JP3582319B2

JP3582319B2 - Manufacturing method of seamless cans

Info

Publication number: JP3582319B2
Application number: JP23188197A
Authority: JP
Inventors: 則人佐伯
Original assignee: Toyo Seikan Kaisha Ltd
Current assignee: Toyo Seikan Kaisha Ltd
Priority date: 1997-08-14
Filing date: 1997-08-14
Publication date: 2004-10-27
Anticipated expiration: 2017-08-14
Also published as: JPH1157906A

Description

【０００１】
【発明の属する技術分野】
本発明は、再絞りーしごき加工法による、有機被膜で被覆されたシームレス缶の製造方法に関する。
【０００２】
【従来の技術】
特開平７−２７５９６１号公報に、内外面が有機被膜で被覆された金属カップに皺押さえ具を装入し、皺押さえ具で金属カップ底部をダイ平面部に対し押さえつつ、ポンチをダイのキャビティ内に前進させて、金属カップの側壁部外面を、ダイ平面部、ダイの曲率半径の小さい加工コーナに密接させながら、加工コーナにおける曲げ延伸により側壁部の板厚を減少し、さらにポンチと、加工コーナの前端部、または前端部より前方にあるしごき部との協同によりしごき加工を行なって側壁部の板厚をより減少して細長いシームレス缶を製造する方法、すなわち同一工程で行なう薄肉化再絞りーしごき加工法が提案されている。
しかしながら上記公報に記載の薄肉化再絞りーしごき加工法では、側壁部を薄くしようとすると、側壁部が破断し易く、そのため製造されるシームレス缶の側壁部の薄肉化、従ってシームレス缶の軽量化によるコスト低減が十分でないという問題があった。
【０００３】
【発明が解決しようとする課題】
本発明は、側壁部を薄くしても側壁部の破断が起こり難い、改善された、同一工程で行なう薄肉化再絞りーしごき加工法によるシームレス缶の製造方法を提供することを目的とする。
【０００４】
【課題を解決するための手段】
請求項１に係る発明のシームレス缶の製造方法は、
内外面が有機被膜で被覆された絞り成形体に皺押さえ具を装入し、皺押さえ具で絞り成形体の底部をダイ平面部に対し押さえつつ、ポンチをダイのキャビティ内に前進させて、絞り成形体の側壁部外面を、ダイ平面部、ダイの曲率半径の小さい加工コーナに密接させながら、加工コーナにおける曲げ延伸により側壁部の板厚を減少し、さらにポンチと、加工コーナの前端部、または前端部より前方にあるしごき部との協同によりしごき加工を行なって側壁部の板厚をより減少して絞り成形体より細長い第１のシームレス缶を製造する方法において、
絞り成形体の側壁部肉厚のしごき加工後の減厚量が高さ方向に等しくなるように、
絞り成形体の側壁部の上方に向かって次第に肉厚が大きくなる高さ方向肉厚分布に対応した、後方に向って内側に０度１分〜０度３０分で傾斜するテーパ部を、ポンチの円筒形部の上端に接続して設けたポンチを用いて加工することを特徴とする。
しごき部が加工コーナの前端部にある時は、しごき部は円形線よりなる。加工コーナの前端部より前方にあるしごき部は、通常短円筒形である。
【０００５】
平坦なブランクから通常の絞り成形を行なう際に、絞り成形体の側壁部となるべき部分は、周方向に圧縮されながらダイキャビティ内に入っていくことによって形成される。また側壁部と底部の間の湾曲部は比較的高い延伸力を受ける。そのため絞り成形体の湾曲部はブランクの厚さよりやや薄くなるが、側壁部は下方から上方に向って次第に厚くなり、端面部の厚さはブランクの厚さよりかなり厚くなることが知られている。例えば端面部の厚さをｔｍ、ブランクの厚さをｔ０、絞り比をＲとすると、ｔｍは、ｔ０にＲの平方根を掛けた値に等しいとされている（「図解プレス加工辞典」、宮川松男編、第１１８〜１１９頁、昭和５１年１０月３０日、日刊工業新聞社発行）。なおこの関係式は、極く軟らかい深絞り用鋼板（ロックウエル３０Ｔ硬度が約５０）のブランクについて得られたものと思われる。
そのため従来の、全長が実質的に円筒形のポンチを用いて、絞り成形体の薄肉化再絞りーしごき加工を行なうと、形成されるシームレス缶の側壁部の肉厚が高さ方向に実質的に等しくなるため、減厚量、特にしごき量が上方になる程、すなわち開口端に近づく程大きくなる。従ってしごき量が破断上限に達し易く、成形中の側壁部の破断が起こり易くなるものと思われる。
【０００６】
請求項１に係わる発明の場合、ポンチに、減厚量が高さ方向に実質的に等しくなるように、絞り成形体の側壁部の高さ方向肉厚分布に対応した、後方に向って僅かに細くなるテーパ部が設けられている。そのため同じ再絞り比で、同じ高さが得られるようにした薄肉化再絞りーしごき加工で比較した場合、従来のポンチを使用した場合のように側壁部の減厚量が上方部において高くなることがない。従って側壁部の破断を起こすことなく、側壁部を薄くすることができる。
【０００７】
請求項２に係る発明は、被成形体を、絞り成形体でなく、請求項１記載の方法で形成された第１のシームレス缶として、第１のシームレス缶に、請求項１記載の方法を１回ないし複数回行なって、第１のシームレス缶より細長い第２のシームレス缶を製造する方法である。
第１のシームレス缶を形成するポンチに、後方に向って僅かに細くなるテーパ部が付されているので、第１のシームレス缶の側壁部も、少なくとも上方部が上方に向って肉厚が大きくなっている。従って段落番号０００６に記載したのと同様の作用で、破断することなく、側壁部がより薄く、かつ少なくとも上方部が上方に向って肉厚が大きくなっている、細長い第２のシームレス缶を製造することができる。
請求項１記載の方法を複数回行なう場合についても、各回毎に同様のことがいえる。
【０００８】
請求項３に係わる発明のシームレス缶の製造方法は、
第１のシームレス缶に皺押さえ具を装入し、皺押さえ具で第１のシームレス缶の底部をダイ平面部に対し押さえつつ、ポンチをダイのキャビティ内に前進させて、第１のシームレス缶の側壁部外面を、ダイ平面部、ダイの曲率半径の小さい加工コーナに密接させながら、加工コーナにおける曲げ延伸により側壁部の板厚を減少し、さらにポンチと、加工コーナの前端部、または前端部より前方にある第１のしごき部との協同によりしごき加工を行なって側壁部の板厚をより減少し、直ちに第１のしごき部に近接してその前方に設けられた第２のしごき部との協同によりしごき加工を行なって側壁部の板厚をさらに減少して、第１のシームレス缶より細長い第３のシームレス缶を製造する方法において、第１のシームレス缶の側壁部肉厚の曲げ延伸−しごき加工後の減厚量が高さ方向に等しくなるように、第１のシームレス缶の側壁部の上方に向かって次第に肉厚が大きくなる高さ方向肉厚分布に対応した、後方に向って内側に０度１分〜０度３０分で傾斜するテーパ部を、
ポンチの円筒形部の上端に接続して設けたポンチを用いて加工することを特徴とする。
【０００９】
段落番号０００７に記載したように、第１のシームレス缶の側壁部は上方に向って肉厚が大きくなっている。従って段落番号０００６に記載したのと同様の作用で、破断することなく、側壁部がより薄く、細長い第３のシームレス缶を製造することができる。
成形が終了した時点で、第１のしごき部と第２のしごき部の間の側壁部部分（開口端部に当たる）は、第２のしごき部によるしごき加工を受けない。従ってこの部分（開口端部）はその下方の側壁部部分より厚く（図１０の曲線２参照）、ネックイン加工やフランジ加工の際の皺や割れ等の成形不良が発生し難い。
【００１０】
請求項４に係わる発明のシームレス缶の製造方法は、
第２のシームレス缶に皺押さえ具を装入し、皺押さえ具で第２のシームレス缶の底部をダイ平面部に対し押さえつつ、ポンチをダイのキャビティ内に前進させて、第２のシームレス缶の側壁部外面を、ダイ平面部、ダイの曲率半径の小さい加工コーナに密接させながら、加工コーナにおける曲げ延伸により側壁部の板厚を減少し、さらにポンチと、加工コーナの前端部、または前端部より前方にある第１のしごき部との協同によりしごき加工を行なって側壁部の板厚をより減少し、直ちに第１のしごき部に近接してその前方に設けられた第２のしごき部との協同によりしごき加工を行なって側壁部の板厚をさらに減少して、第２のシームレス缶より細長い第４のシームレス缶を製造する方法において、第２のシームレス缶の側壁部肉厚の曲げ延伸−しごき加工後の減厚量が高さ方向に等しくなるように、第２のシームレス缶の側壁部の上方に向かって次第に肉厚が大きくなる
高さ方向肉厚分布に対応した、後方に向って内側に０度１分〜０度３０分で傾斜するテーパ部を、
ポンチの円筒形部の上端に接続して設けたポンチを用いて加工することを特徴とする。
段落番号０００７に記載したように、第２のシームレス缶の側壁部は、少なくとも上方部が上方に向って肉厚が大きくなっている。従って段落番号０００９に記載したように、破断することなく、側壁部がより薄く、細長い第４のシームレス缶を製造することができる。また成形が終了した時点における第１のしごき部と第２のしごき部の間の側壁部部分（開口端部に当たる）は、その下方の側壁部部分より厚く、ネックイン加工やフランジ加工の際の皺や割れ等の成形不良が発生し難い。
【００１１】
請求項５に係わる発明のシームレス缶の製造方法は、
絞り成形体に皺押さえ具を装入し、皺押さえ具で絞り成形体の底部をダイ平面部に対し押さえつつ、ポンチをダイのキャビティ内に前進させて、絞り成形体の側壁部外面を、ダイ平面部、ダイの曲率半径の小さい加工コーナに密接させながら、加工コーナにおける曲げ延伸により側壁部の板厚を減少し、さらにポンチと、加工コーナの前端部、または前端部より前方にある第１のしごき部との協同によりしごき加工を行なって側壁部の板厚をより減少し、直ちに第１のしごき部に近接してその前方に設けられた第２のしごき部との協同によりしごき加工を行なって側壁部の板厚をさらに減少して、絞り成形体より細長い第５のシームレス缶を製造する方法において、絞り成形体の側壁部肉厚の曲げ延伸−しごき加工後の減厚量が高さ方向に等しくなるように、絞り成形体の側壁部の上方に向かって次第に肉厚が大きくなる高さ方向肉厚分布に対応した、後方に向って内側に０度１分〜０度３０分で傾斜するテーパ部を、ポンチの円筒形部の上端に接続して設けたポンチを用いて加工することを特徴とする。
絞り成形体は、側壁部が上方に向って肉厚が大きくなっている。従って段落番号０００９に記載したように、破断することなく、側壁部がより薄く、細長い第５のシームレス缶を製造することができる。また成形が終了した時点における第１のしごき部と第２のしごき部の間の側壁部部分（開口端部に当たる）は、その下方の側壁部部分より厚く、ネックイン加工やフランジ加工の際の皺や割れ等の成形不良が発生し難い。
【００１３】
【発明の実施の形態】
図１に示すブランク１は、缶用金属板２の両面に薄い有機被膜３、例えば熱可塑性ポリエステル系フィルムが熱接着により被覆されたもので、円形で、全厚はｔ０である。
図２に示す絞り成形体４は、ブランク１より、比較的大きい曲率半径を有する加工コーナのダイを用いた通常の絞り成形法によって形成された絞り成形体である。絞り成形体４の底部４ａの厚さは、ブランク１の厚さｔ０に実質的に等しい。絞り成形体４の湾曲部４ｂの最小肉厚はｔ０より僅かに小さく、側壁部４ｃの肉厚は上方に向って次第に大きくなり、端面部４ｃ１において最大になる（図８の曲線１参照）。
【００１４】
図３は、絞り成形体４を薄肉化再絞りーしごき加工して、中間シームレス缶２５を形成している途中の状態を示す。１１はダイ、１２はダイ１１を支持するダイ支持部である。２０はポンチプレート（図示されない）にポンチ支持筒２２を介して着設された、ダイ１１と同軸のポンチ、２１は僅かな間隙１９をあけてポンチ２０を包囲して、ポンチ２０と同軸に上部ダイシュー（図示されない）に着設された皺押さえ具である。
ダイ１１は、上面である平坦な環状平面部１３、環状平面部１３に接続する曲率半径Ｒｄ１の小さい加工コーナ１４、加工コーナ１４の下端１４ａに連接する、逆円錐台形のアプローチ部１５、アプローチ部１５に曲率部またはシャープコーナ１６を介して接続する短円筒形のしごき部１７および逃げ面１８を備えている。加工コーナ１４で再絞り加工を行なう際に薄肉化を実現するために、加工コーナ１４の曲率半径Ｒｄ１は、（１〜５）ｘｔ０（ｔ０はブランクの板厚）、より好ましくは（１〜２．９）ｘｔ０であることが望ましい。
【００１５】
ポンチ２０は下方より、平坦でエア吹き出し孔の開口部（図示されない）を有する底面２０ａ、底面２０ａに接続する湾曲部２０ｂ、湾曲部２０ｂの上端に接続する僅かな高さの逆円錐台形部２０ｃ、逆円錐台形部２０ｃの上端に接続し、全高のほぼ半分を占める円筒形部２０ｄを備えている。ポンチ２０はさらに、円筒形部２０ｄの上端２０ｄ１に接続し、軸線に対する僅かなテーパ角βで内側上方に傾斜するテーパ部２０ｅを備えている。ポンチ２０の高さは、形成される中間シームレス缶２５の高さより若干大きい。
逆円錐台形部２０ｃは、加工の初期におけるしごき量を軽減するために設けられている。しごき加工の初期においては、前工程の底部すなわち元板厚部分をしごき加工することになるので、この部分のしごき量を軽減するためにテーパ部を有する逆円錐台形部２０ｃが設けられている。逆円錐台形部２０ｃの高さＨ１および中心軸に対する傾斜角αは、絞り比、元板厚としごきクリアランス（しごき量）によって決められる（図９参照）。通常、高さＨ１は２〜１０ｍｍ、傾斜角αは０度１０分〜１度３０分程度であるが、この限りでない。
【００１６】
中間シームレス缶２５の側壁部２５ａの高さ方向或る位置における厚さは、ダイ１１のしごき部１７とポンチ２０間のクリアランスによって決まる。クリアランスは、当該位置におけるポンチ２０の直径をｄ、しごき部の内径をＤとすると、（Ｄーｄ）／２である。
中間シームレス缶２５の側壁部２５ａのほぼ下半部は、絞り成形体４の底部４ａのポンチ底面２０ａと接触する部分の外側部、湾曲部４ｂおよび側壁部４ｃの下方部よりなる（図２参照）が、これらの部分の厚さはほぼ等しい。従ってこれらの部分は、ポンチ２０の円筒形部２０ｄとしごき部１７によってしごかれるが、しごき後の肉厚減少量すなわち減厚量（しごき後の或る部分に対応する絞り成形体４の側壁部４ｃの部分の肉厚から、しごき後上記部分の肉厚を引いた値）は実質的に同じである。絞り成形体４の上方部は上方に向って厚くなるが、この厚くなる割合に見合ってテーパ部２０ｅのテーパ角βを定めることによって、この部分のしごき後の減厚量を実質的に同じに、従って側壁部全体の減厚量を実質的に等しくすることができる。テーパ角βは、通常０度１分〜０度３０分、より好ましくは０度２分〜０度１５分である。
【００１７】
円筒形部２０ｄの高さＨｓ１と、テーパ部２０ｅのテーパ角βは、中間シームレス缶２５の側壁部２５ａが形成される前後の体積計算（体積一定の条件を入れた）と、減厚量計算（減厚量一定の条件を入れた）を、例えばＣＡＤを用いて行なうことによっておよその値が求められる。正確な値は、高さＨｓ１とテーパ角βの種々の組み合わせによる実験を行なって、「減厚量が実質的に一定」が得られる組み合わせを見つけることによって定められる。
【００１８】
以上の工具により中間シームレス缶２５は、次のようにして形成される。
絞り成形体４に皺押さえ具２１を装入し、皺押さえ具２１で絞り成形体４の底部４ａの周辺部をダイ１１の環状平面部１３に対して押圧しながら、ポンチ２０をダイ１１のキャビティ内に前進させて、絞り成形体４の側壁部４ｃ外面を、環状平面部１３およびダイ１１の曲率半径の小さい加工コーナ１４に密接させながら、加工コーナ１４における曲げ延伸により側壁部４ｃの板厚を減少させる。直ちにポンチ２０としごき部１７との協同により、板厚が減少した側壁部４ｃをしごき加工して肉厚を更に減少させ、フランジ部（後述の２５ｂ）が残る時点で成形を終了する。このようにして絞り成形体４を、それより側壁部（２５ａ）が薄く、細く、かつ高い中間シームレス缶２５に形成する。
図４は成形が終了して、フランジ部２５ｂが付いた中間シームレス缶２５が形成された状態を示す。中間シームレス缶２５の側壁部２５ａのほぼ下半を占める下方部２５ａ１の肉厚は実質的に均一である。側壁部２５ａのほぼ上半を占める上方部２５ａ２の肉厚は上方に向って直線的に次第に大きくなっている（図８の曲線２参照）。なお２５ａ３は、下方部２５ａ１と上方部２５ａ２との境界部である。
【００１９】
図５は、中間シームレス缶２５をさらに薄肉化再絞りーしごき加工して、より細く、かつ高いシームレス缶２７を形成中の状態を示す。
図５において、３１は薄肉化再絞り−しごきダイ、３２はしごきリングダイであり、しごきリングダイ３２は支持体４３によって支持されており、薄肉化再絞り−しごきダイ３１はしごきリングダイ３２の上に互いに同軸に取り付けられている。しごきリングダイ３２の内径は、再絞り−しごきダイ３１の内径より小さい。
４５は再絞り−しごきダイ３１およびしごきリングダイ３２と同軸のポンチであり、４６は僅かな間隙３０をあけてポンチ４５を包囲して、ポンチ４５と同軸に上部ダイシュー（図示されない）に着設された皺押さえ具である。
ダイ３１は、上面である平坦な環状平面部３３、環状平面部３３に接続する曲率半径Ｒｄ２の小さい加工コーナ３４、加工コーナ３４の下端３４ａに連接する逆円錐台形のアプローチ部３５、アプローチ部３５に曲率部またはシャープコーナ３６を介して接続する短円筒形の上しごき部３７および逃げ面３８を備えている。加工コーナ３４で絞り加工を行なう際に薄肉化を実現するために、加工コーナ３４の曲率半径Ｒｄ２は、（１〜５）ｘｔ０（ｔ０はブランクの板厚）、より好ましくは（１〜２．９）ｘｔ０であることが望ましい。
ダイ３２は、逆円錐台形のアプローチ部３９、アプローチ部３９に曲率部またはシャープコーナ４０を介して接続する短円筒形の下しごき部４１および逃げ面４２を備えている。
【００２０】
ポンチ４５は下方より、平坦でエア吹き出し孔の開口部（図示されない）を有する底面４５ａ、底面４５ａに接続する湾曲部４５ｂ、湾曲部４５ｂの上端に接続する僅かな高さの逆円錐台形部４５ｃ、逆円錐台形部４５ｃの上端に接続し、全高のほぼ半分を占める円筒形部４５ｄを備えている。ポンチ４５はさらに、円筒形部４５ｄの上端４５ｄ１に接続し、軸線に対する僅かなテーパ角ρで内側上方に傾斜するテーパ部４５ｅを備えている。ポンチ４５の高さは、形成されるシームレス缶２７の全高より若干大きい。
逆円錐台形部４５ｃの高さＨ２および中心軸に対する傾斜角θは、絞り比、元板厚としごきクリアランス（しごき量）によって決められる（図１１参照）。通常、高さＨ２は２〜１０ｍｍ、傾斜角θは０度１０分〜１度３０分程度であるが、この限りでない。
【００２１】
シームレス缶２７の側壁部２７ａの厚さは、前記のようにダイの上しごき部３７および下しごき部４１とポンチ４５間のクリアランスによって決まる。シームレス缶２７の側壁部２７ａのほぼ下半部は、中間シームレス缶２５の底部２５ｃのポンチ底面４５ａと接触する部分の外側部、湾曲部２５ｄおよび側壁部２５ａの下方部２５ａ１よりなる（図４参照）。前二者は、厚さは下方部２５ａ１より大きいが、クリアランスが比較的大きいポンチ先端の逆円錐台形部４５ｃと下しごき部４１によってしごかれる。側壁部２５ａの下方部２５ａ１はポンチ４５の円筒形部４５ｄと下しごき部４１によってしごかれるが、この部分の厚さはほぼ均一である。従って側壁部２７ａのほぼ下半部のしごき後の減厚量はほぼ均等である。
【００２２】
中間シームレス缶２５の上方部２５ａ２は上方に向って厚くなるが、この厚くなる割合に見合ってテーパ部４５ｅのテーパ角ρを定めることによって、この部分のしごきによる減厚量を実質的に同じに、従って側壁部２５ａ全体の減厚量を実質的に等しくすることができる。テーパ角ρは、通常０度１分〜０度３０分、より好ましくは０度２分〜０度１５分である。
【００２３】
円筒形部４５ｄの高さＨｓ２と、テーパ部４５ｅのテーパ角ρは、シームレス缶２７の側壁部２７ａが形成される前後の体積計算（体積一定の条件を入れた）と、減厚量計算（減厚量一定の条件を入れた）を、例えばＣＡＤを用いて行なうことによっておよその値が求められる。正確な値は、高さＨｓ２とテーパ角ρの種々の組み合わせによる実験を行なって、「減厚量が実質的に一定」が得られる組み合わせを見つけることによって定められる。
【００２４】
以上の工具によりシームレス缶２７は、次のようにして形成される。
中間シームレス缶２５に皺押さえ具４６を装入し、皺押さえ具４６で中間シームレス缶２５の底部２５ｃの周辺部をダイ３１の環状平面部３３に対して押圧しながら、ポンチ４５をダイ３１、３２のキャビティ内に前進させて、中間シームレス缶２５の側壁部２５ａ外面を、環状平面部３３およびダイ３１の曲率半径の小さい加工コーナ３４に密接させながら、加工コーナ３４における曲げ延伸により側壁部２５ａの板厚を減少させる。
直ちにポンチ４５と上しごき部３７および下しごき部４１との協同により、板厚が減少した側壁部２５ａをしごき加工して肉厚を更に減少させ、フランジ部（後述の２７ｂ）が残る時点で成形を終了する。この場合、成形が終了した時点で、下しごき部４１としごき３７の間にある側壁部２５ａの部分である開口端部２７ｘは下しごき部４１によるしごき加工を受けない。従って開口端部２７ｘは、減厚された側壁部２５ａ（後述の２７ａ）の他の部分に比べて特に厚い（図１０の曲線２の（２７ｘ）参照）。このようにして中間シームレス缶２５を、それより側壁部２７ａが薄く、細く、かつ高いシームレス缶２７に形成する。
【００２５】
図６は成形が終了して、フランジ部２７ａが付いたシームレス缶２７が形成された状態を示す。シームレス缶２７の側壁部２７ａの下方部２７ａ１の肉厚は実質的に均一であり、上方部２７ａ２の肉厚は上方に向って次第に大きくなった後、下しごき部４１に接触する部分から上の開口端部２７ｘは一段と大きくなっている。なお２７ａ３は、下方部２７ａ１と上方部２７ａ２との境界部である。
【００２６】
シームレス缶２７は、次の工程で底部２７ｃをドーミング加工された後、工具から取り出される。その後、側壁部２７ａをフランジ部２７ｂ下方から切断され、開口端部２７ｘをネックイン加工およびフランジ加工され、例えば図７に示すような、フランジ部２８ａ、ネックイン部２８ｂ、側壁部２８ｃ、チャイム部２８ｄおよび内側に凹んだドーム部２８を有する、缶詰等に用いられるシームレス缶２８に形成される。
開口端部２７ｘは、外面が円筒形で、内面が僅かなテーパ角ρの円錐台形である。そのため上記切断後の開口端部２７ｘの端面が側壁部２７ａの中で最も厚い。従って側壁部２７ａの主部の肉厚を薄くしても、この端面は比較的厚いので、ネックイン加工時の皺やフランジ加工時の割れが起こり難い。
【００２７】
図示は省略したが、図３に示すタイプのポンチとダイを用いて、中間シームレス缶２５を薄肉化再絞りーしごき加工して、中間シームレス缶２５より細長く、かつ側壁部がより薄く、その減厚量が全高に亘り実質的に等しいシームレス缶を製造することができる。このシームレス缶を、さらに図３に示すタイプのポンチとダイを用いて１回もしくは複数回薄肉化再絞りーしごき加工して、より細長く、かつ側壁部がより薄く、その減厚量が全高に亘り実質的に等しい別のシームレス缶を製造することができる。
図示は省略したが、上記のようにして製造したシームレス缶を、図５に示すタイプのポンチとダイを用いて、薄肉化再絞りーしごき加工して、より細長く、かつ側壁部がより薄く、その減厚量が全高に亘り実質的に等しい、かつ比較的肉厚の開口端部を有するシームレス缶を製造することができる。
さらに図示は省略したが、絞り成形体４を、図５に示すタイプのポンチとダイを用いて、薄肉化再絞りーしごき加工して、より細長く、かつ側壁部がより薄く、その減厚量が全高に亘り実質的に等しい、かつ比較的肉厚の開口端部を有するシームレス缶を製造することができる。
【００２８】
【実施例】
厚さ０．１８０ｍｍ、ＤＲー６Ｍ（２回冷延鋼板：ロックウエル３０Ｔ硬度：６６〜７２）のティンフリースチール２（電解クロム酸処理鋼板）の、缶内面となるべき面に厚さ０．０２５ｍｍの、缶外面となるべき面に厚さ０．０１７ｍｍの二軸延伸エチレンテレフタレート／エチレンイソフタレート共重合体（モル比：８８／１２，融点２３０℃，ガラス転移温度Ｔｇ：７０℃）フィルム３を熱接着することにより作製されたラミネート鋼板（総厚さｔ０＝０．２２２ｍｍ）に、パラフィンワックス（融点Ｔｍ：６０℃）を両面に各約５０ｍｇ／ｍ^２を塗布した。
このラミネート鋼板を、絞り成形機（図示されない）により、直径１５４ｍｍの円形ブランク１に打ち抜き、ブランク１を加工コーナの曲率半径が０．８ｍｍの通常のダイを用いて、絞り比１．６２で絞り加工することにより、平均高さＨ０が４３ｍｍ、内径Ｄ０が９５ｍｍの絞り成形体４（図２）を作製した。絞り成形体４の側壁部４ｃの厚さと底部４ａ内面からの高さとの関係を図８の曲線１に示す。
【００２９】
絞り成形体４を、加工コーナ１４の曲率半径Ｒｄ１が０．５０ｍｍ（Ｒｄ１／ｔ０＝２．２５）、アプローチ部１５の中心軸に対する上方傾斜角が５度、１６がシャープコーナ、しごき部１７の内径Ｄ１が８１．９７ｍｍのダイ１１、および湾曲部２０ｂの曲率半径が５ｍｍ、逆円筒形部２０ｃの高さＨ１が６ｍｍ、傾斜角αが１度、円筒形部２０ｄの直径ｄ１が８１．７０ｍｍ、高さＨｓ１が２３ｍｍ、テーパ部２０ｅの高さが３６ｍｍ、テーパ角βが０度４分のポンチ２０（表面温度を５０℃に保持した）を備える図３に示すタイプの工具を用いて、絞り比１．１６で薄肉化再絞り−しごき加工を行ない、高さが７２ｍｍの中間シームレス缶２５を作製した。
中間シームレス缶２５の側壁部２５ａの厚さと底部２５ｃ内面からの高さとの関係を図８の曲線２に示す。曲線２において、底部内面よりの高さが約４〜５ｍｍの位置の箇所において板厚減少が無いのは、図９に示すように、逆円筒形部２０ｃの下端部近傍では、しごき部１７とポンチ２０とのクリアランスが、当該位置における絞り成形体の側壁部４ｃの肉厚より大きいためである。
曲線１と曲線２との対応する部分（例えば点ａと点ｂ、または点ｃと点ｄ）の厚さの差から、対応する部分における減厚量（ｍｍ）が求められる。ポンチストローク（ポンチ底面２０ａがダイ１１の平面部１３に達した時のストロークを０ｍｍとする）と減厚量との関係を曲線３に示す。減厚量は、高さが約４〜５ｍｍの位置で０であるのを除いて約０．０６ｍｍと実質的に一定である。なお曲線１における点ｃと点ｅの間の部分はフランジ部２５ｂである。
【００３０】
比較のため、テーパ部２０ｅを有しない、逆円錐台形部２０ｃを除いては全長が円筒形のポンチを用いた点以外は、前記と同様にして、絞り成形体４を再絞りーしごき加工したが、ポンチの底面から約６５ｍｍの位置で側壁部が破断して成形が不可能であった。破断位置の減厚量は約０．０９ｍｍであった。
【００３１】
段落番号００２９に記載のようにして作製した、中間シームレス缶２５を図５に示すタイプの工具を用いて、薄肉化再絞りーしごき加工して高さが１２７ｍｍのシームレス缶２７を作製した。
この場合、加工コーナ３４の曲率半径Ｒｄ２が０．７０ｍｍ（Ｒｄ２／ｔ０＝３．１５）、上しごき部３７の内径Ｄ２が６６．３２ｍｍのダイ３１、および下しごき部４１の内径Ｄ３が６６．２３ｍｍで、ダイ３１の上しごき部３７の上端からダイ３２の下しごき部４１の上端までの垂直高さが１８．５ｍｍであった。アプローチ部３５の中心軸に対する上方傾斜角が４度、アプローチ部３９の中心軸に対する上方傾斜角が２度、３６および４０はシャープコーナであった。
ポンチ４５の湾曲部４５ｂの曲率半径が５ｍｍ、逆円筒形部４５ｃの高さＨ２が１５ｍｍ、傾斜角θが０度３５分、円筒形部４５ｄの直径ｄ２が６６．０５ｍｍ、高さＨｓ２が５５ｍｍ、テーパ部４５ｅの高さが４２ｍｍ、テーパ角ρが０度３分２０秒であった。ポンチ４５の表面温度を５０℃に保持した。
【００３２】
シームレス缶２７の側壁部２７ａの厚さと底部２７ｃ内面からの高さとの関係を図１０の曲線２に示す。中間シームレス缶２５の側壁部２５ａの厚さと底部２５ｃ内面からの高さとの関係も図１０の曲線１に示す。
曲線１と曲線２との対応する部分（例えば点ｆと点ｇ、または点ｈと点ｉ）の厚さの差から、対応する部分における減厚量（ｍｍ）が求められる。ポンチストローク（ポンチ底面４５ａがダイ３１の平面部３３に達した時のストロークを０ｍｍとする）と減厚量との関係を曲線３に示す。減厚量は、高さが４０ｍｍに至るまでの位置においては比較的小さい範囲内で変動する。これは図１１に示すように、逆円錐台形部４５ｃのため、上しごき部３７のみによってしごかれるからである。減厚量は、高さが４０ｍｍを越えた位置では約０．０４ｍｍであり、ほぼ一定である。なお点ｊと点ｌの間の部分はフランジ部２５ｂを、点ｋと点ｍの間の部分はフランジ部２７ｂを示す。
【００３３】
比較のため、テーパ部４５ｅを有しない、逆円錐台形部４５ｃを除いては全長が円筒形のポンチを用いた点以外は、前記と同様にして、中間シームレス缶２５を薄肉化再絞りーしごき加工したが、ポンチの底面から約１０５ｍｍの位置で側壁部が破断して成形が不可能であった。破断位置の減厚量は約０．０６ｍｍであった。
【００３４】
【発明の効果】
請求項１、２に係わる発明の、同一工程で行なう薄肉化再絞りーしごき加工法によるシームレス缶の製造方法は、側壁部を薄くしても側壁部の破断が起こり難いという効果を奏する。請求項３、４、５に係わる発明は、上記効果に加えて、形成された開口端部にネックインする時の皺やフランジ加工する時の割れ等が発生し難いという利点を有する。
【図面の簡単な説明】
【図１】図２の絞り成形体を形成するためのブランクの例の縦断面図である。
【図２】図２は、絞り成形体の例の縦断面図である。
【図３】図３は、図２の絞り成形体を薄肉化再絞りーしごき加工している途中の状態を示す要部縦断面図である。
【図４】図４は、図３に示す薄肉化再絞りーしごき加工が終了して、中間シームレス缶が形成された時点の状態を示す要部縦断面図である。
【図５】図５は、図２の絞り成形体より形成された中間シームレス缶を薄肉化再絞りーしごき加工している途中の状態を示す要部縦断面図である。
【図６】図６は、図５に示す薄肉化再絞りーしごき加工が終了してシームレス缶が形成された時点の状態を示す要部縦断面図である。
【図７】図７は、図６のシームレス缶に、ドーミング加工、ネックイン加工およびフランジ加工を施してなる缶体の例の縦断面図である。
【図８】図８は、図３および図４に示す成形における、絞り成形体および中間シームレス缶の側壁部の厚さと、それぞれの缶底部内面からの高さとの関係、ならびに成形時における側壁部の減厚量とポンチストロークとの関係を示す線図である。
【図９】図９は、図３に示す成形の初期における状態を示す要部縦断面図である。
【図１０】図１０は、図５および図６に示す成形における、中間シームレス缶およびシームレス缶の側壁部の厚さと、それぞれの缶底部内面からの高さとの関係、ならびに成形時における側壁部の減厚量とポンチストロークとの関係を示す線図である。
【図１１】図１１は、図５に示す成形の初期における状態を示す要部縦断面図である。
【符号の説明】
３有機被膜
４絞り成形体
４ａ底部
４ｃ側壁部
１１ダイ
１３環状平面部（ダイ平面部）
１４加工コーナ
１４ａ下端（前端部）
１７しごき部
２０ポンチ
２０ｄ円筒形部
２０ｅテーパ部
２１皺押え具
２５中間シームレス缶（第１のシームレス缶）
２５ａ側壁部
２５ｃ底部（第１のシームレス缶の底部）
２７シームレス缶（第３のシームレス缶）
２７ａ側壁部
２８シームレス缶
３１ダイ
３２リングダイ
３３環状平面部（ダイ平面部）
３４加工コーナ
３４ａ下端（前端部）
３７上しごき部（第１のしごき部）
４１下しごき部（第２のしごき部）
４５ポンチ
４５ｄ円筒形部
４５ｅテーパ部
４６皺押え具[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a seamless can coated with an organic film by a redrawing-ironing method.
[0002]
[Prior art]
Japanese Unexamined Patent Publication No. 7-275961 discloses a method in which a wrinkle presser is inserted into a metal cup whose inner and outer surfaces are coated with an organic film, and the punch is pressed into the cavity of the die while pressing the bottom of the metal cup against the plane of the die with the wrinkle presser. While moving forward, the side wall outer surface of the metal cup is brought into close contact with the die flat part, the processing corner having a small radius of curvature of the die, while reducing the thickness of the side wall part by bending and stretching at the processing corner, and further, with a punch, A method of manufacturing an elongated seamless can by performing ironing in cooperation with a front end portion of a processing corner or an ironing portion in front of the front end portion to reduce the thickness of a side wall portion, that is, thinning performed in the same process. A drawing-ironing method has been proposed.
However, in the thinning re-drawing and ironing method described in the above-mentioned publication, when the side wall portion is to be thinned, the side wall portion is easily broken, and thus the side wall portion of the manufactured seamless can is made thinner, and thus the weight of the seamless can is reduced. However, there is a problem that the cost reduction by the above is not sufficient.
[0003]
[Problems to be solved by the invention]
An object of the present invention is to provide an improved method for producing a seamless can by the thinning redrawing and ironing method, which is performed in the same process, in which the side wall portion is hardly broken even when the side wall portion is thinned.
[0004]
[Means for Solving the Problems]
The method for manufacturing a seamless can according to the invention according to claim 1 comprises:
Inserting a wrinkle suppressor into the drawn molded body whose inner and outer surfaces are coated with the organic coating, and pressing the bottom of the drawn molded body against the die flat surface with the wrinkle presser, advance the punch into the die cavity, While making the outer surface of the side wall portion of the drawn compact closely contact with the die plane portion, the processing corner having a small radius of curvature of the die, the thickness of the side wall portion is reduced by bending and stretching at the processing corner, and further, the punch and the front end of the processing corner Or a method of manufacturing a first seamless can that is thinner than the drawn molded body by performing ironing in cooperation with an ironing part located forward of the front end to further reduce the thickness of the side wall part,
The thickness reduction after ironing of the side wall thickness of the drawn compactBe equal in height directionlike,
Of the side wall of the drawn bodyThe thickness gradually increases upwardInward to the rear corresponding to the thickness distribution in the height direction0 degrees 1 minute to 0 degrees 30 minutesThe inclined taper part,Connect to the upper end of the cylindrical part of the punchIt is characterized by processing using the provided punch.
When the ironing section is at the front end of the machining corner, the ironing section consists of a circular line. The ironing portion forward of the front end of the working corner is usually short cylindrical.
[0005]
When a normal drawing is performed from a flat blank, a portion to be a side wall of the drawn product is formed by entering the die cavity while being compressed in the circumferential direction. The curved portion between the side wall and the bottom receives a relatively high stretching force. For this reason, it is known that the curved portion of the drawn compact is slightly thinner than the thickness of the blank, but the side wall portion is gradually thicker from below to above, and the thickness of the end face portion is considerably larger than the thickness of the blank. For example, assuming that the thickness of the end face is tm, the thickness of the blank is t0, and the drawing ratio is R, tm is equal to a value obtained by multiplying t0 by the square root of R (“Illustrated Press Processing Dictionary”, Miyakawa Matsuo Edition, pp. 118-119, October 30, 1976, published by Nikkan Kogyo Shimbun). This relational expression seems to have been obtained for an extremely soft blank for deep drawing (a Rockwell 30T hardness of about 50).
Therefore, when a conventional, substantially full-length punch is used to reduce the thickness of the drawn product and redrawing and ironing, the thickness of the side wall portion of the formed seamless can is substantially increased in the height direction. Therefore, the greater the thickness reduction amount, particularly the amount of ironing, that is, the closer to the opening end, the greater the thickness. Therefore, it is considered that the ironing amount easily reaches the breaking upper limit, and the side wall portion is easily broken during molding.
[0006]
In the case of the invention according to claim 1, the punch is slightly rearwardly corresponding to the thickness distribution in the height direction of the side wall portion of the drawn formed body so that the thickness reduction amount becomes substantially equal in the height direction. A tapered portion is provided which becomes thinner. Therefore, when compared with the thinning redrawing-ironing process in which the same height is obtained at the same redrawing ratio, the amount of reduction in the thickness of the side wall portion is higher in the upper portion as in the case of using a conventional punch. Nothing. Therefore, it is possible to make the side wall thin without breaking the side wall.
[0007]
According to a second aspect of the present invention, the object to be molded is not a drawn molded body but a first seamless can formed by the method of the first aspect. This is a method for producing a second seamless can that is longer than the first seamless can by performing it one or more times.
Since the punch forming the first seamless can is provided with a tapered portion that becomes slightly thinner toward the rear, the side wall of the first seamless can also has a large wall thickness with at least the upper part facing upward. Has become. Accordingly, by the same operation as described in paragraph number 0006, the second seamless can having a thinner side wall portion and having a wall thickness increasing at least at the upper portion is formed without breaking. can do.
The same can be said for each time when the method according to claim 1 is performed a plurality of times.
[0008]
The method for producing a seamless can of the invention according to claim 3 comprises:
The punch is advanced into the cavity of the die while the bottom of the first seamless can is pressed against the flat surface of the die with the wrinkle press, and the punch is moved into the first seamless can. While the outer surface of the side wall portion is in close contact with the die flat surface portion and the processing corner having a small radius of curvature of the die, the thickness of the side wall portion is reduced by bending and stretching at the processing corner, and the punch and the front end or front end of the processing corner are further reduced. The ironing is performed in cooperation with the first ironing part located forward of the part to further reduce the thickness of the side wall part, and the second ironing part is provided immediately in front of the first ironing part in the vicinity of the first ironing part. In a method of manufacturing a third seamless can that is longer than the first seamless can by ironing to reduce the thickness of the side wall in cooperation with the first seamless can. Shin - ironing thickness reduction amount after processingBe equal in height directionAs shown in the side wall of the first seamless canThe thickness gradually increases upwardInward to the rear corresponding to the thickness distribution in the height direction0 degrees 1 minute to 0 degrees 30 minutesThe inclined taper part,
Connect to the upper end of the cylindrical part of the punchIt is characterized by processing using the provided punch.
[0009]
As described in paragraph number 0007, the side wall of the first seamless can has an increased wall thickness in the upward direction. Accordingly, the third seamless can having a thinner side wall and an elongated shape can be manufactured by the same operation as described in paragraph 0006 without breaking.
When the molding is completed, the side wall portion (corresponding to the opening end) between the first and second ironing portions is not subjected to the ironing process by the second ironing portion. Therefore, this portion (open end portion) is thicker than the lower side wall portion (see curve 2 in FIG. 10), and molding defects such as wrinkles and cracks during neck-in processing and flange processing are less likely to occur.
[0010]
The method for producing a seamless can according to the invention according to claim 4 comprises:
The punch is advanced into the cavity of the die while the wrinkle presser is inserted into the second seamless can, and the bottom of the second seamless can is pressed against the flat surface of the die by the wrinkle presser. While the outer surface of the side wall portion is in close contact with the die flat surface portion and the processing corner having a small radius of curvature of the die, the thickness of the side wall portion is reduced by bending and stretching at the processing corner, and the punch and the front end or front end of the processing corner are further reduced. The ironing is performed in cooperation with the first ironing part located forward of the part to further reduce the thickness of the side wall part, and the second ironing part is provided immediately in front of the first ironing part in the vicinity of the first ironing part. A method of manufacturing a fourth seamless can which is thinner than the second seamless can by ironing to further reduce the thickness of the side wall in cooperation with the second seamless can. Shin - ironing thickness reduction amount after processingBe equal in height directionLike the side wall of the second seamless canThe thickness gradually increases upward
Inward to the rear corresponding to the thickness distribution in the height direction0 degrees 1 minute to 0 degrees 30 minutesThe inclined taper part,
Connect to the upper end of the cylindrical part of the punchIt is characterized by processing using the provided punch.
As described in paragraph number 0007, the side wall portion of the second seamless can has a wall thickness that increases at least at an upper portion thereof. Therefore, as described in paragraph 0009, a thin and long fourth seamless can can be manufactured without breaking. Further, the side wall portion (corresponding to the opening end) between the first ironing portion and the second ironing portion at the time when the molding is completed is thicker than the lower side wall portion, and is used for neck-in processing and flange processing. Molding defects such as wrinkles and cracks are unlikely to occur.
[0011]
The method for manufacturing a seamless can according to the invention according to claim 5,
A wrinkle presser is inserted into the drawn compact, and the punch is advanced into the die cavity while holding the bottom of the drawn compact against the flat surface of the die with the wrinkle presser. The die plane portion, the thickness of the side wall portion is reduced by bending and stretching at the processing corner while being in close contact with the processing corner having a small radius of curvature of the die, and the punch and the front end of the processing corner or the front end of the front edge of the processing corner are further reduced. The ironing process is performed in cooperation with the first ironing portion to reduce the thickness of the side wall portion, and the ironing process is immediately performed in cooperation with the second ironing portion provided near the first ironing portion and in front of the first ironing portion. And further reducing the thickness of the side wall portion to produce a fifth seamless can that is narrower than the drawn body, wherein the thickness of the side wall portion of the drawn body is reduced by bending and stretching after ironing.Be equal in height directionAs shown in the drawing,The thickness gradually increases upwardInward to the rear corresponding to the thickness distribution in the height direction0 degrees 1 minute to 0 degrees 30 minutesThe inclined taper part,Connect to the upper end of the cylindrical part of the punchIt is characterized by processing using the provided punch.
The drawn molded body has a thicker wall with the side wall part directed upward. Therefore, as described in paragraph 0009, the fifth seamless can having a thinner side wall and an elongated shape can be manufactured without breaking. Further, the side wall portion (corresponding to the opening end) between the first ironing portion and the second ironing portion at the time when the molding is completed is thicker than the lower side wall portion, and is used for neck-in processing and flange processing. Molding defects such as wrinkles and cracks are unlikely to occur.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
A blank 1 shown in FIG. 1 is a metal plate 2 for a can in which a thin organic coating 3, for example, a thermoplastic polyester film is coated on both surfaces by thermal bonding, is circular, and has a total thickness of t0.
The drawn compact 4 shown in FIG. 2 is a drawn compact formed by a normal drawing method using a die having a processing corner having a relatively larger radius of curvature than the blank 1. The thickness of the bottom portion 4a of the drawn body 4 is substantially equal to the thickness t0 of the blank 1. The minimum thickness of the curved portion 4b of the drawn molded body 4 is slightly smaller than t0, the thickness of the side wall portion 4c gradually increases upward, and becomes maximum at the end face portion 4c1 (see curve 1 in FIG. 8).
[0014]
FIG. 3 shows a state in the middle of forming the intermediate seamless can 25 by thinning and redrawing and ironing the drawn compact 4. Reference numeral 11 denotes a die, and reference numeral 12 denotes a die supporting portion for supporting the die 11. Reference numeral 20 denotes a punch mounted on a punch plate (not shown) via a punch support cylinder 22. The punch 21 is coaxial with the die 11, surrounds the punch 20 with a slight gap 19 therebetween, and is coaxial with the punch 20. It is a wrinkle holder attached to a die shoe (not shown).
The die 11 includes a flat annular flat surface portion 13 serving as an upper surface, a processing corner 14 having a small radius of curvature Rd1 connected to the annular flat surface portion 13, an inverted frustoconical approach portion 15 connected to a lower end 14a of the processing corner 14, and an approach portion. 15 has a short cylindrical ironing portion 17 and a flank 18 connected to each other through a curvature portion or a sharp corner 16. The radius of curvature Rd1 of the processing corner 14 is (1 to 5) × t0 (t0 is the thickness of the blank), and more preferably (1 to 2), in order to reduce the thickness when performing redrawing at the processing corner 14. .9) It is desirable that xt0.
[0015]
The punch 20 has a flat bottom surface 20a having an air outlet opening (not shown), a curved portion 20b connected to the bottom surface 20a, and an inverted truncated conical portion 20c having a slight height connected to the upper end of the curved portion 20b. And a cylindrical portion 20d which is connected to the upper end of the inverted truncated conical portion 20c and occupies almost half of the total height. The punch 20 further includes a tapered portion 20e that is connected to the upper end 20d1 of the cylindrical portion 20d and that is inclined inward and upward at a slight taper angle β with respect to the axis. The height of the punch 20 is slightly larger than the height of the intermediate seamless can 25 to be formed.
The inverted truncated conical portion 20c is provided to reduce the amount of ironing at the beginning of processing. In the initial stage of the ironing process, the bottom portion of the previous process, that is, the original plate thickness portion is ironed. Therefore, in order to reduce the ironing amount in this portion, an inverted truncated conical portion 20c having a tapered portion is provided. The height H1 of the inverted truncated cone 20c and the inclination angle α with respect to the central axis are determined by the drawing ratio, the original plate thickness, and the iron clearance (ironing amount) (see FIG. 9). Usually, the height H1 is about 2 to 10 mm, and the inclination angle α is about 0 ° 10 minutes to 1 ° 30 minutes, but is not limited thereto.
[0016]
The thickness of the side wall 25a of the intermediate seamless can 25 at a certain position in the height direction is determined by the clearance between the ironing portion 17 of the die 11 and the punch 20. The clearance is (D−d) / 2, where d is the diameter of the punch 20 at the position and D is the inner diameter of the ironing portion.
A substantially lower half of the side wall 25a of the intermediate seamless can 25 includes an outer portion of a portion of the bottom 4a of the drawn molded body 4 which is in contact with the punch bottom surface 20a, and a lower portion of the curved portion 4b and the side wall 4c (see FIG. 2). ), But the thickness of these parts is almost equal. Therefore, these portions are squeezed by the cylindrical portion 20d of the punch 20 and the ironing portion 17, but the thickness reduction amount after ironing, that is, the thickness reduction amount (the side wall of the drawn molded body 4 corresponding to a certain portion after ironing) The value obtained by subtracting the thickness of the portion after ironing from the thickness of the portion 4c) is substantially the same. Although the upper portion of the drawn compact 4 becomes thicker upward, the tapered angle β of the tapered portion 20e is determined in accordance with the rate of the increase, so that the reduced thickness of this portion after ironing is made substantially the same. Therefore, the thickness reduction of the entire side wall portion can be made substantially equal. The taper angle β is usually 0 degree 1 minute to 0 degree 30 minutes, more preferably 0 degree 2 minutes to 0 degree 15 minutes.
[0017]
The height Hs1 of the cylindrical portion 20d and the taper angle β of the tapered portion 20e are determined by calculating the volume before and after the formation of the side wall portion 25a of the intermediate seamless can 25 (with a constant volume condition) and calculating the thickness reduction. (With a constant thickness reduction condition) performed using, for example, CAD, an approximate value can be obtained. The exact value is determined by conducting experiments with various combinations of the height Hs1 and the taper angle β and finding a combination that gives “substantially constant thickness reduction”.
[0018]
The intermediate seamless can 25 is formed by the above tools as follows.
The wrinkle presser 21 is inserted into the drawn compact 4, and the punch 20 is pressed by the wrinkle presser 21 while pressing the periphery of the bottom 4 a of the drawn compact 4 against the annular flat portion 13 of the die 11. While being advanced into the cavity, the outer surface of the side wall portion 4c of the drawn compact 4 is brought into close contact with the annular flat portion 13 and the processing corner 14 having a small radius of curvature of the die 11, and the plate of the side wall portion 4c is bent and stretched at the processing corner 14. Reduce thickness. Immediately in cooperation with the punch 20 and the ironing portion 17, the side wall portion 4c having the reduced thickness is ironed to further reduce the wall thickness, and the molding is finished when the flange portion (25b described later) remains. In this way, the drawn molded body 4 is formed into an intermediate seamless can 25 whose side wall (25a) is thinner, thinner and higher.
FIG. 4 shows a state where the molding is completed and the intermediate seamless can 25 having the flange portion 25b is formed. The thickness of the lower portion 25a1 occupying substantially the lower half of the side wall portion 25a of the intermediate seamless can 25 is substantially uniform. The thickness of the upper portion 25a2 occupying substantially the upper half of the side wall portion 25a gradually increases linearly upward (see curve 2 in FIG. 8). 25a3 is a boundary between the lower part 25a1 and the upper part 25a2.
[0019]
FIG. 5 shows a state in which the intermediate seamless can 25 is further thinned and re-drawn and ironed to form a thinner and higher seamless can 27.
In FIG. 5, reference numeral 31 denotes a thinning re-drawing-ironing die, 32 denotes an ironing ring die, and the ironing ring die 32 is supported by a support 43. Mounted coaxially on top of each other. The inner diameter of the ironing ring die 32 is smaller than the inner diameter of the redraw-ironing die 31.
Reference numeral 45 denotes a punch coaxial with the redrawing-ironing die 31 and the ironing ring die 32, and 46 surrounds the punch 45 with a slight gap 30, and is mounted on an upper die shoe (not shown) coaxially with the punch 45. It is a wrinkle holder that has been made.
The die 31 has a flat annular flat surface portion 33 serving as an upper surface, a processing corner 34 having a small radius of curvature Rd2 connected to the annular flat surface portion 33, an inverted frustoconical approach portion 35 connected to a lower end 34a of the processing corner 34, and an approach portion 35. And a short cylindrical upper ironing portion 37 and a flank 38 connected to each other through a curvature portion or a sharp corner 36. In order to reduce the thickness when performing drawing at the processing corner 34, the radius of curvature Rd2 of the processing corner 34 is (1-5) xt0 (t0 is the thickness of the blank), and more preferably (1-2. 9) It is desirable that xt0.
The die 32 includes an inverted frustoconical approach portion 39, a short cylindrical lower ironing portion 41 connected to the approach portion 39 via a curvature portion or a sharp corner 40, and a flank 42.
[0020]
The punch 45 has a flat bottom surface 45a having an air outlet opening (not shown), a curved portion 45b connected to the bottom surface 45a, and an inverted truncated conical portion 45c having a slight height connected to the upper end of the curved portion 45b. And a cylindrical portion 45d which is connected to the upper end of the inverted truncated conical portion 45c and occupies almost half of the total height. The punch 45 further includes a tapered portion 45e which is connected to the upper end 45d1 of the cylindrical portion 45d and is inclined inward and upward at a slight taper angle ρ with respect to the axis. The height of the punch 45 is slightly larger than the total height of the seamless can 27 to be formed.
The height H2 of the inverted truncated conical portion 45c and the inclination angle θ with respect to the central axis are determined by the drawing ratio, the original plate thickness, and the ironing clearance (ironing amount) (see FIG. 11). Usually, the height H2 is about 2 to 10 mm, and the inclination angle θ is about 0 ° 10 minutes to 1 ° 30 minutes, but is not limited thereto.
[0021]
The thickness of the side wall portion 27a of the seamless can 27 is determined by the clearance between the upper and lower ironing portions 37 and 41 and the punch 45 as described above. A substantially lower half of the side wall 27a of the seamless can 27 includes an outer portion of the bottom 25c of the intermediate seamless can 25 that comes into contact with the punch bottom surface 45a, a curved portion 25d, and a lower portion 25a1 of the side wall 25a (see FIG. 4). ). The former two, although thicker than the lower part 25a1, are squeezed by the inverted frustoconical part 45c at the tip of the punch and the lowering part 41 having a relatively large clearance. The lower portion 25a1 of the side wall portion 25a is squeezed by the cylindrical portion 45d of the punch 45 and the lowering portion 41, and the thickness of this portion is substantially uniform. Accordingly, the thickness of the lower half of the side wall 27a after ironing is substantially uniform.
[0022]
The upper portion 25a2 of the intermediate seamless can 25 becomes thicker upward, but by determining the taper angle ρ of the tapered portion 45e in accordance with the rate of this increase, the thickness reduction by ironing of this portion can be made substantially the same. Therefore, the thickness reduction of the entire side wall portion 25a can be made substantially equal. The taper angle ρ is usually 0 degree 1 minute to 0 degree 30 minutes, more preferably 0 degree 2 minutes to 0 degree 15 minutes.
[0023]
The height Hs2 of the cylindrical portion 45d and the taper angle ρ of the tapered portion 45e are calculated by calculating the volume before and after the formation of the side wall 27a of the seamless can 27 (with a constant volume condition) and calculating the thickness reduction ( An approximate value can be obtained by performing, for example, CAD under the condition of a constant thickness reduction. The exact value is determined by conducting experiments with various combinations of the height Hs2 and the taper angle ρ to find the combination that gives “substantially constant thickness reduction”.
[0024]
The seamless can 27 is formed as follows by the above tools.
The wrinkle presser 46 is inserted into the intermediate seamless can 25, and the punch 45 is pressed into the die 31 while pressing the peripheral portion of the bottom 25 c of the intermediate seamless can 25 against the annular flat portion 33 of the die 31 with the wrinkle presser 46. 32, the outer surface of the side wall portion 25a of the intermediate seamless can 25 is brought into close contact with the annular flat portion 33 and the processing corner 34 having a small radius of curvature of the die 31, and the side wall portion 25a is bent and stretched at the processing corner 34. The thickness of the sheet.
Immediately in cooperation with the punch 45, the upper ironing portion 37 and the lower ironing portion 41, the side wall portion 25a having a reduced thickness is ironed to further reduce the wall thickness, and is formed when the flange portion (27b described later) remains. To end. In this case, at the time when the forming is completed, the opening end 27x which is the portion of the side wall 25a between the ironing portion 41 and the ironing 37 is not subjected to ironing by the ironing portion 41. Therefore, the opening end portion 27x is particularly thicker than other portions of the reduced side wall portion 25a (27a described later) (see (27x) of the curve 2 in FIG. 10). In this manner, the intermediate seamless can 25 is formed into a seamless can 27 having a thinner, thinner and higher side wall 27a.
[0025]
FIG. 6 shows a state where the molding is completed and a seamless can 27 having a flange 27a is formed. The thickness of the lower portion 27a1 of the side wall portion 27a of the seamless can 27 is substantially uniform, and the thickness of the upper portion 27a2 gradually increases upward, and then increases from the portion in contact with the lower ironing portion 41. The opening end 27x is further enlarged. 27a3 is a boundary between the lower part 27a1 and the upper part 27a2.
[0026]
The seamless can 27 is removed from the tool after the bottom 27c is domed in the next step. Thereafter, the side wall portion 27a is cut from below the flange portion 27b, and the opening end portion 27x is subjected to neck-in processing and flange processing. For example, as shown in FIG. 7, a flange portion 28a, a neck-in portion 28b, a side wall portion 28c, a chime portion It is formed into a seamless can 28 used for canning and the like, having a dome portion 28d and a concave dome portion 28 on the inside.
The open end 27x has a cylindrical outer surface and a frusto-conical inner surface with a slight taper angle ρ. Therefore, the end face of the opening end 27x after the cutting is the thickest in the side wall 27a. Therefore, even if the thickness of the main portion of the side wall portion 27a is reduced, since this end face is relatively thick, wrinkles during neck-in processing and cracks during flange processing are unlikely to occur.
[0027]
Although not shown, the intermediate seamless can 25 is thinned and re-drawn and ironed using a punch and a die of the type shown in FIG. Seamless cans can be manufactured whose thicknesses are substantially equal over the entire height. This seamless can is further thinned and redrawn one or more times using a punch and die of the type shown in FIG. Another seamless can can be manufactured that is substantially equal throughout.
Although illustration is omitted, the seamless can manufactured as described above is thinned and re-drawn using a punch and a die of the type shown in FIG. It is possible to produce a seamless can whose thickness is substantially equal over the entire height and which has a relatively thick open end.
Although not shown, the drawn molded body 4 is thinned and redrawn using a punch and a die of the type shown in FIG. 5 and ironed to obtain a thinner and thinner side wall portion. Can be manufactured substantially seamlessly over the entire height and having a relatively thick open end.
[0028]
【Example】
0.180 mm thick, 0.025 mm thick on the surface to be used as the inner surface of the can of tin-free steel 2 (electrolytic chromic acid-treated steel plate) of DR-6M (twice cold-rolled steel plate: Rockwell 30T hardness: 66-72) Of a biaxially stretched ethylene terephthalate / ethylene isophthalate copolymer (mol ratio: 88/12, melting point 230 ° C., glass transition temperature Tg: 70 ° C.) having a thickness of 0.017 mm on the surface to be the outer surface of the can About 50 mg / m 2 of paraffin wax (melting point Tm: 60 ° C.) on both sides of a laminated steel sheet (total thickness t0 = 0.222 mm) produced by heat bonding.²Was applied.
This laminated steel plate is punched into a circular blank 1 having a diameter of 154 mm by a draw forming machine (not shown), and the blank 1 is drawn at a drawing ratio of 1.62 using a normal die having a processing corner having a radius of curvature of 0.8 mm. By processing, a drawn compact 4 (FIG. 2) having an average height H0 of 43 mm and an inner diameter D0 of 95 mm was produced. Curve 1 in FIG. 8 shows the relationship between the thickness of the side wall portion 4c of the drawn compact 4 and the height from the inner surface of the bottom portion 4a.
[0029]
The drawn compact 4 is formed by forming a radius of curvature Rd1 of the processing corner 14 at 0.50 mm (Rd1 / t0 = 2.25), an angle of upward inclination with respect to the center axis of the approach portion 15 at 5 degrees, a sharp corner 16 and a sharpened portion 17. A die 11 having an inner diameter D1 of 81.97 mm, a radius of curvature of the curved portion 20b of 5 mm, a height H1 of the inverted cylindrical portion 20c of 6 mm, an inclination angle α of 1 degree, and a diameter d1 of the cylindrical portion 20d of 81.70 mm Using a tool of the type shown in FIG. 3 including a punch 20 (having a surface temperature of 50 ° C.) with a height Hs1 of 23 mm, a height of the tapered portion 20 e of 36 mm, and a taper angle β of 0 ° 4 min, A thinning redrawing-ironing process was performed at a drawing ratio of 1.16 to produce an intermediate seamless can 25 having a height of 72 mm.
Curve 2 in FIG. 8 shows the relationship between the thickness of the side wall 25a of the intermediate seamless can 25 and the height from the inner surface of the bottom 25c. In the curve 2, there is no reduction in the thickness at a position where the height from the inner surface of the bottom is about 4 to 5 mm, as shown in FIG. 9, in the vicinity of the lower end of the inverted cylindrical portion 20 c, This is because the clearance with the punch 20 is larger than the thickness of the side wall 4c of the drawn molded body at the position.
From the thickness difference between the corresponding portions of the curves 1 and 2 (for example, the points a and b or the points c and d), the thickness reduction (mm) in the corresponding portions is obtained. Curve 3 shows the relationship between the punch stroke (the stroke when the punch bottom surface 20a reaches the flat portion 13 of the die 11 is 0 mm) and the thickness reduction amount. The thickness reduction is substantially constant at about 0.06 mm except that the height is 0 at a position of about 4-5 mm. The portion between the point c and the point e in the curve 1 is the flange 25b.
[0030]
For comparison, the drawn molded body 4 was redrawn and ironed in the same manner as described above, except that a punch having a cylindrical length was used except for the inverted frustoconical portion 20c having no tapered portion 20e. However, the sidewall was broken at a position about 65 mm from the bottom of the punch, and molding was impossible. The amount of thickness reduction at the breaking position was about 0.09 mm.
[0031]
The intermediate seamless can 25 produced as described in paragraph 0029 was thinned and redrawn and ironed using a tool of the type shown in FIG. 5 to produce a seamless can 27 having a height of 127 mm.
In this case, the radius of curvature Rd2 of the machining corner 34 is 0.70 mm (Rd2 / t0 = 3.15), the inner diameter D2 of the upper ironing portion 37 is 66.32 mm, and the inner diameter D3 of the lower ironing portion 41 is 66 mm. At 23 mm, the vertical height from the upper end of the upper ironing portion 37 of the die 31 to the upper end of the lower ironing portion 41 of the die 32 was 18.5 mm. The upward inclination angle with respect to the central axis of the approach portion 35 was 4 degrees, the upward inclination angle with respect to the central axis of the approach portion 39 was 2 degrees, and 36 and 40 were sharp corners.
The radius of curvature of the curved portion 45b of the punch 45 is 5 mm, the height H2 of the inverted cylindrical portion 45c is 15 mm, the inclination angle θ is 0 degrees 35 minutes, the diameter d2 of the cylindrical portion 45d is 66.05 mm, and the height Hs2 is 55 mm. The height of the tapered portion 45e was 42 mm, and the taper angle ρ was 0 degrees 3 minutes 20 seconds. The surface temperature of the punch 45 was kept at 50 ° C.
[0032]
Curve 2 in FIG. 10 shows the relationship between the thickness of the side wall 27a of the seamless can 27 and the height from the inner surface of the bottom 27c. The curve 1 in FIG. 10 also shows the relationship between the thickness of the side wall 25a of the intermediate seamless can 25 and the height from the inner surface of the bottom 25c.
From the thickness difference between the corresponding portions of the curves 1 and 2 (for example, the points f and g or the points h and i), the thickness reduction (mm) in the corresponding portions is obtained. A curve 3 shows the relationship between the punch stroke (the stroke when the punch bottom surface 45a reaches the flat portion 33 of the die 31 is 0 mm) and the thickness reduction amount. The thickness reduction varies within a relatively small range up to a height of 40 mm. This is because, as shown in FIG. 11, the inverted frusto-conical portion 45c is squeezed only by the upper ironing portion 37. The thickness reduction amount is about 0.04 mm at a position where the height exceeds 40 mm, and is almost constant. The portion between points j and 1 indicates the flange portion 25b, and the portion between points k and m indicates the flange portion 27b.
[0033]
For comparison, the intermediate seamless can 25 was thinned and re-drawn and ironed in the same manner as described above except that a punch having a cylindrical length was used except for the inverted frustoconical portion 45c having no tapered portion 45e. Although it was processed, the side wall was broken at a position of about 105 mm from the bottom of the punch, and molding was impossible. The amount of thickness reduction at the breaking position was about 0.06 mm.
[0034]
【The invention's effect】
The method for producing a seamless can by the thinning redrawing and ironing method performed in the same step according to the first and second aspects of the invention has an effect that even if the side wall portion is thinned, the side wall portion is hardly broken. The inventions according to claims 3, 4, and 5 have an advantage that, in addition to the above effects, wrinkles when necking in the formed open end and cracks or the like during flange processing are less likely to occur.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of an example of a blank for forming the drawn compact of FIG. 2;
FIG. 2 is a vertical cross-sectional view of an example of a drawn compact.
FIG. 3 is a longitudinal sectional view of an essential part showing a state in which the drawn compact of FIG. 2 is being redrawn and ironed while being drawn.
FIG. 4 is a longitudinal sectional view of an essential part showing a state at the time when an intermediate seamless can is formed after the thinning re-drawing and ironing shown in FIG. 3 is completed.
FIG. 5 is a longitudinal sectional view of an essential part showing a state in which the intermediate seamless can formed from the drawn molded article of FIG. 2 is being thinned and redrawn and ironed.
6 is a longitudinal sectional view of an essential part showing a state at the time when the thinning redrawing-ironing process shown in FIG. 5 is completed and a seamless can is formed.
7 is a longitudinal sectional view of an example of a can body obtained by subjecting the seamless can of FIG. 6 to doming, neck-in, and flange processing.
FIG. 8 is a diagram showing the relationship between the thickness of the side wall portion of the drawn molded body and the intermediate seamless can and the height from the inner surface of the can bottom in the molding shown in FIGS. 3 and 4, and the side wall portion during molding. FIG. 3 is a diagram showing a relationship between a thickness reduction amount and a punch stroke.
FIG. 9 is a longitudinal sectional view of an essential part showing a state at an early stage of the molding shown in FIG. 3;
FIG. 10 is a diagram showing the relationship between the thickness of the side wall of the intermediate seamless can and the seamless can and the height from the inner surface of the can bottom in the molding shown in FIG. 5 and FIG. FIG. 4 is a diagram showing a relationship between a thickness reduction amount and a punch stroke.
FIG. 11 is a longitudinal sectional view of an essential part showing a state at an early stage of the molding shown in FIG. 5;
[Explanation of symbols]
3 Organic coating
4 Drawings
4a bottom
4c Side wall
11 dies
13 annular flat part (die flat part)
14 Machining corner
14a Lower end (front end)
17 Ironing part
20 punches
20d cylindrical part
20e taper part
21 Wrinkle holder
25 Intermediate seamless cans (first seamless cans)
25a Side wall
25c Bottom (bottom of first seamless can)
27 Seamless cans (third seamless cans)
27a Side wall
28 seamless cans
31 die
32 ring dies
33 annular flat part (die flat part)
34 Machining corner
34a Lower end (front end)
37 Upper ironing part (first ironing part)
41 Lower ironing part (second ironing part)
45 punch
45d cylindrical part
45e taper part
46 Wrinkle retainer

Claims

Inserting a wrinkle suppressor into the drawn molded body whose inner and outer surfaces are coated with the organic coating, and pressing the bottom of the drawn molded body against the die flat surface with the wrinkle presser, advance the punch into the die cavity, While making the outer surface of the side wall portion of the drawn compact closely contact with the die plane portion, the processing corner having a small radius of curvature of the die, the thickness of the side wall portion is reduced by bending and stretching at the processing corner, and further, the punch and the front end of the processing corner Or a method of manufacturing a first seamless can that is thinner than the drawn molded body by performing ironing in cooperation with an ironing part located forward of the front end to further reduce the thickness of the side wall part,
In order that the thickness reduction after ironing of the side wall thickness of the drawn body becomes equal in the height direction ,
A punch is formed by tapering a tapered portion inclined inward toward the rear at 0 degrees 1 minute to 0 degrees 30 minutes corresponding to the height direction thickness distribution in which the thickness gradually increases toward the upper side of the side wall portion of the drawn molded body. A process using a punch connected to the upper end of the cylindrical portion of the above .

A method for producing a second seamless can which is longer than the first seamless can by applying the method of claim 1 to the first seamless can one or more times.

The punch is advanced into the cavity of the die while the wrinkle presser is inserted into the first seamless can and the bottom of the first seamless can is pressed against the flat surface of the die by the wrinkle presser. While the outer surface of the side wall portion is in close contact with the die flat surface portion and the processing corner having a small radius of curvature of the die, the thickness of the side wall portion is reduced by bending and stretching at the processing corner, and the punch and the front end or front end of the processing corner are further reduced. The ironing is performed in cooperation with the first ironing part located forward of the part to further reduce the thickness of the side wall part, and the second ironing part is provided immediately in front of the first ironing part in the vicinity of the first ironing part. In a method of manufacturing a third seamless can that is longer than the first seamless can by ironing to reduce the thickness of the side wall in cooperation with the first seamless can. Shin - as ironing thickness reduction amount after processing becomes equal to the height direction, corresponding to progressively wall thickness height direction thickness distribution becomes larger toward the upper side wall portion of the first seamless can, the rear The taper part which inclines at 0 degrees 1 minute to 0 degrees 30 minutes toward the inside,
A method for producing a seamless can, characterized in that processing is performed using a punch connected to the upper end of a cylindrical portion of the punch.

The punch is advanced into the cavity of the die while the wrinkle presser is inserted into the second seamless can and the bottom of the second seamless can is pressed against the flat surface of the die by the wrinkle presser. While the outer surface of the side wall portion is in close contact with the die flat surface portion and the processing corner having a small radius of curvature of the die, the thickness of the side wall portion is reduced by bending and stretching at the processing corner, and the punch and the front end or front end of the processing corner are further reduced. The ironing is performed in cooperation with the first ironing part located forward of the part to further reduce the thickness of the side wall part, and the second ironing part is provided immediately in front of the first ironing part in the vicinity of the first ironing part. A method of manufacturing a fourth seamless can which is thinner than the second seamless can by ironing to further reduce the thickness of the side wall in cooperation with the second seamless can. Shin - as ironing thickness reduction amount after processing becomes equal to the height direction, corresponding to progressively thickness increases <br/> height direction thickness distribution toward the upper sidewall portion of the second seamless can The tapered part which inclines at 0 degree 1 minute-0 degree 30 minutes inward toward the rear,
A method for producing a seamless can, characterized in that processing is performed using a punch connected to the upper end of a cylindrical portion of the punch.

A wrinkle presser is inserted into the drawn compact, and the punch is advanced into the die cavity while holding the bottom of the drawn compact against the flat surface of the die with the wrinkle presser. The die plane portion, the thickness of the side wall portion is reduced by bending and stretching at the processing corner while being in close contact with the processing corner having a small radius of curvature of the die, and the punch and the front end of the processing corner or the front end of the front edge of the processing corner are further reduced. The ironing process is performed in cooperation with the first ironing portion to reduce the thickness of the side wall portion, and the ironing process is immediately performed in cooperation with the second ironing portion provided near the first ironing portion and in front of the first ironing portion. And further reducing the thickness of the side wall portion to produce a fifth seamless can that is narrower than the drawn body, wherein the thickness of the side wall portion of the drawn body is reduced by bending and stretching after ironing. Height etc. Kunar so on, corresponding to progressively wall thickness height direction thickness distribution becomes larger toward the upper side wall portion of the draw-forming body, inclined at 0 degrees 1 minute to 0 ° C for 30 minutes inwardly toward the rear A method for manufacturing a seamless can, characterized in that the tapered portion is processed using a punch provided by being connected to an upper end of a cylindrical portion of the punch.