JP2003145203A - Method for manufacturing hot-rolled steel strip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a hot-rolled steel strip having a plurality of levels of material characteristics along a longitudinal direction by a single rolling chance. SOLUTION: The method for manufacturing the hot-rolled steel strip has a process for the finish rolling of a bloom or a thin steel slab roughly rolled by a roughing mill 2 by using a finishing mill 4. The finish rolling is carried out after heating or cooling the bloom (rough bar) or steel thin slab after the rough rolling with the rough bar heating apparatus or the cooling apparatus 3 provided in the inlet side of the finishing mill 4 so that the two or more levels of the temperature might change along longitudinal direction.

Description

【発明の詳細な説明】Detailed Description of the Invention

【０００１】[0001]

【発明の属する技術分野】本発明は、熱延鋼帯の製造方
法、特に１回の圧延チャンスで長手方向に２水準以上の
材料特性を有する熱延鋼帯を製造する方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a hot-rolled steel strip, and more particularly to a method for producing a hot-rolled steel strip having material characteristics of two or more levels in the longitudinal direction in one rolling opportunity.

【０００２】[0002]

【従来の技術】一般に、熱延鋼帯は、前工程で製造され
たスラブを、加熱炉で所定の温度に再加熱した後あるい
は加熱炉を通さず直接に、複数の圧延機で粗圧延して所
定の厚さの鋼片（粗バーと呼ばれる）とした後、複数の
スタンドからなる連続熱間圧延機で所定の温度（仕上温
度と呼ばれる）で所定の板厚に仕上圧延し、ランナウト
テーブルで所定の温度（巻取温度と呼ばれる）まで冷却
してコイラーで巻取って製造される。2. Description of the Related Art Generally, hot-rolled steel strip is roughly rolled by a plurality of rolling mills after reheating the slab manufactured in the previous step to a predetermined temperature in a heating furnace or directly without passing through the heating furnace. To a predetermined thickness (called a rough bar) and then finish rolling to a predetermined plate thickness at a predetermined temperature (called the finishing temperature) with a continuous hot rolling mill consisting of multiple stands, and a runout table. It is manufactured by cooling to a predetermined temperature (called a winding temperature) and winding with a coiler.

【０００３】最近では、粗圧延を省略するために、粗バ
ー相当の厚みに鋳造された薄スラブを直接仕上圧延する
方法も実用化されている。Recently, in order to omit the rough rolling, a method of directly finishing rolling a thin slab cast to a thickness corresponding to a rough bar has been put into practical use.

【０００４】熱延鋼帯の材料特性に大きな影響を及ぼす
熱延条件としては、加熱炉温度（加熱炉を通さない場合
は、スラブの熱履歴）、仕上温度、圧下率、圧延後の冷
却速度、巻取温度があるが、これまではこれらの条件を
制御することにより所定の材料特性を長手方向や幅方向
に均一に得るための努力が払われてきた。The hot rolling conditions that have a great influence on the material properties of the hot rolled steel strip are as follows: heating furnace temperature (heat history of the slab when not passing through the heating furnace), finishing temperature, rolling reduction, cooling rate after rolling. Although there is a winding temperature, efforts have been made so far to obtain predetermined material properties uniformly in the longitudinal direction and the width direction by controlling these conditions.

【０００５】しかし、現行の設備では高歩留りで生産で
きない小ロット品種への対応や最近注目されている熱間
圧延の完全連続化を考えたとき、１回の圧延チャンスで
長手方向に沿って複数の水準の材料特性を有する熱延鋼
帯を製造できれば、生産性や歩留りの向上および在庫の
低減などに多くのメリットが期待される。However, considering a small lot variety that cannot be produced with a high yield by the current equipment and a perfect continuous hot rolling, which has recently attracted attention, it is possible to take a plurality of pieces along the longitudinal direction with one rolling opportunity. If hot-rolled steel strips having the same level of material properties can be manufactured, many advantages are expected in improving productivity, yield, and reducing inventory.

【０００６】[0006]

【発明が解決しようとする課題】しかしながら、このよ
うな技術は未だ開示されていない。However, such a technique has not been disclosed yet.

【０００７】本発明はこのような課題を解決するために
なされたもので、１回の圧延チャンスで長手方向に沿っ
て複数の水準の材料特性を有する熱延鋼帯を製造する方
法を提供することを目的とする。The present invention has been made to solve the above problems, and provides a method for producing a hot-rolled steel strip having a plurality of levels of material properties along the longitudinal direction with one rolling opportunity. The purpose is to

【０００８】[0008]

【課題を解決するための手段】上記課題は、粗圧延後の
粗バーまたは鋼の薄スラブを仕上圧延する工程を有して
なる熱延鋼帯の製造方法において、前記粗圧延後の粗バ
ーまたは鋼の薄スラブを、その温度が長手方向に沿って
２水準以上変わるように加熱または冷却した後に仕上圧
延することを特徴とする熱延鋼帯の製造方法、あるいは
粗圧延後の粗バーまたは鋼の薄スラブを仕上圧延する工
程と仕上圧延後の鋼帯を巻取る工程を有してなる熱延鋼
帯の製造方法において、前記仕上圧延後の鋼帯をその温
度が長手方向に沿って２水準以上変わるように冷却した
後、前記鋼帯の温度の異なる部分を、前記鋼帯の温度の
変り目で切断して異なるコイラーで巻取ることを特徴と
する熱延鋼帯の製造方法により解決される。Means for Solving the Problems The above-mentioned problem is a method for producing a hot-rolled steel strip comprising a step of finish rolling a rough bar after rough rolling or a thin slab of steel, wherein the rough bar after rough rolling is provided. Alternatively, a thin steel slab is heated or cooled so that the temperature thereof changes along the longitudinal direction by two levels or more, and then finish rolling is performed, or a rough bar after rough rolling or In a method for producing a hot-rolled steel strip comprising a step of finish rolling a thin slab of steel and a step of winding a steel strip after finish rolling, the temperature of the steel strip after the finish rolling is along the longitudinal direction. A method for manufacturing a hot-rolled steel strip, characterized in that after cooling so as to change by two levels or more, portions of the steel strip having different temperatures are cut at the temperature transition points of the steel strip and wound by different coilers. To be done.

【０００９】上述したように、熱延鋼帯の材料特性に大
きな影響を及ぼす熱延条件としては、加熱炉温度（加熱
炉を通さない場合は、スラブの熱履歴）、仕上温度、圧
下率、圧延後の冷却速度、巻取温度がある。したがっ
て、１回の圧延チャンスで長手方向に沿って複数の水準
の材料特性を有する熱延鋼帯を製造するには、これらの
条件を仕上圧延前のスラブや粗バーあるいは仕上圧延後
の鋼帯に対して長手方向に変化させればよい。As described above, the hot rolling conditions that have a great influence on the material properties of the hot rolled steel strip are: heating furnace temperature (heat history of the slab when not passing through the heating furnace), finishing temperature, rolling reduction, There are cooling rate and rolling temperature after rolling. Therefore, in order to produce a hot-rolled steel strip having a plurality of levels of material properties along the longitudinal direction in one rolling opportunity, these conditions must be satisfied by the slab or rough bar before finish rolling or the steel strip after finish rolling. However, it may be changed in the longitudinal direction.

【００１０】しかしながら、仕上温度と巻取温度以外の
条件には次のような問題があり、長手方向に沿って複数
の水準の材料特性を有する熱延鋼帯を製造することは実
質的に不可能である。すなわち、加熱炉温度について
は、１０ｍ前後の長さのスラブを加熱炉で温度制御し
て、その長手方向に温度を変えることはできない。ま
た、加熱炉を通さない場合でも、極厚のスラブを短時間
で加熱したり冷却して長手方向に温度を変化させること
は困難である。圧下率については、材料特性ばかりでな
く板厚も変わってしまう。圧延後の冷却速度について
は、低温変態相が生成するような成分系の鋼にしか適用
できなく、しかもランナウトテーブル上で短時間に冷却
速度を厳密に制御することは難しい。However, the conditions other than the finishing temperature and the coiling temperature have the following problems, and it is substantially impossible to manufacture a hot-rolled steel strip having a plurality of levels of material properties along the longitudinal direction. It is possible. That is, regarding the heating furnace temperature, it is impossible to control the temperature of a slab having a length of about 10 m in the heating furnace and change the temperature in the longitudinal direction. Even when the slab is not passed through the heating furnace, it is difficult to heat or cool the extremely thick slab in a short time to change the temperature in the longitudinal direction. Regarding the rolling reduction, not only the material properties but also the plate thickness changes. Regarding the cooling rate after rolling, it can be applied only to the steel of the component system in which the low temperature transformation phase is generated, and it is difficult to strictly control the cooling rate on the runout table in a short time.

【００１１】一方、１回の圧延チャンスで長手方向に仕
上温度を変えることは、粗圧延後の厚さの薄い粗バーま
たは鋼の薄スラブを加熱または冷却したり、圧延速度を
加速または減速することにより容易に行える。しかし、
圧延速度を変化させて仕上温度を変えると温度の遷移領
域が広くなり、したがって特性の遷移領域も広くなって
歩留りの大幅な低下を招くので、厚さの薄い粗バーや薄
スラブを加熱または冷却する方がよい。On the other hand, changing the finishing temperature in the longitudinal direction with one rolling opportunity heats or cools the rough bar or the thin slab of steel having a small thickness after rough rolling, or accelerates or decelerates the rolling speed. This can be done easily. But,
When the rolling speed is changed to change the finishing temperature, the temperature transition region widens, and therefore the characteristic transition region also widens, leading to a large decrease in yield.Therefore, heating or cooling a coarse bar or thin slab with a small thickness is required. It is better to do.

【００１２】また、１回の圧延チャンスで長手方向に巻
取温度を変えることは、仕上圧延後の鋼帯をその温度が
長手方向に沿って２水準以上変わるように冷却すれば行
える。しかし、コイラーに巻取り後は温度が均一化され
て材料特性に差がほとんどなくなってしまう恐れがある
ので、巻取り直前に鋼帯の温度の変り目を切断して異な
るコイラーで巻取る必要がある。なお、仕上圧延すべき
鋼片としては、粗圧延後の粗バーや鋳造ままの薄スラブ
を用いることができる。Further, the winding temperature can be changed in the longitudinal direction with one rolling chance by cooling the steel strip after finish rolling so that the temperature changes by two levels or more along the longitudinal direction. However, since there is a possibility that the temperature will be uniformed after winding on the coiler and there will be almost no difference in material properties, it is necessary to cut the temperature change of the steel strip and wind it with a different coiler immediately before winding. . As the steel piece to be finish-rolled, a rough bar after rough rolling or a thin slab as cast can be used.

【００１３】[0013]

【発明の実施の形態】図１に、本発明の１実施の形態で
ある熱延鋼帯の製造方法を模式的に示す。図で、１は加
熱炉、２は粗圧延機、３は誘導加熱方式の粗バー加熱装
置、４は仕上圧延機、５はランナウト冷却装置、６はコ
イラー、７は放射温度計、８は高速剪断機を表す。DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 schematically shows a method for manufacturing a hot-rolled steel strip, which is an embodiment of the present invention. In the figure, 1 is a heating furnace, 2 is a rough rolling mill, 3 is an induction heating type rough bar heating device, 4 is a finish rolling mill, 5 is a runout cooling device, 6 is a coiler, 7 is a radiation thermometer, and 8 is high speed. Represents a shear.

【００１４】加熱炉１で加熱された長さ１０ｍ程度、厚
さ２５０ｍｍ程度のスラブは、粗圧延機２により長さ８
０ｍ程度、厚さ３０ｍｍ程度の粗バーに圧延され、仕上
圧延機４で所定の板厚まで仕上圧延された後、ランナウ
ト冷却装置５により冷却され、コイラー６で巻取られ
て、熱延鋼帯の製品となる。このとき、仕上圧延機入側
に設けられた誘導加熱方式の粗バー加熱装置３により粗
バーの温度が長手方向に沿って２水準変わるように加熱
すれば、熱延鋼帯の前半分と後半分の仕上温度が変わ
り、１回の圧延チャンスで長手方向に２水準の材料特性
を有する熱延鋼帯を製造することができる。The slab heated by the heating furnace 1 and having a length of about 10 m and a thickness of about 250 mm is made into a length of 8 by the rough rolling mill 2.
After rolling to a rough bar of about 0 m and a thickness of about 30 mm, finish rolling to a predetermined plate thickness by a finish rolling machine 4, cooling by a runout cooling device 5, winding by a coiler 6, and rolling of a hot rolled steel strip. Will be the product of. At this time, if heating is performed so that the temperature of the rough bar changes by two levels along the longitudinal direction by the induction heating type rough bar heating device 3 provided on the entry side of the finishing rolling mill, the first half and the latter half of the hot rolled steel strip. The finishing temperature is changed, and a hot rolled steel strip having two levels of material properties in the longitudinal direction can be manufactured with one rolling opportunity.

【００１５】本発明法で熱間圧延を行うと、粗バーの温
度変更点で仕上圧延時の変形抵抗が大きく変化するため
板厚が変動する恐れがある。しかし、仕上圧延機４の入
側に設けた放射温度計７で温度変更点をトラッキング
し、温度変更点が各スタンドを通過するときロールギャ
ップなどの圧延条件を瞬時に変更することによって板厚
変動のない鋼帯を製造できる。When hot rolling is carried out by the method of the present invention, the deformation resistance during finish rolling greatly changes at the temperature change point of the rough bar, so that the sheet thickness may change. However, the temperature change point is tracked by the radiation thermometer 7 provided on the entrance side of the finishing rolling mill 4, and when the temperature change point passes through each stand, the rolling conditions such as the roll gap are instantaneously changed to change the plate thickness. It is possible to manufacture steel strips without.

【００１６】巻取温度を変えて長手方向に２水準の材料
特性を有する熱延鋼帯を製造するには、前述したように
鋼帯の温度の変り目をコイラー６の直前に設けた高速剪
断機８で切断して異なるコイラー６で巻取ればよい。In order to manufacture a hot-rolled steel strip having two levels of material characteristics in the longitudinal direction by changing the coiling temperature, the high-speed shearing machine having the temperature transition of the steel strip provided immediately before the coiler 6 is used as described above. It may be cut at 8 and wound by a different coiler 6.

【００１７】粗バーあるいは薄スラブを加熱するか冷却
するかは、製造すべき熱延鋼帯の材料特性によって決め
ればよい。Whether to heat or cool the rough bar or the thin slab may be determined by the material characteristics of the hot-rolled steel strip to be manufactured.

【００１８】粗バーあるいは薄スラブの加熱には、誘導
加熱方式の他、制御応答性に優れる通電加熱方式を用い
ることができる。For heating the coarse bar or the thin slab, an induction heating method or an electric heating method having excellent control response can be used.

【００１９】粗バーあるいは薄スラブを冷却は、ガスジ
ェット方式、散水方式、ミスト噴霧方式などの冷却装置
を誘導加熱方式の粗バー加熱装置３の代わりに設置すれ
ば可能である。The rough bar or thin slab can be cooled by installing a cooling device such as a gas jet type, a water sprinkling type or a mist spraying type in place of the induction heating type rough bar heating device 3.

【００２０】[0020]

【実施例】表１に示すＣ量の大きく異なる成分系Ａ、Ｂ
の厚さ２５０ｍｍ、幅１０５０ｍｍ、長さ９２００ｍｍ
のスラブを、図１に模式的に示した熱延鋼帯の製造方法
により表２に示す条件で熱間圧延し、長手方向の前半部
と後半部に２水準の材料特性を有する厚さ１．６ｍｍの
熱延鋼帯を製造した。EXAMPLES Component systems A and B having greatly different amounts of C shown in Table 1
Thickness 250 mm, width 1050 mm, length 9200 mm
1 was hot-rolled under the conditions shown in Table 2 by the method for manufacturing a hot-rolled steel strip schematically shown in FIG. 1 to obtain a thickness 1 having two levels of material properties in the first half and the second half in the longitudinal direction. A hot rolled steel strip of 0.6 mm was produced.

【００２１】試料Ｎｏ．１と２はそれぞれ成分系Ａ、Ｂ
の鋼を用い、仕上圧延機入側に設けられた誘導加熱方式
の粗バー加熱装置により長手方向の前半部と後半部で仕
上温度を変えた本発明法による試料である。Sample No. 1 and 2 are component systems A and B, respectively
Is a sample according to the method of the present invention in which the finishing temperature is changed between the first half and the second half in the longitudinal direction by the induction heating type rough bar heating device provided on the entry side of the finishing rolling mill.

【００２２】試料Ｎｏ．３と４はそれぞれ成分系Ａ、Ｂ
の鋼を用い、試料Ｎｏ．１と２と同様な方法で長手方向
の前半部と後半部で仕上温度を変え、さらにその仕上温
度に対応して巻取温度も変えた本発明法による試料であ
る。なお、巻取温度を変えているため、長手方向の前半
部と後半部は巻取温度の変り目で巻取り直前に切断さ
れ、異なるコイラーに巻取られている。Sample No. 3 and 4 are component systems A and B, respectively
Sample No. A sample according to the method of the present invention in which the finishing temperature was changed in the first half and the second half in the longitudinal direction in the same manner as in 1 and 2, and the winding temperature was also changed corresponding to the finishing temperature. In addition, since the winding temperature is changed, the first half and the second half in the longitudinal direction are cut at the transition of the winding temperature immediately before winding and are wound by different coilers.

【００２３】試料Ｎｏ．５〜１０は、同様なスラブを用
い表２に示した仕上温度、巻取温度でそれぞれ個別に製
造した従来法による試料である。Sample No. Nos. 5 to 10 are samples by the conventional method, which were individually manufactured using the same slab at the finishing temperature and the winding temperature shown in Table 2.

【００２４】そして、長手方向の前半部と後半部に対
し、平均の機械試験値および以下に定義した歩留りを求
めた。Then, an average mechanical test value and a yield defined below were obtained for the first half and the second half in the longitudinal direction.

【００２５】歩留り＝機械試験値の実測値と目標値の差
が目標値の±１０％以内を満足している部分の重量／熱
延鋼帯の全重量 ここで、長手方向の前半部と後半部で仕上温度のみを変
えた試料Ｎｏ．１と２に対しては、巻取り後温度変更点
近傍で切断してから、平均の機械試験値および歩留りを
求めた。Yield = Weight of the portion where the difference between the actually measured value of the mechanical test value and the target value is within ± 10% of the target value / Total weight of the hot-rolled steel strip. Here, the first half and the second half in the longitudinal direction. No. in which only the finishing temperature was changed in the part For 1 and 2, the average mechanical test value and the yield were determined after cutting near the temperature change point after winding.

【００２６】結果を表２に示す。The results are shown in Table 2.

【００２７】本発明法により、それぞれ個別に製造した
場合と同様な機械試験値が得られるのみならず、歩留り
が向上していることがわかる。By the method of the present invention, it is found that not only the mechanical test values similar to the case where they are individually manufactured but also the yield is improved.

【００２８】[0028]

【表１】 [Table 1]

【００２９】[0029]

【表２】 [Table 2]

【００３０】[0030]

【発明の効果】本発明は以上説明したように構成されて
いるので、１回の圧延チャンスで長手方向に沿って複数
の水準の材料特性を有する熱延鋼帯を製造する方法を提
供できる。Since the present invention is configured as described above, it is possible to provide a method for producing a hot-rolled steel strip having a plurality of levels of material properties along the longitudinal direction with one rolling opportunity.

【００３１】したがって、現行の設備では高歩留りで生
産できない小ロット品種や熱間圧延の完全連続化に対応
でき、生産性や歩留りの向上および在庫の低減などに大
きく貢献できる。Therefore, it is possible to cope with small lot varieties that cannot be produced with a high yield in the current equipment and complete continuous hot rolling, and it is possible to greatly contribute to improvement of productivity and yield and reduction of inventory.

【図面の簡単な説明】[Brief description of drawings]

【図１】本発明の１実施の形態である熱延鋼帯の製造方
法の模式図である。FIG. 1 is a schematic diagram of a method for manufacturing a hot-rolled steel strip according to an embodiment of the present invention.

【符号の説明】[Explanation of symbols]

１ 加熱炉 ２ 粗圧延機 ３ 誘導加熱方式の粗バー加熱装置 ４ 仕上圧延機 ５ ランナウト冷却装置 ６ コイラー ７ 放射温度計 ８ 高速剪断機 1 heating furnace 2 rough rolling mill 3 Induction heating type coarse bar heating device 4 Finishing mill 5 Runout cooling system 6 coilers 7 Radiation thermometer 8 high-speed shearing machine

Claims (2)

【特許請求の範囲】[Claims] 【請求項１】 粗圧延後の鋼片または鋼の薄スラブを仕
上圧延する工程を有してなる熱延鋼帯の製造方法におい
て、前記粗圧延後の鋼片または鋼の薄スラブを、その温
度が長手方向に沿って２水準以上変わるように加熱また
は冷却した後に仕上圧延することを特徴とする熱延鋼帯
の製造方法。1. A method for producing a hot-rolled steel strip, comprising a step of finish rolling a steel slab or a thin slab of steel after rough rolling, wherein the steel slab or the thin slab of steel after rough rolling is A method for producing a hot-rolled steel strip, which comprises heating or cooling so that the temperature changes by two levels or more along the longitudinal direction, and then finish rolling. 【請求項２】 粗圧延後の鋼片または鋼の薄スラブを仕
上圧延する工程と仕上圧延後の鋼帯を巻取る工程を有し
てなる熱延鋼帯の製造方法において、前記仕上圧延後の
鋼帯をその温度が長手方向に沿って２水準以上変わるよ
うに冷却した後、前記鋼帯の温度の異なる部分を、前記
鋼帯の温度の変り目で切断して異なるコイラーで巻取る
ことを特徴とする熱延鋼帯の製造方法。2. A method for producing a hot-rolled steel strip, comprising a step of finish rolling a steel slab or a thin slab of steel after rough rolling, and a step of winding a steel strip after finish rolling. After cooling the steel strip in such a manner that the temperature thereof changes by two levels or more along the longitudinal direction, portions of the steel strip having different temperatures are cut at the temperature transitions of the steel strip and wound by different coilers. A method for producing a hot rolled steel strip.