JP4296583B2

JP4296583B2 - Aluminum alloy hollow member with excellent hydroforming properties

Info

Publication number: JP4296583B2
Application number: JP2000290502A
Authority: JP
Inventors: 紘一大堀; 久男谷川; 成幸中川; 聡真嶋
Original assignee: Mitsubishi Aluminum Co Ltd; Nissan Motor Co Ltd
Current assignee: Mitsubishi Aluminum Co Ltd; Nissan Motor Co Ltd
Priority date: 2000-09-25
Filing date: 2000-09-25
Publication date: 2009-07-15
Anticipated expiration: 2020-09-25
Also published as: JP2002097541A

Description

【０００１】
【産業上の利用分野】
この発明は、自動車、車両、あるいは建築部材のフレームや接合部材などの成形に好適なハイドロフォーミング性に優れたアルミニウム合金中空部材およびその製造方法に関するものである。
【０００２】
【従来の技術】
近年、地球の温暖化などの環境問題から、排ガス低減や燃費向上などのために自動車の軽量化が強く要請されている。車体の軽量化の手法としては、従来主として使用されてきた鋼板をアルミ化する材料置換が最も効果的であるため、アルミニウム合金材、特に、複雑形状の構造体を一体で成形できるアルミニウム合金押出し材または引き抜き材の使用が増加している。例えば、アルミニウム合金インゴットを押出しまたはさらに引抜き加工して得られた中空部材を所定の形状に一体成形し、これらを接合して車体骨格を構成し、それに外板パネルを組み付けるアルミスペースフレーム車体が相次いで商品化されている。
これらアルミニウム合金押出し中空部材を所定の形状に一体成形するための加工技術として、最近、ハイドロフォーミング技術が注目されている。ハイドロフォーミングは管材の型の中での液圧による拡管成形が主体となる加工法で、同一部材の断面形状を自由に変更することができる。この加工法においては、例えば、液圧成形に先立ち、予備成形において管材の可動型を用いた複雑断面形状への成形と曲げ加工を行うことも一般的に成されている。また、液圧成形においては、多くの場合、管軸方向の押し込みによって変形部分への材料流入を助長することが行われている。
【０００３】
かかるハイドロフォーミングを行なうためのアルミニウム合金中空部材として、現在のところ６０６３合金、６Ｎ０１合金、６０６１合金などのＡｌ−Ｍｇ−Ｓｉ系合金を押出し加工することにより得られた中空部材が主に使用されている。この中空部材を予備成形により所定の断面形状に加工した後、ハイドロフォーミングが行われている。また、自由な断面形状が成形可能な押出し形材の特徴を生かし、あらかじめ管状以外の所定の断面形状に押出し成形された中空形材を素材として、この形材から直接、または適宜な予備成形を行った後、ハイドロフォーミングが行われている。
【０００４】
【発明が解決しようとする課題】
ところで、Ａｌ−Ｍｇ−Ｓｉ系合金、例えば、６０６３合金、６Ｎ０１合金、６０６１合金などにおいては、強度の高いＴ５あるいはＴ６材はハイドロフォーミング性に劣っているため、拡管率の高いＯ材を用いる必要があった（特開平１０−４６２８０号参照）。
しかしながら、Ｏ材を用いて成形した場合は、部品に必要な強度を得るために、成形後に溶体化・焼入れ、時効からなる熱処理を施さなければならず、熱応力や焼入れ歪みによる変形が避けがたいという問題があった。
また、この精度低下を避けるためにＯ材のまま用いた場合は、強度が低いために板厚を厚くする必要があり、アルミニウム合金による軽量化効果が低くなってしまうという問題点があった。
この発明は、かかる問題点に鑑みてなされたものであって、部品に必要とされる強度と良好なハイドロフォーミング性とを兼ね備えたアルミニウム合金中空部材を提供することを目的とするものである。
【０００５】
【課題を解決するための手段】
本発明者等は、上述のような観点から、ハイドロフォーミングして得られた成形部品の強度が十分にありかつハイドロフォーミング性に優れた中空部材を得るべく研究を行なった結果、下記の（イ）〜（ハ）記載の成分組成を有するＡｌ合金からなるＡｌ合金鋳塊を温度：４６０〜５６０℃に加熱した後、、押出し加工し、次いで５０℃／秒以上の冷却速度で冷却し、その後、必要に応じて冷間引抜き加工を施した後、１５０〜１９０℃の温度で０．５〜８時間加熱する時効処理を施すと、耐力：１６０〜２５０ＭＰａ、全伸び：２２％以上、全伸びに占める局部伸びの割合が１７％以上を有するアルミニウム合金中空部材が得られ、このアルミニウム合金中空部材はハイドロフォーミング性に優れる、という研究結果が得られたのである。
（イ）質量％で（以下％は質量％を示す）ＳｉおよびＭｇを、Ｓｉ：０．７５〜１．４％、Ｍｇ：０．３０〜０．７５％、０．９５％≦１．７３Ｓｉ−Ｍｇ≦１．８５％なる関係を満たすように含有し、さらに、ＭｎおよびＶを、Ｍｎ：０．０２〜０．２０％、Ｖ：０．０５〜０．２５％、０．１２％≦Ｍｎ＋Ｖ≦０．３０％なる関係を満たすように含有し、さらにＴｉ：０．００５〜０．１％、Ｂ：０．０００１〜０．００４％を含有し、残りがＡｌと不可避不純物からなる組成を有するＡｌ合金からなるアルミニウム合金中空部材、
（ロ）前記（イ）記載のＡｌ合金に、さらにＣｕ：０．０３〜０．４％を含有したＡｌ合金からなる中空部材、
【０００６】
この発明は、上記の研究結果にもとづいてなされたものであって、
（１）ＳｉおよびＭｇを、Ｓｉ：０．７５〜１．４％、Ｍｇ：０．３０〜０．７５％、０．９５％≦１．７３Ｓｉ−Ｍｇ≦１．８５％なる関係を満たすように含有し、さらに、ＭｎおよびＶを、Ｍｎ：０．０２〜０．２０％、Ｖ：０．０５〜０．２５％、０．１２％≦Ｍｎ＋Ｖ≦０．３０％なる関係を満たすように含有し、さらにＴｉ：０．００５〜０．１％、Ｂ：０．０００１〜０．００４％を含有し、残りがＡｌと不可避不純物からなる組成を有するＡｌ合金からなるアルミニウム合金中空部材であって、
前記アルミニウム合金中空部材は、耐力：１６０〜２５０ＭＰａ、全伸び：２２％以上、全伸びに占める局部伸びの割合が１７％以上であるハイドロフォーミング性に優れたアルミニウム合金中空部材、
（２）ＳｉおよびＭｇを、Ｓｉ：０．７５〜１．４％、Ｍｇ：０．３０〜０．７５％、０．９５％≦１．７３Ｓｉ−Ｍｇ≦１．８５％なる関係を満たすように含有し、さらに、ＭｎおよびＶを、Ｍｎ：０．０２〜０．２０％、Ｖ：０．０５〜０．２５％、０．１２％≦Ｍｎ＋Ｖ≦０．３０％なる関係を満たすように含有し、
さらにＴｉ：０．００５〜０．１％、Ｂ：０．０００１〜０．００４％を含有し、さらにＣｕ：０．０３〜０．４％を含有し、残りがＡｌと不可避不純物からなる組成を有するＡｌ合金からなるアルミニウム合金中空部材であって、
前記アルミニウム合金中空部材は、耐力：１６０〜２５０ＭＰａ、全伸び：２２％以上、全伸びに占める局部伸びの割合が１７％以上であるハイドロフォーミング性に優れたアルミニウム合金中空部材、
（３）前記（１）〜（２）に記載の組成を有するＡｌ合金鋳塊を温度：４６０〜５６０℃に加熱した後、押出し加工し、次いで５０℃／秒以上の冷却速度で冷却し、その後、１５０〜１９０℃の温度で０．５〜８時間加熱する時効処理を施すハイドロフォーミング性に優れたアルミニウム合金中空部材の製造方法、
（４）前記（１）〜（２）に記載の組成を有するＡｌ合金鋳塊を温度：４６０〜５６０℃に加熱した後、押出し加工し、次いで５０℃／秒以上の冷却速度で冷却し、その後、冷間引抜き加工を施した後、１５０〜１９０℃の温度で０．５〜８時間加熱する時効処理を施すハイドロフォーミング性に優れたアルミニウム合金中空部材の製造方法、
に特徴を有するものである。
【０００７】
ここで「局部伸び」とは、荷重−伸び曲線における最高荷重点から破断までの伸びの値を示し、全伸びに占める局部伸びの割合とは局部伸びの値を全伸びで割った値である。
さらに、ここで冷間引抜き加工とは、押出材をダイスを通してその断面を減少することにより所定の寸法精度を得るための冷間での加工である。
【０００８】
前記（１）または（２）記載のハイドロフォーミング性に優れたアルミニウム合金中空部材の製造方法を一層具体的に説明する。
前記（１）または（２）記載の成分組成を有するビレットをＤＣ鋳造法により作製し、このビレットを温度：５１０〜５８０℃の範囲内の温度で４〜１６時間保持することにより均質化熱処理し、均質化熱処理したビレットを温度：４６０〜５６０℃の範囲内の温度で押出し加工した後、ただちに５０℃／秒以上の冷却速度で冷却する。冷却して得られた中空部材は、必要に応じて冷間引抜き加工を施しても良い。このようにして得られたアルミニウム合金中空部材は、その後、温度：１５０〜１９０℃に０．５〜８時間保持の条件で時効処理すると、耐力：１６０〜２５０ＭＰａ、、全伸び：２２％以上、全伸びに占める局部伸びの割合が１７％以上となり、かかる成分組成および機械的特性を有するアルミニウム合金中空部材はハイドロフォーミング性が良いものとなる。
【０００９】
中空部材を構成するアルミニウム合金の成分組成、機械的特性および製造条件を上記の通りに限定した理由を説明する。
Ａ．成分組成
（ａ）Ｓｉ，Ｍｇ
これら成分には、微細なＭｇ₂Ｓｉ化合物として析出して強度を向上させる作用があるが、ＳｉおよびＭｇのいずれかの含有量でもＳｉ：０．７５％未満、Ｍｇ：０．３％未満になると、生成する析出物の量が少なくなって所望の強度を確保することができず、一方、その含有量がＳｉ：１．４％およびＭｇ：０．７５％を越えるとハイドロフォーミング性、曲げ加工性、および押出しまたは引抜き加工性が低下するようになるので好ましくない。したがって、Ｓｉ：０．７５〜１．４％、Ｍｇ：０．３０〜０．７５％に定めた。ＳｉおよびＭｇの一層好ましい範囲はＳｉ：０．７〜１．２％、Ｍｇ：０．４０〜０．６０％である。
さらに、Ｓｉは、Ｍｇ₂Ｓｉの形成に必要な量よりも過剰に含有させると、Ｍｇ₂Ｓｉをより微細に析出させ、かつ過剰Ｓｉが微細な粒子として均一分散させることによって、伸びが増加し、その結果ハイドロフォーミング性が向上するようになる。しかしながら、Ｓｉが０．９５％≦１．７３Ｓｉ−Ｍｇを満足する量未満ではその効果が十分得られず、一方、１．７３Ｓｉ−Ｍｇ≦１．８５％を満足する量を超えると粒界に析出したＳｉが溶体化処理後も残存するようになって靭性が低下し、またハイドロフォーミング性及び曲げ加工性も劣化する。したがって、この発明のアルミニウム合金中空部材に含まれるＳｉおよびＭｇはＳｉ：０．７５〜１．４％、Ｍｇ：０．３０〜０．７５％であって、かつ０．９５≦１．７３Ｓｉ−Ｍｇ≦１．８５を満足することが必要である。
【００１０】
（ｂ）Ｍｎ、Ｖ
これら成分は、共にＡｌと金属間化合物を形成し、これらが再結晶の核生成サイトとなって押出し組織を微細な等軸粒状の結晶粒組織とし、それによってハイドロフォーミング性及び曲げ加工性を向上させ、特にこれら成分を複合添加することによりその効果を一層大きくさせるが、ＭｎおよびＶの含有量がＭｎ：０．０２％未満、Ｖ：０．０５％未満では所望の効果が得られず、一方、ＭｎおよびＶの含有量がＭｎ：０．２０％、Ｖ：０．２５％を越えると、押出し時の再結晶化が抑制されて繊維状組織が現れるようになり、ハイドロフォーミング性及び曲げ加工性が劣化するので好ましくない。したがって、ＭｎおよびＶの含有量はそれぞれＭｎ：０．０２〜０．２０％、Ｖ：０．０５〜０．２５％に定めた。ＭｎおよびＶは複合添加することが必要であり、その時の添加量はＭｎおよびＶの合計が０．１２％≦Ｍｎ＋Ｖ≦０．３０％の条件を満たすことが一層好ましい。したがって、ＭｎおよびＶの添加量はＭｎ：０．０２〜０．２０％、Ｖ：０．０５〜０．２５％でかつ０．１２％≦Ｍｎ＋Ｖ≦０．３０％に定めた。
【００１１】
（ｃ）Ｔｉ、Ｂ
これら成分は、鋳造組織を微細化し、鋳造割れを防止する作用があるので添加するが、ＴｉおよびＢのいずれかの含有量でもＴｉ：０．００５％未満、Ｂ：０．０００１％未満になると所望の効果が得られず、一方、ＴｉおよびＢのいずれかの含有量でもＴｉ：０．１％およびＢ：０．００４％を越えると、巨大な金属間化合物が生成するようになって靭性が低下し、またハイドロフォーミング性及び曲げ加工性が低下するので好ましくない。したがって、ＴｉおよびＢの含有量をそれぞれＴｉ：０．００５〜０．１％、Ｂ：０．０００１〜０．００４％に定めた。
【００１２】
（ｄ）Ｃｕ
Ｃｕは、素地に固溶することにより中空部材の強度を向上させる作用があるので必要に応じて添加するが、その含有量がＣｕ：０．０３％未満では所望の強度向上効果が得られず、一方、その含有量が０．４％を越えると耐食性が低下するので好ましくない。したがって、Ｃｕ：０．０３〜０．４％と定めた。
【００１３】
Ｂ．機械的特性
ハイドロフォーミングするためのアルミニウム合金中空部材は、強度を必要とするところから、耐力：１６０ＭＰａ以上あることが必要であり、さらにハイドロフォーミング性が優れていると言えるためには全伸び：２２％以上、全伸びに占める局部伸びの割合：１７％以上を有することが必要である。特に複雑な形状のハイドロフォーミング製品を精度良く成形するためには、全伸びに占める局部伸びの割合を大きくすることが必要である。しかし、前記耐力、全伸びおよび局部伸びはアルミニウム合金であるところから上限があり、耐力は２５０ＭＰａを越えることがなく、全伸びは５０％を越えることがなく、また全伸びに占める局部伸びの割合は３５％を越えることがない。
【００１４】
Ｃ．製造条件
（ｅ）押出し加工温度
押出し加工温度を４６０〜５６０℃に限定したのは、４６０℃未満で押出し加工すると温度が低すぎて溶質原子を十分に固溶し、所望の強度を得ることができないので好ましくなく、一方、５６０℃を越えた温度で押出し加工を行なうと、温度が高くなりすぎて、局部融解による割れなどの欠陥が生じるようになるので好ましくないとの理由によるものである。
【００１５】
（ｆ）冷却速度
押出し加工後の冷却速度は、５０℃／秒未満では冷却中に結晶粒界に粗大なＭｇ₂ＳｉやＳｉの析出物が生成し、成形性が劣化するので好ましくなく、したがって、５０℃／秒以上は必要である。しかし、冷却速度は１０００℃／秒を越えて早く冷却しても一層の効果が得られない。
【００１６】
（ｇ）時効処理条件
時効処理条件を１５０〜１９０℃、０．５〜８時間保持に規定したのは、１５０℃未満で０．５時間加熱しても時効処理効果が不十分で、所望の強度が得られないので好ましくなく、一方、１９０℃を越え８時間越えて加熱すると、伸びが低下し、所望の値が得られないので好ましくない理由によるものである。
【００１７】
【発明の実施の形態】
表１〜２に示される組成を有し、直径：２０４ｍｍの寸法を有するＡｌ合金ビレットを溶製し鋳造してビレットを作製し、これらビレットに温度：５４５℃で４時間保持することにより均質化処理を施し、引き続いて１６５０ｔｏｎの押出し機を用い、表３〜４に示される温度で押出し加工を行ない、その後ただちに表３〜４に示される冷却速度で冷却し、ついで表３〜４に示される温度で表３〜４に示される時間保持の時効処理を施すことにより肉厚：２．７ｍｍ、外径：４３ｍｍの寸法を有する本発明Ａｌ合金中空部材（以下、本発明中空部材という）１〜１３、比較Ａｌ合金中空部材（以下、比較中空部材という）１〜５および従来Ａｌ合金中空部材（以下、従来中空部材という）１〜３を作製した。
【００１８】
このようにして得られた本発明中空部材１〜１３、比較中空部材１〜５および従来中空部材１〜３から引張り試験片を切り出して作製し、この引張り試験片を用いて耐力を測定し、全伸びおよび全伸びに占める局部伸びの割合を測定し、その結果を表３〜４に示した。
【００１９】
さらに、本発明中空部材１〜１３、比較中空部材１〜５および従来中空部材１〜３に内圧を負荷すると共に軸方向に押し込みを行なうことにより拡管し、破断が生じたときの破断位置での周長を求め、破断までの周長変化率が１８％以上を○、１８％未満を×で示し、ハイドロフォーミング性を評価し、その結果を表３〜４に示した。
【００２０】
【表１】

【００２１】
【表２】

【００２２】
【表３】

【００２３】
【表４】

【００２４】
【発明の効果】
表１〜４に示される結果から、この発明の条件を満たす成分組成、耐力、全伸びおよび全伸びに占める局部伸びの割合を有する本発明中空部材１〜１３は、この発明の条件から外れた成分組成、耐力、全伸びおよび全伸びに占める局部伸びの割合を有する従来中空部材１〜３および比較中空部材１〜５に比べて、拡管率が優れているところから、ハイドロフォーミング性に優れていることが分かる。前述のように、この発明のアルミニウム合金中空部材は、ハイドロフォーミング性に優れているところから、軽量で精度の優れた各種部品を作製することができ、燃費の向上など自動車産業に優れた効果をもたらすものである。[0001]
[Industrial application fields]
The present invention relates to an aluminum alloy hollow member excellent in hydroforming properties suitable for molding a frame, a joining member, etc. of an automobile, a vehicle, or a building member, and a method for manufacturing the same.
[0002]
[Prior art]
In recent years, due to environmental problems such as global warming, there is a strong demand for weight reduction of automobiles in order to reduce exhaust gas and improve fuel efficiency. The most effective method for reducing the weight of the vehicle body is to replace the steel material, which has been mainly used in the past, with aluminum, so that aluminum alloy materials, especially aluminum alloy extruded materials that can be used to integrally form structures with complex shapes, are most effective. Or the use of drawing material is increasing. For example, a hollow member obtained by extruding or further drawing an aluminum alloy ingot is integrally formed into a predetermined shape, and these are joined together to form a car body skeleton, and an aluminum space frame car body is assembled with an outer panel panel. Has been commercialized.
As a processing technique for integrally forming these aluminum alloy extruded hollow members into a predetermined shape, a hydroforming technique has recently attracted attention. Hydroforming is a processing method that mainly consists of pipe expansion molding by hydraulic pressure in the mold of the pipe material, and the sectional shape of the same member can be freely changed. In this processing method, for example, prior to hydraulic forming, forming and bending into a complex cross-sectional shape using a movable mold of a pipe material is generally performed in preforming. Further, in the hydraulic forming, in many cases, material inflow to the deformed portion is promoted by pushing in the tube axis direction.
[0003]
Currently, hollow members obtained by extruding Al—Mg—Si alloys such as 6063 alloy, 6N01 alloy, and 6061 alloy are mainly used as aluminum alloy hollow members for performing such hydroforming. Yes. Hydroforming is performed after processing this hollow member into a predetermined cross-sectional shape by preforming. In addition, taking advantage of the features of extruded shapes that can be molded into a free cross-sectional shape, a hollow shape material that has been previously extruded into a predetermined cross-sectional shape other than a tubular shape is used as a raw material. After performing, hydroforming is performed.
[0004]
[Problems to be solved by the invention]
By the way, in Al-Mg-Si alloys, such as 6063 alloy, 6N01 alloy, and 6061 alloy, T5 or T6 material having high strength is inferior in hydroforming property, so it is necessary to use O material having a high tube expansion rate. (See JP 10-46280).
However, when molding using O material, in order to obtain the required strength of the part, it must be subjected to heat treatment consisting of solution treatment, quenching, and aging after molding, and deformation due to thermal stress and quenching strain can be avoided. There was a problem of wanting.
Further, when the O material is used as it is in order to avoid this decrease in accuracy, it is necessary to increase the plate thickness because the strength is low, and there is a problem that the lightening effect by the aluminum alloy is reduced.
The present invention has been made in view of such problems, and an object of the present invention is to provide an aluminum alloy hollow member having both strength required for a part and good hydroforming properties.
[0005]
[Means for Solving the Problems]
From the viewpoints described above, the present inventors have conducted research to obtain a hollow member having sufficient strength of a molded part obtained by hydroforming and excellent hydroforming properties. ) To (c) An Al alloy ingot made of an Al alloy having the component composition described above is heated to a temperature of 460 to 560 ° C., then extruded, and then cooled at a cooling rate of 50 ° C./second or more. When subjected to cold drawing as necessary, and then subjected to an aging treatment at a temperature of 150 to 190 ° C. for 0.5 to 8 hours, yield strength: 160 to 250 MPa, total elongation: 22% or more, total elongation An aluminum alloy hollow member having a local elongation ratio of 17% or more is obtained, and a research result was obtained that this aluminum alloy hollow member was excellent in hydroforming properties.
(Ii) Si and Mg in mass% (hereinafter% represents mass%), Si: 0.75-1.4%, Mg: 0.30-0.75%, 0.95% ≦ 1.73Si -Mg ≦ 1.85%, so as to satisfy the relationship, and Mn and V are further Mn: 0.02 to 0.20%, V: 0.05 to 0.25%, 0.12% ≦ A composition containing Mn + V ≦ 0.30%, further containing Ti: 0.005 to 0.1%, B: 0.0001 to 0.004%, and the remainder composed of Al and inevitable impurities. An aluminum alloy hollow member made of an Al alloy having
(B) A hollow member made of an Al alloy containing Cu: 0.03 to 0.4% in addition to the Al alloy described in (a) above,
[0006]
This invention was made based on the above research results,
(1) Si and Mg satisfy the relationship of Si: 0.75 to 1.4%, Mg: 0.30 to 0.75%, 0.95% ≦ 1.73Si-Mg ≦ 1.85% In addition, Mn and V should satisfy the relationship of Mn: 0.02 to 0.20%, V: 0.05 to 0.25%, 0.12% ≦ Mn + V ≦ 0.30% An aluminum alloy hollow member made of an Al alloy having a composition further containing Ti: 0.005 to 0.1%, B: 0.0001 to 0.004%, and the remainder comprising Al and inevitable impurities. And
The aluminum alloy hollow member has a proof stress: 160 to 250 MPa, a total elongation: 22% or more, and an aluminum alloy hollow member excellent in hydroforming properties in which the ratio of local elongation in the total elongation is 17% or more,
(2) Si and Mg should satisfy the relationship of Si: 0.75 to 1.4%, Mg: 0.30 to 0.75%, 0.95% ≦ 1.73Si—Mg ≦ 1.85% In addition, Mn and V should satisfy the relationship of Mn: 0.02 to 0.20%, V: 0.05 to 0.25%, 0.12% ≦ Mn + V ≦ 0.30% Contains,
Further, Ti: 0.005 to 0.1%, B: 0.0001 to 0.004%, further Cu: 0.03 to 0.4%, the remainder composed of Al and inevitable impurities An aluminum alloy hollow member made of an Al alloy having
The aluminum alloy hollow member has a proof stress: 160 to 250 MPa, a total elongation: 22% or more, and an aluminum alloy hollow member excellent in hydroforming properties in which the ratio of local elongation in the total elongation is 17% or more,
(3) The Al alloy ingot having the composition described in the above (1) to (2) is heated to a temperature of 460 to 560 ° C., then extruded, and then cooled at a cooling rate of 50 ° C./second or more. Then, the manufacturing method of the aluminum alloy hollow member excellent in hydroforming property which performs the aging treatment which heats at the temperature of 150-190 degreeC for 0.5-8 hours,
(4) The Al alloy ingot having the composition described in the above (1) to (2) is heated to a temperature of 460 to 560 ° C., then extruded, and then cooled at a cooling rate of 50 ° C./second or more. Then, after performing a cold drawing process, the manufacturing method of the aluminum alloy hollow member excellent in hydroforming property which performs the aging treatment which heats at the temperature of 150-190 degreeC for 0.5-8 hours,
It has the characteristics.
[0007]
Here, “local elongation” indicates the value of elongation from the highest load point to break in the load-elongation curve, and the ratio of local elongation to the total elongation is a value obtained by dividing the value of local elongation by the total elongation. .
Further, here, the cold drawing process is a cold process for obtaining a predetermined dimensional accuracy by reducing the cross section of the extruded material through a die.
[0008]
The method for producing an aluminum alloy hollow member having excellent hydroforming properties as described in (1) or (2) will be described more specifically.
A billet having the component composition described in the above (1) or (2) is produced by a DC casting method, and this billet is subjected to a homogenization heat treatment by maintaining the billet at a temperature in the range of 510-580 ° C. for 4-16 hours. The billet subjected to the homogenization heat treatment is extruded at a temperature in the range of 460 to 560 ° C., and then immediately cooled at a cooling rate of 50 ° C./second or more. The hollow member obtained by cooling may be cold-drawn as necessary. The aluminum alloy hollow member thus obtained was then subjected to an aging treatment at a temperature of 150 to 190 ° C. for 0.5 to 8 hours, with a yield strength of 160 to 250 MPa, a total elongation of 22% or more, The proportion of the local elongation in the total elongation is 17% or more, and the aluminum alloy hollow member having such a component composition and mechanical properties has good hydroforming properties.
[0009]
The reason for limiting the component composition, mechanical properties, and manufacturing conditions of the aluminum alloy constituting the hollow member as described above will be described.
A. Component composition (a) Si, Mg
These components have the effect of improving the strength by precipitating as a fine Mg ₂ Si compound, but even if the content of either Si or Mg is Si: less than 0.75%, Mg: less than 0.3% In this case, the amount of precipitates to be generated is reduced and the desired strength cannot be ensured. On the other hand, when the content exceeds Si: 1.4% and Mg: 0.75%, hydroforming properties, bending This is not preferable because processability and extrusion or drawing processability are lowered. Therefore, it was set to Si: 0.75 to 1.4% and Mg: 0.30 to 0.75%. More preferable ranges of Si and Mg are Si: 0.7 to 1.2% and Mg: 0.40 to 0.60%.
Furthermore, Si is the excessive content than the amount required for the formation of Mg ₂ Si, is more finely precipitating Mg ₂ Si, and by the excess Si is uniformly dispersed as fine particles, an increase in elongation As a result, the hydroforming property is improved. However, if Si is less than the amount satisfying 0.95% ≦ 1.73Si—Mg, the effect cannot be sufficiently obtained. On the other hand, if the amount satisfying 1.73Si—Mg ≦ 1.85% is exceeded, the grain boundary is not obtained. Precipitated Si remains after the solution treatment and the toughness is lowered, and the hydroforming property and bending workability are also deteriorated. Therefore, Si and Mg contained in the aluminum alloy hollow member of the present invention are Si: 0.75 to 1.4%, Mg: 0.30 to 0.75%, and 0.95 ≦ 1.73Si— It is necessary to satisfy Mg ≦ 1.85.
[0010]
(B) Mn, V
Both of these components form an intermetallic compound with Al, and these serve as nucleation sites for recrystallization, making the extruded structure a fine equiaxed grain structure, thereby improving hydroforming and bending workability. In particular, by adding these components in combination, the effect is further increased. However, if the contents of Mn and V are Mn: less than 0.02% and V: less than 0.05%, the desired effect cannot be obtained. On the other hand, if the contents of Mn and V exceed Mn: 0.20% and V: 0.25%, recrystallization during extrusion is suppressed, and a fibrous structure appears, resulting in hydroforming properties and bending. Since workability deteriorates, it is not preferable. Therefore, the contents of Mn and V were determined to be Mn: 0.02 to 0.20% and V: 0.05 to 0.25%, respectively. It is necessary to add Mn and V in combination, and it is more preferable that the amount of addition at that time satisfies the condition that the sum of Mn and V is 0.12% ≦ Mn + V ≦ 0.30%. Therefore, the addition amounts of Mn and V were determined as Mn: 0.02 to 0.20%, V: 0.05 to 0.25%, and 0.12% ≦ Mn + V ≦ 0.30%.
[0011]
(C) Ti, B
These components are added because they have the effect of refining the cast structure and preventing casting cracks, but even if the content of either Ti or B is Ti: less than 0.005%, B: less than 0.0001% On the other hand, if any content of Ti and B exceeds Ti: 0.1% and B: 0.004%, a huge intermetallic compound is produced and toughness is not obtained. Is lowered, and hydroforming property and bending workability are lowered. Therefore, the contents of Ti and B are set to Ti: 0.005 to 0.1% and B: 0.0001 to 0.004%, respectively.
[0012]
(D) Cu
Since Cu has the effect of improving the strength of the hollow member by dissolving in the substrate, it is added as necessary. However, if the content is less than 0.03%, the desired strength improvement effect cannot be obtained. On the other hand, if the content exceeds 0.4%, the corrosion resistance decreases, which is not preferable. Therefore, it was determined that Cu: 0.03 to 0.4%.
[0013]
B. Mechanical Properties The aluminum alloy hollow member for hydroforming requires strength, and therefore must have a proof stress of 160 MPa or more. Further, in order to say that the hydroforming property is excellent, the total elongation: 22 % Of local elongation in the total elongation: 17% or more is necessary. In particular, in order to accurately mold a hydroformed product having a complicated shape, it is necessary to increase the ratio of local elongation to the total elongation. However, the proof stress, total elongation and local elongation have an upper limit from being an aluminum alloy, the proof stress does not exceed 250 MPa, the total elongation does not exceed 50%, and the ratio of local elongation to the total elongation Does not exceed 35%.
[0014]
C. Manufacturing conditions (e) Extrusion temperature Extrusion temperature is limited to 460-560 ° C. When extrusion is performed at less than 460 ° C, the temperature is too low to sufficiently dissolve solute atoms and obtain the desired strength. On the other hand, it is not preferable because it cannot be performed. On the other hand, if extrusion is performed at a temperature exceeding 560 ° C., the temperature becomes too high and defects such as cracks due to local melting occur, which is not preferable.
[0015]
(F) Cooling rate If the cooling rate after extrusion is less than 50 ° C./second, coarse Mg ₂ Si or Si precipitates are generated at the grain boundaries during cooling, and formability deteriorates. 50 ° C./second or more is necessary. However, even if the cooling rate exceeds 1000 ° C./sec.
[0016]
(G) Aging treatment conditions The aging treatment conditions are defined as 150 to 190 ° C. and held for 0.5 to 8 hours because the aging treatment effect is insufficient even when heated at less than 150 ° C. for 0.5 hours. This is because it is not preferable because the strength cannot be obtained. On the other hand, if the heating is carried out over 190 ° C. for more than 8 hours, the elongation is lowered and the desired value cannot be obtained.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
A billet was prepared by melting and casting an Al alloy billet having the composition shown in Tables 1 and 2 and having a diameter of 204 mm, and homogenized by holding the billet at a temperature of 545 ° C. for 4 hours. Treated, followed by extrusion using a 1650 ton extruder at the temperatures shown in Tables 3-4, immediately followed by cooling at the cooling rates shown in Tables 3-4, and then shown in Tables 3-4 The present invention Al alloy hollow member (hereinafter referred to as the present hollow member) 1 having a thickness of 2.7 mm and an outer diameter of 43 mm by performing an aging treatment of holding time shown in Tables 3 to 4 at a temperature 1 to 3 13, Comparative Al alloy hollow members (hereinafter referred to as comparative hollow members) 1 to 5 and conventional Al alloy hollow members (hereinafter referred to as conventional hollow members) 1 to 3 were produced.
[0018]
Tensile test pieces were cut out from the hollow members 1 to 13 of the present invention thus obtained, the comparative hollow members 1 to 5 and the conventional hollow members 1 to 3, and the yield strength was measured using the tensile test pieces. The total elongation and the ratio of local elongation to the total elongation were measured, and the results are shown in Tables 3-4.
[0019]
Furthermore, the present invention hollow member 1-13, comparison hollow member 1-5 and conventional hollow member 1-3 are loaded with an internal pressure and pushed in the axial direction to expand the tube, and at the fracture position when the fracture occurs The perimeter was obtained, the perimeter change rate until breakage was 18% or more, and less than 18% was indicated by x, and hydroforming properties were evaluated. The results are shown in Tables 3-4.
[0020]
[Table 1]

[0021]
[Table 2]

[0022]
[Table 3]

[0023]
[Table 4]

[0024]
【The invention's effect】
From the results shown in Tables 1 to 4, the present invention hollow members 1 to 13 having the component composition that satisfies the conditions of the present invention, the proof stress, the total elongation and the ratio of the local elongation in the total elongation deviated from the conditions of the present invention. Compared to the conventional hollow members 1 to 3 and comparative hollow members 1 to 5 having a component composition, proof stress, total elongation, and the ratio of local elongation to the total elongation, the tube expansion rate is excellent, and thus the hydroforming property is excellent. I understand that. As described above, since the aluminum alloy hollow member of the present invention is excellent in hydroforming properties, it is possible to produce various parts with light weight and high accuracy, and has excellent effects on the automobile industry such as improvement in fuel consumption. Is what it brings.

Claims

In mass% (hereinafter,% indicates mass%), Si and Mg,
Si: 0.75 to 1.4%, Mg: 0.30 to 0.75%, 0.95% ≦ 1.73Si—Mg ≦ 1.85%, so as to satisfy the relationship,
Further, Mn and V are contained so as to satisfy the relationship of Mn: 0.02 to 0.20%, V: 0.05 to 0.25%, 0.12% ≦ Mn + V ≦ 0.30%,
Further, Ti: 0.005 to 0.1%, B: 0.0001 to 0.004%, the remainder is an aluminum alloy hollow member made of an Al alloy having a composition consisting of Al and inevitable impurities,
The aluminum alloy hollow member has an excellent hydroforming property, wherein the aluminum alloy hollow member has a yield strength of 160 to 250 MPa, a total elongation of 22% or more, and a local elongation ratio of 17% or more.

Si and Mg are contained so as to satisfy the relationship of Si: 0.75 to 1.4%, Mg: 0.30 to 0.75%, 0.95% ≦ 1.73Si—Mg ≦ 1.85%. ,
Further, Mn and V are contained so as to satisfy the relationship of Mn: 0.02 to 0.20%, V: 0.05 to 0.25%, 0.12% ≦ Mn + V ≦ 0.30%,
Further, Ti: 0.005 to 0.1%, B: 0.0001 to 0.004%,
Furthermore, Cu: 0.03 to 0.4% is contained,
The balance is an aluminum alloy hollow member made of an Al alloy having a composition consisting of Al and inevitable impurities,
The aluminum alloy hollow member has an excellent hydroforming property, wherein the aluminum alloy hollow member has a yield strength of 160 to 250 MPa, a total elongation of 22% or more, and a local elongation ratio of 17% or more.

The Al alloy ingot having the composition according to claim 1 or 2 is heated to a temperature of 460 to 560 ° C., then extruded, then cooled at a cooling rate of 50 ° C./second or more, and then 150 to 190 ° C. The manufacturing method of the aluminum alloy hollow member excellent in hydroforming property characterized by performing the aging treatment which heats for 0.5 to 8 hours at temperature.

The Al alloy ingot having the composition according to claim 1 or 2 is heated to a temperature of 460 to 560 ° C., then extruded, and then cooled at a cooling rate of 50 ° C./second or more, and then cold drawn. After manufacturing, the manufacturing method of the aluminum alloy hollow member excellent in hydroforming property characterized by performing the aging treatment which heats for 0.5 to 8 hours at the temperature of 150-190 degreeC.