JP3900640B2 - Steel plate for two-piece battery can excellent in sealing performance of sealing part and manufacturing method thereof - Google Patents

Description

【００２２】
【表２】

【００２３】
次に本発明における成分組成について説明する。
本発明の鋼板は、重量％で、０．０１％＜Ｃ＜０．０３％、０．０２％≦ｓｏｌ．Ａｌ≦０．１５％、Ｎ≦０．００３５％、Ｓｉ≦０．０２％、０．１％≦Ｍｎ≦１．０％、Ｐ≦０．０２％、Ｓ≦０．０２％、残部Ｆｅおよび不可避不純物からなる鋼組成を有している。また、０．０００５％≦Ｂ≦０．００５％のＢをさらに含有する。以下、このように組成を限定した理由について説明する。
【００２４】
Ｃ： Ｃは深絞り性、面内異方性を劣化さぜずに優れた封口部密封性をを確保するために極めて重要な元素であり、適正範囲内に制御しなければならない。Ｃ含有量が０．０３％以上になると、深絞り性が劣化し、多段の絞り成形過程で割れ等の成形不良が発生しやすくなるとともに、面内異方性が劣化し、結果として封口部密封性が低下する。従来の低Ｃ鋼を焼鈍後に二次圧延した鋼板は、焼鈍後に１．５％程度の調圧を施した鋼板に比べ、深絞り性、面内異方性が劣る領向にあり、特に鋼板板厚を薄くした、すなわちゲージダウンした鋼板ではそれが顕著となる。このような二次圧延した場合の特性劣化を回避するためには、Ｃ量を０．０３％未満にする必要があり、したがって本発明ではＣ量を０．０３％未満とする。一方、Ｃ量が０．０１％以下になると、耐時効性が急激に劣化し、二次圧延の圧下率が比較的低くＮｉめっき後に熱拡散処理を施した場合に、缶底周辺にストレッチャーストレイン（ＳＳ）が発生する場合があり好ましくない。そこで、本発明ではＳＳ発生を確実に抑制するためにＣを０．０１％超とする。この範囲の中でも特に０．０１５％以上、０．０２５％以下の範囲がより望ましい。
【００２５】
ｓｏｌ．Ａｌ： ｓｏｌ．Ａｌは後述するＮ量とともに、二次圧延した鋼板の深絞り性、面内異方性を良好に保つために重要な元素である。ｓｏ１．Ａｌは脱酸のため、およびＮをＡｌＮとして析出させ固溶Ｎ量を低減するために０．０２％以上の添加を必要とする。一方、０．１５％を超える多量のＡｌを添加しても、これらの効果は飽和し、かつ微細なアルミナ系介在物が残留しやすくなり、介在物起因の割れ等の成形不良が発生しやすくなる。そこで、本発明においては、ｓｏｌ．Ａｌ量を０．０２％以上、０．１５％以下とする。
【００２６】
Ｎ： Ｎは極力少なくすることが望ましい。Ｎが多い場合には、０．０２％以上のＡｌを添加しても固溶Ｎが残留しやすくなり、二次圧延後の鋼板の深絞り性、面内異方性を良好に保つことが困難となる。そこで、本発明においては、これらの悪影響を回避するために、Ｎ量を０．００３５％以下とする。さらに、０．００２５％以下とすることがより一層望ましい。
【００２７】
Ｂ： Ｂは封口部密封性をさらに向上させるために、必要に応じて添加する元素である。封口部をかしめ加工する際に曲げＲ外側の表面に微細なクラックが発生する場合があり、これが起点となりＮｉ層に鉄地に達するクラックが形成されると、封口部密封性が低下し、また耐食性も低下することがある。このような曲げＲ外側表層の微細クラックは、鋼板の粒界に析出した比較的大きなカーバイドを起点として発生する。Ｂを添加すると、Ｂが粒界に偏析するため、粒界に析出するカーバイドが減少し、カーバイドは粒内に比較的微細に分散析出するようになる。その結果として、Ｂ添加により微細クラックに起因した封口部密封性の低下が抑制される。また、ＢはＮをＢＮとして析出させ固溶Ｎを低減する作用も有しており、二次圧延材の深絞り性、面内異方性の向上にも有効である。これらのＢ添加効果を発揮させるためには、０．０００５％以上の添加が必要であり、一方、０．００３％を超える過剰な添加を行なってもこれらの効果は飽和し、逆に固溶Ｂの残留による深校り性の低下などの悪影響が顕在化してくる。以上のことから、本発明においては、Ｂを添加する場合に、その量を０．０００５％以上、０．００３％以下とする。そのなかでＢ添加効果を特に顕著に発揮させるためには、０．００１０％以上、０．００２５％以下とすることが望ましい。
【００２９】
Ｓｉ： Ｓｉは意図的な添加を行わない場合にも、不純物成分として鋼中に残留し鋼板の耐食性およびＮｉめっきの密着性を劣化させる元素であり、良好な耐食性を確保するためには、その含有量を０．０２％以下とすることが望ましい。
【００３０】
Ｍｎ： Ｍｎは鋼中ＳをＭｎＳとして析出させることによってスラブの熱間割れを防止する。Ｓを析出固定するためには０．１％以上添加することが望ましい。また、Ｍｎは鋼板の高強度化、細粒化に効果的な元素であり、必要に応じて適量添加してもよい。しかし、Ｍｎを過度に添加すると鋼板の耐食性およびＮｉめっきの密着性を劣化させるため、添加するにしてもその量を１．０％以下とすることが好ましい。
【００３１】
Ｐ： Ｐはフェライト粒界に偏析して粒界を脆化させ、絞り成形時の加工性を低下させる。また、Ｎｉめっきの密着性を低下させる元素であり、その含有量は極力少ないほうが好ましく、０．０２％以下とすることが望ましい。
【００３２】
Ｓ： Ｓはスラブの熱間割れ防止の観点から極力少ないほうが好ましく、０．０２％以下とすることが望ましい。
【００３３】
本発明の鋼板は、上記のような鋼組成を有し、焼鈍後の二次圧延により加工硬化していることを特徴とする。多段の絞り成形により製缶される電池缶用鋼板をゲージダウンした場合にも、かしめ強度向上をはかり充分な封口部密封性を確保するために、本発明においては、焼鈍後の鋼板を二次圧延して加工硬化させ、鋼板の高強度化をはかる。しかし、単に従来の低炭素鋼板を二次圧延により高強度化した場合には、前述のように深絞り性や面内異方性が劣化し、成形不良やかしめ強度の不均一による密封性の低下をもたらすため、従来の低Ｃ鋼に比べＣ量を低減し適正範囲に制御した鋼を素材として用いる必要がある。
【００３４】
鋼板の高強度化をはかる手段としては、加工硬化以外にも、析出強化、変態組織強化、細粒化強化、固溶強化などの種々の方法がある。しかし、析出強化では、充分な強度を確保するためには、Ｎｂ等の炭窒化物形成元素を添加し、多量の炭窒化物を分散析出させる必要があり、これらの炭窒化物が耐食性を劣化させ、めっきの密着性も劣化させる。さらに鋼板の深絞り性も劣化するという問題点を有している。また、変態組織強化をはかるためには、焼鈍時に高温焼純、急速冷却する必要があり、０．２ｍｍ程度の極薄ゲージダウン材を製造することは困難である。すなわち、連続焼純時にＣＡＬ内での絞りや蛇行、破断が発生しやすく、工業的に安定して極薄材の高強度化をはかることが困難となる。さらに、細粒化強化はその強化能が小さく、充分な強度を得ることができない。さらにまた、固溶強化は、上記のような問題点は比較的少ないが、充分な強度を得るために、強化能の大きいＣ、Ｎを多量に添加した場合には深絞り性や面内異方性が劣化し、Ｐ、Ｓｉを多量に添加した場合にはめっき密着性や深絞り性が大きく劣化する。Ｍｎは比較的悪影響が小さいが、強化能が小さいためＭｎのみでは充分な強度を確保することができない。また、Ｍｎも１％を超えるほど多量に添加した場合には、Ｐ、Ｓｉと同様な悪影響が顕著となってくる。
【００３５】
これらに対し、Ｃ量を適正範囲に制御した鋼板の二次圧延による加工硬化の場合には上記のような問題がなく、また、絞り成形時に時効によるストレッチャーストレインの発生が抑制される。
以上のことから、本発明においては、０．０１％＜Ｃ＜０．０３％の鋼板を焼鈍後の二次圧延により加工硬化させることを必須とする。
【００３６】
次に本発明の鋼板の製造方法について説明する。
転炉溶製後、連続鋳造して得られたスラブを粗圧延を経て、あるいは粗圧延を省略し直接熱間仕上圧延機に挿入し、熱間圧延を行う。スラブ加熱温度は、通常行われている範囲内の１０５０〜１２５０℃程度とすることができる。熱延仕上温度はＡｒ₃変態点以上とすることが望ましい。熱延仕上げ温度がＡｒ₃変態点より低くなると、熱延板に集合組織が形成されるとともに、表層結晶粒が粗大化したり加工組織が残存する場合があり、二次圧延後鋼板の深絞り性が劣化し、さらに鋼板板厚の不均一が生じやすく、結果として電池缶封口部の円周方向板厚不均一による密封性の低下をもたらすことになる。巻取温度は５００〜７００℃程度とすることができるが、Ｂを添加しない場合には固溶Ｎを低減するために６００℃以上とすることが望ましい。
【００３７】
さらに熱延鋼板を酸洗し、冷間圧延した後、連続焼鈍を行う。面内異方性を小さくするために、一次冷圧率は８０〜９０％程度が望ましく、後述する二次圧延も含めた全冷圧率は８３〜９３％程度が望ましい。ここで、全冷圧率とは、（熱延仕上厚−二次圧延後の板厚）／熱延仕上厚を表わしている。連続焼鈍の焼鈍温度は、未再結晶組織の残存による加工性の低下および過度の粒成長による粗粒化に起因した肌荒れを抑制するため、再結晶温度以上、７５０℃以下程度とすることが望ましい。
【００３８】
焼純後に、さらに二次圧延を行なう。二次圧延は鋼板の高強度化をはかり、電池缶に成形後の封口部のかしめ強度を高め、封口部密封性を向上させるために必要な工程である。図２にかしめ強度に対する二次圧延の圧下率の影響を示す。同図から二次圧延の圧下率が５％未満では充分なかしめ強度が得られないことがわかる。また、二次圧延の圧下率が３０％を超えるとかしめ強度が低下する傾向がある。３０％を超える高圧下率圧延を行なうと、鋼板の降伏強度が高くなりすぎて封口部のかしめ加工後のスブリングバックが大きくなり、逆にかしめ強度が低下し内容物の液漏れの危険性が大きくなる。この場合には、全圧下率を８３〜９３％程度にしても、面内異方性を充分に小さくすることが困難となり、封口部の円周方向板厚分布の不均一による密封性の低下が顕在化してくる。さらに、深絞り性が劣化し、多段絞り成形時に割れ発生等の成形不良が顕在化してくる。これらのことから、二次圧延の圧下率を１０〜２５％とする。
【００３９】
通常、電池用鋼板の両面には、製缶後の良好な耐食性を確保するためのめっき層および／または合金化めっき層等の耐食被覆層が形成されている。適用されるめっき層、合金化めっき層としては、耐食性を確保できるものであればその種類に特別な制約はなく、単層または複層のめっき層および／またはこのめっき層を熱拡散して得られた合金化めっき層を鋼板の両面に形成させればよい。ただし、電池内容物のアルカリに対する優れた耐食性を得るためには、少なくともＮｉめっき層またはＦｅ−Ｎｉ合金化めっき層を設けることが望ましい。このＦｅ−Ｎｉ合金化めっき層はＮｉめっき層を熱拡散処理して得られるもので、Ｎｉめっき層の全部を合金化（Ｆｅ−Ｎｉ）させたものでもよいし、下地鋼板とＮｉめっき層の界面のみを合金化させたものでもよい。このような合金層を生成させることにより、耐食性はさらに向上する。
【００４０】
前述のように、多段絞り成形により製缶される電池缶には、プレス成形後にＮｉめっきを行なう後めっき法とＮｉめっき鋼板をプレス成形するプレめっき法の２種類があるが、本発明鋼板は両者のいずれにも適用することができ、同様の効果を発揮することができる。
【００４１】
特に、後者の場合で優れた耐食性を確保するためには、鋼板両面にそれぞれ、少なくとも１層のＮｉめっき層および／またはＦｅ−Ｎｉ合金化めっき層を設けることが望ましい。また、Ｎｉめっき層および／またはＦｅ−Ｎｉ合金化めっき層の上層にＳｎめっき層を設け、さらに耐食性を高めることもできる。Ｎｉめっき厚は特に限定するものではないが、両面ともに１〜５μｍ程度の厚さとするのが望ましく、両面等厚めっき、差厚めっきのいずれもでもよい。また、Ｎｉめっき層を熱拡散処理する際の加熱条件も特に限定するものではないが、６００〜７５０℃で３０秒から３分程度とすることが好ましい。また、熱拡散処理後に、表面粗さの調整と時効によるＳＳ発生を抑制するために０．５〜２％程度の調圧を行うこともできる。さらに、この調圧後に再度Ｎｉめっきを行うことにより、耐食性は一段と向上する。
【００４２】
【実施例】
表３に示す組成の鋼を転炉溶製した後、連続鋳造によりスラブとし、加熱温度：１２００〜１２３０℃、仕上温度：８６０〜９００℃、巻取温度：６００〜６４０℃で熱間圧延し、酸洗後、冷間圧延し、さらに表４に示す条件で連続焼鈍、二次圧延または調質圧延を行い、０．２５、０．２０、０．１８ｍｍの板厚に仕上げ、鋼板の両面に厚さ４μｍのＮｉめっきを施した。全冷圧率は８６〜９０％とした。一部の鋼板については、Ｎｉめっき後に６５０℃で１分の熱拡散処理を施し、Ｆｅ−Ｎｉ合金化めっき層を形成させた。
【００４３】
これらの鋼板の引張試験を行い降伏強度を測定するとともに、直径４５ｍｍφの円形ブランクを打ち抜き、絞り比１．６７で深絞り成形し耳率を測定した。耳率は円周方向各位置の成形高さを測定し、成形高さの最大値と最小値の差を高さ最小値で割った百分率で表わした。さらに、直径５５ｍｍφの円形ブランクを打ち抜き、１０工程の多段絞り加工により最終直径１３．８５ｍｍの単３型電池缶相当の絞り缶を作製した。
【００４４】
これらの缶の缶端部をトリムした後、図１に示したように開口部に絶縁パッキンと封口蓋を装着し、かしめ加工により封口した後、缶底に穴を開けて増圧したエアーを封入し、封口部からのエアーの漏れが始まる内圧を求め、かしめ強度を評価した。また、上記の単３型電池缶相当の絞り缶に疑似充填剤としてアルカリ電解液を封入し、絶縁パッキンと封口蓋を装着し、かしめ加工により封口した後、温度３８℃、湿度９０％の雰囲気で４０日間貯蔵（恒温恒湿処理）し、封口部からの液漏れの有無を判定した。耐時効性は、絞り缶缶底のストレッチャーストレイン（ＳＳ）の発生の有無により評価した。これらの結果を表５に示す。
【００４５】
表５に示すように、本発明例の鋼板は、かしめ強度が高く、液漏れが皆無であり、比較例に比べ、封口部密封性、多段絞り性、面内異方性、耐時効性のいずれにおいても優れていることがわかる。
【００４６】
【表３】

【００４７】
【表４】

【００４８】
【表５】

【００４９】
【発明の効果】
以上説明したように、本発明によれば、封口部密封性の優れた２ピース電池缶用鋼板およびその製造方法を得ることが可能となる。
【図面の簡単な説明】
【図１】電池用絞り缶を示す断面図。
【図２】かしめ強度に対する二次圧延圧下率の影響を示す図。
【符号の説明】
１……電池用絞り缶
２……封口蓋
３……絶縁パッキン
４……封口部
５……エアー封入口[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to a steel plate for battery cans and a method for producing the same, and more particularly to a steel plate for two-piece battery cans excellent in sealing performance suitable for battery cans formed by multistage deep drawing and a method for producing the same.
[0002]
[Prior art]
For secondary batteries such as alkaline manganese dry batteries and lithium batteries, and secondary batteries such as Ni-Cd batteries and Ni-MH batteries, so-called two-piece battery cans are used, in which the steel plate used as a material is processed into a cylindrical shape by press molding. ing. These two-piece cans are further divided into DI cans and drawn cans according to the molding method.
[0003]
DI cans are made by so-called DI molding, which consists of a step of punching a steel plate of about 0.4 mm into a circular blank and deep drawing into a cylindrical shape and a step of ironing the cylindrical parts with a plurality of ironing dies. It is a battery can. The DI can can be made thinner than the steel plate thickness as a raw material by ironing the can wall, and the final can wall thickness can be reduced to about 0.15 mm. As a conventional technique related to a battery manufactured by such DI molding, for example, there is a technique disclosed in Japanese Patent Publication No. 7-99686.
[0004]
On the other hand, a drawn can is a battery can that is made by multistage drawing of about 5 to 10 steps after first cupping, and it is difficult to reduce the can wall thickness like a DI can. The can wall thickness is about the same as the steel plate thickness. In addition, since battery cans are required to have excellent corrosion resistance that can withstand the alkalinity of the battery contents, those that are Ni-plated are generally used. Both a post-plating method (so-called barrel plating) to be performed and a pre-plating method for press-forming a Ni-plated steel sheet are used. As conventional techniques relating to battery cans manufactured by such drawing, for example, there are techniques disclosed in Japanese Patent Application Laid-Open Nos. 55-131959 and 58-17661.
[0005]
[Problems to be solved by the invention]
In recent years, the need for improving the life of small batteries such as the above primary batteries and secondary batteries has increased further, and as one of the countermeasures, the can wall of the battery can is made thinner and the filler capacity is increased. Attempts have been made to increase battery capacity. In the case of DI cans, it is relatively easy to reduce the thickness of the can wall as described above, but in the case of a drawn can, the thickness of the can wall is slightly thicker than the bottom of the can in normal drawing. It is difficult to thin the can wall by molding. Therefore, with respect to the steel plate for a drawing can, there is a strong demand for gauge down of the steel plate itself before forming.
[0006]
However, if the steel plate is gauged down, the wall thickness of the can can be reduced and the battery capacity can be increased, but the thickness of the sealing plate is naturally reduced, so that the caulking strength of the sealing portion is weakened and the liquid leakage of the contents is reduced. A new problem of increased risk arises. At present, a fundamental solution to such a problem has not yet been found.
[0007]
The present invention has been made in view of such circumstances, and has an excellent sealing portion sealing property even when gauge down, and is particularly effective when formed by multistage drawing. And it aims at providing the manufacturing method.
[0008]
[Means for Solving the Problems]
In order to improve the sealing performance of the sealing part, it is necessary to increase the strength of the sealing part and to increase the caulking strength. However, unlike a DI can, a drawn can has little work hardening during can manufacturing, so the strength of the steel sheet itself is reduced. Need to increase. However, simply increasing the strength of the steel sheet reduces the deep drawability and tends to cause forming defects such as cracks in a multistage drawing process. In addition, the in-plane anisotropy deteriorates, the ear of the can end becomes larger, the trim margin becomes larger, the thickness distribution in the circumferential direction of the sealing portion becomes uneven, and the caulking strength becomes uneven. The risk of dripping liquid increases.
[0009]
Accordingly, the present inventors have earnestly solved the above-mentioned problem of obtaining a steel plate for a two-piece battery can with high caulking strength and excellent sealing performance without deteriorating deep drawability and in-plane anisotropy. As a result of repeated investigations, the above problem is solved by reducing the amount of C compared to conventional low C steel and work hardening the medium and low C steel controlled within the appropriate range by secondary rolling after annealing. I found that I can do it. Furthermore, it discovered that the sealing part sealing property improved more by adding B.
[0010]
This invention is made | formed based on the above knowledge, and 1st invention is 0.01% <C <0.03% and 0.02% <sol. Al ≦ 0.15%, N ≦ 0.0035% , Si ≦ 0.02%, 0.1% ≦ Mn ≦ 1.0%, P ≦ 0.02%, S ≦ 0.02%, balance Fe and Provided is a steel plate for a two-piece battery can having a sealing portion excellent in sealing performance, characterized by having a steel composition composed of inevitable impurities and being work-hardened by secondary rolling after annealing.
[0011]
A second invention provides a steel plate for a two-piece battery can with excellent sealing portion sealing performance, characterized in that in the first invention, 0.0005% ≦ B ≦ 0.003% is further contained.
[0012]
A third invention is a steel plate for a two-piece battery can with excellent sealing performance, having at least a Ni plating layer or a Fe-Ni alloyed plating layer on both surfaces of the steel plate of the first or second invention. I will provide a.
[0013]
The fourth aspect of the present invention is 0.01% <C <0.03%, 0.02% ≦ sol. Al ≦ 0.15%, N ≦ 0.0035% , Si ≦ 0.02%, 0.1% ≦ Mn ≦ 1.0%, P ≦ 0.02%, S ≦ 0.02%, balance Fe and A two-piece battery with excellent sealing performance, characterized by subjecting a hot-rolled steel sheet having an inevitable impurity composition to cold rolling, followed by continuous annealing, followed by secondary rolling at a rolling reduction of 10 to 25 %. A method for producing a steel plate for cans is provided.
[0014]
The fifth invention relates to 0.01% <C <0.03%, 0.02% ≦ sol. Al ≦ 0.15%, N ≦ 0.0035%, 0.0005% ≦ B ≦ 0.005% , Si ≦ 0.02%, 0.1% ≦ Mn ≦ 1.0%, P ≦ 0.02. %, S ≦ 0.02%, hot-rolled steel sheet having a steel composition composed of the balance Fe and inevitable impurities is cold-rolled and then continuously annealed, followed by secondary rolling at a rolling reduction of 10 to 25 %. The manufacturing method of the steel plate for 2 piece battery cans which was excellent in the sealing part sealing property made.
[0015]
The sixth invention is a two-piece excellent sealing part sealing property characterized in that at least a Ni plating layer or a Fe—Ni alloyed plating layer is formed on both surfaces of the steel plate produced in the fourth or fifth invention. A method for producing a steel plate for a battery can is provided.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The details of the present invention, the details of the present invention, and the reasons for limitation will be described below.
The inventors of the present invention attempted to increase the caulking strength of the sealing portion of the battery can, and considered that it was necessary to increase the strength of the steel plate in order to improve the sealing performance of the sealing portion, and studied the effect of increasing the strength of the steel plate. At that time, in the DI can, focusing on the fact that the part corresponding to the sealing part was work-hardened by ironing at the time of can-making, we examined the work hardening of the steel sheet before forming by secondary rolling to increase the strength. .
[0017]
0.04% C steel, 0.02% C steel, 0.02% C-B added steel, and 0.009% steel shown in Table 1 were subjected to temper rolling or secondary rolling to obtain a sheet thickness of 0 Finished to 20 mm (total cold pressure ratio 89%), Ni plating with a thickness of 4 μm was applied to both surfaces of the steel plate, and heat diffusion treatment was performed at 650 ° C. for 30 seconds to form an Fe—Ni alloyed plating layer. The yield strength, ear rate, aging resistance, multistage drawability, and sealability of the sealing part after canning were investigated. The yield strength of the steel sheet was measured by a tensile test, a circular blank having a diameter of 45 mmφ was punched out, deep-drawn at a drawing ratio of 1.67, and the ear rate was measured. The ear ratio was expressed as a percentage obtained by measuring the molding height at each position in the circumferential direction and dividing the difference between the maximum value and the minimum value of the molding height by the minimum height value. Further, a circular blank having a diameter of 55 mmφ was punched out, and a drawn can corresponding to an AA type battery can having a final diameter of 13.85 mm was produced by multistage drawing in 10 steps. After trimming the can ends of these cans, an insulating packing sealing lid was attached to the opening as shown in FIG. 1 and sealed by caulking. Further, a hole was opened at the bottom of the can, and the pressurized air was sealed. The internal pressure at the moment when the air leaked from the sealing portion started was determined, and the caulking strength was evaluated. The aging resistance was evaluated based on whether or not stretcher strain (SS) was generated on the bottom of the can.
[0018]
These results are shown in Table 2. In the case where the conventional 0.04% C steel is not subjected to secondary rolling (A1), the yield strength of the steel sheet is low, so that the caulking strength, that is, the sealing performance of the sealing portion is inferior. On the other hand, when the secondary rolling is performed (A2), the yield strength of the steel sheet is high but the ear ratio (in-plane anisotropy) is inferior, and as a result, the caulking strength is sufficiently improved instead of the steel sheet strength. Absent. Furthermore, it can be seen that some cracks occur during multi-stage drawing, and the drawability is poor.
[0019]
In contrast, when 0.02% C steel is not subjected to secondary rolling (B1), the strength is low and sealability is inferior similarly to low C steel, but when it is work hardened by secondary rolling (B2). ) All have good ear ratio, multi-stage drawability, and caulking strength. For the 0.02% C—B added steel (C1, 2), the steel sheet yield strength shows almost the same result as the 0.02% C steel. However, the caulking strength is further improved. This is considered to be due to the fact that the generation of fine cracks on the outer surface of the caulking portion bending R is suppressed by the addition of B, that is, the addition of B.
[0020]
On the other hand, in the case of 0.009% steel with a further reduced amount of C, SS is observed at the bottom of the can even when secondary rolling is performed (D2), indicating that the aging resistance is inferior.
[0021]
[Table 1]

[0022]
[Table 2]

[0023]
Next, the component composition in the present invention will be described.
The steel sheet of the present invention is 0.01% <C <0.03%, 0.02% ≦ sol. Al ≦ 0.15%, N ≦ 0.0035% , Si ≦ 0.02%, 0.1% ≦ Mn ≦ 1.0%, P ≦ 0.02%, S ≦ 0.02%, balance Fe and It has a steel composition consisting of inevitable impurities . Further, 0.0005% ≦ B ≦ 0.005% B is further contained. Hereinafter, the reason for limiting the composition in this way will be described.
[0024]
C: C is an extremely important element in order to ensure excellent sealability of the sealing portion without degrading deep drawability and in-plane anisotropy, and must be controlled within an appropriate range. When the C content is 0.03% or more, the deep drawability deteriorates, and molding defects such as cracks are likely to occur in a multistage drawing process, and the in-plane anisotropy deteriorates, resulting in a sealing portion. The sealing performance is reduced. Steel sheets that have been subjected to secondary rolling after annealing of conventional low C steel are inferior in deep drawability and in-plane anisotropy compared to steel sheets that have been subjected to pressure regulation of about 1.5% after annealing. This is particularly noticeable in steel sheets with a reduced thickness, that is, gauged down. In order to avoid such characteristic deterioration when the secondary rolling is performed, the C amount needs to be less than 0.03%. Therefore, in the present invention, the C amount is made less than 0.03%. On the other hand, when the C content is 0.01% or less, the aging resistance deteriorates rapidly, the rolling reduction of the secondary rolling is relatively low, and when heat diffusion treatment is performed after Ni plating, a stretcher is formed around the bottom of the can. Strain (SS) may occur, which is not preferable. Therefore, in the present invention, C is made more than 0.01% in order to reliably suppress the occurrence of SS. Among these ranges, a range of 0.015% or more and 0.025% or less is more preferable.
[0025]
sol. Al: sol. Al is an important element in order to keep the deep drawability and in-plane anisotropy of the secondary rolled steel together with the N amount described later. so1. Al needs to be added in an amount of 0.02% or more for deoxidation and in order to precipitate N as AlN and reduce the amount of dissolved N. On the other hand, even if a large amount of Al exceeding 0.15% is added, these effects are saturated, and fine alumina inclusions are likely to remain, and molding defects such as cracks due to inclusions are likely to occur. Become. Therefore, in the present invention, sol. The Al content is 0.02% or more and 0.15% or less.
[0026]
N: It is desirable to reduce N as much as possible. When N is large, solid solution N tends to remain even if 0.02% or more of Al is added, and the deep drawability and in-plane anisotropy of the steel sheet after secondary rolling can be kept good. It becomes difficult. Therefore, in the present invention, in order to avoid these adverse effects, the N amount is made 0.0035% or less. Furthermore, it is still more desirable to set it as 0.0025% or less.
[0027]
B: B is an element added as necessary to further improve the sealing performance of the sealing portion. When the sealing part is caulked, fine cracks may be generated on the outer surface of the bend R, and if this becomes a starting point and a crack reaching the iron base is formed in the Ni layer, the sealing part sealing performance is reduced, and Corrosion resistance may also decrease. Such fine cracks in the outer surface layer of the bending R are generated starting from relatively large carbides precipitated at the grain boundaries of the steel sheet. When B is added, since B is segregated at the grain boundary, the carbide precipitated at the grain boundary is reduced, and the carbide is dispersed and precipitated relatively finely within the grain. As a result, the addition of B suppresses the deterioration of the sealing performance due to the fine cracks. B also has an action of precipitating N as BN to reduce the solid solution N, and is effective in improving the deep drawability and in-plane anisotropy of the secondary rolled material. In order to exert these B addition effects, addition of 0.0005% or more is necessary. On the other hand, even if excessive addition exceeding 0.003% is performed, these effects are saturated and, conversely, solid solution Adverse effects such as a decrease in deep schooling due to B residues will become apparent. From the above, in the present invention, when B is added, the amount is made 0.0005% or more and 0.003% or less. Among these, in order to exhibit the B addition effect particularly remarkably, it is desirable that the content be 0.0010% or more and 0.0025% or less.
[0029]
Si: Si is an element that remains in the steel as an impurity component even when no intentional addition is performed, and deteriorates the corrosion resistance of the steel sheet and the adhesion of the Ni plating. In order to ensure good corrosion resistance, It is desirable that the content be 0.02% or less.
[0030]
Mn: Mn prevents hot cracking of the slab by precipitating S in the steel as MnS. In order to precipitate and fix S, it is desirable to add 0.1% or more. Mn is an element effective for increasing the strength and fineness of the steel sheet, and an appropriate amount may be added as necessary. However, if Mn is added excessively, the corrosion resistance of the steel sheet and the adhesion of Ni plating deteriorate, so even if it is added, the amount is preferably made 1.0% or less.
[0031]
P: P segregates at the ferrite grain boundaries, embrittles the grain boundaries, and lowers the workability during drawing. Moreover, it is an element which reduces the adhesiveness of Ni plating, and it is preferable that the content is as small as possible, and it is desirable to make it 0.02% or less.
[0032]
S: S is preferably as small as possible from the viewpoint of preventing hot cracking of the slab, and is preferably 0.02% or less.
[0033]
The steel sheet of the present invention has the above steel composition and is characterized by being work hardened by secondary rolling after annealing. Even when the steel sheet for battery cans made by multi-stage drawing is gauged down, in order to secure sufficient sealing part sealing performance by improving the caulking strength, the steel sheet after annealing is secondary. Roll and work harden to increase the strength of the steel sheet. However, when a conventional low-carbon steel sheet is simply strengthened by secondary rolling, the deep drawability and in-plane anisotropy deteriorate as described above, resulting in poor sealing and non-uniform caulking strength. In order to bring about a fall, it is necessary to use the steel which reduced C amount compared with the conventional low C steel, and was controlled to the appropriate range as a raw material.
[0034]
In addition to work hardening, there are various methods such as precipitation strengthening, transformation structure strengthening, grain refinement strengthening, and solid solution strengthening as means for increasing the strength of the steel sheet. However, in precipitation strengthening, in order to ensure sufficient strength, it is necessary to add a carbonitride-forming element such as Nb to disperse and precipitate a large amount of carbonitride, and these carbonitrides deteriorate the corrosion resistance. And the adhesion of the plating is also deteriorated. In addition, the deep drawability of the steel sheet is also deteriorated. Further, in order to strengthen the transformation structure, it is necessary to perform high-temperature annealing and rapid cooling during annealing, and it is difficult to produce an ultrathin gauge down material of about 0.2 mm. That is, drawing, meandering, and breakage are likely to occur in the CAL during continuous smelting, making it difficult to increase the strength of an ultrathin material stably industrially. Further, the fine grain strengthening has a small strengthening ability, and a sufficient strength cannot be obtained. Furthermore, solid solution strengthening has relatively few problems as described above. However, in order to obtain sufficient strength, when a large amount of C or N having a large strengthening ability is added, deep drawability and in-plane difference are different. The directivity deteriorates, and when a large amount of P and Si is added, the plating adhesion and deep drawability are greatly deteriorated. Mn has a relatively small adverse effect, but since the strengthening ability is small, sufficient strength cannot be ensured with Mn alone. Further, when Mn is added in a large amount exceeding 1%, the same adverse effect as P and Si becomes remarkable.
[0035]
On the other hand, in the case of work hardening by secondary rolling of a steel sheet in which the C amount is controlled within an appropriate range, there is no problem as described above, and the occurrence of stretcher strain due to aging during drawing is suppressed.
From the above, in the present invention, it is essential to work harden a steel sheet of 0.01% <C <0.03% by secondary rolling after annealing.
[0036]
Next, the manufacturing method of the steel plate of this invention is demonstrated.
After the melting of the converter, the slab obtained by continuous casting is subjected to rough rolling, or is directly inserted into a hot finishing mill without rough rolling and hot rolling is performed. Slab heating temperature can be about 1050-1250 degreeC in the range currently performed normally. The hot rolling finishing temperature is preferably not less than the Ar ₃ transformation point. When the hot-rolling finishing temperature is lower than the Ar ₃ transformation point, a texture is formed on the hot-rolled sheet, and surface crystal grains may be coarsened or the processed structure may remain. As a result, non-uniformity of the steel plate thickness is likely to occur, resulting in a decrease in sealing performance due to non-uniform circumferential plate thickness of the battery can sealing portion. The coiling temperature can be about 500 to 700 ° C., but when B is not added, it is desirable that the temperature is 600 ° C. or higher in order to reduce the solid solution N.
[0037]
Further, the hot-rolled steel sheet is pickled and cold-rolled, followed by continuous annealing. In order to reduce the in-plane anisotropy, the primary cold pressure ratio is desirably about 80 to 90%, and the total cold pressure ratio including the secondary rolling described later is desirably about 83 to 93%. Here, the total cold pressure ratio represents (hot rolled finish thickness-plate thickness after secondary rolling) / hot rolled finish thickness. The annealing temperature for continuous annealing is preferably about the recrystallization temperature or higher and about 750 ° C. or lower in order to suppress deterioration of workability due to remaining unrecrystallized structure and rough skin due to excessive grain growth. .
[0038]
Further secondary rolling is performed after tempering. Secondary rolling is a process required to increase the strength of the steel sheet, to increase the caulking strength of the sealed portion after forming into the battery can, and to improve the sealing performance of the sealed portion. FIG. 2 shows the influence of the rolling reduction of the secondary rolling on the caulking strength. It can be seen from the figure that if the rolling reduction of the secondary rolling is less than 5%, sufficient caulking strength cannot be obtained. Further, when the rolling reduction of the secondary rolling exceeds 30%, the caulking strength tends to decrease. When rolling at a high-pressure ratio exceeding 30%, the yield strength of the steel sheet becomes too high and the shrinking back after caulking of the sealing part becomes large, and conversely, the caulking strength decreases and the liquid may leak. Becomes larger. In this case, even if the total rolling reduction is about 83 to 93%, it becomes difficult to sufficiently reduce the in-plane anisotropy, and the sealing performance is deteriorated due to the uneven thickness distribution in the circumferential direction of the sealing portion. Becomes obvious. Further, the deep drawability deteriorates, and molding defects such as cracking become apparent during multistage drawing. From these things, the rolling reduction of secondary rolling shall be 10-25 % .
[0039]
Usually, a corrosion-resistant coating layer such as a plating layer and / or an alloying plating layer for ensuring good corrosion resistance after canning is formed on both surfaces of the battery steel sheet. The applied plating layer or alloyed plating layer is not particularly limited as long as it can ensure corrosion resistance, and is obtained by thermally diffusing a single layer or multiple layers and / or this plating layer. What is necessary is just to form the obtained alloying plating layer on both surfaces of a steel plate. However, in order to obtain excellent corrosion resistance of the battery contents against alkali, it is desirable to provide at least a Ni plating layer or a Fe—Ni alloyed plating layer. This Fe—Ni alloyed plating layer is obtained by subjecting the Ni plating layer to thermal diffusion treatment, and may be obtained by alloying the entire Ni plating layer (Fe—Ni). An alloy obtained by alloying only the interface may be used. By generating such an alloy layer, the corrosion resistance is further improved.
[0040]
As described above, there are two types of battery cans manufactured by multi-stage drawing, that is, a post-plating method in which Ni plating is performed after press forming and a pre-plating method in which Ni-plated steel plate is press-formed. It can be applied to both, and the same effect can be exhibited.
[0041]
In particular, in order to ensure excellent corrosion resistance in the latter case, it is desirable to provide at least one Ni plating layer and / or Fe—Ni alloyed plating layer on both sides of the steel sheet. Further, an Sn plating layer can be provided on the Ni plating layer and / or the Fe—Ni alloying plating layer to further improve the corrosion resistance. The Ni plating thickness is not particularly limited, but it is desirable that both sides have a thickness of about 1 to 5 μm, and both the equal thickness plating and the differential thickness plating may be used. Moreover, although the heating conditions at the time of heat-diffusion-processing a Ni plating layer are not specifically limited, It is preferable to set it as about 30 second to about 3 minutes at 600-750 degreeC. In addition, after the thermal diffusion treatment, pressure adjustment of about 0.5 to 2% may be performed in order to adjust the surface roughness and suppress the generation of SS due to aging. Furthermore, the corrosion resistance is further improved by performing Ni plating again after this pressure adjustment.
[0042]
【Example】
After the steel having the composition shown in Table 3 was melted in a converter, it was made into a slab by continuous casting and hot rolled at a heating temperature of 1200 to 1230 ° C, a finishing temperature of 860 to 900 ° C, and a winding temperature of 600 to 640 ° C. Then, after pickling, cold rolling, and further performing continuous annealing, secondary rolling or temper rolling under the conditions shown in Table 4, finishing to a thickness of 0.25, 0.20, 0.18 mm, both sides of the steel plate 4 μm thick Ni plating was applied. The total cold pressure ratio was 86 to 90%. About some steel plates, after Ni plating, the thermal diffusion process was performed at 650 degreeC for 1 minute, and the Fe-Ni alloying plating layer was formed.
[0043]
These steel sheets were subjected to a tensile test to measure the yield strength, and a circular blank having a diameter of 45 mmφ was punched out and deep-drawn at a drawing ratio of 1.67 to measure the ear rate. The ear ratio was expressed as a percentage obtained by measuring the molding height at each position in the circumferential direction and dividing the difference between the maximum value and the minimum value of the molding height by the minimum height value. Further, a circular blank having a diameter of 55 mmφ was punched out, and a drawn can corresponding to an AA type battery can having a final diameter of 13.85 mm was produced by multistage drawing in 10 steps.
[0044]
After trimming the can ends of these cans, as shown in FIG. 1, an insulating packing and a sealing lid are attached to the opening, and after sealing by caulking, a hole is made in the bottom of the can to increase the pressure. Sealing was performed, the internal pressure at which air leakage from the sealing portion began was determined, and the caulking strength was evaluated. In addition, an alkaline electrolyte as a pseudo filler is enclosed in the above-mentioned AA size battery can, and an insulating packing and a sealing lid are attached. After sealing by caulking, the temperature is 38 ° C. and the humidity is 90%. Was stored for 40 days (constant temperature and humidity treatment), and the presence or absence of liquid leakage from the sealing portion was determined. The aging resistance was evaluated by the presence or absence of the occurrence of stretcher strain (SS) on the bottom of the can. These results are shown in Table 5.
[0045]
As shown in Table 5, the steel sheet of the present invention example has high caulking strength and no liquid leakage. Compared with the comparative example, the sealing part sealing property, multistage drawing property, in-plane anisotropy, and aging resistance It turns out that it is excellent in any.
[0046]
[Table 3]

[0047]
[Table 4]

[0048]
[Table 5]

[0049]
【The invention's effect】
As described above, according to the present invention, it is possible to obtain a steel plate for a two-piece battery can with excellent sealing portion sealing performance and a method for manufacturing the same.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a battery can.
FIG. 2 is a graph showing the influence of secondary rolling reduction ratio on caulking strength.
[Explanation of symbols]
1 …… Battery can 2 …… Sealing lid 3… Insulating packing 4 …… Sealing part 5 …… Air filling port

Claims (6)

% By weight, 0.01% <C <0.03%, 0.02% ≦ sol. Al ≦ 0.15%, N ≦ 0.0035% , Si ≦ 0.02%, 0.1% ≦ Mn ≦ 1.0%, P ≦ 0.02%, S ≦ 0.02%, balance Fe and A steel plate for a two-piece battery can with excellent sealing performance, having a steel composition composed of inevitable impurities and being work-hardened by secondary rolling after annealing.   The steel plate for a two-piece battery can with excellent sealing portion sealing performance according to claim 1, further comprising B in an amount of 0.0005% ≤B≤0.003%.   A steel plate for a two-piece battery can with excellent sealing performance, comprising at least a Ni plating layer or a Fe-Ni alloyed plating layer on both surfaces of the steel plate according to claim 1 or 2. % By weight, 0.01% <C <0.03%, 0.02% ≦ sol. Al ≦ 0.15%, N ≦ 0.0035% , Si ≦ 0.02%, 0.1% ≦ Mn ≦ 1.0%, P ≦ 0.02%, S ≦ 0.02%, balance Fe and after cold rolling the hot-rolled steel plate having a steel composition consisting of unavoidable impurities, continuous annealing, excellent two-piece then sealing portion sealing properties, characterized in that performing the secondary rolling 10% to 25% of reduction ratio Manufacturing method of steel sheet for battery can. % By weight, 0.01% <C <0.03%, 0.02% ≦ sol. Al ≦ 0.15%, N ≦ 0.0035%, 0.0005% ≦ B ≦ 0.003% , Si ≦ 0.02%, 0.1% ≦ Mn ≦ 1.0%, P ≦ 0.02. %, S ≦ 0.02%, hot-rolled steel sheet having a steel composition composed of the balance Fe and inevitable impurities is cold-rolled and then continuously annealed, followed by secondary rolling at a rolling reduction of 10 to 25 %. The manufacturing method of the steel plate for 2 piece battery cans which was excellent in sealing part sealing property.   6. Two-pieces with excellent sealing performance, wherein at least a Ni plating layer or a Fe—Ni alloyed plating layer is formed on both surfaces of a steel plate manufactured by the manufacturing method according to claim 4 or 5. Manufacturing method of steel sheet for battery can.

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