JP3604835B2

JP3604835B2 - Method for manufacturing aluminum DI can having irregular pattern on body

Info

Publication number: JP3604835B2
Application number: JP26122496A
Authority: JP
Inventors: 泰史榎木
Original assignee: Daiwa Can Co Ltd
Current assignee: Daiwa Can Co Ltd
Priority date: 1996-09-11
Filing date: 1996-09-11
Publication date: 2004-12-22
Anticipated expiration: 2016-09-11
Also published as: JPH1085873A

Description

【０００１】
【発明の属する技術分野】
本発明は、胴部に凹凸模様をもつアルミニウムの絞りしごき缶（以下ＤＩ缶と略称する）の製造に関し、特に絞りしごき加工が施されたアルミニウムＤＩ缶の胴部に焼鈍処理した後に膨出して加工硬化させ、バルジ加工により凹凸模様を胴部に施すアルミニウムＤＩ缶及びその製造方法に関する。
【０００２】
【従来の技術】
飲料缶においては、アルミニウム板を円筒状に絞りしごき加工し、缶底と胴を一体成形したＤＩ缶が広く用いられている。この容器を使って販売する各メーカーにおいては、商品のイメージをより良く見せ、ユーザーに購買意欲が涌くようなデザインの開発を行って来た。
【０００３】
それらのほとんどは、缶胴側壁への印刷によるものであったが、缶胴側壁にビードを入れたり、バルジ加工して缶胴に凹凸を入れる等、缶体を変形させ、商品の差別化、個別化を狙うことも試みられている。
【０００４】
バルジ加工においては、缶体を自由な形に変えることができ、商品の個別化を目的とする上で最適な加工方法であるが、飲料缶に使われるしごき加工されたそのままの缶を加工すると、残留応力のため亀裂が生じることがある。このため一度焼鈍しなければならず、一方焼鈍を行うと材料が軟化して耐圧力が減少し、特に缶詰製造時の殺菌等により、缶底が缶内圧によりバックリングしたり、また缶胴強度の減少により、ネッキング時のネック成形力や内容物充填時のリフター圧により座屈が生ずる。
【０００５】
座屈に関しては、多くの場合、缶胴径より小さいボトム部の接地直径に向かうテーパー壁上部と、缶胴側壁下端部の境界部で発生する。しかし元板厚が十分厚い場合には、ボトム部の板厚が増すため、缶胴部分で座屈が生ずる。さらにバルジ加工により凹凸模様を施すと、軸荷重は集中荷重として働き、こういった変形部分で座屈する。
【０００６】
アルミニウム合金３００４−Ｈ１９１材を使った２１１径や２０２径の飲料缶では、しごき加工された状態において、缶胴部で硬度が８５〜９５Ｈｖ（ビッカース硬度）を有し、壁厚が０．１０５ｍｍの時、テーパー壁上部と缶胴側壁下端部の境界部の座屈強度は１３０ｋｇｆ程度あり、缶胴座屈強度は約１９０ｋｇｆ程度ある。また缶底部では硬度８２〜８９Ｈｖを有し、板厚が０．２８ｍｍの場合、耐圧力は６ｋｇｆ／ｃｍ^２以上が確保される。
【０００７】
缶胴部へ凹凸模様をつける場合、これらの缶を焼鈍処理し、その部分にバルジ加工が施される。ところがこのバルジ加工が全体膨出でなく、部分的な膨出の場合、膨出加工されなかった部分では加工硬化が起こらない低い硬度（４０〜５０Ｈｖ）のままの部分が残り、これらの部分は缶の強度を著しく損なう。
【０００８】
例えば、バルジ加工前で、テーパー壁上部と缶胴側壁下端部の境界部の座屈強度は約７０ｋｇｆ，缶胴の座屈強度は約１００ｋｇｆとなり、また耐圧強度が４ｋｇｆ／ｃｍ^２に低下し、耐圧容器としての機能を果たさなくなる。
【０００９】
この様な理由から、上記の強度不足を補う為に材料の厚みを厚くする方法が考えられるものの、それでは材料コストが上がり不経済になるため、金属製薄肉耐圧容器のバルジ加工は従来殆ど実施されていなかった。
【００１０】
【発明が解決しようとする課題】
しかしながら、飲料缶での容器としての個別化需要は強く、絞りしごき加工を行った薄肉ＤＩ缶のバルジ加工への要求は根強くあった。現在のところ、焼鈍せずに変形できるビード加工等の方法が行われているが、ビード加工ではデザインの自由度がなく、缶需要者の満足を得るまでには至っていない。
【００１１】
また特公昭５９−１８２６１号公報に開示の技術では、焼鈍処理までは至らないものの、缶内面における合成樹脂皮膜形成時の乾燥用加熱器を使ってしごき加工中の残留応力除去を行い、バルジ成形する方法が提案されている。
【００１２】
この方法では、材料が完全に焼鈍に至るまでの途中の段階、すなわち不完全焼鈍を行い、ある程度軟化した缶を膨出成形する方法と考えられるが、缶内面の樹脂皮膜の乾燥温度との関係から、焼鈍温度の設定が限られ、希望の硬度に焼鈍軟化することが難しい。
【００１３】
このことは、バルジ加工において十分な膨出変形が得られなかったり、時には複雑な形状において破断を起こす等の問題が生じ、またたとえ不完全焼鈍用に専用のオーブンを設置したとしても焼鈍温度の調整が困難で、材料の引っ張り性能や耐力にばらつきが発生する。又オーブンでの焼鈍では局所に限っての焼鈍は難しく、缶底も軟化するため、内容物の内圧により缶底がバックリングする恐れがある。
【００１４】
以上のことより薄肉ＤＩ缶の製造段階において、耐圧容器としての性能を損なうこと無く、バルジ加工に適した硬度の缶を安定的に得ることができ、さらに自由なデザインのバルジ加工を可能とし、且つ材料を節減し得るアルミニウムＤＩ缶の出現が望まれていた。
【００１５】
本発明は、特にＤＩ缶の胴部の所定の幅に亘り焼鈍処理した後に膨出して加工硬化させ、その位置に凹凸模様を施すようにして上記課題を解決した、凹凸模様をもつアルミニウムＤＩ缶及びその製造方法を提供する。
【００１６】
【課題を解決するための手段】
本発明の製造方法は、一体成形による円筒状に成形した缶胴部につながる下部に、環状に下方向に突出している接地部および内部に向け湾曲したドーム部により底部を形成したＤＩ缶を加熱処理した後、開口端部側より膨出部材を挿入して膨出成形して缶の胴部の少なくとも一部に凹凸模様を形成するアルミニウムＤＩ缶の製造方法において、アルミニウム合金３００４−Ｈ１９１材からなるＤＩ缶の、硬度８５〜９５Ｈｖを有する胴部の上端エッジ部から缶底部手前の缶胴部を高周波誘導加熱により焼鈍して該上端エッジ部を含む缶胴部を硬度４０〜５０Ｈｖとなるように軟化させ、次いで缶外面に塗装、印刷し、缶内面に合成樹脂被膜を塗布する工程を経た後、缶蓋径に合わせるように缶エッジ部開口端を所定の径に縮径し、更に、この缶を缶底形状に合わせた底金型および加工する元の缶胴直径より大きく半割りとされた円筒状側壁金型により組立て構成された円筒状金型内に押し込め、前記開口端部側より膨出部材を挿入して、該膨出部材により、前記縮径した部分を除く缶胴部を前記金型に押圧し、直径比が元の直径に対し１．０２〜１．１１の範囲で、硬度が５２〜６０Ｈｖの範囲となるように該缶胴部全体を均一に且つ同心状に膨出成形した後、前記円筒状側壁金型より取り出し、更にこの缶の胴部の少なくとも一部に凹凸模様を施し、缶胴部の硬度を５５〜７０Ｈｖの範囲とし、引き続き蓋を巻き締めるためのフランジ加工を缶開口端部に施すことを特徴とする胴部に凹凸模様をもつアルミニウムＤＩ缶の製造方法である。
【００２１】
【発明の実施の形態】
図１は、本発明によるアルミニウムＤＩ缶の製造過程におけるＤＩ缶の実施の形態例を示す縦断面図、図２はＤＩ缶（バルジ成形缶）の製造方法を説明する工程図である。
【００２２】
先ず工程Ａに示すアルミニウムＤＩ缶１は、一体成形により円筒状に成形した缶胴部２と、この缶胴部につながる缶底部３に、環状に下方向に突出している接地部４および内部に向け湾曲したドーム部５により形成される。
【００２３】
本発明におけるバルジ成形缶の製造方法にあっては、先ず次工程Ｂの焼鈍による缶軟化の影響が缶底部３にまで及ばないように、缶胴部２のみの焼鈍を行う必要がある。焼鈍に当たっては、オーブンによる方法と高周波誘導加熱があるが、缶胴部２に部分的に焼鈍する為には、リング状にコイルを巻いた高周波誘導加熱が有効である。
【００２４】
加熱範囲Ａは、缶底接地部４より上方８ｍｍ程度の缶胴部２と缶底部３の境界部７から、缶開口端部６までの缶胴部２に行う。缶底部の接地部４より上方８ｍｍの間は、缶をスタックさせるために缶胴部２から胴部外径より小さな接地直径部までテーパー壁Ｂにて構成される部分であり、この個所にこの後工程の凹凸模様が施されることはない。
【００２５】
さらに容器に軸荷重が働いた場合、テーパー壁Ｂ上部と缶胴部下端部の境界部７で座屈するので、この部分の材料の軟化を防ぐ必要がある。そして、缶底中央８にあっては、内圧によるバックリングを防止する必要から、缶底接地部８ｍｍ上方の範囲とする加熱範囲を定めた。
【００２６】
このことにより、缶底部３の耐圧強度とテーパー壁Ｂと缶胴側壁下端部の境界部７の座屈強度は、通常の絞りしごき缶（ＤＩ缶）に対し、多少の熱影響はあるものの、所定以上の強度に維持される。
【００２７】
次の工程Ｃとして、缶外面に塗装や印刷を行う。焼鈍前では、熱によりインクが変色するおそれがあり、バルジ加工後では、凹凸により印刷できないので、焼鈍後のこの工程で行う。
【００２８】
さらに次の工程Ｄにおいて、缶内面に合成樹脂皮膜を例えばスプレーにより形成しておく必要がある。これは内容物が直接缶にふれない様にすること以外に、バルジ加工に使用される膨出部材が、缶胴内面を滑りながら合成樹脂皮膜を拡張させ、膨出部材と缶内面地金が直接接触するのを防止する。
【００２９】
これは金属地のままでは膨出部材との摩擦による損傷が大きくなり、特に膨出部材としてゴム等が使用されると、ゴムが発熱したり、また表面が荒れ、膨出部材の寿命が短くなる。このような理由から、事前にスプレー等を用いて缶内面に合成樹脂皮膜を形成する。
【００３０】
次に工程Ｅにおいて、バルジ成形に先立ち、缶の開口端部６は、蓋を巻き締めるための口径まで縮径される。その理由は、次の膨出成形に先立ち縮径しておかないと、缶胴部２の膨出時に開口端部６の材料が引き込まれるため、焼鈍むらや材料の偏肉により同一缶内で缶高がばらつく現象が起きる。
【００３１】
この缶高がばらつくと、巻締時に必要なフランジ長さもばらつくため、巻締不良の原因となり漏れ等を発生する。この理由から先行して縮径を行い、開口端部６に加工硬化を与え、材料の流れを抑制することで缶高ばらつき等の問題を解決することができる。
【００３２】
開口端部６を縮径され、かつ缶胴部２のみ焼鈍された缶は、次の工程Ｆにおいて胴部全体を決められた直径比を有する円筒状の金型内で均一に且つ同心状に膨出成形される。この時の加工硬化によって再度缶胴部２に強度が与えられる。与えられる強度は、直径比により調整される。
【００３３】
一般に材料の硬さは、引張強さとほぼ比例関係にあり、引張強さをσｖとすると、ビッカース硬度Ｈｖとの関係は次の（１）式、数１で表される。
【００３４】
【数１】
σｖ＝ＣＨｖ ………（１）
ただしＣは比例定数である。
【００３５】
従って硬度の上昇は、ほぼ硬度の比率分だけ引張強度が改善されることなる。例えば加工硬化による硬度を５５Ｈｖ以上確保することを目的とすれば、引張強度は、焼鈍後の再結晶状態のアルミニウム硬度（４０〜４５Ｈｖ）に対し、２５〜３５％改善することとなる。
【００３６】
ここで硬度が完全に回復するまで過度に缶胴部２全体の膨出成形を行うと、次工程のデザインにおいて必要な凹凸部の変形ができず、材料が破断するに至る。したがって完全に硬度が回復せずとも、凹凸模様を施すのに十分な変形量をとれる範囲内で事前に膨出成形を行い、焼鈍で低下した硬度をある程度回復させることで缶体強度を上げるように膨出成形を行う。
【００３７】
アルミニウム合金３００４−Ｈ１９１材の焼鈍直後の缶は、伸びが２１％，硬度４５Ｈｖの機械的性質を有する。この伸びが２１％有するため、膨出可能な最大直径比はおおよそ１．２１まで可能となる。
【００３８】
ここで事前膨出成形に伴う伸びは、次の凹凸模様を施すのに十分な変形量が確保できることと、急変する凹凸の形状でも割れや肉厚が極端に薄くなるのを防止できる伸びは１０％程度必要であり、これを確保するため最大で１１％が必要となる。すなわち事前に缶胴を膨出成形できる最大直径比は１．１１となる。
【００３９】
また膨出最低直径比は、１．０より大きければ良いわけだが、加工初期に耐力（０．２％の永久伸びを生ずる降伏応力）が急激に向上するので、２％程度の加工を事前に与え、容器としての強度を改善する。このため、膨出最低直径比を１．０２と定めた。
【００４０】
膨出成形の方法については、まずアルミニウムＤＩ缶を缶底形状に合わせた底金型、円筒状及び凹凸模様をつけた側壁金型で構成された金型に入れ、膨出部材として弾性体を缶内に挿入し、缶外の金型に張り付くまで膨出させる。膨出部材については、ゴムの中実体または薄いゴム袋に油や水を封入し、このゴム袋につながる油圧なしい水圧ポンプ等で加圧して膨出させるものを用いる。また拡張可能なセグメントで構成された金属拡張支持体でもよい。
【００４１】
缶外に金型を使用し内部から加圧して膨出させる加工にあっては、なめらかな曲線が容器に加工できる。このため、缶内より膨出させる膨出部材としては、ゴム等の弾性体や袋状液圧膨出方法の方がデザイン等に自由度をもたせることができる。
【００４２】
ただし上記の方法は膨出部材に耐用性がなく、特に袋状膨出を行う場合には、破損した場合でも、後工程で容器を洗浄しなくても良いように、袋へ入れる膨出液として水を使用したほうが良い。
【００４３】
事前膨出され、硬度がある程度回復した側壁をもつ缶は、円筒状金型より取り出され、つぎの工程Ｇにおいてさらに凹凸模様を施した側壁金型に移し替えて、再度膨出成形を行う。この成形において、径の拡張が行われない部分があっても、焼鈍直後の軟化した側壁部はなく、容器として耐デント特性が向上し、且つ、缶胴強度の確保にも貢献することとなる。
【００４５】
最後に工程Ｈとして、容器として最終的にユーザーに提出するにあたり、缶高さを規格内で管理する必要がある。バルジ加工に先立ち、膨出変形が高さ方向へ影響を及ぼさぬように開口端部６成形を事前に行ったが、それでも僅かながらネック部の材料は側壁の変形に引き込まれる。従って、缶高さを整えるために、最後にフランジ加工を行う必要がある。
【００４６】
このように本発明では、バルジ加工に当たりある程度の強度と伸びを持った事前膨出缶を準備する過程において、不完全な焼鈍を行うのではなく、焼鈍を完結させた後、全体を膨出する手段で加工硬化させることを特徴とし、このようにして、安定して凹凸模様を形成する所望の硬度を得ることがでる。
【００４７】
このようにして製造された容器は、どの部分も焼鈍で軟化されたままの個所がなく、その缶胴部２にあっては、硬度が５５Ｈｖ〜７０Ｈｖとある程度回復した状態にあり、大量生産される時にも、安定的にこれら硬度を維持することができる。さらに缶強度の向上により、薄肉で耐圧力をもったバルジ加工缶を提供することが可能である。
【００４８】
【実施例】
アルミニウム合金３００４−Ｈ１９１材で板厚０．３２ｍｍを使用して、缶胴径φ６０ｍｍ，缶高１３４ｍｍ，壁厚０．１８ｍｍ，缶底形状を図１に示す様な絞りしごき缶を製作し、図２に示す本発明の製造工程に従ってバルジ加工容器を製造した。途中、焼鈍処理後の缶について、膨出直径比別に側壁硬度と缶胴部座屈強度を表１にしめすように測定した。
【００４９】
【表１】

【００５０】
以上の測定結果から、膨出成形により缶胴座屈強度が改善されることが判る。これらの改善は、焼鈍後の冷間加工によるもので、缶胴硬度など安定的に得ることができる。なおテーパー壁Ｂの上部と缶胴側壁下端部の境界部７での座屈強度は表２の通りであった。
【００５１】
【表２】

【００５２】
接地部４から８ｍｍ上方で焼鈍を停止しているもののその熱影響を受け、座屈強度が多少低下した。従って、８ｍｍ以下に焼鈍域を広げることは、更なる強度低下を招くので、この様に焼鈍範囲を限定した。
【００５３】
このようにして製作・焼鈍されたＤＩ缶に図３に示すように事前膨出１０したこの缶の側壁に凸模様１１を形成する再加工を行った。このバルジ加工の結果を表３に示す。
【００５４】
【表３】

【００５５】
膨出直径比１．１２においては、材料破断が見られた。すなわち模様を形成するための材料の伸び代が事前膨出で使われたため、破断に至ったと考えられる。
【００５６】
図４に示す缶は、本発明の製造方法により加工された容器である。この様に複雑な形状の凹凸模様１２の場合、円筒状膨出１０は直径比を１．０３に抑制し、後の凹凸模様を形成するための伸び代を確保する必要がある。
【００５７】
凹凸模様１２を形成することにより、座屈はその模様部分で発生する。座屈強度は殆どの場合、材料が円筒状態の場合より低下する。これら座屈強度は形状によって数値が大きく異なるものの、座屈が凹凸模様の周辺で起きることから、事前膨出によって焼鈍直後の硬度を上げておくことが、これらの座屈強度を向上させるのに役立つ。
【００５８】
即ち表４に示す結果から、事前膨出量を調整することで胴部座屈強度に改善が見られ、壁厚を増加することなく、事前膨出成形の如何により座屈強度を向上したバルジ成形加工が可能である。
【００５９】
【表４】

【００６０】
【発明の効果】
以上説明したように本発明は、ＤＩ缶の凹凸模様を形成するバルジ加工に当たり、ある程度の強度と伸びを持った事前膨出缶を準備する過程において、不完全な焼鈍を行うのではなく、焼鈍を完結させた後、全体を膨出する手段で加工硬化させることを特徴としている。このようにして、安定して凹凸模様を形成する所望の硬度を得ることができ、量産過程の上で均一な硬度を持った良質のバルジ加工品を生産することができる。
【００６１】
さらに、未加工の個所が無いので、必要以上に板厚を厚くすることもなく、薄肉でバルジ加工を施した耐圧容器を提供できるという優れた効果を奏する。
【００６２】
また最終形状により、事前に膨出できる範囲は異なるが、材料伸びの観点から事前膨出量を調整することにより、凹凸加工を行う目安を容易に算定することができる。
【図面の簡単な説明】
【図１】本発明によるＤＩ缶の製造過程における缶の実施の形態例を示す縦断面図である。
【図２】本発明によるＤＩ缶（バルジ成形缶）の製造方法を説明する工程図である。
【図３】本発明に係る実施例のバルジ成形缶断面図である。
【図４】本発明に係る他の実施例のバルジ成形缶を示し、（Ａ）はその縦断面図、（Ｂ）はその凹凸部を示す横断面図である。
【符号の説明】
１アルミニウムＤＩ缶
２缶胴部
３缶底部
４接地部
５ドーム部
６缶開口端部
７境界部
８缶底中央
Ａ焼鈍加熱範囲
Ｂテーパー壁
１０事前膨出（円筒状膨出）
１１凸模様
１２凹凸模様[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to the manufacture of an aluminum drawn and ironed can (hereinafter abbreviated as a DI can) having an irregular pattern on its body, and more particularly, to an aluminum DI can that has been drawn and ironed, which has been subjected to an annealing treatment and then expanded. The present invention relates to an aluminum DI can, which is subjected to work hardening and has an uneven pattern formed on a body by bulging, and a method for manufacturing the same.
[0002]
[Prior art]
In beverage cans, DI cans in which an aluminum plate is drawn into a cylindrical shape and ironed, and a can bottom and a body are integrally formed, are widely used. Manufacturers that sell these containers have developed designs that showcase the image of the product better and motivate users to purchase.
[0003]
Most of them were based on printing on the side wall of the can body.However, the can body was deformed by putting beads on the side wall of the can body, or bulging the surface of the can body so that the product could be differentiated. Attempts have been made to individualize.
[0004]
In bulge processing, the can body can be changed into a free shape, and it is the optimal processing method for the purpose of individualizing products, but when processing the same ironed iron can used for beverage cans In some cases, cracks may occur due to residual stress. For this reason, annealing must be performed once. On the other hand, if annealing is performed, the material is softened and the withstand pressure is reduced. Buckling occurs due to the neck forming force at the time of necking and the lifter pressure at the time of filling the contents.
[0005]
Buckling often occurs at the boundary between the upper portion of the tapered wall toward the ground contact diameter of the bottom portion smaller than the can body diameter and the lower end of the can body side wall. However, if the base plate thickness is sufficiently large, buckling occurs at the can body because the bottom plate thickness increases. Further, when a concavo-convex pattern is formed by bulging, the axial load acts as a concentrated load and buckles at such deformed portions.
[0006]
In a beverage can having a diameter of 211 or 202 using an aluminum alloy 3004-H191 material, the iron can has a hardness of 85 to 95 Hv (Vickers hardness) at the can body and a wall thickness of 0.105 mm when ironed. At this time, the buckling strength at the boundary between the upper portion of the tapered wall and the lower end of the side wall of the can body is about 130 kgf, and the buckling strength of the can body is about 190 kgf. Further, when the bottom of the can has a hardness of 82 to 89 Hv and the plate thickness is 0.28 mm, a withstand pressure of 6 kgf / cm ² or more is secured.
[0007]
When providing an uneven pattern on the can body, these cans are annealed, and bulging is performed on the portions. However, when the bulging process is not the whole bulging but a partial bulging process, portions that have not been bulged remain at a low hardness (40 to 50 Hv) where work hardening does not occur. Significantly impairs the strength of the can.
[0008]
For example, before bulging, the buckling strength at the boundary between the upper portion of the tapered wall and the lower end of the side wall of the can body is about 70 kgf, the buckling strength of the can body is about 100 kgf, and the pressure resistance strength is reduced to 4 kgf / cm ² . It will not function as a pressure vessel.
[0009]
For these reasons, a method of increasing the thickness of the material in order to compensate for the above-mentioned insufficient strength can be considered. However, since the material cost increases and becomes uneconomical, bulging of a metal thin-walled pressure-resistant container has been almost conventionally performed. I didn't.
[0010]
[Problems to be solved by the invention]
However, demand for individualization of beverage cans as containers has been strong, and there has been a strong demand for bulging of thin DI cans that have been drawn and ironed. At present, methods such as bead processing that can be deformed without annealing are being performed. However, bead processing does not have a degree of freedom in design, and has not yet reached the satisfaction of can consumers.
[0011]
According to the technique disclosed in Japanese Patent Publication No. 59-18261, the residual stress during ironing is removed by using a heater for drying when forming a synthetic resin film on the inner surface of the can, but the bulge forming is not performed until the annealing treatment. A way to do that has been proposed.
[0012]
This method is considered to be a method in which the material is completely annealed, that is, a method in which incomplete annealing is performed and a can softened to a certain degree is bulged and formed. Therefore, the setting of the annealing temperature is limited, and it is difficult to soften the annealing to a desired hardness.
[0013]
This causes problems such as insufficient swelling deformation in bulging and sometimes breakage in complicated shapes, and even if a dedicated oven is installed for incomplete annealing, the Adjustment is difficult, and the tensile performance and proof stress of the material vary. Also, in the annealing in an oven, it is difficult to anneal only locally, and the bottom of the can is softened, so that the bottom of the can may be buckled by the internal pressure of the contents.
[0014]
From the above, in the manufacturing stage of a thin DI can, a can having a hardness suitable for bulging can be stably obtained without impairing the performance as a pressure-resistant container, and bulging of a free design is enabled. There has been a demand for an aluminum DI can that can save material.
[0015]
The present invention solves the above-mentioned problem, in particular, by performing an annealing process over a predetermined width of a body portion of a DI can and then expanding and work-hardening the same, thereby providing an uneven pattern at that position. And a method for producing the same.
[0016]
[Means for Solving the Problems]
The manufacturing method of the present invention heats a DI can having a bottom formed by a grounding portion projecting annularly downward and a dome curved inward at a lower portion connected to a can body formed into a cylindrical shape by integral molding. After the treatment, in a method for manufacturing an aluminum DI can in which a swelling member is inserted from the opening end side and swelled to form an uneven pattern on at least a part of the body of the can, an aluminum alloy 3004-H191 material is used. In the DI can, the can body including the upper edge is annealed by high-frequency induction heating from the upper edge of the body having a hardness of 85 to 95 Hv to the can body including the upper edge to have a hardness of 40 to 50 Hv. After the process of coating and printing on the outer surface of the can and applying a synthetic resin coating on the inner surface of the can, the can edge opening end is reduced to a predetermined diameter so as to match the can lid diameter, and further, this Into a cylindrical mold assembled from a bottom mold conforming to the shape of the can bottom and a cylindrical side wall mold that is halved and larger than the original can body diameter to be processed, and expands from the opening end side. By inserting the projecting member, the swelling member presses the can body excluding the reduced diameter portion against the mold, and the diameter ratio is in the range of 1.02 to 1.11 with respect to the original diameter. The whole can body is uniformly and concentrically bulged so as to have a hardness in the range of 52 to 60 Hv, then taken out from the cylindrical side wall mold, and at least a part of the can body has irregularities. A method of manufacturing an aluminum DI can having an uneven pattern on its body, characterized by applying a pattern, setting the hardness of the body of the can to a range of 55 to 70 Hv, and subsequently performing a flange process for winding the lid on the end of the can opening. Is the way.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a longitudinal sectional view showing an embodiment of a DI can in the process of producing an aluminum DI can according to the present invention, and FIG. 2 is a process chart for explaining a method for producing a DI can (bulge molded can).
[0022]
First, the aluminum DI can 1 shown in the step A has a can body 2 formed into a cylindrical shape by integral molding, a can bottom 3 connected to the can body, a grounding portion 4 projecting annularly downward, and an inner portion. It is formed by a dome portion 5 that is curved toward the center.
[0023]
In the method for manufacturing a bulge can according to the present invention, first, only the can body 2 needs to be annealed so that the softening of the can by the annealing in the next step B does not affect the can bottom 3. For annealing, there are an oven method and high-frequency induction heating. In order to partially anneal the can body 2, high-frequency induction heating in which a coil is wound in a ring shape is effective.
[0024]
The heating range A is performed on the can body 2 from the boundary 7 between the can body 2 and the can bottom 3 about 8 mm above the can bottom grounding section 4 to the can opening end 6. The portion 8 mm above the grounding portion 4 at the bottom of the can is a portion formed by the tapered wall B from the can body 2 to the ground diameter portion smaller than the outer diameter of the body for stacking cans. The uneven pattern in the subsequent process is not applied.
[0025]
Further, when an axial load acts on the container, the container buckles at the boundary 7 between the upper portion of the tapered wall B and the lower end of the can body, so that it is necessary to prevent the material in this portion from softening. At the center 8 of the bottom of the can, a heating range of 8 mm above the grounding portion of the can bottom was determined to prevent buckling due to internal pressure.
[0026]
As a result, the pressure resistance of the can bottom 3 and the buckling strength of the boundary 7 between the tapered wall B and the lower end of the side wall of the can have some thermal effects on a normal drawn and ironed can (DI can). The strength is maintained at or above a predetermined level.
[0027]
In the next step C, painting or printing is performed on the outer surface of the can. Before annealing, the ink may be discolored by heat, and after bulging, printing cannot be performed due to unevenness. Therefore, the printing is performed in this step after annealing.
[0028]
Further, in the next step D, it is necessary to form a synthetic resin film on the inner surface of the can by, for example, spraying. In addition to preventing the contents from touching the can directly, the swelling member used for bulge processing expands the synthetic resin film while sliding on the inner surface of the can body, and the swelling member and the inner metal of the can Prevent direct contact.
[0029]
This is because the damage caused by friction with the swelling member becomes large when the metal ground is used, especially when rubber or the like is used as the swelling member, the rubber generates heat or the surface is roughened, and the life of the swelling member is shortened. Become. For this reason, a synthetic resin film is previously formed on the inner surface of the can using a spray or the like.
[0030]
Next, in step E, prior to bulging, the open end 6 of the can is reduced in diameter to a diameter for tightening the lid. The reason is that unless the diameter is reduced before the next bulging molding, the material of the opening end 6 is drawn in when the can body 2 bulges. A phenomenon occurs in which the can height varies.
[0031]
If the can height varies, the length of the flange required at the time of winding will also vary, resulting in poor winding and causing leakage and the like. For this reason, the diameter is reduced in advance, work hardening is applied to the opening end portion 6 and the flow of the material is suppressed, so that problems such as variation in can height can be solved.
[0032]
The can having a reduced diameter at the open end 6 and annealed only the can body 2 is uniformly and concentrically formed in a cylindrical mold having a predetermined diameter ratio in the next step F. It is bulged. The work hardening at this time gives the body 2 a strength again. The given strength is adjusted by the diameter ratio.
[0033]
In general, the hardness of a material is substantially proportional to the tensile strength, and when the tensile strength is σv, the relationship with the Vickers hardness Hv is expressed by the following equation (1) and Equation 1.
[0034]
(Equation 1)
σv = CHv (1)
Here, C is a proportional constant.
[0035]
Therefore, an increase in hardness results in an improvement in tensile strength substantially by the proportion of hardness. For example, if the purpose is to secure the hardness by work hardening of 55 Hv or more, the tensile strength is improved by 25 to 35% with respect to the aluminum hardness (40 to 45 Hv) in the recrystallized state after annealing.
[0036]
If the bulging of the entire can body 2 is excessively performed until the hardness is completely recovered, the irregularities required in the design of the next step cannot be deformed, and the material breaks. Therefore, even if the hardness is not completely recovered, bulging is performed in advance within a range that can take a sufficient amount of deformation to give a concave and convex pattern, and the strength of the can is increased by recovering the hardness reduced by annealing to some extent. Bulge molding.
[0037]
Immediately after annealing of the aluminum alloy 3004-H191 material, the can has an elongation of 21% and a mechanical property of a hardness of 45 Hv. Since this elongation has 21%, the maximum swellable diameter ratio can be approximately up to 1.21.
[0038]
Here, the elongation accompanying the pre-bulging molding is 10%, which can secure a sufficient amount of deformation to give the next uneven pattern, and can prevent the cracks and the wall thickness from becoming extremely thin even in the rapidly changing uneven shape. % Is required, and at most 11% is required to secure this. That is, the maximum diameter ratio at which the can body can be bulged in advance is 1.11.
[0039]
The minimum swelling diameter ratio should be larger than 1.0. However, the proof stress (yield stress causing permanent elongation of 0.2%) is sharply improved in the initial stage of the working, so the working of about 2% must be performed in advance. To improve the strength of the container. For this reason, the minimum swelling diameter ratio was determined to be 1.02.
[0040]
Regarding the method of bulging molding, first, an aluminum DI can is placed in a bottom mold adapted to the shape of the bottom of the can, a mold composed of a cylindrical mold and a side wall mold having an uneven pattern, and an elastic body is formed as a bulging member. Insert into the can and swell until it sticks to the mold outside the can. As the swelling member, a member that is filled with oil or water in a solid rubber body or a thin rubber bag and is swelled by pressurizing with a hydraulic pump or the like connected to the rubber bag with a low hydraulic pressure is used. It may also be a metal expansion support composed of expandable segments.
[0041]
In the process of using a mold outside the can and swelling by pressurizing from inside, a smooth curve can be machined into a container. For this reason, as a swelling member that swells from the inside of the can, an elastic body such as rubber or a bag-like hydraulic swelling method can have more freedom in design and the like.
[0042]
However, the above method is not durable for the swelling member, and particularly when performing bag-like swelling, even if the swelling member is damaged, the swelling liquid to be put into the bag so that the container does not need to be washed in a later process It is better to use water.
[0043]
The can having the side wall which has been pre-expanded and has recovered the hardness to some extent is taken out from the cylindrical mold, and is transferred to the side wall mold further provided with a concavo-convex pattern in the next step G, and the expansion molding is performed again. In this molding, even if there is a portion where the diameter is not expanded, there is no softened side wall immediately after annealing, so that the dent resistance as a container is improved, and it also contributes to securing the strength of the can body. .
[0045]
Finally, as a process H, when finally submitting to a user as a container, it is necessary to manage the can height within the standard. Prior to bulging, the opening end 6 was formed beforehand so that the bulging deformation did not affect the height direction, but the material of the neck portion was still slightly drawn into the deformation of the side wall. Therefore, in order to adjust the height of the can, it is necessary to perform flange processing at the end.
[0046]
Thus, in the present invention, in the process of preparing a pre-expanded can having a certain strength and elongation for bulging, instead of performing incomplete annealing, after completing the annealing, the whole is expanded. It is characterized in that it is work-hardened by means, and in this way, it is possible to obtain a desired hardness for stably forming an uneven pattern.
[0047]
In the container manufactured in this manner, there is no place where any part remains softened by annealing, and the can body 2 has a hardness of 55 Hv to 70 Hv, which has been recovered to some extent, and is mass-produced. Also, these hardnesses can be stably maintained. Further, by improving the strength of the can, it is possible to provide a bulged can having a thin wall and a pressure resistance.
[0048]
【Example】
Using an aluminum alloy 3004-H191 material with a plate thickness of 0.32 mm, a drawn ironing can was manufactured with a can body diameter of φ60 mm, a can height of 134 mm, a wall thickness of 0.18 mm, and a can bottom shape as shown in FIG. A bulge-processed container was manufactured according to the manufacturing process of the present invention shown in FIG. On the way, for the cans after the annealing treatment, the side wall hardness and the can body buckling strength were measured according to the swelling diameter ratio as shown in Table 1.
[0049]
[Table 1]

[0050]
From the above measurement results, it can be seen that the bulging molding improves the can body buckling strength. These improvements are due to cold working after annealing, and can be obtained stably such as can body hardness. The buckling strength at the boundary 7 between the upper portion of the tapered wall B and the lower end of the can body side wall is as shown in Table 2.
[0051]
[Table 2]

[0052]
Although the annealing was stopped 8 mm above the ground contact portion 4, the buckling strength was slightly reduced due to the thermal influence. Therefore, expanding the annealing area to 8 mm or less causes a further decrease in strength, and thus limited the annealing range.
[0053]
The DI can thus manufactured and annealed was reworked to form a convex pattern 11 on the side wall of the can which had been preliminarily expanded 10 as shown in FIG. Table 3 shows the results of this bulge processing.
[0054]
[Table 3]

[0055]
At the bulge diameter ratio of 1.12, material breakage was observed. In other words, it is considered that the breakage was caused because the elongation allowance of the material for forming the pattern was used in advance bulging.
[0056]
The can shown in FIG. 4 is a container processed by the manufacturing method of the present invention. In the case of the concave-convex pattern 12 having such a complicated shape, it is necessary to suppress the diameter ratio of the cylindrical bulge 10 to 1.03 and to secure a sufficient allowance for forming the concave-convex pattern later.
[0057]
By forming the concavo-convex pattern 12, buckling occurs at the pattern portion. Buckling strength is in most cases lower than when the material is cylindrical. Although these buckling strengths vary greatly depending on the shape, since buckling occurs around the uneven pattern, increasing the hardness immediately after annealing by pre-swelling can improve these buckling strengths. Useful.
[0058]
That is, from the results shown in Table 4, the buckling strength of the trunk portion was improved by adjusting the amount of pre-bulging, and the bulge improved the buckling strength by pre-bulging without increasing the wall thickness. Forming is possible.
[0059]
[Table 4]

[0060]
【The invention's effect】
As described above, in the present invention, in the process of preparing a pre-expanded can having a certain degree of strength and elongation, the present invention does not perform incomplete annealing, but performs an After completion of the above, the work is hardened by means of expanding the whole. In this way, it is possible to obtain a desired hardness for stably forming a concavo-convex pattern, and it is possible to produce a high-quality bulge product having a uniform hardness in a mass production process.
[0061]
Furthermore, since there is no unprocessed portion, there is an excellent effect that it is possible to provide a thin and bulged pressure-resistant container without increasing the thickness more than necessary.
[0062]
Although the range in which the swelling can be performed in advance differs depending on the final shape, it is possible to easily calculate a guide for performing the uneven processing by adjusting the amount of the swelling in advance from the viewpoint of material elongation.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an embodiment of a can in the process of manufacturing a DI can according to the present invention.
FIG. 2 is a process diagram illustrating a method for manufacturing a DI can (bulge molded can) according to the present invention.
FIG. 3 is a sectional view of a bulge forming can of an embodiment according to the present invention.
FIGS. 4A and 4B show a bulge can according to another embodiment of the present invention, in which FIG. 4A is a longitudinal sectional view, and FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Aluminum DI can 2 Can body 3 Can bottom 4 Grounding part 5 Dome 6 Can opening end 7 Boundary part 8 Can bottom center A Annealing heating range B Tapered wall 10 Pre-bulge (cylindrical bulge)
11 convex pattern 12 irregular pattern

Claims

A DI can having a bottom formed by a grounding portion projecting annularly downward and a dome curved toward the inside at the lower portion connected to the can body formed into a cylindrical shape by integral molding, and then heated at the open end, A method for manufacturing an aluminum DI can in which a swelling member is inserted from the side and swelled to form an uneven pattern on at least a part of the body of the can.
Of DI cans made of aluminum alloy 3004-H191 material, the can body comprising a top end edge portion is annealed by high-frequency induction heating the can barrel portion of the can bottom front from the upper edge portion of the body having a hardness 85~95Hv Softened to a hardness of 40-50 Hv ,
Next, after coating and printing on the outer surface of the can and applying a synthetic resin film on the inner surface of the can, the opening end of the can edge portion is reduced to a predetermined diameter so as to match the can lid diameter ,
Further, the can is pushed into a cylindrical mold assembled by a bottom mold adapted to the shape of the bottom of the can and a cylindrical side wall mold which is half and larger than the diameter of the original can body to be processed. A swelling member is inserted from the part side, and the swelling member presses the can body excluding the reduced diameter portion against the mold, and the diameter ratio is 1.02 to 1.11 with respect to the original diameter. In the range, after the entire body of the can is uniformly and concentrically swelled so that the hardness is in the range of 52 to 60 Hv , it is taken out from the cylindrical side wall mold ,
Further , at least a part of the body of the can is provided with a concavo-convex pattern, and the hardness of the body of the can is set to a range of 55 to 70 Hv .
A method for producing an aluminum DI can having a concavo-convex pattern on a body portion, wherein flange processing for successively winding a lid is performed on an end of the can opening .