出材は、断面が多角形状の中空押出材からなることを特徴としている。
【００１３】
本発明のＡｌ合金押出形材の加工方法では、Ａｌ合金を押出成形し、得られたＡｌ合金押出材に該Ａｌ合金の最高強度が得られる時効条件より手前の時効条件で第１の熱処理を行うことにより、この第１の熱処理が施されたＡｌ合金押出材では微細な析出物が発生することで伸びが良くしかも硬すぎることがなく、曲げ加工性に優れたものとなる。次いで、曲げ加工を行うことにより、伸びの値が高く複雑な曲げ形状にも曲げ加工することが可能となる。しかも、時効硬化も進んでいるので、降伏強さも高い。例えば、曲げ加工するＡｌ合金押出材が中空部を有する場合、該中空部の断面変形を小さく抑えることが可能になる。
【００１４】
この曲げ加工を行ったＡｌ合金押出材は、エネルギー吸収特性が劣っていることから、前記Ａｌ合金の最高強度が得られる時効条件を越えた時効条件で第２の熱処理を行うことにより、この第２の熱処理が施されたＡｌ合金押出材では析出物が粗大化することで、高強度でありながら低強度合金と同様の圧縮荷重時の変形挙動が可能になり、エネルギー吸収特性を高めることが可能になる。
第１及び第２の熱処理の条件は合金組成により変動するが、本発明に係るＡｌ合金の場合、第１の熱処理では、１２０〜１８０℃の範囲とし、保持時間を１〜２４時間とし、また第２の熱処理では、第１の熱処理以上の温度でかつ、１５０〜２２０℃の範囲とし、保持時間を１〜２４時間とすればよい。
【００１５】
次に、本発明に係るＡｌ合金の組成を限定した理由について説明する。
本発明に係るＡｌ合金は、Ｓｉを０．６〜１．２重量％、Ｍｇを０．５〜１．０重量％、Ｆｅを０．１〜０．４重量％、Ｍｎを０．２〜０．６重量％、Ｔｉを０．００５〜０．１重量％、Ｃｒを０．０５〜０．３重量％および／またはＺｒを０．０５〜０．２５重量％含有し、残部がＡｌ及び不可避不純物からなる組成を有するものである。
また、前記Ａｌ合金は、Ｃｕを０．４〜０．８重量％含有することとしてもよい。
【００１６】
ＳｉおよびＭｇは、Ａｌ合金中に微細なＭｇ_２Ｓｉ化合物として析出して強度を向上させる作用がある。ここで、Ｓｉの含有量が０．６重量％未満かつＭｇの含有量が０．５重量％未満になると、Ｍｇ_２Ｓｉ化合物の析出量が少なくなり、その結果、所望の強度を確保することができなくなる。また、Ｓｉの含有量が１．２重量％を越えかつＭｇの含有量が１．０％を超えると、Ｍｇ_２Ｓｉ化合物の析出量が多くなり、押出加工性および曲げ加工性が低下するとともに、衝突時の変形による割れが発生し易くなる。したがって、Ｓｉの含有量を０．６〜１．２重量％、Ｍｇの含有量を０．５〜１．０重量％とした。なお、Ｓｉの含有量の望ましい範囲は０．６５〜０．９５重量％、Ｍｇの含有量の望ましい範囲は０．５５〜０．９５重量％である。
【００１７】
Ｆｅ、Ｍｎ、Ｃｒ、Ｚｒは、Ｆｅと、Ｍｎと、Ｃｒおよび／またはＺｒとが共存した状態で微細な金属間化合物を生成し、均質化処理後にこの金属間化合物がＡｌ合金中に分散し、押出加工時の再結晶を著しく抑制するとともに繊維状組織の発達を促進する。この結果、衝突時の変形による割れを発生しにくくする作用がある。
【００１８】
ここで、Ｆｅの含有量が０．１重量％未満、Ｍｎの含有量が０．２重量％未満、Ｃｒの含有量が０．０５重量％未満、Ｚｒの含有量が０．０５重量％未満になると、その効果が不十分なものとなり、また、Ｆｅの含有量が０．４重量％を越え、Ｍｎの含有量が０．６重量％を越え、Ｃｒの含有量が０．３重量％を越え、Ｚｒの含有量が０．２５重量％を超えると、粗大な金属間化合物が生成するようになり衝突時の変形による割れが発生し易くなる。
【００１９】
したがって、Ｆｅの含有量を０．１〜０．４重量％、Ｍｎの含有量を０．２〜０．６重量％、Ｃｒの含有量を０．０５〜０．３重量％および／またはＺｒの含有量を０．０５〜０．２５重量％とした。
なお、Ｆｅ、Ｍｎ、Ｃｒ、Ｚｒの含有量の望ましい範囲は、Ｆｅ：０．１５〜０．３重量％、Ｍｎ：０．２５〜０．４５重量％、Ｃｒ：０．０７〜０．２重量％、Ｚｒ：０．０７〜０．１５重量％である。
【００２０】
ＴｉはＡｌ合金の組織を微細化し、割れを防止する作用がある。ここで、Ｔｉの含有量が０．００５重量％未満になると割れを防止するという効果が得られず、また、その含有量が０．１重量％を超えると粗大な金属間化合物を生成するようになり、その結果、衝突時の変形による割れが発生し易くなる。したがって、Ｔｉの含有量を０．００５〜０．１重量％とした。なお、Ｔｉの含有量の望ましい範囲は０．００５〜０．０５重量％である。
【００２１】
Ｃｕは、Ａｌ合金中に固溶して強度を向上させる作用がある。
ここで、Ｃｕの含有量が０．４重量％以下になると所望の強度向上効果が得られず、また、その含有量が０．８重量％を超えると曲げ加工性および耐食性が低下するようになる。
したがって、Ｃｕの含有量を０．４〜０．８重量％とした。なお、Ｃｕの含有量の望ましい範囲は、０．４５〜０．６５重量％である。
【００２２】
【発明の実施の形態】
本発明のＡｌ合金押出形材の加工方法の一実施形態について、図面に基づき説明する。
図１は本発明のＡｌ合金押出形材の加工方法の一実施形態を示す流れ図、図２は時効処理時間とＡｌ合金押出材の強度との関係を表す時効曲線を示す図である。
このＡｌ合金押出形材の加工方法では、Ｓｉを０．６〜１．２重量％、Ｍｇを０．５〜１．０重量％、Ｆｅを０．１〜０．４重量％、Ｍｎを０．２〜０．６重量％、Ｔｉを０．００５〜０．１重量％、Ｃｒを０．０５〜０．３重量％および／またはＺｒを０．０５〜０．２５重量％含有し、残部がＡｌ及び不可避不純物からなるＡｌ合金を押出成形する。
前記Ａｌ合金は、Ｃｕを０．４〜０．８重量％含有することとしてもよい。
【００２３】
このＡｌ合金を押出成形して得られたＡｌ合金押出材は、断面が多角形状の中空押出材、例えば肉厚一定の矩形状の断面を有する筒部材からなる曲げ加工用押出材である。
次いで、このＡｌ合金押出材に、図２に示すように、該Ａｌ合金の最高強度Ｈ_ｈが得られる時効処理時間（時効条件）Ｔ_ｈより手前の時効処理時間（亜時効条件）Ｔ_１で時効処理１（第１の熱処理）を行う。この時効処理時間Ｔ_１における強度Ｈ_１は最高強度Ｈ_ｈより低い。これにより、時効処理１が施されたＡｌ合金押出材では微細な析出物が発生し、伸びが良くしかも硬すぎることがなく、曲げ加工性に優れたものとなる。
【００２４】
次いで、このＡｌ合金押出材に曲げ加工を施す。
この曲げ加工方法は、Ａｌ合金押出材の一端部を押さえつつ該Ａｌ合金押出材を鉛直面内に湾曲させるもので、図３及び図４に示す様な曲げ加工装置を用いて加工される。
この曲げ加工装置１は、矩形状の断面を有する筒状のＡｌ合金押出材２を曲げ加工する中心軸Ｃを有する略車輪状の回転曲げ型３と、該回転曲げ型３の中心軸Ｃの一方側外方に設けられＡｌ合金押出材２の一方の直線部分２ａを上方から押さえる移動押さえ型４と、移動押さえ型４と同一水平線上に設けられ、Ａｌ合金押出材２を回転曲げ型３の図中略三角形状で示したクランプ部３ａとともに把持し、曲げ加工の途中でＡｌ合金押出材２の他方の直線部分２ｂに向かって図中左側から右側に移動するクランプ型（締め付け型）５とから概略構成されている。
【００２５】
ここでは、図３に示すように、前記Ａｌ合金押出材２の略中央部を回転曲げ型３のクランプ部３ａに載置し、このＡｌ合金押出材２の一方の直線部分２ａを移動押さえ型４により上方から押さえる。
そして、図４に示すように、この状態で前記回転曲げ型３をその中心軸Ｃの廻りにゆっくりと図中右回転させ、このＡｌ合金押出材２の直線部分２ｂを前記回転曲げ型３の曲率半径に合わせて鉛直面内に上向きに凸に曲げ加工する。
【００２６】
以上により、直線状に延びるＡｌ合金押出材２は、その直線部分２ａの延長線と他方の直線部分２ｂとのなす角θが所定の角度となるように曲げ加工されてＡｌ合金押出材２’とされる。
このＡｌ合金押出材２’は、伸びの値が高く複雑な曲げ形状にも曲げ加工することが可能である。また、時効硬化も進んでいることから、降伏強さも高い。また、矩形状の断面を有する筒部材であるから、筒部材の断面変形を小さく抑えることが可能である。
【００２７】
このＡｌ合金押出材２’はエネルギー吸収特性が劣っているので、図２に示すように、該Ａｌ合金の最高強度Ｈ_ｈが得られる時効処理時間Ｔ_ｈを越えた時効処理時間（過時効条件）Ｔ_２で時効処理２（第２の熱処理）を行う。この時効処理時間Ｔ_２における強度は、時効処理時間Ｔ_１における強度Ｈ_１にほぼ等しく最高強度Ｈ_ｈよりは低い。これにより、この時効処理２が施されたＡｌ合金押出材では、析出物が粗大化することで強度は若干低下するもののエネルギー吸収特性を付与することが可能になる。
【００２８】
ここで、本実施形態のＡｌ合金押出形材の加工方法の実施例について説明する。
［実施例］
まず、組成の異なる２種類のＡｌ合金を用意した。ここでは、Ａ合金（Ｓｉ：０．９重量％、Ｍｇ：０．９５重量％、Ｆｅ：０．３重量％、Ｍｎ：０．４重量％、Ｔｉ：０．０１重量％、Ｚｒ：０．１０重量％含有し、残部がＡｌ及び不可避不純物からなるＡｌ合金）及びＢ合金（Ｓｉ：０．８５重量％、Ｍｇ：０．８重量％、Ｃｕ：０．６重量％、Ｆｅ：０．２５重量％、Ｍｎ：０．４重量％、Ｔｉ：０．０７重量％、Ｚｒ：０．１２重量％含有し、残部がＡｌ及び不可避不純物からなるＡｌ合金）の２種類とした。
【００２９】
次いで、このＡ合金及びＢ合金に対して表１に示す製造工程により押出成形、熱処理（時効処理１、時効処理２、時効処理３のいずれか１種または２種）及び曲げ加工を行い、試料Ｎｏ．１〜７の押出形材製の部材とした。ここでは、試料Ｎｏ．１、２が本実施例、試料３〜７が比較例である。
時効処理１〜３の条件は、時効処理１：１５０℃×１２時間、時効処理２：２０５℃×６時間、時効処理３：１８０℃×７時間である。
また、押出成形の条件を、押出温度：５００℃、押出速度：７ｍ／ｍｉｎ、冷却：水冷とし、矩形断面の外形寸法が５０×７５ｍｍ、肉厚が２ｍｍの中空角パイプ状に押出成形し押出材とした。なお、時効処理３は、Ａ合金の最高強度Ｈ_ｈが得られる時効処理時間Ｔ_ｈで時効処理を行ったものである。次いで、軸方向に荷重を負荷する圧縮試験を行い、圧潰特性評価を行った。その結果を表１に示す。
【００３０】
【表１】

【００３１】
表１に示した本実施例の押出形材である試料１、２は、曲げ加工時に断面変形や、割れが少なく、加工性が良好であった。また、圧縮試験においても割れが発生することなくアコ−デオン状に圧縮変形し、エネルギ−吸収特性も優れていることが明かであった。
これに対し、曲げ加工の後工程で時効処理１または時効処理２を行った試料（Ｎｏ．３、４）では、曲げ加工時の変形が大きく、圧縮試験においてもアコ−デオン状に圧縮変形する前に割れてしまう（破壊）か、アコ−デオン状に圧縮変形はするが部分的に割れが認められた（やや良）。
【００３２】
また、曲げ加工の前工程で時効処理１を後工程で時効処理３を行った試料（Ｎｏ．５）では、加工性は良好であったが、圧縮試験ではアコ−デオン状に圧縮変形する前に割れてしまった（破壊）。
また、曲げ加工の前工程で時効処理１を行った試料（Ｎｏ．６）では、加工性は良好であったが、圧縮試験ではアコ−デオン状に圧縮変形する前に割れてしまった（破壊）。
また、曲げ加工の前工程で時効処理２を行った試料（Ｎｏ．７）では、曲げ加工時に割れが生じてしまった（割れ）。
【００３３】
以上説明したように、本発明の一実施形態のＡｌ合金押出形材の加工方法によれば、Ｓｉを０．６〜１．２重量％、Ｍｇを０．５〜１．０重量％、Ｆｅを０．１〜０．４重量％、Ｍｎを０．２〜０．６重量％、Ｔｉを０．００５〜０．１重量％、Ｃｒを０．０５〜０．３重量％および／またはＺｒを０．０５〜０．２５重量％含有し、残部がＡｌ及び不可避不純物からなるＡｌ合金（Ｃｕを０．４〜０．８重量％含有してもよい）を押出成形し、得られたＡｌ合金押出材に、最高強度Ｈ_ｈが得られる時効処理時間Ｔ_ｈより手前の時効処理時間Ｔ_１で時効処理１を行うので、微細な析出物が発生することで伸びが良くしかも硬すぎることがなく、その結果、曲げ加工性を高めることができる。
【００３４】
また、このＡｌ合金押出材に曲げ加工を行うので、伸びの値が高く複雑な曲げ形状にも曲げ加工することができる。したがって、中空部の変形を小さく抑えることができ、押出材の断面形状によっては、従来のような中子を省略することができ、金型のコストを削減することができる。しかも、時効硬化が進んでいることから、降伏強さを高めることができる。
【００３５】
また、曲げ加工を施したＡｌ合金押出材に、最高強度Ｈ_ｈが得られる時効処理時間Ｔ_ｈを越えた時効処理時間Ｔ_２で時効処理２を行うので、析出物が粗大化することで、高強度でありながら低強度合金と同様の圧縮荷重時の変形挙動とすることができ、エネルギー吸収特性を高めることができる。
【００３６】
以上、本発明のＡｌ合金押出形材の一実施形態について図面に基づき説明してきたが、具体的な構成は本実施形態に限定されるものではなく、本発明の要旨を逸脱しない範囲で設計の変更等が可能である。例えば、Ａｌ合金の組成は、上記実施例に限定されることなく、上述した組成の範囲で必要に応じて変更することができる。
【００３７】
【発明の効果】
以上説明した様に、本発明のＡｌ合金押出形材の加工方法によれば、Ａｌ合金を押出成形し、得られたＡｌ合金押出材に該Ａｌ合金の最高強度が得られる時効条件より手前の時効条件で第１の熱処理を行うので、微細な析出物が発生することで、伸びが良くしかも硬すぎることがなく、その結果、曲げ加工性を高めることができる。
また、第１の熱処理を行ったＡｌ合金押出材に曲げ加工を行うので、伸びの値が高く複雑な曲げ形状にも曲げ加工することができる。しかも、時効硬化を進めることができるので、降伏強さを高めることができる。
【００３８】
また、このＡｌ合金押出材に、前記Ａｌ合金の最高強度が得られる時効条件を越えた時効条件で第２の熱処理を行うので、析出物が粗大化することで、高強度でありながら低強度合金と同様の圧縮荷重時の変形挙動とすることができ、エネルギー吸収特性を高めることができる。
【００３９】
以上により、曲げ加工性及びエネルギー吸収特性に優れたＡｌ合金押出形材を製造することのできるＡｌ合金押出形材の加工方法を提供することができる。
【図面の簡単な説明】
【図１】本発明のＡｌ合金押出形材の加工方法の一実施形態を示す流れ図である。
【図２】時効処理時間とＡｌ合金押出材の強度との関係を表す時効曲線を示す図である。
【図３】本発明のＡｌ合金押出材に曲げ加工を施すための曲げ加工装置の概略構成を示す正面図である。
【図４】曲げ加工装置の一動作を示す正面図である。
【符号の説明】
１曲げ加工装置
２、２’ Ａｌ合金押出材
２ａ、２ｂ直線部分
３回転曲げ型
３ａクランプ部
４移動押さえ型
５クランプ型（締め付け型）
Ｃ中心軸
θ 角[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method of processing an extruded Al alloy material, and particularly to a method of manufacturing an extruded Al alloy material having excellent energy absorption characteristics, such as a side member constituting an aluminum body structure having a space frame structure. The present invention relates to a preferred method of processing an extruded aluminum alloy.
[0002]
[Prior art]
The side members of the vehicle are buckled and deformed in an accordion-like manner at the time of a collision in the front engine portion and the rear trunk portion of the vehicle, thereby absorbing the impact energy at the time of the collision, thereby improving the safety of the occupant. It is a member that has the function of ensuring the performance.
Examples of the side member include a front side member extending rearward from a lower portion of an engine room in front of a vehicle body and connected to a structural member on a front floor of a passenger compartment, a rear side member extending rearward from a structural member on a rear floor of a passenger compartment and reaching a lower portion of a trunk room. There is.
[0003]
As the conventional side member, a tubular member having a rectangular cross section formed by subjecting a cold-rolled steel sheet to press forming and joining using a spot welding or the like is used.
By the way, in recent years, due to environmental problems such as global warming, there has been a strong demand for automobiles to be lighter for the purpose of reducing exhaust gas and improving fuel efficiency. As part of this weight reduction, instead of using steel plates and steel pipes, In addition, a light alloy extruded material mainly composed of a light metal such as Al or Ti capable of integrally producing a structure having a complicated shape is being studied.
At present, Al-Mg-Si-based Al alloys such as JIS6N01 alloy having a good balance of extrudability, mechanical properties, corrosion resistance and the like are used as light alloys suitable for such extruded shapes.
[0004]
For example, in order to manufacture a member constituting an aluminum body structure having a space frame structure, such as a side member, an aluminum alloy is first extruded into an aluminum alloy extruded material having various cross-sectional shapes. Next, the aluminum alloy extruded material is subjected to age hardening treatment under aging conditions at which the maximum strength of the aluminum alloy is obtained, and thereafter, bending is performed. Next, a joining process such as welding is performed to obtain an Al body structural member (Step A).
In addition, the aluminum alloy extruded material is bent in the same manner as the above-described step A except that the aluminum alloy extruded material is bent and then subjected to an age hardening treatment under aging conditions at which the maximum strength of the aluminum alloy is obtained. You can also get
[0005]
[Problems to be solved by the invention]
By the way, in the members constituting the above-described conventional Al body structure, in particular, in the side member which buckles and deforms in an accordion shape at the time of collision and absorbs energy applied from the front-rear direction, the bending workability during the manufacturing process is low. At the same time, it is required to have a function of absorbing the energy at the time of collision sufficiently by buckling deformation in an accordion shape and minimizing damage to occupants.
[0006]
In the conventional process A, since the aluminum alloy extruded material is subjected to the age hardening treatment and then subjected to the bending process, the extruded material may be cracked during the bending process or may be cracked when the axial compression load is applied. There is a problem that there is.
Further, in the conventional B process, since the age hardening treatment is performed after the bending process is performed on the Al alloy extruded material, there is a problem that a cross-sectional deformation may increase during the bending process of the extruded material. .
As described above, it is difficult to achieve both the bending workability and the energy absorption property in both the steps A and B described above, and there is a problem that either one is sacrificed.
[0007]
The present invention has been made in view of the above circumstances, and provides a method for processing an Al alloy extruded profile capable of producing an Al alloy extruded profile excellent in bending workability and energy absorption characteristics. Aim.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the present inventors have conducted various experiments to clarify the effects of the manufacturing process on the bending workability and energy absorption characteristics of an extruded Al alloy, and as a result, the composition according to the present invention It has been found that by sequentially performing the first heat treatment, the bending process, and the second heat treatment on the Al alloy extruded material, an Al alloy extruded material excellent in bending workability and energy absorption characteristics can be obtained.
[0009]
The present invention is based on the above findings, and the method for processing an Al alloy extruded shape according to claim 1 comprises 0.6 to 1.2% by weight of Si and 0.5 to 1.0% by weight of Mg. 0.1 to 0.4% by weight of Fe, 0.2 to 0.6% by weight of Mn, 0.005 to 0.1% by weight of Ti, 0.05 to 0.3% by weight of Cr and / or Alternatively, an Al alloy containing 0.05 to 0.25% by weight of Zr and the remainder consisting of Al and inevitable impurities is extruded, and the obtained Al alloy extruded material is kept at 120 to 180 ° C. for 1 to 24 hours. A first heat treatment is performed under aging conditions, and then a bending process is performed. Thereafter, a second heat treatment is performed at a temperature equal to or higher than the first heat treatment and at an overaging condition of holding at 150 to 220 ° C. for 1 to 24 hours. It is characterized by:
[0010]
According to a second aspect of the present invention, there is provided a method for processing an extruded Al alloy material according to the first aspect, wherein the Al alloy contains 0.4 to 0.8% by weight of Cu. Features.
[0011]
According to a third aspect of the present invention, there is provided a method for processing an Al alloy extruded section, wherein the extruded section comprises a hollow extruded section having a polygonal cross section. And
[0013]
In the method for processing an extruded Al alloy material according to the present invention, an Al alloy is extruded, and the obtained Al alloy extruded material is subjected to a first heat treatment under an aging condition prior to an aging condition at which the highest strength of the Al alloy is obtained. By performing this, the Al alloy extruded material that has been subjected to the first heat treatment has excellent elongation and is not too hard due to generation of fine precipitates, and has excellent bending workability. Next, by performing bending, it is possible to perform bending even in a complicated bending shape having a high elongation value. In addition, since age hardening is progressing, the yield strength is high. For example, when the Al alloy extruded material to be bent has a hollow portion, the cross-sectional deformation of the hollow portion can be reduced.
[0014]
Since the aluminum alloy extruded material subjected to the bending process has inferior energy absorption characteristics, the second heat treatment is performed under the aging condition exceeding the aging condition at which the maximum strength of the Al alloy is obtained. In the Al alloy extruded material that has been subjected to the heat treatment of 2, the coarsening of the precipitate enables deformation behavior under a compressive load similar to that of a low-strength alloy while having a high strength, and improves energy absorption characteristics. Will be possible.
The conditions of the first and second heat treatments vary depending on the alloy composition. In the case of the Al alloy according to the present invention, the first heat treatment is performed at a temperature in the range of 120 to 180 ° C., the holding time is 1 to 24 hours, and The second heat treatment may be performed at a temperature equal to or higher than the first heat treatment, in a range of 150 to 220 ° C., and for a holding time of 1 to 24 hours.
[0015]
Next, the reason for limiting the composition of the Al alloy according to the present invention will be described.
The Al alloy according to the present invention contains 0.6 to 1.2% by weight of Si, 0.5 to 1.0% by weight of Mg, 0.1 to 0.4% by weight of Fe, and 0.2 to 0.2% of Mn. 0.6% by weight, 0.005 to 0.1% by weight of Ti, 0.05 to 0.3% by weight of Cr and / or 0.05 to 0.25% by weight of Zr, with the balance being Al and It has a composition consisting of unavoidable impurities.
Further, the Al alloy may contain 0.4 to 0.8% by weight of Cu.
[0016]
Si and Mg have a function of improving strength by precipitating as a fine Mg ₂ Si compound in the Al alloy. Here, when the content of Si is less than 0.6% by weight and the content of Mg is less than 0.5% by weight, the precipitation amount of the Mg ₂ Si compound is reduced, and as a result, desired strength is secured. Can not be done. On the other hand, when the content of Si exceeds 1.2% by weight and the content of Mg exceeds 1.0%, the precipitation amount of the Mg ₂ Si compound increases, and the extrusion processability and bending processability decrease. In addition, cracks due to deformation at the time of collision easily occur. Therefore, the content of Si was set to 0.6 to 1.2% by weight, and the content of Mg was set to 0.5 to 1.0% by weight. The preferable range of the Si content is 0.65 to 0.95% by weight, and the preferable range of the Mg content is 0.55 to 0.95% by weight.
[0017]
Fe, Mn, Cr, and Zr generate fine intermetallic compounds in a state where Fe, Mn, Cr, and / or Zr coexist, and after the homogenization treatment, the intermetallic compounds are dispersed in the Al alloy. Remarkably suppresses recrystallization during extrusion and promotes the development of a fibrous structure. As a result, there is an effect that cracks due to deformation at the time of collision hardly occur.
[0018]
Here, the Fe content is less than 0.1% by weight, the Mn content is less than 0.2% by weight, the Cr content is less than 0.05% by weight, and the Zr content is less than 0.05% by weight. , The effect becomes insufficient, the Fe content exceeds 0.4% by weight, the Mn content exceeds 0.6% by weight, and the Cr content is 0.3% by weight. When the Zr content exceeds 0.25% by weight, a coarse intermetallic compound is generated, and cracks due to deformation at the time of collision tend to occur.
[0019]
Therefore, the content of Fe is 0.1 to 0.4% by weight, the content of Mn is 0.2 to 0.6% by weight, the content of Cr is 0.05 to 0.3% by weight and / or Zr. Was 0.05 to 0.25% by weight.
The desirable ranges of the contents of Fe, Mn, Cr and Zr are as follows: Fe: 0.15 to 0.3% by weight, Mn: 0.25 to 0.45% by weight, Cr: 0.07 to 0.2% % By weight, Zr: 0.07 to 0.15% by weight.
[0020]
Ti has the effect of refining the structure of the Al alloy and preventing cracking. Here, if the content of Ti is less than 0.005% by weight, the effect of preventing cracking cannot be obtained, and if the content exceeds 0.1% by weight, a coarse intermetallic compound is generated. As a result, cracks due to deformation at the time of collision tend to occur. Therefore, the content of Ti is set to 0.005 to 0.1% by weight. The desirable range of the content of Ti is 0.005 to 0.05% by weight.
[0021]
Cu has the effect of improving the strength by forming a solid solution in the Al alloy.
Here, if the Cu content is 0.4% by weight or less, a desired strength improving effect cannot be obtained, and if the Cu content exceeds 0.8% by weight, bending workability and corrosion resistance are reduced. Become.
Therefore, the content of Cu is set to 0.4 to 0.8% by weight. Note that a desirable range of the Cu content is 0.45 to 0.65% by weight.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of a method for processing an extruded aluminum alloy according to the present invention will be described with reference to the drawings.
FIG. 1 is a flow chart showing one embodiment of a method for processing an extruded Al alloy material according to the present invention, and FIG. 2 is a diagram showing an aging curve showing the relationship between the aging treatment time and the strength of the extruded Al alloy material.
In this method for processing an extruded aluminum alloy material, 0.6 to 1.2% by weight of Si, 0.5 to 1.0% by weight of Mg, 0.1 to 0.4% by weight of Fe, 0.2 to 0.6% by weight, 0.005 to 0.1% by weight of Ti, 0.05 to 0.3% by weight of Cr and / or 0.05 to 0.25% by weight of Zr, with the balance being Extrudes an Al alloy composed of Al and inevitable impurities.
The Al alloy may contain 0.4 to 0.8% by weight of Cu.
[0023]
An Al alloy extruded material obtained by extrusion-molding this Al alloy is a hollow extruded material having a polygonal cross section, for example, a bending extruded material formed of a cylindrical member having a rectangular cross section with a constant thickness.
Then, the Al alloy extruded material, as shown in FIG. 2, at the highest intensity H _h is aging time obtained (aging conditions) T _h than before the aging time (nitrous aging conditions) T ₁ of the Al alloy Aging treatment 1 (first heat treatment) is performed. Strength _{H 1} in this aging time _{T 1} is lower than the highest intensity _{H h.} As a result, the Al alloy extruded material subjected to the aging treatment 1 generates fine precipitates, has good elongation and is not too hard, and has excellent bending workability.
[0024]
Next, this Al alloy extruded material is subjected to bending.
In this bending method, the extruded Al alloy is bent into a vertical plane while holding one end of the extruded Al alloy, and is processed using a bending apparatus as shown in FIGS.
The bending apparatus 1 includes a substantially wheel-shaped rotary bending die 3 having a central axis C for bending a cylindrical Al alloy extruded material 2 having a rectangular cross section, and a central axis C of the rotary bending die 3. A moving pressing die 4 provided on one side outward and pressing one linear portion 2a of the Al alloy extruded material 2 from above, and a moving pressing die 4 provided on the same horizontal line as the moving pressing die 4 And a clamp type (clamping type) 5 which is gripped together with the clamp portion 3a shown in a substantially triangular shape in the figure and moves from the left side to the right side in the figure toward the other linear portion 2b of the Al alloy extruded material 2 during the bending process. It is roughly constituted from.
[0025]
Here, as shown in FIG. 3, a substantially central portion of the Al alloy extruded material 2 is placed on the clamp portion 3a of the rotary bending die 3, and one of the linear portions 2a of the Al alloy extruded material 2 is moved and held. 4 from above.
Then, as shown in FIG. 4, in this state, the rotary bending die 3 is slowly rotated rightward in the figure around its central axis C, and the linear portion 2 b of the Al alloy extruded material 2 is rotated by the rotary bending die 3. It is bent upward in the vertical plane to match the radius of curvature.
[0026]
As described above, the Al alloy extruded material 2 extending linearly is bent so that the angle θ between the extension of the linear portion 2a and the other linear portion 2b becomes a predetermined angle, and the Al alloy extruded material 2 ′ is formed. It is said.
The extruded Al alloy material 2 'can be bent into a complicated bent shape having a high elongation value. Further, since the age hardening is progressing, the yield strength is high. Further, since the tubular member has a rectangular cross section, it is possible to suppress the cross-sectional deformation of the tubular member to be small.
[0027]
Since the Al alloy extruded material 2 'is inferior energy absorbing characteristics, as shown in FIG. 2, the Al alloy highest intensity H _h is aging time exceeding the aging time T _h obtained in (overaging conditions ) performing an aging treatment 2 (second heat treatment) at _{T 2.} Strength in the aging time T ₂ are lower than the approximately equal maximum intensity H _h to intensity H ₁ in aging time T _1. Thus, in the Al alloy extruded material subjected to the aging treatment 2, although the strength is slightly reduced due to the coarsening of the precipitate, it is possible to impart the energy absorbing property.
[0028]
Here, an example of the processing method of the extruded Al alloy material of the present embodiment will be described.
[Example]
First, two types of Al alloys having different compositions were prepared. Here, alloy A (Si: 0.9% by weight, Mg: 0.95% by weight, Fe: 0.3% by weight, Mn: 0.4% by weight, Ti: 0.01% by weight, Zr: 0. Al alloy containing 10% by weight, the balance being Al and unavoidable impurities) and B alloy (Si: 0.85% by weight, Mg: 0.8% by weight, Cu: 0.6% by weight, Fe: 0.25%) %, Mn: 0.4% by weight, Ti: 0.07% by weight, Zr: 0.12% by weight, with the balance being Al and Al and inevitable impurities.
[0029]
Next, the A alloy and the B alloy were subjected to extrusion molding, heat treatment (one or two of aging treatment 1, aging treatment 2, and aging treatment 3) and bending according to the manufacturing process shown in Table 1, and the sample was subjected to a bending process. No. 1 to 7 were made of extruded members. Here, the sample No. 1 and 2 are the present example, and samples 3 to 7 are comparative examples.
The conditions of the aging treatments 1 to 3 are aging treatment 1: 150 ° C. × 12 hours, aging treatment 2: 205 ° C. × 6 hours, and aging treatment 3: 180 ° C. × 7 hours.
Extrusion molding conditions were as follows: extrusion temperature: 500 ° C., extrusion speed: 7 m / min, cooling: water cooling, extrusion molding into a hollow square pipe having a rectangular cross section of 50 × 75 mm and a wall thickness of 2 mm. Material. Note that the aging process 3 are those subjected to aging treatment at the highest intensity H _h is obtained aging time T _h of A alloy. Next, a compression test in which a load was applied in the axial direction was performed, and crush characteristics were evaluated. Table 1 shows the results.
[0030]
[Table 1]

[0031]
Samples 1 and 2, which are the extruded members of the present example shown in Table 1, had little cross-sectional deformation and cracking during bending, and had good workability. In the compression test, it was also apparent that the sample was compressed and deformed into an accordion shape without cracking, and that it had excellent energy absorption characteristics.
On the other hand, in the samples (Nos. 3 and 4) subjected to the aging treatment 1 or the aging treatment 2 in the post-process of the bending, the deformation at the time of the bending is large, and the compression deformation is performed in an accordion shape even in the compression test. It cracked before (destruction) or was compressed and deformed in an accordion-like manner, but was partially cracked (somewhat good).
[0032]
In the sample (No. 5), which was subjected to the aging treatment 1 in the pre-process of the bending process and the aging treatment 3 in the post-process, the workability was good, but in the compression test, before the sample was compressed and deformed into an accordion shape. Cracked (destruction).
In the sample (No. 6) subjected to the aging treatment 1 in the previous step of the bending, the workability was good, but in the compression test, the sample was broken before accordion-like compression deformation (breakage). ).
Further, in the sample (No. 7) subjected to the aging treatment 2 in the previous step of the bending, a crack was generated during the bending (crack).
[0033]
As described above, according to the method for processing an extruded aluminum alloy according to one embodiment of the present invention, 0.6 to 1.2% by weight of Si, 0.5 to 1.0% by weight of Mg, 0.1 to 0.4% by weight, Mn 0.2 to 0.6% by weight, Ti 0.005 to 0.1% by weight, Cr 0.05 to 0.3% by weight and / or Zr Alloy containing 0.05 to 0.25% by weight and the balance being Al and unavoidable impurities (Cu may be contained at 0.4 to 0.8% by weight) is extruded to obtain an Al alloy. alloy extruded material, since the aging treatment 1 at maximum intensity H _h aging time is obtained T _h than before the aging time T _1, it extends well yet too hard by fine precipitates occurs However, as a result, bending workability can be improved.
[0034]
In addition, since the Al alloy extruded material is bent, it can be bent into a complicated bent shape having a high elongation value. Therefore, the deformation of the hollow portion can be suppressed small, and depending on the cross-sectional shape of the extruded material, the conventional core can be omitted, and the cost of the mold can be reduced. In addition, since the age hardening is advanced, the yield strength can be increased.
[0035]
Further, the Al alloy extruded subjected to bending, maximum strength because H _h is at aging time T ₂ to aging time exceeds T _h obtained performing aging treatment 2, precipitates that coarsen, Despite having high strength, the same deformation behavior under a compressive load as that of a low-strength alloy can be obtained, and the energy absorption characteristics can be enhanced.
[0036]
As described above, one embodiment of the extruded aluminum alloy according to the present invention has been described with reference to the drawings. However, the specific configuration is not limited to this embodiment, and the design of the extruded aluminum alloy is not limited to the scope of the present invention. Changes and the like are possible. For example, the composition of the Al alloy is not limited to the above example, and can be changed as needed within the above-described composition range.
[0037]
【The invention's effect】
As described above, according to the method for processing an extruded Al alloy material of the present invention, an Al alloy is extruded, and the obtained Al alloy extruded material has a higher aging condition than the aging condition at which the highest strength of the Al alloy is obtained. Since the first heat treatment is performed under the aging condition, fine precipitates are generated, so that the elongation is good and the hardness is not too hard. As a result, the bending workability can be improved.
In addition, since the Al alloy extruded material that has been subjected to the first heat treatment is subjected to bending, it can be bent into a complicated bent shape having a high elongation value. Moreover, since age hardening can be advanced, the yield strength can be increased.
[0038]
Further, since the Al alloy extruded material is subjected to the second heat treatment under the aging condition exceeding the aging condition at which the maximum strength of the Al alloy is obtained, the precipitates are coarsened, so that the high strength and the low strength are obtained. Deformation behavior under a compressive load similar to that of an alloy can be obtained, and energy absorption characteristics can be enhanced.
[0039]
As described above, it is possible to provide a method of processing an Al alloy extruded shape capable of manufacturing an Al alloy extruded shape excellent in bending workability and energy absorption characteristics.
[Brief description of the drawings]
FIG. 1 is a flowchart showing an embodiment of a method for processing an extruded Al alloy material according to the present invention.
FIG. 2 is a diagram showing an aging curve showing a relationship between aging treatment time and strength of an extruded Al alloy.
FIG. 3 is a front view showing a schematic configuration of a bending apparatus for bending an Al alloy extruded material of the present invention.
FIG. 4 is a front view showing one operation of the bending apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Bending apparatus 2, 2 'Al alloy extruded

material

2a, 2b Straight part 3 Rotating bending type 3a Clamp part 4 Moving holding type 5 Clamp type (clamp type)
C central axis θ angle

Claims

0.6-1.2% by weight of Si, 0.5-1.0% by weight of Mg, 0.1-0.4% by weight of Fe, 0.2-0.6% by weight of Mn, Ti Extrusion of an Al alloy containing 0.005 to 0.1% by weight, 0.05 to 0.3% by weight of Cr and / or 0.05 to 0.25% by weight of Zr, with the balance being Al and unavoidable impurities Formed, the obtained Al alloy extruded material is subjected to a first heat treatment under a sub-aging condition of holding at 120 to 180 ° C. for 1 to 24 hours, then subjected to bending, and then at a temperature equal to or higher than the first heat treatment. A method for processing an extruded Al alloy material, wherein the second heat treatment is performed under overaging conditions of holding at 150 to 220 ° C for 1 to 24 hours .

The method according to claim 1, wherein the Al alloy contains 0.4 to 0.8% by weight of Cu.

The method according to claim 1 or 2, wherein the extruded material is a hollow extruded material having a polygonal cross section.