JP2004183045A

JP2004183045A - Aluminum alloy sheet for coated tab, and its production method

Info

Publication number: JP2004183045A
Application number: JP2002351012A
Authority: JP
Inventors: Naoyuki Sakuma; 尚幸佐久間; Toshiki Muramatsu; 俊樹村松
Original assignee: Furukawa Sky KK
Current assignee: Furukawa Sky KK
Priority date: 2002-12-03
Filing date: 2002-12-03
Publication date: 2004-07-02

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum alloy sheet for a coated tab having satisfactory bending workability, without causing bent down in the tab when opening a can and obtainable of satisfactory tab performance without carrying out an annealing until the completion of cold rolling after hot rolling in the production process in particular. <P>SOLUTION: The Al alloy sheet for a coated tab comprises 3.5 to 5.5% Mg, 0.01 to 0.55% Mn, 0.02 to 0.40% Si, 0.01 to 0.20% Cr, ≤0.40% Fe, ≤0.30% Cu, and ≤0.30% Ti, and the balance substantially Al, and in which the content of solid solution Mn in a product sheet is 0.005 to 0.25%, and the number of intermetallic compounds with the maximum size of ≥5 μm lies within the range of 50 to 600 pieces/mm<SP>2</SP>. As the production method, on hot rolling after heating for an ingot at 470 to 530°C for ≤15 hr, the finishing temperature in rough rolling is controlled to 370 to 485°C, the finishing temperature in finish rolling is controlled to 280 to 350°C, the recrystallization ratio after the hot rolling is controlled to ≥85%, and, after that, cold rolling of 80 to 92% is performed. Alternatively, temper-annealing of holding the temperature at 100 to 240°C for 1 to 10 hr is further performed. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明が属する技術分野】
この発明はビールや炭酸飲料、果汁飲料等の各種飲料缶あるいは食缶、さらには日用品雑貨を収納する缶等、種々のアルミニウム缶の蓋に使用される塗装タブ用のアルミニウム合金板、特に塗装を施して使用されるタブ材用のアルミニウム合金板およびその製造方法に関するものである。
【０００２】
【従来の技術】
一般にアルミニウム缶に用いられるアルミニウム合金タブ材としては、５０８２合金や５１８２合金などの５０００系合金、すなわちＡｌ−Ｍｇ系合金が使用されることが多い。またこのようなタブ材用のアルミニウム合金板の製造方法としては、熱間圧延および冷間圧延によって所要の板厚とし、かつ熱間圧延後、あるいは冷間圧延中途において中間焼鈍を施すのが一般的である。
【０００３】
また前述のようにして得られたアルミニウム合金板を用いたタブを製造するにあたっては、耐食性や美観向上のために、塗装下地処理を行なってから表面にクリヤ塗料などを塗装焼付けして、プレス加工によってタブ形状に打抜き、また内側の指掛け部分をも打抜き、さらに強度を付与するために指掛け部分の内縁や外周縁部について１８０度曲げなどを行なってタブを製造するのが一般的である。そしてこのようにして得られたタブについては、別途製造した缶蓋のリベット部に結合して缶蓋と一体化させるのが通常である。
【０００４】
なお缶蓋の開缶方式としては、開缶時にタブを引上げて梃子の原理により缶蓋の開口部に力を加えて開口させるステイオンタブ方式や、単純にタブを引張ってその引上げ力により缶蓋の開口部を引裂くプルタブ方式のものとがある。
【０００５】
【発明が解決しようとする課題】
前述のようにアルミニウム缶のタブを製造するにあたっては、１８０度曲げという苛酷な曲げ加工を施すのが通常である。したがってタブ材には、各種成形性のうちでも特に曲げ加工性が優れていることが要求される。
【０００６】
また塗装タブは、前述のように塗装焼付け後、タブ成形が施されるが、塗装焼付けのための加熱時に軟化してその強度が低下し過ぎてしまえば、タブとしての必要強度を満たすことが困難となってしまうことがある。したがってタブ材としては、単に高強度を有するばかりでなく、耐熱軟化特性が良好であることが望まれる。
【０００７】
さらに開缶時においては、ステイオンタブ方式の場合、開缶のためにタブを引上げる際にタブ全体に曲げ応力が作用し、また特にタブのリベット部結合部分はタブを引上げる際に急激に曲げられ、さらにタブを戻す際に逆方向に曲げ戻されるのが通常であり、さらに１回の引上げ・戻しで完全には開缶されなかった際には、タブの引上げ・戻しが複数回繰返されて、繰返し曲げが加わることになる。一方プルタブ方式の場合においても、開缶方式は異なるものの、開缶時にはタブに曲げ応力が作用し、また繰返し曲げ応力が加わることも多いのが実情である。
【０００８】
そしてこのような開缶時にタブに加えられる曲げや繰返し曲げによってタブが折れてしまっては、タブとしての機能を果たし得なくなる。したがってタブの性能として、開缶時にタブの折れが生じないことが必要とされる。
【０００９】
以上のようにタブ材には、各種の成形性のうちでも特に曲げ加工性が優れていることが要求され、また塗装焼付時の耐熱軟化特性が良好で、さらに開缶時における曲げ、繰返し曲げによりタブが折れたりしないことが望まれる。
【００１０】
ここで、前述のようにタブの成形時には１８０度曲げという苛酷な曲げ加工が施されるが、この曲げ加工時に割れが発生したり、割れの起点が生じたりすれば、その影響によって、開缶時にタブに与えられる曲げ、繰返し曲げによりタブが折れてしまい、前述のようにタブとしての機能を果たし得なくなってしまう。したがってタブ材については、特に曲げ加工性が優れていることが強く望まれているのである。
【００１１】
ところでタブ材については、近年、主としてコスト低減の目的から、薄肉化を図ることが望まれており、そこで従来よりも高強度化して薄肉化する傾向が強まっており、特に欧米ではその傾向が強い。しかしながらアルミニウム合金板について単純に高強度化を図った場合、曲げ加工性が低下してしまうのが通常であり、従来のタブ材でも、曲げ加工性を損なわずに薄肉高強度化を図ることは困難であった。
【００１２】
さらにアルミニウム合金板の製造方法としては、最近では、熱間圧延後、あるいは冷間圧延中途での焼鈍（中間焼鈍）を省略したプロセスを適用して、工程数の削減により生産性の向上を図るとともに、省エネルギによりエネルギコストの低減や地球温暖化防止に対する寄与を図ることが考えられている。これは、一般には熱間圧延上りの状態で再結晶させることにより、その後の最終板厚までの工程における中間焼鈍を不要とするプロセスであるが、従来のタブ用アルミニウム合金板についてはこのようなプロセスが確立されておらず、特にタブ材としての前述のような性能に優れたタブ用アルミニウム合金板を得る方法は確立されていなかったのが実情である。
【００１３】
この発明は以上の事情を背景としてなされたもので、曲げ加工性が優れていて、曲げ加工時の割れ等に起因して開缶時にタブの折れが発生するおそれがなく、しかもタブ材として充分な強度と耐塗装焼付軟化性を有するタブ材用のアルミニウム合金板を提供すると同時に、熱間圧延上りから冷間圧延終了までの間の焼鈍を省いたプロセスで上述のようなタブ材として優れた性能を有するアルミニウム合金板を得ることができる方法を提供することを課題とするものである。
【００１４】
【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ため、本発明者が種々実験・検討を重ねた結果、タブ材用のアルミニウム合金の成分組成を適切に調整するばかりでなく、製品板における固溶Ｍｎ量と、金属間化合物の分散状態とを適切に規制することによって、前述の課題を一挙に解決し得ることを見出した。さらに製造方法として、熱間圧延条件を、粗圧延条件と仕上げ圧延条件とに分けて厳密に規制することにより、熱間圧延後または冷間圧延中途の中間焼鈍を省略して製造コスト低減等を図りつつも、前述の課題を解決したタブ材用アルミニウム合金板を製造し得ることを見出したのである。
【００１５】
したがって請求項１の発明の塗装タブ用アルミニウム合金板は、Ｍｇ３．５〜５．５％、Ｍｎ０．０１〜０．５５％、Ｓｉ０．０２〜０．４０％、Ｃｒ０．０１〜０．２０％を含有し、かつＦｅ量が０．４０％以下、Ｃｕ量が０．３０％以下、Ｔｉ量が０．３０％以下に規制され、残部がＡｌおよび不可避的不純物よりなり、しかも固溶Ｍｎ量が０．００５〜０．２５％の範囲内にあり、かつ最大径５μｍ以上の金属間化合物の数が１ｍｍ^２当り５０〜６００個の範囲内であることを特徴とするものである。
【００１６】
また請求項２の発明の塗装タブ用アルミニウム合金板の製造方法は、Ｍｇ３．５〜５．５％、Ｍｎ０．０１〜０．５５％、Ｓｉ０．０２〜０．４０％、Ｃｒ０．０１〜０．２０％を含有し、かつＦｅ量が０．４０％以下、Ｃｕ量が０．３０％以下、Ｔｉ量が０．３０％以下に規制され、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鋳塊を、４７０〜５３０℃の範囲内の温度で１５時間以下加熱した後、粗圧延および仕上げ圧延からなる熱間圧延を行なうにあたって、粗圧延の終了温度を３７０〜４８５℃の範囲内、仕上げ圧延の終了温度を２８０〜３５０℃の範囲内として、熱間圧延上りの再結晶率が８５％以上となるように熱間圧延を行ない、その後８０〜９２％の圧延率で冷間圧延を行なって、固溶Ｍｎ量が０．００５〜０．２５％の範囲内でかつ最大径５μｍ以上の金属間化合物の数が１ｍｍ^２当り５０〜６００個の範囲内の塗装タブ用アルミニウム合金板を得ることを特徴とするものである。
【００１７】
さらに請求項３の発明の塗装タブ用アルミニウム合金板の製造方法は、請求項２に記載の缶蓋塗装タブ用アルミニウム合金板の製造方法において、前記冷間圧延の後、さらに１００〜２４０℃の範囲内の温度で１〜１０時間保持の調質焼鈍を行なうことを特徴とするものである。
【００１８】
【発明の実施の形態】
先ずこの発明の塗装タブ用アルミニウム合金板に使用される合金の成分組成限定理由について説明する。
【００１９】
Ｍｇ：
Ｍｇは、この発明で対象としているタブ材として必要な強度を得るために不可欠な元素である。すなわちＭｇの添加は、Ｍｇそれ自体の固溶による強度向上に寄与し、またＭｇは転位との相互作用が大きいため、加工硬化による強度向上にも寄与する。しかしながらＭｇ添加量が３．５％未満では、タブ材として充分な強度を得ることが困難となる。一方、Ｍｇ添加量が５．５％を越えれば、冷間圧延によって導入される転位密度が多くなり過ぎ、成形中に割れが生じてしまうおそれがある。そこでＭｇ添加量は、３．５〜５．５％の範囲内とした。
【００２０】
Ｍｎ：
Ｍｎの添加は、強度向上と塗装焼付け時の軟化抑制に大きな効果がある。Ｍｎ添加量が０．０１％未満では、製品板の固溶Ｍｎ量が少な過ぎて要求強度を満たすことが困難となる。一方、Ｍｎ添加量が０．５５％を越えれば、Ａｌ−Ｍｎ−（Ｓｉ）系、Ａｌ−Ｆｅ−Ｍｎ−（Ｓｉ）系の金属間化合物の生成量が増大するとともにその金属間化合物が著しく粗大化してしまい、この発明で規定する金属間化合物の条件範囲を越えてしまい、その結果曲げ加工性が著しく低下してしまう。そこでＭｎ添加量は０．０１〜０．５５％の範囲内とした。
【００２１】
Ｓｉ：
Ｓｉの添加は、塗装焼付け時の軟化抑制に大きな効果がある。しかしながらＳｉ添加量が０．０２％未満ではその効果が充分に得られない。一方Ｓｉ添加量が０．４０％を越えれば、Ａｌ−Ｍｎ−Ｓｉ系、Ａｌ−Ｆｅ−Ｍｎ−Ｓｉ系、さらにはＭｇ_２Ｓｉの金属間化合物が生成されるとともに、その粗大化が著しくなり、この発明で規定する金属間化合物の条件範囲を越えてしまい、その結果曲げ加工性の低下をもたらす。そこでＳｉ添加量は、０．０２〜０．４０％の範囲内とした。
【００２２】
Ｃｒ：
Ｃｒの添加は強度向上と塗装焼付け時の軟化抑制に大きな効果がある。しかしながらＣｒ添加量が０．０１％未満では、その効果が現れない。一方Ｃｒ添加量が０．２０％を越えれば、Ａｌ−Ｃｒ系の金属間化合物が生成されるとともにその粗大化が生じて、この発明で規定する金属間化合物の条件範囲を越えてしまって、結果的に曲げ加工性を損ない、また冷間圧延性も阻害してしまう。したがってＣｒ添加量は、０．０１〜０．２０％の範囲内とした。
【００２３】
Ｆｅ：
Ｆｅの添加は、塗装焼付け時の軟化抑制に大きな効果がある。しかしながらＦｅ量が０．４０％を越えれば、Ａｌ−Ｆｅ−Ｍｎ−（Ｓｉ）系の金属間化合物が生成されるとともに、その金属間化合物が粗大化し、この発明で規定する金属間化合物の条件範囲を越えてしまって、結果的に曲げ加工性が低下してしまう。したがって合金中のＦｅ量は、０．４０％以下に規制することとした。
【００２４】
Ｃｕ：
Ｃｕの添加も、強度向上と塗装焼付け時の軟化抑制に大きな効果があるが、Ｃｕ量が０．３０％を越えれば、成形中に割れが発生してしまうおそれがある。そこでＣｕ添加量は、０．３０％以下に規制することとした。
【００２５】
Ｔｉ：
Ｔｉは結晶粒の微細化に有効な元素であるが、その添加量が多くなれば鋳塊組織が羽毛状晶になり難くなって、粒状晶が生成されやすくなる。このように粒状晶が生成された場合には、羽毛状晶の場合よりも粒界に晶出する金属間化合物が粗大化しやすくなり、それ自体で粗大金属間化合物を生成してしまう。そこでＴｉ量は、０．３０％以下に規制することとした。なおＴｉにＢを加えて添加する場合もあるが、その場合のＢ量は３００ｐｐｍ以下に規制することが望ましい。
【００２６】
以上の各成分のほかは、基本的にはＡｌおよび不可避的不純物とすれば良い。
【００２７】
さらにこの発明の塗装タブ用アルミニウム合金板では、合金の成分組成を前述のように調整するばかりでなく、製品板中のＭｎ固溶量を０．００５〜０．２５％の範囲内に調整することが重要である。
【００２８】
すなわち、従来のタブ用アルミニウム合金板の製造プロセスにおいては、前述のように熱間圧延後または冷間圧延の途中において、主として再結晶を目的として焼鈍（中間焼鈍）を行なうのが通常であるが、この発明の場合、製造コスト低減等のために熱間圧延後、冷間圧延終了時の最終板厚までの間に焼鈍を行なわないこととしている。このように熱間圧延後最終板厚まで焼鈍を行なわないプロセスでは、最終板では必然的に固溶Ｍｎ量が少ない状態になってしまう。そして特に固溶Ｍｎ量が０．００５％未満の極少量の場合、塗装焼付け時の軟化抑制効果が極端に小さくなり、タブとしての要求強度を満たすことが困難となってしまう。このように要求強度を満たさなければ、蓋を開けるときにタブが折れ曲がってしまうおそれがある。一方Ｍｎ固溶量の上限については、均質化処理を兼ねた加熱処理条件、熱間圧延板の組織、さらには合金成分などにも影響を受けるが、一般に０．２５％を越える固溶Ｍｎ量を得るためには、Ｍｎを、この発明で規定している添加量範囲を越えて多量に添加しなければならない。しかしながらＭｎ添加量が過剰となれば、Ａｌ−Ｍｎ−（Ｓｉ）系、Ａｌ−Ｆｅ−Ｍｎ−（Ｓｉ）系の金属間化合物の生成量が増大するとともにそれらの金属間化合物が粗大化してしまって、この発明で規定している金属間化合物の条件範囲を越えてしまい、その結果曲げ加工性の低下を招いてしまう。そこで製品板のＭｎ固溶量の上限は０．２５％とした。なおこの発明において固溶Ｍｎ量は熱フェノールろ液分析法で測定したものである。
【００２９】
さらにこの発明の塗装タブ用アルミニウム合金板においては、製品板中に存在する最大径５μｍ以上の金属間化合物について、その分布数を１ｍｍ^２当り５０〜６００個の範囲内に規制することが極めて重要である。すなわち、最大径５μｍ以上の金属間化合物の数が１ｍｍ^２当り５０個未満であれば、金属間化合物が引き起こす曲げ加工性の低下は抑えられるが、高純度地金を使用しなければならなくなって、著しいコスト上昇を招いてしまう。一方、最大径５μｍ以上の金属間化合物の数が、１ｍｍ^２当り６００個を越えれば、金属間化合物による曲げ加工性の低下が著しく顕著に現れてしまう。したがって、コスト上昇を招くことなく優れた曲げ加工性を確保するためには、最大径５μｍ以上の金属間化合物数を、１ｍｍ^２当り５０〜６００個の範囲内に規制する必要がある。ここで、最大径が５μｍに満たない微細な金属間化合物は曲げ加工性に大きな影響を与えないから、この発明では最大径５μｍ以上の金属間化合物のみ規制することとした。なおこの発明において、金属間化合物数の測定は、圧延板表面で組織観察して、画像解析処理装置ルーゼックスにより画像解析して調べた。
【００３０】
以上のように、合金の成分組成のみならず、製品板のＭｎ固溶量、最大径５μｍ以上の金属間化合物数を適切に規制することによって、次に説明するように熱間圧延後、最終板厚までの焼鈍を省略したプロセスを適用しても、曲げ加工性に優れかつ強度もタブ材として充分で耐塗装焼付け軟化性も良好な塗装タブ用アルミニウム合金板が得られるのである。
【００３１】
次にこの発明の製造方法、すなわち請求項２、請求項３の発明の方法について説明する。
【００３２】
先ず前述のような成分組成のアルミニウム合金を、ＤＣ鋳造法などの常法に従って鋳造する。そしてその鋳塊に対し、熱間圧延を行なうに先立って、４７０〜５３０℃の範囲内の温度で１５時間以下の保持の鋳塊加熱を行なう。この熱間圧延前の鋳塊加熱は、鋳塊に対する均質化処理と兼ねて行なうことが好ましい。ここで、鋳塊加熱処理の温度が４７０℃未満では、熱間圧延中に板のエッジ割れなどを引き起こしてしまい、歩留り低下、生産性低下を招いてしまう。一方鋳塊加熱の温度が５３０℃を越えれば、金属間化合物が粗大化しやすくなって、最終板における金属間化合物の条件範囲を越えてしまうおそれがある。また鋳塊加熱の保持時間が１５時間を越えた場合も、金属間化合物が粗大化しやすくなって、最終板における金属間化合物の条件範囲を越えてしまうおそれがある。そこで熱間圧延前の鋳塊加熱処理の条件は、４７０〜５３０℃の範囲内の温度で１５時間以下の保持と規定した。なおここで鋳塊加熱の温度は、加熱炉の設定温度とする。またここで加熱時間の下限は限定しておらず、要は鋳塊内部まで均一に加熱される時間であれば良いが、通常は１時間以上とすることが適当である。
【００３３】
前述のように加熱した鋳塊に対しては直ちに熱間圧延を施す。一般に熱間圧延は粗圧延と仕上げ圧延との組合せで行なうことが多く、この発明の方法の場合も、熱間粗圧延および熱間仕上げ圧延を行なって熱間圧延板とする。そしてこの発明の方法では、熱間粗圧延の終了温度を３７０〜４８５℃の範囲内、熱間仕上げ圧延の終了温度を２８０〜３５０℃の範囲内とし、熱間圧延上りの状態（熱間仕上げ圧延を行なってコイルに巻取った状態）において板の再結晶率が８５％以上となるように熱間圧延する必要がある。これらの条件を規定した理由は次の通りである。
【００３４】
すなわち、熱間粗圧延の終了温度が３７０℃より低い場合には、その後の熱間仕上げ圧延の終了温度が２８０℃を下回ってしまい、結果的に熱間圧延上りの再結晶率８５％以上を確保することが困難となってしまうおそれがある。またこのように熱間粗圧延の終了温度が３７０℃より低ければ、その後の熱間仕上げ圧延中に板のエッジ割れを引き起こしてしまうおそれがある。一方熱間粗圧延の終了温度が４８５℃を越えれば、その後の熱間仕上げ圧延終了温度が３５０℃を越えることがあり、このような高温で熱間仕上げ圧延が終了すれば、熱延コーティングが発生して、製品としての価値を損なってしまうおそれがある。したがって熱間粗圧延の終了温度は３７０〜４８５℃の範囲内とした。
【００３５】
次に熱間仕上げ圧延の終了温度が２８０℃を下回る場合には、仕上げ圧延上りの熱間圧延板の再結晶率８５％以上を確保できなくなってしまう。このように８５％以上の再結晶率を確保できない場合は、後述するように転位密度の高い領域にＭｎが析出してしまい、請求項１で規定した固溶Ｍｎ量を確保できないことがあり、その場合には、塗装焼付け時の軟化抑制効果が極端に小さくなり、タブとしての要求強度を満たすことが困難となってしまう。さらには、熱間仕上げ圧延の終了温度が２８０℃を下回って熱間圧延板の再結晶率８５％以上を確保できなかった場合、冷間圧延途中に板切れが発生して、生産性、歩留りを低下させてしまう。一方、熱間仕上げ圧延温度が３５０℃を越えれば、再結晶率８５％以上は容易に確保できるが、熱延コーティングが発生して品質低下が避けられなくなってしまう。そこで熱間仕上げ圧延終了温度は２８０〜３５０℃の範囲内とした。
【００３６】
以上のような熱間粗圧延、熱間仕上げ圧延によって得られた熱間圧延板は、熱間圧延上りの状態で、板の再結晶率が８５％以上である必要がある。ここで、熱間圧延上りで８５％以上の再結晶率を確保できなければ、転位密度の高い領域にＭｎが析出してしまい、請求項１で規定した固溶Ｍｎ量を確保できないことがあり、その場合には塗装焼付け時の軟化抑制効果が極端に小さくなり、タブとしての要求強度を満たすことが困難となってしまう。そしてこのようにタブとしての要求強度を満たさなければ、蓋を開けるときにタブが折れ曲がってしまう。さらに、熱間圧延上りの状態で板の再結晶率が８５％未満の場合、冷間圧延性が悪くなって、その後の冷間圧延で板切れが発生し、生産性、歩留りを低下させてしまうおそれがある。したがって熱間圧延上りの熱間圧延板の再結晶率は８５％以上である必要がある。
【００３７】
上述のようにして得られた再結晶率８５％以上の熱間圧延板に対しては、最終板厚まで焼鈍を施すことなく、冷間圧延によって最終板厚（製品板厚）に仕上げる。すなわち、熱間圧延後や冷間圧延の中途において中間焼鈍を施すことなく、冷間圧延によって製品板厚まで仕上げる。
【００３８】
この冷間圧延は、圧延率を８０〜９２％の範囲内とする必要がある。すなわち冷間圧延率が８０％未満では、タブに必要な強度が得られない。一方９２％を越える高い冷間圧延率では、冷間圧延によって導入される転位密度が多くなり過ぎて曲げ加工性が低下し、曲げ加工時にタブが割れたりする。そこで冷間圧延率は８０〜９２％の範囲内とする必要がある。
【００３９】
上述のようにして冷間圧延により最終板厚とされた板は、これをそのまま製品板とし、タブに使用しても良いが、場合によっては冷間圧延後、１００〜２４０℃の温度範囲で１〜１０時間保持の調質焼鈍を行なっても良い。このような調質焼鈍の条件について次に説明する。
【００４０】
調質焼鈍の温度が１００℃未満では、調質焼鈍の効果が充分に得られず、一方、２４０℃を越えれば、材料が軟化してタブの要求強度を満たすことが困難となる。また調質焼鈍の保持時間が１時間未満では、コイル全体にわたって均一な熱処理ができず、一方１０時間を越えれば、生産性の低下を招くだけでなく、軟化により強度不足を引き起こしてしまう。そのため調質焼鈍の条件は１００〜２４０℃で１〜１０時間の保持とした。
【００４１】
なお以上の製造方法によって得られる製品板は、そのＭｎ固溶量、金属間化合物分散数がそれぞれ前述の各条件を満たしている必要がある。これらの各条件を満たすための具体的な各プロセス条件は、具体的な合金の成分や他のプロセス条件との組合せによって変化するから、一義的に規定することはできないが、要は前述した鋳塊加熱処理条件、熱間圧延条件（粗圧延条件、仕上げ圧延条件、再結晶率条件）、および冷間圧延条件を満たす範囲内で、具体的な合金の成分に応じて具体的なプロセス条件を適切に組合せれば良い。
【００４２】
【実施例】
表１の合金Ｎｏ．１〜Ｎｏ．６に示す種々の化学成分のアルミニウム合金をＤＣ鋳造法によって鋳造し、得られた鋳塊について、表２の製造プロセス符号Ａ〜Ｈに示す種々のプロセス条件で鋳塊加熱−熱間圧延（粗圧延および仕上げ圧延）−冷間圧延を行ない、また一部のものについては冷間圧延後に調質焼鈍を行ない、最終板厚０．３５ｍｍの製品板（タブ用アルミニウム合金板）とした。各製品板について、仕上げ塗装を行なって、２４０℃×２４ｓで焼付け処理した。
【００４３】
各製品板について、固溶Ｍｎ量を測定するとともに、最大径５μｍ以上の金属間化合物の１ｍｍ^２当りの個数を調べた。また塗装焼付け処理後の材料強度として降伏強さＹＳを調べた。さらに曲げ、繰返し曲げが加わるタブとしての性能を次のように評価した。すなわち、各製品板をタブに加工して、各５００個作製し、ステイオンタブ方式の缶蓋に取付け、実際にタブを引上げて開口させる開口性試験を行なった。なおこの開口性試験は、缶胴に炭酸飲料を入れて炭酸飲料用缶蓋で密封し、その蓋にタブを取り付けて行なった。これらの測定結果、評価結果を表３に示す。
【００４４】
なお表３において、タブ評価は、前述のように開缶性試験を行なって、タブの割れや形状不良により開口時に１個でもタブが折れ曲がった場合を不合格として×印を付し、５００個すべてについてタブの折れ曲がりが生じることなく開口できた場合を合格として○印を付した。また塗装焼付け後の材料強度（ＹＳ）に関しては、一般に２７５Ｐａを下回った場合に開口不良が生じやすいので、この場合もＹＳが２７５Ｐａを下回る場合が不合格と判断できる。そして総合評価については、タブ性能が合格でかつＹＳが２７５Ｐａ以上の場合を合格（○印）、それ以外の場合を不合格（×印）と評価した。
【００４５】
【表１】

【００４６】
【表２】

【００４７】
【表３】

【００４８】
表３において、符号Ａ，Ｄの例は、いずれも合金の成分組成がこの発明で規定する範囲内にあり、また製造プロセスもこの発明で既定する条件を満たし、Ｍｎ固溶量条件、金属間化合物数条件もこの発明で規定する範囲を満たしたものであり、この場合はタブの折れ曲がり生じることなく、タブ性能も良好で、かつ強度も充分であり、総合的にタブ材として優れていることが確認された。
【００４９】
一方符号Ｂの例は、合金の成分組成はこの発明で規定する範囲内であるが、製造プロセスのうち鋳塊加熱処理時間が長過ぎ、最大径５μｍ以上の金属間化合物数が過剰となって、タブ性能が低下し、タブの折れ曲がりが生じてしまった。
【００５０】
さらに符号Ｃの例は、合金の成分組成はこの発明で規定する範囲内であるが、製造プロセスのうち冷間圧延率が高過ぎた例であり、この場合もタブ性能が劣ってしまった。
【００５１】
また製造符号Ｅも合金成分組成はこの発明で規定する範囲内であるが、製造プロセスのうち、熱間圧延の粗圧延終了温度、仕上げ圧延終了温度が低過ぎた例であり、この場合製品板のＭｎ固溶量が少なく、強度が不足するとともに、タブ性能も劣ってしまった。
【００５２】
さらに製造符号Ｆ，Ｇ，Ｈはいずれも合金の成分組成がこの発明で規定する範囲を外れた例であり、これらの場合は製造プロセス条件はこの発明で既定する条件を満たしながらも、強度または／およびタブ性能が劣ってしまった。なおこれらのうち、符号ＦはＭｎ、Ｃｒ、Ｔｉの添加量が過剰な例であり、製品板の固溶Ｍｎ量、最大径５μｍ以上の金属間化合物数がともに過剰となり、タブ性能が劣ってしまった。また符合ＧはＳｉ、Ｃｕ、Ｆｅの添加量が過剰であった例であり、この場合最大径５μｍ以上の金属間化合物数が過剰となり、タブ性能が劣ってしまった。さらに符号ＨはＭｇ量が過少であった例であり、この場合は強度が不足してしまった。
【００５３】
【発明の効果】
前述の実施例からも明らかなように、請求項１の発明によれば、熱間圧延後冷間圧延終了までの間の焼鈍を省略したプロセスで製造しても、曲げ加工性が良好で塗装タブとして使用した場合にタブの折れ曲がりが生じるおそれがなく、また塗装焼付けによる軟化も少なく、タブとして充分な強度を有する塗装タブ用アルミニウム合金板を得ることができる。したがって特に薄肉化を図ったタブ材として極めて有効である。また請求項２、請求項３の発明の製造方法によれば、前述のような優れた性能を有する塗装タブ用アルミニウム合金板を、熱間圧延後冷間圧延終了までの間の焼鈍を省略したプロセスで、確実かつ安定して製造することができ、またこのように熱間圧延終了から冷間圧延終了までの間に焼鈍を行なわないことから、工程数減少により製造コストの低減を図ることができるとともに、消費エネルギの低減によるエネルギコスト低減や地球温暖化防止に寄与することができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an aluminum alloy plate for a coating tab used for lids of various aluminum cans such as beer, carbonated beverage, various beverage cans or food cans such as fruit juice beverages, cans for storing daily necessities and the like, and particularly to coating. The present invention relates to an aluminum alloy plate for a tab material to be applied and used and a method for producing the same.
[0002]
[Prior art]
Generally, as an aluminum alloy tab material used for an aluminum can, a 5000 alloy such as 5082 alloy or 5182 alloy, that is, an Al—Mg alloy is often used. Further, as a method of manufacturing such an aluminum alloy sheet for a tab material, it is common to apply a required thickness by hot rolling and cold rolling, and to perform intermediate annealing after hot rolling or during cold rolling. It is a target.
[0003]
Also, when manufacturing a tab using the aluminum alloy plate obtained as described above, in order to improve corrosion resistance and aesthetics, apply a coating base treatment, paint and bake a clear paint on the surface, and press work In general, a tab is manufactured by punching into a tab shape, and also punching an inner finger-hung portion, and further bending the inner edge and the outer edge of the finger-hook portion by 180 degrees to impart further strength. The tab thus obtained is usually combined with a rivet portion of a separately manufactured can lid and integrated with the can lid.
[0004]
The can lid can be opened by pulling up the tab when the can is opened and applying force to the opening of the can lid by the principle of leverage, or by simply pulling the tab and pulling the can. There is a pull tab type that tears an opening of a lid.
[0005]
[Problems to be solved by the invention]
As described above, when manufacturing a tab of an aluminum can, it is usual to perform a severe bending process of bending at 180 degrees. Therefore, the tab material is required to have particularly excellent bending workability among various moldability.
[0006]
Also, as described above, the tab is formed after baking as described above, but if it softens at the time of heating for baking and the strength is too low, it can meet the required strength as a tab. It can be difficult. Therefore, it is desired that the tab material not only has high strength but also has good heat-softening characteristics.
[0007]
In addition, when the can is opened, in the case of the stay-on tab type, bending stress acts on the entire tab when pulling up the tab for opening, and especially the rivet joint portion of the tab is sharply raised when pulling up the tab. The tab is usually bent back in the opposite direction when the tab is returned, and when the can is not completely opened by one pulling / returning, the tab is pulled up / returned several times. It will be repeated and will be subjected to repeated bending. On the other hand, even in the case of the pull tab method, although the open method is different, a bending stress acts on the tab when the can is opened, and the bending stress is often applied repeatedly.
[0008]
Then, if the tab is broken by bending or repeated bending applied to the tab at the time of opening the can, the function as the tab cannot be achieved. Therefore, it is required that the tab does not break when the can is opened.
[0009]
As described above, the tab material is required to be particularly excellent in bending workability among various moldability, and also has good heat-softening property at the time of baking paint, and further bends at the time of opening the can, repeated bending. It is desired that the tab does not break.
[0010]
Here, as described above, when forming the tab, a severe bending process of bending at 180 degrees is performed, but if a crack occurs at this bending process or a starting point of the crack occurs, the opening of the can is caused by the influence. The tab is sometimes broken due to bending given to the tab and repeated bending, and the tab cannot function as described above. Therefore, it is strongly desired that the tab material has particularly excellent bending workability.
[0011]
By the way, regarding the tab material, in recent years, it has been desired to reduce the thickness, mainly for the purpose of cost reduction. Therefore, there is a growing tendency to increase the strength and reduce the thickness of the tab material, especially in Europe and the United States. . However, when simply increasing the strength of an aluminum alloy plate, bending workability is usually reduced. Even with a conventional tab material, it is difficult to increase the thinness and strength without impairing the bending workability. It was difficult.
[0012]
Further, as a method for manufacturing an aluminum alloy sheet, recently, a process in which annealing (intermediate annealing) after hot rolling or in the middle of cold rolling is omitted is applied, and the productivity is improved by reducing the number of steps. At the same time, energy saving has been considered to contribute to reduction of energy costs and prevention of global warming. This is a process that generally eliminates the need for intermediate annealing in the subsequent steps up to the final sheet thickness by recrystallization in the state after hot rolling, but such a method is used for conventional aluminum alloy sheets for tabs. The fact is that a process has not been established, and a method for obtaining an aluminum alloy plate for a tab excellent in performance as described above as a tab material has not been established.
[0013]
The present invention has been made in view of the above circumstances, and has excellent bending workability, and there is no possibility that the tab will be broken at the time of opening the can due to cracks or the like at the time of bending, and it is sufficient as a tab material. It provides an aluminum alloy plate for tab materials with high strength and paint baking resistance, and at the same time, is excellent as a tab material as described above in a process that eliminates annealing from the start of hot rolling to the end of cold rolling. It is an object of the present invention to provide a method capable of obtaining an aluminum alloy plate having high performance.
[0014]
[Means for Solving the Problems]
In order to solve the above-described problems, as a result of repeated experiments and studies by the present inventor, as well as appropriately adjusting the component composition of the aluminum alloy for the tab material, the amount of solute Mn in the product plate, It has been found that the above-mentioned problems can be solved at once by appropriately regulating the dispersion state of the intermetallic compound. Further, as a manufacturing method, hot rolling conditions are strictly controlled by dividing into rough rolling conditions and finish rolling conditions, thereby eliminating intermediate annealing after hot rolling or in the middle of cold rolling to reduce manufacturing costs and the like. The inventors have found out that an aluminum alloy plate for a tab material that solves the above-mentioned problems can be manufactured.
[0015]
Therefore, the aluminum alloy plate for a coating tab according to the first aspect of the present invention has a composition of Mg 3.5 to 5.5%, Mn 0.01 to 0.55%, Si 0.02 to 0.40%, and Cr 0.01 to 0.20%. And the Fe content is regulated to 0.40% or less, the Cu content is regulated to 0.30% or less, the Ti content is regulated to 0.30% or less, and the balance consists of Al and unavoidable impurities, and the amount of solute Mn Is in the range of 0.005 to 0.25%, and the number of intermetallic compounds having a maximum diameter of 5 μm or more is 1 mm. ² The number is within the range of 50 to 600 pieces.
[0016]
The method for producing an aluminum alloy sheet for a coating tab according to the second aspect of the present invention is as follows: Mg: 3.5 to 5.5%, Mn: 0.01 to 0.55%, Si: 0.02 to 0.40%, Cr: 0.01 to 0%. Aluminum alloy cast containing .20%, Fe content of 0.40% or less, Cu content of 0.30% or less, Ti content of 0.30% or less, the balance being Al and unavoidable impurities After the ingot is heated at a temperature in the range of 470 to 530 ° C. for 15 hours or less, and when hot rolling including rough rolling and finish rolling is performed, the finish temperature of the rough rolling is set in the range of 370 to 485 ° C. in finish rolling. Hot rolling is performed so that the recrystallization rate after hot rolling is 85% or more, and then cold rolling is performed at a rolling rate of 80 to 92%. , The amount of solid solution Mn is 0.005 to .25% range in a and maximum diameter 5μm or more intermetallic number of compounds are 1mm ² The present invention is characterized in that an aluminum alloy plate for a coating tab is obtained in a range of 50 to 600 pieces per coating tab.
[0017]
Further, the method for producing an aluminum alloy plate for a coating tab according to the third aspect of the present invention is the method for producing an aluminum alloy plate for a can lid coating tab according to the second aspect, further comprising: It is characterized in that temper annealing is performed at a temperature within the range for 1 to 10 hours.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
First, the reasons for limiting the composition of the alloy used in the aluminum alloy plate for a coating tab of the present invention will be described.
[0019]
Mg:
Mg is an element indispensable for obtaining the strength required for the tab material targeted in the present invention. That is, the addition of Mg contributes to the improvement in strength due to solid solution of Mg itself, and also contributes to the improvement in strength due to work hardening because Mg has a large interaction with dislocations. However, if the added amount of Mg is less than 3.5%, it is difficult to obtain sufficient strength as a tab material. On the other hand, if the added amount of Mg exceeds 5.5%, the dislocation density introduced by cold rolling becomes too large, and cracks may occur during forming. Therefore, the added amount of Mg is set in the range of 3.5 to 5.5%.
[0020]
Mn:
The addition of Mn has a great effect on improving strength and suppressing softening during baking. If the added amount of Mn is less than 0.01%, the amount of solute Mn in the product plate is too small, and it is difficult to satisfy the required strength. On the other hand, if the added amount of Mn exceeds 0.55%, the amount of Al-Mn- (Si) -based and Al-Fe-Mn- (Si) -based intermetallic compounds increases, and the intermetallic compounds are remarkably increased. It becomes coarse and exceeds the condition range of the intermetallic compound specified in the present invention, and as a result, bending workability is remarkably reduced. Therefore, the amount of Mn added is set in the range of 0.01 to 0.55%.
[0021]
Si:
The addition of Si has a great effect on suppressing softening during baking of paint. However, if the added amount of Si is less than 0.02%, the effect cannot be sufficiently obtained. On the other hand, if the added amount of Si exceeds 0.40%, Al—Mn—Si system, Al—Fe—Mn—Si system, and Mg ₂ As the intermetallic compound of Si is generated, the coarsening becomes remarkable, exceeding the condition range of the intermetallic compound specified in the present invention, and as a result, the bending workability is lowered. Therefore, the added amount of Si is set in the range of 0.02 to 0.40%.
[0022]
Cr:
The addition of Cr has a great effect on improving strength and suppressing softening during baking. However, if the Cr content is less than 0.01%, the effect is not exhibited. On the other hand, if the Cr content exceeds 0.20%, an Al-Cr based intermetallic compound is generated and coarsened, resulting in exceeding the condition range of the intermetallic compound specified in the present invention. As a result, bending workability is impaired, and cold rolling property is impaired. Therefore, the amount of Cr added was set in the range of 0.01 to 0.20%.
[0023]
Fe:
The addition of Fe has a great effect on suppressing softening during baking of paint. However, if the amount of Fe exceeds 0.40%, an Al-Fe-Mn- (Si) -based intermetallic compound is generated, and the intermetallic compound becomes coarse. Exceeding the range results in reduced bending workability. Therefore, the amount of Fe in the alloy is restricted to 0.40% or less.
[0024]
Cu:
Addition of Cu also has a great effect on improving strength and suppressing softening during baking of paint, but if the Cu content exceeds 0.30%, cracks may occur during molding. Therefore, the amount of Cu added is limited to 0.30% or less.
[0025]
Ti:
Although Ti is an element effective for refining crystal grains, if the amount of Ti added is large, the ingot structure is unlikely to become feather-like crystals, and granular crystals are easily generated. When the granular crystals are generated in this way, the intermetallic compound crystallized at the grain boundary is more likely to be coarser than in the case of the feathery crystal, and the coarse intermetallic compound is generated by itself. Therefore, the amount of Ti is restricted to 0.30% or less. In some cases, B may be added to Ti, and in this case, the amount of B is preferably regulated to 300 ppm or less.
[0026]
Other than the above components, Al and unavoidable impurities may be basically used.
[0027]
Further, in the aluminum alloy plate for a coating tab of the present invention, not only the component composition of the alloy is adjusted as described above, but also the Mn solid solution amount in the product plate is adjusted within the range of 0.005 to 0.25%. This is very important.
[0028]
That is, in the conventional manufacturing process of the aluminum alloy sheet for tabs, as described above, usually after the hot rolling or during the cold rolling, annealing (intermediate annealing) is mainly performed for the purpose of recrystallization. In the case of the present invention, annealing is not performed until the final sheet thickness at the end of cold rolling after hot rolling in order to reduce manufacturing costs and the like. In such a process in which annealing is not performed until the final sheet thickness after hot rolling, the final sheet necessarily has a small amount of solute Mn. In particular, when the amount of solute Mn is very small, less than 0.005%, the effect of suppressing softening during baking of the coating becomes extremely small, and it becomes difficult to satisfy the required strength as a tab. If the required strength is not satisfied, the tab may be bent when the lid is opened. On the other hand, the upper limit of the Mn solid solution amount is affected by the heat treatment conditions also serving as the homogenization treatment, the structure of the hot-rolled sheet, and the alloy components, but generally, the solid solution Mn amount exceeding 0.25%. In order to obtain Mn, Mn must be added in a large amount beyond the range specified in the present invention. However, if the amount of added Mn is excessive, the amount of Al-Mn- (Si) -based and Al-Fe-Mn- (Si) -based intermetallic compounds increases, and the intermetallic compounds become coarse. As a result, the condition range of the intermetallic compound defined in the present invention is exceeded, and as a result, bending workability is reduced. Therefore, the upper limit of the Mn solid solution amount of the product plate is set to 0.25%. In the present invention, the amount of solid solution Mn is measured by a hot phenol filtrate analysis method.
[0029]
Further, in the aluminum alloy plate for a coating tab of the present invention, the distribution number of intermetallic compounds having a maximum diameter of 5 μm or more present in the product plate is 1 mm. ² It is extremely important to regulate within the range of 50 to 600 pieces. That is, the number of intermetallic compounds having a maximum diameter of 5 μm or more is 1 mm ² If the number is less than 50 pieces, a decrease in bending workability caused by the intermetallic compound can be suppressed, but a high-purity metal has to be used, resulting in a significant increase in cost. On the other hand, the number of intermetallic compounds having a maximum diameter of 5 μm or more is 1 mm ² If the number exceeds 600, the bending property due to the intermetallic compound is significantly reduced. Therefore, in order to ensure excellent bending workability without increasing the cost, the number of intermetallic compounds having a maximum diameter of 5 μm or more is set to 1 mm ² It is necessary to regulate within the range of 50 to 600 pieces. Here, since a fine intermetallic compound having a maximum diameter of less than 5 μm does not significantly affect bending workability, in the present invention, only an intermetallic compound having a maximum diameter of 5 μm or more is restricted. In the present invention, the number of intermetallic compounds was measured by observing the structure on the surface of the rolled sheet and performing image analysis using a Luzex image analysis processor.
[0030]
As described above, by appropriately regulating not only the composition of the alloy but also the amount of Mn solid solution in the product plate and the number of intermetallic compounds having a maximum diameter of 5 μm or more, the final rolling after hot rolling is performed as described below. Even if a process omitting annealing up to the plate thickness is applied, an aluminum alloy plate for a coating tab having excellent bending workability, sufficient strength as a tab material, and good coating baking resistance can be obtained.
[0031]
Next, the manufacturing method according to the present invention, that is, the method according to the second and third aspects of the present invention will be described.
[0032]
First, an aluminum alloy having the above-described composition is cast according to a conventional method such as a DC casting method. Prior to hot rolling, the ingot is heated at a temperature in the range of 470 to 530 ° C. for 15 hours or less. The ingot heating before the hot rolling is preferably performed also as a homogenization treatment for the ingot. If the temperature of the ingot heat treatment is lower than 470 ° C., edge cracks and the like of the sheet will be caused during hot rolling, leading to a reduction in yield and a reduction in productivity. On the other hand, if the temperature of the ingot heating exceeds 530 ° C., the intermetallic compound tends to be coarsened, possibly exceeding the condition range of the intermetallic compound in the final sheet. Also, when the holding time of the ingot heating exceeds 15 hours, the intermetallic compound is likely to be coarsened and may exceed the condition range of the intermetallic compound in the final sheet. Therefore, the condition of the heat treatment of the ingot before hot rolling is defined as holding at a temperature within the range of 470 to 530 ° C. for 15 hours or less. Here, the temperature of the ingot heating is the set temperature of the heating furnace. Here, the lower limit of the heating time is not limited, and it is essential that the heating time is such that the inside of the ingot is uniformly heated. However, it is usually appropriate that the heating time is 1 hour or more.
[0033]
The hot ingot is immediately subjected to hot rolling as described above. Generally, hot rolling is often performed by a combination of rough rolling and finish rolling. Also in the case of the method of the present invention, hot rough rolling and hot finish rolling are performed to obtain a hot rolled sheet. In the method of the present invention, the end temperature of the hot rough rolling is set in the range of 370 to 485 ° C., the end temperature of the hot finish rolling is set in the range of 280 to 350 ° C. It is necessary to perform hot rolling so that the recrystallization rate of the sheet becomes 85% or more in a state of being rolled and wound into a coil. The reasons for defining these conditions are as follows.
[0034]
That is, when the end temperature of the hot rough rolling is lower than 370 ° C., the end temperature of the subsequent hot finish rolling is lower than 280 ° C., and as a result, the recrystallization rate after hot rolling is 85% or more. It may be difficult to secure them. If the end temperature of the hot rough rolling is lower than 370 ° C., edge cracking of the sheet may be caused during the subsequent hot finish rolling. On the other hand, if the end temperature of the hot rough rolling exceeds 485 ° C, the subsequent hot finish rolling end temperature may exceed 350 ° C. It may occur and impair the value as a product. Therefore, the end temperature of the hot rough rolling was in the range of 370 to 485 ° C.
[0035]
Next, if the end temperature of the hot finish rolling is lower than 280 ° C., it becomes impossible to secure a recrystallization rate of 85% or more of the hot rolled sheet after the finish rolling. If the recrystallization rate of 85% or more cannot be secured in this way, Mn will precipitate in a region having a high dislocation density as described later, and the amount of solid solution Mn specified in claim 1 may not be secured, In this case, the effect of suppressing softening during baking of the paint becomes extremely small, and it becomes difficult to satisfy the required strength as a tab. Further, when the finish temperature of the hot finish rolling is lower than 280 ° C. and the recrystallization rate of the hot rolled sheet cannot be maintained at 85% or more, the sheet is broken during the cold rolling, and the productivity and the yield are reduced. Is reduced. On the other hand, if the hot finish rolling temperature exceeds 350 ° C., a recrystallization rate of 85% or more can be easily secured, but hot rolling coating occurs and quality deterioration cannot be avoided. Therefore, the hot finish rolling end temperature is set in the range of 280 to 350 ° C.
[0036]
The hot-rolled sheet obtained by the above-described hot rough rolling and hot finishing rolling needs to have a recrystallization rate of 85% or more in a hot-rolled state. Here, if a recrystallization rate of 85% or more cannot be ensured after hot rolling, Mn may precipitate in a region having a high dislocation density, and the amount of solid solution Mn specified in claim 1 may not be secured. However, in this case, the effect of suppressing softening during baking of the coating becomes extremely small, and it becomes difficult to satisfy the required strength as a tab. If the required strength of the tab is not satisfied, the tab is bent when the lid is opened. Further, when the recrystallization rate of the sheet is less than 85% in the hot-rolled state, the cold-rolling property is deteriorated, and the subsequent cold-rolling causes the sheet to be cut, thereby lowering the productivity and the yield. There is a possibility that it will. Therefore, the recrystallization rate of the hot-rolled sheet after hot rolling needs to be 85% or more.
[0037]
The hot-rolled sheet having a recrystallization rate of 85% or more obtained as described above is finished to a final sheet thickness (product sheet thickness) by cold rolling without annealing to the final sheet thickness. That is, the product is finished to a product thickness by cold rolling without performing intermediate annealing after hot rolling or in the middle of cold rolling.
[0038]
In this cold rolling, the rolling reduction needs to be in the range of 80 to 92%. That is, if the cold rolling reduction is less than 80%, the strength required for the tab cannot be obtained. On the other hand, at a high cold rolling reduction exceeding 92%, the dislocation density introduced by the cold rolling becomes too large, the bending workability is reduced, and the tab breaks during bending. Therefore, the cold rolling reduction needs to be in the range of 80 to 92%.
[0039]
The plate having the final thickness obtained by the cold rolling as described above may be used as a product plate as it is, and may be used as a tab, but in some cases, after the cold rolling, in a temperature range of 100 to 240 ° C. Temper annealing with holding for 1 to 10 hours may be performed. The conditions for such tempering annealing will be described below.
[0040]
If the temperature of the temper annealing is less than 100 ° C., the effect of the temper annealing cannot be sufficiently obtained, while if it exceeds 240 ° C., the material is softened and it becomes difficult to satisfy the required strength of the tab. Further, if the holding time of the temper annealing is less than 1 hour, uniform heat treatment cannot be performed over the entire coil. If the holding time exceeds 10 hours, not only does the productivity decrease, but also softening causes insufficient strength. Therefore, the condition of the temper annealing was 100 to 240 ° C. for 1 to 10 hours.
[0041]
The product plate obtained by the above-described production method must have the Mn solid solution amount and the intermetallic compound dispersion number each satisfying the above-described conditions. The specific process conditions for satisfying each of these conditions cannot be uniquely defined because they vary depending on the specific alloy components and combinations with other process conditions. Specific process conditions according to the specific alloy components within ranges that satisfy the lump heat treatment conditions, hot rolling conditions (rough rolling conditions, finish rolling conditions, recrystallization rate conditions), and cold rolling conditions What is necessary is just to combine appropriately.
[0042]
【Example】
Table 1 shows the alloy Nos. 1 to No. 6 were cast by a DC casting method, and the obtained ingot was subjected to ingot heating-hot rolling (roughing) under various process conditions indicated by production process codes A to H in Table 2. (Rolling and finishing rolling)-Cold rolling was performed, and for some of them, temper annealing was performed after cold rolling to obtain a product sheet (aluminum alloy sheet for tabs) having a final sheet thickness of 0.35 mm. Each product plate was finish-painted and baked at 240 ° C. × 24 s.
[0043]
For each product plate, the amount of solid solution Mn was measured, and 1 mm of intermetallic compound having a maximum diameter of 5 μm or more was measured. ² The number per hit was checked. Further, the yield strength YS was examined as the material strength after the paint baking treatment. Further, the performance as a tab to which bending and repeated bending were applied was evaluated as follows. That is, each product plate was processed into a tab, 500 pieces each were produced, attached to a can lid of a stay-on tub type, and an opening test was conducted in which the tab was actually pulled up and opened. The opening test was performed by putting a carbonated beverage in a can body, sealing the can with a lid for a carbonated beverage, and attaching a tab to the lid. Table 3 shows the measurement results and the evaluation results.
[0044]
In Table 3, in the tab evaluation, the can openability test was carried out as described above, and the case where at least one tab was bent at the time of opening due to cracking or defective shape of the tab was marked as unacceptable, and 500 tabs were given. In all cases, the case where the opening was possible without bending of the tab was evaluated as acceptable, and a mark was given. In addition, regarding the material strength (YS) after baking the paint, in general, an opening failure is likely to occur when the strength is lower than 275 Pa. In this case as well, when the YS is lower than 275 Pa, it can be judged as reject. As for the overall evaluation, the case where the tab performance was acceptable and the YS was 275 Pa or more was evaluated as passing (o), and the other cases were evaluated as unacceptable (x).
[0045]
[Table 1]

[0046]
[Table 2]

[0047]
[Table 3]

[0048]
In Table 3, examples of the symbols A and D all have the component composition of the alloy within the range specified in the present invention, the manufacturing process also satisfies the conditions specified in the present invention, the Mn solid solution condition, the intermetallic The number-of-compounds condition also satisfies the range specified in the present invention. In this case, the tab does not bend, the tab performance is good, the strength is sufficient, and the tab material is excellent overall. Was confirmed.
[0049]
On the other hand, in the example of the code B, the component composition of the alloy is within the range specified in the present invention, but the ingot heating time in the manufacturing process is too long, and the number of intermetallic compounds having a maximum diameter of 5 μm or more becomes excessive. As a result, the tab performance was deteriorated, and the tab was bent.
[0050]
Further, in the example of the symbol C, the composition of the alloy is within the range specified in the present invention, but the cold rolling reduction in the manufacturing process is too high, and the tab performance is also poor in this case.
[0051]
Although the production code E also has an alloy composition within the range specified in the present invention, the production process is an example in which the rough rolling end temperature and the finish rolling end temperature of hot rolling are too low. Of the solid solution of Mn was small, the strength was insufficient, and the tab performance was inferior.
[0052]
Further, the production codes F, G, and H are all examples in which the component composition of the alloy is out of the range specified in the present invention. In these cases, the manufacturing process conditions satisfy the conditions specified in the present invention, but the strength or the strength is not satisfied. And / or tab performance was inferior. Among these, the symbol F is an example in which the added amounts of Mn, Cr, and Ti are excessive, and the solid solution Mn amount of the product plate and the number of intermetallic compounds having a maximum diameter of 5 μm or more are both excessive, and the tab performance is poor. Oops. Symbol G is an example in which the added amounts of Si, Cu, and Fe were excessive. In this case, the number of intermetallic compounds having a maximum diameter of 5 μm or more became excessive, and the tab performance deteriorated. The symbol H is an example in which the amount of Mg was too small, and in this case, the strength was insufficient.
[0053]
【The invention's effect】
As is apparent from the above-described embodiment, according to the invention of claim 1, even if the production is performed by a process in which the annealing between the hot rolling and the end of the cold rolling is omitted, the bending workability is good and the coating is performed. When used as a tab, there is no possibility that the tab will be bent, and there is little softening due to baking of the coating, and an aluminum alloy plate for a coating tab having sufficient strength as a tab can be obtained. Therefore, it is particularly effective as a thinned tab material. Further, according to the manufacturing method of the invention of claims 2 and 3, annealing of the aluminum alloy sheet for a coating tab having the above-mentioned excellent performance from the hot rolling to the end of the cold rolling is omitted. In the process, it is possible to manufacture reliably and stably, and since the annealing is not performed between the end of the hot rolling and the end of the cold rolling, the manufacturing cost can be reduced by reducing the number of steps. It is possible to contribute to energy cost reduction and global warming prevention by reducing energy consumption.

Claims

It contains Mg 3.5 to 5.5% (mass%, the same applies hereinafter), Mn 0.01 to 0.55%, Si 0.02 to 0.40%, Cr 0.01 to 0.20%, and the Fe content is The content is restricted to 0.40% or less, the Cu content to 0.30% or less, the Ti content to 0.30% or less, the balance being Al and unavoidable impurities, and the solid solution Mn content is 0.005 to 0.25. %, And the number of intermetallic compounds having a maximum diameter of 5 μm or more is within a range of 50 to 600 per 1 mm ² .

Cu containing 3.5 to 5.5% of Mg, 0.01 to 0.55% of Mn, 0.02 to 0.40% of Si, 0.01 to 0.20% of Cr, and having an Fe content of 0.40% or less; The aluminum alloy ingot in which the amount is controlled to 0.30% or less and the Ti amount is controlled to 0.30% or less and the balance is made up of Al and inevitable impurities was heated at a temperature in the range of 470 to 530 ° C. for 15 hours or less. Thereafter, in performing hot rolling comprising rough rolling and finish rolling, the finish temperature of rough rolling is set in a range of 370 to 485 ° C., and the finish temperature of finish rolling is set in a range of 280 to 350 ° C. Hot rolling is performed so that the recrystallization rate becomes 85% or more, and then cold rolling is performed at a rolling rate of 80 to 92%, so that the amount of solute Mn is in the range of 0.005 to 0.25%. And the number of intermetallic compounds having a maximum diameter of 5 μm or more is 1 characterized in that to obtain a paint tab for the aluminum alloy plate in m ² per 50 to 600 pieces in the range, method for manufacturing a coated tab for the aluminum alloy plate.

The method for producing an aluminum alloy plate for a coating tab according to claim 2,
A method for producing an aluminum alloy sheet for a coating tab, further comprising performing temper annealing at a temperature within a range of 100 to 240 ° C. for 1 to 10 hours after the cold rolling.