JP2004315913A - Aluminum alloy sheet for high temperature forming, and method of producing aluminum alloy panel - Google Patents

Aluminum alloy sheet for high temperature forming, and method of producing aluminum alloy panel Download PDF

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JP2004315913A
JP2004315913A JP2003112978A JP2003112978A JP2004315913A JP 2004315913 A JP2004315913 A JP 2004315913A JP 2003112978 A JP2003112978 A JP 2003112978A JP 2003112978 A JP2003112978 A JP 2003112978A JP 2004315913 A JP2004315913 A JP 2004315913A
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temperature
aluminum alloy
panel
treatment
forming
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JP4022497B2 (en
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Tetsuya Masuda
哲也 増田
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Kobe Steel Ltd
株式会社神戸製鋼所
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a series 6,000 aluminum alloy sheet for high temperature forming which has high proof stress under high temperature forming and in which the proof stress of a panel is kept high even if slow cooling and artificial age hardening treatment at a relatively low temperature for a relatively short time are performed after the high temperature forming, and to provide a method of producing an aluminum alloy panel. <P>SOLUTION: The Al-Mg-Si based aluminum alloy sheet has a composition which comprises 0.6 to 1.3% Si, 0.3 to 0.9% Mg, 0.01 to 0.65% Mn and 0.4 to 1.0% Cu, in which the mass ratio of Si/Mg is ≥1.0, and the balance Al with inevitable impurities. The maximum flow stress on a high temperature tensile test at a temperature of 500°C and also at a strain rate of 10<SP>-1</SP>/s is ≥25 MPa, and 0.2% proof stress after the process where the aluminum alloy sheet is held at 500°C for 3 min, is thereafter subjected to heat treatment where the aluminum alloy sheet is cooled down to room temperature at a mean cooling rate of ≤10°C/s in the range of 500 to 200°C and is further subjected to artificial age hardening treatment at 170°C for 30 min is ≥170 MPa. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【0001】
【発明の属する技術分野】
本発明は、高温成形用アルミニウム合金板およびアルミニウム合金パネルの製造方法(以下、アルミニウムをAlとも言う)に関するものである。
【0002】
【従来の技術】
従来から、アルミニウム合金板を難加工形状のパネルに成形するために、アルミニウム合金板を加熱して、460 〜550 ℃の高温領域で高い伸びの特性を生じさせて高成形性を得るような、高速超塑性成形などの高温成形方法が検討されている。
【0003】
これら高温成形用のアルミニウム合金板としては、AA乃至JIS 規格でいう 5000 系 (以下、単に5000系と言う) の Al−Mg系アルミニウム合金が主流となっている。このため、高速超塑性成形用Al−Mg 系アルミニウム合金が従来から多数開発提案されている。
【0004】
これに対し、特に、自動車パネルなど、塗装焼付の際の焼付硬化性 (人工時効硬化性) に優れたAl−Mg−Si系のAA乃至JIS 規格でいう 6000 系 (以下、単に6000系と言う) のアルミニウム合金板の使用も、高温成形の分野で検討されている。これら6000系アルミニウム合金板は、合金元素量が多い他の5000系などのアルミニウム合金に比して、合金元素量が比較的少ない。このため、これら6000系アルミニウム合金パネルのスクラップを、Al合金溶解材 (溶解原料) として再利用する際に、元の6000系アルミニウム合金鋳塊が得やすく、リサイクル性にも優れているという利点もある。
【0005】
高温成形分野への6000系アルミニウム合金板の提案例として、例えば、6000系アルミニウム合金板の平均結晶粒径を15〜120 μm とし、また高速超塑性成形時のひずみ速度と成形温度とを特定の関係に制御して、高速超塑性成形時に高い伸びを得るとともに、成形後にT6処理を施して、引張強度300MPa以上の高い強度を得ることが提案されている (特許文献1参照)。また、溶体化処理などが施されていない6000系アルミニウム合金板を溶体化処理に必要な温度でブロー成形を行い、その後成形品に焼き戻し処理を施して、200MPa以上の高耐力を得ることも提案されている (特許文献2参照)。
【0006】
【特許文献1】
特開平11−131165 号公報
【特許文献2】
特開2001−58221号公報
【0007】
【発明が解決しようとする課題】
しかし、特許文献2のように、溶体化処理に必要な温度で高速超塑性成形を行った場合、この高温下における6000系アルミニウム合金パネルの強度 (耐力) が著しく低下するという問題がある。これは、特許文献1のように、高速超塑性成形時のひずみ速度と成形温度とを特定の関係に制御して、高速超塑性成形時に高い伸びを得る場合でも同様である。
【0008】
このため、特許文献1も2も意図していない、高速超塑性成形の終了時に、金型から成形したパネルを離型するなど、成形パネルをハンドリングするに必要な強度 (耐力) が得られない、という新たな問題が生じる。また、ハンドリング時に成形パネルの変形などが生じる、という新たな問題もある。
【0009】
更に、成形後に人工時効硬化処理を施しても、200MPa以上の高耐力を得ることができないという新たな問題が生じる。この点、前記特許文献1でも、成形後に人工時効硬化処理を施して、200MPa以上の高耐力を得ることができるとしている。しかし、その人工時効硬化処理条件は、175 ℃という比較的高温で、しかも10時間という長時間の処理を行なっている。また、前記特許文献1には高速超塑性成形後のパネルの耐力の開示も無い。これに対して、実際の自動車パネルの塗装焼付処理の条件は、塗料の改善や自動車生産工程の効率化に伴い、150 〜180 ℃で20〜40分間保持する、比較的低温で短時間の人工時効硬化処理が主流となっている。このような、実際の比較的低温で短時間の人工時効硬化処理では、成形後の6000系アルミニウム合金パネルが200MPa以上の高耐力を得ることは到底できない。
【0010】
この点は、前記特許文献2でも全く同様である。即ち、前記特許文献2には、成形時の熱履歴を模擬して、530 ℃で14分間という高温長時間の溶体化処理後、冷却速度2 ℃/ 秒で冷却した後、常温に13.5時間放置してから、180 ℃で40分保持するという、比較的高温で長時間の人工時効硬化処理条件によって、170MPa以上の高耐力を得るとしている (図4 の成形温度毎の人工時効硬化処理時間と耐力との関係から読み取る) 。したがって、生産性を向上させるべく、成形時間の短時間化を図った場合、および/ または、より低温短時間の人工時効硬化処理では、成形後の6000系アルミニウム合金パネルが200MPa以上の高耐力を得ることは到底できない。この人工時効硬化処理後に高耐力を得られない傾向は、高温成形後に放冷などの緩冷却を行い、かつより低温短時間の人工時効硬化処理を行なった場合に著しい。
【0011】
本発明はこの様な事情に着目してなされたものであって、その目的は、溶体化処理に必要な温度で高温成形を行っても、その高温下での耐力が高く、また、この高温成形後に緩冷却を行い、かつ比較的低温で短時間の人工時効硬化処理後を行なっても、人工時効硬化処理後のパネルの耐力が高い高温成形用6000系アルミニウム合金板およびアルミニウム合金パネルの製造方法を提供しようとするものである。
【0012】
【課題を解決するための手段】
この目的を達成するために、本発明高温成形用Al−Mg−Si系アルミニウム合金板の要旨は、Si:0.6〜1.3%、Mg:0.3〜0.9%、Mn:0.01 〜0.65% 、Cu:0.4〜1.0%を含み、かつSi/Mg が質量比で1.0 以上であり、残部Alおよび不可避的不純物からなるAl−Mg−Si系アルミニウム合金板であって、500 ℃の温度でかつ歪み速度:10 −1/sの条件で高温引張試験をした際の最大流動応力が25MPa 以上であるとともに、500 ℃で3 分間保持した後、500 〜200 ℃の範囲を平均冷却速度10℃/s以下で室温まで放冷する熱処理後、更に170 ℃で30分間保持する人工時効硬化処理を施した後の0.2%耐力が170MPa以上である特性を、このアルミニウム合金板が有することである。
【0013】
また、この目的を達成するための、本発明アルミニウム合金パネルの製造方法の要旨は、Si:0.6〜1.3%、Mg:0.3〜0.9%、Mn:0.01 〜0.65% 、Cu:0.4〜1.0%を含み、かつSi/Mg が質量比で1.0 以上であり、残部Alおよび不可避的不純物からなるAl−Mg−Si系アルミニウム合金板を、460 〜550 ℃の高温で成形してパネル化する際に、このパネルの前記高温成形時の最大流動応力を25MPa 以上として成形し、更にこの高温成形後のパネルに150 〜180 ℃で20〜40分間保持する人工時効硬化処理を施し、この人工時効硬化処理後のパネルの0.2%耐力を170MPa以上とすることである。
【0014】
本発明では、6000系アルミニウム合金板の基本成分であるSiとMgの含有量とを各々特定の範囲とするとともに、SiとMgとの質量比Si/Mg を1.0 以上とした過剰Si型とする。そして更に、Cuを比較的多く含有させる。このような6000系アルミニウム合金の特定組成範囲の選択によって、高温成形性自体は阻害せずに、溶体化処理に必要な温度で高温成形を行っても、その高温下での耐力が高くすることができる。また、この高温成形後に放冷されるような緩冷却され、かつ比較的低温で短時間の人工時効硬化処理後を行なっても、人工時効硬化処理後のパネルの耐力を高くすることができる。なお、SiやMgの含有量を高めただけではこれらの効果が十分得られず、合わせてCuを比較的多量に含有しないとこれらの効果が得られない点が、この種高温成形の特異性であると言える。
【0015】
なお、本発明で言うアルミニウム合金板とは、熱延 (熱間圧延上がり) 板、冷延 (冷間圧延上がり) 板などの、溶体化および焼き入れ処理前の状態の板や、これらを溶体化および焼き入れ処理された板のことを言う。また、この溶体化および焼き入れ処理後任意の熱処理、例えば、後述する予備時効処理や、更に必要により施す時効処理などの種々の調質処理を施された板を含む。更に、この溶体化および焼き入れ処理は、パネル成形前に行うものであっても、パネル成形後に行うものであっても、板が溶体化処理温度される温度での高温成形のように、パネル成形と同時に行うものであっても良い。そして、本発明で言うアルミニウム合金板とは、板、コイル、切り板、などの適宜の形状状態を含む。
【0016】
また、本発明で言う高温成形とは、好ましくは、成形温度が成形される6000系アルミニウム合金板が溶体化処理される温度であって、460 〜550 ℃の高温領域で高い伸びの特性を生じさせて高成形性を得るような、高速超塑性成形などの高温成形のことを言う。
【0017】
本発明では、6000系アルミニウム合金板を上記特定の成分組成とする板素材側の改善だけでなく、パネルの製造方法として、これら成形側の高温成形時の成形条件および離型条件として、成形および離型温度、成形時間などを選択することによって、パネルの高温における最大流動応力を確実に25MPa 以上として成形することができる。また、更にこの高温成形後に前記緩冷却されたとしても、人工時効硬化処理を150 〜180 ℃で20〜40分間保持の条件範囲からより時効硬化しやすい条件を選択することによって、人工時効硬化処理後のパネルの0.2%耐力を確実に170MPa以上とすることができる。また、高温成形後に室温まで冷却された後、この冷却後から人工時効硬化処理まで室温で放冷される場合、その放置時間が長くなるほど、人工時効硬化処理後のパネルの耐力は低下する傾向があるため、室温での前記放置時間は短い方が好ましい。但し、放置時間が10時間以上の範囲ではその変化が小さくなる。
【0018】
【発明の実施の形態】
先ず、本発明アルミニウム合金板の化学成分組成の実施形態につき、以下に説明する。前記した通り、本発明では、アルミニウム合金板の化学成分組成を、Si:0.6〜1.3%、Mg:0.3〜0.9%、Mn:0.01 〜0.65% 、Cu:0.4〜1.0%を含み、かつSi/Mg が質量比で1.0 以上であり、残部Alおよび不可避的不純物からなるものとし、基本成分であるSiとMgの含有量とを各々特定の範囲とするとともに、SiとMgとの質量比を特定範囲とした過剰Si型とする。そして更に、Cuを比較的多く含有させる。なお、本発明での化学成分組成の% 表示は、前記請求項の% 表示も含めて、全て質量% の意味である。
【0019】
上記合金元素以外の、Cr、Zr、Ti、B 、Fe、Zn、Ni、V など、その他の合金元素は基本的には不純物元素である。しかし、リサイクルの観点から、溶解材として、高純度Al地金だけではなく、6000系合金やその他のAl合金スクラップ材、低純度Al地金などを溶解原料として使用して、本発明Al合金組成を溶製する場合には、これら他の合金元素は必然的に含まれることとなる。したがって、本発明では、目的とする本発明効果を阻害しない範囲で、これら他の合金元素が含有されることを許容する。
【0020】
各元素の好ましい含有範囲と意義、あるいは許容量について以下に説明する。
Si:0.6 〜1.3%。
Siは、高温成形後のパネルの、塗装焼き付け処理などの、前記低温短時間での人工時効処理時に、MgとともにGPゾーンなどの化合物相を形成して時効硬化能を発揮し、パネルとしての必要強度を得るための必須の元素である。具体的には、高温成形を模擬した、500 ℃で3 分間保持の熱処理後に、急冷ではなく、500 〜200 ℃の範囲を平均冷却速度10℃/s以下で室温まで放冷するような緩冷却であっても、170 ℃で30分間保持する人工時効硬化処理を施した後の0.2%耐力を170MPa以上を確保するために必須の元素である。
【0021】
これらのSiの効果を発揮するためには、更に、Si/Mg を質量比で1.0 以上とし、SiをMgに対し過剰に含有させた過剰Si型6000系Al合金組成とする。Si量が0.6%未満およびSi/Mg が質量比で1.0 未満では、前記高温成形後に放冷された際のパネルの耐力と、前記高温成形後に放冷された際の低温短時間の人工時効硬化能 (パネルの耐力) を兼備することができない。
【0022】
一方、Siが1.3%を越えて含有されると、前記高温成形後に放冷された際に、粒界上にSi、MgSiなどが析出しやすくなる。このため、特に、自動車のアウターパネル (外板) では、高温成形後のヘム (ヘミング、180 度曲げ) 加工時や曲げ加工時に、割れの起点となり易く、ヘム加工性や曲げ加工性が著しく低下する。更に、スポットなどの溶融溶接性も著しく阻害する。したがって、Siは0.6 〜1.3%の範囲とする。
【0023】
Mg:0.3〜0.9%。
Mg は固溶強化により、高温成形時の強度を確保する。具体的には、高温成形を模擬した、500 ℃の温度でかつ歪み速度:10 −1/sの条件で高温引張試験をした際の最大流動応力で25MPa 以上を確保する。また、460 〜550 ℃の高温で板を成形してパネル化する際の、このパネルの高温成形時の最大流動応力で25MPa 以上を確保する。
【0024】
また、高温成形後のパネルの、塗装焼き付け処理などの、前記低温短時間での人工時効処理時に、SiとともにGPゾーンなどの化合物相を形成して時効硬化能を発揮し、パネルとしての必要強度を得るための必須の元素である。具体的には、高温成形を模擬した、500 ℃で3 分間保持の熱処理後に、急冷ではなく、500 〜200 ℃の範囲を平均冷却速度10℃/s以下で室温まで放冷するような緩冷却であっても、170 ℃で30分間保持する人工時効硬化処理を施した後の0.2%耐力を170MPa以上を確保するために必須の元素である。
【0025】
Mgの0.3%未満の含有では、絶対量が不足するため、人工時効処理時に前記化合物相を形成できず、前記高温成形後に放冷された際の強度と、前記高温成形後に放冷された際の低温短時間の人工時効硬化能を兼備することができない。
【0026】
一方、Mgが0.9%を越えて含有されると、前記高温成形後に放冷された際に、粒界上にSi、MgSiなどが析出しやすくなる。このため、特に、自動車のアウターパネル (外板) では、高温成形後のヘム加工時や曲げ加工時に、割れの起点となり易く、ヘム加工性や曲げ加工性が著しく低下する。更に、スポットなどの溶融溶接性も著しく阻害する。したがって、Mgの含有量は、0.3 〜0.9%の範囲で、かつSi/Mg が質量比で1.0 以上となるような量とする。
【0027】
Cu:0.4〜1.0%
Cuは高温成形での高温強度を確保する重要な元素である。具体的には、高温成形を模擬した、500 ℃の温度でかつ歪み速度:10 −1/sの条件で高温引張試験をした際の最大流動応力で25MPa 以上を確保する。また、460 〜550 ℃の高温で板を成形してパネル化する際の、このパネルの高温成形時の最大流動応力で25MPa 以上を確保する。Cuは、更に高温成形後のパネルの、塗装焼き付け処理などの、前記低温短時間での人工時効処理時に、組織の結晶粒にGPゾーンなどの化合物相をAl、Si、Mgとともに形成し、人工時効硬化処理後の強度を高める効果がある。前記した通り、上記SiやMgの含有量を高めただけではこれらの効果が十分得られず、Cuを比較的多量に含有しないとこれらの効果が得られない。
【0028】
Cu含有量が0.4%未満ではこの効果がない。一方、1.0%を越えると、耐応力腐食割れ性や、塗装後の耐食性の内の耐糸さび性、また溶接性を著しく劣化させる。このため、Cuは0.4 〜1.0%の範囲とする。
【0029】
Mn:0.01 〜0.65%
Mnには、板の均質化熱処理時に分散粒子 (分散相) を生成し、これらの分散粒子には再結晶後の粒界移動を妨げる効果があるため、微細な結晶粒を得ることができる効果がある。これにより、高温成形後のパネルにおいても、肌荒れなどのない良好な表面性状を得ることができる。また、高温成形後の低温短時間での人工時効硬化処理時のパネルの耐力は、アルミニウム合金組織の結晶粒が微細なほど向上する。この点、Mn含有量が0.01% 未満ではこれらの効果が無い。
【0030】
一方、Mn含有量が多くなった場合、溶解、鋳造時に粗大なAl−Fe−Si−(Mn、Cr、Zr) 系の金属間化合物や晶析出物を生成しやすく、破壊の起点となり易いため、アルミニウム合金板の機械的性質を低下させる原因となる。また、特に、加工条件が厳しくなったフラットヘムなどの曲げ加工では、Mn含有量が0.25% を越えた場合、曲げ加工性が低下する。このため、Mnは0.01〜0.65% の範囲とする。
【0031】
Cr 、Zr。
これらCr、Zrの遷移元素には、Mnと同様、均質化熱処理時に分散粒子 (分散相) を生成し、微細な結晶粒を得ることができる効果がある。しかし、Cr、Zrも、0.15% を越える含有では、前記フラットヘム加工や曲げ加工を著しく低下させる。したがって、Cr、Zrの含有量も、0.20% 以下に規制することが好ましい。
【0032】
Ti 、B 。
Ti、B は、Ti:0.1% 、B:300ppmを各々越えて含有すると、粗大な晶出物を形成し、成形性を低下させる。但し、Ti、B には微量の含有で、鋳塊の結晶粒を微細化し、プレス成形性を向上させる効果もある。したがって、Ti:0.1% 以下、B:300ppm以下までの含有は許容する。
【0033】
Fe。
溶解原料から混入して、不純物として含まれるFeは、AlCuFe、Al12(Fe,Mn)Cu、(Fe,Mn)Alなどの晶出物を生成する。これらの晶出物は再結晶粒の核となり、Feが0.08% 以上含まれた場合に、結晶粒の粗大化を阻止して、結晶粒を50μm 以下の微細粒とする役割を果たす。しかし、一方で、これらの晶出物は、破壊靱性および疲労特性、更には、前記ヘム加工性や曲げ加工性を著しく劣化させる。これらの劣化特性は、Feの含有量が0.50% を越えると顕著になる。このため、含有させる場合のFeの含有量は0.50% 以下のできるだけ少量とすることが好ましい。
【0034】
Zn。
Znは0.5%を越えて含有されると、耐食性が顕著に低下する。したがって、Znの含有量は0.5%以下のできるだけ少量とすることが好ましい。
【0035】
以上のような本発明アルミニウム合金板の化学成分組成とすることで、高温成形性は阻害せずに、溶体化処理に必要な温度で高温成形を行っても、高温成形における高温下でのパネルの最大流動応力を高くでき、また、高温成形後に放冷するような緩冷却され、かつ比較的低温で短時間の人工時効硬化処理後を行なっても、人工時効硬化処理後のパネルの耐力を高くすることができる。
【0036】
次に、本発明における板の特性評価について以下に説明する。
本発明では、先ず、高温成形における高温下でのパネルの耐力を確保する評価基準として、溶体化処理に必要な温度での高温成形を模擬した、500 ℃の温度でかつ歪み速度:10 −1/sの条件で高温引張試験をした際の、最大流動応力が25MPa 以上であると規定する。この最大流動応力は、アルミニウム合金板の高温引張試験において、板 (試験片) 断面の応力が一定の限界値を越えた際に、断面が減少を開始し、最終的に破断 (延性破壊) に到る際の、前記断面の応力の限界値を測定するもので、高温での強度を示す指標である。したがって、この最大流動応力が高いほど、高温成形後のパネルの金型からの取り外しなどのハンドリング性が良くなる。また、最大流動応力が25MPa 以上である場合に、このハンドリング時にパネルに負荷される応力に耐えて、成形品が著しく変形したり、破断しにくくなる。
【0037】
この高温引張試験条件は、6000系アルミニウム合金板が溶体化処理される温度が成形温度であって、460 〜550 ℃の高温領域で高い伸びの特性を生じさせて高成形性を得るような、高速超塑性成形などの高温成形を模擬する条件であって、これらの高温成形に対応する条件を選択している。
【0038】
この高温引張試験をした際の最大流動応力が25MPa 未満では、高温成形の終了時において、金型から成形したパネルを離型するなど、成形パネルをハンドリングするに必要な強度が不足し、ハンドリング時に成形パネルの変形や破断などが生じる可能性もある。
【0039】
本発明では、前記基準とともに、高温成形後に緩冷却された場合でも、その後の低温短時間の人工時効硬化処理後のパネルの耐力を確保する評価基準として、500 ℃で3 分間保持した後、500 〜200 ℃の範囲を平均冷却速度10℃/s以下で室温まで放冷する熱処理後、更に170 ℃で30分間保持する人工時効硬化処理を施した後の0.2%耐力が170MPa以上であると規定する。前半の熱処理条件の規定は、上記高速超塑性成形などの高温成形を模擬する条件であって、これらの高温成形でかつ高温成形後に緩冷却された場合に対応する条件を選択している。また、後半の人工時効硬化処理条件の規定は、上記低温短時間のパネルの焼付け塗装処理を模擬し、かつ対応させた条件である。
【0040】
また、高温成形後に人工時効硬化処理まで放置される雰囲気温度および時間は人工時効硬化処理後のパネルの耐力に大きな影響を及ぼす。この点、より低温、短時間の人工時効硬化処理後のパネルの耐力を高くするためには、低温、短時間の保持 (放置) が望ましいが、本発明においては、特に、この放置を低温、短時間とせずとも、170 ℃で30分間保持する人工時効硬化処理を施した後に、170MPa以上の0.2%耐力が得られる利点もある。
【0041】
この本発明における板の特性評価基準によって、素材板側や、パネル側あるいはパネル成形側において、実際に高温成形を行わずとも、前記高温成形時の強度や人工時効硬化性などの特性が改良されているか否かが分かる。
【0042】
以下に、本発明におけるアルミニウム合金板の製造方法 (工程) につき説明する。本発明におけるアルミニウム合金板の製造方法は常法により可能である。先ず、溶解、鋳造工程は、本発明成分規格範囲内に溶解調整されたAl合金溶湯を、連続鋳造圧延法、半連続鋳造法(DC鋳造法)等の通常の溶解鋳造法を適宜選択して鋳造する。
【0043】
次いで、このAl合金鋳塊に、鋳塊の偏析除去や、合金組織の均質化、MgSi 成分の固溶などのために、500 ℃以上の温度で均質化熱処理を施す。この均質化熱処理に続く熱間圧延によって熱延板として、あるいは更に必要により冷間圧延されて、所望の板厚とされる。なお、パネルによって厚板が必要な場合には、冷間圧延を省略して、アルミニウム合金板を熱間圧延上がりとしても良い。
【0044】
過剰Si型6000系などのアルミニウム合金板は、これら冷延板乃至熱延板を、調質処理として、溶体化および焼入れ処理されて、前記した諸特性が発揮される。即ち、溶体化および焼入れ処理は、後のパネルの塗装焼き付け硬化処理などの人工時効硬化処理によりGPゾーンなどの化合物相を十分粒内に析出させるために重要な工程である。但し、前記した通り、高温成形の温度が、アルミニウム合金板が溶体化処理される温度であれば、この高温成形が溶体化処理を兼ねることができる。したがって、高温成形するアルミニウム合金板は、予め溶体化および焼入れ処理されても良く、溶体化および焼入れ処理されなくても良い。
【0045】
ただ、高温成形前の溶体化および焼入れ処理を行なうと、粗大なMgSi 金属間化合物を十分固溶させることができる。溶体化処理後に、この粗大なMgSi 金属間化合物が固溶していない場合、高温下における強度 (最大流動応力) 低下の原因となる。これらの効果を出すための溶体化処理条件は、500 〜560 ℃の温度範囲で行うのが好ましい。また、溶体化処理温度は560 ℃を超えた、局部溶融が生じるような高温に高める必要は無い。
【0046】
本発明が対象とする高温成形では、高速超塑性成形など、460 〜550 ℃の高温領域でかつ歪み速度が10−2〜10/s に達する条件での、高い伸びの特性を生じさせて高成形性を得るような、板をパネルに成形するための任意のプレス成形方法、金型成形方法が選択される。更に、車体パネルの用途や形状に応じて、高温成形前に、あるいは高温成形後に、冷間でプレス成形されたり、アウタパネルとしてのフラットヘムなどのヘミング加工や、曲げ加工、トリミング等の加工を適宜付加される場合を含む。
【0047】
但し、パネルの高温成形での高温下における最大流動応力を確実に25MPa 以上とするために、前記した通り、板素材側の改善だけでなく、パネルの製造方法として、これら高温成形時の成形条件および離型条件として、成形および離型温度、成形時間などを選択することが好ましい。また、人工時効硬化処理(ベークハード)後の耐力をできるだけ高くするためには、高温成形後の人工時効硬化処理までの放置時間は短く、放置温度は低い方が好ましい。
【0048】
この高温成形の際、溶体化処理を兼ねる場合の高温成形の昇温 (加熱) 速度は、200 ℃/ 分以上など、できるだけ早い方が結晶粒の微細化のために好ましい。この昇温速度が遅いと結晶粒が粗大に成長して、溶体化処理後のアルミニウム合金板あるいはパネルの結晶粒を20μm 以下に微細化できなくなる可能性がある。
【0049】
溶体化処理を兼ねる場合の高温成形後の冷却の際には、粒界上へのSi、MgSiの析出を抑制し、前記低温短時間の人工時効硬化処理後の耐力をより高耐力とするために、冷却速度を50℃/ 分以上の急冷とすることが好ましい。特に、アウタパネルとしてのフラットヘム加工性や曲げ加工性をり向上させるためにも、上記冷却速度が速い方が好ましい。但し、本発明では、前記した通り、高温成形後の冷却が緩冷却となっても、低温短時間の人工時効硬化処理後の耐力を高耐力とできる。
【0050】
本発明では、成形パネルの塗装焼き付け工程などの人工時効硬化処理での時効硬化性をより高めるため、溶体化処理を兼ねる場合の高温成形後の冷却後に、クラスターの生成を抑制し、GPゾーンの析出を促進するために、予備時効処理をしても良い。この予備時効処理は、50〜100 ℃、好ましくは60〜90℃の温度範囲に、1 〜24時間の必要時間保持することが好ましい。また、予備時効処理後の冷却速度は、1 ℃/hr 以下であることが好ましい。この予備時効処理として、溶体化処理を兼ねる場合の高温成形後の冷却終了温度を50〜100 ℃と高くした後に、直ちに再加熱乃至そのまま保持して行う。あるいは、溶体化処理後常温までの焼入れ処理の後に、直ちに50〜100 ℃に再加熱して行う。
【0051】
更に、室温時効抑制のために、前記予備時効処理後に、時間的な遅滞無く、比較的低温での熱処理 (人工時効処理) を行い、GPゾーンを更に生成させても良い。前記時間的な遅滞があった場合、予備時効処理後でも、時間の経過とともに室温時効 (自然時効) が生じ、この室温時効が生じた後では、前記比較的低温での熱処理による効果が発揮しにくくなる。なお、用途や必要特性に応じて、更に高温での人工時効処理や安定化処理を行い、より高強度化などを図ることなども勿論可能である。
【0052】
【実施例】
次に、本発明の実施例を説明する。表1 に示すA 〜F の本発明範囲内、G 〜L の本発明範囲外、各々2 種類の6000系のAl合金鋳塊をDC鋳造法にて溶製し、面削後に470mmtの厚みとして、昇温速度40°/hr にて加熱して550 ℃×4 時間の均質化熱処理後、この温度で熱間圧延を開始し5mmtの厚みの板に熱間圧延した。
【0053】
熱間粗圧延は、リバース式粗圧延機を用いて粗圧延した。また、続く熱間仕上げ圧延では、量産に用いる4 段4 タンデム式の仕上げ圧延機列を用いて(4回のパスによって) 仕上げ圧延してコイル化した。
その後、各熱間圧延板 (コイル) を冷間圧延し、共通して厚さ1.0mm のAl合金冷延板 (コイル) を作成した。
【0054】
更に、上記各冷延板 (冷延コイルから採取) を以下の同じ条件で調質処理したものと、調質処理しない冷延板も合わせて準備した。調質処理は、先ず、上記冷延板を570 ℃に保持した空気炉に投入し、各試験片が550 ℃の溶体化処理温度に到達した時点で10秒保持し、80℃の温水に焼き入れする処理を行った。前記焼入れ処理の際の冷却速度は200 ℃/ 秒とし、焼入れ終了温度 (焼入れ温度) は共通して80℃とし、焼入れ後にこの温度で2 時間保持する予備時効処理 (保持後は冷却速度0.6 ℃/hr で徐冷) を行った。
【0055】
これら供試板から各例とも試験片を採取し、板の圧延(L) 方向の平均結晶粒径を測定した。結果は、各発明例、比較例とも全て平均結晶粒径は50μm 以下に微細化されていた。この平均結晶粒径の測定は、アルミニウム合金板を0.05〜0.1mm 機械研磨した後電解エッチングした表面を、200 倍の光学顕微鏡を用いて観察し、前記L 方向に、ラインインターセプト法で測定する。1 測定ライン長さは0.95mmとし、1 視野当たり各3 本で合計5 視野を観察することにより、全測定ライン長さを0.95×15mmとした。
【0056】
これら調質処理後の各アルミニウム合金板および調質処理しない各アルミニウム合金板から、各例とも試験片を採取し、高速超塑性成形を評価するために、高温特性を供試板の高温引張試験により評価した。高温特性の内の、最大流動応力(MPa) 、伸び(%) の測定のための高温引張試験は温度500 ℃で行なった。そして、この温度で、昇温速度:100℃/ 分、歪み速度:10 −1/s、平行部長さ: 15mm、幅:5mm、評点間距離:10mm の試験片形状、の条件で高温引張試験を行った。また、試験片が破断するまで一定の上記歪み速度で行った。そして、これら特性は、各供試板の圧延方向に対し平行方向で測定した。これらの結果を表2 に示す。なお表2 の合金番号は表1 の合金番号に対応している。
【0057】
また、キャビティ面積率を測定して高温特性を評価した。高温成形においては、晶出物周辺および粒界3 重点などからキャビティ( 空隙) が発生する。このキャビティ発生 (量) は、高温成形品の実質的な断面積を減少させるため、成形品の機械的な性質および疲労強度を低下させる。したがって、キャビティ面積率は極力少ない方が好ましい。
【0058】
キャビティ面積率の測定は、上記温度500 ℃で高温引張試験を行なった後の、破断した試験片について行った。即ち、この試験片の板厚減少率が50% の (板厚が1/2 に減じた) 箇所の、板の圧延方向に平行な断面組織について、400 倍の光学顕微鏡を用いてキャビティを観察し、キャビティ面積率を画像処理にて測定するとともに、視野数4 視野で平均化した。これらの結果、発明例、比較例ともに差はなく、キャビティ面積率は全て1%以下の少ない値であった。
【0059】
更に、上記各試験片の高速超塑性成形後の人工時効硬化処理後の強度を評価した。このため、各例とも上記各各アルミニウム合金板から試験片を採取し、溶体化処理に必要な温度での高温成形 (高速超塑性成形) 後に急冷ではなく放冷などの緩冷却されることを模擬して、試験片を500 ℃で3 分間保持後、500 〜200 ℃の範囲を平均冷却速度5 ℃/s以下で室温まで放冷する熱処理を行なった。その後、実際の自動車パネルを想定し、高速超塑性成形後に塗装焼き付け硬化処理されることを模擬して、この熱処理後の試験片を更に170 ℃×30分の人工時効硬化処理した後 (ベークハード後) の試験片の0.2%耐力を測定した。なお、耐力測定のための引張試験はJIS Z 2201にしたがって行うとともに、試験片形状はJIS 5 号試験片で行った。また、クロスヘッド速度は5mm/分で、試験片が破断するまで一定の速度で行った。
【0060】
そして、上記人工時効硬化処理した後の試験片の、自動車のアウタパネルとして特に必要な耐デント性を更に評価した。耐デント性試験は、この試験片の中央部に対し、先端のR が50mmΦの球頭ポンチにて、245MPaの荷重を加えた際の、荷重点の凹み量を測定することにより行なった。そして、凹み量が0.3mm 未満のものを〇、凹み量が0.3mm 以上のものを×として評価した。これらの結果も表2 に示す。
【0061】
また、高温成形後にアウターパネルとしてヘム加工されることを模擬して、上記各板から採取した試験片を、500 ℃で3 分間保持後、500 〜200 ℃の範囲を平均冷却速度5 ℃/s以下で室温まで放冷する熱処理を行なった後、試験片を以下の条件でフラットヘム加工した。試験片のフラットヘム加工代 (ヘム加工後のパネルの内側に折り曲げられた端部から折り曲げ部の端部までの距離) を12mmとしてダウンフランジ工程を模擬し、試験片の一辺の縁を90度の角度となるまで折り曲げた。この際、90°曲げ半径は0.8 とした。次に、プリヘム工程を模擬して、試験片縁を更に135 °の角度まで内側に折り曲げた。その後、フラットヘム加工条件を模擬して、インナパネル (板) を前記試験片の折り曲げ部に挿入せずに、折り曲げ部を内側に180 度折り曲げる曲げ加工を行った。
【0062】
そして、このフラットヘムの縁曲部の、肌荒れ、微小な割れ、大きな割れの発生などの表面状態を目視観察した。評価は、○; 肌荒れや微小な割れも無く良好、△; 肌荒れや微小な割れが発生、×; 大きな割れが発生、とした。これらの結果も表2 に示す。
【0063】
表1 、2 から明らかな通り、本発明組成範囲内であるA 〜F の過剰Si型6000系アルミニウム合金板は、溶体化処理に必要な温度で高温成形を行っても、最大流動応力が25MPa 以上である。このため、高温成形後のパネルの金型からの取り外しなどのハンドリング性に優れる。また、高温成形後に緩冷却されたパネルであっても、そして比較的低温で短時間の人工時効硬化処理後を行なっても、人工時効硬化処理後のパネルの耐力が170MPa以上と高い。なお、高温成形前に調質処理したアルミニウム合金板例である発明例1 、2 と高温成形前に調質処理しないアルミニウム合金板例である発明例7 、8 との対比においては、調質処理しない発明例7 、8 の方が、人工時効硬化性について、発明例1 、2 よりも若干劣る。したがって、高温成形前に調質処理するか否かは、この程度の差を考慮して、パネル要求特性に合わせて、適宜選択する。
【0064】
これに対し、Cuが0.3%と下限を外れて低過ぎる合金G を用いた比較例9 は、Cuが0.4%と下限である合金B を用いた発明例2 に比して、最大流動応力が25MPa 未満であり、高温成形後のパネルのハンドリング性が著しく劣る。また、高温成形後に緩冷却されたパネルでは、比較的低温で短時間の人工時効硬化処理後の場合に、人工時効硬化処理後のパネルの耐力が170MPa未満と著しく劣る。
【0065】
Siが0.5%と下限を外れて低過ぎる合金H を用いた比較例10も、Siが0.6%と下限である合金 Cを用いた発明例3 に比して、高温成形後に緩冷却されたパネルでは比較的低温で短時間の人工時効硬化処理した場合に、人工時効硬化処理後のパネルの耐力が170MPa未満と著しく劣る。
【0066】
Mgが0.2%と下限を外れて低過ぎる合金J を用いた比較例12も、Mgが0.3%と下限である合金E を用いた発明例5 に比して、最大流動応力が25MPa 未満であり、高温成形後のパネルのハンドリング性が著しく劣る。また、高温成形後に緩冷却されたパネルでは、比較的低温で短時間の人工時効硬化処理後の場合に、人工時効硬化処理後のパネルの耐力が170MPa未満と著しく劣る。
【0067】
Siが1.4%と上限を外れて高過ぎる合金I を用いた比較例11や、Mgが1.0%と上限を外れて高過ぎる合金K を用いた比較例13は、最大流動応力が25MPa 以上である。しかし、比較例11と比較例13は、は自動車アウタパネルとして使用される際に必要なヘム加工性が、Siが1.3%と上限値である合金D を用いた発明例4 や、Mgが1.0%と上限値である合金F を用いた発明例6 に比して、著しく劣る。また、比較例13は、人工時効硬化処理後のパネルの0.2%耐力が170MPa未満である。
【0068】
また、Siを1.3%と上限値まで増やし、Mgを1.0%と上限値まで増やしても、Cuを有効量乃至実質量含まない合金L を用いた比較例14は、最大流動応力が25MPa 未満であり、高温時の耐力が発明例に比して著しく劣る。また、高温成形後に緩冷却されたパネルでは、比較的低温で短時間の人工時効硬化処理後の場合に、人工時効硬化処理後のパネルの0.2%耐力が170MPa未満と著しく劣る。したがって、本発明の課題に対する、SiやMgの増量効果の低さに比べて、Cuの格段に優れた特異な効果が分かる。また、これらの結果から、高温強度、高温成形後のパネルのハンドリング性、高温成形後に緩冷却された場合の比較的低温で短時間の人工時効硬化性、あるいはヘム加工性に対する、本発明成分組成範囲の臨界的な意義が分かる。
【0069】
【表1】
【0070】
【表2】
【0071】
【発明の効果】
本発明によれば、溶体化処理に必要な温度で高温成形を行っても、高温成形温度下におけるパネル強度が高く、また、この高温成形後に緩冷却を行って、かつ比較的低温で短時間の人工時効硬化処理後を行なっても、人工時効硬化処理後のパネルの耐力が高い高温成形用6000系アルミニウム合金板およびアルミニウム合金パネルの製造方法を提供することができる。しかも、このアルミニウム合金板を従来の板製造工程を変更せずに製造することができる。したがって、6000系アルミニウム合金板のパネル成形用途への拡大を図ることができる点で、多大な工業的な価値を有するものである。
[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing an aluminum alloy plate and an aluminum alloy panel for high-temperature forming (hereinafter, aluminum is also referred to as Al).
[0002]
[Prior art]
Conventionally, in order to form an aluminum alloy plate into a panel having a difficult-to-process shape, the aluminum alloy plate is heated to produce high elongation characteristics in a high temperature range of 460 to 550 ° C. to obtain high formability. High-temperature forming methods such as high-speed superplastic forming are being studied.
[0003]
As these aluminum alloy sheets for high-temperature forming, 5000 series (hereinafter simply referred to as 5000 series) Al-Mg based aluminum alloys in AA to JIS standards are mainly used. For this reason, many Al-Mg based aluminum alloys for high-speed superplastic forming have been conventionally developed and proposed.
[0004]
On the other hand, in particular, Al-Mg-Si based AA or 6000 series (hereinafter simply referred to as 6000 series) which is excellent in baking hardening property (artificial aging hardening property) at the time of paint baking such as automobile panels. The use of aluminum alloy sheets is also being studied in the field of high-temperature forming. These 6000 series aluminum alloy sheets have a relatively small amount of alloying elements as compared with other 5000 series aluminum alloys having a large amount of alloying elements. For this reason, when these 6000 series aluminum alloy panel scraps are reused as an Al alloy melting material (melting raw material), the original 6000 series aluminum alloy ingot is easily obtained and the recyclability is excellent. is there.
[0005]
As a proposal example of a 6000 series aluminum alloy sheet for the high temperature forming field, for example, the average crystal grain size of the 6000 series aluminum alloy sheet is set to 15 to 120 μm, and the strain rate and the forming temperature during high-speed superplastic forming are specified. It has been proposed to control the relationship to obtain high elongation during high-speed superplastic forming and to perform T6 treatment after forming to obtain a high tensile strength of 300 MPa or more (see Patent Document 1). Also, a 6000 series aluminum alloy plate that has not been subjected to a solution treatment or the like may be subjected to blow molding at a temperature required for the solution treatment, and then subjected to a tempering treatment to obtain a high yield strength of 200 MPa or more. It has been proposed (see Patent Document 2).
[0006]
[Patent Document 1]
JP-A-11-131165
[Patent Document 2]
JP 2001-58221A
[0007]
[Problems to be solved by the invention]
However, when high-speed superplastic forming is performed at a temperature required for solution treatment as in Patent Document 2, there is a problem that the strength (proof strength) of the 6000 series aluminum alloy panel at this high temperature is significantly reduced. This is the same even when a high elongation is obtained during high-speed superplastic forming by controlling the strain rate and the forming temperature during high-speed superplastic forming in a specific relationship as in Patent Document 1.
[0008]
For this reason, the strength (proof strength) required for handling the molded panel, such as releasing the panel molded from the mold at the end of the high-speed superplastic molding, which neither Patent Documents 1 nor 2 intended, cannot be obtained. , A new problem arises. There is also a new problem that the molded panel is deformed during handling.
[0009]
Further, even if an artificial age hardening treatment is performed after molding, there is a new problem that a high yield strength of 200 MPa or more cannot be obtained. In this regard, Patent Literature 1 also states that an artificial age hardening treatment can be performed after molding to obtain a high yield strength of 200 MPa or more. However, the conditions of the artificial age hardening treatment are a relatively high temperature of 175 ° C. and a long time of 10 hours. Further, Patent Document 1 does not disclose the yield strength of the panel after high-speed superplastic forming. On the other hand, the actual conditions of the baking treatment of an automobile panel are as follows: with the improvement of the paint and the efficiency of the automobile production process, the artificial panel is kept at a temperature of 150 to 180 ° C. for 20 to 40 minutes. Age hardening is the mainstream. In such actual artificial aging hardening treatment at a relatively low temperature for a short period of time, the 6000 series aluminum alloy panel after forming cannot attain a high yield strength of 200 MPa or more.
[0010]
This point is completely the same in Patent Document 2. That is, Patent Document 2 discloses that a heat history at the time of molding is simulated, a solution treatment is performed at 530 ° C. for 14 minutes at a high temperature for a long time, and then cooled at a cooling rate of 2 ° C./sec. It is said that a high yield strength of 170 MPa or more is obtained by artificial aging hardening conditions at a relatively high temperature and for a long period of time, ie, holding at 180 ° C. for 40 minutes after being left for a period of time (see FIG. Read from the relationship between time and proof stress). Therefore, if the molding time is shortened to improve the productivity and / or the artificial aging hardening treatment is performed at a lower temperature for a shorter time, the 6000 series aluminum alloy panel after molding has a high yield strength of 200 MPa or more. You can't get it. The tendency that a high yield strength cannot be obtained after the artificial aging hardening treatment is remarkable when low-temperature, short-time artificial aging hardening treatment is performed after cooling at a low temperature or the like after high-temperature molding.
[0011]
The present invention has been made in view of such circumstances, and its purpose is to provide a high yield strength even at a high temperature at a temperature necessary for the solution treatment, Manufacture of 6000 series aluminum alloy sheets and aluminum alloy panels for high-temperature forming with high yield strength of panels after artificial aging and hardening even after slow cooling after forming and artificial aging and hardening at a relatively low temperature for a short time It seeks to provide a way.
[0012]
[Means for Solving the Problems]
In order to achieve this object, the gist of the Al-Mg-Si-based aluminum alloy sheet for high-temperature forming of the present invention is as follows: Si: 0.6 to 1.3%, Mg: 0.3 to 0.9%, Mn: Al-Mg-Si containing 0.01 to 0.65%, Cu: 0.4 to 1.0%, and having a mass ratio of Si / Mg of 1.0 or more, with the balance being Al and unavoidable impurities Aluminum alloy plate at a temperature of 500 ° C. and a strain rate of 10 -1 The maximum flow stress in the high temperature tensile test under the condition of / g / s is 25 MPa or more, and after holding at 500 ° C. for 3 minutes, the range of 500 to 200 ° C. is released to room temperature at an average cooling rate of 10 ° C./s or less. The aluminum alloy sheet has a characteristic that the 0.2% proof stress after performing the artificial aging hardening treatment at 170 ° C. for 30 minutes after the cooling heat treatment is 170 MPa or more.
[0013]
The gist of the method for manufacturing the aluminum alloy panel of the present invention for achieving this object is as follows: Si: 0.6 to 1.3%, Mg: 0.3 to 0.9%, Mn: 0.01 to Al-Mg-Si-based aluminum alloy sheet containing 0.65%, Cu: 0.4-1.0%, and having a mass ratio of Si / Mg of 1.0 or more, with the balance being Al and unavoidable impurities Is formed at a high temperature of 460 to 550 ° C. to form a panel, the maximum flow stress of the panel at the time of the high temperature forming is set to 25 MPa or more, and the panel after the high temperature forming is formed at 150 to 180 ° C. at 20 ° C. An artificial age hardening treatment for holding for up to 40 minutes is performed, and the 0.2% proof stress of the panel after the artificial age hardening treatment is set to 170 MPa or more.
[0014]
In the present invention, the contents of Si and Mg, which are the basic components of the 6000 series aluminum alloy plate, are each set to a specific range, and the excess Si type in which the mass ratio Si / Mg of Si and Mg is 1.0 or more. And Further, Cu is contained in a relatively large amount. By selecting such a specific composition range of the 6000 series aluminum alloy, the high-temperature formability itself is not hindered, and even if the high-temperature forming is performed at the temperature required for the solution treatment, the proof stress at the high temperature is increased. Can be. Further, even if the artificial aging hardening treatment is performed at a relatively low temperature for a short time at a relatively low temperature such as being left to cool after the high-temperature molding, the yield strength of the panel after the artificial aging hardening treatment can be increased. It is to be noted that these effects cannot be sufficiently obtained only by increasing the content of Si or Mg, and that these effects cannot be obtained unless the Cu is contained in a relatively large amount. It can be said that
[0015]
The aluminum alloy plate referred to in the present invention is a plate in a state before solution treatment and quenching treatment, such as a hot-rolled (hot-rolled) plate, a cold-rolled (cold-rolled) plate, and the like. Refers to a plate that has been tempered and quenched. Further, it includes a plate that has been subjected to various heat treatments, such as a preliminary aging treatment described below and further an aging treatment to be performed as necessary, for example, after the solution treatment and the quenching treatment. Further, the solution treatment and the quenching treatment may be performed before the panel molding or after the panel molding, as in the case of the high-temperature molding at a temperature at which the plate is subjected to the solution treatment temperature. It may be performed simultaneously with molding. The term “aluminum alloy plate” as used in the present invention includes appropriate shapes such as a plate, a coil, and a cut plate.
[0016]
In the present invention, the high-temperature forming is preferably a forming temperature at which a 6000 series aluminum alloy sheet to be formed is subjected to a solution treatment, and produces high elongation characteristics in a high temperature range of 460 to 550 ° C. High-temperature forming such as high-speed superplastic forming in which high formability is obtained.
[0017]
In the present invention, not only the plate material side having the 6000 series aluminum alloy plate having the specific component composition described above is improved, but also as a manufacturing method of a panel, the forming conditions and the mold release conditions at the time of high-temperature forming of these forming sides include forming and releasing conditions. By selecting a release temperature, a molding time, and the like, it is possible to reliably form a panel with a maximum flow stress at a high temperature of 25 MPa or more. Further, even if the above-mentioned slow cooling is performed after the high-temperature molding, the artificial aging hardening treatment is performed by selecting a condition that makes the age hardening easier from a condition of holding at 150 to 180 ° C. for 20 to 40 minutes. The 0.2% proof stress of the subsequent panel can reliably be 170 MPa or more. In addition, when cooled to room temperature after high-temperature molding, and then allowed to cool to room temperature from this cooling to artificial age hardening treatment, the longer the standing time, the lower the yield strength of the panel after artificial age hardening treatment. For this reason, it is preferable that the standing time at room temperature is short. However, the change is small when the leaving time is 10 hours or more.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
First, an embodiment of the chemical composition of the aluminum alloy sheet of the present invention will be described below. As described above, in the present invention, the chemical composition of the aluminum alloy plate is set to be: Si: 0.6 to 1.3%, Mg: 0.3 to 0.9%, Mn: 0.01 to 0.65%, Cu: contains 0.4 to 1.0%, and the mass ratio of Si / Mg is 1.0 or more, and the balance is made up of Al and unavoidable impurities. In a specific range, and the excess Si type in which the mass ratio of Si to Mg is in a specific range. Further, Cu is contained in a relatively large amount. In the present invention, the expression “%” of the chemical component composition means “% by mass” including the expression “%” in the claims.
[0019]
Other alloying elements other than the above alloying elements, such as Cr, Zr, Ti, B 2, Fe, Zn, Ni, and V, are basically impurity elements. However, from the viewpoint of recycling, not only high-purity Al metal but also 6000 series alloy and other Al alloy scrap materials and low-purity Al metal as melting materials are used as melting materials, and the Al alloy composition of the present invention is used. When these are melted, these other alloying elements are inevitably included. Therefore, the present invention allows the inclusion of these other alloy elements as long as the desired effect of the present invention is not impaired.
[0020]
The preferable content range and significance of each element, or the allowable amount will be described below.
Si: 0.6 to 1.3%.
Si forms a compound phase such as a GP zone together with Mg during the artificial aging treatment at a low temperature and in a short time, such as a paint baking treatment, after the high-temperature molding of the panel. It is an essential element for obtaining strength. More specifically, after a heat treatment simulating high-temperature molding and holding at 500 ° C. for 3 minutes, rather than quenching, gentle cooling such as cooling to a room temperature in the range of 500 to 200 ° C. at an average cooling rate of 10 ° C./s or less to room temperature. However, it is an essential element for ensuring a 0.2% proof stress of 170 MPa or more after performing an artificial aging hardening treatment at 170 ° C. for 30 minutes.
[0021]
In order to exhibit the effect of Si, the excess Si-type 6000 series Al alloy composition containing Si / Mg in a mass ratio of 1.0 or more and Si in excess of Mg is used. When the amount of Si is less than 0.6% and the mass ratio of Si / Mg is less than 1.0, the yield strength of the panel when it is allowed to cool after the high-temperature molding and the low-temperature short-time when it is allowed to cool after the high-temperature molding. Cannot have the artificial age hardening ability (panel strength)
[0022]
On the other hand, when Si is contained in excess of 1.3%, Si, MgSi, and the like are likely to precipitate on the grain boundaries when allowed to cool after the high-temperature molding. For this reason, especially in the outer panel (outer plate) of an automobile, it tends to be a starting point of cracking during hem (hemming, bending at 180 degrees) or bending after high-temperature molding, and the hemability and bendability are significantly reduced. I do. Furthermore, the weldability of spots and the like is significantly impaired. Therefore, Si is set in the range of 0.6 to 1.3%.
[0023]
Mg: 0.3-0.9%.
Mg secures the strength during high-temperature molding by solid solution strengthening. Specifically, at a temperature of 500 ° C. and a strain rate of 10 to simulate high-temperature molding. -1 The maximum flow stress when performing a high-temperature tensile test under the condition of / s is 25 MPa or more. Further, when forming a panel at a high temperature of 460 to 550 ° C. to form a panel, the maximum flow stress of the panel at the time of high temperature molding is 25 MPa or more.
[0024]
In addition, during the artificial aging treatment at a low temperature and in a short time, such as a paint baking treatment, after high-temperature molding, a compound phase such as a GP zone is formed together with Si to exhibit age hardening ability, and the required strength as a panel is obtained. Is an essential element for obtaining More specifically, after a heat treatment simulating high-temperature molding and holding at 500 ° C. for 3 minutes, rather than quenching, gentle cooling such as cooling to a room temperature in the range of 500 to 200 ° C. at an average cooling rate of 10 ° C./s or less to room temperature. However, it is an essential element for ensuring a 0.2% proof stress of 170 MPa or more after performing an artificial aging hardening treatment at 170 ° C. for 30 minutes.
[0025]
If the content of Mg is less than 0.3%, the absolute amount is insufficient, so that the compound phase cannot be formed during the artificial aging treatment, and the strength when cooled after the high-temperature molding and the cooling after the high-temperature molding. It cannot have the artificial aging hardening ability for short time at low temperature.
[0026]
On the other hand, when Mg is contained in an amount exceeding 0.9%, Si, MgSi, and the like are liable to precipitate on the grain boundaries when cooled after the high-temperature molding. For this reason, in particular, the outer panel (outer plate) of an automobile tends to be a starting point of a crack at the time of hemming or bending after high-temperature molding, and the hemmability and bendability are significantly reduced. Furthermore, the weldability of spots and the like is significantly impaired. Therefore, the content of Mg is in the range of 0.3 to 0.9%, and the amount is such that the mass ratio of Si / Mg is 1.0 or more.
[0027]
Cu: 0.4 to 1.0%
Cu is an important element for ensuring high-temperature strength in high-temperature molding. Specifically, at a temperature of 500 ° C. and a strain rate of 10 to simulate high-temperature molding. -1 The maximum flow stress when performing a high-temperature tensile test under the condition of / s is 25 MPa or more. Further, when forming a panel at a high temperature of 460 to 550 ° C. to form a panel, the maximum flow stress of the panel at the time of high temperature molding is 25 MPa or more. Cu further forms a compound phase such as a GP zone in the crystal grains of the structure together with Al, Si and Mg during the artificial aging treatment at a low temperature and in a short time, such as a paint baking treatment, after the panel is formed at a high temperature, and the artificial It has the effect of increasing the strength after age hardening. As described above, these effects cannot be sufficiently obtained only by increasing the contents of Si and Mg, and these effects cannot be obtained unless Cu is contained in a relatively large amount.
[0028]
When the Cu content is less than 0.4%, this effect is not obtained. On the other hand, if it exceeds 1.0%, the stress corrosion cracking resistance, the rust resistance among the corrosion resistance after painting, and the weldability are significantly deteriorated. Therefore, Cu is set in the range of 0.4 to 1.0%.
[0029]
Mn: 0.01 to 0.65%
Mn produces dispersed particles (dispersed phase) during the homogenizing heat treatment of the plate, and these dispersed particles have the effect of preventing the movement of the grain boundary after recrystallization, so that fine crystal grains can be obtained. There is. As a result, it is possible to obtain a good surface property without roughening even in the panel after high-temperature molding. Further, the yield strength of the panel at the time of artificial aging hardening at a low temperature for a short time after high-temperature molding is improved as the crystal grains of the aluminum alloy structure become finer. In this regard, if the Mn content is less than 0.01%, these effects are not obtained.
[0030]
On the other hand, when the Mn content is large, coarse Al-Fe-Si- (Mn, Cr, Zr) -based intermetallic compounds and crystal precipitates are easily formed during melting and casting, and are likely to be the starting points of fracture. This causes the mechanical properties of the aluminum alloy plate to deteriorate. In particular, in bending such as flat hem under severe processing conditions, when the Mn content exceeds 0.25%, bending workability decreases. For this reason, Mn is set in the range of 0.01 to 0.65%.
[0031]
Cr, Zr.
Similar to Mn, these transition elements of Cr and Zr have the effect of forming dispersed particles (dispersed phase) during the homogenization heat treatment, thereby obtaining fine crystal grains. However, if the content of Cr and Zr exceeds 0.15%, the flat hemming and bending are significantly reduced. Therefore, it is preferable that the contents of Cr and Zr are also restricted to 0.20% or less.
[0032]
Ti, B.
If the contents of Ti and B exceed 0.1% of Ti and 300 ppm of B, respectively, a coarse crystallized substance is formed and the formability is reduced. However, a small amount of Ti and B 2 has the effect of refining the crystal grains of the ingot and improving press formability. Therefore, the content of Ti: 0.1% or less and B: 300 ppm or less is permitted.
[0033]
Fe.
Fe mixed as an impurity and contained as impurities is Al 7 Cu 2 Fe, Al 12 (Fe, Mn) 3 Cu 2 , (Fe, Mn) Al 6 Produces crystals such as. These crystallized substances serve as nuclei of recrystallized grains, and when Fe is contained in an amount of 0.08% or more, they play a role in preventing the crystal grains from becoming coarse and making the crystal grains finer than 50 μm. However, on the other hand, these crystallized substances significantly degrade the fracture toughness and fatigue properties, as well as the hemability and bendability. These deterioration characteristics become remarkable when the content of Fe exceeds 0.50%. Therefore, when Fe is contained, the content of Fe is preferably as small as possible, that is, 0.50% or less.
[0034]
Zn.
If Zn is contained in excess of 0.5%, the corrosion resistance is significantly reduced. Therefore, the content of Zn is preferably as small as 0.5% or less.
[0035]
By using the chemical composition of the aluminum alloy sheet of the present invention as described above, the high-temperature formability is not hindered, and even if the high-temperature forming is performed at a temperature required for the solution treatment, the panel is formed at a high temperature in the high-temperature forming. The maximum flow stress of the panel can be increased, and even if the artificial aging hardening is performed at a relatively low temperature for a short time at a relatively low temperature, such as cooling after high-temperature molding, the yield strength of the panel after the artificial aging hardening is improved. Can be higher.
[0036]
Next, the evaluation of the properties of the plate according to the present invention will be described below.
In the present invention, first, as an evaluation criterion for securing the proof stress of the panel at a high temperature in the high-temperature forming, at a temperature of 500 ° C. and a strain rate of 10 to simulate high-temperature forming at a temperature necessary for solution treatment. -1 / S is defined as a maximum flow stress of 25 MPa or more when subjected to a high temperature tensile test. The maximum flow stress occurs in a high-temperature tensile test of an aluminum alloy plate when the cross-section of the plate (specimen) exceeds a certain limit value, the cross-section starts to decrease and finally breaks (ductile fracture). It measures the limit value of the stress of the cross section at the time of reaching, and is an index indicating the strength at high temperature. Therefore, the higher the maximum flow stress, the better the handling properties such as removal of the panel from the mold after high-temperature molding. Further, when the maximum flow stress is 25 MPa or more, the molded product is hardly deformed or broken easily withstands the stress applied to the panel during the handling.
[0037]
The conditions for the high-temperature tensile test are such that the temperature at which the 6000 series aluminum alloy sheet is subjected to a solution treatment is a forming temperature, and high elongation characteristics are obtained in a high temperature range of 460 to 550 ° C. to obtain high formability. Conditions for simulating high-temperature forming such as high-speed superplastic forming and the conditions corresponding to these high-temperature forming are selected.
[0038]
If the maximum flow stress during this high-temperature tensile test is less than 25 MPa, the strength required for handling the molded panel is insufficient at the end of the high-temperature molding, such as releasing the panel molded from the mold. Deformation or breakage of the molded panel may occur.
[0039]
In the present invention, in addition to the above-described criteria, even when the panel is slowly cooled after the high-temperature molding, the panel is held at 500 ° C. for 3 minutes as an evaluation criterion for securing the yield strength of the panel after the artificial aging hardening for a short time at a low temperature. 0.2% proof stress of 170 MPa or more after heat treatment for cooling to room temperature at an average cooling rate of 10 ° C./s or less to a temperature range of 200 ° C. to 200 ° C., and further performing artificial age hardening treatment at 170 ° C. for 30 minutes. It is prescribed. The heat treatment conditions in the first half are conditions simulating high-temperature forming such as the high-speed superplastic forming described above, and conditions corresponding to these high-temperature forming and a case where slow cooling is performed after the high-temperature forming are selected. The conditions for the artificial aging hardening treatment in the latter half are conditions that simulate and correspond to the above-mentioned baking coating of the panel at a low temperature for a short time.
[0040]
Further, the ambient temperature and the time left until the artificial age hardening treatment after the high temperature molding have a great influence on the yield strength of the panel after the artificial age hardening treatment. In this regard, in order to increase the yield strength of the panel after the artificial aging hardening treatment at a lower temperature and for a shorter time, it is desirable to hold (leave) at a lower temperature for a shorter time. Even if the time is not short, there is an advantage that a 0.2% proof stress of 170 MPa or more can be obtained after performing the artificial age hardening treatment at 170 ° C. for 30 minutes.
[0041]
According to the characteristic evaluation criteria of the plate in the present invention, on the material plate side, the panel side or the panel forming side, even if the high-temperature molding is not actually performed, the characteristics such as the strength at the time of the high-temperature molding and the artificial age hardening property are improved. You can see if it is.
[0042]
Hereinafter, a method (step) of manufacturing an aluminum alloy plate according to the present invention will be described. The method for producing an aluminum alloy plate in the present invention can be performed by a conventional method. First, in the melting and casting process, a normal melting and casting method such as a continuous casting and rolling method and a semi-continuous casting method (DC casting method) is appropriately selected from an Al alloy melt that is adjusted to be within the component range of the present invention. To cast.
[0043]
Next, segregation removal of the ingot, homogenization of the alloy structure, Mg 2 A homogenizing heat treatment is performed at a temperature of 500 ° C. or more to form a solid solution of the Si component. A hot rolled sheet is obtained by hot rolling following the homogenizing heat treatment, or further cold-rolled as necessary to obtain a desired sheet thickness. When a thick plate is required depending on the panel, the cold rolling may be omitted, and the aluminum alloy plate may be hot-rolled.
[0044]
An aluminum alloy plate such as an excess Si type 6000 series is subjected to a solution treatment and a quenching treatment of the cold-rolled sheet or the hot-rolled sheet as a tempering treatment, so that the above-described various properties are exhibited. That is, the solution treatment and the quenching treatment are important steps in order to sufficiently precipitate the compound phase such as the GP zone in the grains by the artificial aging hardening treatment such as the paint baking hardening treatment of the subsequent panel. However, as described above, if the temperature of the high-temperature forming is a temperature at which the aluminum alloy sheet is subjected to the solution treatment, the high-temperature forming can also serve as the solution treatment. Therefore, the aluminum alloy plate to be formed at a high temperature may be subjected to a solution treatment and a quenching treatment in advance or may not be subjected to a solution treatment and a quenching treatment.
[0045]
However, when solution treatment and quenching before high-temperature forming are performed, coarse Mg 2 The Si intermetallic compound can be sufficiently dissolved. After solution treatment, this coarse Mg 2 If the Si intermetallic compound does not form a solid solution, it causes a decrease in strength (maximum flow stress) at high temperatures. Solution treatment conditions for achieving these effects are preferably performed in a temperature range of 500 to 560 ° C. Further, it is not necessary to raise the solution treatment temperature to a temperature higher than 560 ° C. or a temperature at which local melting occurs.
[0046]
In the high-temperature molding targeted by the present invention, a high-speed superplastic molding is performed in a high-temperature region of 460 to 550 ° C. and a strain rate of 10 -2 -10 0 Any press forming method and die forming method for forming a plate into a panel is selected so as to produce high elongation characteristics and obtain high formability under the condition of / s. Furthermore, depending on the use and shape of the body panel, before or after high-temperature molding, cold press molding, hemming processing such as flat hem as an outer panel, bending processing, trimming, etc. may be appropriately performed. Including the case where it is added.
[0047]
However, in order to ensure that the maximum flow stress at a high temperature in the high-temperature molding of the panel is 25 MPa or more, as described above, not only the improvement of the plate material side, but also the molding conditions during the high-temperature molding as a panel manufacturing method. It is preferable to select molding and release temperatures, molding times, and the like as mold release conditions. Further, in order to increase the yield strength after the artificial age hardening treatment (baked hard) as much as possible, the standing time until the artificial age hardening treatment after high-temperature molding is short, and the lower the leaving temperature, the better.
[0048]
In this high-temperature forming, the temperature rising (heating) rate of the high-temperature forming in the case of also performing the solution treatment is preferably as fast as possible, for example, 200 ° C./min or more, in order to refine the crystal grains. If the rate of temperature rise is low, the crystal grains grow coarsely, and it may not be possible to refine the crystal grains of the aluminum alloy plate or panel after the solution treatment to 20 μm or less.
[0049]
At the time of cooling after high-temperature forming when also serving as a solution treatment, in order to suppress the precipitation of Si and MgSi on the grain boundaries and to increase the proof stress after the low-temperature short-time artificial aging hardening treatment to a higher proof stress. Preferably, the cooling rate is 50 ° C./min or more. In particular, it is preferable that the cooling rate be high in order to improve the flat hemmability and bending workability of the outer panel. However, in the present invention, as described above, even if the cooling after high-temperature molding is slow cooling, the yield strength after low-temperature, short-time artificial age hardening treatment can be made high.
[0050]
In the present invention, in order to further enhance age hardening in an artificial age hardening treatment such as a paint baking step of a molded panel, the formation of clusters is suppressed after cooling after high-temperature molding when also serving as a solution treatment, and the GP zone is formed. Preliminary aging treatment may be performed to promote precipitation. This preliminary aging treatment is preferably carried out in a temperature range of 50 to 100 ° C., preferably 60 to 90 ° C., for a required time of 1 to 24 hours. Further, the cooling rate after the pre-aging treatment is preferably 1 ° C./hr or less. As the preliminary aging treatment, the cooling end temperature after high-temperature molding in the case of also performing the solution treatment is increased to 50 to 100 ° C., and then immediately reheated or held as it is. Alternatively, after the quenching treatment up to room temperature after the solution treatment, reheating to 50 to 100 ° C. is performed immediately.
[0051]
Further, in order to suppress room temperature aging, heat treatment at a relatively low temperature (artificial aging treatment) may be performed without time delay after the preliminary aging treatment to further generate a GP zone. In the case of the time delay, even after the preliminary aging treatment, room temperature aging (natural aging) occurs with the passage of time, and after the room temperature aging occurs, the effect of the heat treatment at the relatively low temperature is exhibited. It becomes difficult. In addition, it is of course possible to further increase the strength by performing artificial aging treatment or stabilization treatment at a higher temperature, depending on the use or required characteristics.
[0052]
【Example】
Next, examples of the present invention will be described. Within the range of the present invention of A to F shown in Table 1, outside the range of the present invention of G to L, each of two types of 6000 series Al alloy ingots was melted by DC casting, and the thickness was 470 mmt after facing. After a homogenizing heat treatment at 550 ° C. × 4 hours by heating at a heating rate of 40 ° / hr, hot rolling was started at this temperature and hot-rolled to a plate having a thickness of 5 mmt.
[0053]
In the hot rough rolling, rough rolling was performed using a reverse type rough rolling mill. Further, in the subsequent hot finish rolling, a coil was formed by finish rolling (by four passes) using a four-stage four-tandem finishing rolling mill train used for mass production.
Thereafter, each hot-rolled plate (coil) was cold-rolled to prepare a 1.0-mm-thick Al alloy cold-rolled plate (coil) in common.
[0054]
Further, the above-mentioned cold-rolled sheets (collected from the cold-rolled coils) were tempered under the same conditions as described below, and cold-rolled sheets not tempered were also prepared. In the temper treatment, first, the cold-rolled sheet was put into an air furnace maintained at 570 ° C., and when each specimen reached the solution treatment temperature of 550 ° C., the specimen was held for 10 seconds and baked in hot water of 80 ° C. The processing to put was performed. A pre-aging treatment in which the cooling rate during the quenching treatment is 200 ° C./sec, the quenching end temperature (quenching temperature) is 80 ° C., and the quenching is maintained at this temperature for 2 hours (after cooling, the cooling rate is 0.2 ° C. 6 ° C./hr).
[0055]
In each case, a test piece was taken from each of the test plates, and the average crystal grain size in the rolling (L) direction of the plate was measured. As a result, in each of the invention examples and the comparative examples, the average crystal grain size was reduced to 50 μm or less. The average crystal grain size was measured by observing the surface of the aluminum alloy plate which had been mechanically polished and mechanically polished and then subjected to electrolytic etching using a 200-fold optical microscope, and in the L direction, a line intercept method. Measure. 1 The measurement line length was 0.95 mm, and the total measurement line length was 0.95 × 15 mm by observing a total of five visual fields with three lines per visual field.
[0056]
From each aluminum alloy plate after tempering treatment and each aluminum alloy plate without tempering treatment, test specimens were collected in each case, and high-temperature properties were evaluated in order to evaluate high-speed superplastic forming. Was evaluated. Among the high temperature properties, the high temperature tensile test for measuring the maximum flow stress (MPa) and elongation (%) was performed at a temperature of 500 ° C. Then, at this temperature, the heating rate: 100 ° C./min, the strain rate: 10 -1 / S, parallel part length: 15 mm, width: 5 mm, distance between evaluation points: 10 mm A high temperature tensile test was performed under the following conditions: The test was performed at a constant strain rate until the test piece broke. And these characteristics were measured in the direction parallel to the rolling direction of each test plate. Table 2 shows the results. The alloy numbers in Table 2 correspond to the alloy numbers in Table 1.
[0057]
Further, the cavity area ratio was measured to evaluate the high temperature characteristics. In high-temperature molding, cavities (voids) are formed around the crystallized material and at the triple point of the grain boundary. This cavity formation (amount) reduces the mechanical properties and fatigue strength of the molded article, since it reduces the substantial cross-sectional area of the hot molded article. Therefore, the cavity area ratio is preferably as small as possible.
[0058]
The measurement of the cavity area ratio was performed on the fractured test piece after performing the high temperature tensile test at the above temperature of 500 ° C. That is, the cavity was observed using a 400-fold optical microscope with respect to the cross-sectional structure parallel to the rolling direction of the plate at the place where the reduction in the thickness of the test piece was 50% (the thickness was reduced to 2). Then, the cavity area ratio was measured by image processing, and averaged over four visual fields. As a result, there was no difference between the invention example and the comparative example, and the cavity area ratios were all small values of 1% or less.
[0059]
Further, the strength of each of the test pieces after artificial age hardening after high-speed superplastic forming was evaluated. For this reason, in each case, a test piece was taken from each of the above aluminum alloy plates, and after being subjected to high-temperature forming (high-speed superplastic forming) at the temperature required for the solution treatment, it was to be slowly cooled rather than quenched. After simulating, the test piece was kept at 500 ° C. for 3 minutes, and then subjected to a heat treatment in which the test piece was allowed to cool to a room temperature in the range of 500 to 200 ° C. at an average cooling rate of 5 ° C./s or less. Then, assuming an actual automobile panel, simulating that the paint was baked and hardened after high-speed superplastic forming, the test piece after this heat treatment was further subjected to artificial aging hardening at 170 ° C. for 30 minutes (baked hard After that, the 0.2% proof stress of the test piece was measured. In addition, the tensile test for proof stress measurement was performed in accordance with JIS Z 2201, and the test piece shape was a JIS No. 5 test piece. The crosshead speed was 5 mm / min, and the test was performed at a constant speed until the test piece broke.
[0060]
The test piece after the artificial age hardening treatment was further evaluated for dent resistance particularly required as an outer panel of an automobile. The dent resistance test was performed by measuring the amount of dent at the load point when a load of 245 MPa was applied to the center of the test piece using a ball-head punch having a tip R of 50 mmΦ. Then, those having a dent amount of less than 0.3 mm were evaluated as Δ, and those having a dent amount of 0.3 mm or more were evaluated as x. Table 2 also shows these results.
[0061]
After simulating that the outer panel was hemmed after the high-temperature molding, the test pieces taken from each of the above plates were held at 500 ° C. for 3 minutes, and then the range of 500 to 200 ° C. was averaged at a cooling rate of 5 ° C./s. After performing a heat treatment for cooling to room temperature below, the test piece was flat-hemmed under the following conditions. Simulate the down-flanging process by setting the flat hemming allowance of the test piece (distance from the edge bent inside the panel after hemming to the end of the bent portion) to 12 mm, and set the edge of one side of the test piece to 90 degrees. Was bent until the angle of. At this time, the 90 ° bending radius was 0.8. Next, the edge of the test piece was further bent inward to an angle of 135 ° to simulate the prehem process. After that, by simulating the flat hemming conditions, the inner panel (plate) was bent by bending the bent portion 180 degrees inward without inserting the inner panel (plate) into the bent portion of the test piece.
[0062]
Then, the surface state of the curving portion of the flat hem, such as rough skin, minute cracks, and occurrence of large cracks, was visually observed. The evaluation was ○: good without rough skin or minute cracks; Δ: rough skin or minute cracks occurred; ×: large cracks occurred. Table 2 also shows these results.
[0063]
As is clear from Tables 1 and 2, the excess Si-type 6000-based aluminum alloy sheet of A to F within the composition range of the present invention has a maximum flow stress of 25 MPa even when high-temperature forming is performed at a temperature required for solution treatment. That is all. For this reason, it is excellent in handleability such as removal of the panel from the mold after high-temperature molding. Further, even if the panel is slowly cooled after the high-temperature molding, and after a short time artificial aging hardening treatment at a relatively low temperature, the yield strength of the panel after the artificial aging hardening treatment is as high as 170 MPa or more. In addition, in comparison with Invention Examples 1 and 2 which are examples of the aluminum alloy sheet subjected to the tempering treatment before the high-temperature forming, and Invention Examples 7 and 8 which are the aluminum alloy sheets without the tempering treatment before the high-temperature forming, the tempering treatment was performed. Inventive Examples 7 and 8 which are not provided are slightly inferior to Inventive Examples 1 and 2 in artificial age hardening properties. Therefore, whether or not the refining treatment is performed before the high-temperature molding is appropriately selected in consideration of the difference in the degree and the required characteristics of the panel.
[0064]
On the other hand, Comparative Example 9 using the alloy G 2 in which Cu is lower than 0.3% and lower than the lower limit is compared with Invention Example 2 using the alloy B 3 in which Cu is 0.4% and the lower limit. The maximum flow stress is less than 25 MPa, and the handleability of the panel after high-temperature molding is extremely poor. In addition, in the case of a panel that has been slowly cooled after high-temperature molding, the yield strength of the panel after the artificial aging hardening treatment is remarkably inferior to less than 170 MPa when subjected to the artificial aging hardening treatment at a relatively low temperature for a short time.
[0065]
Comparative Example 10 using alloy H 2 in which Si is below the lower limit of 0.5% and which is too low is also less gradual after high-temperature molding than Invention Example 3 using alloy C in which Si is the lower limit of 0.6%. In a cooled panel, when the artificial aging hardening treatment is performed at a relatively low temperature for a short time, the yield strength of the panel after the artificial aging hardening treatment is remarkably inferior to less than 170 MPa.
[0066]
Comparative Example 12 using Alloy J 2 in which Mg is below the lower limit of 0.2% is also lower in maximum flow stress than Invention Example 5 using Alloy E 3 in which Mg is 0.3% and lower limit. Since it is less than 25 MPa, the handleability of the panel after high-temperature molding is extremely poor. In addition, in the case of a panel that has been slowly cooled after high-temperature molding, the yield strength of the panel after the artificial aging hardening treatment is remarkably inferior to less than 170 MPa when subjected to the artificial aging hardening treatment at a relatively low temperature for a short time.
[0067]
Comparative Example 11 using alloy I 2 in which Si is too high and out of the upper limit of 1.4% and Comparative Example 13 using alloy K 2 in which Mg is too high and out of the upper limit of 1.0% have a maximum flow stress. 25 MPa or more. However, Comparative Example 11 and Comparative Example 13 show that the hem workability required when used as an automobile outer panel is Invention Example 4 using an alloy D 3 having an upper limit of 1.3% of Si, It is remarkably inferior to Inventive Example 6 using alloy F 2 having an upper limit of 1.0%. In Comparative Example 13, the panel after the artificial age hardening treatment had a 0.2% proof stress of less than 170 MPa.
[0068]
Further, even when Si was increased to the upper limit of 1.3% and Mg was increased to the upper limit of 1.0%, Comparative Example 14 using alloy L 2 containing no effective amount or substantial amount of Cu showed a maximum flow stress. Is less than 25 MPa, and the proof stress at high temperature is remarkably inferior to the invention examples. In addition, in the case of a panel that has been slowly cooled after high-temperature molding, when subjected to artificial aging hardening at a relatively low temperature for a short time, the 0.2% proof stress of the panel after artificial aging hardening is significantly inferior to less than 170 MPa. Therefore, it can be seen that Cu has a much better and unique effect compared to the low effect of increasing the amount of Si or Mg with respect to the problem of the present invention. In addition, from these results, the composition of the present invention for high-temperature strength, handleability of the panel after high-temperature molding, artificial aging hardening at a relatively low temperature for a short time when cooled slowly after high-temperature molding, or hemmability, We see the critical significance of the range.
[0069]
[Table 1]
[0070]
[Table 2]
[0071]
【The invention's effect】
According to the present invention, even when high-temperature molding is performed at a temperature required for solution treatment, the panel strength is high at the high-temperature molding temperature, and after this high-temperature molding, slow cooling is performed, and the cooling is performed at a relatively low temperature for a short time. Even after the artificial age hardening treatment, the method can provide a high-temperature forming 6000 series aluminum alloy plate and a method of manufacturing an aluminum alloy panel having high yield strength of the panel after the artificial age hardening treatment. Moreover, this aluminum alloy plate can be manufactured without changing the conventional plate manufacturing process. Therefore, the 6000 series aluminum alloy sheet has a great industrial value in that it can be used for panel forming.

Claims (3)

  1. Si:0.6〜1.3%、Mg:0.3〜0.9%、Mn:0.01 〜0.65% 、Cu:0.4〜1.0%を含み、かつSi/Mg が質量比で1.0 以上であり、残部Alおよび不可避的不純物からなるAl−Mg−Si系アルミニウム合金板であって、500 ℃の温度でかつ歪み速度:10 −1/sの条件で高温引張試験をした際の最大流動応力が25MPa 以上であるとともに、500 ℃で3 分間保持した後、500 〜200 ℃の範囲を平均冷却速度10℃/s以下で室温まで放冷する熱処理後、更に170 ℃で30分間保持する人工時効硬化処理を施した後の0.2%耐力が170MPa以上である特性を、このアルミニウム合金板が有することを特徴とする高温成形用Al−Mg−Si系アルミニウム合金板。Si: 0.6 to 1.3%, Mg: 0.3 to 0.9%, Mn: 0.01 to 0.65%, Cu: 0.4 to 1.0%, and Si / Mg Is an Al-Mg-Si-based aluminum alloy plate having a mass ratio of not less than 1.0, the balance being Al and unavoidable impurities, and a high temperature at a temperature of 500 ° C and a strain rate of 10 -1 / s. After a maximum flow stress of 25 MPa or more at the time of a tensile test and holding at 500 ° C. for 3 minutes, a heat treatment in which the temperature in the range of 500 to 200 ° C. is allowed to cool to room temperature at an average cooling rate of 10 ° C./s or less, Al-Mg-Si-based aluminum for high-temperature forming, characterized in that this aluminum alloy plate has a property that 0.2% proof stress after applying an artificial age hardening treatment at 170 ° C for 30 minutes is 170 MPa or more. Alloy plate.
  2. Si:0.6〜1.3%、Mg:0.3〜0.9%、Mn:0.01 〜0.65% 、Cu:0.4〜1.0%を含み、かつSi/Mg が質量比で1.0 以上であり、残部Alおよび不可避的不純物からなるAl−Mg−Si系アルミニウム合金板を、460 〜550 ℃の高温で成形してパネル化する際に、このパネルの前記高温成形時の最大流動応力を25MPa 以上として成形し、更にこの高温成形後のパネルに150 〜180 ℃で20〜40分間保持する人工時効硬化処理を施し、この人工時効硬化処理後のパネルの0.2%耐力を170MPa以上とすることを特徴とするアルミニウム合金パネルの製造方法。Si: 0.6 to 1.3%, Mg: 0.3 to 0.9%, Mn: 0.01 to 0.65%, Cu: 0.4 to 1.0%, and Si / Mg Is not less than 1.0 in terms of mass ratio, and when forming an Al-Mg-Si-based aluminum alloy plate composed of the balance of Al and unavoidable impurities at a high temperature of 460 to 550 ° C to make a panel, Molding is performed so that the maximum flow stress at the time of high-temperature molding is 25 MPa or more. Further, the panel after the high-temperature molding is subjected to an artificial aging hardening treatment at 150 to 180 ° C. for 20 to 40 minutes. A method for manufacturing an aluminum alloy panel, wherein the 2% proof stress is 170 MPa or more.
  3. 前記高温成形の温度が成形されるAl−Mg−Si系アルミニウム合金板が溶体化処理される温度である請求項2に記載のアルミニウム合金パネルの製造方法。The method for manufacturing an aluminum alloy panel according to claim 2, wherein the temperature of the high-temperature forming is a temperature at which the formed Al—Mg—Si-based aluminum alloy plate is subjected to a solution treatment.
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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102005039049A1 (en) * 2005-08-18 2007-02-22 Ks Aluminium-Technologie Ag Method for producing a casting and cylinder crankcase
JP2009024225A (en) * 2007-07-20 2009-02-05 Furukawa Sky Kk Aluminum alloy for storage container of high-pressure hydrogen gas
JP2009030106A (en) * 2007-07-26 2009-02-12 Furukawa Sky Kk Aluminum alloy panel and manufacturing method therefor
JP2012510565A (en) * 2008-09-19 2012-05-10 インペリアル イノベイションズ リミテッド Processing for forming aluminum alloy sheet parts

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102005039049A1 (en) * 2005-08-18 2007-02-22 Ks Aluminium-Technologie Ag Method for producing a casting and cylinder crankcase
JP2009024225A (en) * 2007-07-20 2009-02-05 Furukawa Sky Kk Aluminum alloy for storage container of high-pressure hydrogen gas
JP2009030106A (en) * 2007-07-26 2009-02-12 Furukawa Sky Kk Aluminum alloy panel and manufacturing method therefor
JP2012510565A (en) * 2008-09-19 2012-05-10 インペリアル イノベイションズ リミテッド Processing for forming aluminum alloy sheet parts
US10689738B2 (en) 2008-09-19 2020-06-23 Imperial Innovations Ltd. Process for forming aluminium alloy sheet components

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