JP3976396B2 - High-strength steel plate for drums, method for producing the same, and steel drum - Google Patents

Description

【００５４】
【表２】

【００５５】
本発明範囲の鋼板（鋼板No.1-2〜No.1-4）は、７μm 以下の平均結晶粒径を有し、かつ41％以上の伸びを示している。さらに、延性の低下を伴うことなく常温強度、および 600℃における高温強度が、Nb無添加の冷延鋼板（従来例）に比べ増加している。また、本発明例は曲げ特性も良好であり、巻き締め性に問題はなかった。
【００５６】
ついで、これら鋼板から天板、地板をプレス加工した。一方、胴板を円筒状に曲げ成形し両端部をシーム溶接して缶胴部とし、缶胴部の両端に天板、地板を巻き締め（２重巻締め方式）により装着し容量 200リットルの密封型ドラムとした。なお、外面には通常の塗装（エポキシ系塗料）を施し、内面は燐酸亜鉛による化成処理を施した。製缶に際し、製缶時の曲げ加工性、形状凍結性、溶接性等を調査し製缶性とした。
【００５７】
また、これらドラム缶について、強度特性を調査するため、内部を空のままとし、軸方向および円周方向から圧縮し、マクロな圧縮座屈を生じる荷重を座屈荷重として測定した。
また、これらドラム缶について内部に油類を充填し、-40 ℃に冷却し1.2mの高さから落下させ漏れおよび変形量を調査する落下試験を実施した。なお、落下試験における変形量は、従来例（鋼板No.1-5）の変形量を1.00とし、従来例に対する比で示している。なお、JIS に規定される室温における高さ 1.8ｍからの落下試験については、上記低温落下試験に合格するドラム缶であれば問題なく合格することを確かめたので省略した。
【００５８】
これらの結果を缶体特性として表２に示す。
表２から、本発明例（鋼板No.1-2〜No.1-4）は、製缶性も問題なく、強度特性試験における座屈荷重も比較例にくらべ高く、さらに低温の落下試験における変形量も従来例（鋼板No.1-5）にくらべ減少し、缶体の高強度化が達成されていることがわかる。また、低温の落下試験では、本発明例で、高強度化したにもかかわらず漏れを生じることもなく、内容物を安全に確保でき巻締め部の信頼性が向上していることがわかる。本発明の鋼板では、２重巻締め、３重巻締めといった巻締め方式によらず、また、低温という厳しい条件下においても常に巻締め部の信頼性を向上させることができる。
（実施例２）
0.035 wt％Ｃ−0.01wt％Si−0.25wt％Mn−0.006wt ％Ｐ−0.005wt ％Ｓ−0.0030wt％Ｎ−0.035wt ％Al−0.015wt ％Nbを含み残部Feおよび不可避的不純物からなる鋼素材（スラブ）を用い、表３に示す条件で熱間圧延を施し、圧延終了後水冷し、表３に示す温度で巻取り3.4 〜2.5 mm厚の熱延板とし、ついで、これら熱延板に酸洗処理を施したのち、表３に示す条件で冷間圧延を施し冷延板とした。その後これら冷延板に、表３に示す条件で連続焼鈍を施し、酸洗および表３に示す条件で調質圧延を施し、 1.0mm厚の冷延焼鈍板とした（鋼板No.2-1〜2-7 ）。なお、連続焼鈍においては、過時効帯の炉温を 350℃以下として実質的に過時効処理なしとした。
【００５９】
なお、0.035 wt％Ｃ−0.01wt％Si−0.25wt％Mn−0.006wt ％Ｐ−0.005wt ％Ｓ−0.0020wt％Ｎ−0.035wt ％Al− 0.005wt％Nbを含み残部Feおよび不可避的不純物からなるスラブを用い、表３に示す条件で熱間圧延を施し、圧延終了後水冷し、表３に示す温度で巻取り 2.6mm厚の熱延板とした（鋼板No.2-8）。ついで、この熱延板に酸洗を施したのち、冷間圧延を施して 1.0mm厚の冷延板とした。この冷延板に、焼鈍として、700 ℃×40sec の均熱を施したのち50℃/sの冷却速度で冷却し400 ℃×60sec の過時効処理を施し、冷延焼鈍板として比較例とした。
【００６０】
これら冷延鋼板から実施例１と同じ要領で天板、地板を加工し、胴板を曲げ成形し両端部をシーム溶接して缶胴部とし、缶胴部の両端に天板、地板を巻き締めにより装着し容量200 リットルの密封型ドラムとし、製缶性を調査した。製缶後、外面にはエポキシ系塗装を施し、内面には化成処理のみを施した。
これらドラム缶について、常温（15℃）で、ドラム缶外部から、円周方向の圧縮応力となるように集中荷重を負荷して、その際生じる缶体の変形量を測定した。その結果を表３に示す。
【００６１】
【表３】

【００６２】
本発明範囲の鋼板を用いたドラム缶（鋼板No.2-1〜No.2-7）では、荷重負荷により生じる変形量は、比較例（鋼板No.2-8) くらべ著しく減少することがわかる。すなわち、顕著な高強度化が達成されている。また実施例１と同様に低温での落下試験も実施したが洩れ等を生ずることはなかった。
なお、ドラム缶内部の圧力を高くした場合の缶体の変形量についても、測定した。外部からの圧縮応力負荷に比べ大きな相違はみられないが、本発明例のドラム缶の変形量が比較例の変形量にくらべ少ない傾向は同様に確認できた。
（実施例３）
表４に示す化学組成の鋼を転炉で溶製し、連続鋳造法でスラブとしたのち、表５に示す条件で熱間圧延を施し、圧延終了後水冷しあるいは水冷なしとし、表５に示す温度で巻取り2.9 〜3.4 mm厚の熱延板とし、ついで、これら熱延板に酸洗処理を施したのち、表５に示す条件で冷間圧延を施し冷延板とした。その後これら冷延板に、表５に示す条件で連続焼鈍を施し、表５に示す条件で調質圧延を施し、1.0 mm厚の冷延焼鈍板とした。なお、連続焼鈍は過時効処理なしとした。
【００６３】
これら冷延鋼板を胴板、天板に加工したのち、胴板を曲げ成形し両端部をシーム溶接した。なお、胴板のシーム溶接条件を最適化するため、従来の低炭素アルミキルド鋼板（1.0mm 厚）を溶接する条件（溶接１次電流： 220Ａ、溶接速度：15ｍ／min 、シリンダー圧力で調整する電極加圧力：530kgf（シリンダー圧力3.0kgf/cm²相当））を基本として、１次溶接電流を変化した溶接条件で胴板シーム溶接を行い、通常の製缶工程にしたがい、フランジ成形および輪帯のエキスパンド成形を行って割れ等の不具合発生を調査し、不具合発生のない適正溶接電流の範囲の幅を決定した。
【００６４】
また、適正範囲内の溶接電流でシーム溶接を行い、容量200 リットルの密封型ドラム缶（天板、地板とも２重巻き）に製缶した。これらドラム缶について、缶体圧縮試験（軸方向の静的圧縮試験）を実施し、静的圧潰強度を求めた。
それらの結果を、鋼板の結晶粒径、機械的特性とともに表５に示す。
【００６５】
【表４】

【００６６】
【表５】

【００６７】
表５から、本発明例（鋼板No.3-1〜No.3-3）は、従来例（鋼板No.3-6）に比べ高い強度を有しているにもかかわらず、従来例と同等の溶接可能電流範囲を有し、製缶性、溶接性ともに問題を生じていない。また、本発明例は、静的圧潰強度も従来例に比べ高く、鋼板強度の増加と対応する。
本発明範囲の高強度冷延鋼板をドラム缶用素材として適用すれば、溶接性の劣化を伴わず缶体強度の増加が達成できる。とくに、本発明例の巻締め部は、同一変形量を強制的に与えた場合でも、より大きな歪域まで気密性を確保できる。
（実施例４）
表６に示す化学組成の鋼を転炉で溶製し、連続鋳造法で 260mm厚のスラブ（鋼素材）とした。ついで、これらスラブを表７に示す条件で熱間圧延を施した後冷却し、表７に示す温度で巻取り、1.22mm厚の熱延板とした。ついで、これら熱延板に必要に応じ酸洗または調質圧延を施して最終仕上板厚1.20mm厚の熱延鋼板とした。
【００６８】
これら熱延鋼板について、結晶粒径、引張特性（常温および 600℃における引張強さ）、および曲げ特性・繰り返し曲げ特性を調査した。
結晶粒径（平均結晶粒径）は、鋼板圧延直角方向の断面について光学顕微鏡あるいは電子顕微鏡写真から求めた。また、同じ断面写真より黒皮厚を求めた。引張特性は、ドラム缶の成形時に円周方向となる方向から採取したJIS ５号試験片を用いた。600 ℃における引張強さは、通常の高温引張試験で得られた値を用いた。曲げ特性・繰り返し曲げ特性は、圧延直角方向から採取した曲げ試験片を密着曲げと密着曲げ戻しを行い破断の有無で評価した。なお、表中には破断無しを○、破断有りを×として表示している。
【００６９】
それらの結果を表７に示す。なお、比較として、実施例１で示したＤ鋼（表１）の冷延鋼板についての試験結果（表２の鋼板No.1-4）を従来例として示した。
【００７０】
【表６】

【００７１】
【表７】

【００７２】
本発明範囲の鋼板（本発明例No.4-1〜No.4-4）は、10μm 以下の平均結晶粒径を有し、かつ38％以上の伸びを示している。さらに、延性の低下を伴うことなく常温強度、および 600℃における高温強度が、比較例の鋼板（No.1-4）に比べ増加している。また、曲げ特性も良好であった。
ついで、これら鋼板から天板、地板をプレス加工した。一方、胴板を円筒状に曲げ成形し両端部をシーム溶接して缶胴部とし、缶胴部の両端に天板、地板を巻き締め（通常の２重巻締め方式）により装着し容量 200リットルの密封型ドラムとした。なお、外面にはエポキシ系塗料で塗装を施し、内面は燐酸亜鉛による化成処理を施した。製缶に際し、製缶時の曲げ加工性、形状凍結性、溶接性等を調査し製缶性とした。
【００７３】
また、これらドラム缶について、強度特性を調査するため、内部を空のままとし、軸方向および円周方向から圧縮し、マクロな圧縮座屈を生じる荷重を座屈荷重として測定した。
また、これらドラム缶についても内部に油類を充填し、-40 ℃に冷却し1.2mの高さから落下させ漏れおよび変形量を調査する落下試験を実施した。なお、落下試験における変形量は、従来例（No.1-5）の変形量を1.00とし、従来例に対する比で示している。
【００７４】
これらの結果を缶体特性として表７に示す。
表７から、本発明例は、製缶性も問題なく、強度特性試験における座屈荷重も比較例にくらべ高く、さらに低温の落下試験における変形量も比較例にくらべ減少し、缶体の高強度化が達成されていることがわかる。また、本発明例は、低温の落下試験で漏れを生じることもなく、内容物を安全に確保でき巻締め部の信頼性が確保されていることがわかる。本発明の鋼板では、２重巻締め、３重巻締めといった巻締め方式によらず、また低温という厳しい条件下においても常に巻締め部の信頼性を向上させることができる。
（実施例５）
0.032 wt％Ｃ−0.01wt％Si−0.15wt％Mn−0.003wt ％Ｐ−0.004wt ％Ｓ−0.045wt ％Al−0.017wt ％Nb−0.0021wt％Ｎを含み残部Feおよび不可避的不純物からなる鋼素材（スラブ）を用い、表８に示す条件で熱間圧延を施し、圧延終了後水冷し、表８に示す温度で巻取り熱延板とした。ついで、これら熱延板に酸洗を施したのち調質圧延を施し最終仕上板厚 2.3mm厚の熱延鋼板とした。
【００７５】
これら熱延鋼板から実施例４と同じ要領で天板、地板を加工し、胴板を曲げ成形し両端部をシーム溶接して缶胴部とし、缶胴部の両端に天板、地板を巻き締めにより装着し容量200lの密封型ドラムとし、製缶性を調査した。製缶後、外面にはエポキシ系の塗装を施した。
これらドラム缶について、常温（15℃）でドラム缶外部から、円周方向の圧縮応力となるように集中荷重を負荷して、その際生じる缶体の変形量を測定した。その結果を表８に示す。
【００７６】
【表８】

【００７７】
本発明範囲の鋼板を用いたドラム缶（本発明例No.5-1〜No.5-7）では、荷重負荷により生じる変形量は、高温および常温とも著しく減少することがわかる。本発明の範囲をはずれる比較例（鋼板No.5-8）では、荷重負荷により生ずる変形量が大きい。
なお、ドラム缶内部の圧力を高くした場合の缶体の変形量についても、測定した。外部からの圧縮応力負荷に比べ大きな相違はみられないが、本発明例のドラム缶の変形量が比較例の変形量にくらべ少ない傾向は同様に確認できた。
（実施例６）
表９に示す化学組成の鋼を転炉で溶製し、連続鋳造法でスラブとしたのち、表10に示す条件で熱間圧延を施して熱延板とし、酸洗処理および必要に応じ調質圧延を施して最終仕上板厚1.0mm の黒皮なし（表面にスケールの存在しない）熱延鋼板とした。
【００７８】
なお、0.035 wt％Ｃ−0.01wt％Si−0.18wt％Mn−0.006wt ％Ｐ−0.005wt ％Ｓ−0.045wt ％Al−0.0021wt％Ｎを含み残部Feおよび不可避的不純物からなるスラブ（表９鋼Ｊ）を用い、表10に示す条件で熱間圧延を施し、圧延終了後水冷した後、巻取り 2.9mm厚の熱延板とし、ついで、この熱延板に酸洗を施したのち、冷間圧延を施して1.01mm厚の冷延板とした。この冷延板に、焼鈍を施し、冷延焼鈍板として従来例（鋼板No.6-6）とした。焼鈍条件は、690 ℃×40sec の均熱を施したのち30℃/sの冷却速度で冷却し、実質的に過時効処理を施さなかった。
【００７９】
これら熱延鋼板（従来例は冷延鋼板）を用いて、胴板、天板を加工し、胴板を曲げ成形し両端部をシーム溶接した。なお、胴板のシーム溶接条件を最適化するため、従来の低炭素アルミキルド鋼板（1.0mm 厚）を溶接する条件（溶接１次電流： 220Ａ、溶接速度：15ｍ／min 、電極加圧力：530kgf（シリンダー圧力3.0kgf/cm²相当））を基本として、１次溶接電流を変化した溶接条件で胴板シーム溶接を行い、フランジ成形および輪帯のエキスパンド成形を行って割れ等の不具合発生を調査し、不具合発生のない適正溶接電流の範囲の幅を決定した。また、適正範囲内の溶接電流でシーム溶接を行い、容量200 リットルの密封型ドラム缶に製缶した。これらドラム缶について、缶体圧縮試験（軸方向の静的圧縮試験）を実施し、静的圧潰強度を求めた。それらの結果を、鋼板の結晶粒径、機械的特性とともに表５に示す。
【００８０】
【表９】

【００８１】
【表１０】

【００８２】
表10から、本発明例は、従来例に比べ高い強度を有しているにもかかわらず、従来例と同等の溶接可能電流範囲の幅（上下限はシフトする）を有し、製缶性、溶接性ともに問題を生じていない。また、本発明例は、静的圧潰強度も従来例に比べ高く、鋼板強度の増加と対応する。
本発明範囲の高強度熱延鋼板をドラム缶用素材として適用すれば、溶接性の劣化を伴わず缶体強度の増加が達成できる。とくに、本発明例の素材を用いたドラム缶の巻締め部は、同一変形量を強制的に与えた場合でも、より大きな歪域まで気密性を確保できることを確認した。これは低温での過酷な条件でも変わらない。
（実施例７）
表６に示す化学組成の鋼Ｋを転炉で溶製し、連続鋳造法でスラブとしたのち、表11に示す条件で熱間圧延を施して 1.1mm厚の熱延板とした。酸洗処理を省略し黒皮（表面スケール）付き熱延鋼板としたこれら鋼板を用いて前述の如く、通常のドラム缶製造工程にしたがって、容量200 リットルのドラム缶を製造した。なお、胴部のシーム溶接は、黒皮なしの場合にくらべ溶接電流を低下させて溶接した。また、ドラム缶への塗装は、化成処理を省略して直接塗装したが何ら問題は生じなかった。
【００８３】
これら熱延鋼板の製缶性について、熱延条件、結晶粒径、黒皮（酸化層）厚さおよび黒皮組成（マグネタイト量）とともに表11に示す。なお、マグネタイト量はＸ線回折法により測定した。
【００８４】
【表１１】

【００８５】
表11から、酸化層（黒皮）厚みが厚く、マグネタイト量が少ない場合には、製缶時やや剥離が多いが、酸化層厚が５μm 以下とすることにより、製缶時の剥離は問題ない程度まで減少した。また、酸化層厚が比較的厚い場合には、黒皮なしの場合にくらべ缶胴部のシーム溶接時、電極の損耗がやや増加する傾向がみられた。しかし、酸化層厚みを５μm 以下とすることにより、電極損耗は、冷延鋼板並となり、大幅に改善された。酸化層厚みを５μm 以下とするには、仕上げ圧延温度を920 ℃以下、仕上げ圧延終了から冷却開始までの時間を0.5sec以下、巻取り温度を600 ℃以下とすることが好適である。
【００８６】
このように、本発明の高強度冷延鋼板および高強度熱延鋼板をドラム缶素材として、ドラム缶を製造すれば、製缶性の低下もなく、常温および高温の缶体強度の増加が図れるため、板厚を薄くすることにより低コスト化、軽量化が図れる。さらに、巻締め部の信頼性も向上する。
以上、容量 200リットルの密封型ドラムについてのみ説明したが、さらに小容量のドラム缶に対して適用しても同様な効果があることはいうまでもない。
【００８７】
【発明の効果】
本発明によれば、製缶性の低下を伴うことなく、ドラム缶の大幅な強度増加が達成でき、内容物に対する信頼性が向上し、再生利用回数の大幅な増加が見込めるなど産業上格段の効果を奏する。さらに、鋼板の薄肉化が達成でき、製缶コストの低減および軽量化にも寄与できるという効果もある。また、本発明によれば、缶胴部のシーム溶接性、およびその後の伸びフランジ特性が顕著に改善され、さらに、低温における衝撃的な応力負荷に対しても液洩れ等の発生はなく、巻締め部の信頼性が著しく向上するという効果が期待できる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a steel drum can, and more particularly to a hot-rolled steel sheet, a cold-rolled steel sheet, and methods for producing the same suitable as a material for a steel drum can.
[0002]
[Prior art]
Steel drums can be broadly classified into two types: open drums defined as steel open drums in JIS Z 1600 and sealed drums defined as liquid steel drums in JIS Z 1601. These drums are composed of a top plate, a base plate, and a body plate. In a sealed drum, a disk-shaped top plate and a base plate are wound around both ends of a body plate that is bent into a cylindrical shape and joined by seam welding. In the open type drum, only the body plate and the base plate are wound and the top plate is manufactured to be detachable. These drums are subjected to chemical conversion treatment or coating on the outer surface and, if necessary, the inner surface.
[0003]
Drum cans require precision of the cans and soundness of welded parts, joints, and tightened parts, and JIS standards stipulate that airtight tests (water pressure tests), drop tests, stack tests, etc. should be performed. . In addition, deformation when receiving external force during transportation causes troubles in stacking and the like, and the appearance is also impaired.
The steel plate used as the drum material is a hot rolled mild steel plate and steel strip specified in JIS G 3131, or a cold rolled steel plate or steel strip specified in JIS G 3141, and its thickness is 0.5. ˜1.6 mm, for example, a commonly used 200 liter sealed drum (first grade H class) is 1.6 mm.
[0004]
Generally, a low-carbon aluminum-killed cold-rolled steel box annealing material or a continuous annealing material is used as a material, and its typical composition is 0.05 to 0.10% C-0.2 to 0.5% Mn- to 0.05% Si-0.04 in weight ratio. -0.10% Al-0.0015-0.0030% N. Further, this steel sheet has yield stress (YS): 225 MPa, tensile strength (TS): 340 MPa, and elongation (EL): about 42%. In addition, although a ratio is small, a hot-rolled material may also be applied to a drum can material with some thick plate thickness.
[0005]
[Problems to be solved by the invention]
Recently, attempts have been made to reduce the plate thickness of drum can materials in order to reduce can manufacturing costs. For that purpose, the steel plate strength must be increased to ensure the strength of the can body. However, in order to increase the strength of the steel plate for drums, in addition to ensuring the weldability and formability that are generally required, there are the following problems that must be solved.
[0006]
(1) Improvement of tightening performance
In general, increasing the strength of a steel sheet is accompanied by a decrease in workability, so it is impossible to ensure the soundness of the tightened part (there is no incomplete part of the tightening), and pass the drop test, which is said to be the most severe. It becomes difficult. In recent years, in order to solve the problem of the tightening property in the processing method, there is a means of changing the conventional method of winding the top plate / ground plate and the body plate to a double winding method, that is, a method of triple winding. Sometimes adopted. However, this method complicates the winding process and has disadvantages such as an increase in the amount of raw steel sheet used, so the soundness of the tightening part is maintained by improving the characteristics of the steel sheet, in other words, the raw steel sheet It is required to improve the tightening performance of the steel sheet. Moreover, even if the multiple winding method is adopted, there is a demand for securing the soundness of the tightened portion by improving the tightening property of the material steel plate. However, the improvement of the tightening property is usually contrary to the increase in strength accompanied by the deterioration of workability. According to the knowledge of the present inventors, it is necessary to set the ductility to 35% or more in order to improve the winding property.
[0007]
(2) Improvement of high temperature strength
In general, the drum can is not used only once, but once the contents are put in and used, the inside is washed again and again or again, on average, 4 to 5 times. When reusing, it is necessary to temporarily remove the deposits on the inner surface and the coating on the outer surface, and usually a removal operation by shot blasting is performed. When the amount of deformation generated in the can body by this shot blasting process is large, the drum cans cannot be stacked and become unsuitable for recycling. Therefore, the amount of deformation of the can body by this shot blasting is one factor that determines whether or not the material can be recycled and the number of times of recycling (recyclability).
[0008]
As a result of further investigation by the present inventors, it has been newly found that the deformation of the can body by this shot blasting treatment cannot be prevented even if only the room temperature strength of the steel sheet used is increased.
That is, in general, an incineration process is performed in which the can body is heated to about 800 ° C in order to incinerate and remove the contents before the shot blasting process. In many cases, the shot blasting process is performed warmly. In addition to the small amount of deformation of the can body due to the above-described shot blasting process, the present inventors decide to recycle that the deformation during the high temperature heating and the deformation due to the shot blasting process in the subsequent cooling process are small. I found out that it was an important factor. For this reason, the can body is also required to have high high-temperature strength in a temperature range of approximately 300 to 600 ° C.
[0009]
(3) Ensuring low temperature toughness
In conventional drums, the characteristics of cans at low temperatures are not particularly taken into account, but recently, drums used in low temperature areas and facilities of -40 ° C are increasing, and even if a drop test is performed at low temperatures, the contents It is conceivable that the occurrence of leakage of the drum is required as one index of the reliability of the drum.
[0010]
This means that low-temperature toughness, especially low-temperature toughness (reliability of the tightened part) after the tightening process must be ensured in the steel plate for drum cans. Conflicts with
However, it has been difficult to satisfy all the above-mentioned material requirements in the conventionally known increase in strength. That is, as strengthening means, solid solution strengthening by adding a large amount of alloying elements, work strengthening (see JP-A-56-77039), precipitation hardening, etc. are known. It is difficult to secure sufficient high temperature strength due to a reduction in toughness due to a decrease in toughness and a decrease in ductility. Further, a strengthening method using grain refinement or a low-temperature transformation product (such as bainite) is also known, but the strength or toughness is likely to be lowered by welding or the above-described incineration treatment.
[0011]
As described above, there is no method for increasing the strength of an appropriate steel sheet that satisfies all the characteristics required for a material for drums, and the material thickness cannot be achieved.
The first object of the present invention is to advantageously solve the above-mentioned problems, and conventionally cold-rolled steel sheets have been the mainstream, but by using hot-rolled steel sheets with few processing steps, thinning can be achieved and lightweight. In order to manufacture drums that can be used at low temperatures, at low cost, and at a low cost, as drum materials, high strength (TS: 370 MPa or more, preferably 410 MPa or more, the same applies below) and 35% elongation An object of the present invention is to propose a hot-rolled steel sheet for drums that has the above-described properties and is excellent in toughness and is excellent in formability, weldability, tightness, and high-temperature strength, and a manufacturing method thereof.
[0012]
In addition, the second object of the present invention is to provide a drum can with a high strength as a drum can material in order to produce a drum can that can be thinned, is light and low in cost, can be reused and can be used even in a low temperature range. The object is to propose a cold-rolled steel sheet for drums having an elongation of 35% or more and excellent toughness and excellent formability, weldability, winding property and high-temperature strength, and a method for producing the same.
[0013]
[Means for Solving the Problems]
As a result of various studies on the steel plate composition and manufacturing method in order to solve the above-described problems, the inventors have added a small amount of Nb to the low-carbon aluminum killed steel and optimized the manufacturing conditions as a material for the drum can. By using finely pulverized steel sheet, it has high can strength in a wide range from high temperature to low temperature and has the same or better winding strength, recyclability, weldability and weld formability than conventional materials. It has been newly found that it can be used as a drum can having a low temperature range.
[0014]
  The present invention is configured based on the above-described findings.
  That is, the present invention for achieving the first object is the weight%, C:0.025 %more than0.10% or less, Si: 0.20% or less, Mn: 1.0% or less, P: 0.04% or less, S: 0.01% or less, Al: 0.150% or less, N: 0.0050% or less, Nb: 0.005 to 0.10%, The balance is composed of Fe and inevitable impurities, YuiCrystal grain size7It is a high-strength hot-rolled steel sheet for drums characterized by being not more than μm, and in addition to the above composition, it may further contain Ti: 0.005 to 0.10% by weight, and the hot-rolled steel sheet It may be a hot-rolled steel sheet with a black skin, and the black skin is preferably a film containing 80% or more of magnetite by volume, and the thickness of the black skin is preferably 5 μm or less.
[0015]
  Further, the present invention is a steel drum can characterized in that the above hot-rolled steel plate is used for at least one of a body plate, a top plate, and a ground plate, and can be expected to be lighter by making it thinner than before. Also, it has a feature of excellent reliability of the tightening portion.
  Further, the present invention is expressed by weight%, C:0.025 %more than0.10% or less, Si: 0.20% or less, Mn: 1.0% or less, P: 0.04% or less, S: 0.01% or less, Al: 0.150% or less, N: 0.0050% or less, Nb: 0.005 to 0.10%, Preferably, a steel material having a balance of Fe and inevitable impurities is subjected to hot rolling to a finish rolling temperature of 750 ° C. or higher,After the hot rolling process is completed, 2 sec Start forced cooling withinWinding temperature:500 Over ℃The crystal grain size is characterized by being rolled up at 700 ° C or lower to form a hot-rolled sheet.7It is a method for producing a high-strength hot-rolled steel sheet for drums having excellent toughness of μm or less, and in addition to the above composition, it is preferable to further contain Ti: 0.005 to 0.10% by weight%., MaIn addition, the hot-rolled sheet may be subjected to pickling treatment as necessary, and further subjected to temper rolling.
[0016]
  Further, the present invention for achieving the second object is the weight% C:0.025 %more than0.10% or less, Si: 0.20% or less, Mn: 1.0% or less, P: 0.04% or less, S: 0.01% or less, Al: 0.150% or less, N: 0.0050% or less, Nb: 0.005 to 0.10%, The balance is composed of Fe and inevitable impurities, YuiCrystal grain size5It is a high-strength cold-rolled steel sheet for drums characterized by being not more than μm, and in addition to the above composition, it is preferable to further contain Ti: 0.005 to 0.10% by weight.
[0017]
  Further, the present invention is a steel drum can characterized in that the above-described high-strength cold-rolled steel sheet for drum can is used for at least one of a body plate, a top plate, and a base plate. The reliability of the fastening part is also excellent.
  Further, the present invention is expressed by weight%, C:0.025 %more than0.10% or less, Si: 0.20% or less, Mn: 1.0% or less, P: 0.04% or less, S: 0.01% or less, Al: 0.150% or less, N: 0.0050% or less, Nb: 0.005 to 0.10%, or Furthermore, the steel material containing Ti: 0.005 to 0.10% and the balance consisting of Fe and inevitable impurities is subjected to hot rolling to a finish rolling temperature of 750 ° C. or higher.After the hot rolling process is completed, 2 sec Start forced cooling withinWinding temperature:500 Over ℃After making into a hot-rolled sheet at 700 ° C or lower, pickle the hot-rolled sheet if necessary, and then cold-roll into a cold-rolled sheet, and anneal the cold-rolled sheet at a temperature higher than the recrystallization temperature. Or the grain size is characterized by further temper rolling.5It is a manufacturing method of high-strength cold-rolled steel sheet for drums of μm or less.
[0018]
In addition, in this invention, a crystal grain diameter shall point out the average grain diameter in the full thickness except the outermost surface in the cross section (surface which makes a right angle to a rolling direction) of a steel plate.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
  First, the reasons for limiting the chemical composition of the steel sheet of the present invention will be described.
  C:0.025 %more than0.10% or less
  C dissolves in the base and increases the strength of the steel sheet, but if it exceeds 0.10%, a large amount of carbide is formed and ductility is deteriorated, and the weld is hardened. Many cracks occur in the process. For this reason, in this invention, the upper limit of C content was made into 0.10% from a viewpoint of a moldability. Further, from the viewpoint of moldability, the C content is preferably 0.08% or less. The C content is 0.02 from the viewpoint of securing strength.Five More than%To.
[0020]
Si: 0.20% or less
Si is useful as a strengthening element. However, when it is contained in a large amount, the hot rolling property and the cold rolling property are remarkably deteriorated, and the surface treatment property (particularly chemical conversion treatment property) and the corrosion resistance are also deteriorated. Furthermore, if contained in a large amount, hardening of the welded portion becomes remarkable, which is not preferable. For this reason, Si content was limited to 0.20% or less. In particular, when used in applications requiring corrosion resistance, the Si content is preferably limited to 0.10% or less.
[0021]
Mn: 1.0% or less
Mn is an element that prevents hot cracking due to S, and is added according to the S content. Further, Mn has an effect of refining crystal grains, and the addition of Mn is preferable in terms of material. However, if it is added in a large amount, the corrosion resistance tends to deteriorate, and the steel plate is hardened to deteriorate the cold rolling property. Furthermore, since a large amount of Mn tends to deteriorate weldability and formability of the welded portion, the Mn content is limited to 1.0% or less. In the case where good corrosion resistance and moldability are required, the Mn content is preferably 0.60% or less.
[0022]
P: 0.04% or less
When P is contained in a large amount, the steel is remarkably hardened, and the flange workability and neck workability at the time of producing the drum can are deteriorated, and the corrosion resistance is remarkably deteriorated. Moreover, P has a strong tendency to segregate in steel and causes embrittlement of the weld. For these reasons, P is limited to 0.04% or less. In addition, Preferably it is 0.02% or less.
[0023]
S: 0.01% or less
Since S exists mainly as an inclusion in steel, it is preferable to reduce it as much as possible in order to reduce the workability of the steel sheet, such as ductility, bending and unbending, and to further reduce the corrosion resistance. it can. In addition, when good workability is required, the content is preferably 0.007% or less.
[0024]
Al: 0.150% or less
Al is a useful element that is added as a deoxidizing element and improves the cleanliness of the steel, and also has an effect of refining the structure, and is actively contained in the steel plate for drums of the present invention. However, when the Al content exceeds 0.150%, the steel sheet surface properties deteriorate. For this reason, the Al content is limited to 0.150% or less. From the viewpoint of the stability of the material, the range of 0.010 to 0.080% is preferable.
[0025]
N: 0.0050% or less
In the present invention, since solid solution strengthening by N is not used, it is not necessary to increase N. Rather, the effect of improving the material due to the addition of Nb is hindered, or the low temperature toughness of the tightened portion is lowered by solid solution N. It is desirable to reduce as much as possible. However, up to 0.0050% is acceptable, so the N content is limited to 0.0050% or less. From the viewpoint of improving the strength and low temperature toughness of the can body, the N content is preferably 0.0040% or less.
[0026]
Nb: 0.005 to 0.10%
Nb is an important element in the present invention, and refines the structure with a small amount of addition, and remarkably improves strength and low-temperature toughness of the tightened portion. Moreover, it has the remarkable effect which suppresses the coarsening of the structure | tissue in the seam welding part of a drum can trunk | drum. Refinement of the structure of the seam welded portion is effective in preventing cracks during flange forming as pre-forming for tightening after welding. Furthermore, the addition of a small amount of Nb increases the high-temperature strength of the steel sheet in the temperature range of 300 to 600 ° C., and increases the high-temperature creep strength and high-temperature pressure strength as a drum can body. Further, since precipitation strengthening of Nb carbide occurs after winding, the strength is relatively low during hot rolling, and the hot rolled crown does not increase. Such an effect is recognized when the content is 0.005% or more. However, when the content exceeds 0.10%, a decrease in hot rollability due to an increase in hot deformation resistance becomes significant. For these reasons, the Nb content is limited to 0.005 to 0.10%. Note that the Nb content is preferably 0.005 to 0.030% in order to facilitate manufacture of the steel sheet, that is, to suppress an increase in deformation resistance.
[0027]
Ti: 0.005 to 0.10%
Ti is effective for preventing the occurrence of cracks in the slab, and can be added as necessary. This effect is recognized when the content is 0.005% or more. However, when the content exceeds 0.10%, the formability of the welded portion of the drum can deteriorates, and in particular, the tightening property of the drum can decreases. For this reason, it is desirable to limit the Ti content to a range of 0.005 to 0.10%.
[0028]
In addition, the balance consists of Fe and inevitable impurities, but it is preferable to limit the inevitable impurities to the ranges of Cu: 0.2% or less, Ni: 0.2% or less, Cr: 0.2% or less, Mo: 0.2% or less. . Although the strength of the steel sheet is increased by containing these elements, the weldability, the workability of the welded portion, and the chemical conversion property are remarkably deteriorated.
[0029]
Next, the reasons for limiting the manufacturing conditions of the steel sheet will be described.
It is preferable that the molten steel having the above composition is melted by a generally known melting method such as a converter or an electric furnace, and solidified by a known method such as a continuous casting method, an ingot-making method, or a thin slab casting method to obtain a steel material. . Of these, the continuous casting method is preferred in order to prevent macro segregation.
Hot rolling is performed on the steel material having the above composition.
[0030]
It is desirable that the steel material is heated to a predetermined temperature and then rolled to form a hot-rolled sheet. The heating temperature of the material is not particularly limited, but is preferably in the range of 1000 to 1300 ° C. for the stability of the material. If the temperature exceeds 1300 ° C, the crystal grains become coarse and the elongation characteristics deteriorate. Moreover, if it is less than 1000 degreeC, a deformation resistance becomes high and a rolling load will increase and rolling will become difficult.
[0031]
Further, in the present invention, in addition to the method of once cooling to room temperature after casting into a slab and then reheating as described above, a method of charging and heating in a heating furnace without cooling to room temperature, or slightly There is no problem even if a direct feed rolling method, a direct rolling method, or the like, in which the rolling is performed immediately after the heat retention, is applied.
The hot rolling finish rolling temperature is set to 750 ° C. or higher.
[0032]
By setting the finishing rolling temperature to 750 ° C. or higher, a uniform and fine hot-rolled sheet structure can be obtained, and the structure of the final product (including the case of undergoing a cold rolling-annealing process, the same applies hereinafter) is also refined uniformly. Can be planned. Furthermore, non-uniform precipitation of Nb can be prevented, and the mechanical properties of the final product can be stabilized. Note that if the finish rolling temperature exceeds 1000 ° C., the generation of scale becomes remarkable, so that wrinkles due to scale occur frequently and the soundness of the surface of the steel sheet decreases, which is not preferable for drum cans that require surface soundness. For this reason, it is desirable that the finish rolling temperature be 1000 ° C. or less. In view of the uniformity of the material, the finish rolling temperature is preferably in the range of 800 to 920 ° C.
[0033]
  It is desirable to forcibly cool the hot-rolled sheet after hot rolling. This is because the refinement of the hot-rolled sheet structure is achieved by forced cooling after rolling in addition to the processing strain due to rolling, and thereby the structure of the final product (cold-rolled steel sheet) can be refined.
  Forced cooling starts immediately after rolling.TheThe forced cooling is preferably water cooling or mist cooling, and the cooling rate is preferably 50 ° C./s or more. The forced cooling should be started within 2 seconds after the end of rolling in order to improve the normal temperature strength and high temperature strength by refining hot rolled products.TheIn addition, forced cooling starts within 1 sec after the end of hot rolling from the viewpoint of strength increase and scale thickness stability control.PreferGood. Furthermore, in order to make the black skin thickness of the hot-rolled steel sheet with black skin 5 μm or less, it is desirable to start forced cooling within 0.5 s after rolling.
[0034]
  Winding temperature500 Over ℃700 ℃ or less.
  When the coiling temperature exceeds 700 ° C., the hot-rolled sheet structure becomes coarse, and abnormal grain growth occurs due to non-uniform strain that is inevitably introduced immediately after coiling, increasing the risk of deterioration of the surface properties. On the other hand, when the coiling temperature is less than 400 ° C., the shape of the hot-rolled steel sheet deteriorates, the hardness difference in the steel sheet width direction becomes remarkable, the shape of the cold-rolled steel sheet deteriorates, and as a result, the shape of the drum can becomes uneven, The function as a container may be reduced. For this reason, the coiling temperature is 700 ° C or higher.under 500Over ℃TheIn order to make the thickness of the black skin in the hot-rolled steel sheet with black skin 5 μm or less, the coiling temperature is preferably a low temperature of 600 ° C. or lower.
[0035]
After the hot-rolled sheet is wound, it is preferably subjected to temper rolling.
Temper rolling or skin pass rolling of hot-rolled sheet eliminates or reduces the yield point elongation, and further adjusts the surface roughness of the steel sheet and improves the uniformity of the shape of the original sheet (for example, reduction of ear and belly). It is preferable to carry out for this purpose. The rolling reduction of temper rolling is preferably 5% or less. When the rolling reduction exceeds 5%, the ductility of the steel sheet deteriorates and the yield point fluctuates greatly, causing problems such as variations in the amount of spring back during canning. In order to adjust the surface roughness, it is preferably 1% or more and 5% or less.
[0036]
The hot-rolled sheet is preferably applied to the manufacture of a drum can with an unrolled black skin. In this case, even if the substrate is used in a state of being untreated (untreated), the corrosion resistance and wear resistance are good because a dense iron oxide phase adheres to the inner surface of the drum. Although the outer surface of the can is coated, there is no problem in use even if the organic resin coating is performed directly after the chemical conversion treatment such as zinc phosphate or iron phosphate or without the chemical conversion treatment. The same applies to the inner surface.
[0037]
The black skin of the hot-rolled sheet with black skin is preferably a coating containing 80% or more of magnetite by volume. Thereby, it becomes a hot-rolled sheet excellent in corrosion resistance and wear resistance. The amount of magnetite in the black skin can be adjusted by promoting transformation from wustite by controlling the coiling temperature and atmosphere. When the content of magnetite in the black skin is less than 80%, the black skin peelability is remarkably deteriorated, and the drum can not be practically used. When a drum can made of a hot-rolled steel sheet with a black skin is recycled, the surface oxide layer is easily peeled off by the recycling process, so the presence of the black skin does not hinder the recycling. Further, when the thickness of the black skin exceeds 5 μm, the peelability of the black skin tends to increase, and the thickness of the black skin of the hot-rolled steel sheet with black skin is preferably 5 μm or less.
[0038]
Needless to say, the black skin may be removed. It is preferable to remove the black skin by performing pickling treatment. The pickling conditions for the hot-rolled sheet do not need to be specified in particular, as long as the surface scale can be removed, and the surface scale may be removed by a generally known method, for example, an acid such as hydrochloric acid or sulfuric acid. In addition, in order to prevent rusting after pickling, it is desirable to apply oil to the hot-rolled steel sheet. After removing the scale by pickling, temper rolling under the above conditions is performed.
[0039]
Furthermore, the hot-rolled sheet from which the black skin has been removed is subjected to surface treatment as necessary. Surface treatments that are usually applied to drums such as tin plating, chromium plating, nickel plating, nickel / chromium plating, zinc plating, and other chemical conversion treatments such as zinc phosphate and iron phosphate. Needless to say, any of them can be suitably applied. Moreover, there is no problem even if these can be made by painting or pasting an organic resin film.
[0040]
  Hot-rolled steel sheet manufactured according to the manufacturing conditions described above exhibits a high elongation of 35% or more.,flatUniform crystal grain size7The steel sheet has a uniform fine crystal structure of μm or less. When the desired strength is high, the amount of C, Mn and Nb added and the coiling temperature are controlled so that the average crystal grain size is 7 μm or less..
  Drum cans made using such hot-rolled steel plates have higher normal temperature strength after canning and higher high-temperature strength in the high temperature range (specifically 300 to 600 ° C) than when conventional steel plates are used. In the drop test at −40 ° C., the drum can have excellent low temperature toughness with no leakage of contents.
[0041]
The hot-rolled sheet manufactured under the above-described conditions may be further subjected to pickling (if necessary) and cold-rolled from the state as hot-rolled to form a cold-rolled sheet. It is recommended that the appropriate thickness of the hot-rolled mother board, which is a cold-rolled sheet, is 3.7 to 1.8 mm. The pickling conditions for the hot-rolled sheet do not need to be specified in particular, as long as the surface scale can be removed. The surface scale may be removed by a generally known method, for example, an acid such as hydrochloric acid or sulfuric acid. The rolling reduction in cold rolling is preferably 60 to 85%. In addition, the thin scale steel plate having an oxide layer thickness of 5 μm or less may be subjected to cold rolling as it is without pickling.
[0042]
The cold rolled sheet is then annealed.
Annealing is performed at a temperature equal to or higher than the recrystallization end temperature. When the annealing temperature is lower than the recrystallization end temperature, the resulting steel sheet has an unrecrystallized or partially recrystallized structure, which has high strength but poor ductility, and tends to soften significantly at high temperatures. The material becomes non-uniform in the width direction and the longitudinal direction, and the application is extremely limited. The annealing cycle used in the present invention is not particularly required to be over-aged, and it is preferable to apply a cycle in which a simple heating and cooling process is performed. However, there is no problem even if an annealing cycle in which overaging is performed is applied because the material does not change significantly except that the aging is lowered even if overaging is performed.
[0043]
The annealed cold-rolled annealed plate is subjected to temper rolling as necessary.
Temper rolling or skin pass rolling is performed to eliminate or reduce the yield point elongation, and further to adjust the surface roughness of the steel sheet and improve the shape uniformity of the original sheet (for example, to reduce ear and belly). Is preferred. The rolling reduction of temper rolling is preferably 5% or less. When the rolling reduction exceeds 5%, the ductility of the steel sheet deteriorates and the yield point fluctuates greatly, causing problems such as variations in the amount of spring back during canning. In order to adjust the surface roughness, it is preferably 1% or more and 5% or less.
[0044]
  In order to stably produce a drum can, the ductility of the can material is an important factor. If the steel sheet has an elongation value of 35% or more, stable can production is possible. The elongation value is measured by a tensile test. The specimen is collected in the circumferential direction when the drum can is formed.
  Cold-rolled steel sheets manufactured according to the above-described manufacturing conditions exhibit a high elongation of 35% or more., YuiGrain size5The steel sheet has a uniform fine crystal structure of μm or less. When the strength is high, the amount of C, Mn and Nb added and the coiling temperature are controlled so that the crystal grain size is 5 μm or less.The
[0045]
Further, the cold-rolled annealed plate is subjected to surface treatment as necessary. Surface treatments that are usually applied to drums such as tin plating, chromium plating, nickel plating, nickel / chromium plating, zinc plating, and other chemical conversion treatments such as zinc phosphate and iron phosphate. Needless to say, any of them can be suitably applied. Moreover, there is no problem even if these can be made by painting or pasting an organic resin film. Needless to say, coating may be performed after the can is made.
[0046]
Drum cans made using such cold-rolled steel sheets have higher room temperature strength after canning and higher high-temperature strength in the high temperature range (specifically 300 to 600 ° C) compared to conventional steel sheets. In the drop test at −40 ° C., the drum can have excellent low temperature toughness with no leakage of contents. The high-temperature strength is strength in the range of 300 to 600 ° C. including creep strength, and the value obtained by a normal high-temperature tensile test (crosshead speed of about 1 mm / min) is used as the measurement method.
[0047]
The drum can is composed of a body plate, a top plate, and a main plate. Using the hot-rolled steel sheet with black skin of the present invention, the hot-rolled steel sheet from which the black skin has been removed, or the cold-rolled steel sheet as a raw material, the body plate, the top plate, and the ground plate are processed, the body plate is further bent, and both ends thereof are seamed A can body is formed by welding or other joining methods, and a base plate (and a top plate in a sealed type) is attached to both ends of the can body by tightening (which may be double or multiple) to form a drum can. After forming into a drum, the inner surface is subjected to chemical conversion treatment-coating treatment before winding the top plate as necessary. After tightening the ground plate and top plate, paint the exterior. Moreover, the top plate and the main plate are processed and assembled in separate lines. In addition, although it is preferable to use the steel plate of this invention for all of a trunk | drum, a top plate, and a ground plane, even if it uses the steel plate of this invention for any one or two of these, it is effective.
[0048]
For joining the can body, mash seam welding which has been mainly used conventionally is suitable, but plasma welding, laser welding, or flash butt welding, which are other butt welding, can be applied. Alternatively, a “caulking” method may be used without using welding.
[0049]
【Example】
Example 1
Steel with the chemical composition shown in Table 1 was melted in a converter and made into a slab (steel material) with a thickness of 260 mm by a continuous casting method. Next, these slabs were hot-rolled under the conditions shown in Table 2, cooled, and then wound at the temperatures shown in Table 2. Subsequently, these hot-rolled sheets were subjected to temper rolling as necessary to obtain hot-rolled sheets having a final finished thickness of 3.5 mm. The cooling rate after hot rolling was set to 60 ° C./s throughout the following examples.
[0050]
Next, these hot-rolled sheets were pickled and then cold-rolled under the conditions shown in Table 2 to obtain cold-rolled sheets. Thereafter, these cold-rolled sheets were subjected to continuous annealing under the conditions shown in Table 2, and subjected to temper rolling under the conditions shown in Table 2 to obtain 1.2 mm thick cold-rolled annealed sheets.
For these cold-rolled steel sheets, the average crystal grain size, tensile properties (tensile strength at normal temperature and 600 ° C), bending properties, and repeated bending properties were investigated.
[0051]
The crystal grain size (average crystal grain size) was determined from an optical microscope or an electron micrograph for a cross section in the direction perpendicular to the steel sheet rolling. In addition, for the tensile properties, JIS No. 5 test pieces collected from the circumferential direction when the drum can was formed were used. As the high temperature tensile strength at 600 ° C., the value obtained in the normal high temperature tensile test was used. Bending characteristics and repeated bending characteristics were investigated for the evaluation of winding workability, and bending specimens taken from the direction perpendicular to the rolling were subjected to close contact bending and close contact bending, and evaluated by the presence or absence of breakage. In the table, no breakage is indicated by ○, and breakage is indicated by ×.
[0052]
The results are shown in Table 2.
[0053]
[Table 1]

[0054]
[Table 2]

[0055]
  Steel plate within the scope of the present invention (steel plate No.1-2No.1-4) has an average crystal grain size of 7 μm or less and exhibits an elongation of 41% or more. Furthermore, the normal temperature strength and the high temperature strength at 600 ° C. without increasing ductility are increased compared to the cold-rolled steel sheet containing no Nb (conventional example). In addition, the inventive examples also had good bending characteristics, and there was no problem with the tightening property.
[0056]
Next, a top plate and a ground plate were pressed from these steel plates. On the other hand, the body plate is bent and formed into a cylindrical shape, and both ends are seam welded to form a can body portion. The top plate and the base plate are attached to both ends of the can body portion by tightening (double tightening method), and the capacity is 200 liters. A sealed drum was obtained. The outer surface was subjected to normal coating (epoxy paint), and the inner surface was subjected to chemical conversion treatment with zinc phosphate. When making cans, the bendability at the time of can making, shape freezing properties, weldability, etc. were investigated and made into can making properties.
[0057]
Further, in order to investigate the strength characteristics of these drums, the interior was left empty and compressed from the axial direction and the circumferential direction, and a load causing macro compression buckling was measured as a buckling load.
These drums were filled with oil, cooled to -40 ° C, dropped from a height of 1.2m, and a drop test was conducted to investigate leakage and deformation. The deformation amount in the drop test is shown as a ratio with respect to the conventional example, with the deformation amount of the conventional example (steel plate No. 1-5) being 1.00. The drop test from a height of 1.8 m at room temperature specified in JIS was omitted because it was confirmed that the drum can pass the low temperature drop test without any problem.
[0058]
  These results are shown in Table 2 as can body characteristics.
  From Table 2, the present invention example (steel plate No.1-2~ No.1-4) has no problem in can making, the buckling load in the strength property test is higher than the comparative example, and the deformation amount in the low temperature drop test is also the same as the conventional example (steel plate No.1-5) It can be seen that the strength of the can has been increased. In addition, in the low temperature drop test, it can be seen that in the example of the present invention, the contents can be secured safely without leakage even though the strength is increased, and the reliability of the tightening portion is improved. In the steel plate of the present invention, the reliability of the tightening portion can always be improved regardless of the tightening method such as double winding tightening or triple winding tightening, and even under severe conditions of low temperature.
(Example 2)
  Steel containing 0.035 wt% C-0.01 wt% Si-0.25 wt% Mn-0.006 wt% P-0.005 wt% S-0.0030 wt% N-0.035 wt% Al-0.015 wt% Nb and the balance Fe and inevitable impurities Using a material (slab), hot rolling is performed under the conditions shown in Table 3, water-cooled after completion of rolling, and wound at a temperature shown in Table 3 to form a hot rolled sheet having a thickness of 3.4 to 2.5 mm, and then these hot rolled sheets After the pickling treatment, cold rolling was performed under the conditions shown in Table 3 to obtain cold rolled sheets. Thereafter, these cold-rolled sheets were subjected to continuous annealing under the conditions shown in Table 3, pickling and temper rolling under the conditions shown in Table 3 to obtain 1.0 mm-thick cold-rolled annealed sheets (steel plate No. 2-1 ~ 2-7). In continuous annealing, the furnace temperature in the overaging zone was set to 350 ° C or less, and virtually no overaging treatment was performed.
[0059]
In addition, it contains 0.035 wt% C-0.01 wt% Si-0.25 wt% Mn-0.006 wt% P-0.005 wt% S-0.0020 wt% N-0.035 wt% Al- 0.005 wt% Nb from the remaining Fe and unavoidable impurities Using this slab, hot rolling was performed under the conditions shown in Table 3, and after the completion of rolling, water-cooled, and rolled into a hot rolled sheet 2.6 mm thick at the temperature shown in Table 3 (steel plate No. 2-8). Next, the hot-rolled sheet was pickled and then cold-rolled to obtain a cold-rolled sheet having a thickness of 1.0 mm. This cold-rolled sheet was annealed at 700 ° C for 40 seconds, then cooled at a cooling rate of 50 ° C / s, and over-aged at 400 ° C for 60 seconds to make a comparative example as a cold-rolled annealed sheet .
[0060]
The top plate and the main plate are processed from these cold-rolled steel plates in the same manner as in Example 1. The body plate is bent and formed, and both ends are seam welded to form a can body portion, and the top and ground plates are wound around both ends of the can body portion. A sealed drum with a capacity of 200 liters was installed by tightening, and the canability was investigated. After making the can, the outer surface was coated with epoxy and the inner surface was subjected to chemical conversion treatment only.
For these drums, a concentrated load was applied from the outside of the drum to a compressive stress in the circumferential direction at room temperature (15 ° C.), and the amount of deformation of the resulting can was measured. The results are shown in Table 3.
[0061]
[Table 3]

[0062]
In the drum can (steel plate No.2-1 to No.2-7) using the steel plate of the scope of the present invention, it can be seen that the amount of deformation caused by load is significantly reduced compared to the comparative example (steel plate No.2-8). . That is, a significant increase in strength has been achieved. Further, a drop test at a low temperature was also conducted as in Example 1, but no leakage or the like occurred.
The amount of deformation of the can when the pressure inside the drum can was increased was also measured. Although there is no significant difference compared with the external compressive stress load, the tendency that the amount of deformation of the drum can of the present invention is smaller than the amount of deformation of the comparative example was also confirmed.
(Example 3)
The steel having the chemical composition shown in Table 4 was melted in a converter and made into a slab by a continuous casting method, then hot-rolled under the conditions shown in Table 5, and water-cooled or non-water-cooled after the rolling. Table 5 The hot rolled sheets having a thickness of 2.9 to 3.4 mm were wound at the temperatures shown, and then subjected to pickling treatment, and then cold rolled under the conditions shown in Table 5 to obtain cold rolled sheets. Thereafter, these cold-rolled sheets were subjected to continuous annealing under the conditions shown in Table 5, and subjected to temper rolling under the conditions shown in Table 5 to obtain 1.0 mm-thick cold-rolled annealed sheets. The continuous annealing was not over-aged.
[0063]
After processing these cold-rolled steel sheets into a shell plate and a top plate, the shell plate was bent and both ends were seam welded. In order to optimize the seam welding conditions of the body plate, welding conditions for conventional low carbon aluminum killed steel plate (1.0 mm thick) (welding primary current: 220 A, welding speed: 15 m / min, electrode adjusted by cylinder pressure) Pressure: 530kgf (cylinder pressure 3.0kgf / cm²Based on the equivalent)), body seam welding is performed under welding conditions with different primary welding currents, and in accordance with the normal can-making process, flange formation and ring zone expansion forming are conducted to investigate defects such as cracks. Then, the width of the range of the appropriate welding current that does not cause defects was determined.
[0064]
In addition, seam welding was performed with a welding current within an appropriate range, and a can was made into a sealed drum can with a capacity of 200 liters (both the top plate and the ground plate were wound twice). These drums were subjected to a can compression test (a static compression test in the axial direction) to determine the static crushing strength.
The results are shown in Table 5 together with the crystal grain size and mechanical properties of the steel sheet.
[0065]
[Table 4]

[0066]
[Table 5]

[0067]
From Table 5, although the present invention examples (steel plates No. 3-1 to No. 3-3) have higher strength than the conventional examples (steel plates No. 3-6), It has the same current range that can be welded, and there are no problems in both can-making and weldability. Moreover, the example of the present invention has a higher static crushing strength than the conventional example, and corresponds to an increase in steel plate strength.
If a high-strength cold-rolled steel sheet within the scope of the present invention is applied as a drum can material, an increase in can strength can be achieved without deterioration in weldability. In particular, even when the same amount of deformation is forcibly applied, the winding portion of the present invention can ensure hermeticity up to a larger strain range.
Example 4
Steel having the chemical composition shown in Table 6 was melted in a converter and slab (steel material) having a thickness of 260 mm was obtained by continuous casting. Subsequently, these slabs were hot-rolled under the conditions shown in Table 7 and then cooled and wound at the temperatures shown in Table 7 to obtain hot rolled sheets having a thickness of 1.22 mm. Next, these hot-rolled sheets were pickled or tempered as necessary to obtain hot-rolled steel sheets having a final finished sheet thickness of 1.20 mm.
[0068]
These hot-rolled steel sheets were examined for crystal grain size, tensile properties (tensile strength at normal temperature and 600 ° C), bending properties, and repeated bending properties.
The crystal grain size (average crystal grain size) was determined from an optical microscope or electron micrograph for a cross section in the direction perpendicular to the steel sheet rolling. Moreover, the black skin thickness was calculated | required from the same cross-sectional photograph. For the tensile properties, JIS No. 5 test pieces taken from the circumferential direction when the drum can was formed were used. As the tensile strength at 600 ° C., a value obtained in a normal high temperature tensile test was used. Bending characteristics and repeated bending characteristics were evaluated by the presence or absence of breakage by performing close contact bending and close contact bending on a bending specimen taken from the direction perpendicular to the rolling. In the table, no breakage is indicated by ◯, and breakage is indicated by ×.
[0069]
The results are shown in Table 7. For comparison, the test results (steel plate Nos. 1-4 of Table 2) for the cold-rolled steel sheets of D steel (Table 1) shown in Example 1 are shown as conventional examples.
[0070]
[Table 6]

[0071]
[Table 7]

[0072]
Steel sheets within the scope of the present invention (Invention Examples No. 4-1 to No. 4-4) have an average crystal grain size of 10 μm or less and exhibit an elongation of 38% or more. Further, the normal temperature strength and the high temperature strength at 600 ° C. are increased as compared with the steel plate of the comparative example (No. 1-4) without being accompanied by a decrease in ductility. The bending characteristics were also good.
Next, a top plate and a ground plate were pressed from these steel plates. On the other hand, the body plate is bent and formed into a cylindrical shape, and both ends are seam welded to form a can body portion. A liter sealed drum was obtained. The outer surface was painted with an epoxy-based paint, and the inner surface was subjected to chemical conversion treatment with zinc phosphate. When making cans, the bendability at the time of can making, shape freezing properties, weldability, etc. were investigated and made into can making properties.
[0073]
Further, in order to investigate the strength characteristics of these drums, the interior was left empty and compressed from the axial direction and the circumferential direction, and a load causing macro compression buckling was measured as a buckling load.
These drums were also filled with oil, cooled to -40 ° C, dropped from a height of 1.2m, and a drop test was conducted to investigate leakage and deformation. The deformation amount in the drop test is shown as a ratio with respect to the conventional example where the deformation amount of the conventional example (No. 1-5) is 1.00.
[0074]
These results are shown in Table 7 as can body characteristics.
From Table 7, the present invention example has no problem in can manufacturing, the buckling load in the strength property test is higher than that in the comparative example, and the deformation amount in the drop test at a low temperature is also reduced as compared with the comparative example. It can be seen that strengthening has been achieved. Moreover, it turns out that the example of this invention does not produce a leak by a low temperature drop test, can ensure the contents safely, and the reliability of the winding part is ensured. In the steel plate of the present invention, the reliability of the tightening portion can always be improved regardless of the tightening method such as double winding tightening and triple winding tightening, and even under severe conditions of low temperature.
(Example 5)
Steel containing 0.032 wt% C-0.01 wt% Si-0.15 wt% Mn-0.003 wt% P-0.004 wt% S-0.045 wt% Al-0.017 wt% Nb-0.0021 wt% N and the balance Fe and inevitable impurities Using a raw material (slab), hot rolling was performed under the conditions shown in Table 8, and after the completion of rolling, water-cooling was performed, and a rolled hot-rolled sheet was obtained at the temperature shown in Table 8. Subsequently, these hot-rolled sheets were pickled and then temper-rolled to obtain hot-rolled steel sheets having a final finished thickness of 2.3 mm.
[0075]
The top plate and the main plate are processed from these hot-rolled steel plates in the same manner as in Example 4, the body plate is bent and formed, and both ends are seam welded to form a can body, and the top and ground plates are wound around both ends of the can body It was attached by tightening to make a sealed drum with a capacity of 200 l, and the canability was investigated. After making the can, the outer surface was coated with epoxy.
About these drum cans, concentrated load was applied from the outside of the drum can at room temperature (15 ° C.) so as to be a compressive stress in the circumferential direction, and the amount of deformation of the can body at that time was measured. The results are shown in Table 8.
[0076]
[Table 8]

[0077]
It can be seen that in drums using steel plates within the scope of the present invention (Invention Examples No. 5-1 to No. 5-7), the amount of deformation caused by load is significantly reduced at both high and normal temperatures. In the comparative example (steel plate No. 5-8) outside the scope of the present invention, the amount of deformation caused by the load is large.
The amount of deformation of the can when the pressure inside the drum can was increased was also measured. Although there is no significant difference compared with the external compressive stress load, the tendency that the amount of deformation of the drum can of the present invention is smaller than the amount of deformation of the comparative example was also confirmed.
(Example 6)
Steel with the chemical composition shown in Table 9 is melted in a converter and made into a slab by the continuous casting method, then hot rolled under the conditions shown in Table 10 to form a hot-rolled sheet, pickling treatment and adjusting as necessary. A hot rolled steel sheet with a final thickness of 1.0 mm and no black skin (no scale on the surface) was obtained by quality rolling.
[0078]
A slab containing 0.035 wt% C-0.01 wt% Si-0.18 wt% Mn-0.006 wt% P-0.005 wt% S-0.045 wt% Al-0.0021 wt% N and the balance Fe and inevitable impurities (Table 9) Using steel J), hot rolling was performed under the conditions shown in Table 10, water-cooled after rolling, and then rolled into a 2.9 mm thick hot rolled sheet, and then pickled on this hot rolled sheet, Cold rolling was performed to obtain a cold rolled sheet having a thickness of 1.01 mm. This cold-rolled sheet was annealed to obtain a conventional example (steel plate No. 6-6) as a cold-rolled annealed sheet. The annealing conditions were soaking at 690 ° C. × 40 sec, followed by cooling at a cooling rate of 30 ° C./s, and practically no overaging treatment was performed.
[0079]
Using these hot-rolled steel sheets (conventional examples are cold-rolled steel sheets), the body plate and the top plate were processed, the body plate was bent, and both ends were seam welded. In order to optimize the seam welding conditions for the shell plate, the conditions for welding a conventional low carbon aluminum killed steel sheet (1.0 mm thick) (welding primary current: 220 A, welding speed: 15 m / min, electrode pressure: 530 kgf ( Cylinder pressure 3.0kgf / cm²Equivalent)), the body plate seam welding is performed under the welding conditions with the primary welding current changed, flange formation and ring zone expansion forming are conducted to investigate the occurrence of defects such as cracks, and proper welding with no defects The width of the current range was determined. In addition, seam welding was performed with a welding current within an appropriate range, and a can was formed into a sealed drum of 200 liter capacity. These drums were subjected to a can compression test (a static compression test in the axial direction) to determine the static crushing strength. The results are shown in Table 5 together with the crystal grain size and mechanical properties of the steel sheet.
[0080]
[Table 9]

[0081]
[Table 10]

[0082]
Table 10 shows that the present invention example has a weldable current range width (upper and lower limits are shifted) equivalent to that of the conventional example, although it has higher strength than the conventional example, and can-making properties. There is no problem in weldability. Moreover, the example of the present invention has a higher static crushing strength than the conventional example, and corresponds to an increase in steel plate strength.
If a high-strength hot-rolled steel sheet within the scope of the present invention is applied as a drum can material, an increase in can strength can be achieved without deterioration in weldability. In particular, it was confirmed that the tightening portion of the drum can using the material of the present invention example can ensure hermeticity up to a larger strain region even when the same deformation amount is forcibly applied. This does not change even under severe conditions at low temperatures.
(Example 7)
Steel K having the chemical composition shown in Table 6 was melted in a converter and made into a slab by a continuous casting method, and then hot-rolled under the conditions shown in Table 11 to obtain a hot-rolled sheet having a thickness of 1.1 mm. Using these steel sheets, which were made of hot-rolled steel sheets with black skin (surface scale) without pickling, as described above, drums with a capacity of 200 liters were manufactured according to the normal drum manufacturing process. In addition, the seam welding of the body portion was performed by reducing the welding current compared to the case without the black skin. In addition, the coating on the drum can was performed directly without the chemical conversion treatment, but no problem occurred.
[0083]
Table 11 shows the canability of these hot-rolled steel sheets together with hot-rolling conditions, crystal grain size, black skin (oxide layer) thickness and black skin composition (magnetite amount). The amount of magnetite was measured by the X-ray diffraction method.
[0084]
[Table 11]

[0085]
From Table 11, when the oxide layer (black skin) thickness is thick and the amount of magnetite is small, there is a little peeling at the time of can making, but by making the oxide layer thickness 5 μm or less, peeling at the time of can making is no problem. Decreased to a degree. When the oxide layer was relatively thick, the electrode wear tended to increase slightly during seam welding of the can body, compared to the case without the black skin. However, by setting the oxide layer thickness to 5 μm or less, electrode wear was comparable to that of cold-rolled steel sheets and was greatly improved. In order to make the oxide layer thickness 5 μm or less, it is preferable that the finish rolling temperature is 920 ° C. or less, the time from the finish rolling to the start of cooling is 0.5 sec or less, and the winding temperature is 600 ° C. or less.
[0086]
Thus, if the high-strength cold-rolled steel sheet and high-strength hot-rolled steel sheet of the present invention are used as the drum can material, and the drum can is produced, the can strength can be increased without increasing the can body strength, By reducing the plate thickness, the cost and weight can be reduced. Furthermore, the reliability of the tightening portion is also improved.
Although only the sealed drum with a capacity of 200 liters has been described above, it goes without saying that the same effect can be obtained even when applied to a smaller capacity drum.
[0087]
【The invention's effect】
According to the present invention, a significant increase in strength of a drum can can be achieved without accompanying a decrease in can-making performance, the reliability of the contents can be improved, and a significant increase in the number of recycling can be expected. Play. Furthermore, it is possible to achieve a reduction in the thickness of the steel sheet and to contribute to a reduction in can manufacturing cost and a reduction in weight. In addition, according to the present invention, the seam weldability of the can body portion and the subsequent stretch flange characteristics are remarkably improved, and further, there is no occurrence of liquid leakage or the like even with shock stress load at low temperature. The effect that the reliability of a fastening part improves remarkably can be expected.

Claims (12)

% By weight
C: 0.025 % or more and 0.10% or less, Si: 0.20% or less,
Mn: 1.0% or less, P: 0.04% or less,
S: 0.01% or less, Al: 0.150% or less,
N: 0.0050% or less, Nb: 0.005 to 0.10%
A high-strength hot-rolled steel sheet for drums characterized in that the balance is composed of Fe and inevitable impurities, and the crystal grain size is 7 μm or less. In addition to the composition, further weight%, Ti: 0.005 High strength hot rolled steel sheet for drums as claimed in claim 1, characterized in that it contains 0.040%. The high-strength hot-rolled steel sheet for drums according to claim 1 or 2 , wherein the hot-rolled steel sheet is a hot-rolled steel sheet with a black skin. The high-strength hot-rolled steel sheet for drums according to claim 3 , wherein the black skin is a film containing 80% or more of magnetite by volume. The high-strength hot-rolled steel sheet for drums according to claim 3 or 4 , wherein the thickness of the black skin is 5 µm or less. A steel drum can characterized in that the high-strength hot-rolled steel sheet for drums according to any one of claims 1 to 5 is used for at least one of a body plate, a top plate, and a ground plate. % By weight
C: 0.025 % or more and 0.10% or less, Si: 0.20% or less,
Mn: 1.0% or less, P: 0.04% or less,
S: 0.01% or less, Al: 0.150% or less,
N: 0.0050% or less, Nb: 0.005 to 0.10%
The composition of the steel material containing, finish rolling temperature subjected to hot rolling to 750 ° C. or more, after heat rolling process ends, starts a forced cooling within 2 sec, coiling temperature: 500 ° C. greater A method for producing a high-strength hot-rolled steel sheet for a drum can having a crystal grain size of 7 μm or less, characterized in that it is wound at 700 ° C. or lower to form a hot-rolled sheet. The method for producing a high-strength hot-rolled steel sheet for a drum can according to claim 7 , wherein the hot-rolled sheet is further subjected to temper rolling. % By weight
C: 0.025 % or more and 0.10% or less, Si: 0.20% or less,
Mn: 1.0% or less, P: 0.04% or less,
S: 0.01% or less, Al: 0.150% or less,
N: 0.0050% or less, Nb: 0.005 to 0.10%
A high-strength cold-rolled steel sheet for a drum can characterized by having a composition composed of Fe and the inevitable impurities, and having a crystal grain size of 5 μm or less. The high-strength cold-rolled steel sheet for drums according to claim 9 , further containing Ti: 0.005 to 0.10% by weight% in addition to the composition. A steel drum can characterized in that the high-strength cold-rolled steel sheet for drums according to claim 9 or 10 is used for at least one of a body plate, a top plate, and a base plate. % By weight
C: 0.025 % or more and 0.10% or less, Si: 0.20% or less,
Mn: 1.0% or less, P: 0.04% or less,
S: 0.01% or less, Al: 0.150% or less,
N: 0.0050% or less, Nb: 0.005 to 0.10%
Is subjected to hot rolling to a finish rolling temperature of 750 ° C or higher, and forced cooling is started within 2 seconds after the hot rolling is completed , and the coiling temperature is over 500 ° C and below 700 ° C. After the hot-rolled sheet is wound in step 1, the hot-rolled sheet is pickled and then cold-rolled by cold rolling, and the cold-rolled sheet is annealed at a temperature higher than the recrystallization temperature, or further temper rolled. A method for producing a high-strength cold-rolled steel sheet for a drum can having a crystal grain size of 5 μm or less.