JP4221978B2 - Metal band manufacturing method for preventing waist breakage in metal band manufacturing equipment - Google Patents

Description

ただし、ｔ；板厚ｍｍ、Ｔ；板張力ｋｇ、ｗ；板幅ｍｍ、σ；降伏応力ｋｇ／ｍｍ²、Ｅ；ヤング率ｋｇ／ｍｍ²であり、Ｒはロールに巻きつく際の曲率半径である。例えば、板厚１ｍｍ、板張力１０００ｋｇ、板幅１０００ｍｍ、降伏応力２０ｋｇ／ｍｍ²、ヤング率２００００ｋｇ／ｍｍ²で、曲率半径を３００ｍｍとした場合は、
１．３３ ≦ Ｎ ≦ １９．９５
となり、結局必要本数は２本以上１９本以下となる。実際には対象となる鋼帯の板厚や、降伏応力等に幅があるため、その変動に対応できるように、ロールの押込み量を調整し、曲率半径を調整できるようにするのが好適である。なお、ロール本数が６本以上になると、歪付与効果が飽和し、設備費用や保守費用等が高くなるので、本数は１〜５本の範囲で選定することが好ましく、２〜３本がより好ましい。
【００６０】
ロールで曲げ加工する場合、少なくとも一本のロールで付与される金属帯の曲率半径が４００ｍｍ以下となるようにロール径を選択し、該ロールの押し込み量を調整して金属帯を曲げ加工することが好ましい。金属帯を曲率半径４００ｍｍ以下で曲げるには、ロール径がφ８００ｍｍ以下のロールを用いる必要があり、ロール本数は１本以上であればよい。例えばφ８００ｍｍのロール（大径ロール）で金属帯が該ロールに十分巻きつくように押込み量を調整する方法やロール径がφ４００ｍｍのロールで押込み量を調整する方法を例示できる。但し、ロールの押し込み量は金属帯材質、厚さ等で異なる。付与する表面塑性歪量を大きくするには、ロールの押し込み量を大きくすることや小径ロールを使用することがよい。曲げロールのロール径は、φ４００ｍｍ以下の小径ロールが好ましい。なお、なお、縦型焼鈍炉ではハースロール径は通常φ８００ｍｍ以上、特殊の専用炉にあってもφ５００ｍｍ超、一般にはφ６００ｍｍある。
【００６１】
このようにしてロールの径、設置数、設置場所を決定することで、本発明で必要な温度域および、塑性歪量を実現できる。
【００６２】
図１の連続焼鈍ラインでは、歪付与装置８は加熱焼鈍炉４内の出側近傍に近い最終パスに設置されている。図２は、図１の装置に設置されている歪付与装置を示す概略図で、３本のロールが配置されている例である。すなわち、予歪付与装置８は、鋼帯１通板方向（上下方向）位置をずらし、鋼帯１の両側に千鳥配置された３本のロール１１〜１３で構成されている。前記ロール１１〜１３はそれぞれ独立にパスラインと略直角方向に移動自在に構成されている。１４、１５はハースロールである。
【００６３】
図２の装置を用い、ロール１１〜１３のうちの少なくとも１本以上をパスラインと略直角方向にパスラインを超えて押し込むことで鋼帯の表面に塑性歪を付与する。一例を挙げると、図３（ａ）に示すように、ロール１１及び１３をパスラインにほぼ接するように配置し、ロール１２をパスラインと略直角方向にパスラインを超えて押し込むことで、鋼帯１を曲げ加工してその表面に塑性歪を導入する。あるいは、図３（ｂ）に示すように、ロール１３をパスラインにほぼ接するように配置し、ロール１１と１２をそれぞれパスラインと直角方向に互いに異なる方向、すなわちロール１２はロール１１側に押し込み、ロール１１はロール１２とは反対方向に、各々パスラインを超えて押し込むことで、鋼帯１を曲げ加工してその表面に塑性歪を導入する。図３（ａ）及び（ｂ）では、ロール１１は、鋼帯１のシンクロール６と接触する面側に配置されている。なお、本明細書において、「ロールがパスライン位置にある」とは、ロールがパスラインに接する位置にあることを意味している。図３（ａ）、（ｂ）で、ロール１２は、鋼帯１に対してハースロール１５と同じ側に配置されている。
【００６４】
図３（ｃ）、（ｄ）に示すように、鋼帯１に対する各々のロール配置は、前記（ａ）、（ｂ）と逆の配置であってもよい。
【００６５】
導入される表面塑性歪量は、鋼帯の曲げ曲率で決定され、曲げ曲率は、隣り合うロール同士の金属帯通板方向間隔、ロール径とその押込み量（パスラインを超える押し込み量）を制御することで制御できる。なお、鋼種等の金属帯材質、板厚、温度等の操業変数、隣り合うロール同士の金属帯通板方向間隔、ロール径、ロールの押し込み量等と、表面塑性歪量の関係を予め求めて、対応表を作成しておき、この対応表に基き、操業変数値に応じて、前記各場合におけるロールの押し込み量を設定する。
【００６６】
図２に示した装置は、３本の曲げロールが配置されている例であるが、ロール本数は３本に限定されず、１〜５本の範囲内とすることが好ましい。
【００６７】
歪付与装置８で鋼帯１に塑性歪を付与する際に鋼帯１幅方向反り（Ｃ反り）に影響を与える。Ｃ反りが大きいと、冷却帯５での鋼帯１の均一冷却を妨げ鋼帯１形状を悪化させたり、スリキズを発生させたり等するため、歪付与装置出側で鋼帯１のＣ反りが少ないことが望ましい。
【００６８】
本発明者等は、前記塑性歪付与と同時に歪付与後の鋼帯形状（Ｃ反り）を良好ならしめることについても検討した。その結果、鋼帯通板方向最終ロールで付与される歪量を小さくすることが有効であること明らかになった。３本のロールを使用する場合、図３（ｂ）及び（ｄ）に示されるように、金属帯通板方向最終ロールであるロール１３は略パスライン位置（パスラインに接する位置またはその近傍位置）、中間ロール（ロール１３の上流側ロール）であるロール１２は、パスラインを超えて前記ロール１３側に押し込まれた位置、入側ロール（ロール１２の上流側ロール）であるロール１１は、パスラインを超えて前記ロール１２側に押し込まれた位置に配置することが好ましい。
【００６９】
前記において、ロール１１のパスラインからの押し込み量（ｄ１）、ロール１２のパスラインからの押し込み量（ｄ２）を略同一にすることがより好ましい。
【００７０】
最終ロールで付与される歪量としては、例えば、金属帯に付与される塑性歪（各ロールで付与される塑性歪の和）が０．５％程度である場合、最終ロールで付与される塑性歪を０．１％程度とする例を例示できる。前記ロール配置の一例を挙げると、ロール１１〜１３の径をφ２５０ｍｍ、ロール同士の間隔を３００ｍｍとし、ロール１３をパスライン位置に配置し、ロール１１と１２をパスラインから５０ｍｍ押し込む例を例示できる。但し、本発明はこれに限定されるわけではない。
【００７１】
最終ロールで付与される歪量を小さくするには、前記ロール押し込みと組み合わせて、あるいは前記ロール押し込み方に代えて、最終ロールのロール径を該ロールの上流側に配置される曲げロールのロール径より大きくするようにしてもよい。例えば図２において、最終ロールのロール径を入側ロール、中間ロールの各ロール径より大きくすることが有効である。図２において、最終ロールのロール径を大きくした場合、各ロールのロール配置（押し込み方法）は、図３（ａ）及び（ｄ）のように、入側ロールと最終ロールをパスライン位置に配置し、中間ロールをパスラインと略直角方向にパスラインを超えて押し込む配置であってもよい。このロール配置の一例を挙げると、ロール１１とロール１２のロール径を１５０ｍｍ、ロール１３のロール径を４００ｍｍとし、ロール１１と１３をパスライン位置に配置し、ロール１２のパスラインからの押し込み量を１００ｍｍとする例を例示できる。但し、本発明はこれに限定されるわけではない。
【００７２】
また、前記と組み合わせ、あるいは前記に代えて、入側ロールと中間ロールの間隔（鋼帯通板方向間隔）よりも、中間ロールと最終ロールの間隔を大きくするようにロールを配置してもよい。
【００７３】
曲げロールを２本使用するときは、前記最終ロール１３に代えて、ハースロール１５を使用できるようなロール配置にすることが好ましい。また、曲げロールを４〜５本使用するときは、最終ロールで付与される塑性歪を小さくする観点から、最終ロールはパスライン位置に配置されることが好ましい。
【００７４】
但し、最終ロールで付与される歪は、最終ロールとその上流側のロールの相対的な位置関係で決まるものであるから、最終ロールの上流側ロールの押し込み量が大きい場合は、最終ロールのパスラインに対する位置をパスラインからずらす場合もある。したがって、最終ロールの位置はパスライン位置に限定される訳ではない。
【００７５】
例えば、図４において、ロール２２〜２４のパスラインに対する押し込み位置が各々ｘ１〜ｘ３（パスライン位置が「０」、右側への移動量は「＋」、左側への移動量は「−」である。）であり、ロール２２の押し込み量（｜ｘ１｜）を小さく、ロール２３の押し込み量（｜ｘ２｜）を大きくした場合、最終ロールで付与される歪は、最終ロール２４と中間ロール２３の相対的な位置関係（｜ｘ２−ｘ３｜）で決まるので、ロール２４は、パスラインより左側に移動させるように配置する方が好ましい。
【００７６】
歪付与装置出側の鋼帯反りを少なくするには、鋼帯表面に前記で説明したような表面塑性歪みが付与されることが必要である。鋼帯反りを少なくする曲げロールの押し込み量は、前記塑性歪の付与で説明したのと同様にして、前記操業変数と、所定表面塑性歪量の付与とＣ反り防止効果を両立できるロールの押し込み量の対応表を作成しておき、この対応表に基き、操業変数値に応じて、ロールの押し込み量を設定することで、腰折れを防止できるだけでなく、ガスワイピングノズル部におけるＣ反り発生を防止できる。
【００７７】
前記のようにして歪を付与することで、腰折れが発生する危険が高い、しきい温度Ｔ１より低い温度域でロールによる曲げ変形があっても、前記歪効果により腰折れ欠陥が発生せず、しかも、歪を与える温度域が腰折れ発生の危険がない温度域であるため、歪付与の際に腰折れが発生することも皆無であるため、理想的な腰折れ防止法といえる。
【００７８】
前記したように、特許文献６には、押し込みロールを設けて帯板の反りを矯正することが記載されている。しかし、特許文献６では、めっき浴中にサポートロールを備える溶融めっき設備における反り防止を対象とし、また該サポートロールと押し込みロールを併用することで帯板の反りを矯正するものであって、サポートロールを使用しないで、押し込みロールだけで帯板の反りを矯正するものではない。また、特許文献６では、帯板表面に所要の塑性歪を付与することは示されていないだけでなく、めっき浴中にシンクロールを備えないので、帯板に安定して十分な張力を付与することが困難であり、したがって帯板表面に所要の表面塑性歪を安定して付与することはできないと考えられる。
【００７９】
以上、曲げロールを使用して歪を付与することを説明した。曲げロールに代えて、圧延ロールを使用して塑性歪を付与してもよい。この場合、鋼帯に付与する塑性歪は０．１％超１．５％以下にすればよい。
【００８０】
図１に示した連続焼鈍ラインでは、鋼帯１はＯＡ／冷却帯６で再加熱されることがある。ＯＡ／冷却帯６内またはそれより下流側に腰折れ発生危険部が存在する場合は、歪付与後該腰折れ発生危険部に至る間の鋼帯温度は、しきい温度Ｔ１以上にされないことが必要である。
【００８１】
連続焼鈍ラインに歪付与装置を設けた上記本発明の本実施の形態では、焼鈍炉３通板中に「腰折れ」が発生しやすいＢＨ鋼板の腰折れを防止するのに好適であるが、本発明は前記鋼板に限定されず、焼鈍炉３通板中に「腰折れ」が発生しやすい鋼帯において、広く腰折れを防止する効果が奏される。連続焼鈍ラインは、図１に示される構成の連続焼鈍ラインに限定されず、他の構成の連続焼鈍ラインであってもよい。また、前記で説明した歪付与装置を圧延装置に代え、圧延ロールで歪を付与してもよい。この場合、腰折れを防止するいは、０．１％超１．５％以下の圧延歪を付与すればよい。
【００８２】
歪付与装置８を設置する金属帯の加熱手段を有する金属帯製造装置は連続焼鈍ラインに限定されず、金属帯の加熱手段を有する金属帯製造装置であればよく、鋼帯は冷延鋼帯以外、例えば熱延鋼帯であってもよく、鋼帯以外の金属帯であってもよい。本発明によれば、常温で降伏点伸びを持つ金属帯の腰折れを効果的に防止できる。
【００８３】
【実施例】
焼鈍後後に常温で降伏点伸びを有する、厚さ０．７５ｍｍ、幅１２００ｍｍの鋼帯を準備した。鋼帯の化学成分を表１に記載する。
【００８４】
【表１】

図１に示した連続焼鈍ラインを用いて、前記鋼帯を、ライン速度１２０ｍｐｍ、張力２ｋｇ／ｍｍ²、焼鈍温度８５０℃で焼鈍した後、予歪付与装置２１で種々の条件で予歪を付与した後、冷却帯５で約４００℃に冷却し、ＯＡ／冷却帯６で３００〜４００℃に保持した後冷却し、さらに調質圧延機（図示なし）で調質圧延を行って、冷延鋼帯を製造した。比較のために、予歪を付与しない冷延鋼帯も製造した。該冷延鋼帯（焼鈍後の冷延鋼帯、予歪付与なし且つ調質圧延なし）は、常温での引張り材料特性は、上降伏点２５ｋｇ／ｍｍ²、下降伏点２２ｋｇ／ｍｍ²、降伏点伸び４．３％で、引張試験によると降伏点伸びのなくなる温度（しきい温度Ｔ１）は４４０℃であった。
【００８５】
予歪付与装置８は加熱焼鈍帯４に配置され、図２に示したロール本数が３本の装置に代えて、図５に示されるように、ロール本数が６本で金属帯通板方向に千鳥配置された装置（金属帯通板方向に対して上流側から＃１〜＃６ロールとする）を使用した。ロール径はいずれもφ２５０ｍｍ、隣り合うロール同士の鋼帯通板方向間隔（軸心距離；Ｌ１）はいずれも３００ｍｍ、＃６ロールとハースロール１５との間隔（軸心距離；Ｌ２）は１０００ｍｍである（以下、Ａ装置という）。また予歪付与装置下流側のハースロール径はφ１０００ｍｍである。
【００８６】
３本のロールを使用する場合は、＃１〜＃３ロールはパスラインから退避させて開放し、＃６ロールをパスライン位置に配置し、＃４ロールと＃５ロールを図３（ｂ）に示すようにパスラインからずらした位置に押し込み、その押し込み量を調整した。
【００８７】
５本のロールを使用する場合は、＃１ロールは不使用とし、＃２、＃４、＃６ロールの３本をパスライン位置に配置し、前記各々のロールの中間に千鳥対置された＃３、＃５の２本のロールをパスラインと略直角方向にパスラインを超えて押し込んだ。
【００８８】
６本のロールを使用の場合は、＃２、＃４、６ロールの６本をパスライン位置に配置し、前記各ロールに対して千鳥対置された＃１、＃３、＃５の３本のロールをパスラインと略直角方向に押し込み、その押し込み量を調整した。
【００８９】
また、前記Ａ装置において、＃１〜３ロールを撤去し、＃４〜＃６ロールにφ１００ｍｍのロールを設置し（以下、Ｂ装置という）、＃６ロールをパスライン位置に配置し、＃４ロールと＃５ロールを図３（ｂ）に示すようにパスラインからずらした位置に押し込み、その押し込み量を調整した。前記＃４〜＃６ロールは、ロール剛性の点から、各々φ４００ｍｍのバックアップロールで補強した。
【００９０】
１本のロールを使用する場合は、前記Ａ装置において、＃１〜＃６のロールを撤去し、＃３ロールとしてφ１０００ｍｍのロール、＃６ロールとしてφ１００ｍｍのロールをそれぞれ配置し（以下、Ｃ装置という）、＃６ロールをパスラインを超えて押し込み、押し込み量を調整した。前記＃６ロールは、ロール剛性の点からφ４００ｍｍのバックアップロールで補強した。
【００９１】
前記で得た鋼帯の腰折れ程度を、自動車ドアパネルのプレスを模したプレス試験を行った後、目視観察し、腰折れ欠陥の程度に応じて０〜５の６段階で評価した。腰折れ程度は０（発生なし）が最良で、数字が大きいほど劣位で５が最劣位である。自動車外板などの用途では評点「１」以下、自動車内板などの用途では「２」以下が望ましい。予歪付与条件及び腰折れ程度の評価結果を表２に記載する。
【００９２】
【表２】

予歪付与条件が本発明範囲内にある発明例は、腰折れ程度の評点が２以下であり、腰折れ欠陥が防止され、または本発明範囲を外れる比較例に比べて、その程度が軽微である。さらに予歪付与後の鋼帯反りも少なく、鋼帯反りに起因する通板上、品質上の問題は無かった。
【００９３】
さらに自動車ドアのプレス試験を実施したところ、評点０及び１については、連続焼鈍ラインでの腰折れに起因する欠陥は全くみられず、評点２のものも連続焼鈍ラインでの腰折れに起因する欠陥に起因する非常に軽微であった。このように、本発明を用いることで腰折れがない鋼帯を製造することができた。
【００９４】
本実施例ではロール曲げによる表面塑性歪付与を行ったが、他の方法（例えば圧延法）によって実施しても同様の効果が得られる。
【００９５】
【発明の効果】
本発明によれば、降伏点伸びのある金属帯でも表面性状を著しく劣化させる腰折れ模様を、低コストでしかも確実に防止でき、欠陥検査等の簡略化が図れる。
【００９６】
また、本発明によれば、予歪付与後の金属帯Ｃ反りを低減できるので、金属帯Ｃ反りに起因する通板上、品質上の問題の発生を防止できる。
【図面の簡単な説明】
【図１】本発明の実施の形態に係る連続焼鈍装置の概略図である。
【図２】図１の装置に配置される歪付与装置の構成例を説明する概略図である。
【図３】曲げロールのロール配置例を説明する図である。
【図４】予歪付与装置に使用するロールの別の配置例を説明する図。
【図５】実施例で使用した予歪付与装置のロール配置を説明する図。
【図６】一般的な連続焼鈍装置の概略図である。
【符号の説明】
１ 金属帯（鋼帯）
２ 巻き戻し装置
３ 連続焼鈍炉
４ 加熱手段（加熱焼鈍帯）
５ 冷却帯
６ ＯＡ／冷却帯
７ 巻取り装置
８ 歪付与装置
１１〜１３ 曲げロール
１４、１５ ハースロール[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a metal strip.To the lawRelated. More specifically, when manufacturing a metal strip having a yield point elongation at room temperature in a metal strip manufacturing apparatus having a heating means for the metal strip, a method of manufacturing a metal strip that can prevent a waist break occurring in the apparatus.To the lawRelated.
[0002]
[Prior art]
Since the metal strip is subjected to heat treatment or the like, it is often produced by a continuous line having heating means in the line. For example, steel strips such as cold-rolled steel strips are manufactured on a continuous annealing line. FIG. 6 is a schematic view showing a general continuous annealing line. In FIG. 6, 1 is a steel strip, 2 is a rewinding device, 3 is a continuous annealing furnace, a heating annealing zone 4, a cooling zone 5, and an OA / cooling zone 6 are arranged in this order, and 7 is a winding device.
[0003]
In this continuous annealing line, a raw steel strip 1 such as a cold-rolled steel strip is unwound from a rewinding device 2, introduced into an annealing furnace 3, annealed in a heating annealing zone 4, and cooled in a cooling zone 5. Further, after being cooled in the OA / cooling zone 6 or reheated to a temperature of about 300 ° C. to 400 ° C., it is cooled and led out of the annealing furnace 3. The steel strip led out of the annealing furnace 3 is temper-rolled by a temper rolling mill (not shown) and wound by the winding equipment 7.
[0004]
When a steel strip is produced by the continuous annealing line, for example, a steel strip that is age-hardened when heated to about 200 ° C. (hereinafter sometimes referred to as BH steel strip) has a yield point elongation. There is a case in which a distortion pattern called “back folding” occurs in the threading plate. This defect can be made inconspicuous by temper rolling with a temper rolling mill, but it may become obvious again during press forming by the customer, etc. descend.
[0005]
As a conventional technique for preventing hip breakage, there is a method of defining the sheet passing speed by a calculation formula determined from the plate thickness, temperature, roll diameter and the like (see Patent Document 1). In addition, there is a method in which rolling is performed in a specific temperature range to control the distribution state of crystal grain size (see Patent Document 2). A method of changing the material of the steel strip to a material that does not cause hip folding (for example, refer to Patent Document 1), and a method of imparting pre-strain to the steel band to make the waist folding less noticeable (for example, refer to Non-Patent Document 1).
[0006]
However, there was a problem with either method. For example, in the method of defining the plate passing speed, the speed necessary for preventing hip breakage is large and cannot be realized depending on the equipment, and the temperature control is difficult to control the particle size, and a stable effect cannot be obtained.
[0007]
In addition, changing the material can provide a certain effect, but it also affects the material and is disadvantageous in terms of cost. Furthermore, although the method using pre-strain is recognized to have a certain effect, there is a concern that the pre-strain itself may cause a hip break, so that a large pre-strain is not given and the effect is often limited.
[0008]
As described above, since there is no technology that can fundamentally prevent hip breakage in the prior art, there is a problem that yield must be reduced because it is necessary to deal with strict customers with strict quality control.
[0009]
The prior art document information will be described below. Note that Patent Documents 4 to 6 are described in the section of [Embodiment of the Invention] for convenience of description.
[0010]
[Patent Document 1]
JP-A-55-136510 (first page)
[0011]
[Patent Document 2]
Japanese Patent Laid-Open No. 58-217637 (first page)
[0012]
[Patent Document 3]
JP-A-6-299292 (first page)
[0013]
[Patent Document 4]
Japanese Patent Publication No. 7-94704 (page 1-3, FIG. 1)
[0014]
[Patent Document 5]
Japanese Patent Laid-Open No. 10-130801 (page 1-4, FIG. 1)
[0015]
[Patent Document 6]
JP 2000-204460 A (second page, FIG. 1)
[0016]
[Non-Patent Document 1]
Masatoshi Aratani, 4 others, “Effects of canning conditions on the fruiting properties of steel sheets for 3-piece cans”, Iron and Steel, Japan Iron and Steel Institute, 1997, Vol. 83, No. 4, p. 19-24
[0017]
[Problems to be solved by the invention]
An object of the present invention is to produce a metal strip that can prevent waist breakage occurring in the metal strip production apparatus having a heating means for the metal strip when producing a metal strip having a yield point elongation at room temperature.The lawIs to provide.
[0018]
[Means for Solving the Problems]
Means of the present invention for solving the above problems are as follows.
(1) A method for producing a metal strip having a yield point elongation at room temperature in a metal strip production apparatus having a heating means for the metal strip,
A heating step of heating the metal strip to the following threshold temperature or higher;
A strain imparting step of imparting plastic strain to the metal strip in a temperature range where the temperature of the metal strip is the following threshold temperature T1 or more and 650 ° C. or less.,
The plastic strain is applied using (a) a roll that bends and deforms the metal band, and the plastic strain has a surface plastic strain amount of more than 0.1% and not more than 1.5% of the metal band, or (B) Rolling strain applied by a rolling roll, and the plastic strain amount is more than 0.1% and 1.5% or less.
It is characterized byPreventing hip breakage in metal strip manufacturing equipmentA method for producing a metal strip.
[0019]
However, the threshold temperature T1 is a temperature at which the elongation at the yield point of the metal strip disappears above the temperature.
[0020]
(2) The strain imparting step is provided on the downstream side of the maximum metal zone temperature reaching point in the heat annealing step, and on the upstream side where the hip breakage occurrence risk part is upstream.Preventing hip breakage in metal strip manufacturing equipmentA method for producing a metal strip.
[0021]
However, the waist folding risk portion is a portion where the metal band is broken when the plastic strain is not applied.
[0024]
(3)The plastic strain is applied by dividing into 1 to 5 times.(1) or (2)Described inPreventing hip breakage in metal strip manufacturing equipmentA method for producing a metal strip.
[0025]
(4)The plastic strain imparting step is provided downstream of the maximum metal zone temperature reaching point in the heat annealing step.(1)-(3)In any ofPreventing hip breakage in metal strip manufacturing equipmentA method for producing a metal strip.
[0026]
(5)The metal band temperature is set to 650 ° C. or less from the strain applying step to the waist folding risk portion.Any of (1) to (4)Described inPreventing hip breakage in metal strip manufacturing equipmentA method for producing a metal strip.
[0027]
(6)Two or more plastic strainsrollWhen applying usingPlastic strainIs the final one placed on the steel strip through directionrollThe amount of surface plastic strain applied inrollUpstream ofrollIt is characterized by being applied so as to be smaller than the surface plastic strain applied byAny of (1) to (5)Described inPreventing hip breakage in metal strip manufacturing equipmentA method for producing a metal strip.
[0028]
(7)The plastic strain is applied using three rolls arranged in a staggered manner on both sides of the metal band in the metal band passing plate direction, and is disposed on the metal band sheet passing side out of the three rolls. The final roll is disposed substantially at the pass line position, and the entrance roll disposed on the metal band passing plate direction entrance side is pushed beyond the pass line in the direction substantially perpendicular to the pass line of the metal band,The entrance roll and the final rollThe intermediate roll disposed between the metal roll is pushed over the pass line in a direction substantially perpendicular to the pass line.Any of (1) to (6)Described inPreventing hip breakage in metal strip manufacturing equipmentA method for producing a metal strip.
[0029]
(8)The pushing amount from the pass line of the entry side roll and the pushing amount from the pass line of the intermediate roll are substantially the same.(7)Described inPreventing hip breakage in metal strip manufacturing equipmentA method for producing a metal strip.
[0030]
(9)Of the three rolls, the roll diameter of the final roll is larger than the roll diameters of the entry roll and the intermediate roll.(7) or (8)Described inPreventing hip breakage in metal strip manufacturing equipmentA method for producing a metal strip.
[0031]
(10)The plastic strain is applied using three rolls arranged in a staggered manner on both sides of the metal band in the metal band passing plate direction, and is disposed on the metal band sheet passing side out of the three rolls. The roll diameter of the final roll is as follows:The entrance roll and the final rollIt is characterized by being larger than the roll diameter of the intermediate roll arranged betweenAny of (1) to (6)Described inPreventing hip breakage in metal strip manufacturing equipmentA method for producing a metal strip.
[0032]
(11)The entrance roll and the final roll are arranged at a substantially pass line position, and the intermediate roll pushes the metal plate in a direction substantially perpendicular to the pass line beyond the pass line.(10)Described inPreventing hip breakage in metal strip manufacturing equipmentA method for producing a metal strip.
[0043]
DETAILED DESCRIPTION OF THE INVENTION
The present inventors diligently studied the cause of the occurrence of steel belt waist breakage and the method of avoiding it in a continuous annealing facility. First, as a result of examining the cause of hip fracture, the following findings were obtained. When the steel strip is passed through the continuous production apparatus, it is subjected to bending by a roll in various steel strip temperature ranges, and a strong stress is applied. When the magnitude of the stress exceeds the yield stress, the bent portion yields locally and becomes a hip break. Here, since the stress is a bending stress by a roll, the vicinity of the surface is the largest.
[0044]
The present inventors performed a material test by bending and a test in an actual machine. As a result, even if the steel strip has a yield point elongation at room temperature, the yield point elongation disappears when the steel strip temperature exceeds a certain temperature. It was found that the threshold temperature T1 is a temperature at which the yield point zone of the steel strip disappears. At the threshold temperature T1 or higher, the steel strip does not fold down because the steel strip has no yield point elongation in this temperature range, and local strain concentration does not occur even at stresses exceeding the yield point. It is done.
[0045]
In general, it is known that when strain is applied in advance at room temperature, hip breakage is less likely to occur in subsequent processing. The inventors of the present invention have an effect even when the strain imparting effect is equal to or higher than the threshold temperature T1, that is, when prestrain is applied to the steel strip when the steel strip temperature is equal to or higher than the threshold temperature T1, It has been newly found that waist folding does not occur even when the belt is bent with a roll at a temperature lower than the threshold temperature T1. The threshold temperature T1 varies depending on the steel type and the like, and the threshold temperature T1 is determined from the steel strip temperature at which the elongation at yield point is eliminated by performing a tensile test while changing the steel strip temperature. Further, if the temperature is too high, the effect of imparting strain decreases, and if the temperature exceeds 650 ° C., the prevention effect is hardly observed, and the amount of plastic strain to be introduced needs to exceed 0.1% in terms of surface strain. If it exceeds 5%, the effect reaches a peak, and the surface plastic strain does not need to be applied by one bending roll, and may be added in several times in the temperature range, but it is divided into 6 or more times. It was found that the effect reached a peak when applied. Therefore, it is preferable that the plastic strain is applied in 1 to 5 times. Here, the amount of strain is elastic strain + plastic strain, and the elastic strain is expressed by σ / E (σ: yield stress of material, E: Young's modulus).
[0046]
Since the stress causing the hip fracture defect is a bending stress caused by the roll, the stress in the vicinity of the surface is the largest. For this reason, in order to prevent a hip fracture defect, it is effective to take measures against the vicinity of the surface where the strongest stress is applied. From such a viewpoint, a method of applying pre-strain with a bending roll is conceivable. As a result of the test, when pre-strain is imparted by a bending roll, the number of rolls is preferably 1 to 5.
[0047]
Note that Patent Documents 4 to 6 describe that a steel strip is subjected to a roll bending process in an annealing furnace.
[0048]
In Patent Document 4, the crystal grain size is adjusted by annealing a steel strip after bending with a roll having an outer diameter of 50 mm or more and 500 mm or less, followed by a solid-liquid reaction in a galvanizing bath and subsequent Fe-Zn alloying reaction. To prevent surface irregularities generated by the alloying process. The present invention is different from the present invention in issues and configuration.
[0049]
In Patent Document 5, bending and unbending processes are performed at a bending radius of 300 mm or less, and residual strain is applied to the surface of the steel strip to make the diffusion reaction at the steel plate and the plating interface uniform. This prevents the initial alloying unevenness due to the non-uniform distribution of the additive elements in the steel strip to which Si, P, Mn, etc. are added, and the initial surface due to the large surface roughness in the hot-rolled steel strip. It prevents uneven alloying, thereby preventing uneven plating, reduced gloss, and uneven alloying reaction. The subject of the present invention is different.
[0050]
In Patent Document 6, the strip plate is passed through the passage plate chamber of the apparatus for plating by passing the strip plate from the passage plate chamber in a non-oxidizing atmosphere into a molten metal plating bath, using two points in the pass line as fulcrums. The push roll which can be pushed in across the position is provided, and the curvature of a strip is corrected.
[0051]
In Patent Documents 4 to 6, the steel strip targeted for any of these is a hot-dip plated steel strip, and it is not considered to prevent hip breakage.
[0052]
The present invention has been made based on the above findings.
[0053]
Hereinafter, embodiments of the present invention will be further described with reference to the drawings. A continuous annealing line will be described as an example of an apparatus for manufacturing a metal band having a metal band heating means. In the following description, a steel strip is used as a metal strip. FIG. 1 is a schematic view showing a main part of a continuous annealing line according to an embodiment of the present invention, in which a strain imparting device 8 is installed in the general continuous annealing line shown in FIG. A heating annealing zone 4 for heating and annealing the metal strip is provided as a heating means.
[0054]
In the present embodiment, a strain imparting device is provided in the annealing furnace 2 having the threshold temperature T1 or more and 650 ° C. or less downstream of the maximum steel strip temperature reaching point. When strain is applied to a steel strip having a temperature lower than the threshold temperature T1, the belt will bend when the strain is applied, and the effect of preventing hip breakage will not be achieved. Further, when strain is applied to a steel strip having a temperature exceeding the threshold temperature of 650 ° C., the effect of imparting a pre-strain is not recognized, and the steel strip is broken.
[0055]
The pre-strain imparting device is provided on the downstream side from the maximum steel strip temperature reaching point. If the prestrain imparting device is provided on the upstream side from the point where the maximum steel strip temperature is reached, the prestrain imparting effect is lost by heating to the above temperature, and it becomes impossible to prevent the occurrence of hip folding.
[0056]
Normally, the steel strip is heated and annealed at a temperature of 650 ° C. or higher in the heat annealing zone 4 and then cooled in the cooling zone 5 to a temperature lower than the threshold temperature T1. A temperature range defined by the present invention, which is a threshold temperature T1 or more and 650 ° C. or less, exists between the heating annealing zone 4 and the cooling zone 5. Therefore, the strain applying device is provided in at least one of the temperature portion between the heating annealing zone 4 and the cooling zone 5, that is, the temperature portion of the heating annealing zone 4, the temperature portion of the cooling zone 5, and the connecting portion of both. Usually, the heat-annealing zone 4 has a temperature range in which the steel strip temperature is not less than the threshold temperature T1 and not more than 650 ° C. Therefore, it is suitable to provide the strain imparting device 8 in the heat annealing furnace 4. When the steel strip temperature does not exceed the threshold temperature T1, a heating section is newly provided to heat the steel strip temperature to the above temperature range, thereby realizing the temperature range defined in the present invention, and then applying strain. May be.
[0057]
The strain can be applied with a bending roll. When the surface plastic strain is applied in a plurality of times, the surface plastic strain defined in the present invention is the sum of the amount of plastic strain applied to the surface of the metal strip in each strain application. That is, the surface plastic strain applied at the i-th time is expressed as ε_i, The surface plastic strain ε defined in the present invention is ε = Σε_iDefined by It is calculated as the sum of both compression strain and tensile strain. It is presumed that the sum is the same regardless of tension or compression because this mechanism for preventing hip breakage is caused by a transition independent of compression and tension.
[0058]
At that time, the roll (bending roll) needs to have a roll diameter and the number of rolls that can impart plastic strain to the steel strip in the strain imparting portion in a surface plastic strain of more than 0.1% and 1.5% or less. In the case of adding distortion by dividing a plurality of rolls, the required number N of rolls is determined by the following calculation formula.
[0059]
[Expression 1]

Where t: plate thickness mm, T: plate tension kg, w: plate width mm, σ: yield stress kg / mm², E; Young's modulus kg / mm²Where R is the radius of curvature when winding on the roll. For example, plate thickness 1mm, plate tension 1000kg, plate width 1000mm, yield stress 20kg / mm²Young's modulus 20000kg / mm²And when the curvature radius is 300mm,
1.33 ≦ N ≦ 19.95
In the end, the required number is 2 or more and 19 or less. Actually, there is a range in the steel strip thickness, yield stress, etc., so it is preferable to adjust the radius of curvature by adjusting the roll push-in amount so that the fluctuation can be accommodated. is there. In addition, when the number of rolls is 6 or more, the strain imparting effect is saturated, and the equipment cost, maintenance cost, etc. are increased. Therefore, the number of rolls is preferably selected in the range of 1 to 5, more preferably 2 to 3 preferable.
[0060]
When bending with a roll, select the roll diameter so that the radius of curvature of the metal band provided by at least one roll is 400 mm or less, and adjust the pushing amount of the roll to bend the metal band. Is preferred. In order to bend a metal strip with a curvature radius of 400 mm or less, it is necessary to use a roll having a roll diameter of 800 mm or less, and the number of rolls may be one or more. For example, a method of adjusting the pushing amount so that the metal band is sufficiently wound around the roll with a roll of φ800 mm (large diameter roll) and a method of adjusting the pushing amount with a roll having a roll diameter of φ400 mm can be exemplified. However, the pushing amount of the roll differs depending on the metal strip material, thickness, and the like. In order to increase the amount of surface plastic strain to be applied, it is preferable to increase the pushing amount of the roll or use a small-diameter roll. The roll diameter of the bending roll is preferably a small diameter roll of φ400 mm or less. In the vertical annealing furnace, the hearth roll diameter is usually φ800 mm or more, and even in a special dedicated furnace, it is more than φ500 mm, generally φ600 mm.
[0061]
By determining the roll diameter, the number of installations, and the installation location in this manner, the temperature range and the amount of plastic strain required in the present invention can be realized.
[0062]
In the continuous annealing line of FIG. 1, the strain imparting device 8 is installed in the final path near the exit side in the heating annealing furnace 4. FIG. 2 is a schematic view showing a strain applying device installed in the device of FIG. 1, and is an example in which three rolls are arranged. That is, the pre-strain imparting device 8 is composed of three rolls 11 to 13 that are staggeredly arranged on both sides of the steel strip 1 by shifting the position of the steel strip 1 through plate direction (vertical direction). The rolls 11 to 13 are configured to be independently movable in a direction substantially perpendicular to the pass line. 14 and 15 are hearth rolls.
[0063]
Using the apparatus of FIG. 2, at least one of the rolls 11 to 13 is pushed in the direction substantially perpendicular to the pass line beyond the pass line, thereby applying plastic strain to the surface of the steel strip. For example, as shown in FIG. 3 (a), the rolls 11 and 13 are disposed so as to substantially contact the pass line, and the roll 12 is pushed in the direction substantially perpendicular to the pass line beyond the pass line, thereby The band 1 is bent to introduce plastic strain on the surface. Alternatively, as shown in FIG. 3B, the roll 13 is disposed so as to be substantially in contact with the pass line, and the rolls 11 and 12 are respectively pushed in directions different from each other in the direction perpendicular to the pass line, that is, the roll 12 is pushed into the roll 11 side. The roll 11 is pushed in the direction opposite to the roll 12 beyond the pass line, thereby bending the steel strip 1 and introducing plastic strain on the surface thereof. 3 (a) and 3 (b), the roll 11 is disposed on the surface side of the steel strip 1 in contact with the sink roll 6. In this specification, “the roll is at the pass line position” means that the roll is at a position in contact with the pass line. 3A and 3B, the roll 12 is disposed on the same side as the hearth roll 15 with respect to the steel strip 1.
[0064]
As shown in FIGS. 3 (c) and 3 (d), each roll arrangement with respect to the steel strip 1 may be an arrangement opposite to the above (a) and (b).
[0065]
The amount of surface plastic strain to be introduced is determined by the bending curvature of the steel strip, and the bending curvature controls the distance between adjacent rolls in the direction of the metal strip, the roll diameter and its push amount (push amount exceeding the pass line). You can control it. In addition, obtain the relationship between the surface plastic strain amount and the metal strip material such as steel grade, operation variables such as plate thickness and temperature, the distance between adjacent rolls in the metal strip direction, roll diameter, roll push-in amount, etc. Then, a correspondence table is prepared, and the push-in amount of the roll in each case is set according to the operation variable value based on the correspondence table.
[0066]
The apparatus shown in FIG. 2 is an example in which three bending rolls are arranged, but the number of rolls is not limited to three and is preferably in the range of 1 to 5.
[0067]
When plastic strain is applied to the steel strip 1 by the strain applying device 8, the warp in the width direction of the steel strip 1 (C warpage) is affected. If the C warp is large, uniform cooling of the steel strip 1 in the cooling zone 5 is hindered, and the shape of the steel strip 1 is deteriorated or scratches are generated. Less is desirable.
[0068]
The inventors of the present invention also studied to make the steel strip shape (C warpage) after applying the strain good at the same time as applying the plastic strain. As a result, it became clear that it is effective to reduce the amount of strain applied by the final roll in the steel strip passing direction. When three rolls are used, as shown in FIGS. 3B and 3D, the roll 13, which is the final roll in the metal band passing direction, has a substantially pass line position (a position in contact with or near the pass line). ), The roll 12 that is an intermediate roll (upstream roll of the roll 13) is a position pushed into the roll 13 beyond the pass line, the roll 11 that is an entry roll (upstream roll of the roll 12), It is preferable to arrange at a position where it is pushed into the roll 12 side beyond the pass line.
[0069]
In the above, it is more preferable that the pushing amount (d1) of the roll 11 from the pass line and the pushing amount (d2) of the roll 12 from the pass line are substantially the same.
[0070]
As the amount of strain applied by the final roll, for example, when the plastic strain applied to the metal strip (the sum of the plastic strain applied by each roll) is about 0.5%, the plastic applied by the final roll An example in which the strain is about 0.1% can be illustrated. As an example of the roll arrangement, the diameter of the rolls 11 to 13 is φ250 mm, the distance between the rolls is 300 mm, the roll 13 is arranged at the pass line position, and the rolls 11 and 12 are pushed into the pass line by 50 mm. . However, the present invention is not limited to this.
[0071]
In order to reduce the amount of distortion imparted by the final roll, in combination with the roll pressing, or instead of the roll pressing method, the roll diameter of the bending roll arranged upstream of the roll is used as the roll diameter of the final roll. It may be made larger. For example, in FIG. 2, it is effective to make the roll diameter of the final roll larger than the roll diameters of the entrance roll and the intermediate roll. In FIG. 2, when the roll diameter of the final roll is increased, the roll arrangement (push-in method) of each roll is arranged at the pass line position as shown in FIGS. The intermediate roll may be pushed in the direction substantially perpendicular to the pass line beyond the pass line. As an example of this roll arrangement, the roll diameter of the rolls 11 and 12 is 150 mm, the roll diameter of the roll 13 is 400 mm, the rolls 11 and 13 are arranged at the pass line position, and the push amount of the roll 12 from the pass line An example in which is set to 100 mm can be illustrated. However, the present invention is not limited to this.
[0072]
Further, in combination with the above, or instead of the above, the roll may be arranged so that the distance between the intermediate roll and the final roll is larger than the distance between the entry roll and the intermediate roll (interval in the strip direction). .
[0073]
When two bending rolls are used, it is preferable to use a roll arrangement in which the hearth roll 15 can be used instead of the final roll 13. Moreover, when using 4-5 bending rolls, it is preferable to arrange | position a final roll in a pass line position from a viewpoint of making the plastic strain provided with a final roll small.
[0074]
However, since the strain applied by the final roll is determined by the relative positional relationship between the final roll and the upstream roll, if the amount of pushing of the upstream roll of the final roll is large, the final roll pass The position with respect to the line may be shifted from the pass line. Therefore, the position of the final roll is not limited to the pass line position.
[0075]
For example, in FIG. 4, the pushing positions of the rolls 22 to 24 with respect to the pass line are x1 to x3 (the pass line position is “0”, the movement amount to the right is “+”, and the movement amount to the left is “−”. When the push amount (| x1 |) of the roll 22 is small and the push amount (| x2 |) of the roll 23 is large, the strain applied by the final roll is the final roll 24 and the intermediate roll 23. Therefore, it is preferable to arrange the roll 24 so as to move to the left side of the pass line.
[0076]
In order to reduce the warpage of the steel strip on the exit side of the strain imparting device, it is necessary to impart the surface plastic strain as described above to the surface of the steel strip. The indentation amount of the bending roll to reduce the warpage of the steel strip is the indentation of the roll capable of achieving both the operation variable, the application of the predetermined surface plastic strain amount, and the C warpage prevention effect in the same manner as described in the application of the plastic strain. Create a correspondence table for the amount, and set the roll push-in amount according to the operation variable value based on this correspondence table, so that not only can you prevent hip breakage, but also prevent C warpage from occurring in the gas wiping nozzle. it can.
[0077]
By applying strain as described above, there is a high risk of hip breakage. Even if there is bending deformation due to the roll in a temperature range lower than the threshold temperature T1, no buckling defect occurs due to the strain effect, and In addition, since the temperature range in which the strain is applied is a temperature range in which there is no risk of the occurrence of hip folding, there is no possibility of hip folding at the time of applying the strain, so it can be said to be an ideal method for preventing hip folding.
[0078]
As described above, Patent Document 6 describes that a push roll is provided to correct the warping of the strip. However, Patent Document 6 targets warpage prevention in a hot dipping facility equipped with a support roll in the plating bath, and corrects the warpage of the band plate by using the support roll and the pushing roll together. A roll is not used, and the warping of the strip is not corrected only by the pushing roll. In addition, Patent Document 6 does not show that the required plastic strain is imparted to the surface of the strip, but also a sink roll is not provided in the plating bath, so that sufficient tension is stably applied to the strip. Therefore, it is considered that the required surface plastic strain cannot be stably applied to the surface of the strip.
[0079]
As described above, it has been explained that the bending is applied using the bending roll. Instead of a bending roll, plastic strain may be imparted using a rolling roll. In this case, the plastic strain applied to the steel strip may be more than 0.1% and 1.5% or less.
[0080]
In the continuous annealing line shown in FIG. 1, the steel strip 1 may be reheated in the OA / cooling zone 6. If there is a waist fracture risk part in the OA / cooling zone 6 or downstream thereof, it is necessary that the steel strip temperature between reaching the waist fracture risk part after applying strain should not be higher than the threshold temperature T1. is there.
[0081]
In the present embodiment of the present invention in which a strain imparting device is provided in the continuous annealing line, it is suitable for preventing the hip breakage of the BH steel sheet that is prone to “loose break” in the three-pass plate of the annealing furnace. The steel strip is not limited to the above steel plate, and the effect of widely preventing the waist break is exerted in the steel strip in which the “roll back” is likely to occur in the three-pass plate of the annealing furnace. The continuous annealing line is not limited to the continuous annealing line having the configuration shown in FIG. 1, and may be a continuous annealing line having another configuration. Further, the strain applying device described above may be replaced with a rolling device, and strain may be applied with a rolling roll. In this case, rolling strain of more than 0.1% and 1.5% or less may be applied to prevent hip breakage.
[0082]
The metal strip manufacturing apparatus having the metal strip heating means for installing the strain imparting device 8 is not limited to the continuous annealing line, and may be any metal strip manufacturing apparatus having the metal strip heating means, and the steel strip is a cold-rolled steel strip. Other than that, for example, it may be a hot-rolled steel strip or a metal strip other than the steel strip. According to the present invention, it is possible to effectively prevent a metal band having a yield point elongation at room temperature from breaking.
[0083]
【Example】
After annealing, a steel strip having a yield point elongation of 0.75 mm and a width of 1200 mm at normal temperature was prepared. Table 1 shows the chemical composition of the steel strip.
[0084]
[Table 1]

Using the continuous annealing line shown in FIG. 1, the steel strip has a line speed of 120 mpm and a tension of 2 kg / mm.²After annealing at an annealing temperature of 850 ° C., the pre-straining device 21 applies pre-strain under various conditions, then cools to about 400 ° C. in the cooling zone 5, and keeps it at 300 to 400 ° C. in the OA / cooling zone 6. After cooling, it was further temper-rolled with a temper rolling mill (not shown) to produce a cold-rolled steel strip. For comparison, a cold-rolled steel strip without prestrain was also produced. The cold-rolled steel strip (cold-rolled steel strip after annealing, no prestraining and no temper rolling) has a tensile material property at room temperature of 25 kg / mm upper yield point.²Lowering yield point 22kg / mm²The yield point elongation was 4.3%, and the temperature at which the yield point elongation disappeared (threshold temperature T1) was 440 ° C. according to the tensile test.
[0085]
The pre-strain imparting device 8 is arranged in the heat-annealing band 4, and instead of the device having three rolls shown in FIG. 2, as shown in FIG. A staggered device (# 1 to # 6 rolls from the upstream side with respect to the metal band passing plate direction) was used. The roll diameter is φ250 mm, the distance between adjacent rolls in the strip direction (axial distance; L1) is 300 mm, and the distance between the # 6 roll and the hearth roll 15 (axial distance; L2) is 1000 mm. Yes (hereinafter referred to as A device). The hearth roll diameter on the downstream side of the pre-strain imparting device is φ1000 mm.
[0086]
When using three rolls, the # 1 to # 3 rolls are retracted from the pass line and released, the # 6 roll is placed at the pass line position, and the # 4 roll and the # 5 roll are arranged as shown in FIG. As shown in Fig. 4, the sheet was pushed to a position shifted from the pass line, and the amount of pushing was adjusted.
[0087]
When five rolls are used, # 1 roll is not used, and # 2, # 4, and # 6 rolls are arranged at the pass line position, and are staggered in the middle of each of the rolls. The two rolls # 3 and # 5 were pushed over the pass line in a direction substantially perpendicular to the pass line.
[0088]
When 6 rolls are used, 6 rolls of # 2, # 4 and 6 rolls are arranged at the pass line position, and 3 rolls of # 1, # 3 and # 5 are arranged in a staggered manner with respect to each roll. Was pushed in a direction substantially perpendicular to the pass line, and the push amount was adjusted.
[0089]
In the A apparatus, the rolls # 1 to 3 are removed, rolls of φ100 mm are installed on the rolls # 4 to # 6 (hereinafter referred to as B apparatus), and the roll # 6 is disposed at the pass line position. The roll and # 5 roll were pushed into a position shifted from the pass line as shown in FIG. 3B, and the push amount was adjusted. Each of the # 4 to # 6 rolls was reinforced with a backup roll having a diameter of 400 mm from the viewpoint of roll rigidity.
[0090]
When using one roll, in the A apparatus, the rolls # 1 to # 6 are removed, and a φ1000 mm roll is arranged as the # 3 roll, and a φ100 mm roll is arranged as the # 6 roll (hereinafter referred to as C apparatus). No. 6 roll was pushed beyond the pass line to adjust the push amount. The # 6 roll was reinforced with a φ400 mm backup roll from the viewpoint of roll rigidity.
[0091]
The degree of waist folding of the steel strip obtained above was subjected to a press test simulating the press of an automobile door panel, and then visually observed, and was evaluated in 6 stages from 0 to 5 depending on the degree of waist breaking defect. As for the degree of hip break, 0 (no occurrence) is the best, and the larger the number, the worse and 5 the worst. For applications such as an automobile outer plate, a score of “1” or less is desirable, and for applications such as an automobile inner plate, “2” or less is desirable. Table 2 shows the pre-straining conditions and the evaluation results of the degree of hip folding.
[0092]
[Table 2]

In the invention example in which the pre-straining condition is within the scope of the present invention, the score of the degree of hip folding is 2 or less, and the degree of hip folding is prevented, or the degree is less than that of the comparative example that falls outside the scope of the present invention. Furthermore, there was little warpage of the steel strip after pre-straining, and there were no quality problems on the plate due to warpage of the steel strip.
[0093]
Furthermore, when the press test of the automobile door was carried out, with respect to the grades 0 and 1, there was no defect caused by the hip break in the continuous annealing line, and the grade 2 was also a defect caused by the hip break in the continuous annealing line. It was very minor. Thus, the steel strip which does not have a hip break was able to be manufactured by using this invention.
[0094]
In the present embodiment, surface plastic strain was imparted by roll bending, but the same effect can be obtained even if it is performed by another method (for example, rolling method).
[0095]
【The invention's effect】
According to the present invention, it is possible to reliably prevent low-back folding patterns that significantly deteriorate the surface properties even in a metal strip having an elongation at yield point, and to simplify defect inspection and the like.
[0096]
In addition, according to the present invention, since the metal band C warpage after prestraining can be reduced, it is possible to prevent the occurrence of quality problems on the plate due to the metal band C warpage.
[Brief description of the drawings]
FIG. 1 is a schematic view of a continuous annealing apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic diagram illustrating a configuration example of a strain applying device arranged in the device of FIG. 1;
FIG. 3 is a diagram for explaining a roll arrangement example of bending rolls.
FIG. 4 is a diagram for explaining another arrangement example of rolls used in the predistortion applying device.
FIG. 5 is a diagram illustrating a roll arrangement of the predistortion applying device used in the example.
FIG. 6 is a schematic view of a general continuous annealing apparatus.
[Explanation of symbols]
1 Metal strip (steel strip)
2 Rewinding device
3 Continuous annealing furnace
4 Heating means (heat annealing zone)
5 Cooling zone
6 OA / cooling zone
7 Winding device
8 Distortion device
11-13 Bending roll
14, 15 Hearth Roll

Claims (11)

A method for producing a metal strip having a yield point elongation at room temperature in a metal strip production apparatus having a metal strip heating means,
A heating step of heating the metal strip to the following threshold temperature or higher;
A strain imparting step of imparting plastic strain to the metal strip in a temperature range where the temperature of the metal strip is the following threshold temperature T1 or more and 650 ° C. or less ,
The plastic strain is applied using (a) a roll that bends and deforms the metal band, and the plastic strain has a surface plastic strain amount of more than 0.1% and not more than 1.5% of the metal band, or (b) a rolling strain imparted by the rolling rolls, the buckling occurs in the metal strip manufacturing facility, wherein the <br/> 該塑distortions amount is less than 0.1% 1.5% A method of manufacturing a metal strip to prevent .
However, the threshold temperature T1 is a temperature at which the elongation at the yield point of the metal strip disappears above the temperature. The said distortion | strain imparting process is provided in the maximum metal belt temperature reach | attainment point downstream of a heat-annealing process, and a waist break generation | occurrence | production risk part upstream, The generation | occurrence | production of the waist break in the metal belt manufacturing equipment of Claim 1 characterized by the above-mentioned A method for producing a metal strip.
However, the waist breakage risk part is a part where the metal band is broken when the plastic strain is not applied. The said plastic strain is divided | segmented and provided to 1 to 5 times, The manufacturing method of the metal strip which prevents the buckling generation | occurrence | production within the metal strip manufacturing facility of Claim 1 or 2 characterized by the above-mentioned. The said plastic strain imparting process is provided downstream of the maximum metal band temperature reaching point in the heat annealing process, and the occurrence of hip breakage in the metal band manufacturing facility according to any one of claims 1 to 3 , A method of manufacturing a metal strip to prevent . The metal band temperature is set to 650 ° C. or less from the strain applying step to the waist folding occurrence risk part, within the metal band manufacturing facility according to any one of claims 1 to 4. A method of manufacturing a metal strip that prevents the occurrence of hip breakage . When the plastic strain is applied using two or more rolls , the plastic strain has an amount of surface plastic strain applied by the final roll disposed on the steel strip passing side in the upstream direction of the final roll . It is provided so that it may become smaller than the surface plastic strain amount provided with a roll , The metal belt of the present invention for preventing waist breakage in the metal belt manufacturing facility according to any one of claims 1 to 5 , Production method. The plastic strain is applied using three rolls arranged in a staggered manner on both sides of the metal band in the metal band passing plate direction, and is disposed on the metal band sheet passing side out of the three rolls. the final roll is disposed substantially pass line position, entry side roll arranged metal strip through plate direction entry side is pushed beyond the pass line of the metal strip in the pass line substantially perpendicular direction, entering-side roll It arranged intermediate rolls between the last roll and is claimed in any one of claims 1 to 6, characterized in that pushed beyond the pass line of the metal strip in the pass line substantially perpendicular direction The manufacturing method of the metal strip which prevents the buckling generation | occurrence | production in the metal strip manufacturing equipment of this . The amount of push-in from the pass line of the entry side roll and the amount of push-in from the pass line of the intermediate roll are substantially the same, and the occurrence of hip breakage in the metal strip manufacturing facility according to claim 7 is prevented. A method for producing a metal strip. The roll break in the metal strip manufacturing facility according to claim 7 or 8 , wherein a roll diameter of the final roll among the three rolls is larger than a roll diameter of the entry roll and the intermediate roll. A method of manufacturing a metal strip that prevents generation . The plastic strain is applied using three rolls arranged in a staggered manner on both sides of the metal band in the metal band passing plate direction, and is disposed on the metal band sheet passing side out of the three rolls. The roll diameter of the final roll is larger than the roll diameter of the intermediate roll arranged between the entry roll and the entry roll and the final roll arranged on the metal band passing plate direction entry side. The manufacturing method of the metal strip which prevents the buckling generation | occurrence | production within the metal strip manufacturing equipment of any one of 1-6 . The final roll and entering-side roll is arranged substantially pass line position, the intermediate rolls, claim 10, characterized in that it is pushed beyond the pass line of the metal plate to the pass line substantially perpendicular direction The manufacturing method of the metal band which prevents the waist break generation | occurrence | production within the metal band manufacturing facility of description.

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