JP2004351484A

JP2004351484A - Method and equipment for producing hot-rolled steel strip

Info

Publication number: JP2004351484A
Application number: JP2003153098A
Authority: JP
Inventors: Yoshiro Tsuchiya; 義郎土屋; Tatsuya Jinnai; 達也陣内
Original assignee: JFE Steel Corp
Current assignee: JFE Steel Corp
Priority date: 2003-05-29
Filing date: 2003-05-29
Publication date: 2004-12-16

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and equipment for producing hot-rolled steel strips, which suppress a warpage to be generated at an end of a rough bar in rough-rolling and properly straighten the bar to send it to a finish-rolling process. <P>SOLUTION: The method for producing the hot-rolled steel strip comprises steps of: rough-rolling a slab into the rough bar by a rough-roller; roughly straightening the warpage of the rough bar with a first warpage straightening apparatus; finish-straightening the warpage of the rough bar with a second warpage straightening apparatus; heating the rough bar with an induction heating apparatus; and finish-rolling the rough bar continuously heated with a finish-rolling apparatus to produce the hot-rolled steel strip. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、粗圧延機と仕上圧延機の間において、反り矯正装置により粗バーの反りを矯正し、しかる後に加熱装置により粗バーの加熱を行なう熱延鋼帯の製造方法および製造装置に関するものである。
【０００２】
【従来の技術】
一般に熱延鋼帯は、加熱炉においてスラブを所定温度に加熱し、この加熱されたスラブを粗圧延機において所定厚さに圧延して粗バーとし、次いで粗バーをエッジヒーターやバーヒーター等の加熱装置により加熱した後、複数基の圧延スタンドからなる仕上圧延機において仕上圧延して所定厚さの熱延鋼帯とし、この熱延鋼帯をホットランテーブル上で冷却装置により冷却した後、コイラーで巻取ることにより製造される。
【０００３】
このような連続熱間圧延において、粗圧延機で所定厚さに圧延された粗バーの特に先端部に「反り」や「耳波／中伸び」などの形状不良が発生することがある。
【０００４】
粗バーに上述した形状不良が発生すると、粗バーを加熱装置により加熱する際に、粗バーが加熱装置に衝突し装置が損傷する恐れが生じる。
【０００５】
上述した問題を防止するために図２に示すような設備が知られている。図２に示す設備では、粗圧延機１と仕上圧延機１０との間のエッジヒーター９の入側に平坦度矯正装置６が設けられており、平坦度矯正装置６の入側および出側には反り検出器４ｂ、４ｃが設けられている（例えば、特許文献１参照。）。
【０００６】
粗圧延機１によって粗圧延された粗バー２の先端部に生じた「反り」や「耳波／中伸び」などの形状不良は、平坦度矯正装置６の入側および出側に設けられた反り検出器４ｂ、４ｃによって検出され、その検出信号に基づいて平坦度矯正装置６が制御され、粗バー２の平坦度不良が矯正される。このようにして平坦度不良が矯正された粗バー２はエッジヒーター９に送り込まれ、エッジヒーター９によりその幅方向両端部が加熱されて、幅方向の温度分布が均一になった後、仕上圧延機１０によって所定の板厚に仕上圧延される。
【０００７】
【特許文献１】
特開平５−３２９５１９号公報
【０００８】
【発明が解決しようとする課題】
しかしながら、上記した従来技術には次のような問題がある。
【０００９】
粗圧延機１によって粗圧延された粗バー２の先端部に生じた「反り」や「耳波／中伸び」などの形状不良が大きいと、平坦度矯正装置６による粗バー２の反りの矯正が不充分となり、反りを生じたままの粗バーが下流側に送られてエッジヒーター９などの下流側の設備を壊すという問題があった。
【００１０】
また、上記形状不良が大きいと、平坦度矯正装置６の入側の上部ガイドと下ロール間に粗バーが挟まって進行不能になったり、平坦度矯正装置６に噛み込みすらできないという問題があった。
【００１１】
したがって本発明の目的は、粗圧延により粗バーの先端部に生じる反りを抑制するとともに適切に矯正して仕上圧延工程に送ることができる熱延鋼帯の製造方法および製造装置を提供することにある。
【００１２】
【課題を解決するための手段】
上記の課題を解決するための本発明の熱延鋼帯の製造方法および製造装置は以下のような特徴を有する。
【００１３】
（１）スラブを粗圧延機により粗圧延して粗バーとした後、第１の反り矯正装置により前記粗バーの反りを粗矯正し、次いで第２の反り矯正装置により前記粗バーの反りを仕上矯正した後、誘導加熱装置により前記粗バーを加熱し、引き続き加熱された粗バーを仕上圧延機により仕上圧延して熱延鋼帯とすることを特徴とする熱延鋼帯の製造方法。
【００１４】
（２）第１の反り矯正装置により、粗バーの反り量が第２の反り矯正装置の入側許容値以下になるように粗圧延後の粗バーの反りを粗矯正するとともに、第２の反り矯正装置により、粗バーの反り量が誘導加熱装置の入側許容値以下になるように粗バーの反りを仕上矯正することを特徴とする上記（１）に記載の熱延鋼帯の製造方法。
【００１５】
（３）第１の反り矯正装置の出側に粗バーの反り検出手段を設け、該反り検出手段により検出された粗バーの反り量が第２の反り矯正装置の入側許容値を超えている場合には、第２の反り矯正装置および誘導加熱装置を退避させて粗バーを通板させることを特徴とする上記（１）に記載の熱延鋼帯の製造方法。
【００１６】
（４）スラブを粗圧延して粗バーとする粗圧延機と、該粗圧延機直後に設置された粗バーの反りを粗矯正するための第１の反り矯正装置と、前記粗バーの反りを仕上矯正するための第２の反り矯正装置と、該第２の反り矯正装置の後に設置された反り矯正後の粗バーを加熱するための誘導加熱装置と、加熱された粗バーを仕上圧延して熱延鋼帯とする仕上圧延機とを備えたことを特徴とする熱延鋼帯の製造装置。
【００１７】
（５）第１の反り矯正装置の出側に反り検出手段を備えるとともに、第２の反り矯正装置および誘導加熱装置を粗バーの板厚方向または板幅方向に退避可能な構造とすることを特徴とする上記（４）に記載の熱延鋼帯の製造装置。
【００１８】
【発明の実施の形態】
図１は、本発明の熱延鋼帯の製造装置の一実施形態を示す側面図である。
【００１９】
この熱延鋼帯の製造装置は、粗圧延機１の直後に粗バー２の反りを矯正するための第１の反り矯正装置３と、この第１の反り矯正装置３の出側に設置された反り検出器４ａと、粗バー２の反りを矯正するための第２の反り矯正装置７と、この第２の反り矯正装置７の入側および出側に設けられた反り検出器４ｂ、４ｃと、反り検出器４ａ、４ｂ、４ｃの出力より粗バー２の反り矯正を制御する制御装置５と、この第２の反り矯正装置７に続いて配置される反りを矯正された粗バー２を加熱するための誘導加熱装置８と、加熱された粗バー２を仕上圧延して熱延鋼帯とする仕上圧延機１０とを備えている。
【００２０】
前記第１の反り矯正装置３は、粗圧延機１の直後に設置されて粗バー２の反りを粗矯正するためのもので、粗バー先端部の反りが成長する前に矯正を行う。そのためには第１の反り矯正装置３をできるだけ粗圧延機１のロールバイト直後に設けて粗バーの反りを抑え込むことが好ましい。
【００２１】
第１の反り矯正装置３の構造は、本実施形態のように後述する第２の反り矯正装置７と同様に粗圧延機１の直後のガイド３ａとレベラー３ｂとで構成される場合もあるし、ガイドだけの場合もある。ガイドだけの構造でも、粗バーの長手方向の一部分を粗圧延機で圧延している状態で、粗バー先端がガイドに当たるので反り矯正効果が得られる。耳波／中伸びのような平坦度不良は矯正できないが反りの問題が圧倒的に多いのでガイドだけの構造でもよい。ガイドの後段にレベラーを設置する構成とすることにより耳波／中伸びのような平坦度不良を矯正することができてより好ましい。
【００２２】
前記第２の反り矯正装置７は、第１の反り矯正装置３により粗矯正した粗バーの反りを仕上矯正するためのもので、本実施形態では上ロール２本、下ロール３本のロールより構成されるレベラー７ｂとこのレベラー最上流のロール直前に設けられた粗バーの先端をレベラーに案内するためのガイド７ａとからなる。レベラー７ｂのロールの本数は第２の反り矯正装置７の入側許容値等の設計条件より決定されるもので、本実施形態の本数に限られない。
【００２３】
上記熱延鋼帯の製造装置を使用して本発明法を実施する場合には、粗圧延機を出た粗バー２は、まず第１の反り矯正装置３に通板されて、第１の反り矯正装置３の出側に設けられた反り検出器４ａによって検出される粗バーの反り量が第２の反り矯正装置７の入側許容値以下になるように矯正される。
【００２４】
次に反り検出器４ａによって検出された粗バー先端部の実際の反り量が予め定められた第２の反り矯正装置７の入側許容値以内であれば、粗バーを第２の反り矯正装置７以降の装置に通板させる。しかしながらこの検出された粗バー先端部の実際の反り量が予め定められた入側許容値を超えていたならば、制御装置５により第２の反り矯正装置７を粗バーの板厚方向に退避させ、さらに誘導加熱装置８を粗バーの板幅方向に退避させて粗バーを通板させる。このようにして通板させた粗バーは誘導加熱装置８による加熱を行うことができないために温度が低いので、本材料は仕上圧延温度を低く変更したり、目標仕上厚を厚く変更したり、またはその両方を行って仕上圧延可能な材料に変更することもある。
【００２５】
さらに、第２の反り矯正装置７に通板された粗バーは、第２の反り矯正装置７により粗バー先端部の反りや耳波／中伸びなどの平坦度不良が矯正される。その際、反り検出器４ｂによって検出された粗バー２の反りの程度によって、制御装置５により第２の反り矯正装置７のレベラー７ｂが適切に制御される。
【００２６】
反り検出器４ｃによって検出された粗バー先端部の実際の反り量が予め定められた誘導加熱装置８の入側許容値以内であれば、粗バーを誘導加熱装置８に通板させる。しかしながらこの検出された粗バー先端部の実際の反り量が予め定められた入側許容値を超えていたならば、粗バーの通板を中断して誘導加熱装置を退避させるか、粗バーの通板を中断し、且つ粗バーを逆送させ、再度第２の反り矯正装置７にて粗バーを矯正することもある。
【００２７】
粗バーの反りを矯正するための第２の反り矯正装置７と、反りを矯正された粗バーを加熱するための誘導加熱装置８は、退避指令から退避完了までの時間を短くするために、粗バー板厚方向に上下動ができる退避可能な構造であることが好ましいが、粗バー板幅方向に退避する構造でも、退避が完了するまで粗バ−の装置への進入を遅らせればよい。
【００２８】
本実施形態では、反り検出器４ａ、４ｂ、４ｃが反りの絶対値を測定できる装置として記載したが、反り検出器４ａ、４ｂ、４ｃはこれに限らない。例えば反り検出器４ａ、４ｂについていえば、粗バーの粗厚＋反り量が第２の反り矯正装置７の入側許容値（例えば１５０ｍｍ）以下か以上かが識別できる方式でよいし、反り検出器４ｃについていえば、粗バーの粗厚＋反り量が誘導加熱装置８の入側許容値（例えば５０ｍｍ）以下か以上かが識別できる方式でもよい。このような簡易な反り検出器としては、例えば粗バー先端部の反りが第２の反り矯正装置７の入側許容値や誘導加熱装置８の入側許容値を超えると粗バー幅方向の上空に張られたチェーンに当たってそれを検出できるような構造でよい。
【００２９】
また、後に記載の実施例の表１からもわかるように反り検出器４ａ出力と反り検出器４ｂ出力とはほとんど変わらないので、反り検出器４ｂは設置せずに反り検出器４ａで代表させてもよい。反り検出器４ａを代表としたのは、反り検出器４ａの出力によって、第２の反り矯正装置７さらには誘導加熱装置８を退避させるか、またはこれらの装置はそのままで粗バーを通板させるかの判定を少しでも早くでき、第２の反り矯正装置７さらには誘導加熱装置８の退避動作完了を粗バーの進行を中断して待機させる、というようなロス時間をなくすか、少なくすることができるからである。
【００３０】
前記誘導加熱装置８は、粗バーの両端部を加熱するエッジヒーターの場合もあるし、粗バー全体を幅方向に加熱するバーヒーターの場合もあるし、エッジヒーターおよびバーヒーターの併用の場合もある。
【００３１】
【実施例】
加熱炉において、１２００℃の温度に加熱された厚さ２３５ｍｍ、幅１０５０ｍｍ、長さ９２００ｍｍの寸法の炭素鋼からなるスラブを、図１に示した熱延鋼帯の製造装置により、粗圧延機１において粗圧延し、粗厚３２ｍｍ、幅１０５０ｍｍの粗バー２とした。次いで粗バー２を第１の反り矯正装置３により粗矯正を行い、第２の反り矯正装置７により仕上矯正を行ってその反りおよび平坦度を矯正した。その後、バーヒーター８によって粗バーの幅方向全体を所定の温度に加熱した後、仕上圧延機１０によって仕上圧延して、目標仕上厚さ２．０ｍｍ、幅１０５０ｍｍの熱延鋼帯を製造した。
【００３２】
表１に上記のように製造した熱延鋼帯について、反り検出器４ａ、４ｂ、４ｃの出力と制御装置の判定結果について示す。第２の反り矯正装置の入側許容値は１５０ｍｍであり、誘導加熱装置の入側許容値は５０ｍｍである。
【００３３】
表１において、ケース１〜３は本発明例であり、ケース４は第１の反り矯正装置３が配置されない場合の比較例である。
【００３４】
【表１】

【００３５】
ケース１および２は、第１の反り矯正装置により、粗バーの反り量が第２の反り矯正装置の入側許容値以下になるように粗圧延後の粗バーの反りが粗矯正されている（反り検出器４ａの出力結果より）とともに、第２の反り矯正装置により、粗バーの反り量が誘導加熱装置の入側許容値以下になるように粗バーの反りが仕上矯正されている（反り検出器４ｃの出力結果より）。
【００３６】
ケース３は、反り検出器４ａにより検出された粗矯正後の粗バーの反り量が第２の反り矯正装置の入側許容値を超えているので、第２の反り矯正装置および誘導加熱装置を退避させて粗バーを通板させ、仕上圧延は目標仕上厚を２．３ｍｍに変更した。
【００３７】
ケース４は、従来技術と同様に、粗矯正を行わなかったため、反り検出器４ａにより検出された粗バーの粗圧延機出側反り量が第２の反り矯正装置の入側許容値を超えているので、粗バーの通板を中止させて粗バーを通板ラインから外した。
【００３８】
次に、本発明の粗バーの反りを粗矯正するための第１の反り矯正装置と、前記粗バーの反りを仕上矯正するための第２の反り矯正装置を用いた熱延鋼帯の製造を長期間行った。その結果、粗バーを通板ラインから外すようなトラブルの発生頻度は５回／月であったものが０回／月となった。
【００３９】
【発明の効果】
以上述べたように本発明によれば、粗圧延により粗バーの先端部に生じる反りを抑制するとともに適切に矯正して仕上圧延工程に送ることができ、歩留まりが向上するとともに、安定した熱延鋼帯の製造が可能となる。
【図面の簡単な説明】
【図１】本発明の熱延鋼帯の製造装置の一実施形態を示す側面図
【図２】従来の平坦度矯正装置を示す側面図
【符号の説明】
１粗圧延機
２粗バー
３第１の反り矯正装置
３ａガイド
３ｂレベラー
４ａ、４ｂ、４ｃ反り検出器
５制御装置
６平坦度矯正装置
７第２の反り矯正装置
７ａガイド
７ｂレベラー
８誘導加熱装置
９エッジヒーター
１０仕上圧延機[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for manufacturing a hot-rolled steel strip in which a warp correcting device corrects a warp of a rough bar between a rough rolling mill and a finish rolling mill, and then heats the rough bar by a heating device. It is.
[0002]
[Prior art]
Generally, a hot-rolled steel strip heats a slab to a predetermined temperature in a heating furnace, rolls the heated slab to a predetermined thickness in a rough rolling mill to form a coarse bar, and then converts the coarse bar to an edge heater, a bar heater, or the like. After being heated by a heating device, it is finish-rolled in a finishing rolling mill comprising a plurality of rolling stands to form a hot-rolled steel strip having a predetermined thickness, and the hot-rolled steel strip is cooled on a hot run table by a cooling device. It is manufactured by winding in.
[0003]
In such continuous hot rolling, shape defects such as “warpage” and “ear wave / medium elongation” may occur at the tip of a coarse bar rolled to a predetermined thickness by a rough rolling mill.
[0004]
When the above-mentioned shape defect occurs in the rough bar, when the rough bar is heated by the heating device, the rough bar collides with the heating device, and the device may be damaged.
[0005]
In order to prevent the above-described problem, there is known a facility as shown in FIG. In the equipment shown in FIG. 2, a flatness correction device 6 is provided on the entrance side of the edge heater 9 between the rough rolling mill 1 and the finish rolling mill 10, and on the entry side and the exit side of the flatness correction device 6. Are provided with

warp detectors

4b and 4c (see, for example, Patent Document 1).
[0006]
Shape defects such as “warpage” and “ear wave / medium elongation” generated at the tip of the rough bar 2 roughly rolled by the rough rolling machine 1 were provided on the entrance side and the exit side of the flatness correction device 6. The flatness correcting device 6 is detected by the

warp detectors

4b and 4c based on the detection signals, and the flatness defect of the rough bar 2 is corrected. The rough bar 2 in which the flatness defect has been corrected in this way is sent to the edge heater 9, and both ends in the width direction are heated by the edge heater 9, and the temperature distribution in the width direction becomes uniform. The roll is finish-rolled to a predetermined thickness by the mill 10.
[0007]
[Patent Document 1]
Japanese Patent Application Laid-Open No. Hei 5-329519
[Problems to be solved by the invention]
However, the above-described prior art has the following problems.
[0009]
If there is a large shape defect such as “warpage” or “ear wave / medium elongation” generated at the tip of the rough bar 2 coarsely rolled by the rough rolling machine 1, the flatness correction device 6 corrects the warpage of the rough bar 2. However, there is a problem that the coarse bar with warpage is sent to the downstream side to break the downstream equipment such as the edge heater 9.
[0010]
In addition, when the shape defect is large, there is a problem that the rough bar is caught between the upper guide and the lower roll on the entry side of the flatness correction device 6 to make it impossible to advance, and that the flatness correction device 6 cannot be bitten. Was.
[0011]
Therefore, an object of the present invention is to provide a method and an apparatus for manufacturing a hot-rolled steel strip which can suppress warpage generated at the leading end of a rough bar by rough rolling and can appropriately correct the warp and send it to a finish rolling step. is there.
[0012]
[Means for Solving the Problems]
The method and apparatus for manufacturing a hot-rolled steel strip according to the present invention for solving the above-mentioned problems have the following features.
[0013]
(1) After the slab is roughly rolled by a rough rolling machine to form a rough bar, the warpage of the rough bar is roughly corrected by a first warp straightening device, and then the warpage of the rough bar is reduced by a second warp straightening device. A method for producing a hot-rolled steel strip, wherein after finishing the straightening, the rough bar is heated by an induction heating device, and then the heated rough bar is finish-rolled by a finishing mill to form a hot-rolled steel strip.
[0014]
(2) The first warp correcting device roughly corrects the warpage of the rough bar after the rough rolling so that the warp amount of the rough bar is equal to or less than the allowable value on the entry side of the second warp correcting device. The production of the hot-rolled steel strip according to the above (1), wherein the warp of the rough bar is finished and corrected by the warp correcting device so that the amount of warpage of the rough bar is equal to or less than the allowable value on the inlet side of the induction heating device. Method.
[0015]
(3) A coarse bar warp detecting means is provided on the output side of the first warp straightening device, and the amount of warpage of the coarse bar detected by the warp detecting means exceeds the allowable value on the entrance side of the second warp straightening device. If so, the method for manufacturing a hot-rolled steel strip according to the above (1), wherein the second warp straightening device and the induction heating device are retracted and the coarse bar is passed through.
[0016]
(4) a rough rolling mill for roughly rolling a slab to obtain a rough bar, a first warpage straightening device for roughly correcting the warpage of the rough bar installed immediately after the rough rolling machine, and a warpage of the rough bar A second warp straightening device for finish straightening, an induction heating device for heating a warped straight bar installed after the second warp straightening device, and finish rolling of the heated rough bar A hot-rolled steel strip manufacturing apparatus comprising:
[0017]
(5) A structure in which a warp detecting means is provided on the exit side of the first warp straightening device, and the second warp straightening device and the induction heating device have a structure capable of retracting in the thickness direction or the width direction of the rough bar. The apparatus for producing a hot-rolled steel strip according to the above (4), which is characterized in that:
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a side view showing an embodiment of the apparatus for manufacturing a hot-rolled steel strip according to the present invention.
[0019]
The apparatus for manufacturing a hot-rolled steel strip is provided immediately after the rough rolling mill 1 with a first warp straightening device 3 for straightening the warp of the rough bar 2, and installed on the exit side of the first warp straightening device 3. Warp detector 4a, a second warp correcting device 7 for correcting the warpage of the rough bar 2, and

warp detectors

4b and 4c provided on the entrance side and the exit side of the second warp correction device 7, respectively. And a control device 5 for controlling the warp correction of the rough bar 2 based on the outputs of the

warp detectors

4a, 4b and 4c, and the warped straight bar 2 disposed following the second warp correction device 7. An induction heating device 8 for heating and a finishing mill 10 for finish-rolling the heated rough bar 2 to form a hot-rolled steel strip are provided.
[0020]
The first warp straightening device 3 is provided immediately after the rough rolling mill 1 to roughly correct the warpage of the rough bar 2 and performs straightening before the warp of the rough bar tip grows. For this purpose, it is preferable that the first warp straightening device 3 be provided as soon as possible after the roll bite of the rough rolling mill 1 to suppress the warpage of the rough bar.
[0021]
The structure of the first warp straightening device 3 may be constituted by a guide 3a and a leveler 3b immediately after the rough rolling mill 1 as in a second warp straightening device 7 described later as in this embodiment. , Sometimes just a guide. Even with a structure having only a guide, the tip of the rough bar hits the guide in a state where a part of the rough bar in the longitudinal direction is rolled by the rough rolling mill, so that a warp correcting effect can be obtained. A flatness defect such as an ear wave / middle elongation cannot be corrected, but the problem of warpage is overwhelming, so that a structure having only a guide may be used. It is more preferable that a leveler is provided at a stage subsequent to the guide because flatness defects such as ear waves / middle elongation can be corrected.
[0022]
The second warp straightening device 7 is for finishing and correcting the warpage of the rough bar coarsely corrected by the first warp straightening device 3, and in the present embodiment, is composed of two upper rolls and three lower rolls. It comprises a leveler 7b and a guide 7a for guiding the leading end of a coarse bar provided immediately before the uppermost roll of the leveler to the leveler. The number of rolls of the leveler 7b is determined based on design conditions such as the allowable value on the entrance side of the second warp straightening device 7, and is not limited to the number in the present embodiment.
[0023]
When the method of the present invention is carried out using the above-described apparatus for manufacturing a hot-rolled steel strip, the rough bar 2 that has exited the rough rolling mill is first passed through a first warp straightening device 3 and is subjected to a first warping. The warpage of the coarse bar detected by the warp detector 4a provided on the output side of the warp straightening device 3 is corrected so as to be equal to or less than the allowable value of the second warp correcting device 7 on the incoming side.
[0024]
Next, if the actual amount of warpage of the rough bar tip portion detected by the warp detector 4a is within the predetermined allowable value on the entry side of the second warp straightening device 7, the rough bar is moved to the second warp straightening device. 7 is passed through the device. However, if the detected amount of warpage of the coarse bar tip exceeds a predetermined allowable value on the entry side, the controller 5 retreats the second warp straightening device 7 in the thickness direction of the rough bar. Then, the induction heating device 8 is retracted in the width direction of the coarse bar to pass the coarse bar. Since the coarse bar passed in this way has a low temperature because it cannot be heated by the induction heating device 8, the present material changes the finish rolling temperature to a low value or changes the target finish thickness to a large value. Alternatively, the material may be changed to a material that can be finish-rolled by performing both.
[0025]
Further, the coarse bar passed through the second warp straightening device 7 is corrected by the second warp straightening device 7 for flatness defects such as warpage of the rough bar tip and ear waves / middle elongation. At this time, the leveler 7b of the second warp straightening device 7 is appropriately controlled by the control device 5 according to the degree of warpage of the rough bar 2 detected by the warp detector 4b.
[0026]
If the actual amount of warpage of the coarse bar tip detected by the warp detector 4c is within a predetermined allowable value on the entry side of the induction heating device 8, the coarse bar is passed through the induction heating device 8. However, if the detected amount of warpage of the rough bar tip portion exceeds a predetermined allowable value on the entrance side, the rough bar passing is interrupted to retract the induction heating device, or In some cases, the passing of the plate is interrupted, the coarse bar is reversed, and the second warp correcting device 7 corrects the coarse bar again.
[0027]
The second warp correcting device 7 for correcting the warpage of the rough bar and the induction heating device 8 for heating the rough bar whose warp has been corrected are provided in order to shorten the time from the evacuation order to the evacuation completion. It is preferable to have a retractable structure capable of moving up and down in the coarse bar plate thickness direction. However, even in a structure in which the coarse bar plate is retracted in the width direction, the entry of the coarse bar into the device may be delayed until the retraction is completed. .
[0028]
In the present embodiment, the

warp detectors

4a, 4b, and 4c have been described as devices capable of measuring the absolute value of the warp, but the

warp detectors

4a, 4b, and 4c are not limited thereto. For example, with respect to the

warp detectors

4a and 4b, a method capable of discriminating whether the coarse thickness of the coarse bar + the warp amount is equal to or less than the entrance allowable value (for example, 150 mm) of the second warp straightening device 7 may be used. As for the heater 4c, a method may be used in which it is possible to identify whether or not the coarse thickness of the coarse bar + the amount of warpage is equal to or less than the entrance allowable value (for example, 50 mm) of the induction heating device 8. As such a simple warp detector, for example, if the warp at the leading end of the rough bar exceeds the inlet side allowable value of the second warp straightening device 7 or the inlet side allowable value of the induction heating device 8, the sky above the rough bar width direction The structure may be such that it can be detected by hitting a chain attached to the chain.
[0029]
Further, as can be seen from Table 1 of the embodiment described later, since the output of the warp detector 4a and the output of the warp detector 4b hardly change, the warp detector 4b is not provided and is represented by the warp detector 4a. Is also good. The reason why the warp detector 4a is used as a representative is that the second warp straightening device 7 and the induction heating device 8 are retracted by the output of the warp detector 4a, or the coarse bar is passed as it is. It is possible to eliminate or reduce the loss time in which the evacuation operation of the second warp straightening device 7 and the induction heating device 8 is stopped by interrupting the progress of the coarse bar. Because it can be.
[0030]
The induction heating device 8 may be an edge heater for heating both ends of the coarse bar, a bar heater for heating the entire coarse bar in the width direction, or a combination of the edge heater and the bar heater. is there.
[0031]
【Example】
In a heating furnace, a slab made of carbon steel having a thickness of 235 mm, a width of 1050 mm, and a length of 9200 mm heated to a temperature of 1200 ° C. was converted into a rough rolling mill 1 by a hot-rolled steel strip manufacturing apparatus shown in FIG. Was rough-rolled to obtain a rough bar 2 having a rough thickness of 32 mm and a width of 1050 mm. Next, the rough bar 2 was roughly corrected by the first warp straightening device 3 and the finish straightening was performed by the second warp straightening device 7 to correct the warp and flatness. Thereafter, the entire width direction of the coarse bar was heated to a predetermined temperature by the bar heater 8 and then finish-rolled by the finish rolling mill 10 to produce a hot-rolled steel strip having a target finish thickness of 2.0 mm and a width of 1050 mm.
[0032]
Table 1 shows the outputs of the

warp detectors

4a, 4b, and 4c and the results of determination by the control device for the hot-rolled steel strip manufactured as described above. The entrance allowance of the second warp straightening device is 150 mm, and the entrance allowance of the induction heating device is 50 mm.
[0033]
In Table 1, Cases 1 to 3 are examples of the present invention, and Case 4 is a comparative example in which the first warp correcting device 3 is not provided.
[0034]
[Table 1]

[0035]
In the cases 1 and 2, the warpage of the rough bar after the rough rolling is roughly corrected by the first warp correcting device so that the warp amount of the coarse bar is equal to or less than the allowable value on the entry side of the second warp correcting device. Along with (from the output of the warp detector 4a), the warpage of the coarse bar is corrected by the second warp correction device so that the amount of warpage of the coarse bar is equal to or less than the allowable value on the inlet side of the induction heating device ( From the output result of the warp detector 4c).
[0036]
Since the amount of warpage of the coarse bar after the rough correction detected by the warp detector 4a exceeds the allowable value of the second warp correction device on the inlet side, the case 3 includes the second warp correction device and the induction heating device. After retreating, the coarse bar was passed through, and the finish rolling changed the target finish thickness to 2.3 mm.
[0037]
In case 4, as in the prior art, since the rough straightening was not performed, the amount of warpage of the rough bar detected by the warp detector 4a on the rough rolling mill exceeds the allowable value on the incoming side of the second warp straightening device. Therefore, the passing of the coarse bar was stopped and the coarse bar was removed from the vertical line.
[0038]
Next, production of a hot-rolled steel strip using the first warp straightening device for roughly correcting the warpage of the rough bar of the present invention and the second warp straightening device for finish-correcting the warpage of the rough bar. For a long time. As a result, the frequency of occurrence of troubles such as removing the coarse bar from the plate line was 5 times / month but 0 times / month.
[0039]
【The invention's effect】
As described above, according to the present invention, it is possible to suppress the warpage generated at the leading end of the rough bar by rough rolling, to correct the warp appropriately, and to send it to the finish rolling step, thereby improving the yield and improving the stable hot rolling. Production of steel strip becomes possible.
[Brief description of the drawings]
FIG. 1 is a side view showing an embodiment of a hot-rolled steel strip manufacturing apparatus according to the present invention. FIG. 2 is a side view showing a conventional flatness correction device.
DESCRIPTION OF SYMBOLS 1 Rough rolling mill 2 Rough bar 3 First warp straightening device 3a

Guide 3b Leveler

4a, 4b, 4c Warp detector 5 Control device 6 Flatness straightening device 7 Second warp straightening device 7a Guide 7b Leveler 8 Induction heating device 9 Edge heater 10 Finish rolling mill

Claims

After the slab was roughly rolled by a rough rolling machine to obtain a rough bar, the warpage of the rough bar was roughly corrected by a first warp straightening device, and then the warpage of the coarse bar was finish-corrected by a second warp straightening device. Thereafter, the rough bar is heated by an induction heating device, and then the heated rough bar is finish-rolled by a finish rolling mill to form a hot-rolled steel strip.

The first warp correcting device roughly corrects the warpage of the rough bar after the rough rolling so that the amount of warpage of the rough bar is equal to or less than the allowable value on the entry side of the second warp correcting device, and the second warp correcting device The method for producing a hot-rolled steel strip according to claim 1, wherein the warp of the rough bar is corrected so that the warp amount of the rough bar becomes equal to or less than an allowable value on the entrance side of the induction heating device.

Provide a coarse bar warp detection means on the output side of the first warp straightening device, and when the warp amount of the rough bar detected by the warp detection means exceeds the entrance side allowable value of the second warp straightening device. The method of manufacturing a hot-rolled steel strip according to claim 1, wherein the second straightening device and the induction heating device are retracted and the coarse bar is passed through.

A rough rolling machine for roughly rolling a slab to obtain a rough bar, a first warpage straightening device for roughly correcting the warpage of the rough bar installed immediately after the rough rolling machine, and a finish straightening for the warpage of the rough bar; A second warp straightening device, an induction heating device installed after the second warp straightening device for heating the warped rough bar, and finish-rolling and heating the heated rough bar. An apparatus for manufacturing a hot-rolled steel strip, comprising: a finish rolling mill for forming a rolled steel strip.

It is characterized in that a warp detecting means is provided on the exit side of the first warp straightening device, and the second warp straightening device and the induction heating device are structured to be retractable in the thickness direction or the width direction of the rough bar. An apparatus for manufacturing a hot-rolled steel strip according to claim 4.