JP3871462B2

JP3871462B2 - Method for producing aluminum alloy plate for can body

Info

Publication number: JP3871462B2
Application number: JP03090699A
Authority: JP
Inventors: 旭日比野; 政文溝内; 尚幸佐久間
Original assignee: Furukawa Sky Aluminum Corp
Current assignee: Furukawa Sky Aluminum Corp
Priority date: 1999-02-09
Filing date: 1999-02-09
Publication date: 2007-01-24
Anticipated expiration: 2019-02-09
Also published as: JP2000234158A

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ＪＩＳ３００４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、ＤＩ缶製造時におけるフランジ成形性（口拡げ性）、しごき性（缶切れ性）も重要であり、これらの耳率、フランジ成形性、しごき性、および強度を缶胴材に要求される主要４要素と称することができ、これらの４要素をバランス良く向上させることが強く望まれている。特に耳率は、これらの４要素のうちでもその制御が難しく、したがってこれらの４要素のバランスの改善には、耳率の適切な制御が極めて重要な課題となっている。
【０００７】
ここで、従来一般の熱間圧延方式としては、粗圧延機、仕上圧延機としてそれぞれリバーシング・ミル、リバーシング・ウォームミルを適用するか、あるいは粗圧延および仕上圧延兼用の圧延機としてリバーシング・ミルを用いることが多いが、これらの熱間圧延方式では、一般に耳率を改善しようとすれば、特にフランジ成形性の低下を招く問題が生じ、また逆にフランジ成形性を向上させようとすれば耳率を抑えることが困難となり、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となる。
【０００８】
一方、耳率を改善するための缶胴材製造方法として、既に特開平５−３１７９１４号では、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、焼鈍を２回行なうために製造コストの上昇を招き、さらには製缶時の材料の加工硬化量が大きくなってフランジ成形性が悪化する問題もある。
【０００９】
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、熱間圧延機としてリバーシング・ミルを用いた場合に、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、しごき性に優れ、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。
【００１０】
【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、熱間圧延における材料の再結晶、特に熱間圧延中途以降における各圧延パスでの再結晶状態を厳密に制御し、かつ得られた熱間圧延板に対し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。
【００１１】
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％（重量％、以下同じ）、Ｍｎ０．５〜２．０％、Ｆｅ０．１〜０．７％、Ｓｉ０．０５〜０．５％を含有し、さらに必要に応じて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鋳造した後、５２０〜６３０℃の範囲内の温度で１時間以上の均質化処理を施し、さらにリバーシング・ミルを用いて熱間圧延を行なうにあたり、
（１）３５０〜５８０℃の範囲内の温度で熱間圧延を開始し、
（２）熱間圧延中途の板厚が２０〜２００ｍｍの範囲内の段階で、表面から５０μｍの深さまでの領域に再結晶率３０％以上の再結晶を少なくとも１回生じさせ、
（３）熱間圧延中途の板厚が２０ｍｍ以上の段階から熱間圧延終了までの間の総熱間圧延率を９８％以下とし、かつその間における各圧延パスでの圧延温度を２２０〜４５０℃の範囲内とするとともに各圧延パスでの歪み速度を２〜３５０／ｓｅｃの範囲内とし、しかも各圧延パス間の材料滞留時間を１０分以内として、熱間圧延中途の板厚が２０ｍｍ以上の段階から熱延終了までの間の各圧延パス（但し最終パスを除く）における次パス開始直前までの再結晶率を１〜８０％の範囲内に制御し、
（４）熱間圧延の終了温度を２００〜３３０℃の範囲内、終了板厚を１．０〜７．０ｍｍの範囲内とし、
（５）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１００℃／ｈｒ以下とし、
（６）以上の（１）〜（５）により、熱間圧延終了後の室温に冷却された状態での再結晶率を９５％以下、耐力を７０ＭＰａ以上に制御し、
その後、熱間圧延板に対して、２〜６０％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５０％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。
【００１２】
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、さらに必要に応じて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。
【００１３】
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５０％以上の圧延率で最終冷間圧延を行なうものである。
【００１４】
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。
【００１５】
なお、以上の請求項１〜４の方法において、５０％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０．１〜２４時間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５の発明である。
【００１６】
【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。
【００１７】
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。
【００１８】
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、ゴーリングと称さ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。ゴーリングは晶出物の大きさ、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。
【００１９】
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。適切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％未満では適切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。
【００２０】
Ｓｉ：
Ｓｉの添加は、Ｍｇ₂Ｓｉ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。
【００２１】
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。
【００２２】
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。
【００２３】
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。
【００２４】
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。
【００２５】
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。
【００２６】
以上の各元素の残部はＡｌと不可避不純物とすれば良い。
【００２７】
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。
【００２８】
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。
【００２９】
均質化処理を施したスラブに対しては、熱間圧延機としてリバーシング・ミル（リバーシング・ウォームミルを含む）を用いて熱間圧延を行なう。具体的には、［０００７］欄に記載したと同様に、粗圧延機、仕上圧延機としてそれぞれリバーシング・ミル（リバーシング・ウォームミルを含む）を用いるか、または粗圧延、仕上圧延兼用の圧延機としてそれぞれリバーシング・ミル（リバーシング・ウォームミルを含む）を用いて熱間圧延を行なう。缶胴材の製造工程中においては、熱間圧延は、再結晶挙動の制御を通じて耳率の制御に重要な影響を及ぼす。そこでこの発明では、熱間圧延開始温度や熱間圧延終了温度のみならず、少なくとも板厚が２０ｍｍ以降の段階での各圧延パスの条件などを厳密に細かく規定することによって、再結晶挙動を厳密に制御している。以下に熱間圧延工程における各条件についてさらに詳細に説明する。
【００３０】
（１）熱間圧延開始温度を３５０〜５８０℃の範囲内とする。
【００３１】
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３５０℃未満では圧延集合組織を発達させ易いが、熱間圧延中に板のエッジ割れが生じやすくなり、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３５０〜５８０℃の範囲内とする必要がある。
【００３２】
（２）熱間圧延中途の板厚が２０〜２００ｍｍの範囲内の段階で、表面から５０μｍの深さまでの領域（表層領域）に３０％以上の再結晶率で少なくとも１回の再結晶を生じさせる。
【００３３】
熱間圧延中途における板厚が２０〜２００ｍｍの範囲内の段階での表層領域の回復や再結晶は、最終板の耳率にはそれほど大きな影響を与えないが、表面品質、エッジ割れの改善に影響があり、この表層領域で３０％以上の再結晶を少なくとも１回以上生じさせておくことにより、最終板の表面品質の向上とエッジ割れの防止に有効となり、ひいてはフランジ成形性、しごき性の向上に寄与する。ここで、３０％以上の再結晶が生じた領域が表面から５０μｍ未満の浅い領域に過ぎない場合や、表面から５０μｍの深さの領域の再結晶率が３０％未満の場合には、上記の効果を充分に得ることができない。
【００３４】
（３）熱間圧延中途の板厚が少なくとも２０ｍｍ以上の段階から熱間圧延終了までの間において、圧延パス（但し最終パスを除く）における次パス開始直前までの再結晶率を１〜８０％の範囲内に制御する。そしてこのように板厚が２０ｍｍ以上の段階以降の各圧延パスにおいて１〜８０％の再結晶率を確保するために、熱間圧延中途の板厚が２０ｍｍ以上の段階から熱間圧延終了までの間の総熱間圧延率を９８％以下とし、かつその間における各圧延パスでの圧延温度を２２０〜４５０℃の範囲内とするとともに、その間における各圧延パスでの歪み速度を２〜３５０／ｓｅｃの範囲内とし、しかも各圧延パス間での材料滞留時間を１０分以内とする。
【００３５】
少なくとも板厚が２０ｍｍ以上の段階以降の各圧延パスにおける圧延中の再結晶率は、集合組織の制御に重要な影響を及ぼし、その間の各圧延パスにおける再結晶率を１〜８０％の範囲内、望ましくは５〜４０％の範囲内に制御することによって、熱間圧延終了後の材料のキューブ方位密度を高め、最終板の４５°耳を低くして低耳率を達成することが可能となる。なおここで規定している各圧延パスにおける再結晶率は、その圧延パスの開始から次パスでの圧延が開始される直前までに生じる再結晶を体積率で表したものである。ここで、板厚が２０ｍｍの段階以降の各圧延パスのうち、１パスでも再結晶率が８０％を越えたりあるいは１％未満となれば、熱間圧延終了後のキューブ方位結晶粒の密度が低下し、最終板の４５°耳が高くなってしまう。また板厚が２０ｍｍより厚い段階における各圧延パスにおける再結晶率は、最終板の耳率には大きな影響を与えない。但し、板厚が２０ｍｍよりも大きい段階から各圧延パスの再結晶率を前述のように制御しても特に不都合を招くことはなく、そこでこの発明では、熱間圧延中途の板厚が２０ｍｍ以上の段階から後の各圧延パスにおける再結晶率を規定している。
【００３６】
上述のように板厚が２０ｍｍ以上の段階以降の各圧延パスにおける再結晶率を１〜８０％、好ましくは５〜４０％の範囲内に制御するためには、圧延温度と、各圧延パスの歪み速度と、各圧延パス間の材料滞留時間を適切に制御する必要がある。すなわち、板厚が２０ｍｍ以上の段階以降において、先ず圧延温度を２２０〜４５０℃の範囲内とし、また各圧延パスの歪み速度を２〜３５０／ｓの範囲内とし、さらに各圧延パス間における滞留時間（前の圧延パスにおける圧延終了から次の圧延パスにおける圧延開始までの時間）を１０分以内とする必要がある。ここで、板厚が２０ｍｍ以上の段階以降での圧延温度が２２０℃未満では、前述の再結晶率の下限を確保することが困難となるばかりでなく、圧延中に板のエッジ割れが生じるおそれがあり、一方４５０℃を越えれば再結晶率が上限を越えるおそれがある。また各圧延パスにおける歪み速度が２／ｓｅｃ未満となれば、前述の再結晶率の下限を確保することが困難となるばかりでなく、生産性も著しく低下してしまい、一方各圧延パスにおける歪み速度が３５０／ｓｅｃを越えれば、表面品質が低下してしまうおそれがある。さらに各圧延パスの間における材料の滞留時間が１０分を越えれば、その滞留時間中に再結晶が進行して、各圧延パスでの再結晶率が上限を越えてしまうおそれがあり、また生産性も著しく低下してしまう。
【００３７】
（４）熱間圧延終了温度を２００〜３３０℃の範囲内とし、かつ熱間圧延終了時の板厚を１．０〜７．０ｍｍの範囲内とする。
【００３８】
熱間圧延の終了温度（上がり温度）が２００℃未満では、表面品質が低下するばかりでなく、第２相粒子周辺での再結晶核生成密度が増加して、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。一方熱間圧延終了温度が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９５％以下、耐力を７０ＭＰａ以上とすることが困難となってしまう。また熱間圧延終了時の板厚（上がり板厚）が１．０ｍｍ未満では、熱間圧延機における板厚精度の制御が困難となり、一方熱間圧延終了板厚が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、高強度は容易に得られるものの、４５°耳が高くなって、耳率が大きくなってしまう。
【００３９】
（５）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１００℃／時間以下とする。
【００４０】
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。なお熱間圧延終了直後の２２０〜３３０℃の範囲内の温度から室温までの平均冷却速度の下限は特に限定しないが、１℃／時間以上とすることが好ましい。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９５％以下、耐力値を７０ＭＰａ以上とすることが困難となるおそれがある。
【００４１】
（６）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９５％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。
【００４２】
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なポイントであり、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９５％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には、その後の１次冷間圧延と焼鈍により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９５％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９５％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。
【００４３】
以上の（１）〜（６）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２〜６０％の範囲内の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１次冷間圧延を施して熱延板に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。
【００４４】
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６０％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２〜６０％の範囲内とした。ここで、特にこの発明においては、１次冷間圧延の圧延率が２〜６０％という広い範囲で許容されることが重要であり、このような広い範囲内で１次冷間圧延率を最適に調整することによって、最終板における低耳率のみならず、前述の缶胴材に要求される４要素のバランスを向上させることが可能となった。なおこのように１次冷間圧延率に広い範囲が許容されるようになったのは、既に述べたように熱間圧延条件を厳密に規制して、耳率制御に有利となるように熱間圧延工程での再結晶状態を適切に制御したことによるのである。
【００４５】
前述のように熱延板に対して圧延率２〜６０％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。
【００４６】
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。
【００４７】
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。
【００４８】
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、５０％以上の圧延率で、最終冷間圧延を施す。ここで、最終冷間圧延の圧延率が５０％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。
【００４９】
最終冷間圧延後の板は、これを最終板としてそのままＤＩ成形に供しても良いが、最終冷間圧延後の板に必要に応じて８０〜２００℃の範囲内の温度で０．５〜２４時間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ず、さらに焼鈍時間が２４時間を越えれば、成形性向上効果が飽和し、生産性、経済性を損なうだけである。なお積極的に最終焼鈍を行なわない場合でも、最終冷間圧延を高速で行なうことにより発生する加工熱を利用して、前記同様な焼鈍効果を得ることができる。
【００５０】
【実施例】
表１に示す合金記号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、リバーシング・ミルを用いて熱間圧延を施した。熱間圧延の詳細な条件を表２〜表４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、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には、製造番号１，３，５の場合を除いて最終焼鈍を施した。１次冷間圧延後の詳細な条件を表５の製造番号１〜７に示す。
【００５１】
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、２５０ＭＰａ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。
【００５２】
さらにＤＩ缶成形性評価として、缶切れ性（しごき性）、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１〜５の５段階で相対評価した。これらの結果を表６に示す。なお表６においてＤＩ缶成形性についての５段階評価においては、数字が大きいほど良好であり、“３”のランク以上で合格と評価した。
【００５３】

【００５４】
【表２】

【００５５】
【表３】

【００５６】
【表４】

【００５７】
【表５】

【００５８】
【表６】

【００５９】
表１〜表６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２５０ＭＰａ以上で充分な強度を有しており、しかもＤＩ缶成形性、特にしごき性、フランジ成形性も優れていることが明らかである。
【００６０】
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、熱間圧延中途の板厚２５ｍｍの段階から２パス目の再結晶率が９１％と大きくなってこの発明で規定する１〜８０％の範囲を越え、かつ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、さらに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９５％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を下廻っており、この場合は最終板の耳率が５．７％と高く、さらには缶切れ性（しごき性）にも劣っていた。
【００６１】
また製造番号７は、Ｍｇが０．４５％とこの発明で規定する範囲を外れた合金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、ＤＩ成形性に劣っていた。
【００６２】
【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缶胴用材料として要求される４要素、すなわち耳率とフランジ成形性、しごき性、強度のバランスが優れたアルミニウム合金板を確実かつ安定して得ることができる。特にこの発明の方法の場合、熱間圧延条件を細かく制御することにより、低耳率を確保しながらも中間焼鈍を挟んでの２回の冷間圧延のうちの１次の冷間圧延の圧延率を広い範囲で調整することが可能となり、そのため低耳率と高い強度とを同時かつ容易に得ることが可能となった。[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. In addition, flange formability (mouth spreadability) and ironability (can tearability) at the time of DI can production are also important, and these ear ratios, flange formability, ironability, and strength are required for can bodies. It can be called four main elements, and it is strongly desired to improve these four elements in a balanced manner. In particular, it is difficult to control the ear rate among these four elements. Therefore, appropriate control of the ear rate is an extremely important issue for improving the balance of these four elements.
[0007]
Here, as a conventional general hot rolling method, a reversing mill and a reversing worm mill are applied as a roughing mill and a finishing mill, respectively, or a reversing as a rolling mill for both roughing and finishing rolling.・ In many cases, mills are used. However, in these hot rolling methods, in general, if the ear rate is to be improved, there is a problem that particularly deteriorates the flange formability, and conversely, the flange formability is improved. In this case, it is difficult to suppress the ear rate. For example, it is difficult to suppress the ear rate to 3% or less at the aperture ratio of 1.9.
[0008]
On the other hand, as a method for manufacturing a can body material for improving the ear rate, Japanese Patent Laid-Open No. 5-317914 has already proposed a method of performing annealing twice in the middle of cold rolling. When annealing is performed twice, the rolling ratio of the final cold rolling cannot be increased, so that there is a problem that the strength is likely to be insufficient. Further, the annealing is performed twice, resulting in an increase in manufacturing cost, and further There is also a problem that the work hardening amount of the material at the time of the can increases and the flange formability deteriorates.
[0009]
This invention was made against the background of the above circumstances, When using a reversing mill as a hot rolling mill, A material that can sufficiently satisfy various requirements for a can body material, that is, excellent in strength, flange formability and squeezability even when it is thinned, and the ear ratio of the material in deep drawing is reliably and stably low It is a basic object to provide a method capable of producing an aluminum alloy plate for a can body.
[0010]
[Means for Solving the Problems]
As a result of various experiments and examinations by the inventors of the present application in order to solve the above-described problems, the recrystallization of the material in hot rolling, particularly the recrystallization state in each rolling pass after the middle of hot rolling is strictly observed. It was found that the above-mentioned problems can be solved by performing intermediate annealing after subjecting the obtained hot-rolled sheet to primary cold rolling, and the present invention has been made. .
[0011]
Specifically, the method for producing an aluminum alloy plate for a can body of the invention of claim 1 includes Mg 0.5 to 2.0% (% by weight, hereinafter the same), Mn 0.5 to 2.0%, Fe0.1 -0.7%, containing 0.05-0.5% Si, and optionally 0.005-0.20% Ti alone or in combination with 0.0001-0.05% B And after casting an aluminum alloy consisting of Al and inevitable impurities, a homogenization treatment is performed for 1 hour or more at a temperature in the range of 520 to 630 ° C., and With reversing mill In performing hot rolling,
(1) Hot rolling is started at a temperature within the range of 350 to 580 ° C.,
(2) In the stage where the plate thickness in the middle of hot rolling is in the range of 20 to 200 mm, recrystallization having a recrystallization ratio of 30% or more is generated at least once in a region from the surface to a depth of 50 μm,
(3) The total hot rolling rate between the stage where the sheet thickness during hot rolling is 20 mm or more and the end of hot rolling is 98% or less, and the rolling temperature in each rolling pass during that period is 220 to 450 ° C. And the strain rate in each rolling pass is in the range of 2 to 350 / sec, and the material residence time between each rolling pass is within 10 minutes, and the plate thickness during hot rolling is 20 mm or more. Control the recrystallization rate until just before the next pass start in each rolling pass (excluding the final pass) from the stage to the end of hot rolling within the range of 1 to 80%,
(4) The end temperature of hot rolling is in the range of 200 to 330 ° C., the end plate thickness is in the range of 1.0 to 7.0 mm,
(5) 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 100 ° C./hr or less,
(6) By the above (1) to (5), the recrystallization rate in the state cooled to room temperature after the end of hot rolling is controlled to 95% or less and the proof stress is controlled to 70 MPa or more,
Thereafter, the hot-rolled sheet is subjected to primary cold rolling at a rolling rate within a range of 2 to 60%, and further at an average temperature increase rate within a range of 1 to 100 ° C./sec. 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 50% or more The final cold rolling is performed.
[0012]
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 Further, if necessary, 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. In addition, it is manufactured by a process of homogenization, hot rolling, primary cold rolling, continuous annealing, and final cold rolling under the same conditions as the process conditions defined in claim 1.
[0013]
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 50% or more in the same manner as in the method of claim 1.
[0014]
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.
[0015]
In addition, in the method of the above Claims 1-4, after performing the final cold rolling at a rolling rate of 50% or more, the final holding is further performed at a temperature within the range of 80 to 200 ° C. for 0.1 to 24 hours. Annealing may be performed, and this is defined in the invention of claim 5.
[0016]
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.
[0017]
Mg:
The addition of Mg is effective in improving the strength by solid solution of Mg itself, and can be expected to improve the strength by increasing the work hardening amount accompanying the solid solution of Mg. ₂ Strength improvement by aging precipitation of Si can also be expected. Therefore, Mg is an indispensable element for obtaining strength required for a can body material. Further, Mg has an effect of multiplying dislocations at the time of 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%.
[0018]
Mn:
Mn is an effective element that contributes to improvement in strength and formability. In particular, Mn is particularly important for a can body material, which is the intended use 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 and seizure called goling may occur. Goling is known to be affected by the size, amount, and type of crystallized matter, 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 compound cannot be obtained, while if the amount of Mn exceeds 2.0%, Al ₆ A primary intermetallic compound of Mn is generated, and the formability is remarkably impaired. Therefore, the amount of Mn is set in the range of 0.5 to 2.0%.
[0019]
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 Fe content is less than 0.1%, it is difficult to obtain an appropriate compound dispersion state. On the other hand, if the Fe content 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%.
[0020]
Si:
The addition of Si is Mg ₂ It contributes to improving the strength of the can body material through age hardening by precipitation of 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%.
[0021]
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%.
[0022]
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.
[0023]
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%.
[0024]
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%.
[0025]
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%.
[0026]
The balance of the above elements may be Al and inevitable impurities.
[0027]
Next, the manufacturing process in this invention is demonstrated with the effect | action.
[0028]
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.
[0029]
For slabs that have been homogenized, Using a reversing mill (including reversing worm mill) as a hot rolling mill Hot rolling is performed. Specifically, as described in the column [0007], a reversing mill (including a reversing worm mill) is used as a roughing mill and a finishing mill, respectively, or both roughing and finishing rolling are used. Hot rolling is performed using a reversing mill (including a reversing worm mill) as a rolling mill. During the manufacturing process of can bodies Is The hot rolling has an important influence on the control of the ear rate through the control of the recrystallization behavior. Therefore, in the present invention, not only the hot rolling start temperature and the hot rolling end temperature, but also the conditions of each rolling pass at the stage where the plate thickness is 20 mm or more are strictly defined, so that the recrystallization behavior is strictly controlled. Is controlling. Hereinafter, each condition in the hot rolling process will be described in more detail.
[0030]
(1) The hot rolling start temperature is set within a range of 350 to 580 ° C.
[0031]
The starting temperature of hot rolling has a strong influence on the material recovery and recrystallization behavior during hot rolling, and in particular the crystal structure of the cube orientation (cube orientation required to lower the deep drawing ear of the final plate). The aggregate of crystal grains plays an important role in the formation of a cube band. If the hot rolling start temperature is less than 350 ° C., the rolled texture is likely to develop, but the edge cracking of the plate is likely to occur during hot rolling, while if the hot rolling is started at a high temperature exceeding 580 ° C., the cube Although band formation is facilitated, the surface quality of the plate is reduced. Therefore, the hot rolling start temperature needs to be in the range of 350 to 580 ° C.
[0032]
(2) At the stage where the plate thickness in the middle of hot rolling is in the range of 20 to 200 mm, at least one recrystallization occurs at a recrystallization rate of 30% or more in a region (surface region) from the surface to a depth of 50 μm. Let
[0033]
Recovery and recrystallization of the surface layer in the stage where the plate thickness is in the range of 20 to 200 mm in the middle of hot rolling does not significantly affect the ear rate of the final plate, but it improves surface quality and edge cracking. It is effective to improve the surface quality of the final plate and prevent edge cracking by generating at least one recrystallization of 30% or more in this surface layer region. Contributes to improvement. Here, when the region where recrystallization of 30% or more has occurred is only a shallow region less than 50 μm from the surface, or when the recrystallization rate of the region 50 μm deep from the surface is less than 30%, The effect cannot be obtained sufficiently.
[0034]
(3) Between the stage where the plate thickness in the middle of hot rolling is at least 20 mm or more and the end of hot rolling, the recrystallization rate in the rolling pass (excluding the final pass) immediately before the start of the next pass is 1 to 80%. Control within the range. And in order to secure a recrystallization rate of 1 to 80% in each rolling pass after the stage where the plate thickness is 20 mm or more in this way, from the stage where the plate thickness during hot rolling is 20 mm or more to the end of hot rolling. The total hot rolling rate in the meantime is 98% or less, and the rolling temperature in each rolling pass in the meantime is in the range of 220 to 450 ° C., and the strain rate in each rolling pass in the meantime is 2 to 350 / sec. In addition, the material residence time between the rolling passes is within 10 minutes.
[0035]
At least the recrystallization rate during rolling in each rolling pass after the stage where the plate thickness is 20 mm or more has an important influence on the control of the texture, and the recrystallization rate in each rolling pass during that time is in the range of 1 to 80%. By controlling within the range of 5 to 40%, it is possible to increase the cube orientation density of the material after the hot rolling and lower the 45 ° ear of the final plate to achieve a low ear rate. Become. In addition, the recrystallization rate in each rolling pass prescribed | regulated here represents the recrystallization produced from the start of the rolling pass to just before the start of the rolling in the next pass by the volume rate. Here, if the recrystallization rate exceeds 80% or less than 1% in each rolling pass after the stage where the plate thickness is 20 mm, the density of the cube-oriented crystal grains after the hot rolling is finished is Lowers and the 45 ° ears of the final plate become higher. Further, the recrystallization rate in each rolling pass in the stage where the plate thickness is thicker than 20 mm does not have a great influence on the ear rate of the final plate. However, even if the recrystallization rate of each rolling pass is controlled as described above from the stage where the plate thickness is greater than 20 mm, there is no particular inconvenience, so in the present invention, the plate thickness during hot rolling is 20 mm or more. The recrystallization rate in each rolling pass after the stage is defined.
[0036]
As described above, in order to control the recrystallization rate in each rolling pass after the stage where the plate thickness is 20 mm or more in the range of 1 to 80%, preferably 5 to 40%, the rolling temperature and the rolling pass It is necessary to appropriately control the strain rate and the material residence time between each rolling pass. That is, after the stage where the plate thickness is 20 mm or more, first, the rolling temperature is set within the range of 220 to 450 ° C., the strain rate of each rolling pass is set within the range of 2 to 350 / s, and the residence between the rolling passes is further set. The time (time from the end of rolling in the previous rolling pass to the start of rolling in the next rolling pass) needs to be within 10 minutes. Here, if the rolling temperature after the stage where the plate thickness is 20 mm or more is less than 220 ° C., not only is it difficult to ensure the lower limit of the recrystallization rate described above, but edge cracking of the plate may occur during rolling. On the other hand, if it exceeds 450 ° C., the recrystallization rate may exceed the upper limit. Further, if the strain rate in each rolling pass is less than 2 / sec, not only will it be difficult to ensure the lower limit of the recrystallization rate described above, but productivity will be significantly reduced, while strain in each rolling pass will be reduced. If the speed exceeds 350 / sec, the surface quality may deteriorate. Furthermore, if the residence time of the material between the rolling passes exceeds 10 minutes, recrystallization proceeds during the residence time, and the recrystallization rate in each rolling pass may exceed the upper limit. The properties are also significantly reduced.
[0037]
(4) The hot rolling end temperature is in the range of 200 to 330 ° C., and the plate thickness at the end of the hot rolling is in the range of 1.0 to 7.0 mm.
[0038]
When the end temperature (rising temperature) of hot rolling is less than 200 ° C., not only the surface quality is deteriorated, but also the recrystallization nucleation density around the second phase particles is increased, and the subsequent recrystallization is not in the cube orientation. This is disadvantageous for low ear rate control. On the other hand, if the hot rolling end temperature exceeds 330 ° C., it becomes difficult to make the recrystallization rate 95% or less and the proof stress 70 MPa or more in the state cooled to room temperature after the hot rolling. Also, if the plate thickness at the end of hot rolling (rising plate thickness) is less than 1.0 mm, it is difficult to control the plate thickness accuracy in the hot rolling mill, while if the plate thickness after hot rolling exceeds 7.0 mm, In the final cold rolling after annealing, the rolling rate becomes too high and high strength can be easily obtained, but the 45 ° ear becomes high and the ear rate becomes large.
[0039]
(5) The average cooling rate from the temperature within the range of 200 to 330 ° C. immediately after the end of hot rolling to room temperature is set to 100 ° C./hour or less.
[0040]
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. The lower limit of the average cooling rate from the temperature in the range of 220 to 330 ° C. immediately after the end of hot rolling to room temperature is not particularly limited, but is preferably 1 ° C./hour or more. If the cooling rate during that time is less than 1 ° C./hour, recrystallization will occur almost completely, making it difficult to achieve a recrystallization rate of 95% or less and a proof stress of 70 MPa or more when cooled to room temperature. There is a fear.
[0041]
(6) The recrystallization rate of the hot-rolled sheet (hot-rolled sheet) after cooling to room temperature is 95% 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.
[0042]
Regulation of the recrystallization rate and the proof stress value of the hot-rolled up-slab cooled to room temperature is an important point in the method of the present invention. affect. 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 95% (that is, at or near the complete recrystallization state) If the recrystallization state) or the proof stress value is less than 70 MPa, the effect of expanding the recrystallized structure in the cube orientation cannot be obtained by the subsequent primary cold rolling and annealing. It becomes difficult to control the rate, 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 95% 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 95% 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 component composition have an effect, as described above, the hot rolling finish temperature, the cooling rate to room temperature, and the alloy component composition should be controlled to 70 MPa or more by appropriately adjusting them in relation to each other. Can do.
[0043]
For the hot-rolled sheet in the partially recrystallized state obtained so as to satisfy the above conditions (1) to (6), primary cold rolling within a range of 2 to 60% is applied. . In this way, by subjecting the hot-rolled sheet in the partially recrystallized state to primary cold rolling to give distortion to the hot-rolled sheet, the subsequent annealing promotes the generation and growth of recrystallized grains with cube orientation. An effect of suppressing generation and growth of recrystallized grains other than the orientation can be obtained.
[0044]
Here, when the rolling ratio of the primary cold rolling on the hot-rolled sheet is less than 2%, the generation of recrystallized grains having a cube orientation due to insufficient strain, the effect of accelerating the growth, and the 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 60%, the recrystallized grains in the cube orientation are also destroyed 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 60%. Here, particularly in the present invention, it is important that the rolling rate of primary cold rolling is allowed in a wide range of 2 to 60%, and the primary cold rolling rate is optimal within such a wide range. As a result of the adjustment, it is possible to improve not only the low ear ratio in the final plate but also the balance of the four elements required for the can body material described above. The wide range of the primary cold rolling rate has been allowed in this way as described above. The hot rolling conditions are strictly regulated as described above, so that the hot rolling rate can be advantageously controlled. This is because the recrystallization state in the hot rolling process was appropriately controlled.
[0045]
As described above, after the primary cold rolling at a rolling rate of 2 to 60% is performed 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.
[0046]
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 | maintenance 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 hardly occurs. On the other hand, if the temperature exceeds 620 ° C., eutectic melting may occur. Furthermore, holding at 330-620 ° C. for more than 10 minutes inhibits the productivity of continuous annealing.
[0047]
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.
[0048]
As described above, after performing the intermediate annealing by continuous annealing or batch annealing, the final cold rolling is performed at a rolling rate of 50% or more in order to obtain a final sheet thickness and necessary strength. Here, when the rolling ratio of the final cold rolling is less than 50%, 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.
[0049]
The plate after the final cold rolling may be subjected to DI forming as it is as the final plate, but the plate after the final cold rolling may be used at a temperature in the range of 80 to 200 ° C. as necessary. A 24-hour final annealing 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 annealing time is less than 0.5 hours, the effect of improving the formability cannot be sufficiently obtained. If the annealing time exceeds 24 hours, the effect of improving the formability is saturated, and the productivity and economy are improved. It only harms sex. Even when the final annealing is not actively performed, the same annealing effect as described above can be obtained by utilizing the processing heat generated by performing the final cold rolling at a high speed.
[0050]
【Example】
Each alloy of alloy symbols A to F shown in Table 1 was cast into a slab by a DC casting method according to a conventional method. After applying homogenization, With reversing mill Hot rolling was performed. Detailed conditions of hot rolling are shown in production numbers 1 to 7 in Tables 2 to 4. Furthermore, after subjecting the hot-rolled sheet after cooling to room temperature to primary cold rolling, continuous annealing or batch annealing was performed 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 manufacturing numbers 1, 3, and 5. Detailed conditions after primary cold rolling are shown in production numbers 1 to 7 in Table 5.
[0051]
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 250 MPa or more is required as the proof strength after baking (baking), and when the ear rate exceeds 3%, it is known that troubles during can making are likely to occur. It has been.
[0052]
Further, as a DI can moldability evaluation, the can tearability (squeezing property), the mouth spreadability (flange moldability), the seaming property, and the appearance defect 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. Investigation was made and relative evaluation was performed in 5 stages of 1 to 5, respectively. These results are shown in Table 6. In Table 6, in the five-stage evaluation of DI can moldability, the larger the number, the better, and the pass was evaluated as “3” or higher.
[0053]

[0054]
[Table 2]

[0055]
[Table 3]

[0056]
[Table 4]

[0057]
[Table 5]

[0058]
[Table 6]

[0059]
In Tables 1 to 6, 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 250 MPa or more, and it has sufficient strength. In particular, it is clear that ironing and flange formability are also excellent.
[0060]
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 rate in the second pass is increased to 91% from the stage of the plate thickness of 25 mm in the middle of hot rolling, exceeding the range of 1 to 80% specified in the present invention, and hot. The rolling up temperature is 340 ° C., exceeds the range of 200 to 330 ° C. specified in the present invention, and the recrystallization rate in the state cooled to room temperature after the end of hot rolling is 100%. The upper limit of the recrystallization rate is 95% and the proof stress is 66 MPa, which is lower than the lower limit 70 MPa defined in the present invention. In this case, the final plate has a high ear rate of 5.7%. It was inferior to the ironing ability.
[0061]
Production No. 7 is an example using an alloy F having an Mg content of 0.45%, which is outside the range specified in the present invention. In this case, the strength after baking is low, the ear rate is high, and the DI moldability is high. It was inferior to.
[0062]
【The invention's effect】
As is apparent from the above-described embodiments, according to the method of the present invention, four elements required as a material for a DI can body, that is, an aluminum alloy having an excellent balance of ear ratio, flange formability, ironability, and strength. A board can be obtained reliably and stably. In particular, in the case of the method of the present invention, by controlling the hot rolling conditions finely, rolling of the first cold rolling out of the two cold rollings with intermediate annealing sandwiched while ensuring a low ear rate. It became possible to adjust the rate in a wide range, so that it was possible to obtain a low ear rate and high strength simultaneously and easily.

Claims

Contains Mg 0.5-2.0% (% by weight, the same shall apply hereinafter), Mn 0.5-2.0%, Fe 0.1-0.7%, Si 0.05-0.5%, and further if necessary After casting 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 unavoidable impurities, 520 to 630 When performing homogenization treatment for 1 hour or more at a temperature in the range of ° C. and further performing hot rolling using a reversing mill ,
(1) Hot rolling is started at a temperature within the range of 350 to 580 ° C.,
(2) In the stage where the plate thickness in the middle of hot rolling is in the range of 20 to 200 mm, recrystallization having a recrystallization ratio of 30% or more is generated at least once in a region from the surface to a depth of 50 μm,
(3) The total hot rolling rate between the stage where the sheet thickness during hot rolling is 20 mm or more and the end of hot rolling is 98% or less, and the rolling temperature in each rolling pass during that period is 220 to 450 ° C. And the strain rate in each rolling pass is in the range of 2 to 350 / sec, and the material residence time between each rolling pass is within 10 minutes, and the plate thickness during hot rolling is 20 mm or more. Control the recrystallization rate until just before the next pass start in each rolling pass (excluding the final pass) from the stage to the end of hot rolling within the range of 1 to 80%,
(4) The end temperature of hot rolling is in the range of 200 to 330 ° C., the end plate thickness is in the range of 1.0 to 7.0 mm,
(5) 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 100 ° C./hr or less,
(6) By the above (1) to (5), the recrystallization rate in the state cooled to room temperature after the end of hot rolling is controlled to 95% or less and the proof stress is controlled to 70 MPa or more,
Thereafter, the hot-rolled sheet is subjected to primary cold rolling at a rolling rate within a range of 2 to 60%, and further at an average temperature increase rate within a range of 1 to 100 ° C./sec. 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 50% or more A method for producing an aluminum alloy plate for a can body, characterized by performing final cold rolling.

Mg 0.5-2.0%, Mn 0.5-2.0%, Fe 0.1-0.7%, Si 0.05-0.5%, and Cu 0.05-0.5%, Cr0 0.05-0.3%, Zn 0.05-0.5%, or two or more of them, and if necessary, 0.005-0.20% Ti alone or 0.005%. After casting an aluminum alloy containing 0001 to 0.05% B and the balance being Al and inevitable impurities, homogenization treatment is performed for 1 hour or more at a temperature in the range of 520 to 630 ° C. Furthermore, when performing hot rolling using a reversing mill ,
(1) Hot rolling is started at a temperature within the range of 350 to 580 ° C.,
(2) In the stage where the plate thickness in the middle of hot rolling is in the range of 20 to 200 mm, recrystallization having a recrystallization ratio of 30% or more is generated at least once in a region from the surface to a depth of 50 μm,
(3) The total hot rolling rate between the stage where the sheet thickness during hot rolling is 20 mm or more and the end of hot rolling is 98% or less, and the rolling temperature in each rolling pass during that period is 220 to 450 ° C. And the strain rate in each rolling pass is in the range of 2 to 350 / sec, and the material residence time between each rolling pass is within 10 minutes, and the plate thickness during hot rolling is 20 mm or more. Control the recrystallization rate until just before the next pass start in each rolling pass (excluding the final pass) from the stage to the end of hot rolling within the range of 1 to 80%,
(4) The end temperature of hot rolling is in the range of 200 to 330 ° C., the end plate thickness is in the range of 1.0 to 7.0 mm,
(5) 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 100 ° C./hr or less,
(6) By the above (1) to (5), the recrystallization rate in the state cooled to room temperature after the end of hot rolling is controlled to 95% or less and the proof stress is controlled to 70 MPa or more,
Thereafter, the hot-rolled sheet is subjected to primary cold rolling at a rolling rate within a range of 2 to 60%, and further at an average temperature increase rate within a range of 1 to 100 ° C./sec. 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 50% or more A method for producing an aluminum alloy plate for a can body, characterized by performing final cold rolling.

Containing Mg 0.5-2.0%, Mn 0.5-2.0%, Fe 0.1-0.7%, Si 0.05-0.5%, and further 0.005-0. After casting an aluminum alloy containing 20% Ti alone or in combination with 0.0001-0.05% B with the balance being Al and unavoidable impurities, at a temperature in the range of 520-630 ° C. When performing a homogenization treatment for 1 hour or more and performing hot rolling using a reversing mill ,
(1) Hot rolling is started at a temperature within the range of 350 to 580 ° C.,
(2) In the stage where the plate thickness in the middle of hot rolling is in the range of 20 to 200 mm, recrystallization having a recrystallization ratio of 30% or more is generated at least once in a region from the surface to a depth of 50 μm,
(3) The total hot rolling rate between the stage where the sheet thickness during hot rolling is 20 mm or more and the end of hot rolling is 98% or less, and the rolling temperature in each rolling pass during that period is 220 to 450 ° C. And the strain rate in each rolling pass is in the range of 2 to 350 / sec, and the material residence time between each rolling pass is within 10 minutes, and the plate thickness during hot rolling is 20 mm or more. Control the recrystallization rate until just before the next pass start in each rolling pass (excluding the final pass) from the stage to the end of hot rolling within the range of 1 to 80%,
(4) The end temperature of hot rolling is in the range of 200 to 330 ° C., the end plate thickness is in the range of 1.0 to 7.0 mm,
(5) 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 100 ° C./hr or less,
(6) By the above (1) to (5), the recrystallization rate in the state cooled to room temperature after the end of hot rolling is controlled to 95% or less and the proof stress is controlled to 70 MPa or more,
Thereafter, the hot-rolled sheet is subjected to primary cold rolling at a rolling rate within a range of 2 to 60%, and further heated at an average heating rate of 0.1 ° C./second or less to 250 to 500 ° C. The batch is annealed at an average cooling rate of 0.1 ° C./second or less at a temperature within the range of 0.5 hours or more, and then subjected to final cold rolling at a rolling rate of 50% or more. A method for producing an aluminum alloy plate for a can body characterized by the above.

Mg 0.5-2.0%, Mn 0.5-2.0%, Fe 0.1-0.7%, Si 0.05-0.5%, and Cu 0.05-0.5%, Cr0 0.05-0.3%, Zn 0.05-0.5%, or two or more of them, and if necessary, 0.005-0.20% Ti alone or 0.005%. After casting an aluminum alloy containing 0001 to 0.05% B and the balance being Al and inevitable impurities, homogenization treatment is performed for 1 hour or more at a temperature in the range of 520 to 630 ° C. Furthermore, when performing hot rolling using a reversing mill ,
(1) Hot rolling is started at a temperature within the range of 350 to 580 ° C.,
(2) In the stage where the plate thickness in the middle of hot rolling is in the range of 20 to 200 mm, recrystallization having a recrystallization ratio of 30% or more is generated at least once in a region from the surface to a depth of 50 μm,
(3) The total hot rolling rate between the stage where the sheet thickness during hot rolling is 20 mm or more and the end of hot rolling is 98% or less, and the rolling temperature in each rolling pass during that period is 220 to 450 ° C. And the strain rate in each rolling pass is in the range of 2 to 350 / sec, and the material residence time between each rolling pass is within 10 minutes, and the plate thickness during hot rolling is 20 mm or more. Control the recrystallization rate until just before the next pass start in each rolling pass (excluding the final pass) from the stage to the end of hot rolling within the range of 1 to 80%,
(4) The end temperature of hot rolling is in the range of 200 to 330 ° C., the end plate thickness is in the range of 1.0 to 7.0 mm,
(5) 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 100 ° C./hr or less,
(6) By the above (1) to (5), the recrystallization rate in the state cooled to room temperature after the end of hot rolling is controlled to 95% or less and the proof stress is controlled to 70 MPa or more,
Thereafter, the hot-rolled sheet is subjected to primary cold rolling at a rolling rate within a range of 2 to 60%, and further heated at an average heating rate of 0.1 ° C./second or less to 250 to 500 ° C. The batch is annealed at an average cooling rate of 0.1 ° C./second or less at a temperature within the range of 0.5 hours or more, and then subjected to final cold rolling at a rolling rate of 50% or more. A method for producing an aluminum alloy plate for a can body characterized by the above.

In the manufacturing method of the aluminum alloy plate for can bodies according to any one of claims 1 to 4,
A method for producing an aluminum alloy sheet for a can body, wherein after the final cold rolling is performed, final annealing is further performed at a temperature in the range of 80 to 200 ° C for 0.1 to 24 hours.