JP3600022B2

JP3600022B2 - Manufacturing method of aluminum base alloy sheet for deep drawing

Info

Publication number: JP3600022B2
Application number: JP19786798A
Authority: JP
Inventors: 紘一大堀; 洋斉藤; 充斉藤; 俊宏原田
Original assignee: Mitsubishi Aluminum Co Ltd
Current assignee: Mitsubishi Aluminum Co Ltd
Priority date: 1998-07-13
Filing date: 1998-07-13
Publication date: 2004-12-08
Anticipated expiration: 2018-07-13
Also published as: JP2000026946A

Description

【０００１】
【発明の属する技術分野】
本発明は、高強度および高延展性を有し、アルミニウム基合金製の缶などの深絞り成形に際して耳率を著しく低減できる深絞り成形用アルミニウム基合金板の製造方法に関する。
【０００２】
【従来の技術】
缶入り飲料などの需要増大に伴い、最近ではその容器として好適なアルミニウム基合金製のいわゆるＤＩ（Ｄｅｅｐｄｒａｗｉｎｇ＆Ｉｒｏｎｉｎｇ）缶が大量に生産されるようになっている。このアルミニウム基合金製ＤＩ缶の本体の一般的な製造方法としては、アルミニウム基合金板を多段に深絞り加工し、さらにしごき加工を行って缶本体を成形し、焼付け塗装後に、耐圧強度の向上や比較的高価な蓋部材の材料の使用量を削減するために縮径するネック加工を行う。ここで使用するアルミニウム基合金板には、製缶後の十分な強度と、多段深絞りやしごきに耐える成形性とが共に要求される。
【０００３】
一般に、深絞り用アルミニウム基合金としては、Ａｌ−Ｍｎ−Ｍｇ系の、例えば米国アルミニウム協会標準（Ａ．Ａ）３００４合金などが広く用いられている。この合金から深絞り用アルミニウム基合金板を製造するには、（ａ）先ずこの合金の鋳塊を熱間圧延し、次に（ｂ）冷間圧延して適度な板厚の板材とし、この冷間圧延後の板材に（ｃ）中間焼鈍を施し、さらに要求される強度に応じて（ｄ）冷間圧延による硬化処理が行われる。
【０００４】
この深絞り成形用アルミニウム基合金板の製造工程において、板材の強度を向上させるためには前記（ｄ）の冷間圧延における冷間圧延率を高くする必要がある。しかし冷間圧延度を上げると、いわゆる圧延集合組織が発達し、塑性変形に際して異方性が顕著に現れるようになり、深絞り成形したときの板材の圧延方向に応じて成形した缶本体の上縁の高さが山谷状に変化する現象が起こる。
この山谷状に変形した部分は通常、「耳」と呼ばれている。深絞り成形後の缶体は、次いでしごき加工を行った後に、蓋部材を取付けるために開口部を水平に切断し缶高を揃えるトリム加工が行われる。このトリム加工の際には耳も除去されるので、耳の高さが高いと、除去すべき板材の量割合（以下「耳率」という）が増大し、歩留まりが低下して製造コストが上昇するという問題があった。そこで、低耳率となる板材が求められていた。
【０００５】
一般にアルミニウム基合金板を冷間圧延すると、圧延方向に対して４５〜６０゜の方向に耳の山となる圧延集合組織が発達する傾向がある。そこで、耳率を低下させるためには圧延集合組織の発達を抑制する必要がある。これは冷間圧延前の板材における再結晶集合組織の生成状態を制御することによって達成できることがわかっている。すなわち、一般には、冷間圧延以前に、０−９０゜の方向に深絞り耳を生じるような、「立方体方位」と呼ばれる再結晶集合組織を発達させる方法が用いられる。
立方体方位が発達すると０−９０゜方向の耳を生じることになるが、その後の冷間圧延によってこの方向の耳はあまり発達せず、一方、４５゜耳を生成する圧延集合組織の発達も抑制され、結果として開口部周縁における耳の山が均一化されることになる。この方法によって、圧延度８０％以上の冷間圧延の後に僅かな０−９０゜耳と４５゜耳とが混在する低耳性板材が得られるようになった。
【０００６】
前記の立方体方位の再結晶集合組織を発達させる具体的な方法としては、熱間圧延時の諸条件を調節し、熱間圧延後に巻き取ったコイルが冷却するまでの間、あるいは巻き取ったコイルを焼鈍する際に生じる再結晶を制御する方法（特開平５−１２５５００号公報）が知られている。
この方法では、前記（ｂ）冷間圧延、または（ｂ）冷間圧延と（ｃ）中間焼鈍とを行わず、再結晶した熱間圧延板に前記（ｄ）冷間圧延を施す。現在、ＤＩ缶用として主に用いられている板材の厚さは約０．３ｍｍ程度であるので、この方法を適用して最終の冷間圧延率を８０〜９０％とする場合には、熱間圧延により板厚が１．５〜３ｍｍとなるように圧延する必要がある。
そこで、普通、リバース式熱間圧延機を用いて圧延した後にさらにタンデム式の仕上用熱間圧延機または圧延機の両側にコイル巻取り装置を装備したリバース式熱間仕上圧延機を用いて圧延する方法が用いられる。しかしこれらの熱間仕上圧延機は大規模でかつ高価であり、これを用いることによる製造コスト上の負担が大きい。
更に、缶用素材の薄肉化に伴い、圧延ロールやパス間での温度低下の影響が大きくなり、適切な熱間圧延条件を維持するためには設備能力を更に増大させる必要があって一層コストが嵩む傾向にあった。
【０００７】
そこで、熱間圧延の全工程にシングルミルのリバース式熱間粗圧延機のみを用いる方法が検討された。しかしこの粗圧延機を用いて薄肉の板材を製造しようとすると、パス間での温度低下が著しく、熱間圧延板の再結晶を制御するための熱間圧延条件を維持することがきわめて困難になる。この問題を解決する手段として、アルミニウム基合金に時効硬化性を与える元素を添加し、前記（ｂ）の冷間圧延後、前記（ｃ）の中間焼鈍を比較的高温で行うことにより溶体化し、前記（ｄ）の冷間圧延の圧延度を小さくしても十分な強度が得られる方法が提案された（特公昭６０−３５２４２号公報）。
【０００８】
この方法によれば、ＤＩ缶本体を成形した後の焼付け塗装の加熱により結晶が析出するので、焼付け時の加熱による軟化が抑制され、冷間圧延率を小さくしても十分な強度が得られるようになった。従って、前記（ｃ）中間焼鈍の後に立方体集合組織が十分発達していなくても冷間圧延の圧延率を小さくできるので圧延集合組織の発達も軽度となり、耳率が比較的低い実用レベルのＤＩ缶が得られるようになった。この方法は、仕上用熱間圧延機を用いた場合より耳率が若干高く、従ってトリム量も多くなるのではあるが、設備費が高価な仕上用の熱間圧延機を用いずに適用できるので、結果的に有利な方法となっている。
【０００９】
しかし、最近、経済的およびデザイン的な要求からＤＩ缶における蓋部材の直径を小さくする要求が高まり、このためネックの縮径率が増大するようになってきた。ところがネックの縮径率を増大させると、このネック成形工程においても深絞り成形の場合と同様に素材の異方性により開口部において缶高が変化し耳が発生するという新たな問題が生じた。このネック成形によって生じる開口部の高さ変動部を「ネック耳」と称する。
缶本体の開口部は、ネック成形を行った後にフランジ成形され、このフランジが蓋部材との巻き締めに使われるのであるが、ネック耳が大きいとフランジ幅が方向により異なったり、ネック部の形状が方向により変化するなどの問題が起こり、加工工程が煩雑になると共に外観上にも悪影響が現れる。そこで、ネックの縮径率を大きくしてもネック耳が生じにくい深絞り成形用アルミニウム基合金板が求められていた。
【００１０】
缶本体の開口部は、ネック成形を行った後にフランジ成形され、このフランジが蓋部材との巻き締めに使われるのであるが、ネック耳が大きいとフランジ幅が方向により異なったり、ネック部の形状が方向により変化するなどの問題が起こり、加工工程が煩雑になると共に外観上にも悪影響が現れる。そこで、ネックの縮径率を大きくしてもネック耳が生じにくい深絞り成形用アルミニウム基合金板が求められた。
【００１１】
このような背景から本発明者らは、特願平９−１４２７９１号においてシングルミルの粗圧延・仕上圧延兼用のリバース式熱間圧延機を用い、深絞り成形時やネック成形時にネック耳が生じにくい深絞り成形用アルミニウム合金板の製造方法について特許出願している。
この特許出願に係る技術によれば、均熱工程と熱間圧延工程と第一冷間圧延工程と第一中間焼鈍工程と第二冷間圧延工程と第二中間焼鈍工程と第三中間焼鈍工程と最終冷間圧延工程とを順次施してアルミニウム基合金板を製造する際に、特に、
熱間圧延終了温度を２８０〜３５０℃の範囲内とし、引き続き６０〜９０％の第一冷間圧延を施し、２５０〜２８０℃の温度範囲において２〜２４時間の第一中間焼鈍を施すことが要件とされていた。
【００１２】
【発明が解決しようとする課題】
前記熱間終了温度を２８０〜３５０℃とするのは、熱間圧延後再結晶しないようにするためであるが、この温度範囲を外れた場合、引き続き行われる第一冷間圧延での加工硬化が大きく、６０％以上の高い圧延率の冷間圧延を行う過程で、アルミニウム基合金板の両サイドにクラックが発生しやすく、クラックを除去するために両サイドをトリムする必要があり、歩留まりが低下する問題があった。そこで本発明者らは、前述の製造条件の見直しを行うことで熱間終了温度を２８０〜３５０℃の範囲より広くしてもクラックを生じない製造条件を見い出し、本発明に到達した。
【００１３】
また、前述の第一中間焼鈍は、第一冷間圧延加工して加工硬化したコイルを半軟化の状態まで焼鈍するための工程であるが、どの程度まで軟化させるかにより耳率が変化するため、耳率のばらつきを小さくするためには、加熱温度や時間を厳格に管理する必要があるので、この加熱温度や時間の管理を緩和できるような製造条件について研究したところ本発明に到達した。
更に、第一中間焼鈍は通常バッチ式と称される焼鈍炉で行ない、ここではアルミニウム基合金板をコイル状に巻き付けてコイルの状態で炉内に搬入して焼鈍を行うが、バッチ式焼鈍炉では、このコイルの幅や条件によって加熱速度が異なるために、即ち、コイル重量が異なると温度を一定に管理できないために、同一の加熱温度と時間にするためにはコイルの寸法に応じて炉の操業条件を変更する必要があり、コイルの寸法管理が繁雑な問題があった。即ち、多数のコイルを同時に同一炉に搬入して処理する場合に、大きさの異なるコイル毎に加熱、冷却条件が異なってしまう問題があるので、全てのコイルの寸法を同一にする必要があった。
このため、製造するコイルの寸法に応じて別々に焼鈍を行う必要があり、生産時期の調整のために中間製品の在庫量が増大してしまう問題があった。
【００１４】
本発明は上記の課題を解決するためになされたものであって、その目的は、素材強度の高いものを歩留まり低下を引き起こす事なく製造することができるとともに深絞り成形後の耳率を大幅に低減することができる深絞り成形用アルミニウム基合金板の製造方法を提供することにある。
更に、連続焼鈍炉を用いて第１中間焼鈍を行うことでアルミニウム基合金板に個々に所望の条件で焼鈍を行うことができ、熱間圧延工程の温度条件と第二冷間圧延工程の圧延率の条件を緩和することができるアルミニウム基合金板の製造方法を提供することを目的とする。
また、ネック成形時の縮径率を大きくしてもネック耳を生じにくいとともに、アルミニウム基合金の幅や大きさ、コイルとした場合のコイルの寸法に左右されずに生産時期を選択することができ、中間製品の在庫量を削減できるアルミニウム基合金板の製造方法の提供を目的とする。
【００１５】
【課題を解決するための手段】
上記の課題を解決するために本発明は、アルミニウム基合金の鋳塊からアルミニウム基合金板を製造するに際し、順次、(1)均熱工程において、前記アルミニウム基合金鋳塊を、５２０〜６１０℃の範囲内の均質化温度に加熱して均質化し、(2)熱間圧延工程において、前記の均質化されたアルミニウム基合金鋳塊を熱間圧延して板材を形成し、熱間圧延終了時の板材温度を、２８０〜４８０℃の温度範囲に調節し、前記熱間圧延の全工程にシングルミルのリバース式熱間粗圧延機を用いるとともに、(3)第一冷間圧延工程において、前記熱間圧延終了後の板材を、圧延率が６０〜９０％の範囲内となるように冷間圧延し、(4)第一中間焼鈍工程において、連続焼鈍装置を用いて１０〜２００℃／ｓの範囲の加熱速度で２８０〜３８０℃の温度範囲まで加熱し、この温度範囲で１〜３０秒間保持し、次いで１０〜２００℃／ｓの範囲の冷却速度で冷却して焼鈍し、(5)第二冷間圧延工程において、前記第一中間焼鈍後の板材を、圧延率が５〜４０％の範囲内となるように冷間圧延し、(6)第二中間焼鈍工程において、前記第二冷間圧延後の板材を、焼鈍温度が２７０〜４００℃の範囲内、焼鈍時間が２〜２４時間の範囲内で焼鈍し、(7)第三中間焼鈍工程において、連続焼鈍装置を用いて１０〜２００℃／ｓの範囲の加熱速度で４５０〜６００℃の温度範囲まで加熱し、この温度範囲で１〜３０秒間保持し、次いで１０〜２００℃／ｓの範囲の冷却速度で冷却して焼鈍し、次いで(8)最終冷間圧延工程において、前記第三中間焼鈍後の板材を、圧延率が４５〜９０％の範囲内となるように冷間圧延することを特徴とする。
【００１６】
前記のアルミニウム基合金は、Ｓｉ：０．１〜０．４重量％、Ｆｅ：０．３〜０．６重量％、Ｃｕ：０．０５〜０．４重量％、Ｍｎ：０．８〜１．５重量％およびＭｇ：０．８〜１．５重量％を含有し、残りがＡｌと不可避不純物からなる組成を有するものであることが好ましい。
このアルミニウム基合金は、さらに前記の元素に加えてＣｒ：０．２５重量％以下、Ｚｎ：０．０５〜０．２５重量％、Ｔｉ：０．２重量％以下のうち１種または２種以上を含有するものであることが好ましい。
【００１７】
前記(1)均熱工程において、均質化加熱速度を１００℃／時以下とし、かつ均質化時間を１時間以上としても良い。
前記(2)熱間圧延工程において、熱間圧延の全工程にシングルミルのリバース式熱間粗圧延機を用いることを要する。
前記(2)熱間圧延工程において、熱間圧延の開始温度を５００℃以上とし、かつ熱間圧延最終パスの開始温度を４００℃以上としても良い。
前記(2)熱間圧延工程において、熱間圧延最終パスの圧延率を５０％以上とすることができる。
【００１８】
前記▲５▼第二冷間圧延工程において、前記第一中間焼鈍後の板材を、圧延率が２０〜４０％の範囲内となるように冷間圧延することができる。
前記▲６▼第二中間焼鈍工程において、前記第二冷間圧延後の板材を、焼鈍温度が２７０〜３２０℃の範囲内、焼鈍時間が２〜２４時間の範囲内で焼鈍することが好ましい。
前記▲７▼第三中間焼鈍工程において、加熱速度および冷却速度を何れも１０〜２００℃／秒の範囲内とすることができる。
前記▲４▼第一中間焼鈍工程後の耐力を１００〜２５０ＭＰａの範囲とすることができる。
【００１９】
【発明の実施の形態】
以下、本発明の実施の形態を詳しく説明する。
本発明の深絞り成形用アルミニウム基合金板の製造方法は、基本的に、アルミニウム基合金の鋳塊を基材とし、それぞれ特定の条件に設定された次の各工程
▲１▼均熱工程、▲２▼熱間圧延工程、▲３▼第一冷間圧延工程、▲４▼第一中間焼鈍工程、▲５▼第二冷間圧延工程、▲６▼第二中間焼鈍工程、▲７▼第三中間焼鈍工程、および▲８▼最終冷間圧延工程を順次経由することにより構成される。
【００２０】
本発明に係る製造方法によれば、熱間圧延工程の全工程にシングルミルのリバース式熱間粗圧延機のみを用い、しかも強度と成形性とが両立した本発明アルミニウム基合金板が得られ、例えばＤＩ缶などの深絞り缶を製造する板材として用いるとき耳率が従来の板材に比べて低減し、ネック縮径率を大きくしたＤＩ缶を成形する際にもネック耳が減少し、缶体の変形を防止し歩留りを向上させることができる。
【００２１】
本発明に係る製造方法に用いるアルミニウム基合金としては、基本的にＡｌを基とし、Ｓｉを０．１〜０．４重量％、Ｆｅを０．３〜０．６重量％、Ｃｕを０．０５〜０．４重量％、Ｍｎを０．８〜１．５重量％およびＭｇを０．８〜１．５重量％含むものが用いられる。この基本的な組成自体は特殊なものではなく、現在大量に用いられている種々のアルミニウム缶用合金の組成の範囲内のものであるから、本発明の製造方法は、リサイクルされたアルミニウム缶を原料として経済的にかつ効率よく本発明のアルミニウム基合金板を製造するのに適している。
【００２２】
前記成分の内のＳｉは、同時に含有するＭｇと化合物を形成し易く、固溶硬化作用、分散硬化作用および析出硬化作用を有する他、Ａｌ、Ｍｎ、Ｆｅなどと化合物を形成し、しごき成形時のダイスに対する焼付きを防止する効果がある。その含有量は、０．１重量％未満では所望の潤滑特性を確保することができず、また０．４重量％を越えると加工性が劣化して不都合である。
Ｆｅは、結晶の微細化およびしごき成形時のダイスに対する焼付きを防止する効果がある。その含有量は、０．３重量％未満では所望の効果が得られず、０．６重量％を越えると加工性を劣化させる。
Ｃｕは、Ｍｇと化合物を形成し易く、固溶硬化、分散硬化および析出硬化に寄与する。その含有量は、０．０５重量％未満では所望の効果が得られず、０．４重量％を越えると加工性を劣化させる。
Ｍｎは、Ｆｅ、Ｓｉ、Ａｌなどと化合物を形成し易く、晶出相および分散相となって分散硬化作用を現すと共にしごき成形時のダイスに対する焼付きを防止する効果がある。その含有量は、０．８重量％未満では所望の硬化特性が得られず、１．５重量％を越えると加工性が劣化する。
またＭｇは、固溶体強化作用を有し、圧延による加工硬化性を高めると共に、前記Ｓｉや後記のＣｕと共存することによって分散硬化と析出硬化作用を現す。その含有量は、０．８重量％未満では所望の効果が得られず、１．５重量％を越えると再びその効果が低下するようになる。
【００２３】
本組成物は、前記のＳｉ、Ｆｅ、Ｃｕ、ＭｎおよびＭｇに加えて、さらに、Ｃｒを０．２５重量％以下、Ｚｎを０．０５〜０．２５重量％、Ｔｉを０．２重量％以下の範囲内で含んでいてもよい。
このうちＣｒは、熱間圧延後の再結晶を抑制する作用を有する。ただしその含有量が０．２５重量％を越えるとかえってこの作用が低下する。
ＺｎはＭｇ、Ｓｉ、Ｃｕの析出物を微細化する作用を有する。その含有量は、０．０５重量％未満では所望の効果が得られず、０．２５重量％を越えると耐食性を劣化させる。
Ｔｉは、結晶粒を微細化して加工性を改善する効果がある。ただしその含有量は０．２重量％を越えると粗大な化合物を生成しかえって加工性を劣化させる。
【００２４】
前記の本組成物から本発明のアルミニウム基合金板を製造するに際しては、先ず、常法に従って本組成物の溶湯から鋳塊を鋳造する。このときの凝固速度は通常、５〜２０℃／秒とされる。鋳塊の寸法は、例えば１．５ｍ×０．５ｍ×４〜５ｍである。
次に面削を行い、鋳塊の表面を１〜２５ｍｍ程度研削して、表面が平滑化された面削体を作成する。
【００２５】
この面削体は、次に本発明の▲１▼均熱工程に送られる。この▲１▼均熱工程は一般に、溶湯の凝固によって生じたミクロ偏析の均質化、過飽和固溶元素の析出、凝固によって形成された準安定相の平衡相への転移などのために行われる。
この▲１▼均熱工程においては、均質化温度を５２０〜６１０℃の範囲内とすることが重要である。均質化温度が５２０℃未満では、▲５▼第二中間焼鈍の効果が得られず耳率が高くなる。また６１０℃を越えると、鋳塊が溶融するおそれがある。
【００２６】
また前記の▲１▼均熱工程において、面削体は１００℃／時以下の加熱速度で均質化温度まで加熱することが好ましい。加熱速度が１００℃／時を越えると、部分的に溶融を生じる惧れがある。しかし加熱速度は、遅すぎると生産効率が低下する。この観点から、好ましい加熱速度は、１０〜１００℃／時の範囲内である。
【００２７】
また前記の▲１▼均熱工程において、均質化温度に保持する時間（均質化時間）は１時間以上とすることが好ましい。均質化時間が１時間未満では均質化が十分に進行しない場合がある。しかし長すぎても効果はなく生産効率が低下する。この観点から、好ましい均質化時間は１〜２４時間の範囲内である。この▲１▼均熱工程は均質化時間が比較的長いので通常、バッチ方式で炉中に置いて行われる。
【００２８】
▲２▼熱間圧延工程は、前記の均質化されたアルミニウム基合金鋳塊を熱間圧延して板材を形成するために行われる。本発明は、この▲２▼熱間圧延工程を、シングルミルのリバース式熱間粗圧延機のみを用いて行い得ることが特長である。この圧延機は、単基式の熱圧延ロールの前後に受座が設けられ、この熱圧延ロールの間に鋳塊を往復繰り返し通過させることで次第に薄板化する、従来から熱間粗圧延機として一般に用いられている装置である。
【００２９】
この▲２▼熱間圧延工程においては、圧延終了後にコイルとして巻き取られたアルミニウム板材の再結晶が、生じないか、一部生じたとしてもできるだけ少ないようにすることが特に重要である。このため熱間圧延終了直後のコイルの温度が２８０〜４８０℃の範囲内となるように調節する。
この仕上げ温度が２８０℃未満となるまで冷却すると板材が硬質となり、引き続き行う冷間圧延時にクラックが生じ易くなる。また、コイル巻き取り後に３５０℃を越えると、巻き取られた板材に一部再結晶が生じるが、後述する▲４▼第一中間焼鈍工程における好ましい条件の連続焼鈍により、この再結晶による悪影響を４８０℃までは緩和して解消できるので、この温度範囲とすることができる。即ち、この熱間圧延終了直後の温度を４８０℃まで高くしても、特願平９−１４２７９１号特許で得られる耳率１．８〜２．８と同等の耳率を得ることができる。更に、熱間圧延終了直後のコイルの温度を４００℃以上に高くすると、その後の第一冷間圧延で６０〜９０％の圧延率としてもクラックをほとんど生じないようにできるので、著しく歩留まりを改善できる。
【００３０】
前記の▲２▼熱間圧延工程において、圧延開始温度は５００℃以上とすることが好ましい。圧延開始温度が５００℃未満では、圧延荷重が大となり所要パス数が増加し効率が低下すると共に、前記の熱間圧延終了直後の許容温度範囲を維持することが困難になる。
最終パスの開始温度は４００℃以上とすることが好ましい。また、この熱間圧延工程の最終パスにおける圧延率は５０％以上、歪み速度は１〜５０ｓｅｃ^−１の範囲内とすることが好ましい。熱間圧延最終パスの開始温度、圧延率および歪み速度は、いずれも高いほど生産効率は向上するが、熱間圧延直後の板材温度が規定温度より高くなる場合が生じる。この場合には、熱間圧延終了直後のコイルに巻取られた板材の温度が２８０〜４８０℃の範囲内となるように、圧延ロールとコイル巻取り機との間で板材を強制的に冷却することが好ましい。
【００３１】
▲３▼第一冷間圧延工程は、前記の熱間圧延工程終了後の冷却した板材を、圧延率が６０〜９０％の範囲内となるように冷間圧延する。この工程における圧延率が６０％未満では耳率が大となる。圧延率は、高いほど▲５▼第二中間焼鈍工程において０〜９０゜耳となる立方体方位組織が多く生成する。ただし圧延率が９０％を越えると耳率は逆に高くなりサイドクラックも起こるようになる。この観点から、圧延率は７５〜９０％の範囲内とすることが好ましい。
【００３２】
▲４▼第一中間焼鈍工程は、前記冷間圧延後の板材に対し、図１に基本構成を示す連続焼鈍装置を用いて加熱速度１０〜２００℃／ｓの範囲（１０℃／ｓ以上、２００℃／ｓ以下の範囲）で加熱し、保持温度２８０〜３８０℃の範囲（２８０℃以上、３８０℃以下の範囲）に１〜３０ｓ（１ｓ以上、３０ｓ以下）保持し、冷却速度１０〜２００℃／ｓの範囲（１０℃以上、２００℃以下の範囲）で冷却するものとする。
【００３３】
図１に連続焼鈍装置（ＣｏｎｔｉｎｕｏｕｓＡｎｎｅａｌｉｎｇＬｉｎｅ：略称ＣＡＬ）の基本構成例を示すが、この例の連続焼鈍装置Ａは、供給ロール１から長尺のアルミニウム基合金板材２を引き出して緩衝装置３を介して１００ｍ程度の長い炉本体４に供給し、この炉本体４内で移動中に上記条件で焼鈍し、焼鈍後に炉本体４から引き出し、緩衝装置６を介して巻取ロール７に巻き取ることができる装置である。この連続焼鈍装置Ａによれば、炉本体４を通過するアルミニウム基合金板材２を連続単体処理できるために、バッチ式の焼鈍炉よりもより正確な加熱条件と冷却条件で焼鈍処理を行うことができる。
そして、連続焼鈍装置Ａならば、アルミニウム基合金板材２を供給ロール１に巻き付けたコイルの幅や径が異なっても、換言するとアルミニウム基合金板材２の幅や厚さ、処理するべき長さが異なっていても、製造したい順番に焼鈍処理できるために、同一の大きさのコイルのみを焼鈍炉に搬入して焼鈍していたバッチ式の焼鈍炉の場合に比べて中間在庫の増加を抑えることができる。
【００３４】
この焼鈍工程は、アルミニウム基合金板材を半軟化状態にもたらすものであって、焼鈍後の耐力；ＹＳ（Ｙｉｅｌｄｓｔｒｅｎｇｔｈ）を１００〜２５０ＭＰａの範囲、より好ましくは１３０〜２００ＭＰａの範囲とすることが好ましい。耐力がこの範囲になるように焼鈍するならば、後述の第二中間焼鈍後に０−９０゜耳となる立方体方位組織が多く生成する。
焼鈍温度が２８０℃未満または保持時間が１ｓ未満では十分な軟化が得られず結果的に耳率が高くなる。焼鈍温度が３８０℃を越えまたは保持時間が３０ｓを越えると軟化が過剰となって耳率が高くなる。
【００３５】
▲５▼第二冷間圧延工程は、前記の▲４▼第一中間焼鈍後の板材に対し、圧延率５〜４０％の範囲内となるように冷間圧延する工程である。実際上、圧延率を１０〜２０％の範囲内にするならば、耳率を低く抑えた状態で後述する最終冷間圧延工程において最終圧延率を９０％と高くにすることが可能となる。また、ここでの圧延率を５％以上、１０％未満の範囲、あるいは２０を越えて４０％以下の範囲とすると、最終冷間圧延工程において耳率を低く抑えた状態で可能な最終圧延率は低くなる傾向があり、圧延率７０〜９０％の範囲内であっても、７０％に近い範囲になる。
また、圧延率が５％未満では工程全体としての圧延パス数が増大して生産効率が低下する可能性があり好ましくない。圧延率が４０％を越えると、耳率が高くなり、本発明の製造方法を用いる理由がなくなる。
【００３６】
ここで特願平９−１４２７９１号特許の技術では、第１中間焼鈍と第２中間焼鈍の間に行う第二冷間圧延の圧延率を５〜３０％の範囲とする必要があり、この範囲の中でも最終的な製品の耳率をできるだけ低くするためには、好ましくは、１０〜２０％の範囲の圧延率とする必要があった。しかし、通常、工業的には、シングルスタンドのミルであっても、１パスで３０〜６０％もの圧延を行うのが普通であり、１０〜２０％の低圧下率の冷間圧延を行うことはパス数の増加の原因となるので好ましくない。しかし、本発明方法では、▲４▼第一中間焼鈍工程を連続焼鈍装置Ａで行うので、熱間圧延終了直後のコイルの温度を４００℃以下とした場合は、第二冷間圧延の圧延率を２０〜４０％と高くしても、特願平９−１４２７９１号特許の技術で得られた耳率１．８〜２．８と同等の耳率を得ることができる。従ってパス数の増加を抑えることができる。
【００３７】
▲６▼第二中間焼鈍工程は、前記の▲５▼第二冷間圧延工程を経た板材を、焼鈍温度が２７０〜４００℃の範囲内、焼鈍時間が２〜２４時間の範囲内で焼鈍する工程である。この工程は、前記▲１▼から▲５▼の工程を順次施した板材を十分に再結晶させ、立方体方位組織を十分に発達させ、高い０〜９０゜耳が発生する軟質材を得る工程である。この際、▲５▼第二冷間圧延工程を経た板材は、焼鈍温度が２７０〜３２０℃の範囲内に１〜２４時間保持することがより好ましい。この焼鈍温度の範囲内では温度が低いほど０〜９０゜耳が高くなる。
焼鈍温度が２７０℃または焼鈍時間が２時間未満では焼鈍の効果が不十分であり、耳率改善効果が得られない。焼鈍温度が４００℃を越え、または焼鈍時間が２４時間を越えても、耳率は更には改善されず、生産効率が低下する他、表面酸化などの弊害が生じ易くなる。焼鈍温度を２７０〜３２０℃に設定してほぼ完全に再結晶させた後、より高温で加熱すると、第二中間焼鈍後に最も高い０−９０゜耳が得られる。
【００３８】
▲７▼第三中間焼鈍工程は、前記の▲６▼第二中間焼鈍工程を経た後の板材を、焼鈍温度が４５０〜６００℃の範囲内、焼鈍時間が１〜３０秒間の範囲内で焼鈍する。この工程は、▲６▼第二中間焼鈍工程に引き続いて、短時間、より高い焼鈍温度にもたらすことで焼鈍による立方体方位組織の生成を更に増大させ、０〜９０゜耳を高くする効果があり、本発明において特に重要な工程である。焼鈍温度が４５０℃または焼鈍時間が２秒未満では焼鈍の効果が不十分であり、十分な強度が得られず耳率改善効果も低い。焼鈍温度が６００℃を越え、または焼鈍時間が６０秒を越えると、耳率は低く強度も大となるがネック成形時に加工硬化が生じ易くなる。この工程は焼鈍時間が短時間であるので、図１に示す連続焼鈍装置を用いて行うことが好ましい。以上の条件で行う▲７▼第三中間焼鈍工程であるならば、後工程で行う▲８▼最終冷間圧延工程において加工率を低くすることができるようになる。
【００３９】
▲７▼第三中間焼鈍工程における加熱速度および冷却速度は、何れも１０〜２００℃／秒とすることが好ましい。加熱／冷却速度が１０℃／秒未満では生産効率が低下する。また加熱／冷却速度が２００℃／秒を越えると、板材に歪みが発生し易くなる。
【００４０】
▲８▼最終冷間圧延工程では、前記の▲６▼第二中間焼鈍後の板材を、所定の板厚となるように、圧延率が４５〜９０％の範囲内で冷間圧延する。この工程を経た後に板材は所定の板厚の本発明のアルミニウム基合金板としてコイルに巻き取られ製品化される。
この工程における圧延率が４５％未満では、生産効率は高まるが缶体成形時やネック成形時に加工硬化を生じ易くなる。圧延率が９０％を越えると耳率が高くなる。また、この工程において４５％もの低い圧延率を採用できるのは、先の▲７▼第三中間焼鈍工程において連続焼鈍装置を用いて前述の好ましい条件で行ったためである。
ここで圧延率を低くできるならば、ＤＩ成形時にしわや破断が生じにくくなる効果を得ることができる。
【００４１】
以上説明の順に、▲１▼均熱工程と▲２▼熱間圧延工程と▲３▼第一冷間圧延工程と▲４▼第一中間焼鈍工程と▲５▼第二冷間圧延工程と▲６▼第二中間焼鈍工程、および、▲７▼第三中間焼鈍工程と▲８▼最終冷間圧延工程を施してアルミニウム基合金板を製造することにより、図２に示すようにアルミ缶を製造するためにカップ８とした場合に、耳率の少ないものを得ることができる。
なお、図２においてカップ底のアルミニウム基合金板の圧延方向を矢印で記載したが、この圧延方向を基準として、カップ８の周方向の位置を表す。このカップ８の上部（筒体を構成するアルミニウム基合金板ではサイド部）に〇印で示した箇所に生成されるものが０−９０゜耳であり、前述の工程のうち、最初の圧延加工では０−９０゜の位置に耳が生じ易く、圧延処理を重ねることにより×印で示した４５゜方向にも耳が生じやすくなる傾向がある。本発明の製造方法によれば、このアルミニウム基合金のサイド部、即ち、アルミニウム基合金板材を筒状に加工したものにあっては筒体開口部に現れる耳の耳率を抑えることができる。
【００４２】
【実施例】
次に、本発明を実施例により更に詳しく説明する。
以下の実施例および比較例において、原料のアルミニウム基合金としては表１に示す４種類の組成のものを、それぞれ合金Ａ，Ｂ，Ｃ，Ｄ，Ｅとして用いた。
【００４３】
【表１】

【００４４】
前記のそれぞれの合金の溶湯から半連続鋳造により重量６ｔ、厚さ５５０ｍｍの鋳塊を鋳造し、１２．５ｍｍの面削を行い面削鋳塊の試料を作製した。この試料のそれぞれについて、実施例は表１、比較例は表２に示す条件で順次、▲１▼均熱工程、▲２▼熱間圧延工程、▲３▼第一冷間圧延工程、▲４▼第一中間焼鈍工程、▲５▼第二冷間圧延工程、▲６▼第二中間焼鈍工程、▲７▼第三中間焼鈍工程および▲８▼最終冷間圧延工程を施し、深絞り成形用アルミニウム基合金板を製造した。表記以外の各工程の条件は全試料共通に下記の通りとした。
【００４５】
▲１▼均熱工程：加熱速度は平均５０℃／時、均質化温度は５７０℃±３℃とし、この温度範囲に８〜１０時間保持して均質化を行った。
▲２▼熱間圧延工程：前記の均熱工程終了直後の試料について、シングルミルのリバース式熱間粗圧延機のみを用いて行った。熱間圧延最終パスの開始温度は４５０℃〜５００℃、圧下量は６２％とした。表２，表３の「熱延巻取直後温度」は最終パス終了後コイルに巻取った直後の温度であり、これは圧延速度により調節した（圧延速度が遅いほど仕上げ温度が低くなる）。
なお、熱間圧延終了後、コイルに巻き取る直前に板幅方向両端に発生したサイドクラックを除去するため、各２０ｍｍ両端部をトリムした。
【００４６】
▲４▼第一中間焼鈍工程：長さ２０ｍの炉本体を備えた連続焼鈍装置を用い、加熱速度１５℃／ｓ、保持温度、保持時間を後述の表２に示す温度に、冷却速度３０℃／ｓに設定した。
後述の表４と表５に示す比較例においては、上記と同じ連続焼鈍炉を用いた場合（方法Ｃ’）の外に、バッチ式焼鈍炉を用い、（焼鈍温度−１００）℃から（焼鈍温度−１０）℃までの平均加熱速度を１４〜１７℃／時間とし、保持温度、時間を表４に示す条件とし、冷却は実体温度が２５０℃となるまでは炉冷とし、以降は大気中で冷却した場合（方法Ｂ’）の例も記載した。
なお、第一中間焼鈍直前に、サイドクラックを除去するために、各２０ｍｍ両端部をトリムした。
【００４７】
▲６▼第二中間焼鈍工程：バッチ式焼鈍炉を用い、（焼鈍設定温度−１００℃）から（焼鈍設定温度−１０℃）までの平均加熱速度は１４〜１７℃／時とした。焼鈍終了後の冷却は実体温度が約２５０℃となるまでは炉中で冷却し、以後は大気中で放冷した。
▲７▼第三中間焼鈍工程：フローティング式連続焼鈍炉を用い、常温から（焼鈍温度−１００℃）までの平均加熱速度は３０〜５０℃／秒とした。表２，表３の「温度」は焼鈍最高到達温度を示し、「時間」は４００℃から焼鈍最高到達温度に達するまでの時間（秒）を示す。冷却速度は、焼鈍最高到達温度から７０℃までの平均で、約１００℃／秒とした。
▲８▼最終冷間圧延工程：表２，表３の「最終冷延率」によって、板厚０．２８ｍｍの深絞り成形用アルミニウム基合金板を製造した。
【００４８】
上記の深絞り成形用アルミニウム基合金板を用いて深絞り試験を行った。
「耳率」は、深絞り加工によって絞られたカップについて、下式
耳率＝耳の高さ÷カップ高さ×１００（％）
により計算した。
耐力は、前記の深絞り成形用アルミニウム基合金板を焼付塗装の焼付け条件に相当する２１０℃で１０分間の加熱を行った後、ＪＩＳ５号引張り試験片に加工し、ＪＩＳＢ７７７１に従って０．２％耐力を求めた。
これらの結果を表２、表３（実施例）および表４、表５（比較例）に示す。
【００４９】
【表２】

【００５０】
【表３】

【００５１】
【表４】

【００５２】
【表５】

上記表２の結果から、本発明の条件を充たす実施例１〜１０の深絞り成形用アルミニウム基合金板（組成は表１記載）は、いずれも優れた耐力を維持したまま１．０〜１．６％の低い耳率を示した。
【００５３】
また、表３の最終冷間圧延率が９０％近い８９％の実施例１０では最終冷間圧延途中に、長さ１ｍｍ以上のサイドクラックが発生したため、各２０ｍｍ両端部をトリムしたが、その他の実施例１〜９では第１中間焼鈍直前に１回トリムを行うだけで最終板厚まで圧延可能であった。
これに対し、表４と表５において、▲４▼第一中間焼鈍工程における保持温度が本発明の範囲から外れ、結果として、第一中間焼鈍後の耐力が本発明範囲から外れた比較例１１、１２、▲５▼第二冷間圧延工程における「第二冷間圧延率」が本発明の条件から外れた比較例１４、▲６▼第二中間焼鈍工程における保持温度が本発明条件から外れた比較例１３、▲７▼最終冷間圧延工程の圧延率が本発明の条件から外れた比較例１５では、耳率が高いか、あるいは、耐力が著しく低くなった。
【００５４】
また、本発明者らが先に特許出願している特願平９−１４２７９１号明細書に記載の深絞り成形用アルミニウム基合金の製造方法に準じて、▲４▼第一中間焼鈍工程をバッチ式の焼鈍炉を用いて実施した比較例１６〜１８では、耳率が高いか、あるいは、第一冷間圧延途中にクラックを生じやすい。実施例１〜８は、熱間圧延巻取直後温度が４２０℃以上と高いため、８０〜８９％の第一冷間圧延を行っても、冷間圧延途中にほとんどサイドクラックが発生しなかったが、比較例１８では、熱間圧延巻取直後温度が低いために、８０％の第一冷間圧延途中に長さ１ｍｍ以上のサイドクラックが発生し、冷間圧延途中にトリムが必要であった。このため、第一中間焼鈍直前のトリムを略したが、最終冷間圧延途中に、再度長さ１ｍｍ以上のサイドクラックが発生し、再トリムが必要になった。一方、熱間圧延巻取直後温度を４２０℃と高くした場合、比較例１６に示すように、第一中間焼鈍にバッチ式の焼鈍炉を用いた方法では、耳率が高くなる。比較例１７では最終冷間圧延率が高く、第一中間焼鈍にバッチ式の焼鈍炉を用いた方法では、連続焼鈍装置を用いた実施例１０と同等の低い耳率が得られないことが判明した。
【００５５】
【発明の効果】
本発明の深絞り成形用アルミニウム基合金板の製造方法は、アルミニウム基合金鋳塊を、(1)均熱工程において５２０〜６１０℃に加熱し、(2)熱間圧延工程において熱間圧延終了時の板材温度が２８０〜４８０℃となるように熱間圧延し、前記熱間圧延の全工程にシングルミルのリバース式熱間粗圧延機を用いるとともに、(3)第一冷間圧延工程において圧延率が６０〜９０％となるように冷間圧延し、(4)第一中間焼鈍工程において連続焼鈍装置を用いて２８０〜３８０℃で１〜３０ｓの範囲内で焼鈍し、(5)第二冷間圧延工程において圧延率が５〜４０％となるように冷間圧延し、(6)第二中間焼鈍工程において２７０〜４００℃、２〜２４時間の範囲内で焼鈍し、(7)第三中間焼鈍工程において４５０〜６００℃、１〜３０秒間の範囲内で焼鈍し、次いで(8)最終冷間圧延工程において圧延率４５〜９０％の範囲内となるように冷間圧延するものであるので、(2)熱間圧延工程の全工程においてシングルミルのリバース式熱間粗圧延機のみを用いて、深絞り成形時に耳率を大幅に低減できるばかりでなく、製缶時にネックの縮径率を大きくしてもネック耳が生じにくい深絞り成形用アルミニウム基合金板を製造することができ、ＤＩ缶などを製造する際の製造コストを低減しかつ歩留まりを大幅に向上することができる。
【００５６】
次に、▲４▼第一中間焼鈍工程において連続焼鈍装置を用いて２８０〜３８０℃で１〜３０ｓの範囲内で焼鈍するので、前工程の▲２▼熱間圧延工程における熱間圧延終了時の板材温度を２８０〜４８０℃の範囲と広くすることができる。
【００５７】
また、▲４▼第一中間焼鈍工程において連続焼鈍装置を用い、保持温度２８０〜３８０℃で行い、焼鈍後の耐力を１００〜２５０ＭＰａとするならば、熱間圧延工程の熱間圧延終了時の板材温度管理幅を２８０〜４８０℃に広く範囲に設定することができるとともに、第二焼鈍後において０−９０゜耳を高くすることができ、最終的に耳率の低いアルミニウム基合金板を得ることができる。
更に、第三中間焼鈍において連続焼鈍装置を用い、４５０〜６００℃で１〜３０ｓの条件で行うならば、▲８▼最終冷間圧延工程において圧延率を４５％と低く設定することができ、ＤＩ成形時にしわや破断が生じにくくなる効果がある。
【図面の簡単な説明】
【図１】本発明製造方法の実施に用いる連続焼鈍装置の一例を示す概略構成図。
【図２】本発明製造方法で得られたアルミニウム基合金板を加工して得られるアルミ缶用筒体の斜視図。
【符号の説明】
Ａ・・・連続焼鈍装置、１・・・供給ロール、２・・・アルミニウム基合金板材、３、６・・・緩衝装置、４・・・炉本体、７・・・巻取ロール、８・・・筒体。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing an aluminum-based alloy plate for deep drawing, which has high strength and high ductility, and which can significantly reduce an ear ratio in deep drawing of a can or the like made of an aluminum-based alloy.
[0002]
[Prior art]
With the increasing demand for canned beverages and the like, recently, so-called DI (Deep Drawing & Ironing) cans made of an aluminum-based alloy suitable for such containers have been mass-produced. As a general method of manufacturing the body of this aluminum-base alloy DI can, an aluminum-base alloy plate is deep-drawn in multiple stages, then ironed to form a can body, and after baking coating, the pressure resistance is improved. In order to reduce the amount of material used for the lid member, which is relatively expensive, the neck processing for reducing the diameter is performed. The aluminum-based alloy plate used here is required to have both sufficient strength after can making and formability to withstand multi-stage deep drawing and ironing.
[0003]
In general, as an aluminum-based alloy for deep drawing, an Al-Mn-Mg-based alloy such as the American Aluminum Association Standard (AA) 3004 alloy is widely used. In order to produce a deep-drawing aluminum-based alloy sheet from this alloy, (a) first hot-roll an ingot of this alloy, and then (b) cold-roll to obtain a sheet having an appropriate thickness. The sheet material after cold rolling is subjected to (c) intermediate annealing, and further subjected to (d) cold rolling hardening treatment according to required strength.
[0004]
In the production process of the aluminum-base alloy sheet for deep drawing, in order to improve the strength of the sheet material, it is necessary to increase the cold rolling ratio in the cold rolling of the above (d). However, when the degree of cold rolling is increased, a so-called rolling texture develops, anisotropy appears remarkably during plastic deformation, and the top of the can body formed according to the rolling direction of the sheet material when deep drawing is performed. A phenomenon occurs in which the height of the edge changes in a valley-like manner.
The portion deformed in a mountain-valley shape is usually called an “ear”. After deep drawing, the can body is then ironed, and then trimmed to cut the opening horizontally to make the can height uniform in order to attach a lid member. Ears are also removed during this trimming, so if the height of the ears is high, the amount of plate material to be removed (hereinafter referred to as “ear ratio”) increases, the yield decreases, and the manufacturing cost increases. There was a problem of doing. Therefore, a plate material having a low ear ratio has been required.
[0005]
In general, when an aluminum-based alloy sheet is cold-rolled, a rolled texture having ears in a direction of 45 to 60 ° with respect to the rolling direction tends to develop. Therefore, in order to reduce the ear ratio, it is necessary to suppress the development of the rolling texture. It has been found that this can be achieved by controlling the state of formation of the recrystallized texture in the sheet material before cold rolling. That is, generally, a method of developing a recrystallized texture called “cubic orientation” that causes a deep drawing ear in the direction of 0-90 ° before cold rolling is used.
The development of the cubic orientation results in ears in the 0-90 ° direction, but the subsequent cold rolling does not significantly develop the ears in this direction, while also suppressing the development of the rolled texture producing the 45 ° ears. As a result, the peak of the ear at the periphery of the opening is made uniform. According to this method, a low-ear plate material in which a few 0-90 ° ears and 45 ° ears coexist after cold rolling at a rolling degree of 80% or more can be obtained.
[0006]
As a specific method of developing the recrystallized texture of the cubic orientation, the conditions during hot rolling are adjusted, and the coil wound up after hot rolling is cooled, or the coil wound up. There is known a method of controlling recrystallization which occurs when annealing is performed (Japanese Patent Laid-Open No. 5-125500).
In this method, the (d) cold rolling is performed on the recrystallized hot rolled sheet without performing the (b) cold rolling or (b) cold rolling and (c) intermediate annealing. At present, the thickness of the sheet material mainly used for DI cans is about 0.3 mm, so if this method is applied to make the final cold rolling reduction 80 to 90%, It is necessary to perform rolling so that the sheet thickness becomes 1.5 to 3 mm by cold rolling.
Therefore, usually, after rolling using a reverse hot rolling mill, further rolling using a tandem finishing hot rolling mill or a reverse hot finishing rolling mill equipped with coil winding devices on both sides of the rolling mill. Is used. However, these hot finishing mills are large-scale and expensive, and the use of these hot rolls imposes a large burden on manufacturing costs.
Further, as the thickness of the material for cans becomes thinner, the effect of the temperature drop between the rolling rolls and passes increases, and it is necessary to further increase the equipment capacity in order to maintain appropriate hot rolling conditions. Tended to increase.
[0007]
Therefore, a method using only a single-mill reverse hot rough rolling mill in all the steps of hot rolling was studied. However, when trying to produce thin sheet material using this rough rolling mill, the temperature drop between passes is remarkable, making it extremely difficult to maintain the hot rolling conditions for controlling recrystallization of the hot rolled sheet. Become. As a means for solving this problem, an element that imparts age hardening to the aluminum-based alloy is added, and after the cold rolling of the above (b), the intermediate annealing of the above (c) is performed at a relatively high temperature to form a solution. A method has been proposed in which sufficient strength can be obtained even when the rolling degree of the cold rolling in the above (d) is reduced (Japanese Patent Publication No. 60-35242).
[0008]
According to this method, since crystals are precipitated by heating the baking coating after forming the DI can body, softening due to heating during baking is suppressed, and sufficient strength can be obtained even when the cold rolling reduction is reduced. It became so. Therefore, even if the cubic texture is not sufficiently developed after the intermediate annealing (c), the rolling reduction of the cold rolling can be reduced, so that the development of the rolling texture becomes light, and the DI of the practical level having a relatively low ear ratio is obtained. Cans are now available. This method has a slightly higher ear ratio than when a finishing hot rolling mill is used, and therefore the trim amount is increased, but can be applied without using an expensive finishing hot rolling mill with high equipment cost. As a result, this is an advantageous method.
[0009]
However, recently, demands for reducing the diameter of the lid member in the DI can have increased due to economical and design requirements, and as a result, the diameter reduction rate of the neck has increased. However, when the diameter reduction ratio of the neck is increased, a new problem arises in this neck forming step in which the can height changes at the opening due to the anisotropy of the material, as in the case of deep drawing, and ears are generated. . The height variation of the opening caused by the neck forming is called "neck ear".
The opening of the can body is formed into a flange after the neck is formed, and this flange is used for tightening with the lid member.If the neck ear is large, the flange width differs depending on the direction or the shape of the neck part However, there arises a problem that the shape varies depending on the direction, so that the processing steps become complicated and the appearance is also adversely affected. Therefore, there has been a demand for an aluminum-based alloy plate for deep drawing which hardly causes a neck ear even when the diameter reduction ratio of the neck is increased.
[0010]
The opening of the can body is formed into a flange after the neck is formed, and this flange is used for tightening with the lid member.If the neck ear is large, the flange width differs depending on the direction or the shape of the neck part However, there arises a problem that the shape varies depending on the direction, so that the processing steps become complicated and the appearance is also adversely affected. Therefore, there has been a demand for an aluminum-based alloy plate for deep drawing which hardly causes a neck ear even when the diameter reduction ratio of the neck is increased.
[0011]
From such a background, the present inventors disclosed in Japanese Patent Application No. Hei 9-142791 that a single-mill reverse type hot rolling mill for both rough rolling and finish rolling was used to form a neck ear during deep drawing or neck forming. A patent application has been filed for a method for producing a difficult-to-draw aluminum alloy sheet for deep drawing.
According to the technology according to this patent application, a soaking step, a hot rolling step, a first cold rolling step, a first intermediate annealing step, a second cold rolling step, a second intermediate annealing step, and a third intermediate annealing step And when the final cold rolling step is sequentially performed to produce an aluminum-based alloy sheet,
The hot-rolling end temperature is in the range of 280 to 350 ° C., followed by 60 to 90% first cold rolling, and then in the 250 to 280 ° C. temperature range for 2 to 24 hours of first intermediate annealing. It was a requirement.
[0012]
[Problems to be solved by the invention]
The reason why the hot end temperature is set to 280 to 350 ° C. is to prevent recrystallization after hot rolling. However, if the temperature is outside this temperature range, work hardening in the subsequent first cold rolling is performed. In the process of performing cold rolling at a high rolling reduction of 60% or more, cracks are likely to occur on both sides of the aluminum-based alloy sheet, and it is necessary to trim both sides to remove the cracks. There was a problem of lowering. Therefore, the present inventors have reviewed the above manufacturing conditions and found manufacturing conditions that do not cause cracks even if the hot end temperature is made wider than the range of 280 to 350 ° C., and reached the present invention.
[0013]
In addition, the first intermediate annealing is a step for annealing the work-hardened coil by the first cold rolling to a semi-softened state, but the ear ratio changes depending on how much softening is performed. In order to reduce the variation of the ear ratio, it is necessary to strictly control the heating temperature and time. Therefore, the present inventors arrived at the present invention by studying the manufacturing conditions capable of relaxing the control of the heating temperature and time.
Furthermore, the first intermediate annealing is usually performed in an annealing furnace called a batch type. Here, an aluminum-based alloy plate is wound in a coil shape and carried into a furnace in a coil state to perform annealing. Since the heating rate varies depending on the coil width and conditions, that is, if the coil weight is different, the temperature cannot be controlled uniformly, so that the same heating temperature and time are required for the furnace according to the coil dimensions. It was necessary to change the operating conditions, and there was a problem that the dimensional control of the coil was complicated. That is, when a large number of coils are simultaneously loaded into the same furnace and processed, there is a problem in that heating and cooling conditions differ for each coil having a different size. Therefore, it is necessary to make the dimensions of all coils the same. Was.
For this reason, it is necessary to perform annealing separately according to the dimensions of the coil to be manufactured, and there is a problem that the inventory of intermediate products increases due to adjustment of the production time.
[0014]
The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to make it possible to manufacture a material having a high material strength without causing a decrease in yield and to significantly reduce an ear ratio after deep drawing. An object of the present invention is to provide a method for producing an aluminum-based alloy plate for deep drawing which can be reduced.
Furthermore, by performing the first intermediate annealing using a continuous annealing furnace, the aluminum-based alloy sheet can be individually annealed under desired conditions, and the temperature conditions of the hot rolling step and the rolling conditions of the second cold rolling step It is an object of the present invention to provide a method for manufacturing an aluminum-based alloy plate capable of relaxing the condition of the rate.
Also, even if the diameter reduction rate during neck molding is increased, neck ears are not easily generated, and the production time can be selected without being affected by the width and size of the aluminum-based alloy and the dimensions of the coil when it is used as a coil. It is an object of the present invention to provide a method for manufacturing an aluminum-based alloy plate that can reduce the stock of intermediate products.
[0015]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a method of manufacturing an aluminum-based alloy plate from an ingot of an aluminum-based alloy. (2) In the hot rolling step, the homogenized aluminum-based alloy ingot is hot-rolled to form a sheet, and at the end of hot rolling, The sheet material temperature is adjusted to a temperature range of 280 to 480 ° C., and a single-mill reverse hot rough rolling mill is used for all the steps of the hot rolling. (3) In the first cold rolling step, The hot-rolled sheet material is cold-rolled so that the rolling ratio falls within the range of 60 to 90%. (4) In the first intermediate annealing step, 10 to 200 ° C./s using a continuous annealing apparatus. At a heating rate in the range of 280-380 ° C. , And kept at this temperature range for 1 to 30 seconds, then cooled and annealed at a cooling rate in the range of 10 to 200 ° C./s, (5) in the second cold rolling step, the first intermediate annealing The subsequent sheet material is cold-rolled so that the rolling ratio is in the range of 5 to 40%. (6) In the second intermediate annealing step, the sheet material after the second cold rolling is performed at an annealing temperature of 270 to 270. Annealing in the range of 400 ° C. and the annealing time in the range of 2 to 24 hours, (7) in the third intermediate annealing step, using a continuous annealing device at a heating rate in the range of 10 to 200 ° C./s, 450 to 450 ° C. Heat to a temperature range of 600 ° C., hold at this temperature range for 1-30 seconds, then cool and anneal at a cooling rate of 10-200 ° C./s, then (8) in the final cold rolling step, The sheet material after the third intermediate annealing is cold-rolled so that the rolling reduction is in the range of 45 to 90%. It is characterized in.
[0016]
The aluminum-based alloy contains 0.1 to 0.4% by weight of Si, 0.3 to 0.6% by weight of Fe, 0.05 to 0.4% by weight of Cu, and 0.8 to 1% of Mn. It is preferable that the composition contains 0.5% by weight and 0.8 to 1.5% by weight of Mg, with the balance having a composition comprising Al and inevitable impurities.
The aluminum-based alloy further contains one or more of Cr: 0.25% by weight or less, Zn: 0.05 to 0.25% by weight, and Ti: 0.2% by weight or less in addition to the above elements. Is preferable.
[0017]
In the (1) soaking step, the homogenizing heating rate may be 100 ° C./hour or less, and the homogenizing time may be 1 hour or more.
In the (2) hot rolling step, it is necessary to use a single-mill reverse hot rough rolling mill in all the steps of hot rolling.
In the (2) hot rolling step, the starting temperature of the hot rolling may be 500 ° C. or more, and the starting temperature of the final hot rolling pass may be 400 ° C. or more.
In the (2) hot rolling step, the rolling reduction in the final hot rolling pass can be set to 50% or more.
[0018]
(5) In the second cold rolling step, the sheet material after the first intermediate annealing can be cold-rolled so that a rolling reduction is in a range of 20 to 40%.
(6) In the second intermediate annealing step, the sheet material after the second cold rolling is preferably annealed at an annealing temperature in a range of 270 to 320 ° C and an annealing time in a range of 2 to 24 hours.
(7) In the third intermediate annealing step, both the heating rate and the cooling rate can be in the range of 10 to 200 ° C./sec.
(4) The yield strength after the first intermediate annealing step can be in the range of 100 to 250 MPa.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
The method for producing an aluminum-based alloy plate for deep drawing according to the present invention is basically based on an ingot of an aluminum-based alloy as a base material, and each of the following steps (1) set at specific conditions: (2) hot rolling step, (3) first cold rolling step, (4) first intermediate annealing step, (5) second cold rolling step, (6) second intermediate annealing step, (7) first It is constituted by sequentially passing through three intermediate annealing steps and (8) final cold rolling step.
[0020]
According to the production method according to the present invention, the aluminum-based alloy sheet of the present invention is obtained, in which only a single-mill reverse hot rough rolling mill is used in all the steps of the hot rolling step, and the strength and the formability are compatible. For example, when used as a plate material for producing deep drawn cans such as DI cans, the ear ratio is reduced as compared with conventional plate materials, and the neck ears are reduced even when forming a DI can with a large neck diameter reduction ratio. The deformation can be prevented and the yield can be improved.
[0021]
The aluminum-based alloy used in the production method according to the present invention is basically based on Al, with 0.1 to 0.4% by weight of Si, 0.3 to 0.6% by weight of Fe, and 0.1% by weight of Cu. Those containing 0.5 to 0.4% by weight, 0.8 to 1.5% by weight of Mn and 0.8 to 1.5% by weight of Mg are used. Since the basic composition itself is not special and is within the range of the composition of various aluminum can alloys currently used in large quantities, the production method of the present invention uses recycled aluminum cans. It is suitable for economically and efficiently producing the aluminum-based alloy sheet of the present invention as a raw material.
[0022]
Among the above components, Si easily forms a compound with simultaneously contained Mg and has a solid solution hardening action, a dispersion hardening action, and a precipitation hardening action, and also forms a compound with Al, Mn, Fe, etc., and when ironing, Has the effect of preventing seizure on the die. If the content is less than 0.1% by weight, desired lubricating properties cannot be ensured, and if it exceeds 0.4% by weight, workability is deteriorated, which is inconvenient.
Fe has an effect of miniaturizing crystals and preventing seizure on a die during ironing. If the content is less than 0.3% by weight, the desired effect cannot be obtained, and if it exceeds 0.6% by weight, processability is deteriorated.
Cu easily forms a compound with Mg and contributes to solid solution hardening, dispersion hardening and precipitation hardening. If the content is less than 0.05% by weight, the desired effect cannot be obtained, and if it exceeds 0.4% by weight, the workability is deteriorated.
Mn easily forms a compound with Fe, Si, Al and the like, becomes a crystallization phase and a dispersed phase, exhibits a dispersion hardening effect, and has an effect of preventing seizure to a die during ironing. If the content is less than 0.8% by weight, desired curing properties cannot be obtained, and if it exceeds 1.5% by weight, processability is deteriorated.
Mg has a solid solution strengthening effect, enhances work hardenability by rolling, and exhibits a dispersion hardening and a precipitation hardening effect by coexisting with Si and Cu described later. If the content is less than 0.8% by weight, the desired effect cannot be obtained, and if it exceeds 1.5% by weight, the effect is reduced again.
[0023]
In addition to the above-mentioned Si, Fe, Cu, Mn and Mg, the present composition further contains 0.25% by weight or less of Cr, 0.05 to 0.25% by weight of Zn, and 0.2% by weight of Ti. It may be included within the following range.
Of these, Cr has the effect of suppressing recrystallization after hot rolling. However, if the content exceeds 0.25% by weight, this effect is rather reduced.
Zn has an effect of miniaturizing precipitates of Mg, Si, and Cu. If the content is less than 0.05% by weight, the desired effect cannot be obtained, and if it exceeds 0.25% by weight, the corrosion resistance deteriorates.
Ti has an effect of making crystal grains finer and improving workability. However, if the content exceeds 0.2% by weight, a coarse compound is formed and processability is deteriorated.
[0024]
In producing the aluminum-based alloy sheet of the present invention from the above composition, first, an ingot is cast from a molten metal of the composition according to a conventional method. The solidification rate at this time is usually 5 to 20 ° C./sec. The size of the ingot is, for example, 1.5 m × 0.5 m × 4 to 5 m.
Next, the surface of the ingot is ground by grinding by about 1 to 25 mm to create a smooth body having a smooth surface.
[0025]
This chamfered body is then sent to the (1) soaking step of the present invention. This {circle around (1)} soaking step is generally performed for homogenization of microsegregation caused by solidification of the molten metal, precipitation of supersaturated solid solution elements, transition of a metastable phase formed by solidification to an equilibrium phase, and the like.
In this {circle around (1)} soaking process, it is important that the homogenization temperature be in the range of 520 to 610 ° C. If the homogenization temperature is lower than 520 ° C., (5) the effect of the second intermediate annealing cannot be obtained, and the ear ratio becomes high. If the temperature exceeds 610 ° C., the ingot may be melted.
[0026]
In the above (1) soaking step, it is preferable to heat the chamfered body to a homogenizing temperature at a heating rate of 100 ° C./hour or less. If the heating rate exceeds 100 ° C./hour, there is a possibility that partial melting may occur. However, if the heating rate is too low, the production efficiency decreases. From this viewpoint, a preferable heating rate is in a range of 10 to 100 ° C./hour.
[0027]
Further, in the above (1) soaking step, the time for maintaining the temperature at the homogenization temperature (homogenization time) is preferably 1 hour or more. If the homogenization time is less than 1 hour, the homogenization may not proceed sufficiently. However, if it is too long, there is no effect and the production efficiency is reduced. In this regard, a preferred homogenization time is in the range of 1 to 24 hours. This (1) soaking step is usually carried out in a furnace in a batch mode since the homogenization time is relatively long.
[0028]
{Circle around (2)} The hot rolling step is performed to hot-roll the homogenized aluminum-based alloy ingot to form a sheet material. The present invention is characterized in that this (2) hot rolling step can be performed using only a single-mill reverse hot rough rolling mill. This rolling mill is provided with seats before and after a single-base hot rolling roll, and gradually reduces the thickness by repeatedly passing the ingot reciprocatingly between the hot rolling rolls. This is a commonly used device.
[0029]
In the (2) hot rolling step, it is particularly important that the recrystallization of the aluminum sheet material wound up as a coil after the completion of the rolling does not occur, or that it occurs as little as possible even if it occurs partially. Therefore, the temperature of the coil immediately after the completion of the hot rolling is adjusted to be in the range of 280 to 480 ° C.
If this finishing temperature is cooled to less than 280 ° C., the plate becomes hard, and cracks are likely to occur during the subsequent cold rolling. If the temperature exceeds 350 ° C. after winding the coil, recrystallization occurs partially in the rolled sheet material. However, continuous annealing under the preferable conditions in the first intermediate annealing step (4), which will be described later, reduces the adverse effect of this recrystallization. Since the temperature can be relaxed and eliminated up to 480 ° C., the temperature can be kept in this temperature range. That is, even if the temperature immediately after the completion of the hot rolling is increased to 480 ° C., an ear ratio equivalent to the ear ratio of 1.8 to 2.8 obtained in Japanese Patent Application No. 9-142791 can be obtained. Further, when the temperature of the coil immediately after the completion of the hot rolling is increased to 400 ° C. or more, cracks can hardly occur even at a rolling reduction of 60 to 90% in the subsequent first cold rolling, so that the yield is remarkably improved. it can.
[0030]
In the above (2) hot rolling step, the rolling start temperature is preferably set to 500 ° C. or higher. If the rolling start temperature is lower than 500 ° C., the rolling load increases, the number of required passes increases, the efficiency decreases, and it becomes difficult to maintain the allowable temperature range immediately after the end of the hot rolling.
The starting temperature of the final pass is preferably set to 400 ° C. or higher. Further, it is preferable that the rolling ratio in the final pass of the hot rolling step is 50% or more, and the strain rate is in the range of ^{1 to} 50 sec ^-1 . The higher the starting temperature, rolling ratio and strain rate of the final hot rolling pass, the higher the production efficiency, but the sheet temperature immediately after hot rolling may be higher than the specified temperature. In this case, the sheet material is forcibly cooled between the rolling rolls and the coil winder so that the temperature of the sheet material wound around the coil immediately after the completion of the hot rolling is in the range of 280 to 480 ° C. Is preferred.
[0031]
{Circle around (3)} In the first cold rolling step, the cooled sheet material after the completion of the hot rolling step is cold-rolled so that the rolling ratio falls within a range of 60 to 90%. When the rolling ratio in this step is less than 60%, the ear ratio becomes large. The higher the rolling reduction, the more the cubic orientation structure having a 0-90 mm ear is formed in the (5) second intermediate annealing step. However, when the rolling ratio exceeds 90%, the ear ratio is conversely increased and side cracks also occur. From this viewpoint, the rolling reduction is preferably in the range of 75 to 90%.
[0032]
(4) In the first intermediate annealing step, the sheet material after the cold rolling is heated at a heating rate of 10 to 200 ° C./s (10 ° C./s or more, using a continuous annealing apparatus having a basic configuration shown in FIG. 1). Heat at a temperature of 200 ° C./s or less), hold for 1 to 30 s (1 s to 30 s) in a holding temperature range of 280 to 380 ° C. (a range of 280 to 380 ° C.), and cool at a cooling rate of 10 to 200 Cooling is performed in the range of ° C / s (range of 10 ° C or more and 200 ° C or less).
[0033]
FIG. 1 shows an example of a basic configuration of a continuous annealing apparatus (continuous annealing line: CAL). In this example, a continuous annealing apparatus A pulls out a long aluminum-based alloy plate 2 from a supply roll 1 to remove a shock absorber 3. To the furnace body 4 having a length of about 100 m through the furnace body, annealing under the above-mentioned conditions while moving in the furnace body 4, drawing out from the furnace body 4 after annealing, and winding it up on the winding roll 7 via the buffer device 6. It is a device that can do. According to the continuous annealing apparatus A, since the aluminum-based alloy sheet 2 passing through the furnace main body 4 can be continuously and unitarily processed, the annealing processing can be performed under more accurate heating conditions and cooling conditions than in a batch type annealing furnace. it can.
Then, in the case of the continuous annealing apparatus A, even if the width and diameter of the coil around which the aluminum-based alloy plate 2 is wound around the supply roll 1 are different, in other words, the width and thickness of the aluminum-based alloy plate 2 and the length to be processed are different. Even if they are different, it is possible to perform the annealing process in the order in which they are to be manufactured, so that the increase in intermediate stock is suppressed compared to the batch type annealing furnace where only coils of the same size are carried into the annealing furnace and annealed. Can be.
[0034]
This annealing step brings the aluminum-based alloy sheet into a semi-softened state, and the proof stress after annealing; YS (Yield strength) is preferably in the range of 100 to 250 MPa, more preferably in the range of 130 to 200 MPa. . If annealing is performed so that the proof stress is in this range, a large cubic orientation structure having a 0-90 ° ear is generated after the second intermediate annealing described later.
If the annealing temperature is less than 280 ° C. or the holding time is less than 1 s, sufficient softening cannot be obtained, resulting in a high ear ratio. If the annealing temperature exceeds 380 ° C. or the holding time exceeds 30 s, the softening becomes excessive and the ear ratio increases.
[0035]
(5) The second cold rolling step is a step of performing (4) cold rolling on the sheet material after the first intermediate annealing so that the rolling rate falls within a range of 5 to 40%. Actually, if the rolling reduction is in the range of 10 to 20%, it is possible to increase the final rolling reduction to 90% in the final cold rolling step described later with the ear ratio kept low. Further, when the rolling ratio here is in the range of 5% or more and less than 10%, or in the range of more than 20 and 40% or less, the final rolling ratio possible in a state where the ear ratio is kept low in the final cold rolling step. Tends to be low, and even when the rolling reduction is in the range of 70 to 90%, it is in a range close to 70%.
On the other hand, if the rolling ratio is less than 5%, the number of rolling passes in the entire process may increase and the production efficiency may decrease, which is not preferable. If the rolling ratio exceeds 40%, the ear ratio increases, and there is no reason to use the production method of the present invention.
[0036]
Here, in the technology of Japanese Patent Application No. 9-127991, the rolling ratio of the second cold rolling performed between the first intermediate annealing and the second intermediate annealing needs to be in the range of 5 to 30%. Among them, in order to reduce the ear ratio of the final product as much as possible, it is necessary to preferably set the rolling ratio in the range of 10 to 20%. However, industrially, even in the case of a single-stand mill, it is normal to perform rolling of 30 to 60% in one pass, and to perform cold rolling at a low rolling reduction of 10 to 20%. Is not preferable because it causes an increase in the number of passes. However, in the method of the present invention, (4) the first intermediate annealing step is performed by the continuous annealing apparatus A. Therefore, when the temperature of the coil immediately after the end of the hot rolling is set to 400 ° C. or lower, the rolling rate of the second cold rolling is reduced. Can be increased to 20 to 40%, an ear ratio equivalent to the ear ratio of 1.8 to 2.8 obtained by the technique of Japanese Patent Application No. 9-142791 can be obtained. Therefore, an increase in the number of paths can be suppressed.
[0037]
(6) In the second intermediate annealing step, (5) the sheet material having undergone the second cold rolling step is annealed at an annealing temperature within a range of 270 to 400 ° C. and an annealing time within a range of 2 to 24 hours. It is a process. This step is a step of sufficiently recrystallizing the plate material that has been subjected to the above-mentioned steps (1) to (5) in order to sufficiently develop a cubic orientation structure, and to obtain a soft material having a high 0 to 90 ° ear. is there. At this time, it is more preferable to maintain the annealing temperature of the sheet material after the (5) second cold rolling step in the range of 270 to 320 ° C. for 1 to 24 hours. Within this annealing temperature range, the lower the temperature, the higher the 0-90 ° ear.
If the annealing temperature is 270 ° C. or the annealing time is less than 2 hours, the effect of the annealing is insufficient, and the ear rate improving effect cannot be obtained. If the annealing temperature exceeds 400 ° C. or the annealing time exceeds 24 hours, the ear ratio is not further improved, the production efficiency is reduced, and adverse effects such as surface oxidation are likely to occur. When the annealing temperature is set to 270 to 320 ° C. and the crystal is almost completely recrystallized and then heated at a higher temperature, the highest 0-90 ° ear is obtained after the second intermediate annealing.
[0038]
{Circle around (7)} The third intermediate annealing step comprises annealing the sheet material after the above {circle around (6)} second intermediate annealing step at an annealing temperature within a range of 450 to 600 ° C. and an annealing time within a range of 1 to 30 seconds. I do. This step has the effect of further increasing the generation of the cubic orientation structure by annealing by bringing the annealing temperature to a higher value for a short time, following the (6) second intermediate annealing step, following the second intermediate annealing step. This is a particularly important step in the present invention. If the annealing temperature is 450 ° C. or the annealing time is less than 2 seconds, the effect of annealing is insufficient, sufficient strength cannot be obtained, and the ear rate improving effect is low. If the annealing temperature exceeds 600 ° C. or the annealing time exceeds 60 seconds, the ear ratio is low and the strength is large, but work hardening is likely to occur during neck molding. This step is preferably performed using a continuous annealing apparatus shown in FIG. 1 since the annealing time is short. If the process (7) is the third intermediate annealing process performed under the above conditions, the working ratio can be reduced in the final cold rolling process (8) performed in the subsequent process.
[0039]
{Circle around (7)} Both the heating rate and the cooling rate in the third intermediate annealing step are preferably set to 10 to 200 ° C./sec. If the heating / cooling rate is less than 10 ° C./sec, the production efficiency is reduced. On the other hand, if the heating / cooling rate exceeds 200 ° C./sec, the plate tends to be distorted.
[0040]
(8) In the final cold rolling step, (6) the sheet material after the second intermediate annealing is cold-rolled in a rolling ratio of 45 to 90% so as to have a predetermined sheet thickness. After this step, the sheet material is wound around a coil as an aluminum-based alloy sheet of the present invention having a predetermined thickness to produce a product.
When the rolling ratio in this step is less than 45%, the production efficiency is increased, but work hardening is apt to occur at the time of can molding or neck molding. When the rolling ratio exceeds 90%, the ear ratio increases. The reason why a rolling reduction as low as 45% can be adopted in this step is that the third intermediate annealing step (7) was performed under the aforementioned preferable conditions using a continuous annealing apparatus.
Here, if the rolling reduction can be reduced, it is possible to obtain an effect that wrinkles and breakage are less likely to occur during DI molding.
[0041]
In the order given above, (1) soaking step, (2) hot rolling step, (3) first cold rolling step, (4) first intermediate annealing step, (5) second cold rolling step, and 6) a second intermediate annealing step, and (7) a third intermediate annealing step and (8) a final cold rolling step to produce an aluminum-based alloy plate, thereby producing an aluminum can as shown in FIG. Therefore, when the cup 8 is used, it is possible to obtain a small ear ratio.
Although the rolling direction of the aluminum-based alloy plate at the bottom of the cup is indicated by an arrow in FIG. 2, the circumferential position of the cup 8 is represented based on the rolling direction. In the upper portion of the cup 8 (the side portion in the case of the aluminum-based alloy plate constituting the cylindrical body), the portion generated at the position indicated by the mark 〇 is the 0-90 ゜ ear, and the first rolling process In this case, the ear tends to be formed at the position of 0-90 °, and the ear tends to be formed easily in the 45 ° direction indicated by the cross mark by repeating the rolling process. According to the manufacturing method of the present invention, in the side portion of the aluminum-based alloy, that is, in the case where the aluminum-based alloy plate is processed into a cylindrical shape, the ear ratio of the ear appearing at the opening of the cylindrical body can be suppressed.
[0042]
【Example】
Next, the present invention will be described in more detail with reference to examples.
In the following Examples and Comparative Examples, four types of compositions shown in Table 1 were used as aluminum alloys as raw materials as alloys A, B, C, D, and E, respectively.
[0043]
[Table 1]

[0044]
An ingot having a weight of 6 t and a thickness of 550 mm was cast from the melt of each of the above alloys by semi-continuous casting, and a 12.5 mm face was cut to prepare a sample of a face-cut ingot. For each of these samples, the examples are shown in Table 1 and the comparative examples are shown in Table 2 in the following order: (1) soaking step, (2) hot rolling step, (3) first cold rolling step, (4) ▼ First intermediate annealing step, 5) Second cold rolling step, 6) Second intermediate annealing step, 7) Third intermediate annealing step and 8) Final cold rolling step, for deep drawing An aluminum-based alloy plate was manufactured. The conditions of each step other than the notation were as follows for all samples.
[0045]
{Circle around (1)} Soaking process: The heating rate was 50 ° C./hour on average, and the homogenization temperature was 570 ° C. ± 3 ° C., and the homogenization was performed by maintaining the temperature range for 8 to 10 hours.
{Circle around (2)} Hot rolling step: The sample immediately after the above soaking step was carried out using only a single-mill reverse hot rough rolling mill. The starting temperature of the final hot rolling pass was 450 ° C. to 500 ° C., and the rolling reduction was 62%. "Temperature immediately after hot rolling and winding" in Tables 2 and 3 is the temperature immediately after winding into a coil after the final pass, and was adjusted by the rolling speed (the lower the rolling speed, the lower the finishing temperature).
After the hot rolling was completed, both ends of each 20 mm were trimmed to remove side cracks generated at both ends in the sheet width direction just before winding into a coil.
[0046]
{Circle around (4)} First intermediate annealing step: using a continuous annealing apparatus equipped with a furnace body having a length of 20 m, heating rate 15 ° C./s, holding temperature and holding time to the temperature shown in Table 2 below, cooling rate 30 ° C. / S.
In Comparative Examples shown in Tables 4 and 5 described below, in addition to the case where the same continuous annealing furnace was used as described above (Method C ′), a batch annealing furnace was used and (annealing temperature −100) ° C. to (annealing). Temperature: The average heating rate up to -10) ° C is 14 to 17 ° C / hour, the holding temperature and time are the conditions shown in Table 4, and the cooling is furnace cooling until the actual temperature reaches 250 ° C. In the case of cooling by (Method B '), an example was also described.
Immediately before the first intermediate annealing, both ends of each 20 mm were trimmed to remove side cracks.
[0047]
{Circle around (6)} Second intermediate annealing step: Using a batch annealing furnace, the average heating rate from (set annealing temperature −100 ° C.) to (set annealing temperature −10 ° C.) was set to 14 to 17 ° C./hour. After the completion of the annealing, cooling was performed in a furnace until the actual temperature reached about 250 ° C., and thereafter cooling was performed in the atmosphere.
{Circle around (7)} Third intermediate annealing step: A floating type continuous annealing furnace was used, and the average heating rate from normal temperature to (annealing temperature −100 ° C.) was 30 to 50 ° C./sec. “Temperature” in Tables 2 and 3 indicates the maximum annealing temperature, and “Time” indicates the time (second) from 400 ° C. to the maximum annealing temperature. The cooling rate was about 100 ° C./sec on average from the highest annealing temperature to 70 ° C.
(8) Final cold rolling step: An aluminum-based alloy plate for deep drawing with a thickness of 0.28 mm was manufactured according to the “final cold rolling ratio” in Tables 2 and 3.
[0048]
A deep drawing test was performed using the above-mentioned aluminum base alloy plate for deep drawing.
The “ear ratio” is the lower formula ear ratio = ear height ÷ cup height × 100 (%) for a cup drawn by deep drawing.
Was calculated by
The proof stress is as follows. After heating the aluminum-based alloy plate for deep drawing at 210 ° C. for 10 minutes corresponding to the baking conditions of baking coating, it is processed into a JIS No. 5 tensile test piece, and 0.2% in accordance with JIS B7771. The proof stress was determined.
The results are shown in Tables 2 and 3 (Examples) and Tables 4 and 5 (Comparative Examples).
[0049]
[Table 2]

[0050]
[Table 3]

[0051]
[Table 4]

[0052]
[Table 5]

From the results in Table 2 above, the aluminum-based alloy plates for deep drawing of Examples 1 to 10 satisfying the conditions of the present invention (compositions are described in Table 1) are all 1.0 to 1 while maintaining excellent proof stress. The ear rate was as low as 0.6%.
[0053]
Further, in Example 10 in which the final cold rolling ratio in Table 3 was 89%, which is close to 90%, side cracks of 1 mm or more in length occurred during the final cold rolling. Therefore, both ends of each 20 mm were trimmed. In Examples 1 to 9, it was possible to roll to the final sheet thickness only by performing trim once just before the first intermediate annealing.
On the other hand, in Tables 4 and 5, (4) Comparative Example 11 in which the holding temperature in the first intermediate annealing step was out of the range of the present invention, and as a result, the proof stress after the first intermediate annealing was out of the range of the present invention. , 12, (5) Comparative Example 14 in which "second cold rolling ratio" in the second cold rolling step was out of the condition of the present invention, and (6) Holding temperature in the second intermediate annealing step was out of the condition of the present invention. In Comparative Example 13, {circle around (7)} Comparative Example 15 in which the rolling reduction in the final cold rolling step deviated from the conditions of the present invention, the ear ratio was high or the proof stress was extremely low.
[0054]
In addition, according to the method of manufacturing an aluminum-based alloy for deep drawing described in Japanese Patent Application No. 9-142791 previously filed by the present inventors, (4) the first intermediate annealing In Comparative Examples 16 to 18 performed using the annealing furnace of the formula, the ear ratio is high or cracks are easily generated during the first cold rolling. In Examples 1 to 8, since the temperature immediately after hot rolling and winding was as high as 420 ° C. or more, even when the first cold rolling of 80 to 89% was performed, almost no side cracks occurred during the cold rolling. However, in Comparative Example 18, since the temperature immediately after hot rolling was low, side cracks of 1 mm or more in length occurred during the 80% first cold rolling, and trim was required during the cold rolling. Was. For this reason, the trim immediately before the first intermediate annealing was omitted, but side cracks having a length of 1 mm or more occurred again during the final cold rolling, and the trim was required again. On the other hand, when the temperature immediately after hot rolling and winding is increased to 420 ° C., as shown in Comparative Example 16, the ear ratio increases in the method using the batch-type annealing furnace for the first intermediate annealing. In Comparative Example 17, the final cold rolling ratio was high, and it was found that the method using a batch type annealing furnace for the first intermediate annealing could not obtain a low ear rate equivalent to that of Example 10 using the continuous annealing apparatus. did.
[0055]
【The invention's effect】
In the method for producing an aluminum-based alloy plate for deep drawing according to the present invention, the aluminum-based alloy ingot is heated to 520 to 610 ° C. in the (1) soaking step, and hot rolling is completed in the (2) hot rolling step. Hot rolling such that the sheet temperature at the time becomes 280 to 480 ° C., and using a single-mill reverse hot rough rolling mill in all the steps of the hot rolling , (3) in the first cold rolling step Cold rolling is performed so that the rolling ratio becomes 60 to 90%. (4) In the first intermediate annealing step, annealing is performed at 280 to 380 ° C. in the range of 1 to 30 s using a continuous annealing apparatus. (2) cold rolling so that the rolling reduction is 5 to 40% in the second cold rolling step, and (6) annealing in the range of 270 to 400 ° C. for 2 to 24 hours in the second intermediate annealing step; 450-600 ° C. in the third intermediate annealing step, annealing within a range of 1 to 30 seconds, Next, (8) in the final cold rolling step, cold rolling is performed so as to fall within a range of a rolling rate of 45 to 90%. Using only a rough rolling mill, not only can the ear ratio be greatly reduced during deep drawing, but also the aluminum base alloy sheet for deep drawing can be used to prevent the occurrence of neck ears even when the neck diameter reduction ratio is increased during can making. The manufacturing cost can be reduced when manufacturing DI cans and the like, and the yield can be greatly improved.
[0056]
Next, (4) in the first intermediate annealing step, annealing is performed at 280 to 380 ° C. in the range of 1 to 30 s using a continuous annealing apparatus. Can be broadened to the range of 280 to 480 ° C.
[0057]
(4) In the first intermediate annealing step, if a continuous annealing apparatus is used and the holding temperature is 280 to 380 ° C. and the proof stress after annealing is 100 to 250 MPa, the hot rolling at the end of the hot rolling in the hot rolling step The plate material temperature control width can be set to a wide range from 280 to 480 ° C., and the 0-90 ° ear can be increased after the second annealing, and finally an aluminum-based alloy plate having a low ear rate can be obtained. be able to.
Further, if the third intermediate annealing is performed using a continuous annealing apparatus at 450 to 600 ° C. for 1 to 30 s, (8) the rolling reduction can be set as low as 45% in the final cold rolling step. This has the effect that wrinkles and breaks are less likely to occur during DI molding.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an example of a continuous annealing apparatus used for carrying out the manufacturing method of the present invention.
FIG. 2 is a perspective view of an aluminum can cylinder obtained by processing an aluminum-based alloy plate obtained by the production method of the present invention.
[Explanation of symbols]
A: continuous annealing device, 1: supply roll, 2: aluminum base alloy plate, 3, 6: buffer device, 4: furnace body, 7: winding roll, 8. ..Cylinders.

Claims

When manufacturing an aluminum-based alloy plate from an aluminum-based alloy ingot,
(1) In the soaking step, the aluminum-based alloy ingot is heated to a homogenization temperature in the range of 520 to 610 ° C to homogenize,
(2) In the hot rolling step, the homogenized aluminum-based alloy ingot is hot-rolled to form a sheet, and the sheet temperature at the end of hot rolling is adjusted to a temperature range of 280 to 480 ° C. And
While using a single-mill reverse hot rough rolling mill for all the steps of the hot rolling,
(3) In the first cold rolling step, the sheet material after the completion of the hot rolling is cold-rolled so that the rolling ratio falls within a range of 60 to 90%,
(4) In the first intermediate annealing step, using a continuous annealing device, heating to a temperature range of 280 to 380 ° C. at a heating rate of 10 to 200 ° C./s, and holding in this temperature range for 1 to 30 seconds; Then, it is annealed by cooling at a cooling rate in the range of 10 to 200 ° C./s,
(5) In the second cold rolling step, the sheet material after the first intermediate annealing is cold-rolled so that the rolling ratio is in the range of 5 to 40%,
(6) In the second intermediate annealing step, the sheet material after the second cold rolling is annealed at an annealing temperature within a range of 270 to 400 ° C. and an annealing time within a range of 2 to 24 hours,
(7) in the third intermediate annealing step, using a continuous annealing device, heating to a temperature range of 450 to 600 ° C. at a heating rate of 10 to 200 ° C./s, and holding at this temperature range for 1 to 30 seconds; It is then annealed by cooling at a cooling rate in the range of 10-200 ° C / s, then
(8) In the final cold rolling step, the sheet material after the third intermediate annealing is cold-rolled so that the rolling ratio falls within a range of 45 to 90%, and the aluminum base alloy for deep drawing. Plate manufacturing method.

The aluminum-based alloy,
Si: 0.1 to 0.4% by weight,
Fe: 0.3 to 0.6% by weight,
Cu: 0.05 to 0.4% by weight;
Mn: 0.8-1.5% by weight and Mg: 0.8-1.5% by weight
2. The method for producing an aluminum-based alloy plate for deep drawing according to claim 1, wherein the alloy has a composition comprising Al and inevitable impurities.

The aluminum-based alloy,
Si: 0.1 to 0.4% by weight,
Fe: 0.3 to 0.6% by weight,
Cu: 0.05 to 0.4% by weight;
Mn: 0.8-1.5% by weight and Mg: 0.8-1.5% by weight
Containing, further,
Cr: 0.25% by weight or less Zn: 0.05 to 0.25% by weight,
The deep drawing forming material according to claim 1, wherein one or more of Ti: 0.2% by weight or less is contained, and the remainder has a composition of Al and unavoidable impurities. A method for manufacturing an aluminum-based alloy plate.

The deep drawing according to any one of claims 1 to 3, wherein in the (1) soaking step, a homogenizing heating rate is set to 100 ° C / hour or less and a homogenizing time is set to 1 hour or more. Of manufacturing aluminum base alloy sheet for automobile

The method according to any one of claims 1 to 4 , wherein in the (2) hot rolling step, a hot rolling start temperature is set to 500 ° C or higher, and a hot rolling final pass start temperature is set to 400 ° C or higher. 3. The method for producing an aluminum-based alloy plate for deep drawing according to item 1.

The production of an aluminum-based alloy sheet for deep drawing according to any one of claims 1 to 5 , wherein in the (2) hot rolling step, a rolling reduction in a final hot rolling pass is set to 50% or more. Method.

The (5) according to claim 1-6 in the second cold rolling step, the plate material after the first intermediate annealing, rolling rate is characterized in that the cold rolling to be within the range of 20-40% The method for producing an aluminum-based alloy plate for deep drawing according to any one of the above.

(6) In the second intermediate annealing step, the sheet material after the second cold rolling, the annealing temperature is in the range of 270 to 320 ° C., annealing time is in the range of 2 to 24 hours, characterized in that the annealing The method for producing an aluminum-based alloy plate for deep drawing according to any one of claims 1 to 7 .

(7) In the third intermediate annealing step, for deep drawing according to any one of claims 1 to 8, characterized in that the heating rate and the range of the cooling rate both 10 to 200 ° C. / sec A method for manufacturing an aluminum-based alloy plate.

The method according to any one of claims 1 to 9 , wherein the proof stress after the (4) first intermediate annealing step is in a range of 100 to 250 MPa.