JP2003191005A - Method for cooling hot-rolled steel strip and its production method - Google Patents
Method for cooling hot-rolled steel strip and its production methodInfo
- Publication number
- JP2003191005A JP2003191005A JP2001392504A JP2001392504A JP2003191005A JP 2003191005 A JP2003191005 A JP 2003191005A JP 2001392504 A JP2001392504 A JP 2001392504A JP 2001392504 A JP2001392504 A JP 2001392504A JP 2003191005 A JP2003191005 A JP 2003191005A
- Authority
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- Japan
- Prior art keywords
- cooling
- steel strip
- temperature
- hot
- finish rolling
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- Heat Treatment Of Strip Materials And Filament Materials (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、熱間仕上げ圧延さ
れた高温鋼帯に対する冷却水による熱延鋼帯の冷却方法
および、この冷却方法を用いて熱延鋼帯を製造する製造
方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cooling a hot-rolled steel strip by hot-rolled hot steel strip with cooling water, and a method for producing a hot-rolled steel strip using this cooling method.
【０００２】[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、加熱されたスラブを粗圧延機
で所定厚みに圧延して粗バーとなす。ついで、粗バーを
複数基のスタンドからなる熱間仕上げ圧延機において連
続的に熱間仕上げ圧延し、所定の厚みの鋼帯とする。こ
の熱延鋼帯を、ランナウトテーブル上の冷却装置におい
て冷却した後、コイラーで巻き取ることにより製造され
る。このような鋼帯を、製造ラインで連続的に製造する
場合、熱間仕上げ圧延機を出た直後に鋼帯を水冷すると
冷却ムラが発生し易かった。特に、高速で圧延される鋼
帯においては、幅方向に沿って温度に大きなバラツキが
ある。具体的には、図５にＡ変化として示すように、鋼
帯幅方向の中央部付近の温度が高く、端部が低い温度プ
ロフィルが発生していた。そこで、高温の鋼帯を均一に
冷却して、温度ムラの発生を抑制する手段が数多く提案
されている。たとえば、以下に述べるような技術が開示
されている。2. Description of the Related Art Generally, a hot rolled steel strip is formed by heating a slab to a predetermined temperature in a heating furnace and rolling the heated slab to a predetermined thickness by a rough rolling machine to form a rough bar. Then, the rough bar is continuously hot-finished and rolled in a hot-finishing mill consisting of a plurality of stands to obtain a steel strip having a predetermined thickness. This hot-rolled steel strip is manufactured by cooling it in a cooling device on a runout table and then winding it with a coiler. In the case of continuously producing such a steel strip on a production line, if the steel strip is water-cooled immediately after leaving the hot finish rolling mill, uneven cooling is likely to occur. Particularly, in a steel strip rolled at a high speed, there is a large variation in temperature along the width direction. Specifically, as shown as a change A in FIG. 5, a temperature profile in which the temperature near the central portion in the width direction of the steel strip is high and the end portions are low is generated. Therefore, many means have been proposed for uniformly cooling the high temperature steel strip to suppress the occurrence of temperature unevenness. For example, the following techniques are disclosed.
【０００３】（１） 特開平７−２８４８３６号公報：
圧延後の鋼帯を、表面温度が復熱して６５０℃〜７５０
℃になるまで水冷した後、一旦冷却を停止し、復熱した
後に再び冷却する。（以下、先行技術１と言う。）
（２） 特開平１０−２１１５１５号公報：圧延後の高
温鋼帯を水冷する際に、熱流束が鋼帯の温度に対して正
の勾配を有する冷却条件で冷却する。（以下、先行技術
２と言う）。(1) Japanese Patent Application Laid-Open No. 7-282836:
The surface temperature of the rolled steel strip recovers from 650 ° C to 750 ° C.
After water cooling to ℃, stop cooling, reheat and then cool again. (Hereinafter, referred to as Prior Art 1) (2) Japanese Patent Laid-Open No. 10-21515: Cooling condition in which a heat flux has a positive gradient with respect to the temperature of the steel strip when water-cooling the hot strip after rolling. Cool with. (Hereinafter, referred to as Prior Art 2).
【０００４】（３） 鋼帯の幅方向に沿って温度ムラが
発生しても、そのムラを打ち消すべく、幅方向の冷却能
を可変として、冷却後の幅方向温度を均一にする冷却装
置および制御方法。（以下、先行技術３と言う）(3) Even if temperature unevenness occurs along the width direction of the steel strip, in order to cancel the unevenness, the cooling ability in the width direction is made variable so as to make the temperature in the width direction uniform after cooling. Control method. (Hereinafter, referred to as Prior Art 3)
【０００５】[0005]
【発明が解決しようとする課題】しかしながら、先行技
術１の冷却方法では、冷却開始時の鋼帯温度が９００℃
程度の高温の場合もしくは、板厚が３ｍｍ程度の鋼帯で
は、復熱温度が６５０℃〜７５０℃となるように冷却を
停止させることが難しかった。特に、復熱温度を６５０
℃以上として、変態を起こさない温度で冷却を停止させ
るように温度を規定しているが、実際には、表面温度は
水冷中に変態開始温度より低くなるため、鋼帯表層にお
いて変態が進行しており、途中で冷却を停止すると表層
と内部とで温度履歴が異なってしまう。変態の進行も異
なって、冷却後に板厚方向の組織不均一が生じ、材質が
安定しない。However, in the cooling method of Prior Art 1, the steel strip temperature at the start of cooling is 900 ° C.
It was difficult to stop the cooling so that the recuperation temperature was 650 ° C to 750 ° C in the case of a high temperature of about 3 mm or a steel strip having a plate thickness of about 3 mm. Especially, set the recuperation temperature to 650
Although the temperature is regulated so that the cooling is stopped at a temperature that does not cause transformation above ℃, in reality, since the surface temperature becomes lower than the transformation start temperature during water cooling, transformation progresses in the surface layer of the steel strip. Therefore, if cooling is stopped midway, the temperature history will differ between the surface layer and the inside. The progress of the transformation is also different, and the structure becomes unstable in the plate thickness direction after cooling, and the material is not stable.
【０００６】先行技術２では、鋼帯の表面温度に応じ
て、鋼帯に対する冷却条件を変更する必要がある。しか
しながら、その実施例で示される冷却条件では、鋼帯の
搬送速度は高々６０ｍｐｍまでである。これに対して、
連続的に圧延される熱延鋼帯の製造装置において、鋼帯
の搬送速度は６００ｍｐｍ〜１３００ｍｐｍと、非常に
高速である。このような高速で搬送される高温の熱延鋼
帯において、どのような条件で冷却を行うか、について
の具体的な条件の記載や示唆がない。In the prior art 2, it is necessary to change the cooling conditions for the steel strip depending on the surface temperature of the steel strip. However, under the cooling conditions shown in the example, the conveying speed of the steel strip is up to 60 mpm. On the contrary,
In a continuously rolled hot-rolled steel strip manufacturing apparatus, the steel strip is transported at a very high speed of 600 mpm to 1300 mpm. There is no description or suggestion of specific conditions for cooling under such high temperature hot-rolled steel strip conveyed at high speed.
【０００７】先行技術３では、冷却自体で発生する温度
ムラの発生を防止することはできない。あるいは、一旦
冷却して、その結果、得られた冷却後の温度プロフィル
を検知し、それに応じて冷却能を幅方向に制御しなけれ
ばならない。高速搬送される鋼帯に対する冷却方法で
は、このようなフィードバック制御は制御性が悪く、実
質的に効果がない。In Prior Art 3, it is impossible to prevent the occurrence of temperature unevenness caused by cooling itself. Alternatively, it is necessary to cool once and, as a result, to detect the resulting temperature profile after cooling and control the cooling capacity in the width direction accordingly. In a cooling method for a steel strip conveyed at high speed, such feedback control has poor controllability and is substantially ineffective.
【０００８】一般に、高温の熱延鋼帯を水冷すると、冷
却中の鋼帯の表面温度に応じて、３つの冷却形態、すな
わち、沸騰現象が生じていることが知られている。図３
は、冷却条件を一定にした場合の、鋼帯表面温度と熱流
束の関係を模式的に示した図である。図中のＮ変化は、
静止した鋼帯に対して冷却水の水量密度が３００〜５０
０Ｌ／ｍｉｎｍ２でスプレー冷却した場合の、熱伝達特
性を示したものである。鋼帯温度を高温から徐々に冷や
してくる過程を考えると、４００〜５００℃付近から熱
流束の立ち上がりが観察される。It is generally known that when a hot rolled steel strip at high temperature is water-cooled, three cooling modes, that is, boiling phenomena occur depending on the surface temperature of the steel strip being cooled. Figure 3
FIG. 4 is a diagram schematically showing the relationship between the steel strip surface temperature and the heat flux when the cooling conditions are constant. The change in N in the figure is
The water density of the cooling water is 300 to 50 with respect to the stationary steel strip.
It shows heat transfer characteristics in the case of spray cooling at 0 L / minm 2 . Considering the process of gradually cooling the steel strip temperature from a high temperature, rising of the heat flux is observed from around 400 to 500 ° C.
【０００９】この状態は次のように説明される。高温の
鋼帯を冷却すると、まず、鋼帯表面と冷却水との間に蒸
気膜が存在する膜沸騰状態になる。この膜沸騰状態は、
鋼帯表面温度が非常に高いので、冷却水が鋼帯表面に到
達する前に蒸発して、鋼帯に直接接触することがない沸
騰現象である。鋼帯と冷却水との間には常に蒸気膜が存
在するために、熱流束が小さく、冷却能力は低い。This condition is explained as follows. When the high temperature steel strip is cooled, first, a film boiling state in which a vapor film exists between the steel strip surface and the cooling water is obtained. This film boiling state is
This is a boiling phenomenon in which the cooling water evaporates before reaching the surface of the steel strip and does not come into direct contact with the steel strip because the surface temperature of the steel strip is very high. Since the steam film always exists between the steel strip and the cooling water, the heat flux is small and the cooling capacity is low.
【００１０】鋼帯の表面温度が低下してくると、膜沸騰
状態から遷移沸騰状態へと移行する。遷移沸騰状態に移
行するときの熱流束は、一般に、極小熱流束点と言れて
いる。この遷移沸騰領域では、鋼帯表面を覆っていた蒸
気膜が崩壊して、冷却水と鋼帯表面とが直接接触するよ
うになる。鋼帯は急速に温度低下し、この温度降下にと
もなって、熱流束は急激に増大する。When the surface temperature of the steel strip decreases, the film boiling state transitions to the transition boiling state. The heat flux when transitioning to the transition boiling state is generally said to be the minimum heat flux point. In this transition boiling region, the vapor film covering the surface of the steel strip collapses and the cooling water comes into direct contact with the surface of the steel strip. The temperature of the steel strip decreases rapidly, and the heat flux rapidly increases with this temperature decrease.
【００１１】さらに鋼帯表面温度が低下すると、鋼帯の
表面に蒸気の膜が存在しなくなる。鋼帯表面が冷却水と
全面的に接触し、局所的な発泡点から気泡が発生する状
態、すなわち核沸騰状態に移行する。熱流束は極大点を
過ぎ、かつ鋼帯の温度降下にともなって熱流束は減少す
る。上述したように、沸騰をともなった鋼帯の冷却現象
では、膜沸騰、遷移沸騰、核沸騰の３つの沸騰状態が存
在するのだが、その熱伝達特性は、温度降下にともなっ
て熱流束が減少する膜沸騰および核沸騰と、温度降下に
ともなって熱流束が上昇する遷移沸騰とに区別される。When the surface temperature of the steel strip further decreases, the vapor film does not exist on the surface of the steel strip. The surface of the steel strip comes into full contact with the cooling water, and a state where bubbles are generated from a local foaming point, that is, a state of nucleate boiling shifts. The heat flux passes the maximum point, and the heat flux decreases as the temperature of the steel strip drops. As described above, in the cooling phenomenon of the steel strip accompanied by boiling, there are three boiling states of film boiling, transition boiling, and nucleate boiling, but the heat transfer characteristics are that the heat flux decreases as the temperature drops. A distinction is made between film boiling and nucleate boiling that occur and transitional boiling in which the heat flux rises as the temperature drops.
【００１２】一般に、連続した熱間仕上げ圧延機から出
た熱延鋼帯は、その幅方向両側端部の温度が、幅方向中
央部の温度よりも低くなる。これは、鋼帯が熱間仕上げ
圧延前の粗バー段階（通常、この時点で厚み３０ｍｍ前
後）で圧延待機している（すなわち、自然放冷される）
際に、幅方向両側端部はエッジを有するので、幅方向中
央部に比べて温度の降下が大きいことによる。In general, the temperature of the widthwise end portions of the hot-rolled steel strip discharged from the continuous hot finish rolling mill is lower than the temperature of the widthwise central portion. This is because the steel strip is waiting for rolling at a rough bar stage (usually, at a thickness of around 30 mm at this point) before hot finish rolling (that is, it is naturally cooled).
At this time, since both widthwise end portions have edges, the temperature drop is larger than that in the widthwise central portion.
【００１３】この熱間仕上げ圧延前後の端部温度分布の
推移を図５にＡ変化、Ｂ変化、Ｃ変化として示した。一
般に、熱間仕上げ圧延は、７つの熱間仕上げ圧延機群で
連続的に行われる。加熱炉に近いほうから第１の熱間仕
上げ圧延機、第２の熱間仕上げ圧延機、第３の……の順
に配置され、第７の熱間仕上げ圧延機を最終仕上げ圧延
機と呼ぶ。この熱間仕上げ圧延機の前、中、後の鋼帯の
端部近傍の温度分布の推移が、図５に示すＡ変化と、Ｂ
変化およびＣ変化となる。The transition of the end temperature distribution before and after the hot finish rolling is shown as A change, B change, and C change in FIG. Generally, hot finish rolling is continuously performed by a group of seven hot finish rolling mills. The first hot finish rolling mill, the second hot finish rolling mill, the third ... Are arranged in this order from the one closer to the heating furnace, and the seventh hot finish rolling mill is called a final finishing rolling mill. The transition of the temperature distribution in the vicinity of the end of the steel strip before, after, and after this hot finish rolling mill is shown by A change and B change in FIG.
Change and C change.
【００１４】なお説明すれば、熱間仕上げ圧延直前であ
る第１の熱間仕上げ圧延機に入る直前がＡ変化のような
端部温度分布で、熱間仕上げ圧延中の第３の熱間仕上げ
圧延機と第４の熱間仕上げ圧延機の間では、Ｂ変化のよ
うな端部温度分布となる。両者の温度分布の差は、それ
ぞれΔＴ１、ΔＴ２となり、極くわずかである。これ
は、第３の熱間仕上げ圧延機を出た段階では、鋼帯厚み
は約１０ｍｍと厚く、端部の温度降下が鋼帯中央部の温
度低下に比較して差がないためである。端部で温度が低
下する幅が、端部から粗バーの厚みの２〜５倍程度の幅
であり、粗バーの厚みが３０ｍｍの場合は、端部から６
０〜１５０ｍｍの範囲の温度が、中央部の温度よりも１
０〜４０℃低下した状態になる。Explaining it further, immediately before entering the first hot finish rolling mill, which is just before hot finish rolling, there is an end temperature distribution such as A change, and the third hot finish rolling during hot finish rolling is performed. Between the rolling mill and the fourth hot finish rolling mill, there is an end temperature distribution like B change. The difference between the temperature distributions of both is ΔT1 and ΔT2, respectively, which is extremely small. This is because at the stage of leaving the third hot finish rolling mill, the thickness of the steel strip is as thick as about 10 mm, and the temperature drop at the end portion is not different from the temperature drop at the central portion of the steel strip. The width at which the temperature decreases at the end is about 2 to 5 times the thickness of the coarse bar from the end, and when the thickness of the coarse bar is 30 mm, 6 from the end.
The temperature in the range of 0 to 150 mm is 1 than the temperature of the central part.
The temperature drops by 0 to 40 ° C.
【００１５】最終（第７）熱間仕上げ圧延機を出た直後
の鋼帯の端部温度分布を、Ｃ変化として示す。第３の熱
間仕上げ圧延機以降、第４、第５の熱間仕上げ圧延機を
順次通過するにつれて鋼帯の厚みが薄くなる。その一方
で、鋼帯の温度降下が加速度的に大きくなり、端部近傍
の温度降下がＡ、Ｂ変化に比べて大きくなる。これは、
鋼帯端部からの放熱が鋼帯中央部の放熱よりも大きいた
めであり、かつ温度降下の著しい領域が板厚に依存して
進むためである。鋼帯の端部近傍の温度降下は、端部か
ら板厚の約５倍の領域の温度降下が、幅方向中央部の温
度降下よりも大きくなる。The end temperature distribution of the steel strip immediately after leaving the final (seventh) hot finish rolling mill is shown as C change. After the third hot finish rolling mill, the thickness of the steel strip becomes thinner as it sequentially passes through the fourth and fifth hot finish rolling mills. On the other hand, the temperature drop of the steel strip becomes large at an accelerating rate, and the temperature drop near the end portion becomes larger than the A and B changes. this is,
This is because the heat radiation from the end of the steel strip is larger than that at the central portion of the steel strip, and the region where the temperature drop is remarkable depends on the plate thickness. Regarding the temperature drop in the vicinity of the end of the steel strip, the temperature drop in the region of about 5 times the plate thickness from the end is larger than the temperature drop in the center portion in the width direction.
【００１６】具体的には、端部近傍での温度低下が大き
い部分は、第３〜第４の熱間仕上げ圧延機の間では鋼帯
厚みが１０ｍｍであり、端部影響を受ける領域がエッジ
から５０ｍｍ程度である。また、第４〜第５の熱間仕上
げ圧延機の間では鋼帯厚みが７ｍｍとなり、端部影響を
受ける領域がエッジから３５ｍｍ程度となる。第５〜第
６の熱間仕上げ圧延機の間では鋼帯厚みが５ｍｍとな
り、端部影響を受ける領域がエッジから１５ｍｍ程度と
なる。Specifically, in the portion where the temperature drop is large near the edges, the steel strip thickness is 10 mm between the third and fourth hot finishing mills, and the area affected by the edges is the edge. To about 50 mm. Further, between the fourth to fifth hot finish rolling mills, the steel strip thickness is 7 mm, and the region affected by the end portion is about 35 mm from the edge. Between the fifth to sixth hot finish rolling mills, the thickness of the steel strip is 5 mm, and the region affected by the end portion is about 15 mm from the edge.
【００１７】そして、第６〜第７の熱間仕上げ圧延機の
間では鋼帯の厚みが３．５ｍｍとなり、端部影響を受け
る領域がエッジから１８ｍｍ程度となる。第７の熱間仕
上げ圧延機を通過する間で鋼帯厚みが３ｍｍとなり、端
部影響を受ける領域がエッジから１５ｍｍとなる。第７
の熱間仕上げ圧延機を出たところで端部温度分布を計測
すると、Ｃ変化のようになる。端部での温度降下はＡ，
Ｂ変化に比べて傾きが大きくなるとともに、温度差ΔＴ
３が大きくなる。このように鋼帯厚みが薄くなると、鋼
帯中央部と端部との温度差ΔＴが加速度的に大きくな
る。Between the sixth to seventh hot finishing mills, the thickness of the steel strip is 3.5 mm, and the area affected by the end portion is about 18 mm from the edge. While passing through the seventh hot finish rolling mill, the steel strip has a thickness of 3 mm, and the end-affected region is 15 mm from the edge. 7th
When the end temperature distribution is measured when the hot finish rolling mill is exited, the result is C change. The temperature drop at the end is A,
The slope becomes larger than the B change and the temperature difference ΔT
3 becomes larger. When the thickness of the steel strip is reduced in this way, the temperature difference ΔT between the central portion and the end portion of the steel strip is increased at an accelerated rate.
【００１８】このような幅方向に温度分布を持った鋼帯
を冷却する際の冷却ムラの発生は、次のように説明され
る。前述したように、各沸騰形態の熱伝達特性によっ
て、高温状態すなわち膜沸騰状態で冷却を行うと、冷却
の進行にしたがって熱流束が減少する。したがって、冷
却開始時に温度が高い部分は、温度が低い部分より熱流
束が大きいために速く冷えて、両者の差は縮小する。The occurrence of cooling unevenness when cooling the steel strip having such a temperature distribution in the width direction is explained as follows. As described above, due to the heat transfer characteristics of each boiling mode, when cooling is performed in a high temperature state, that is, a film boiling state, the heat flux decreases as the cooling progresses. Therefore, at the start of cooling, the portion with a high temperature has a larger heat flux than the portion with a low temperature, so that the portion cools faster and the difference between the two is reduced.
【００１９】一方、鋼帯表面温度が遷移沸騰領域の場合
は、表面温度の降下にしたがって熱流束が増加するの
で、冷却開始時に温度が高い部分は、温度が低い部分よ
りも熱流束が小さいために、両者の温度差は拡大する。
また、鋼帯表面温度が核沸騰領域の場合は、膜沸騰領域
で冷却を行った場合と同様、冷却開始時に温度が高い部
分は、温度が低い部分より熱流束が大きいために速く冷
えて、両者の差は縮小する。On the other hand, when the surface temperature of the steel strip is in the transition boiling region, the heat flux increases as the surface temperature decreases, so that the part where the temperature is high at the start of cooling has a smaller heat flux than the part where the temperature is low. In addition, the temperature difference between the two increases.
Further, when the steel strip surface temperature is in the nucleate boiling region, as in the case where cooling is performed in the film boiling region, the part where the temperature is high at the start of cooling is cooled faster because the heat flux is larger than the part where the temperature is low, The difference between the two will shrink.
【００２０】以上説明したように、鋼帯の圧延では、熱
間仕上げ圧延直後の冷却開始時に温度が低い鋼帯端部と
中央部の温度差は、膜沸騰状態と、核沸騰状態では、冷
却の進行にしたがって温度差が縮小する方向に、遷移沸
騰状態では温度差が拡大する方向になる。そこで、本発
明者らは上述現象について種々研究を重ねた結果、熱間
仕上げ圧延後の鋼帯の幅方向の温度ムラを解消するよう
に冷却し、かつ冷却後の幅方向温度を均一にするには、
水量密度が２５００Ｌ／ｍｉｎｍ２以上で冷却して、冷
却開始と同時に、図３中に曲線Ｍで示すように、温度の
降下にしたがって熱流速が減少する伝熱特性の冷却、す
なわち核沸騰状態で冷却すればよく、そのためには、水
量密度２５００Ｌ／ｍｉｎｍ２以上で冷却すればよいこ
とを知見した。As described above, in the rolling of the steel strip, the temperature difference between the end portion and the central portion of the steel strip, which has a low temperature at the start of cooling immediately after the hot finish rolling, is the difference between the film boiling state and the nucleate boiling state. In the transition boiling state, the temperature difference decreases in the direction of decreasing the temperature difference. Therefore, as a result of various studies on the above phenomenon, the present inventors have cooled the steel strip after hot finish rolling so as to eliminate temperature unevenness in the width direction and make the temperature in the width direction uniform after cooling. Has
Cooling is performed at a water amount density of 2500 L / min 2 or more, and at the same time as the start of cooling, as shown by a curve M in FIG. It has been found that cooling can be performed, and for that purpose, cooling can be performed at a water amount density of 2500 L / min 2 or more.
【００２１】また、図５のＢ変化からＣ変化のように、
板厚が薄い段階では、鋼帯端部の温度降下が、鋼帯中央
部の温度降下と比較して大きいので、時間の経過につれ
て両者の温度差が拡大する傾向にある。そこで、水量密
度２５００Ｌ／ｍｉｎｍ２以上で端部の温度を救える限
界を精査した結果、最終仕上げ圧延後２秒以内に、この
冷却条件で冷却を開始すれば中央部と端部の温度差ΔＴ
が４０℃を越えるようなことがなく、冷却を終了できる
ことが判明した。しかしながら、最終仕上げ圧延後２秒
以上経過したのちに、上記冷却条件で冷却しても、中央
部と端部の温度差が既についてしまっているので、中央
部と端部で温度差ΔＴを４０℃以内に抑えることは困難
であった。Further, from the change B to the change C in FIG.
In the stage where the plate thickness is thin, the temperature drop at the end of the steel strip is larger than the temperature drop at the center of the steel strip, so the temperature difference between the two tends to increase over time. Therefore, as a result of carefully examining the limit that can save the temperature of the end portion with the water amount density of 2500 L / minm 2 or more, if the cooling is started under this cooling condition within 2 seconds after the final finish rolling, the temperature difference ΔT between the central portion and the end portion
It was found that the cooling can be completed without exceeding 40 ° C. However, even after cooling for 2 seconds or more after the final finish rolling, the temperature difference between the central portion and the end portion is already kept even if the cooling is performed under the above cooling conditions, so the temperature difference ΔT between the central portion and the end portion is 40. It was difficult to keep it within ℃.
【００２２】本発明は、上記事情に着目してなされたも
のであり、その目的とするところは、高速で搬送される
ランナウト上で鋼帯を連続して、かつ鋼帯の幅方向に亘
って均一な温度に冷却して、幅方向に均質な鋼帯を連続
的に製造するための熱延鋼帯の冷却方法およびその製造
方法を提供しようとするものである。The present invention has been made in view of the above circumstances, and its object is to continuously run a steel strip on a runout which is conveyed at a high speed and to extend across the width of the strip. An object of the present invention is to provide a method for cooling a hot-rolled steel strip and a method for producing the same for continuously producing a steel strip that is homogeneous in the width direction by cooling to a uniform temperature.
【００２３】[0023]
【課題を解決するための手段】本発明は、上記知見に基
づいてなされたものであり、第１の手段として、熱間仕
上げ圧延後の冷却水による鋼帯の冷却方法であって、冷
却水の水量密度を２５００Ｌ／ｍｉｎｍ２以上に設定し
て冷却する。第２の手段として、上記冷却水の水量密度
を２５００Ｌ／ｍｉｎｍ２以上に設定した冷却は、熱間
仕上げ圧延後２秒未満の間に開始する。The present invention has been made based on the above findings. As a first means, there is provided a method for cooling a steel strip with cooling water after hot finish rolling, comprising: The water amount density is set to 2500 L / minm 2 or more and cooled. As a second means, cooling in which the water density of the cooling water is set to 2500 L / minm 2 or more is started within less than 2 seconds after hot finish rolling.
【００２４】第３の手段として、熱延鋼帯の製造方法
は、スラブを加熱する加熱工程と、上記加熱工程にて加
熱されたスラブを粗圧延して粗バーとなす粗圧延工程
と、上記粗圧延工程にて粗圧延された粗バーを仕上げ圧
延する仕上げ圧延工程と、上記仕上げ圧延工程で仕上げ
圧延された鋼帯を、請求項１および請求項２のいずれか
の冷却方法によって冷却する冷却工程と、上記冷却工程
で冷却された鋼帯を巻き取る巻き取り工程とを具備し
た。第４の手段として、上記粗圧延工程と上記仕上げ圧
延工程との間に、粗バーを加熱する加熱工程を有する。As a third means, a method of manufacturing a hot-rolled steel strip comprises a heating step of heating a slab, a rough rolling step of roughly rolling the slab heated in the heating step to form a rough bar, A finish rolling step of finish rolling a rough bar roughly rolled in the rough rolling step, and a cooling for cooling the steel strip finish rolled in the finish rolling step by the cooling method according to any one of claims 1 and 2. The method includes a step and a winding step of winding the steel strip cooled in the cooling step. As a fourth means, there is a heating step of heating the rough bar between the rough rolling step and the finish rolling step.
【００２５】本発明の冷却工程における熱伝達特性を、
図３にＭ変化として示す。鋼帯の搬送速度が６００ｍｐ
ｍ以上の高速であっても、仕上げ圧延後の鋼帯の冷却
（通常、９００℃以下から冷却）は、冷却の進行にした
がって鋼帯の表面温度が低下する。図３にＮ変化として
示す、従来の水量密度３００〜５００Ｌ／ｍｉｎｍ２の
スプレー冷却と比較すると、本発明（Ｍ変化）では熱流
束が単純に減少する熱伝導特性となる。そのため、冷却
開始時に温度の高い部分は、温度が低い部分より熱流束
が大きいため早く冷えて、両者の差が縮小する冷却を実
現できる。The heat transfer characteristics in the cooling process of the present invention are
This is shown as M change in FIG. Steel strip transfer speed is 600mp
Even at a high speed of m or more, when cooling the steel strip after finish rolling (usually cooling from 900 ° C. or lower), the surface temperature of the steel strip decreases as the cooling progresses. Compared with the conventional spray cooling of water amount density of 300 to 500 L / min 2 shown as N change in FIG. 3, in the present invention (M change), the heat flux has a heat conduction characteristic in which the heat flux simply decreases. Therefore, at the start of cooling, the portion having a higher temperature has a larger heat flux than the portion having a lower temperature, so that the portion cools faster, and the cooling in which the difference between the two is reduced can be realized.
【００２６】この効果を、図４に示す。同図は、冷却前
の鋼帯中央部と端部との温度差ΔＴｂと、冷却後の鋼帯
中央部と端部の温度差ΔＴａとの差（ΔＴｂ−ΔＴａ）
と、水量密度の関係を示したものである。ここで、水量
密度が２０００Ｌ／ｍｉｎｍ２以下では、ΔＴｂ−ΔＴ
ａ＜０となり、冷却後に温度差が拡大しているのに対
し、水量密度が２５００Ｌ／ｍｉｎｍ２以上では、ΔＴ
ｂ−ΔＴａ＞０となって、冷却後に温度差が縮小するこ
とが分かる。This effect is shown in FIG. The figure shows the difference (ΔTb-ΔTa) between the temperature difference ΔTb between the center and the end of the steel strip before cooling and the temperature difference ΔTa between the center and the end of the steel strip after cooling.
And the water density. Here, when the water density is 2000 L / minm 2 or less, ΔTb−ΔT
While a <0, and the temperature difference widens after cooling, when the water density is 2500 L / min 2 or more, ΔT
It can be seen that b-ΔTa> 0 and the temperature difference decreases after cooling.
【００２７】このような冷却方法により、圧延後の鋼帯
の幅方向温度偏差を極力なくすことが可能となる。冷却
終了時の幅方向の温度差、特に、両側端部と中央部との
温度差は少なくなる傾向にあり、結果として冷却停止温
度の均一性が向上する。この効果を最大限に引き出すた
めに、粗圧延段階で発生した両側端部の温度降下を補償
する加熱手段を備えることとする。たとえば誘導加熱に
よって、粗バーの鋼帯端部を連続的に加熱する方法や、
両側部近傍に備えたバーナーで端部を加熱することによ
り、さらなる効果が期待される。With such a cooling method, it is possible to minimize the temperature deviation in the width direction of the rolled steel strip. The temperature difference in the width direction at the end of cooling tends to be small, especially the temperature difference between both side end portions and the central portion, and as a result, the uniformity of the cooling stop temperature is improved. In order to maximize this effect, a heating means for compensating for the temperature drop at both end portions generated in the rough rolling stage is provided. For example, a method of continuously heating the steel strip end of the rough bar by induction heating,
Further effects can be expected by heating the ends with burners provided near both sides.
【００２８】また、鋼帯の長手方向全長に亘って温度差
を少なくするためには、粗バー段階から仕上げ圧延に入
る際の待機時間中に発生する、自然放冷分を鋼帯長手方
向に亘って補償する手段を備える。たとえば、誘導加熱
のような粗バーの断面温度を上昇させる手段を設けて、
仕上げ圧延に入る粗バーの平均温度が常に一定になるよ
うな加熱制御を行う。これにより、さらなる温度の均一
化が得られ、特に、鋼帯の長手方向全長に亘る温度の均
一化が得られる。結果として、仕上げ圧延終了時に不可
避的に存在する温度差を、少なくとも冷却開始前と同程
度か、より少なくすることが可能となり、コイル内の温
度の均一性が向上して、コイル全体の材質の均質性が向
上する。Further, in order to reduce the temperature difference over the entire length in the longitudinal direction of the steel strip, the naturally-cooled component generated during the waiting time at the time of entering the finish rolling from the rough bar stage is set in the longitudinal direction of the strip. A means for compensating is provided. For example, by providing a means for increasing the cross-section temperature of the coarse bar, such as induction heating,
The heating control is performed so that the average temperature of the rough bar entering the finish rolling is always constant. This makes it possible to further homogenize the temperature, and in particular, to homogenize the temperature over the entire length in the longitudinal direction of the steel strip. As a result, the temperature difference that exists inevitably at the end of finish rolling can be at least equal to or less than that before the start of cooling, and the uniformity of temperature inside the coil is improved, and Improves homogeneity.
【００２９】[0029]
【発明の実施の形態】次に、本発明の実施の形態を詳述
する。
［第１の実施の形態］図１に、熱延鋼帯の製造設備にお
ける構成配置を概略に示す。粗圧延機１で圧延された粗
バー２は複数の搬送テーブル上を搬送され、７つの熱間
仕上げ圧延機３で連続的に所定の厚みまで圧延される。
さらに、ランナウトテーブル４へ送られたあと、後方に
配置される巻取り機５で巻取られて熱延鋼帯（熱延コイ
ルとも言う）となる。BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described in detail. [First Embodiment] FIG. 1 schematically shows a structural arrangement in a hot-rolled steel strip manufacturing facility. The rough bar 2 rolled by the rough rolling mill 1 is transported on a plurality of transport tables and continuously rolled by the seven hot finish rolling mills 3 to a predetermined thickness.
Further, after being sent to the runout table 4, it is wound by a winder 5 arranged at the rear to form a hot rolled steel strip (also called a hot rolled coil).
【００３０】上記ランナウトテーブル４において、最終
熱間仕上げ圧延機３Ｚの直後位置に、後述する冷却装置
６が設置される。上記冷却装置６は、最終熱間仕上げ圧
延機３Ｚから５ｍ離間した位置から設置される、全長２
０ｍの装置である。このような熱延鋼帯の製造設備であ
って、熱延鋼帯の製造方法として、スラブを加熱する加
熱工程と、上記加熱工程にて加熱されたスラブを粗圧延
機１で粗圧延して粗バー２となす粗圧延工程と、上記粗
圧延工程にて粗圧延された粗バー２を熱間仕上げ圧延機
３で熱間仕上げ圧延する熱間仕上げ圧延工程と、上記熱
間仕上げ圧延工程で熱間仕上げ圧延された鋼帯を冷却装
置６で冷却する冷却工程と、上記冷却工程で冷却された
鋼帯を巻取り機５で巻取る巻取り工程とを具備してい
る。On the runout table 4, a cooling device 6 to be described later is installed immediately after the final hot finish rolling mill 3Z. The cooling device 6 is installed from a position 5 m away from the final hot finish rolling mill 3Z and has a total length of 2
It is a device of 0 m. In such a hot-rolled steel strip manufacturing facility, as a method for manufacturing a hot-rolled steel strip, a heating step of heating a slab and a slab heated in the heating step are roughly rolled by a rough rolling machine 1. A rough rolling step for forming a rough bar 2, a hot finish rolling step for hot finish rolling the rough bar 2 rough-rolled in the rough rolling step by a hot finish rolling mill 3, and a hot finish rolling step. It comprises a cooling step of cooling the hot-finished steel strip with a cooling device 6 and a winding step of winding the steel strip cooled in the cooling step with a winding machine 5.
【００３１】以下、冷却装置６について詳述する。搬送
される鋼帯の上方部位である冷却装置６の上面側には、
互いに近接して複数の円管ラミナーノズル７が配置さ
れ、図示しないガイドの上方から鋼帯に向けて冷却水を
散水するようになっている。一方、搬送される鋼帯の下
方部位である冷却装置６の下面側には、搬送テーブルａ
間に、複数のスプレーノズル８が設けられている。これ
らスプレーノズル８は、搬送される鋼帯の幅方向に沿っ
て１００ｍｍピッチで、かつ長手方向に搬送テーブルａ
と同じ３００ｍｍピッチで設置されていて、長手方向に
沿う各ノズルは列毎にＯＮ−ＯＦＦ制御が可能である。The cooling device 6 will be described in detail below. On the upper surface side of the cooling device 6, which is the upper portion of the steel strip to be transported,
A plurality of circular tube laminar nozzles 7 are arranged in close proximity to each other and spray cooling water from above a guide (not shown) toward the steel strip. On the other hand, on the lower surface side of the cooling device 6 which is a lower portion of the steel strip to be transported, the transport table a
A plurality of spray nozzles 8 are provided between them. These spray nozzles 8 have a pitch of 100 mm along the width direction of the steel strip to be conveyed, and the conveyance table a in the longitudinal direction.
The nozzles are arranged at the same 300 mm pitch as the above and each nozzle along the longitudinal direction can be ON-OFF controlled for each row.
【００３２】なお、冷却装置６から噴射された冷却水が
鋼帯上を流れて冷却装置の前後に流出し、局所的に鋼帯
が過冷却を起すことが考えられ、幅方向における温度ム
ラの発生になってしまう。これを防止するため、冷却装
置入側と出側に、鋼帯上の冷却水を幅方向側端部へ吹き
飛ばす水切りパージノズル９が設けられている。ここ
で、冷却水の水量密度は、第１の実施の形態では２５０
０Ｌ／ｍｉｎｍ２としているが、実質的には２５００Ｌ
／ｍｉｎｍ２以上であれば、図３に曲線Ｍで示すような
熱伝達特性を示し、温度の降下にしたがって熱流速が単
調に減少する冷却を行うことが可能である。It is conceivable that the cooling water injected from the cooling device 6 flows over the steel strip and flows out before and after the cooling device to locally supercool the steel strip. It will occur. In order to prevent this, drainage purge nozzles 9 are provided on the inlet side and outlet side of the cooling device to blow off the cooling water on the steel strip to the end portion on the width direction side. Here, the water quantity density of the cooling water is 250 in the first embodiment.
Although it is set to 0 L / min 2 , it is substantially 2500 L.
If it is / minm 2 or more, the heat transfer characteristic as shown by the curve M in FIG. 3 is exhibited, and it is possible to perform the cooling in which the heat flow rate monotonously decreases as the temperature decreases.
【００３３】すなわち、水量密度が高い場合には、実質
的に冷却開始直後から核沸騰領域での冷却となる。本実
施例の場合は、核沸騰領域が９００℃であるが、水量密
度を２５００Ｌ／ｍｉｎｍ２以上に設定すれば、鋼帯表
面温度が高くても、表面温度の降下にしたがって熱流束
が減少する。いわゆる、核沸騰状態で冷却が進行するの
で、冷却開始時に鋼帯内に温度のムラが存在しても、冷
却中に温度が高い部分は、温度が低い部分よりも熱流束
が小さいために、両者の温度差は冷却終了時には縮小す
る。That is, when the water amount density is high, cooling is performed in the nucleate boiling region substantially immediately after the start of cooling. In the case of the present embodiment, the nucleate boiling region is 900 ° C., but if the water amount density is set to 2500 L / min 2 or more, the heat flux decreases as the surface temperature drops even if the steel strip surface temperature is high. . Since the cooling progresses in the so-called nucleate boiling state, even if there is temperature unevenness in the steel strip at the start of cooling, the high temperature portion during cooling has a smaller heat flux than the low temperature portion, The temperature difference between the two decreases at the end of cooling.
【００３４】なお、鋼帯の幅方向の温度分布は、仕上げ
圧延機３の後側に設けられる冷却前温度計１０と、冷却
装置６の出側に設けられる冷却後温度計１１によって計
測した。この冷却装置６に、熱間仕上げ圧延直後の厚み
２．３ｍｍの炭素鋼の鋼帯を、搬送速度６００〜１３０
０ｍｐｍで通過させて冷却を施した。鋼帯の先端が巻取
り機５に巻取られるまでの無拘束（無張力）の状態で
は、搬送速度６００ｍｐｍで冷却装置６を通過させ、先
端が巻取り機５に巻取られたあとは１３００ｍｐｍまで
加速する。なお、仕上げ圧延直後の鋼帯温度は、幅方向
の温度が８８０〜９１０℃、幅方向の温度差が３０℃で
ある。The temperature distribution in the width direction of the steel strip was measured by a pre-cooling thermometer 10 provided on the rear side of the finish rolling mill 3 and a post-cooling thermometer 11 provided on the outlet side of the cooling device 6. A steel strip of carbon steel having a thickness of 2.3 mm immediately after the hot finish rolling was transferred to the cooling device 6 at a transfer speed of 600 to 130.
Cooling was done by passing at 0 mpm. In the unconstrained state (no tension) until the tip of the steel strip is wound up by the winder 5, the steel strip is passed through the cooling device 6 at a conveyance speed of 600 mpm, and after the tip is wound up by the winder 5, 1300 mpm. Accelerate to. The temperature of the steel strip immediately after finish rolling is 880 to 910 ° C in the width direction and 30 ° C in the width direction.
【００３５】つぎに、この冷却装置６による冷却制御
は、搬送速度の増速に応じて、冷却水を噴射するノズル
の数を増加することで対応する。この場合、冷却水を噴
射するノズルの列を搬送方向の下流側に向かって順に増
加する。２５００Ｌ／ｍｉｎｍ２のような高水量密度で
の冷却では、水量を変えても冷却能力（熱伝達特性）は
変わらない。すなわち、水量密度を増やしても冷却能力
は飽和していて冷却能力はほとんど変化しない。Next, the cooling control by the cooling device 6 is dealt with by increasing the number of nozzles for injecting the cooling water in accordance with the increase in the conveying speed. In this case, the row of nozzles that eject the cooling water is sequentially increased toward the downstream side in the transport direction. In cooling at a high water density such as 2500 L / minm 2, the cooling capacity (heat transfer characteristic) does not change even if the water quantity is changed. That is, even if the water density is increased, the cooling capacity is saturated and the cooling capacity hardly changes.
【００３６】したがって、増速にともなって冷却能力を
増加させる手段として、冷却水を噴射するノズルの数を
増やし、かつ冷却ゾーン長を長くすることで対応するの
が効果的である。以上の冷却設備・冷却条件で、熱間仕
上げ圧延直後の鋼帯幅方向の温度分布は８８０℃〜９１
０℃であったものが、冷却後では７００℃〜７２０℃と
なって、最大値と最小値の差が３０℃から２０℃へと縮
小した。その結果、鋼帯幅方向の引張り強度のばらつき
は３０ＭＰａから２０ＭＰａへ均一化した。Therefore, it is effective to increase the number of nozzles for injecting cooling water and increase the length of the cooling zone as a means for increasing the cooling capacity as the speed increases. Under the above cooling equipment and cooling conditions, the temperature distribution in the steel strip width direction immediately after hot finish rolling is 880 ° C to 91 ° C.
After the temperature was 0 ° C, it became 700 ° C to 720 ° C after cooling, and the difference between the maximum value and the minimum value was reduced from 30 ° C to 20 ° C. As a result, the variation in tensile strength in the width direction of the steel strip was made uniform from 30 MPa to 20 MPa.
【００３７】なお、冷却開始のタイミング（時間）は、
仕上げ圧延終了直後の方が、本発明における冷却方法に
よる鋼帯幅方向の均質化の効果を最大限に発揮できる。
すなわち、仕上げ圧延直後から端部は中央部に比べて、
エッジ効果のため温度降下が速い。したがって、圧延後
の時間経過にともなって鋼帯端部と鋼帯中央部の温度差
が拡大していく。この第１の実施の形態では、熱間仕上
げ圧延後約１秒で冷却を開始している。これを２秒とす
ると、本実施の形態の条件では冷却後の幅方向温度分布
の最大値と最小値の差が圧延直後のそれと比べて縮小し
ない。本発明の効果を得るためには、仕上げ圧延後２秒
未満、望ましくは１秒以内に冷却開始することが望まし
い。The timing (time) of cooling start is
Immediately after finishing rolling, the effect of homogenizing in the width direction of the steel strip by the cooling method of the present invention can be maximized.
That is, immediately after the finish rolling, the end portion is
The temperature drop is fast due to the edge effect. Therefore, the temperature difference between the steel strip edge portion and the steel strip central portion increases with the lapse of time after rolling. In the first embodiment, cooling is started about 1 second after hot finish rolling. If this is set to 2 seconds, under the conditions of the present embodiment, the difference between the maximum value and the minimum value of the widthwise temperature distribution after cooling is not reduced as compared with that immediately after rolling. In order to obtain the effect of the present invention, it is desirable to start cooling within less than 2 seconds, preferably within 1 second after finish rolling.
【００３８】［第２の実施の形態］図２に、熱延鋼帯の
製造設備における配置を概略に示す。先に図１で説明し
た設備と同一設備については、同番号を付して、ここで
は新たな説明を省略する。この第２の実施の形態では、
仕上げ圧延前の粗バー２に対して、粗バー２の全体を誘
導加熱するバーヒータ１２と、粗バー２のエッジを誘導
加熱するエッジヒータ１３を設置したことに特徴があ
る。[Second Embodiment] FIG. 2 schematically shows the arrangement of a hot-rolled steel strip in a manufacturing facility. The same equipment as the equipment described above with reference to FIG. 1 is denoted by the same reference numeral, and a new description is omitted here. In this second embodiment,
It is characterized in that a bar heater 12 that induction-heats the entire rough bar 2 and an edge heater 13 that induction-heats the edge of the rough bar 2 are provided for the rough bar 2 before finish rolling.
【００３９】すなわち、上述した熱延鋼帯の製造方法に
おいて、上記粗圧延工程と上記仕上げ圧延工程との間
に、粗バーを加熱する加熱工程を有している。なお説明
すれば、仕上げ圧延機３の前には粗バー２全体の温度を
上げるバーヒータ１２が配置されていて、たとえ粗バー
に局所的な温度変動があっても、または、たとえ圧延速
度が変わっても、仕上げ圧延機３に導かれる粗バー２の
長手方向の温度が予め定めた温度となるように温度制御
を行っている。That is, the above-described method for manufacturing a hot-rolled steel strip has a heating step of heating the rough bar between the rough rolling step and the finish rolling step. It should be noted that a bar heater 12 that raises the temperature of the entire rough bar 2 is arranged in front of the finish rolling mill 3, and even if there is a local temperature fluctuation in the rough bar or even if the rolling speed changes. Even so, the temperature control is performed so that the temperature in the longitudinal direction of the rough bar 2 guided to the finish rolling mill 3 becomes a predetermined temperature.
【００４０】なお、予め定めた温度とは、仕上げ圧延機
入側における粗バーの温度が、その長手方向に亘って一
定とする温度であったり、仕上げ圧延機出側温度が目標
仕上げ温度以上となるように設定した仕上げ圧延機入側
の温度であったりする。そのため、制御方式により、仕
上げ圧延機入り側の温度、出側の温度、その他の場所で
の温度を種々選択し、予め目標温度を定めて温度制御を
行うこととなる。さらに、このバーヒータ１２に隣接す
る仕上げ圧延機３側には、エッジヒータ１３が配置され
ていて、粗バー２の両側端部を局所的に誘導加熱するよ
うになっている。The predetermined temperature means that the temperature of the rough bar on the entrance side of the finishing rolling mill is constant over the longitudinal direction, or the temperature on the exit side of the finishing rolling mill is equal to or higher than the target finishing temperature. It may be the temperature at the entry side of the finishing mill that is set so that Therefore, the temperature of the entrance side of the finish rolling mill, the temperature of the exit side, and the temperature at other places are variously selected according to the control method, and the target temperature is set in advance to perform the temperature control. Further, an edge heater 13 is arranged on the side of the finish rolling mill 3 adjacent to the bar heater 12 so that both end portions of the rough bar 2 are locally induction-heated.
【００４１】このエッジヒータ１３により、バーヒータ
１２では制御が不十分な粗バー２の幅方向の温度分布の
制御を行っている。粗バー２の幅方向には、スラブから
粗バー２に圧延される段階で粗バー端部に温度降下が生
じている。エッジヒータ１３は、この粗バー２の幅方向
の温度補償を行うものである。ここで、冷却水の水量密
度は、本実施の形態例では２５００Ｌ／ｍｉｎｍ２とし
ているが、実質的には２５００Ｌ／ｍｉｎｍ２以上であ
れば、図３の曲線Ｍで示すような熱伝達特性を示し、温
度の降下にしたがって熱流束が単調に減少する冷却を行
うことが可能である。The edge heater 13 controls the temperature distribution in the width direction of the coarse bar 2 which is not sufficiently controlled by the bar heater 12. In the width direction of the rough bar 2, a temperature drop occurs at the end of the rough bar when the slab is rolled into the rough bar 2. The edge heater 13 performs temperature compensation in the width direction of the rough bar 2. Here, the water density of the cooling water is 2500 L / minm 2 in the present embodiment, but if it is substantially 2500 L / min 2 or more, the heat transfer characteristic as shown by the curve M in FIG. 3 is obtained. It is possible to provide cooling in which the heat flux monotonically decreases with decreasing temperature.
【００４２】すなわち、水量密度が高い場合には、実質
的に冷却開始直後から核沸騰領域での冷却となる。本実
施の形態の場合は、核沸騰領域が９００℃であるが、水
量密度を２５００Ｌ／ｍｉｎｍ２以上に設定すれば、鋼
帯表面温度が高くても、表面温度の降下にしたがって熱
流束が減少する。いわゆる、核沸騰状態で冷却が進行す
るので、冷却開始時に鋼帯内に温度ムラが存在しても、
冷却中に温度が高い部分は、温度が低い部分よりも熱流
束が小さいために、両者の温度差は冷却終了時には縮小
する。That is, when the water amount density is high, cooling is performed in the nucleate boiling region substantially immediately after the start of cooling. In the case of the present embodiment, the nucleate boiling region is 900 ° C., but if the water amount density is set to 2500 L / minm 2 or more, even if the steel strip surface temperature is high, the heat flux decreases as the surface temperature decreases. To do. Since the cooling progresses in the so-called nucleate boiling state, even if there is temperature unevenness in the steel strip at the start of cooling,
Since the heat flux in the high temperature portion during cooling is smaller than that in the low temperature portion, the temperature difference between the two decreases at the end of cooling.
【００４３】この冷却装置６に、熱間仕上げ圧延直後の
厚み２．３ｍｍの炭素鋼の鋼帯を、搬送速度６００〜１
３００ｍｐｍで通過させて冷却を施した。鋼帯先端が巻
取り機５に巻取られるまでの無拘束（無張力）の状態で
は、搬送速度６００ｍｐｍで冷却装置６を通過させ、先
端が巻取り機５に巻取られたあとは１３００ｍｐｍまで
加速する。なお、仕上げ圧延直後の鋼帯温度は、バーヒ
ータ１２とエッジヒータ１３を使ったことにより均一化
し、幅方向の温度が８８０〜９１０℃、幅方向の温度差
が２０℃である。In this cooling device 6, a steel strip of carbon steel having a thickness of 2.3 mm immediately after hot finish rolling was conveyed at a transfer speed of 600 to 1
Cooling was done by passing through at 300 mpm. In the unconstrained state (no tension) until the tip of the steel strip is wound up by the winder 5, the cooling device 6 is passed at a conveying speed of 600 mpm, and up to 1300 mpm after the tip is wound up by the winder 5. To accelerate. The temperature of the steel strip immediately after finish rolling is made uniform by using the bar heater 12 and the edge heater 13, and the temperature in the width direction is 880 to 910 ° C and the temperature difference in the width direction is 20 ° C.
【００４４】つぎに、この冷却装置６による冷却制御
は、搬送速度の増速に応じて、冷却水を噴射するノズル
の数を増加することで対応する。この場合、冷却水を噴
射するノズルの列を搬送方向の下流側に向かって順に増
加する。２５００Ｌ／ｍｉｎｍ２のような高水量密度で
の冷却では、水量を変えても冷却能力（熱伝達特性）は
変わらない。すなわち、水量密度を増やしても冷却能力
は飽和していて冷却能力はほとんど変化しない。Next, the cooling control by the cooling device 6 is dealt with by increasing the number of nozzles for injecting the cooling water in accordance with the increase in the transport speed. In this case, the row of nozzles that eject the cooling water is sequentially increased toward the downstream side in the transport direction. In cooling at a high water density such as 2500 L / minm 2, the cooling capacity (heat transfer characteristic) does not change even if the water quantity is changed. That is, even if the water density is increased, the cooling capacity is saturated and the cooling capacity hardly changes.
【００４５】したがって、増速にともなって冷却能力を
増加させる手段として、冷却水を噴射するノズルの数を
増やし、かつ冷却ゾーン長を長くすることで対応するの
が効果的である。以上の冷却設備・冷却条件で、仕上げ
圧延直後の鋼帯幅方向の温度分布は、８９０℃〜９１０
℃であったものが、冷却後では７００℃〜７１５℃とな
って、最大値と最小値の差が２０℃から１５℃へと縮小
した。さらに、鋼帯の長手方向についても、その温度バ
ラツキが１５℃程度となったことで、コイル全体の引張
り強度のばらつきは２０ＭＰａから１５ＭＰａへ均質化
した。Therefore, it is effective to increase the number of nozzles for injecting cooling water and increase the length of the cooling zone as a means for increasing the cooling capacity with increasing speed. With the above cooling equipment and cooling conditions, the temperature distribution in the steel strip width direction immediately after finish rolling is 890 ° C to 910 ° C.
What was ℃ was 700 ℃ -715 ℃ after cooling, the difference between the maximum value and the minimum value was reduced from 20 ℃ to 15 ℃. Further, in the longitudinal direction of the steel strip as well, the temperature variation became about 15 ° C., so that the variation in the tensile strength of the entire coil was homogenized from 20 MPa to 15 MPa.
【００４６】［比較例］比較例として、第１の実施の形
態で説明した冷却装置を用いて、以下の条件で鋼帯の冷
却を行い、冷却後の鋼帯の幅方向の温度均一性を比較し
た。
（比較例１）熱間仕上げ圧延終了後の熱延鋼帯の上面と
下面を、それぞれ冷却水の水量密度が５００Ｌ／ｍｉｎ
ｍ２に設定したスプレー冷却を行う。[Comparative Example] As a comparative example, the cooling apparatus described in the first embodiment was used to cool the steel strip under the following conditions, and the temperature uniformity in the width direction of the steel strip after cooling was measured. Compared. (Comparative Example 1) The water density of the cooling water was 500 L / min on the upper surface and the lower surface of the hot-rolled steel strip after the hot finish rolling.
Perform spray cooling set to m 2 .
【００４７】（比較例２）熱間仕上げ圧延終了後の熱延
鋼帯の上面と下面を、それぞれ冷却水の水量密度が２０
００Ｌ／ｍｉｎｍ２に設定したスプレー冷却を行う。
（比較例３）熱間仕上げ圧延終了４秒後の熱延鋼帯の上
面と下面を、それぞれの冷却水の水量密度が２５００Ｌ
／ｍｉｎｍ２に設定したスプレー冷却を行う。なお、比
較例における被冷却材と、これに対する冷却条件は、第
１の実施の形態と同じである。(Comparative Example 2) The upper and lower surfaces of the hot-rolled steel strip after completion of the hot finish rolling had a cooling water volume density of 20 respectively.
Spray cooling is set to 00 L / minm 2 . (Comparative Example 3) The water density of each cooling water was 2500 L on the upper surface and the lower surface of the hot-rolled steel strip 4 seconds after the end of hot finish rolling.
Spray cooling set to / min 2 is performed. The material to be cooled and the cooling conditions for the material in the comparative example are the same as those in the first embodiment.
【００４８】すなわち、熱間仕上圧延直後の厚み２．３
ｍｍの低炭素鋼の鋼帯を、搬送速度６００〜１３００ｍ
ｐｍで通過させて冷却を施した。仕上げ圧延直後の鋼帯
の温度は、幅方向において平均温度が８８０〜９１０
℃、幅方向における温度差が３０℃である。鋼帯は、先
端が巻取り機に巻取られるまでの無拘束（無張力）の状
態では６００ｍｐｍで圧延（搬送）され、先端が巻取り
機に巻取られたあとは、加速して１３００ｍｐｍまで加
速した。That is, the thickness 2.3 immediately after hot finish rolling.
mm low carbon steel strip, transfer speed 600 ~ 1300m
Cooling was done by passing at pm. The temperature of the steel strip immediately after finish rolling has an average temperature of 880 to 910 in the width direction.
C., the temperature difference in the width direction is 30.degree. The steel strip is rolled (conveyed) at 600 mpm in the unconstrained state (no tension) until the tip is taken up by the winder, and after the tip is taken up by the winder, it accelerates to 1300 mpm. I accelerated.
【００４９】以上の冷却設備と冷却条件により、仕上げ
圧延時の鋼帯幅方向の温度分布が、第１の実施の形態で
は８８０℃〜９１０℃であったものが、比較例１では７
７０℃〜８５０℃と、最大値と最小値の差が３０℃から
８０℃へと拡大した。比較例２では、６６０℃〜７２０
℃と、最大値と最小値の差が３０℃から６０℃へと拡大
した。比較例３では、６５０〜６９０℃と、最大値と最
小値の差が３０℃から４０℃へと拡大した。その結果、
鋼帯幅方向の引張り強度のバラツキは、比較例１では８
０ＭＰａ、比較例２では６０ＭＰａ、比較例３では４０
ＭＰａであり、第１の実施の形態での２０ＭＰａに比べ
てバラツキが大きかった。With the above cooling equipment and cooling conditions, the temperature distribution in the width direction of the steel strip during finish rolling was 880 ° C. to 910 ° C. in the first embodiment, but was 7 in Comparative Example 1.
70 ° C to 850 ° C, the difference between the maximum value and the minimum value expanded from 30 ° C to 80 ° C. In Comparative Example 2, 660 ° C. to 720
C, and the difference between the maximum and minimum values expanded from 30 to 60 ° C. In Comparative Example 3, the difference between the maximum value and the minimum value expanded from 650 to 690 ° C. from 30 ° C. to 40 ° C. as a result,
The variation in tensile strength in the width direction of the steel strip is 8 in Comparative Example 1.
0 MPa, 60 MPa in Comparative Example 2, 40 in Comparative Example 3
It was MPa, and the variation was larger than 20 MPa in the first embodiment.
【００５０】なお、上述した先行技術２では、水量密度
を２０００Ｌ／ｍｉｎｍ２以上という条件ならば核沸騰
状態が維持されるとの開示情報があるが、鋼帯の圧延速
度が２００〜３００ｍｐｍを越えると２０００Ｌ／ｍｉ
ｎｍ２では、核沸騰状態を維持できなくなり、幅方向に
局所的に遷移沸騰状態が残存してしまう。その結果、冷
却開始時の幅方向の温度ムラが拡大する。なお、鋼帯の
圧延速度は、圧延開始時には５００〜６００ｍｐｍであ
るが、最終的には１０００〜１３００ｍｐｍまで加速さ
れる。したがって、本発明が適用される高速搬送される
鋼帯に対する冷却方法として、水量密度を２５００Ｌ／
ｍｉｎｍ２と規定することにより、極めて有効であると
の結論が得られる。In the above-mentioned prior art 2, there is disclosed information that the nucleate boiling state is maintained under the condition that the water amount density is 2000 L / minm 2 or more, but the rolling speed of the steel strip exceeds 200 to 300 mpm. And 2000L / mi
At nm 2 , the nucleate boiling state cannot be maintained, and the transition boiling state locally remains in the width direction. As a result, the temperature unevenness in the width direction at the start of cooling increases. The rolling speed of the steel strip is 500 to 600 mpm at the start of rolling, but is finally accelerated to 1000 to 1300 mpm. Therefore, as a cooling method for a high-speed conveyed steel strip to which the present invention is applied, a water amount density of 2500 L /
It is concluded that it is extremely effective by defining it as minm 2 .
【００５１】[0051]
【発明の効果】以上説明したように、本発明によれば、
以下に述べるような効果を奏することとなる。
（１）鋼帯幅方向の温度分布変化が解消されて、常に均
一な温度分布の鋼帯が得られる。
（２）鋼帯幅方向の材質の均質性が向上して、品質が安
定する。
（３）鋼帯の幅方向端部における強度はずれがなくな
り、製品の歩留まりが向上する。
（４）エッジヒータやバーヒータなどの補助加熱装置を
設けること、かつ／または、冷却量を制御することで、
鋼帯の長手方向についても温度のバラツキを減らし、特
性の均質化が得られる。As described above, according to the present invention,
The following effects will be obtained. (1) A change in the temperature distribution in the width direction of the steel strip is eliminated, and a steel strip having a uniform temperature distribution is always obtained. (2) The homogeneity of the material in the width direction of the steel strip is improved and the quality is stabilized. (3) The strength at the widthwise end of the steel strip is eliminated and the product yield is improved. (4) By providing an auxiliary heating device such as an edge heater or a bar heater and / or controlling the cooling amount,
Variations in temperature can be reduced in the longitudinal direction of the steel strip, and homogenization of properties can be obtained.
【図１】本発明における冷却方法を実現するための、第
１の実施の形態に係る圧延設備の概要図。FIG. 1 is a schematic diagram of rolling equipment according to a first embodiment for realizing a cooling method according to the present invention.
【図２】本発明における冷却方法を実現するための、第
２の実施の形態に係る圧延設備の概要図。FIG. 2 is a schematic diagram of rolling equipment according to a second embodiment for realizing a cooling method according to the present invention.
【図３】鋼帯の水による冷却の熱伝達特性を説明する
図。FIG. 3 is a diagram illustrating a heat transfer characteristic of cooling a steel strip with water.
【図４】冷却前後の鋼帯中央部と端部の温度差と、水量
密度の関係を表す図。FIG. 4 is a diagram showing the relationship between the temperature difference between the central portion and the end portion of the steel strip before and after cooling and the water density.
【図５】鋼帯の幅方向の温度分布を説明する図。FIG. 5 is a diagram illustrating a temperature distribution in the width direction of a steel strip.
１…粗圧延機、 ２…粗バー、 ３…熱間仕上げ圧延機群、 ４…ランナウトテーブル、 ５…巻取り機、 ６…冷却装置、 ７…円管ラミナーノズル、 ８…スプレーノズル、 ９…水切りパージノズル、 １０…冷却装置入側温度計、 １１…冷却装置出側温度計、 １２…バーヒータ、 １３…エッジヒータ。 1 ... rough rolling machine, 2 ... coarse bar, 3 ... Hot finishing rolling mill group, 4 ... runout table, 5 ... Winder, 6 ... Cooling device, 7 ... Circular tube laminar nozzle, 8 ... Spray nozzle, 9 ... Draining purge nozzle, 10 ... Cooling device inlet side thermometer, 11 ... Cooling device outlet thermometer, 12 ... bar heater, 13 ... Edge heater.
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.7 識別記号 ＦＩ テーマコート゛(参考） Ｃ２１Ｄ 9/52 １０２ Ｃ２１Ｄ 9/52 １０２ (72)発明者 井上 正 東京都千代田区丸の内一丁目１番２号 日 本鋼管株式会社内 (72)発明者 池宗 省三 東京都千代田区丸の内一丁目１番２号 日 本鋼管株式会社内 (72)発明者 今田 貞則 東京都千代田区丸の内一丁目１番２号 日 本鋼管株式会社内 Ｆターム(参考） 4E002 AD01 BD07 BD08 4K043 AA01 BA04 CB04 EA07 FA03 FA13 ─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. 7 Identification code FI theme code (reference) C21D 9/52 102 C21D 9/52 102 (72) Inventor Tadashi Inoue 1-2-1, Marunouchi, Chiyoda-ku, Tokyo No. Nippon Steel Pipe Co., Ltd. (72) Inventor Shozo Ikemune 1-2-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Pipe Co., Ltd. (72) Sadanori Imada 1-2-1 Marunouchi, Chiyoda-ku, Tokyo No. Japan Furukawa Co., Ltd. F term (reference) 4E002 AD01 BD07 BD08 4K043 AA01 BA04 CB04 EA07 FA03 FA13
Claims (4)
却方法であって、冷却水の水量密度を２５００Ｌ／ｍｉ
ｎｍ２以上に設定して冷却することを特徴とする熱延鋼
帯の冷却方法。1. A method for cooling a steel strip with cooling water after hot finish rolling, wherein the water quantity density of cooling water is 2500 L / mi.
A method for cooling a hot-rolled steel strip, which comprises setting the thickness to nm 2 or more and cooling.
ｎｍ２以上に設定した冷却は、熱間仕上げ圧延後２秒未
満の間に開始することを特徴とする請求項１記載の熱延
鋼帯の冷却方法。2. The water quantity density of the cooling water is 2500 L / mi.
The method for cooling a hot-rolled steel strip according to claim 1, wherein the cooling set to nm 2 or more is started within less than 2 seconds after the hot finish rolling.
程にて加熱されたスラブを粗圧延して粗バーとなす粗圧
延工程と、上記粗圧延工程にて粗圧延された粗バーを熱
間仕上げ圧延する熱間仕上げ圧延工程と、上記熱間仕上
げ圧延工程で熱間仕上げ圧延された鋼帯を、請求項１お
よび請求項２のいずれかの冷却方法によって冷却する冷
却工程と、上記冷却工程で冷却された鋼帯を巻き取る巻
き取り工程と、を具備したことを特徴とする熱延鋼帯の
製造方法。3. A heating step of heating a slab, a rough rolling step of roughly rolling the slab heated in the heating step to form a rough bar, and a rough bar rough-rolled in the rough rolling step are heated. A hot finish rolling step of performing hot finish rolling, a cooling step of cooling the steel strip hot finished by the hot finish rolling step by the cooling method according to claim 1 or 2, and the above cooling. A winding process of winding the steel strip cooled in the process, and a method for producing a hot-rolled steel strip.
との間に、粗バーを加熱する加熱工程を有することを特
徴とする請求項３記載の熱延鋼帯の製造方法。4. The method of manufacturing a hot-rolled steel strip according to claim 3, further comprising a heating step of heating a rough bar between the rough rolling step and the hot finish rolling step.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001392504A JP2003191005A (en) | 2001-12-25 | 2001-12-25 | Method for cooling hot-rolled steel strip and its production method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001392504A JP2003191005A (en) | 2001-12-25 | 2001-12-25 | Method for cooling hot-rolled steel strip and its production method |
Publications (1)
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| JP2003191005A true JP2003191005A (en) | 2003-07-08 |
Family
ID=27599801
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|---|---|---|---|
| JP2001392504A Pending JP2003191005A (en) | 2001-12-25 | 2001-12-25 | Method for cooling hot-rolled steel strip and its production method |
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| JP2005279736A (en) * | 2004-03-30 | 2005-10-13 | Jfe Steel Kk | Hot-rolled steel strip manufacturing method |
| WO2007055403A1 (en) * | 2005-11-11 | 2007-05-18 | Jfe Steel Corporation | Cooling apparatus for hot rolled steel band and method of cooling the steel band |
| JP2007152429A (en) * | 2005-11-11 | 2007-06-21 | Jfe Steel Kk | Apparatus and method for cooling hot-rolled steel strip |
| WO2008117552A1 (en) * | 2007-02-26 | 2008-10-02 | Jfe Steel Corporation | Device and method for cooling hot-rolled steel strip |
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2001
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| JP4525133B2 (en) * | 2004-03-30 | 2010-08-18 | Ｊｆｅスチール株式会社 | Manufacturing method of hot-rolled steel strip |
| JP2005279736A (en) * | 2004-03-30 | 2005-10-13 | Jfe Steel Kk | Hot-rolled steel strip manufacturing method |
| US8318080B2 (en) | 2005-11-11 | 2012-11-27 | Jfe Steel Corporation | Device and method for cooling hot strip |
| JP2007152429A (en) * | 2005-11-11 | 2007-06-21 | Jfe Steel Kk | Apparatus and method for cooling hot-rolled steel strip |
| JP4544234B2 (en) * | 2005-11-11 | 2010-09-15 | Ｊｆｅスチール株式会社 | Apparatus and method for cooling hot-rolled steel strip |
| KR101005455B1 (en) * | 2005-11-11 | 2011-01-05 | 제이에프이 스틸 가부시키가이샤 | Cooling apparatus for hot rolled steel band and method of cooling the steel band |
| WO2007055403A1 (en) * | 2005-11-11 | 2007-05-18 | Jfe Steel Corporation | Cooling apparatus for hot rolled steel band and method of cooling the steel band |
| US8506879B2 (en) | 2005-11-11 | 2013-08-13 | Jfe Steel Corporation | Method for cooling hot strip |
| US8231826B2 (en) | 2006-03-03 | 2012-07-31 | Jfe Steel Corporation | Hot-strip cooling device and cooling method |
| US8444909B2 (en) | 2006-03-03 | 2013-05-21 | Jfe Steel Corporation | Hot-strip cooling device |
| WO2008117552A1 (en) * | 2007-02-26 | 2008-10-02 | Jfe Steel Corporation | Device and method for cooling hot-rolled steel strip |
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