JP3710249B2

JP3710249B2 - Aluminum extruded profile and method for producing extruded profile and structural member

Info

Publication number: JP3710249B2
Application number: JP10639197A
Authority: JP
Inventors: 伸昭大原; 洋一郎戸次; 知生岡; 和彦後郷
Original assignee: Honda Motor Co Ltd; Furukawa Sky Aluminum Corp
Current assignee: Honda Motor Co Ltd; Furukawa Sky Aluminum Corp
Priority date: 1997-04-23
Filing date: 1997-04-23
Publication date: 2005-10-26
Anticipated expiration: 2017-04-23
Also published as: JPH10298691A

Description

【０００１】
【発明の属する技術分野】
本発明は、オートバイフレーム材、オートバイハンドル材、自転車リム材等に使用しうる、アルミニウム押出形材及びそれを成形加工したアルミニウム構造部材の製造方法に関する。
【０００２】
【従来の技術】
オートバイフレーム、オートバイハンドル材用には従来、押出加工性及び強度に優れた溶接構造用アルミニウム合金として知られるＡｌ−Ｚｎ−Ｍｇ系合金が用いられている。この用途にこれらのＡｌ−Ｚｎ−Ｍｇ系合金が使用されるのは６０６１や６Ｎ０１等のＡｌ−Ｍｇ−Ｓｉ系合金では溶接性や溶接時の熱影響による押出形材の軟化の問題があるが、Ａｌ−Ｚｎ−Ｍｇ系合金は溶接性が優れるとともに溶接部及び熱影響部の強度が自然時効で回復し、耐ＳＣＣ性にも優れるためである。このようなアルミニウム合金として具体的には、オートバイフレーム材、オートバイハンドル材、自転車リム材等には、Ｚｎ：４．５〜５．０％、Ｍｇ：１．０〜２．０％、Ｍｎ：０．２〜０．７％を含有し、残部がＡｌ及び不可避不純物からなるＪＩＳ７Ｎ０１合金、または、Ｚｎ：５．０〜６．０％、Ｍｇ：０．５〜１．０％、Ｚｒ：０．０５〜０．２５％（以上の％は重量％を示す。以下同様に組成の重量％を単に％と示す。）を含有し、残部がＡｌ及び不可避不純物からなるＪＩＳ７００３合金等が使用されている。これらの合金を加工して得られた材料は、高強度で、溶接性、靭性及び耐食性に優れている。
従来、７Ｎ０１や７００３から形成した押出形材では、Ｔ４、Ｔ５材の状態で出荷されることが多く、この場合、これらの材料の機械的性質、特に伸び値が不足するため、デザインが単純でユーザーでの加工がそれほど厳しくない場合は成形が可能であるが、デザインが複雑な場合は、厳しい曲げやスウェージング等の強加工を必要とし、肌荒れや割れを生じる場合があった。しかし最近、二輪フレーム材も高度のデザイン性が要求され、ますます厳しい曲げやスウェージング等の強加工が行われる場合が増加し、強加工に耐える二輪フレーム材が必要とされていた。
しかし、これまでに表面品質を改善した従来技術の代表例として、特開昭６０−１９４０４１、特開平８−１２０３８７、特開平７−１８３６３等があるが、これらはアルマイト性改善やオレンジビール、ストレッチャー、ストレインマークの発生防止等に関するもので、本発明におけるような表面特性を改善すると同時にＴ５調質のままでの強加工領域におけるスウェージング性や曲げ加工性及び溶接後の硬度回復特性を改善し、加工終了後の熱処理を不要としたものは存在しない。
【０００３】
そのため、デザインが複雑で成形が困難な製品に、上記７Ｎ０１や７００３等の従来材を使用する場合、これらの材料の機械的性質、特に伸びを改善するため、材料を一旦完全焼鈍材とした後、成形加工を行い、その後溶体化、焼入れ、時効等の熱処理を行うか、材料及び金型を加熱し温間でこれらの加工を行い、さらに溶接により一体のフレーム構造体とする方法が取られていた。
しかし、この完全焼鈍材を強加工する方法では、加工終了後、溶体化処理、焼入れ、時効硬化処理等の熱処理が必要で、熱処理時の寸法変化、形材表面の再結晶化、納期、コスト等の問題があり、また温間加工する場合は、温間加工温度の管理が困難である等の問題もあり、さらに加工温度によっては前記と同じ、焼入れ→時効等の熱処理を行う必要があった。
また、これらの従来のオートバイフレーム用アルミニウム押出形材の製造方法では、押出速度を増すと、表面再結晶の発生を防止できず、再結晶層の厚さが数百μｍに達する場合がある。
【０００４】
【発明が解決しようとする課題】
本発明は上記の従来の欠点を克服し、Ｔ５材での伸び値に優れ、強加工に耐える二輪フレーム用アルミニウム合金を提供することを目的とする。
また本発明は、Ｔ５材での曲げ加工やスウェージング加工のような強加工に対する加工性を改善し、材料製造工程における完全焼鈍工程を省くことにより二輪フレームの製造工程の簡略化とコストダウンを図ることのできるアルミニウム押出形材とその製造方法を提供することを目的とする。
さらに本発明の目的は、表面性のよい、成形性及び溶接後の強度回復特性に優れたオートバイ用アルミニウム構造部材と、それを生産性よく、低コストで製造しうる方法を提供することにある。
【０００５】
【課題を解決するための手段】
本発明の目的は以下の発明により達成された。
（１）Ｚｎ：４．５〜７．５％、Ｍｇ：０．２０％以上０．５０％未満、Ｔｉ：０．００１〜０．１％、Ｂ：０．０００１〜０．０８％、Ｆｅ：０．３５％以下、Ｓｉ：０．３０％以下、Ｃｕ：０．２％以下を含有し、Ｍｎ：０．１〜０．３％、Ｚｒ：０．１〜０．３％、Ｃｒ：０．０５〜０．２％（以上の％は重量％を示す。）のうち１種または２種以上を含有し、残部がＡｌ及び不可避不純物からなるアルミニウム合金を、液体窒素により押出ダイスを冷却して又は押出ダイスを冷却しないで、１０ｍ／分以上の高速押出加工し、次いで９０〜１２０℃での予備時効処理をし、またはしないで１３０〜１７０℃における人工時効処理をし、液体窒素冷却を行って押出した場合は表面粗さＲmax １０μｍ以下、液体窒素冷却を行わないで押出した場合はＲmax １５μｍ以下、且つ表面再結晶層の厚さが５０μｍ以下で、さらに耐応力腐食割れ性に優れると同時に、強加工領域でのスウェージング加工性と曲げ加工性および溶接後の硬度回復特性に優れ、少なくとも幅方向で２５％、高さ方向で１５％のスウェージング加工を行い得る押出形材とすることを特徴とするオートバイ構造部材用アルミニウム合金押出形材の製造方法。
（２）前記表面再結晶層の厚さを４１μｍ以下にすることを特徴とする（１）記載のオートバイ構造部材用アルミニウム合金押出形材の製造方法。
（３）（１）または（２）に記載の押出形材を、完全焼鈍処理を行わずに、そのまま強加工を行うことを特徴とするオートバイ用アルミニウム合金構造部材の製造方法。
（４）加工欠陥を発生することなく、少なくとも幅方向で２５％、高さ方向で１５％のスウェージング加工を行う（３）記載のオートバイ用アルミニウム合金構造部材の製造方法。
（５）（３）または（４）記載の方法により製造されたオートバイ用アルミニウム合金構造部材。
（６）（３）〜（５）のいずれか１項に記載の製造方法で製造された、加工欠陥を発生することなく少なくとも幅方向で２５％、高さ方向で１５％のスウェージング加工を行ったオートバイ用アルミニウム合金構造部材。
【０００６】
【発明の実施の形態】
本発明に用いるＡｌ−Ｚｎ−Ｍｇ系合金中の元素の添加理由及び組成限定理由を下記に示す。
Ｚｎは、押出材を強化する。Ｚｎの含有量が４．５％未満の場合、十分な強度が得られず押出性が悪化し、７．５％を越えると耐応力腐食割れ性（耐ＳＣＣ性）が低下する。
ＭｇもＺｎ同様に押出材を強化する。Ｍｇの含有量が０．２０％未満の場合、十分な強度が得られない。また、Ｍｇの含有量が０．５０％以上では押出性及び溶接後の強度回復特性が低下し、溶接後のビード部の硬度回復に要する時間が長くなり、さらには加工性が低下し曲げやスウェージング加工が困難となる。Ｍｇの含有量は好ましくは０．３５〜０．４５％である。
Ｔｉ、Ｂは鋳塊組織を微細にし、機械的性能を向上させる。Ｔｉ、Ｂの含有量がそれぞれ０．００１％、０．０００１％未満の場合、この効果はない。Ｔｉ、Ｂの含有量がそれぞれ０．１％、０．０８％を越えると巨大化合物が発生して機械的性質を低下させるとともに上記効果が得られない。
【０００７】
Ｍｎ、Ｚｒ、Ｃｒは、鋳造時に晶出物、均熱時に析出物等の金属間化合物を生成し、押出材の再結晶を抑制する。これらの元素の添加濃度の下限（Ｍｎ、Ｚｒ：０．１％、Ｃｒ：０．０５％）未満では、再結晶を抑制することはできない。また、上限濃度（Ｍｎ、Ｚｒ：０．３％、Ｃｒ：０．２％）を越えると巨大な金属間化合物が発生し、機械的性能が著しく低下する。なお、再結晶を抑制するためには、これらの元素のうち１種または２種以上添加する。
Ｆｅ、Ｓｉが多量に含有されると押出形材の光輝性やアルマイト性が低下する。そのために、Ｆｅ、Ｓｉの含有量をそれぞれ０．３５％、０．３０％以下に限定する。
【０００８】
次にこの合金からの押出形材の製造工程について説明する。
前記の組成を有するアルミニウム合金を、常法に従って、溶解、連続鋳造してビレットを製造し、均質化処理、熱間押出を行い、それぞれの用途に応じて所定の押出形材を製造する。
押出形材の製造は通常の方法に従って行うことができるが、本発明においては高速押出加工を行いうることを特徴とする。本発明においてこの押出加工の限界押出速度は、通常３０ｍ／分、好ましくは２０ｍ／分であり、押出速度を非常に大きくすることができる。従って本発明において押出速度を遅くすることは特に問題なく行うことができるが、従来の７００３系合金よりも押出速度を速くしうることが本発明の特徴である。押出速度の下限は通常５ｍ／分以上、好ましくは１０ｍ／分以上である。
本発明による押出形材は、液体窒素冷却を行って押出した場合は表面粗さＲ_max １０μｍ以下、液体窒素冷却を行わないで押出した場合はＲ_max １５μｍ以下であり、表面再結晶層の厚さは５０μｍ以下である。本発明方法では、このように押出速度を大きくしても、表面粗度が粗くならず、表面再結晶層の平均厚さも厚くならないという特徴を有する。
本発明においては形材を押出後、これをスウェージング、曲げ等の成形加工を行う前に、人工時効処理を行う。この人工時効処理の時効温度はＡｌ−Ｚｎ−Ｍｇ系では低温の、通常１３０〜１７０℃、好ましくは１４０〜１６０℃で行われることが多く、時効条件も１段よりも２段時効が好ましい。２段時効の場合は、１段目が通常９０〜１２０℃、好ましくは９５〜１１５℃で、予備時効後、２段目は前記の１３０〜１７０℃の範囲で行われる。また、時効に必要とする時間は合計６〜２０時間で、２段時効の場合は時効時間を適当に配分する。時効時間が短いと材料強度が不十分で、長いと過時効になり、強度が低下するとともに熱経済性が低下し、意味がない。これにより製品に必要な強度と成形性を付与できる。
【０００９】
また、従来の押出材から構造部材を製造する場合、前記のように成形性を確保するため、押出材を一旦Ｏ材処理した後、スウェージング、曲げ加工を行って、さらにその後、焼入・焼戻を行うなどの熱処理が必要で、この点がユーザーにおける大きな問題となっていた。その後、スウェージングや厳しい曲げ加工等を伴う場合においても、Ｏ材処理をせずにＴ５材のまま厳しいプレス成形や曲げ加工を行うことを可能にしたものである。本発明の押出形材は、強加工領域でのスウェージングや曲げ加工を行い得るという特徴を有する。この強加工とは幅方向で少なくとも２５％及び／又は高さ方向の少なくとも１５％のスウェージング加工を行うこと及び厳しい曲げ加工を行うことなどがあげられる。
Ｔ５材において厳しい成形加工を可能としたのは、▲１▼本発明に用いられるアルミニウム合金組成では押出形材の表面再結晶を抑制しうること、▲２▼さらに、合金成分のうち、Ｚｎ添加量を所定範囲として、特にＭｇ添加量を低い特定の範囲に限定して、押出材の強度は若干低下するが伸び値が改善されることによるのである。すなわち、表面再結晶制御により形材の肌荒れ不良を防止し、さらに伸び値の改善により、強加工時の割れを防止したものであり、本発明により、初めて両特性を満足する溶接用中強度アルミニウム合金を用いたオートバイフレーム用材料が得られたのである。
【００１０】
本発明における押出加工温度（押出ビレットの予熱温度）は、従来と特に変わらないが、４２０〜４９０℃で、押出生産性を考慮すると、好ましい範囲は４４０〜４９０℃である。
押出加工温度が４９０℃を超えると、押出形材の表面再結晶層厚さが所望の範囲を満足せず、逆に４２０℃未満では表面再結晶厚さは問題ないが、押出生産性が低下し、押出が困難となる。
また、本発明においては押出形材を形成する際、ダイスを液体窒素で冷却し、押出加工発熱による温度増加を防止し製品温度を低下させ再結晶を防止することができる。
この場合、押出ダイスと押出形材表面の冷却により押出材の製品温度を４００〜４７０℃にするのが望ましく、押出生産性を考慮すると製品温度は４２０〜４７０℃とするのが好ましい。
この時、形材製品温度の上限は形材表面が再結晶しない限り高い方が望ましいので、望ましい範囲も４７０℃のままで良い。
また押出加工時の押出ダイスに対する液体窒素の流量は、前記のように冷却能が十分であれば特に制限はないが、好ましくは１０〜３０ｋｇ／時間である。この液体窒素による押出形材表面の急速冷却は、押出形材の表面品質をさらに向上させる効果がある。
また、液体窒素冷却を行わない場合は、押出時の押出ダイスと形材表面の冷却がないので、ビレット予熱温度の上限を液体窒素冷却を行う場合よりも２０〜３０℃低めの４６０〜４７０℃とするのが望ましい。
本発明において、このような押出形材を時効処理後、製品形状に応じてスウェージング加工、曲げ加工等のオートバイ用構造部材としての成形加工を行うもので、また必要により、このような成形加工後、溶接等による組立てを行う。
本発明において製造されるオートバイ用アルミニウム構造部材は、オートバイフレーム、オートバイハンドルなどであるが、これに限定されるものではない。また、本発明によるアルミニウム構造部材は自転車リム材等、自転車用構造部材としても用いうるものであることはいうまでもない。
【００１１】
【実施例】
次に、本発明を実施例に基づきさらに詳細に説明する。
表１に示す組成の合金を通常の方法により溶解し、鋳造（ＤＣ鋳造もしくはホットトップ鋳造）して鋳塊を得た。この鋳塊を４７０℃で６時間均質化処理して押出ビレットを作製した。次にビレットを４５０℃に加熱し、図１に断面図で示す形材を押出した。このときの押出速度を試験材の限界押出速度と同じにした。これは、試験材１〜６（本発明）では２０ｍ／分、試験材７〜１２（比較例及び従来例）では３〜７ｍ／分である。
【００１２】
なお、試験材４〜６については押出ダイスを液体窒素の流量を２０ｋｇ／時間に設定して冷却した。ダイス表面の温度は約４３０℃±１０℃とした。
押出直後の形材はファン空冷した。押出形材を引張矯正した後に時効処理（１０５℃×８時間→１５５℃×８時間）を施した。
このようにして得られたＴ５形材について、限界押出速度とＴ５形材の表面再結晶層の平均厚さ、表面粗さ、常温における引張性能と耐ＳＣＣ性を試験した。この結果を表２に示した。
また、Ｔ５形材の溶接後の硬度回復に要する時間、スウェージング加工時の割れ発生状況の測定・観察結果も表２に示す。参考のため、Ｔ４材（常温で２週間以上放置したもの）も試作し、これらについても表２と同様の特性を評価した。このスウェージング加工試験は次のようにして行った。スウェージング加工には図１に示す形状の寸法：巾（Ｗ）７０ｍｍ×高さ（Ｈ）３０ｍｍ×肉厚（ｔ）３ｍｍの形材を用い、これを巾４９ｍｍ×高さ２５．５ｍｍに加工した。この際巾方向、高さ方向の圧下量はそれぞれ３０％、１５％である。
なお、押出速度を表３のように１０〜２０ｍ／分に上昇させた以外は試験材７〜１２とそれぞれ全く同様にして押出加工し、時効処理して試験材７ａ〜１２ａを形成した。このものの表面性状及びスウェージング加工性、溶接後の硬度の回復性を試験し、表３に示した。
【００１３】
【表１】

【００１４】
【表２】

【００１５】
【表３】

【００１６】
表２の結果から明らかなように、試験材Ｎｏ．７、８は、引張性能のうち、引張強さ、耐力が劣り、しかも限界押出速度が非常に低く、表面性状も劣るものしか得られない。また、これらの試験材は、溶接後の硬度回復に長時間を要する。また、試験材Ｎｏ．９、１０は、引張性能中、伸びが悪く、また、耐ＳＣＣ性が悪い。また、限界押出速度及び表面性状が劣る。さらに、スウェージング加工によって割れが生じ、溶接後の硬度回復性にも劣る。
これに対し、実施例のＮｏ．１〜６の押出形材は、限界押出速度が著しく大きく、押出形材の表面性状も優れ（表面再結晶層が薄く、表面の肌荒れがなく平滑である）、耐ＳＣＣ性に優れる。また、試験材Ｎｏ．１〜６はスウェージング加工性に優れ、溶接部の硬度回復に要する時間が短い。
さらに、従来例としての試験材Ｎｏ．１１、１２のＴ５形材は、限界押出速度が非常に低く、また、スウェージング加工において割れが発生してしまう。表２には示していないが、常温で２週間以上室温放置したＴ４材の表面粗さ、引張特性はほぼ同等で、耐ＳＣＣ性、溶接後の硬度回復時間等は、それほど変らないが、これらの材料は曲げやスウェージング加工において割れが発生し、変形抵抗が大きく成形不能であった。
なお、試験材Ｎｏ．４、５、６の結果から明らかなように、液体窒素によるダイス冷却が表面性状の改善に有効である。
表３の結果から明らかなように、試験材Ｎｏ．７〜１２に対応するＮｏ．７ａ〜１２ａは、他の条件は同じにして押出速度を上げた場合であるが、押出形材の表面性状（表面粗さ、表面再結晶層の平均厚さ）が著しく悪化し、この押出形材はスウェージング加工性も劣るものであった。
【００１７】
【発明の効果】
本発明方法によれば、スウェージング加工性などの、オートバイ構造部材（部品）とするのに必要な強加工における成形加工性の優れる押出形材を製造することができ、しかも、高速で表面性状の優れた肌荒れのない押出形材を押出加工で製造でき、生産性を著しく高めることができる。このようにして得られた押出形材は、熱処理を行わなくてもそのまま厳しい曲げやスウェージング等の強加工を行うことができるという効果を奏する。さらに本発明方法によるオートバイ用アルミニウム構造部材は溶接性に優れ、溶接後、溶接ビード及びその近傍の硬度回復が速いという優れた効果を奏する。
本発明方法によれば、スウェージング加工等の加工後の熱処理が不要となって、スウェージング加工等の強加工が実施しやすくなり、また、製造工程を短縮でき、オートバイ用アルミニウム構造材の製造工程において製造コストの低減、生産性の向上を図ることができる。
【図面の簡単な説明】
【図１】実施例において製造した押出形材の断面図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an aluminum extruded profile that can be used for a motorcycle frame material, a motorcycle handle material, a bicycle rim material, and the like, and a method for manufacturing an aluminum structural member formed by processing the aluminum extruded profile.
[0002]
[Prior art]
Conventionally, Al—Zn—Mg alloys known as aluminum alloys for welded structures having excellent extrudability and strength have been used for motorcycle frames and motorcycle handle materials. These Al-Zn-Mg based alloys are used for this purpose. However, in Al-Mg-Si based alloys such as 6061 and 6N01, there is a problem of softening of the extruded shape due to the weldability and the heat effect during welding. This is because the Al—Zn—Mg alloy has excellent weldability, the strength of the welded part and the heat-affected zone is recovered by natural aging, and the SCC resistance is also excellent. Specific examples of such aluminum alloys include motorcycle frame materials, motorcycle handle materials, bicycle rim materials, etc .: Zn: 4.5 to 5.0%, Mg: 1.0 to 2.0%, Mn: JIS 7N01 alloy containing 0.2 to 0.7%, the balance being Al and inevitable impurities, or Zn: 5.0 to 6.0%, Mg: 0.5 to 1.0%, Zr: JIS 7003 alloy containing 0.05 to 0.25% (the above% indicates% by weight. Similarly, the% by weight of the composition is simply referred to as%), and the balance is Al and inevitable impurities are used. Has been. Materials obtained by processing these alloys have high strength and are excellent in weldability, toughness, and corrosion resistance.
Conventionally, extruded shapes formed from 7N01 and 7003 are often shipped in the state of T4 and T5 materials. In this case, the mechanical properties of these materials, particularly the elongation value, are insufficient, so the design is simple. Molding is possible when the user's processing is not so severe, but when the design is complicated, severe processing such as severe bending and swaging is required, which may cause rough skin and cracks. Recently, however, two-wheel frame materials are also required to have a high degree of design, and the number of cases in which severe processing such as bending and swaging is increasingly performed has increased, and a two-wheel frame material that can withstand strong processing has been required.
However, as representative examples of conventional techniques for improving the surface quality, there are JP-A-60-194041, JP-A-8-120387, JP-A-7-18363, and the like. This is related to prevention of the occurrence of lecher and strain marks, etc., improving the surface characteristics as in the present invention, and at the same time improving the swaging and bending workability and the hardness recovery characteristics after welding in T5 tempering. However, there is no one that does not require heat treatment after the end of processing.
[0003]
Therefore, when conventional materials such as 7N01 and 7003 are used for products that are complicated in design and difficult to form, after the materials are once made into a fully annealed material in order to improve the mechanical properties of these materials, particularly the elongation. , And then heat treatment such as solution treatment, quenching, aging, etc., or heat the material and the mold to perform these processes warm, and further weld to form an integrated frame structure It was.
However, this method of strong processing of fully annealed materials requires heat treatment such as solution treatment, quenching, age hardening treatment, etc. after the completion of processing, dimensional change during heat treatment, recrystallization of shape surface, delivery date, cost In the case of warm working, there is also a problem that it is difficult to control the warm working temperature, and depending on the working temperature, it is necessary to perform the same heat treatment such as quenching → aging as described above. It was.
Further, in these conventional methods for producing an aluminum extruded shape for motorcycle frames, when the extrusion speed is increased, the occurrence of surface recrystallization cannot be prevented, and the thickness of the recrystallized layer may reach several hundred μm.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to provide an aluminum alloy for a two-wheeled frame that overcomes the above-mentioned conventional drawbacks, has an excellent elongation value with a T5 material, and can withstand strong processing.
In addition, the present invention improves workability for strong processing such as bending processing and swaging processing with T5 material, and simplifies the manufacturing process of the two-wheeled frame and reduces the cost by omitting the complete annealing process in the material manufacturing process. It is an object of the present invention to provide an aluminum extruded shape and a method for producing the same.
A further object of the present invention is to provide an aluminum structural member for motorcycles having good surface properties, excellent formability and excellent strength recovery characteristics after welding, and a method capable of producing the same with high productivity and low cost. .
[0005]
[Means for Solving the Problems]
The object of the present invention has been achieved by the following invention.
(1) Zn: 4.5 to 7.5%, Mg: 0.20% or more and less than 0.50%, Ti: 0.001 to 0.1%, B: 0.0001 to 0.08%, Fe : 0.35% or less, Si: 0.30% or less, Cu: 0.2% or less, Mn: 0.1-0.3%, Zr: 0.1-0.3%, Cr: An aluminum alloy containing one or more of 0.05 to 0.2% (the above% indicates weight%), the balance being Al and inevitable impurities , and cooling the extrusion die with liquid nitrogen With or without cooling the extrusion die, high-speed extrusion at 10 m / min or higher, followed by pre-aging at 90 to 120 ° C. or artificial aging at 130 to 170 ° C. and cooling with liquid nitrogen When the extrusion is performed, the surface roughness Rmax is 10 μm or less and the extrusion is performed without cooling with liquid nitrogen. When Rmax is 15 μm or less and the thickness of the surface recrystallized layer is 50 μm or less, it has excellent stress corrosion cracking resistance, and at the same time, swaging workability and bending workability in a strong working region and hardness recovery after welding. A method for producing an aluminum alloy extruded shape for a motorcycle structural member, characterized in that the extruded shape has excellent characteristics and can be subjected to a swaging of at least 25% in the width direction and 15% in the height direction.
(2) The method for producing an aluminum alloy extruded shape for a motorcycle structural member according to (1 ), wherein the thickness of the surface recrystallized layer is 41 μm or less.
(3) A method for producing an aluminum alloy structural member for a motorcycle, characterized in that the extruded section according to (1) or (2) is subjected to strong processing as it is without performing a complete annealing treatment.
(4) The method for producing an aluminum alloy structural member for a motorcycle according to (3), wherein swaging is performed at least 25% in the width direction and 15% in the height direction without generating a processing defect.
(5) An aluminum alloy structural member for motorcycles produced by the method according to (3) or (4).
(6) Swaging processing of at least 25% in the width direction and 15% in the height direction, which is manufactured by the manufacturing method according to any one of (3) to (5) without generating a processing defect. Made aluminum alloy structural member for motorcycles.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The reasons for adding elements and the reasons for limiting the composition in the Al—Zn—Mg alloy used in the present invention are shown below.
Zn reinforces the extruded material. When the Zn content is less than 4.5%, sufficient strength cannot be obtained and the extrudability deteriorates, and when it exceeds 7.5%, the stress corrosion cracking resistance (SCC resistance) decreases.
Mg strengthens the extruded material in the same way as Zn. If the Mg content is less than 0.20%, sufficient strength cannot be obtained. Further, when the Mg content is 0.50% or more, the extrudability and strength recovery characteristics after welding are lowered, the time required for the hardness recovery of the bead part after welding is prolonged, and further, workability is lowered and bending and Swaging is difficult. The Mg content is preferably 0.35 to 0.45%.
Ti and B refine the ingot structure and improve the mechanical performance. This effect is not obtained when the contents of Ti and B are less than 0.001% and 0.0001%, respectively. If the contents of Ti and B exceed 0.1% and 0.08%, respectively, a giant compound is generated and the mechanical properties are deteriorated and the above effect cannot be obtained.
[0007]
Mn, Zr, and Cr generate an intermetallic compound such as a crystallized product during casting and a precipitate during soaking, and suppress recrystallization of the extruded material. If it is less than the lower limit (Mn, Zr: 0.1%, Cr: 0.05%) of the additive concentration of these elements, recrystallization cannot be suppressed. On the other hand, when the concentration exceeds the upper limit concentration (Mn, Zr: 0.3%, Cr: 0.2%), a huge intermetallic compound is generated and the mechanical performance is remarkably lowered. In order to suppress recrystallization, one or more of these elements are added.
When a large amount of Fe and Si is contained, the glitter and alumite properties of the extruded shape are lowered. Therefore, the contents of Fe and Si are limited to 0.35% and 0.30% or less, respectively.
[0008]
Next, the manufacturing process of the extrusion shape material from this alloy is demonstrated.
The aluminum alloy having the above composition is melted and continuously cast according to a conventional method to produce a billet, homogenized, and hot extruded, and a predetermined extruded shape is produced according to each application.
Although the extruded shape can be produced according to a normal method, the present invention is characterized in that high-speed extrusion can be performed. In the present invention, the limit extrusion speed of this extrusion process is usually 30 m / min, preferably 20 m / min, and the extrusion speed can be very high. Therefore, in the present invention, the extrusion speed can be lowered without any particular problem, but it is a feature of the present invention that the extrusion speed can be increased as compared with the conventional 7003-based alloy. The lower limit of the extrusion speed is usually 5 m / min or more, preferably 10 m / min or more.
The extruded profile according to the present invention has a surface roughness R _{max of} 10 μm or less when extruded with liquid nitrogen cooling, and R _{max of} 15 μm or less when extruded without liquid nitrogen cooling. The thickness is 50 μm or less. In the method of the present invention, even when the extrusion speed is increased, the surface roughness is not roughened, and the average thickness of the surface recrystallized layer is not thickened.
In the present invention, an artificial aging treatment is performed after extruding the shape material and before performing molding such as swaging and bending. The aging temperature of this artificial aging treatment is often low at an Al—Zn—Mg system, usually 130 to 170 ° C., preferably 140 to 160 ° C., and the aging conditions are preferably two-stage aging rather than one stage. In the case of two-stage aging, the first stage is usually 90 to 120 ° C., preferably 95 to 115 ° C. After preliminary aging, the second stage is carried out in the range of 130 to 170 ° C. The total time required for aging is 6 to 20 hours. In the case of two-stage aging, the aging time is appropriately allocated. If the aging time is short, the material strength is insufficient, and if the aging time is long, the material becomes over-aged. Thereby, strength and moldability required for the product can be imparted.
[0009]
Moreover, when manufacturing a structural member from the conventional extruded material, in order to ensure the moldability as described above, the extruded material is once treated with an O material, then subjected to swaging and bending, and then quenched and bent. Heat treatment such as tempering is necessary, which is a big problem for users. After that, even when swaging or severe bending work is involved, it is possible to perform severe press molding and bending work without changing the O material treatment with the T5 material. The extruded profile of the present invention is characterized by being able to perform swaging and bending in a strong working region. The strong processing includes performing a swaging process of at least 25% in the width direction and / or at least 15% in the height direction, and performing a severe bending process.
The T5 material has made it possible to perform a severe forming process. (1) The aluminum alloy composition used in the present invention can suppress the surface recrystallization of the extruded shape. (2) Further, among the alloy components, Zn is added. This is because the strength of the extruded material is slightly reduced but the elongation value is improved by limiting the amount to a predetermined range, and in particular limiting the Mg addition amount to a low specific range. In other words, the surface recrystallization control prevents the rough surface of the profile from being damaged, and the elongation value improves to prevent cracking during strong processing. A motorcycle frame material using an alloy was obtained.
[0010]
Although the extrusion processing temperature (preheating temperature of the extrusion billet) in the present invention is not particularly different from the conventional one, it is 420 to 490 ° C., and the preferable range is 440 to 490 ° C. in consideration of the extrusion productivity.
If the extrusion temperature exceeds 490 ° C, the surface recrystallized layer thickness of the extruded profile does not satisfy the desired range. Conversely, if it is less than 420 ° C, there is no problem with the surface recrystallized thickness, but the extrusion productivity decreases. However, extrusion becomes difficult.
Further, in the present invention, when forming the extruded shape, the die is cooled with liquid nitrogen to prevent an increase in temperature due to heat generated by the extrusion process, thereby reducing the product temperature and preventing recrystallization.
In this case, the product temperature of the extruded material is desirably 400 to 470 ° C. by cooling the extrusion die and the surface of the extruded profile, and the product temperature is preferably 420 to 470 ° C. in view of extrusion productivity.
At this time, since the upper limit of the shape product temperature is desirably higher as long as the shape surface is not recrystallized, the desirable range may remain at 470 ° C.
The flow rate of liquid nitrogen with respect to the extrusion die at the time of extrusion is not particularly limited as long as the cooling ability is sufficient as described above, but is preferably 10 to 30 kg / hour. This rapid cooling of the extruded profile surface with liquid nitrogen has the effect of further improving the surface quality of the extruded profile.
Further, when liquid nitrogen cooling is not performed, there is no cooling of the extrusion die and the shape material surface at the time of extrusion, so the upper limit of the billet preheating temperature is 460 to 470 ° C. which is 20 to 30 ° C. lower than when liquid nitrogen cooling is performed. Is desirable.
In the present invention, after aging treatment of such an extruded profile, it is subjected to molding processing as a structural member for motorcycles such as swaging processing and bending processing according to the product shape, and if necessary, such molding processing Then, assembly by welding or the like is performed.
The aluminum structural member for motorcycle manufactured in the present invention is a motorcycle frame, a motorcycle handle or the like, but is not limited thereto. Further, it goes without saying that the aluminum structural member according to the present invention can be used as a bicycle structural member such as a bicycle rim material.
[0011]
【Example】
Next, the present invention will be described in more detail based on examples.
An alloy having the composition shown in Table 1 was melted by an ordinary method and cast (DC casting or hot top casting) to obtain an ingot. The ingot was homogenized at 470 ° C. for 6 hours to produce an extruded billet. Next, the billet was heated to 450 ° C., and the profile shown in the sectional view in FIG. 1 was extruded. The extrusion speed at this time was the same as the limit extrusion speed of the test material. This is 20 m / min for the test materials 1 to 6 (invention) and 3 to 7 m / min for the test materials 7 to 12 (comparative and conventional examples).
[0012]
In addition, about the test materials 4-6, the extrusion die was cooled by setting the flow volume of liquid nitrogen to 20 kg / hour. The die surface temperature was about 430 ° C. ± 10 ° C.
The shape immediately after extrusion was cooled by a fan. An aging treatment (105 ° C. × 8 hours → 155 ° C. × 8 hours) was performed after the extruded profile was straightened.
The T5 profile thus obtained was tested for the limiting extrusion rate, the average thickness of the surface recrystallized layer of the T5 profile, the surface roughness, the tensile performance at room temperature and the SCC resistance. The results are shown in Table 2.
Table 2 also shows the time required for the hardness recovery after welding of the T5 profile and the measurement / observation results of the crack occurrence state during swaging. For reference, T4 materials (those allowed to stand at room temperature for 2 weeks or more) were also prototyped, and the same characteristics as in Table 2 were also evaluated. This swaging test was performed as follows. The shape of the shape shown in FIG. 1 is used for the swaging process: a shape (width (W) 70 mm × height (H) 30 mm × wall thickness (t) 3 mm) is processed into a width 49 mm × height 25.5 mm. did. At this time, the amount of reduction in the width direction and the height direction is 30% and 15%, respectively.
Except that the extrusion speed was increased to 10 to 20 m / min as shown in Table 3, extrusion was performed in exactly the same manner as test materials 7 to 12, respectively, and aging treatment was performed to form test materials 7a to 12a. This was tested for surface properties, swaging workability, and recoverability of hardness after welding, and is shown in Table 3.
[0013]
[Table 1]

[0014]
[Table 2]

[0015]
[Table 3]

[0016]
As is apparent from the results in Table 2, the test material No. In Nos. 7 and 8, only tensile strength and yield strength are inferior among tensile performances, and the critical extrusion speed is very low and surface properties are inferior. Moreover, these test materials require a long time to recover the hardness after welding. In addition, test material No. Nos. 9 and 10 have poor elongation during tensile performance and poor SCC resistance. Moreover, the limit extrusion speed and surface properties are inferior. Further, cracking occurs due to the swaging process, and the hardness recoverability after welding is poor.
On the other hand, in Example No. The extruded shapes 1 to 6 have a remarkably large limit extrusion speed, and the surface properties of the extruded shapes are excellent (the surface recrystallized layer is thin, the surface is not rough and smooth), and the SCC resistance is excellent. In addition, test material No. Nos. 1 to 6 are excellent in swaging workability, and the time required for the hardness recovery of the welded portion is short.
Furthermore, test material No. as a conventional example. The 11 and 12 T5 profiles have a very low limit extrusion speed, and cracking occurs in the swaging process. Although not shown in Table 2, the surface roughness and tensile properties of T4 materials left at room temperature for more than 2 weeks at room temperature are almost the same, SCC resistance, hardness recovery time after welding, etc. are not changed so much. This material had cracks in bending and swaging, and had a large deformation resistance and could not be molded.
The test material No. As is clear from the results of 4, 5, and 6, die cooling with liquid nitrogen is effective in improving the surface properties.
As is apparent from the results in Table 3, the test material No. No. corresponding to 7-12. 7a to 12a are cases where the extrusion speed was increased under the same conditions, but the surface properties (surface roughness, average thickness of the surface recrystallized layer) of the extruded shape material deteriorated significantly. The material was inferior in swaging processability.
[0017]
【The invention's effect】
According to the method of the present invention, it is possible to produce an extruded shape having excellent molding processability in strong processing necessary for making a motorcycle structural member (part) such as swaging processability, and at the same time, surface properties at high speed. Can be produced by extrusion processing, and productivity can be remarkably enhanced. The extruded profile thus obtained has the effect that it can be subjected to severe processing such as severe bending and swaging as it is without heat treatment. Furthermore, the aluminum structural member for motorcycles according to the method of the present invention is excellent in weldability, and exhibits an excellent effect that the hardness recovery in the weld bead and its vicinity is quick after welding.
According to the method of the present invention, post-processing heat treatment such as swaging is not necessary, and it becomes easy to perform strong processing such as swaging, and the manufacturing process can be shortened. In the process, manufacturing cost can be reduced and productivity can be improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an extruded profile produced in an example.

Claims

Zn: 4.5-7.5%, Mg: 0.20% or more and less than 0.50%, Ti: 0.001-0.1%, B: 0.0001-0.08%, Fe: 0.0. 35% or less, Si: 0.30% or less, Cu: 0.2% or less, Mn: 0.1-0.3%, Zr: 0.1-0.3%, Cr: 0.05 An aluminum alloy containing one or more of ~ 0.2% (the above% indicates weight%), the balance being Al and inevitable impurities , cooling the extrusion die with liquid nitrogen or Without cooling the extrusion die, perform high-speed extrusion processing at 10 m / min or higher, and then perform pre-aging treatment at 90 to 120 ° C. or artificial aging treatment at 130 to 170 ° C. and perform liquid nitrogen cooling. When extruded, the surface roughness Rmax is 10 μm or less, and when extruded without liquid nitrogen cooling Has an Rmax of 15 μm or less and a surface recrystallized layer thickness of 50 μm or less, and is excellent in stress corrosion cracking resistance, and at the same time, it has swaging workability and bending workability in a strong working region, and hardness recovery characteristics after welding. A method for producing an aluminum alloy extruded shape for a motorcycle structural member, which is excellent and has an extruded shape capable of performing swaging at least 25% in the width direction and 15% in the height direction.

The method for producing an aluminum alloy extruded shape for a motorcycle structural member according to claim 1, wherein the thickness of the surface recrystallized layer is 41 µm or less.

A method for producing an aluminum alloy structural member for a motorcycle, comprising subjecting the extruded section according to claim 1 or 2 to strong processing without performing a complete annealing treatment.

The method for producing an aluminum alloy structural member for a motorcycle according to claim 3, wherein swaging is performed at least 25% in the width direction and 15% in the height direction without causing any processing defects.

The aluminum alloy structural member for motorcycles manufactured by the method of Claim 3 or 4.

The aluminum for motorcycles manufactured by the manufacturing method according to any one of claims 3 to 5 and subjected to swaging at least 25% in the width direction and 15% in the height direction without causing a processing defect. Alloy structural member.