JP3713614B2 - Method for producing aluminum alloy plate for can body - Google Patents
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Description
【０００１】
【発明の属する技術分野】
この発明はＤＩ加工（絞り−しごき加工）による２ピースアルミニウム缶用の缶胴、すなわちＤＩ缶胴に用いられるＡｌ−Ｍｇ−Ｍｎ系アルミニウム合金板の製造方法に関し、特に深絞り耳が低くかつ塗装焼付後の強度が高く、しかもＤＩ加工時の成形性および塗装焼付後の成形性に優れたＤＩ缶胴用アルミニウム合金板の製造方法に関するものである。
【０００２】
【従来の技術】
一般に２ピースアルミニウム缶の製造工程としては、缶胴素材に対して深絞り加工およびしごき加工によるＤＩ成形を施して缶胴形状とした後、所定のサイズにトリミングを施して脱脂・洗浄処理を行ない、さらに塗装および印刷を行なって焼付け（ベーキング）を行ない、その後、缶胴縁部に対してネッキング加工、フランジング加工を行ない、その後、別に成形した缶蓋（缶エンド）と合せてシーミング加工を行なって缶とするのが通常である。
【０００３】
このようにして製造されるＤＩ缶の素材（缶胴材）としては、従来からＡｌ−Ｍｇ−Ｍｎ系合金であるＪＩＳ ３００４合金の硬質板が広く用いられている。この３００４合金は、しごき加工性に優れていて、強度を高めるために高圧延率で冷間圧延を施した場合でも比較的良好な成形性を示すところから、ＤＩ缶胴材として好適であるとされている。
【０００４】
このようなＤＩ缶胴用の３００４合金硬質板の製造方法としては、ＤＣ鋳造法などによって鋳造後、鋳塊に対し均質化処理を施し、さらに熱間圧延および冷間圧延を施して所定の板厚とし、かつその過程における冷間圧延前あるいは冷間圧延中途において中間焼鈍を施す方法が一般的である。
【０００５】
ところでＤＩ缶胴については、主として材料コスト低減、軽量化の目的から、より薄肉化を図ることが強く望まれている。そしてこのように薄肉化を図るためには、薄肉化に伴なって生じる缶の座屈強度低下の問題を回避するため、材料の高強度化を図ることが不可欠である。
【０００６】
またＤＩ缶胴用材料については、上述のような薄肉化を図るための高強度化の要請ばかりではなく、ＤＩ成形時における耳率が低いことが強く望まれる。すなわち、ＤＩ成形時の耳率が低いことは、ＤＩ成形時の歩留りの向上と、缶胴の耳切れに起因する缶胴破断の防止の点から必要とされている。さらに、耳率を如何に制御するかによって、強度、フランジ成形性、耳率のバランスに影響を及ぼすことになるから、耳率制御は缶胴材にとって極めて重要な課題となっている。
【０００７】
しかしながら、前述のような従来の一般的な缶胴材製造方法では、耳率を抑えるにも限界があり、例えば絞り比１．９において耳率を３％以下に抑えることは困難であった。
【０００８】
そこで低耳率を達成するための缶胴材製造方法が、既に例えば特開平５−３１７９１４号、特開平９−２４９９３２号において提案されている。
【０００９】
【発明が解決しようとする課題】
前述の特開平５−３１７９１４号においては、冷間圧延中途において２回焼鈍を行なう方法が提案されているが、このように冷間圧延中途において２回焼鈍を行なった場合、最終冷間圧延の圧延率を大きくとれないため、強度不足が生じやすいという問題があるほか、製缶時の材料の加工硬化量が大きく、フランジ成形性が悪化する問題がある。
【００１０】
また特開平９−２４９９３２号においては、熱間圧延の最終パスにおける圧延速度、減面率、および熱延終了温度を厳密に規制することによって低耳率を達成する方法が提案されており、この方法は、ある程度は低耳率達成に有効であるが、依然として耳率の変動は大きく、確実かつ安定して低耳率を得るには不充分であった。
【００１１】
以上のように、従来提案されている方法は、缶胴材に対する諸要求を全て充分に満たすことは困難であった。
【００１２】
この発明は以上の事情を背景としてなされたものであって、缶胴材として望まれる諸要求を充分に満足し得る材料、すなわち薄肉化を図った場合でも強度とフランジ成形性に優れ、しかも深絞りにおける材料の耳率が確実かつ安定して低い缶胴用アルミニウム合金板を製造し得る方法を提供することを基本的な目的とするものである。
【００１３】
【課題を解決するための手段】
前述のような課題を解決するべく、本願発明者等が種々実験・検討を重ねた結果、熱間圧延上りでの熱延板の再結晶状態を適切に制御し、かつその熱延板に対し軽度の１次冷間圧延を施してから中間焼鈍を行なうことによって、前述の課題を解決し得ることを見出し、この発明をなすに至ったのである。
【００１４】
具体的には、請求項１の発明の缶胴用アルミニウム合金板の製造方法は、Ｍｇ０．５〜２．０％、Ｍｎ０．５〜２．０％、Ｆｅ０．１〜０．７％、Ｓｉ０．０５〜０．５％を含有し、残部がＡｌおよび不可避的不純物よりなるアルミニウム合金をスラブに鋳造した後、そのスラブに対し５２０〜６３０℃の範囲内の温度で１時間以上の均質化処理を施し、さらにスラブを熱間圧延するにあたり、３８０〜５８０℃の範囲内の温度で熱間圧延を開始し、仕上板厚１．０〜７．０ｍｍの範囲内まで熱間圧延して、２００〜３３０℃の範囲内の温度で熱間圧延を終了させ、さらに熱間圧延終了直後の２００〜３３０℃の範囲内の温度から室温までの平均冷却速度を１〜１００℃／時間の範囲内として、再結晶率が体積率で９０％以下、耐力が７０ＭＰａ以上の熱延板を得、その後２〜２５％の範囲内の圧延率で１次冷間圧延を行ない、さらに１〜１００℃／秒の範囲内の平均昇温速度で３３０〜６２０℃の範囲内の温度に加熱して保持なしもしくは１０分以下の保持を行なって、１〜１００℃／秒の範囲内の平均冷却速度で冷却する連続焼鈍を施し、その後さらに６０％以上の圧延率で最終冷間圧延を行なうことを特徴とするものである。
【００１５】
また請求項２の発明の缶胴用アルミニウム合金板の製造方法は、素材アルミニウム合金として、Ｍｇ０．５〜２．０％、Ｍｎ０．５〜２．０％、Ｆｅ０．１〜０．７％、Ｓｉ０．０５〜０．５％を含有し、かつＣｕ０．０５〜０．５％、Ｃｒ０．０５〜０．３％、Ｚｎ０．０５〜０．５％のうちの１種または２種以上を含有し、残部がＡｌおよび不可避的不純物よりなるアルミニウム合金を用い、請求項１で規定するプロセス条件と同様の条件の均質化処理−熱間圧延−１次冷間圧延−連続焼鈍−最終冷間圧延のプロセスで製造するものである。
【００１６】
さらに請求項３の発明の缶胴用アルミニウム合金板の製造方法は、素材合金として請求項１で規定する合金と同じアルミニウム合金を用い、かつ均質化処理−熱間圧延−１次冷間圧延を請求項１で規定する条件で行ない、その後の焼鈍として、０．１℃／秒以下の平均昇温速度で加熱して２５０〜５００℃の範囲内の温度に０．５時間以上保持して、０．１℃／秒以下の平均冷却速度で冷却するバッチ焼鈍を施し、その後請求項１の方法と同様に６０％以上の圧延率で最終冷間圧延を行なうものである。
【００１７】
そしてまた請求項４の発明の缶胴用アルミニウム合金板の製造方法は、素材アルミニウム合金として請求項２で規定する成分組成と同じ成分組成の合金を用い、請求項３で規定するプロセスで製造するものである。
【００１８】
一方請求項５の発明の缶胴用アルミニウム合金板の製造方法は、素材アルミニウム合金として、Ｍｇ０．５〜２．０％、Ｍｎ０．５〜２．０％、Ｆｅ０．１〜０．７％、Ｓｉ０．０５〜０．５％を含有し、さらに０．００５〜０．２０％のＴｉを単独でもしくは０．０００１〜０．０５％のＢと組合せて含有し、残部がＡｌおよび不可避的不純物よりなるアルミニウム合金を用い、請求項１で規定するプロセス条件と同様の条件の均質化処理−熱間圧延−１次冷間圧延−連続焼鈍−最終冷間圧延のプロセスで製造するものである。
【００１９】
また請求項６の発明の缶胴用アルミニウム合金板の製造方法は、素材アルミニウム合金として、Ｍｇ０．５〜２．０％、Ｍｎ０．５〜２．０％、Ｆｅ０．１〜０．７％、Ｓｉ０．０５〜０．５％を含有し、かつＣｕ０．０５〜０．５％、Ｃｒ０．０５〜０．３％、Ｚｎ０．０５〜０．５％のうちの１種または２種以上を含有し、さらに０．００５〜０．２０％のＴｉを単独でもしくは０．０００１〜０．０５％のＢと組合せて含有し、残部がＡｌおよび不可避的不純物よりなるアルミニウム合金を用い、請求項１で規定するプロセス条件と同様の条件の均質化処理−熱間圧延−１次冷間圧延−連続焼鈍−最終冷間圧延のプロセスで製造するものである。
【００２０】
さらに請求項７の発明の缶胴用アルミニウム合金板の製造方法は、素材合金として請求項５で規定する合金と同じアルミニウム合金を用い、請求項３で規定するプロセス条件と同様の条件の均質化処理−熱間圧延−１次冷間圧延−バッチ焼鈍−最終冷間圧延のプロセスで製造するものである。
【００２１】
そしてまた請求項８の発明の缶胴用アルミニウム合金板の製造方法は、素材アルミニウム合金として請求項６で規定する成分組成と同じ成分組成の合金を用い、請求項３で規定するプロセスで製造するものである。
【００２２】
なお、以上の請求項１〜８の方法において、６０％以上の圧延率で最終冷間圧延を行なった後には、さらに８０〜２００℃の範囲内の温度で０．５時間以上保持する最終焼鈍を施しても良く、これを規定したのが請求項９の発明である。
【００２３】
【発明の実施の形態】
先ずこの発明の方法において用いられるアルミニウム合金の成分組成の限定理由について説明する。
【００２４】
Ｍｇ：
Ｍｇの添加は、Ｍｇそれ自体の固溶による強度向上に効果があり、またＭｇの固溶に伴なって加工硬化量の増大による強度向上が期待でき、さらにはＳｉとの共存によるＭｇ2Ｓｉの時効析出による強度向上も期待でき、したがってＭｇは缶胴材として必要な強度を得るためには不可欠の元素である。またＭｇは、加工時の転位の増殖作用があるため、再結晶粒を微細化させるためにも有効である。但しＭｇ量が０．５％未満では上述の効果が少なく、一方２．０％を越えれば、高強度は容易に得られるものの、ＤＩ加工時の変形抵抗が大きくなって絞り性やしごき性を悪くする。したがってＭｇ量は０．５〜２．０％の範囲内とした。
【００２５】
Ｍｎ：
Ｍｎは強度および成形性の向上に寄与する有効な元素である。特にこの発明で目的としている用途である缶胴材ではＤＩ成形時にしごき加工が加えられるため、とりわけＭｎは重要となる。アルミニウム板のしごき加工においては通常エマルジョンタイプの潤滑剤が用いられているが、Ｍｎ系晶出物が少ない場合には同程度の強度を有していてもエマルジョンタイプ潤滑剤だけでは潤滑能が不足し、ゴーリングと呼ばれる擦り疵や焼付きなどの外観不良が発生するおそれがある。この現象は晶出物の大きさ、量、種類に影響されることが知られており、その晶出物を形成するためにＭｎは不可欠な元素である。Ｍｎ量が０．５％未満ではＭｎ系化合物による固体潤滑的な効果が得られず、一方Ｍｎ量が２．０％を越えればＡｌ6Ｍｎの初晶巨大金属間化合物が発生し、著しく成形性を損なう。そこでＭｎ量は０．５〜２．０％の範囲内とした。
【００２６】
Ｆｅ：
Ｆｅは、Ｍｎの晶出や析出を促進して、アルミニウム基地中のＭｎ固溶量やＭｎ系金属間化合物の分散状態を制御するために必要な元素である。適正な化合物分散状態を得るためには、Ｍｎ添加量に応じてＦｅを添加することが必要である。Ｆｅ量が０．１％未満では適正な化合物分散状態を得ることが困難であり、一方Ｆｅ量が０．７％を越えれば、Ｍｎ添加に伴なって初晶巨大金属間化合物が発生しやすくなり、成形性を著しく損なう。そこでＦｅ量の範囲は０．１〜０．７％とした。
【００２７】
Ｓｉ：
Ｓｉの添加は、Ｍｇ2 Ｓｉ系化合物の析出による時効硬化を通じて缶胴材の強度向上に寄与する。またＳｉは、Ａｌ−Ｍｎ−Ｆｅ−Ｓｉ系金属間化合物を生成して、Ｍｎ系金属間化合物の分散状態を制御するために必要な元素である。Ｓｉ量が０．０５％未満では上記の効果が得られず、一方０．５％を越えれば時効硬化により材料が硬くなりすぎて成形性を阻害する。そこでＳｉ量の範囲は０．０５〜０．５％とした。
【００２８】
Ｔｉ，Ｂ：
通常のアルミニウム合金においては、鋳塊結晶粒微細化のためにＴｉ、あるいはＴｉおよびＢを微量添加することが行なわれており、この発明においても、必要に応じて微量のＴｉを単独で、あるいはＢと組合せて添加しても良い。但しＴｉ量が０．００５％未満ではその効果が得られず、０．２０％を越えれば巨大なＡｌ−Ｔｉ系金属間化合物が晶出して成形性を阻害するため、Ｔｉを添加する場合のＴｉ量は０．００５〜０．２０％の範囲内とした。またＴｉとともにＢを添加すれば鋳塊結晶粒微細化の効果が向上するが、Ｔｉと併せてＢを添加する場合、Ｂ量が０．０００１％未満ではその効果がなく、０．０５％を越えればＴｉ−Ｂ系の粗大粒子が混入して成形性を害することから、ＴｉとともにＢを添加する場合のＢ量は０．０００１〜０．０５％の範囲内とした。
【００２９】
Ｃｕ，Ｃｒ，Ｚｎ：
これらはいずれも強度向上に寄与する元素であり、必要に応じてこれらのうちから選ばれた１種または２種以上が添加される。これらの各元素についてさらに説明する。
【００３０】
Ｃｕ：
Ｃｕは、焼鈍時にアルミニウム基地中に溶体化させておき、塗装焼付処理時にＡｌ−Ｃｕ−Ｍｇ系析出物として析出することによる析出硬化を利用した強度向上に寄与する。Ｃｕ量が０．０５％未満ではその効果が得られず、一方Ｃｕを０．５％を越えて添加した場合には、時効硬化は容易に得られるものの、硬くなりすぎて成形性を阻害し、また耐食性も劣化する。そこでＣｕ量の範囲は０．０５〜０．５％とした。
【００３１】
Ｃｒ；
Ｃｒも強度向上に効果的な元素であるが、０．０５％未満ではその効果が少なく、０．３％を越えれば巨大晶出物生成によって成形性の低下を招くため、好ましくない。そこでＣｒ量の範囲は０．０５〜０．３％とした。
【００３２】
Ｚｎ：
Ｚｎの添加はＡｌ−Ｍｇ−Ｚｎ系粒子の時効析出による強度向上に寄与するが、０．０５％未満ではその効果が得られず、０．５％を越えれば、強度への寄与については問題がないが、耐食性を劣化させる。そこでＺｎ量の範囲は０．０５〜０．５％とした。
【００３３】
以上の各元素の残部はＡｌと不可避不純物すれば良い。
【００３４】
次にこの発明における製造プロセスを、その作用とともに説明する。
【００３５】
先ず前述のような合金組成を有するアルミニウム合金鋳塊を常法に従ってＤＣ鋳造法（半連続鋳造法）などにより鋳造する。次いでその鋳塊に対して均質化処理を施して、鋳塊の偏析を均質化するとともにＭｎ系の第２相粒子サイズと分布を最適化する。均質化処理温度が５２０℃未満では均質化の効果が不充分であり、一方６３０℃を越えれば共晶融解のおそれがある。均質化処理は１時間未満では均質化が不充分となる。したがって均質化処理は５２０〜６３０℃の範囲内の温度で１時間以上行なう必要がある。なお均質化処理時間の上限は特に規制しないが、経済性を考慮して通常は４８時間以下にすることが好ましい。
【００３６】
均質化処理を施したスラブに対しては、熱間圧延を行なう。この熱間圧延は、通常は粗圧延とそれに続く仕上圧延とに区分されるが、この発明の方法の場合、熱間圧延の開始温度条件、すなわち粗圧延の開始温度条件と、熱間圧延の終了温度条件、すなわち仕上圧延の上り温度条件および上り板厚条件と、仕上圧延後の室温までの冷却速度条件を適切に規制し、さらに仕上圧延後の室温に至った状態での熱延板の再結晶状態を適切に制御することが極めて重要である。そこでこれらの条件についてさらに詳細に説明する。
【００３７】
（１） 熱間圧延開始温度（粗圧延開始温度）を３８０〜５８０℃の範囲内とする。
熱間圧延の開始温度は、熱間圧延中の材料の回復および再結晶の挙動に強い影響を及ぼし、特に最終板の深絞り耳を低くするために必要なキューブ方位の結晶組織（キューブ方位の結晶粒の集合体を以下キューブバンドと称する）の形成に重要な役割を果たしている。熱間圧延開始温度が３８０℃未満ではキューブバンドの形成量が不足しやすく、一方５８０℃を越えた高温で熱間圧延を開始すれば、キューブバンドの形成は容易となるものの、板の表面品質が低下する。したがって熱間圧延開始温度は３８０〜５８０℃の範囲内とする必要がある。
【００３８】
（２） 熱間圧延の終了温度（仕上圧延上り温度）を２００〜３３０℃の範囲内とする。
熱間仕上圧延の上り温度が２００℃未満では表面品質が低下し、また第２相粒子周辺での再結晶核生成が増加して、その後の再結晶でキューブ方位以外の再結晶粒が多くなり、低耳率制御に不利となる。一方上り温度が３３０℃を越えれば、熱間圧延終了後室温まで冷却した状態での再結晶率を９０％以下、耐力を７０ＭＰａ以上とすることが困難となってしまう。
【００３９】
（３） 熱間仕上圧延の上り板厚を１．０〜７．０ｍｍの範囲内とする。
仕上圧延の上がり板厚が１．０ｍｍ未満では、焼鈍後の最終的な冷間圧延での圧延率を充分に確保することが困難となり、最終板の強度不足が生じやすい。一方上り板厚が７．０ｍｍを越えれば、焼鈍後の最終的な冷間圧延において圧延率が高くなり過ぎ、高強度は得られず、耳率も高くなってしまう。
【００４０】
（４） 熱間圧延終了直後の２００〜３３０℃の範囲内の温度から室温までの平均冷却速度を１〜１００℃／時間の範囲内、望ましくは１〜７０℃／時間の範囲内とする。
熱間圧延終了直後の上り材（コイル）の２００〜３３０℃の範囲内の温度から室温までの冷却過程、特に１００℃までの冷却過程は、キューブ方位再結晶粒の核生成が生じる過程であり、この間の冷却速度が１００℃／時間を越える場合には、キューブ方位再結晶粒の核生成が不充分となり、最終板の低耳率制御に不利となる。一方、その間の冷却速度が１℃／時間未満の場合は、ほぼ完全に再結晶してしまい、室温まで冷却した状態での再結晶率を９０％以下、耐力値を７０ＭＰａ以上とすることが困難となる。
【００４１】
（５） 室温まで冷却した状態での熱間圧延上がり板（熱延板）の再結晶率を９０％以下、耐力値を７０ＭＰａ以上とする。このことは、熱延板を完全再結晶状態とはさせずに、部分再結晶状態とすることを意味する。
熱間圧延上り板の室温まで冷却した状態での再結晶率と耐力値の規制は、この発明の方法において重要であり、これらの値は最終板の低耳率制御と外観欠陥に大きな影響を及ぼす。すなわち、熱間圧延上りの２００〜３３０℃の範囲内の温度から室温まで冷却する間に自己焼鈍が進んで、再結晶率が９０％を越えてしまった場合（すなわち完全再結晶状態もしくはそれに近い再結晶状態）あるいは耐力値が７０ＭＰａを下廻ってしまった場合（すなわち完全焼鈍状態もしくはそれに近い焼鈍状態）には、その後の１次冷間圧延と焼鈍によるキューブ方位の再結晶組織を拡大させる効果が得られなくなり、そのため最終板を低耳率に制御することが困難となり、また同時に最終板の結晶粒の粗大化を招いて製缶時の肌荒れやフローライン等の外観欠陥が発生しやすくなる。したがって室温まで冷却した状態での再結晶率を９０％以下、耐力値を７０ＭＰａ以上に規制する必要がある。そしてこの範囲内でも特に再結晶率は７５％以下、耐力値は９０ＭＰａ以上が好ましい。なおこのように室温まで冷却した状態での再結晶率には、主として熱間圧延終了温度と、熱間圧延終了温度からの室温までの冷却速度、さらには合金の成分組成が影響を与えるから、これらを相互の関係のもとに適切に調整することによって室温での再結晶率を９０％以下に制御することができ、また室温まで冷却した状態での耐力値には、上述ような再結晶率と合金成分組成が影響を与えるから、前記同様に熱間圧延終了温度、室温までの冷却速度、合金の成分組成を相互の関係のもとに適切に調整することによって７０ＭＰａ以上に制御することができる。
【００４２】
以上の（１）〜（５）の条件を満たすようにして得られた部分再結晶状態の熱延板に対しては、圧延率が２〜２５％の範囲内の軽度の１次冷間圧延を施す。このように部分再結晶状態の熱延板に対し軽度の１次冷間圧延を施して熱延板に軽度の歪みを与えることにより、その後の焼鈍でキューブ方位の再結晶粒の生成、成長を促進させるとともにキューブ方位以外の再結晶粒の生成、成長を抑制する効果が得られる。
【００４３】
ここで、熱延板に対する１次冷間圧延の圧延率が２％未満では、歪み量不足によりキューブ方位の再結晶粒の生成、成長を加速する効果およびキューブ方位以外の再結晶粒の生成、成長を抑制する効果が不充分となり、一方圧延率が２５％を越えれば、導入された多量の歪によりキューブ方位の再結晶粒も壊されてしまうため、キユーブ方位再結晶粒組織を充分に得ることが困難となり、最終板の耳率低減効果が得られなくなる。したがって熱延板に対する１次冷間圧延における圧延率は２〜２５％の範囲内とした。
【００４４】
このように熱延板に対して圧延率２〜２５％の１次冷間圧延を施した後には、連続焼鈍（ＣＡＬ）もしくはバッチ焼鈍によって中間焼鈍を施す。この中間焼鈍は、材料を完全に再結晶させ、最終冷間圧延後の最終板の耳率を低くするために必要な工程である。
【００４５】
１次冷間圧延後の中間焼鈍に連続焼鈍を適用する場合、その連続焼鈍は、１〜１００℃／秒の範囲内の平均昇温速度で３３０〜６２０℃の範囲内の温度に加熱し、保持なしもしくは１０分以下の保持の後、１〜１００℃／秒の範囲内の平均冷却速度で冷却する条件とする。ここで、平均昇温速度、平均冷却速度が１℃／秒未満では、連続焼鈍（ＣＡＬ）方式においては生産性の著しい低下を招き、また１００℃／秒を越える平均昇温速度、平均冷却速度はキューブ方位の再結晶粒の形成に不利となる。また加熱到達温度が３３０℃未満では再結晶が生じにくく、一方６２０℃を越える高温では共晶融解が生じるおそれがある。さらに３３０〜６２０℃に１０分を越えて保持することは、連続焼鈍の生産性を阻害する。
【００４６】
一方、一次冷間圧延後の中間焼鈍としてバッチ焼鈍を適用する場合、平均昇温速度０．１℃／秒以下で２５０〜５００℃の範囲内の温度に加熱し、その範囲内の温度で０．５時間以上保持し、平均冷却速度０．１℃／秒以下で冷却する。ここで、平均昇温速度および平均冷却速度が０．１℃／秒を越えれば、バッチ焼鈍方式では熱延板コイル全体を均一に加熱もしくは冷却できなくなる問題が生じる。また加熱保持温度が２５０℃未満では完全に再結晶させることが困難となり、一方５００℃を越える高温では再結晶核が粗大となって、製缶時に肌荒れやフローラインなどの表面欠陥が発生しやすくなる。また加熱保持の時間が０．５時間未満では完全に再結晶させることが困難であり、また熱延板のコイルの全体を均一に加熱することが困難となる。なおバッチ焼鈍の場合の加熱保持時間の上限は特に定めないが、通常は経済性の観点から、２４時間以内とする。
【００４７】
以上のように、連続焼鈍もしくはバッチ焼鈍による中間焼鈍を施した後には、最終板厚としかつ必要な強度を得るために冷間圧延を施す。ここで、最終の冷間圧延率が６０％未満では、加工硬化による強度上昇が少なく、缶胴材用の最終板に必要な強度を得ることが困難である。
【００４８】
冷間圧延後の板は、これを最終板としてそのままＤＩ成形に供しても良いが、冷間圧延板に必要に応じて８０〜２００℃の範囲内の温度で０．５時間以上の最終焼鈍を行なっても良い。この最終焼鈍は、延性の回復による成形性の向上を目的としたものであるが、その温度が８０℃未満では成形性の向上効果が充分に得られず、一方２００℃を越えれば軟化による強度低下が大きくなり、また焼鈍時間が０．５時間未満では成形性向上効果を充分に得ることができない。なお焼鈍時間の上限は特に定めないが、生産性、経済性の点からは１０時間以下が望ましい。
【００４９】
【実施例】
表１に示す金属記号Ａ〜Ｆの各合金について、常法に従ってＤＣ鋳造法によりスラブに鋳塊した。その後、均質化処理を施した後、熱間粗圧延および熱間仕上圧延によって熱間圧延を施した。熱間圧延の詳細な条件を表２の製造番号１〜７に示す。さらに室温まで冷却した後の熱延板に対し、表３中に示す条件で１次冷間圧延を施した後、中間焼鈍として連続焼鈍もしくはバッチ焼鈍を施し、その後最終冷間圧延を行なった。なお最終冷間圧延後、製造番号３，５の場合を除いて最終焼鈍を施した。
【００５０】
以上のようにして得られた缶胴用のアルミニウム合金板について、元板の機械的性質（引張強さＴＳ、耐力ＹＳ、伸びＥＬ）および塗装焼付（ベーキング）を想定した２００℃×２０分の熱処理を行なった後の機械的性質を調べた。また元板については、ポンチ径４８ｍｍ、ブランク径９３ｍｍ、クリアランス３０％の条件にてカップ深絞り試験を行なって耳率を調べた。ここで、強度については、塗装焼付（ベーキング）後の耐力として、２７０ＭＰａ以上の値が必要であり、また耳率については、３％を越えれば製缶中のトラブルが発生しやすくなることが知られている。
【００５１】
さらにＤＩ缶成形性評価として、缶切れ性、口拡げ性（フランジ成形性）、シーミング性、および外観欠陥について調べた。ここで、缶切れ性については苛酷なしごき加工を連続１０，０００缶行なったときの缶破断の発生状況を調べ、また口拡げ性については４段ネッキング加工後のフランジ成形性を調べ、さらにシーミング性については４段ネッキング加工後のシーミング加工性を調べ、そしてまた外観欠陥については、ＤＩ缶の缶胴壁の圧延方向に沿ったフローライン状の外観欠陥およびＤＩ方向の縦筋の発生状況を調べ、それぞれ◎〜×で相対評価した。これらの結果を表４に示す。
【００５２】
【表１】
【表２】
【表３】
【表４】
表１〜表４において、製造番号１〜５はいずれもこの発明で規定する成分組成範囲内の合金について、この発明で規定する製造プロセス条件を満足して製造したものであり、この場合は表５に示すように、いずれも耳率が３％を確実に下廻って充分な低耳率を達成でき、かつベーキング後の耐力が２７０ＭＰａ以上で充分な強度を有しており、しかもＤＩ成形性も優れていることが明らかである。
【００５７】
一方製造番号６は、合金の成分組成はこの発明で規定する範囲内であるが、製造プロセス条件がこの発明で規定する範囲から外れたものである。すなわち製造番号６のプロセスでは、熱間圧延上り温度が３４０℃であって、この発明で規定する２００〜３３０℃の範囲を越え、また熱間圧延終了後の室温まで冷却した状態での再結晶率が１００％であって、この発明の再結晶率上限９０％を越えるとともに、耐力値が６６ＭＰａとこの発明で規定する下限７０ＭＰａを下廻り、さらに１次冷間圧延率が３０％とこの発明で規定する２〜２５％の範囲を越えており、この場合は最終板の耳率が５．８％と高く、缶切れ性と口拡げ性が劣っていた。
【００５８】
また製造番号７は、Ｍｇ量が０．４７％とこの発明で規定する合金のＭｇ量下限よりも低い合金Ｆを用いた例であり、この場合はベーキング後の強度が低く、また耳率も高く、缶切れ性に劣っていた。
【００５９】
【発明の効果】
前述の実施例からも明らかなように、この発明の方法によれば、ＤＩ缶胴用材料として、缶胴の薄肉化に充分耐え得るような高強度を有すると同時に、ＤＩ成形性、特にフランジ成形性に優れ、しかも深絞り耳率が安定して低いアルミニウム合金板を確実に得ることができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a can body for a two-piece aluminum can by DI processing (drawing-ironing processing), that is, a method for producing an Al-Mg-Mn-based aluminum alloy plate used for a DI can body, and particularly has a low deep drawing ear and is coated The present invention relates to a method for producing an aluminum alloy plate for a DI can body having high strength after baking and excellent moldability during DI processing and formability after baking.
[0002]
[Prior art]
In general, as a manufacturing process for 2-piece aluminum cans, the can body material is subjected to DI molding by deep drawing and ironing to form a can body shape, then trimmed to a predetermined size, and then degreased and washed. Furthermore, painting and printing are performed and baking (baking) is performed, then necking and flanging are performed on the can body edge, and then seaming processing is performed together with a separately formed can lid (can end). It is normal to go into cans.
[0003]
Conventionally, a hard plate of JIS 3004 alloy, which is an Al-Mg-Mn alloy, has been widely used as a raw material (can body material) for a DI can thus manufactured. This 3004 alloy is excellent in ironing workability and exhibits relatively good formability even when cold-rolled at a high rolling rate in order to increase strength, and is therefore suitable as a DI can body. Has been.
[0004]
As a method of manufacturing such a 3004 alloy hard plate for a DI can body, after casting by a DC casting method or the like, the ingot is subjected to homogenization treatment, and further subjected to hot rolling and cold rolling to a predetermined plate. A method is generally used in which the thickness is increased and intermediate annealing is performed before or during the cold rolling in the process.
[0005]
By the way, it is strongly desired to reduce the thickness of the DI can body mainly for the purpose of reducing the material cost and reducing the weight. In order to reduce the wall thickness in this way, it is indispensable to increase the strength of the material in order to avoid the problem of reduced buckling strength of the can caused by the reduction in thickness.
[0006]
In addition, the DI can body material is strongly desired not only to have a high strength for thinning as described above, but also to have a low ear rate during DI molding. That is, a low ear rate at the time of DI molding is required from the standpoint of improving the yield at the time of DI molding and preventing can barrel breakage caused by ear can cut of the can barrel. Further, since the balance of strength, flange formability, and ear ratio is affected by how the ear ratio is controlled, the ear ratio control is an extremely important issue for the can body material.
[0007]
However, in the conventional general can body manufacturing method as described above, there is a limit in suppressing the ear rate, and for example, it was difficult to suppress the ear rate to 3% or less at a drawing ratio of 1.9.
[0008]
In view of this, a can body manufacturing method for achieving a low ear rate has already been proposed in, for example, Japanese Patent Laid-Open Nos. 5-317914 and 9-249932.
[0009]
[Problems to be solved by the invention]
In the above-mentioned JP-A-5-317914, a method of performing annealing twice in the middle of cold rolling is proposed, but when annealing is performed twice in the middle of cold rolling in this way, the final cold rolling is performed. Since the rolling rate cannot be increased, there is a problem that the strength is likely to be insufficient, and there is a problem that the work hardening amount of the material at the time of can making is large and the flange formability is deteriorated.
[0010]
Japanese Patent Laid-Open No. 9-249932 proposes a method for achieving a low ear rate by strictly regulating the rolling speed, the area reduction rate, and the hot rolling end temperature in the final pass of hot rolling. method is to some extent effective in achieving low ears rate was insufficient to obtain a still and by increasing variation of the ear rate, reliably and stably low ear rate.
[0011]
As described above, it has been difficult for the conventionally proposed methods to sufficiently satisfy all the requirements for the can body material.
[0012]
The present invention has been made against the background of the above circumstances, and is a material that can sufficiently satisfy various requirements desired as a can body material, that is, excellent in strength and flange formability even when thinned, and deep. The basic object of the present invention is to provide a method capable of producing an aluminum alloy plate for a can body with a reliable and stable low ear ratio of the material in the drawing.
[0013]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the inventors of the present application have conducted various experiments and examinations. As a result, the recrystallization state of the hot rolled sheet after hot rolling is appropriately controlled, and the hot rolled sheet The inventors have found that the above-described problems can be solved by performing intermediate annealing after performing a mild primary cold rolling, and have made the present invention.
[0014]
Specifically, the manufacturing method of the aluminum alloy plate for can bodies of the invention of claim 1 is Mg 0.5-2.0%, Mn 0.5-2.0%, Fe 0.1-0.7%, SiO containing .05～0.5%, after the aluminum alloy remaining portion is made of Al and unavoidable impurities was cast into a slab, 1 hour or more homogenization at a temperature in the range of five hundred twenty to six hundred and thirty ° C. for that slab When the treatment is performed and the slab is further hot-rolled, the hot-rolling is started at a temperature in the range of 380 to 580 ° C., the hot-rolling is performed in the range of the finished sheet thickness of 1.0 to 7.0 mm, The hot rolling is finished at a temperature in the range of 200 to 330 ° C., and the average cooling rate from the temperature in the range of 200 to 330 ° C. immediately after the end of the hot rolling to room temperature is in the range of 1 to 100 ° C./hour. The recrystallization rate is 90% or less by volume, and the proof stress is 70M. a or more hot-rolled sheet is obtained, and then primary cold rolling is performed at a rolling rate within a range of 2 to 25%, and further an average heating rate within a range of 1 to 100 ° C./second is set to 330 to 620 ° C. Heat to a temperature within the range and hold without holding or hold for 10 minutes or less, and perform continuous annealing to cool at an average cooling rate within the range of 1 to 100 ° C./second, and then at a rolling rate of 60% or more The final cold rolling is performed.
[0015]
Moreover, the manufacturing method of the aluminum alloy plate for can bodies of invention of Claim 2 is Mg0.5-2.0%, Mn0.5-2.0%, Fe0.1-0.7% as raw material aluminum alloy, Si 0.05 to 0.5% and Cu 0.05 to 0.5%, Cr 0.05 to 0.3%, Zn 0.05 to 0.5%, or one or more of them and, using the aluminum alloy remaining portion is made of Al and unavoidable impurities, homogenizing the same conditions and process conditions specified in claim 1 - hot rolled -1-order cold rolling - continuous annealing - the final cold It is manufactured by a rolling process.
[0016]
Furthermore, the manufacturing method of the aluminum alloy plate for can bodies of invention of Claim 3 uses the same aluminum alloy as the alloy prescribed | regulated in Claim 1 as a raw material alloy, and performs homogenization treatment-hot rolling-primary cold rolling. Performed under the conditions defined in claim 1, and as the subsequent annealing, heated at an average temperature increase rate of 0.1 ° C./second or less and held at a temperature in the range of 250 to 500 ° C. for 0.5 hour or more, Batch annealing is performed to cool at an average cooling rate of 0.1 ° C./second or less, and then final cold rolling is performed at a rolling rate of 60% or more in the same manner as in the method of claim 1.
[0017]
And the manufacturing method of the aluminum alloy plate for can bodies of invention of Claim 4 uses the alloy of the same component composition as the component composition prescribed | regulated in Claim 2 as a raw material aluminum alloy, and it manufactures it by the process prescribed | regulated in Claim 3. Is.
[0018]
On the other hand, the manufacturing method of the aluminum alloy plate for can bodies of the invention of claim 5 is as follows: Mg 0.5-2.0%, Mn 0.5-2.0%, Fe 0.1-0.7%, Containing 0.05 to 0.5% Si, further containing 0.005 to 0.20% Ti alone or in combination with 0.0001 to 0.05% B, the balance being Al and inevitable impurities It is manufactured by the process of homogenization treatment-hot rolling-primary cold rolling-continuous annealing-final cold rolling under the same conditions as the process conditions specified in claim 1.
[0019]
Moreover, the manufacturing method of the aluminum alloy plate for can bodies of invention of Claim 6 is Mg0.5-2.0%, Mn0.5-2.0%, Fe0.1-0.7% as raw material aluminum alloy, Si 0.05 to 0.5% and Cu 0.05 to 0.5%, Cr 0.05 to 0.3%, Zn 0.05 to 0.5%, or one or more of them Further, an aluminum alloy containing 0.005 to 0.20% Ti alone or in combination with 0.0001 to 0.05% B with the balance being Al and inevitable impurities is used. It is manufactured by a process of homogenization treatment-hot rolling-primary cold rolling-continuous annealing-final cold rolling under the same conditions as the process conditions specified in.
[0020]
Furthermore, the manufacturing method of the aluminum alloy plate for can bodies of the invention of claim 7 uses the same aluminum alloy as the alloy specified in claim 5 as the material alloy, and homogenized under the same conditions as the process conditions specified in claim 3. It is manufactured by a process of treatment-hot rolling-primary cold rolling-batch annealing-final cold rolling.
[0021]
And the manufacturing method of the aluminum alloy plate for can bodies of invention of Claim 8 is manufactured by the process prescribed | regulated in Claim 3, using the alloy of the same component composition as the ingredient composition prescribed | regulated in Claim 6 as raw material aluminum alloy. Is.
[0022]
In addition, in the method of the said Claims 1-8 , after performing final cold rolling with the rolling rate of 60% or more, the final annealing which hold | maintains 0.5 hours or more at the temperature within the range of 80-200 degreeC is further carried out. The invention of claim 9 defines this.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
First, the reasons for limiting the component composition of the aluminum alloy used in the method of the present invention will be described.
[0024]
Mg:
The addition of Mg is effective in improving the strength due to the solid solution of Mg itself, and can be expected to improve the strength by increasing the work hardening amount due to the solid solution of Mg, and further, Mg 2 Si by coexisting with Si. Therefore, Mg is an indispensable element for obtaining the strength required as a can body material. Mg also has an effect of multiplying dislocations during processing, and is therefore effective for making recrystallized grains finer. However, if the amount of Mg is less than 0.5%, the above-mentioned effect is small. On the other hand, if it exceeds 2.0%, high strength can be easily obtained, but the deformation resistance during DI processing increases and the drawability and squeezing property are improved. Make it worse. Therefore, the Mg content is set in the range of 0.5 to 2.0%.
[0025]
Mn:
Mn is an effective element that contributes to improvement in strength and formability. In particular, Mn is particularly important for the can body material, which is the intended application of the present invention, because ironing is applied during DI molding. Emulsion-type lubricants are usually used in ironing of aluminum plates, but if there are few Mn-based crystallized products, even if they have the same level of strength, the emulsion-type lubricants alone are not sufficient for lubrication. In addition, appearance defects such as scuffing or seizure called goling may occur. This phenomenon is known to be affected by the size, amount, and type of the crystallized product, and Mn is an indispensable element for forming the crystallized product. If the amount of Mn is less than 0.5%, the effect of solid lubrication by the Mn-based compound cannot be obtained. On the other hand, if the amount of Mn exceeds 2.0%, a primary intermetallic compound of Al 6 Mn is generated, which is markedly formed. Impairs sex. Therefore, the amount of Mn is set in the range of 0.5 to 2.0%.
[0026]
Fe:
Fe is an element necessary for accelerating crystallization and precipitation of Mn to control the amount of Mn solid solution in the aluminum matrix and the dispersion state of the Mn-based intermetallic compound. In order to obtain an appropriate compound dispersion state, it is necessary to add Fe according to the amount of Mn added. If the amount of Fe is less than 0.1%, it is difficult to obtain a proper compound dispersion state. On the other hand, if the amount of Fe exceeds 0.7%, a primary giant intermetallic compound is likely to be generated with the addition of Mn. Thus, the moldability is remarkably impaired. Therefore, the range of Fe content is set to 0.1 to 0.7%.
[0027]
Si:
The addition of Si contributes to improvement of the strength of the can body material through age hardening by precipitation of Mg2 Si-based compounds. Si is an element necessary for generating an Al—Mn—Fe—Si intermetallic compound and controlling the dispersion state of the Mn intermetallic compound. If the amount of Si is less than 0.05%, the above effect cannot be obtained. On the other hand, if it exceeds 0.5%, the material becomes too hard due to age hardening, thereby impairing the moldability. Therefore, the range of Si content is set to 0.05 to 0.5%.
[0028]
Ti, B:
In a normal aluminum alloy, a small amount of Ti or Ti and B is added for ingot crystal grain refinement. Also in this invention, a small amount of Ti is used alone or as required. B may be added in combination with B. However, if the amount of Ti is less than 0.005%, the effect cannot be obtained, and if it exceeds 0.20%, a huge Al-Ti intermetallic compound crystallizes and inhibits formability. The amount of Ti was within the range of 0.005 to 0.20%. Moreover, if B is added together with Ti, the effect of refining the ingot crystal grains is improved. However, when B is added together with Ti, the effect is not obtained if the amount of B is less than 0.0001%. If exceeding, Ti—B based coarse particles are mixed to impair the moldability. Therefore, the amount of B in the case of adding B together with Ti is set in the range of 0.0001 to 0.05%.
[0029]
Cu, Cr, Zn:
These are all elements that contribute to strength improvement, and one or more selected from these are added as necessary. Each of these elements will be further described.
[0030]
Cu:
Cu is in solution in the aluminum matrix during annealing, and contributes to strength improvement using precipitation hardening by depositing as an Al-Cu-Mg-based precipitate during coating baking. If the amount of Cu is less than 0.05%, the effect cannot be obtained. On the other hand, if Cu is added in excess of 0.5%, age hardening can be easily obtained, but it becomes too hard and inhibits formability. Moreover, corrosion resistance also deteriorates. Therefore, the range of Cu content is set to 0.05 to 0.5%.
[0031]
Cr;
Cr is also an element effective in improving the strength. However, if it is less than 0.05%, the effect is small, and if it exceeds 0.3%, formability is reduced due to the formation of giant crystals, which is not preferable. Therefore, the range of Cr content is set to 0.05 to 0.3%.
[0032]
Zn:
Addition of Zn contributes to strength improvement by aging precipitation of Al—Mg—Zn-based particles. However, if it is less than 0.05%, the effect cannot be obtained, and if it exceeds 0.5%, there is a problem regarding contribution to strength. There is no, but deteriorates the corrosion resistance. Therefore, the range of Zn content is set to 0.05 to 0.5%.
[0033]
The balance of the above elements may be inevitable impurities with Al.
[0034]
Next, the manufacturing process in this invention is demonstrated with the effect | action.
[0035]
First, an aluminum alloy ingot having the above alloy composition is cast by a DC casting method (semi-continuous casting method) or the like according to a conventional method. The ingot is then homogenized to homogenize the ingot segregation and optimize the Mn-based second phase particle size and distribution. If the homogenization treatment temperature is less than 520 ° C, the effect of homogenization is insufficient, while if it exceeds 630 ° C, eutectic melting may occur. If the homogenization treatment is less than 1 hour, homogenization is insufficient. Therefore, it is necessary to carry out the homogenization treatment for 1 hour or more at a temperature in the range of 520 to 630 ° C. The upper limit of the homogenization time is not particularly limited, but it is usually preferably 48 hours or less in consideration of economy.
[0036]
Hot rolling is performed on the slab subjected to the homogenization treatment. This hot rolling is usually divided into rough rolling and subsequent finish rolling. In the case of the method of the present invention, hot rolling start temperature conditions, that is, rough rolling start temperature conditions, and hot rolling Appropriately regulate the end temperature conditions, that is, the ascending temperature condition and ascending sheet thickness condition of finish rolling, and the cooling rate condition to room temperature after finish rolling, and further the hot rolled sheet in a state where it reaches room temperature after finish rolling. It is extremely important to appropriately control the recrystallization state. Therefore, these conditions will be described in more detail.
[0037]
(1) The hot rolling start temperature (rough rolling start temperature) is set within a range of 380 to 580 ° C.
The starting temperature of hot rolling has a strong influence on the material recovery and recrystallization behavior during hot rolling, especially the crystal structure of the cube orientation (cube orientation required for lowering the deep drawing ear of the final plate). The aggregate of crystal grains plays an important role in the formation of a cube band. When the hot rolling start temperature is less than 380 ° C., the amount of cube band formation tends to be insufficient. On the other hand, if hot rolling is started at a high temperature exceeding 580 ° C., the formation of the cube band is facilitated, but the surface quality of the plate Decreases. Therefore, the hot rolling start temperature needs to be in the range of 380 to 580 ° C.
[0038]
(2) End temperature of hot rolling (finish rolling finishing temperature) is set within a range of 200 to 330 ° C.
If the ascending temperature of hot finish rolling is less than 200 ° C, the surface quality deteriorates, and recrystallization nucleation increases around the second phase particles, and subsequent recrystallization increases the number of recrystallized grains other than the cube orientation. It is disadvantageous for low ear rate control. On the other hand, if the rising temperature exceeds 330 ° C., it becomes difficult to set the recrystallization rate to 90% or less and the proof stress to 70 MPa or more in the state of cooling to room temperature after the end of hot rolling.
[0039]
(3) The ascent thickness of the hot finish rolling is set in the range of 1.0 to 7.0 mm.
If the finishing plate thickness of finish rolling is less than 1.0 mm, it becomes difficult to ensure a sufficient rolling rate in the final cold rolling after annealing, and the strength of the final plate is likely to be insufficient. On the other hand, if the ascending plate thickness exceeds 7.0 mm, the rolling rate becomes too high in the final cold rolling after annealing, so that high strength cannot be obtained and the ear rate becomes high.
[0040]
(4) The average cooling rate from the temperature in the range of 200 to 330 ° C. immediately after the end of hot rolling to room temperature is in the range of 1 to 100 ° C./hour, desirably in the range of 1 to 70 ° C./hour.
The cooling process of the ascending material (coil) immediately after the end of hot rolling from 200 to 330 ° C. to room temperature, in particular, the cooling process to 100 ° C. is a process in which nucleation of cube-oriented recrystallized grains occurs. When the cooling rate during this time exceeds 100 ° C./hour, the nucleation of the cube orientation recrystallized grains becomes insufficient, which is disadvantageous for controlling the low ear rate of the final plate. On the other hand, when the cooling rate during that time is less than 1 ° C./hour, it is almost completely recrystallized, and it is difficult to make the recrystallization rate 90% or less and the proof stress 70 MPa or more in the state cooled to room temperature. It becomes.
[0041]
(5) The recrystallization rate of the hot-rolled sheet (hot-rolled sheet) after cooling to room temperature is 90% or less, and the proof stress is 70 MPa or more. This means that the hot rolled sheet is not completely recrystallized but is partially recrystallized.
The regulation of the recrystallization rate and the proof stress value of the hot rolled up board after cooling to room temperature is important in the method of the present invention, and these values have a great influence on the low ear rate control and appearance defects of the final board. Effect. That is, when the self-annealing progresses while cooling from room temperature in the range of 200 to 330 ° C. after the hot rolling to room temperature, the recrystallization rate exceeds 90% (that is, the complete recrystallization state or close to it) When the proof stress value is less than 70 MPa (that is, the complete annealing state or an annealing state close thereto), the effect of expanding the recrystallization structure in the cube orientation by the subsequent primary cold rolling and annealing is effective. As a result, it becomes difficult to control the final plate to a low ear ratio, and at the same time, the crystal grains of the final plate are coarsened, and appearance defects such as rough skin and flow lines during canning are likely to occur. Therefore, it is necessary to regulate the recrystallization rate in a state cooled to room temperature to 90% or less and the proof stress value to 70 MPa or more. Even within this range, the recrystallization rate is preferably 75% or less and the proof stress is preferably 90 MPa or more. In this way, the recrystallization rate in the state cooled to room temperature is mainly affected by the hot rolling end temperature, the cooling rate from the hot rolling end temperature to room temperature, and further the composition of the alloy. By appropriately adjusting these in relation to each other, the recrystallization rate at room temperature can be controlled to 90% or less, and the proof stress value in the state cooled to room temperature is the recrystallization as described above. Since the rate and the alloy composition are affected, the hot rolling finish temperature, the cooling rate to room temperature, and the alloy composition are controlled to 70 MPa or higher by appropriately adjusting the composition of the alloy in relation to each other. Can do.
[0042]
For the hot rolled sheet in the partially recrystallized state obtained so as to satisfy the above conditions (1) to (5), a light primary cold rolling with a rolling rate in the range of 2 to 25%. Apply. By subjecting the hot-rolled sheet in a partially recrystallized state to mild primary cold rolling to give a mild strain to the hot-rolled sheet, the subsequent annealing can generate and grow recrystallized grains with a cube orientation. An effect of promoting and suppressing generation and growth of recrystallized grains other than the cube orientation can be obtained.
[0043]
Here, when the rolling ratio of the primary cold rolling on the hot-rolled sheet is less than 2%, generation of recrystallized grains having a cube orientation due to insufficient strain, the effect of accelerating the growth, and generation of recrystallized grains other than the cube orientation The effect of suppressing the growth becomes insufficient. On the other hand, if the rolling rate exceeds 25%, the recrystallized grains in the cube orientation are also broken by the large amount of strain introduced, so that the cube-oriented recrystallized grain structure is sufficiently obtained. This makes it difficult to obtain the ear rate reduction effect of the final plate. Therefore, the rolling rate in the primary cold rolling for the hot-rolled sheet is set in the range of 2 to 25%.
[0044]
Thus, after performing the primary cold rolling with a rolling rate of 2 to 25% on the hot-rolled sheet, intermediate annealing is performed by continuous annealing (CAL) or batch annealing. This intermediate annealing is a process necessary to completely recrystallize the material and lower the ear ratio of the final plate after the final cold rolling.
[0045]
When applying the continuous annealing to the intermediate annealing after the primary cold rolling, the continuous annealing is heated to a temperature in the range of 330 to 620 ° C. with an average temperature increase rate in the range of 1 to 100 ° C./second, It is set as the conditions which cool with the average cooling rate within the range of 1-100 degree-C / sec after holding | maintenance without holding or 10 minutes or less. Here, if the average heating rate and the average cooling rate are less than 1 ° C./second, the productivity decreases in the continuous annealing (CAL) method, and the average heating rate and the average cooling rate exceed 100 ° C./second. Is disadvantageous for the formation of recrystallized grains with cube orientation. Further, if the temperature reached by heating is less than 330 ° C., recrystallization is unlikely to occur, whereas if the temperature exceeds 620 ° C., eutectic melting may occur. Furthermore, holding at 330 to 620 ° C. for more than 10 minutes inhibits the productivity of continuous annealing.
[0046]
On the other hand, when batch annealing is applied as intermediate annealing after primary cold rolling, heating is performed at an average temperature increase rate of 0.1 ° C./second or less to a temperature in the range of 250 to 500 ° C., and 0 in the temperature range. Hold for 5 hours or more and cool at an average cooling rate of 0.1 ° C./second or less. Here, if the average heating rate and the average cooling rate exceed 0.1 ° C./second, there arises a problem that the whole hot rolled plate coil cannot be uniformly heated or cooled by the batch annealing method. Further, when the heating and holding temperature is less than 250 ° C, it is difficult to completely recrystallize, while at a temperature exceeding 500 ° C, the recrystallization nucleus becomes coarse, and surface defects such as rough skin and flow lines are likely to occur during canning. Become. Further, if the heating and holding time is less than 0.5 hours, it is difficult to completely recrystallize, and it becomes difficult to uniformly heat the entire coil of the hot rolled sheet. The upper limit of the heating and holding time in the case of batch annealing is not particularly defined, but is usually within 24 hours from the viewpoint of economy.
[0047]
As described above, after performing the intermediate annealing by continuous annealing or batch annealing, cold rolling is performed in order to obtain a final sheet thickness and necessary strength. Here, when the final cold rolling reduction is less than 60%, the strength increase due to work hardening is small, and it is difficult to obtain the strength necessary for the final plate for the can body material.
[0048]
The cold-rolled plate may be used as it is as a final plate for DI molding, but the cold-rolled plate may be subjected to final annealing at a temperature in the range of 80 to 200 ° C. for 0.5 hour or longer as necessary. May be performed. This final annealing is aimed at improving the formability by recovering the ductility, but if the temperature is less than 80 ° C, the effect of improving the formability is not sufficiently obtained, while if it exceeds 200 ° C, the strength due to softening is obtained. If the decrease is large and the annealing time is less than 0.5 hours, the effect of improving the formability cannot be obtained sufficiently. The upper limit of the annealing time is not particularly defined, but is preferably 10 hours or less from the viewpoint of productivity and economy.
[0049]
【Example】
Each alloy of metal symbols A to F shown in Table 1 was cast into a slab by a DC casting method according to a conventional method. Then, after performing homogenization treatment, hot rolling was performed by hot rough rolling and hot finish rolling. Detailed conditions of hot rolling are shown in production numbers 1 to 7 in Table 2. Further, the hot-rolled sheet after cooling to room temperature was subjected to primary cold rolling under the conditions shown in Table 3, followed by continuous annealing or batch annealing as intermediate annealing, and then final cold rolling was performed. In addition, after the last cold rolling, the final annealing was performed except the case of the production numbers 3 and 5.
[0050]
About the aluminum alloy plate for can bodies obtained as described above, the mechanical properties (tensile strength TS, proof stress YS, elongation EL) and coating baking (baking) of the base plate were assumed at 200 ° C. for 20 minutes. The mechanical properties after the heat treatment were examined. The base plate was subjected to a cup deep drawing test under the conditions of a punch diameter of 48 mm, a blank diameter of 93 mm, and a clearance of 30%, and the ear rate was examined. Here, with regard to the strength, a value of 270 MPa or more is required as the proof strength after baking (baking), and if the ear rate exceeds 3%, it is known that troubles during can manufacturing are likely to occur. It has been.
[0051]
Further, as a DI can moldability evaluation, can tearability, mouth spreadability (flange moldability), seamability, and appearance defects were examined. Here, regarding can breakability, the state of occurrence of can breakage after continuous 10,000 cans without harsh ironing was investigated, and regarding the spreadability, flange formability after four-stage necking was examined, and seaming was further performed. For seamability, the seaming workability after four-stage necking was investigated, and for appearance defects, the appearance of flow line-like appearance defects along the rolling direction of the can body wall of the DI can and vertical stripes in the DI direction were observed. The relative evaluation was made with 相 対 to ×. These results are shown in Table 4.
[0052]
[Table 1]
[Table 2]
[Table 3]
[Table 4]
In Tables 1 to 4, production numbers 1 to 5 are all manufactured within the component composition range defined in the present invention while satisfying the production process conditions defined in the present invention. As shown in Fig. 5, the ear rate is surely below 3% and a sufficiently low ear rate can be achieved, and the strength after baking is 270 MPa or more, and the DI moldability is also good. It is clear that it is excellent.
[0057]
On the other hand, in the production number 6, the alloy component composition is within the range specified in the present invention, but the manufacturing process condition is out of the range defined in the present invention. That is, in the process of production number 6, the recrystallization in a state where the hot rolling ascending temperature is 340 ° C., exceeds the range of 200 to 330 ° C. defined in the present invention, and is cooled to room temperature after the hot rolling is finished. The rate is 100%, exceeds the upper limit of 90% of the recrystallization rate of the present invention, the proof stress is 66 MPa, which is lower than the lower limit of 70 MPa defined by the present invention, and the primary cold rolling rate is 30%. In this case, the ear rate of the final plate was as high as 5.8%, and the can openability and spreadability were inferior.
[0058]
Production number 7 is an example using an alloy F having an Mg content of 0.47%, which is lower than the lower limit of the Mg content of the alloy defined in the present invention. In this case, the strength after baking is low and the ear rate is also low It was high and was inferior to cans.
[0059]
【The invention's effect】
As is apparent from the above-described embodiments, according to the method of the present invention, the DI can barrel material has high strength enough to withstand the thinning of the can barrel, and at the same time, DI moldability, particularly flange. It is possible to reliably obtain an aluminum alloy plate that is excellent in formability and has a stable and low deep drawing ratio.
Claims (9)
６０％以上の圧延率で最終冷間圧延を行なった後、さらに８０〜２００℃の範囲内の温度で０．５時間以上保持する最終焼鈍を施すことを特徴とする、缶胴用アルミニウム合金板の製造方法。In the manufacturing method of the aluminum alloy plate for can bodies according to any one of claims 1 to 8 ,
An aluminum alloy sheet for a can body, which is subjected to final annealing at a temperature in the range of 80 to 200 ° C. for 0.5 hour or more after final cold rolling at a rolling rate of 60% or more. Manufacturing method.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP07654498A JP3713614B2 (en) | 1998-03-10 | 1998-03-10 | Method for producing aluminum alloy plate for can body |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP07654498A JP3713614B2 (en) | 1998-03-10 | 1998-03-10 | Method for producing aluminum alloy plate for can body |
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| JPH11256292A JPH11256292A (en) | 1999-09-21 |
| JP3713614B2 true JP3713614B2 (en) | 2005-11-09 |
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| US6458224B1 (en) * | 1999-12-23 | 2002-10-01 | Reynolds Metals Company | Aluminum alloys with optimum combinations of formability, corrosion resistance, and hot workability, and methods of use |
| JP2001262261A (en) * | 2000-03-22 | 2001-09-26 | Furukawa Electric Co Ltd:The | Aluminum alloy sheet for can barrel excellent in can bottom formability and its producing method |
| JP2006152371A (en) * | 2004-11-29 | 2006-06-15 | Furukawa Sky Kk | Aluminum alloy for food can having excellent casting-crack resistance |
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