JP5742507B2 - Manufacturing method of hot-rolled steel sheet - Google Patents

Manufacturing method of hot-rolled steel sheet Download PDF

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JP5742507B2
JP5742507B2 JP2011141650A JP2011141650A JP5742507B2 JP 5742507 B2 JP5742507 B2 JP 5742507B2 JP 2011141650 A JP2011141650 A JP 2011141650A JP 2011141650 A JP2011141650 A JP 2011141650A JP 5742507 B2 JP5742507 B2 JP 5742507B2
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章翁 篠原
章翁 篠原
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JFE Steel Corp
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Description

本発明は、熱延鋼板の製造方法に関するものである。   The present invention relates to a method for producing a hot-rolled steel sheet.

近年、自動車の軽量化のため、鋼板の高強度化が必要になっている。そして、高強度の熱延鋼板を製造する際には、材質の安定化と加工性向上のために、６００℃以下の低温巻き取りを行うことが多くなっている。   In recent years, it has become necessary to increase the strength of steel sheets in order to reduce the weight of automobiles. And when manufacturing a high-strength hot-rolled steel sheet, low-temperature winding at 600 ° C. or less is frequently performed in order to stabilize the material and improve workability.

しかし、鋼板の高強度化に伴い、熱間圧延機の負荷が高まると同時に、軽量化のため鋼板板厚は薄くなったことから、鋼板形状を安定させることが難しくなってきた。特に、この問題は、板厚２．３ｍｍ以下において顕著である。   However, as the strength of the steel sheet increases, the load on the hot rolling mill increases, and at the same time, the steel sheet thickness is reduced for weight reduction, making it difficult to stabilize the shape of the steel sheet. In particular, this problem is significant when the plate thickness is 2.3 mm or less.

また、低温巻き取りでは、わずかな温度差が大きな材質の差となって現れ、鋼板をプレス加工に供する時に幅方向、長手方向の部位により割れが発生することがあり、従来よりも巻き取り温度を狭い許容範囲で制御する必要が出てきた。   In low-temperature winding, a slight temperature difference appears as a large material difference, and when the steel sheet is subjected to press working, cracks may occur depending on the width direction and longitudinal direction parts. Need to be controlled within a narrow tolerance.

そのため、従来通りのスラブ単位のバッチ式の熱間圧延で高強度の熱延鋼板を製造しようとした場合は、鋼板形状および巻き取り温度が安定するまでに時間がかかり、その間に圧延された鋼板部分は、不適合品として切り捨てられていた。特に薄物製造時には切り捨て量が多かった。   Therefore, when trying to produce a hot rolled steel sheet with high strength by conventional batch-type hot rolling in units of slabs, it takes time until the steel sheet shape and winding temperature are stabilized, and the steel sheet rolled during that time The part was discarded as nonconforming product. In particular, the amount of cut-off was large when manufacturing thin objects.

これに対して、エンドレス圧延と呼ばれる熱間圧延方法によって、高強度の熱延鋼板を製造することが考えられる。   On the other hand, it is conceivable to manufacture a high-strength hot-rolled steel sheet by a hot rolling method called endless rolling.

エンドレス圧延は、例えば特許文献１、２に記載のように、スラブを粗圧延し、粗圧延したシートバーを巻き取り、巻き戻した後、その先端部を先行シートバーの尾端部に接合し、仕上圧延する熱間圧延方法であり、鋼板の先端部および尾端部における不安定現象を抑制することが可能である。   In endless rolling, for example, as described in Patent Documents 1 and 2, the slab is roughly rolled, the sheet bar which has been roughly rolled is wound up and rewound, and then the leading end is joined to the tail end of the preceding sheet bar. This is a hot rolling method in which finish rolling is performed, and it is possible to suppress instability phenomena at the tip and tail ends of the steel sheet.

ただし、通常、高強度の熱延鋼板を製造する際には、高強度を実現するために、Ｓｉ、Ｍｎなどの添加元素を加える方法がとられるので、それによって溶接性を阻害し、エンドレス圧延の際のシートバーの溶接接合が不安定になるという問題がある。   However, when producing high strength hot-rolled steel sheets, usually, a method of adding additive elements such as Si and Mn is used to achieve high strength, thereby inhibiting weldability and endless rolling. In this case, there is a problem that the welding of the seat bar becomes unstable.

特開２００３−２１１２１４号公報JP 2003-211214 A 特開２００６−２３９７７７号公報JP 2006-239777 A

本発明は、上記のような事情に鑑みてなされたものであり、高強度の熱延鋼板を安定して良好な品質で製造することができる熱延鋼板の製造方法を提供することを目的とするものである。   This invention is made | formed in view of the above situations, and it aims at providing the manufacturing method of the hot-rolled steel plate which can manufacture a high strength hot-rolled steel plate stably with favorable quality. To do.

本発明者らは、前記課題を解決するために鋭意検討を行った結果、エンドレス圧延と棒状冷却水による冷却とをコンビネーションした製造方法を着想した。   As a result of intensive studies to solve the above problems, the present inventors have conceived a manufacturing method in which endless rolling and cooling with rod-shaped cooling water are combined.

すなわち、上記の着想に基づいて、本発明は以下の特徴を有している。   That is, based on the above idea, the present invention has the following features.

［１］鋼素材を、板厚２．３ｍｍ以下に熱間圧延後、巻取り温度≦６００℃で巻取り、熱延鋼板とするに際し、熱間圧延を、スラブを粗圧延し、粗圧延したシートバーを巻き取り、巻き戻した後、その先端部を先行シートバーの尾端部に接合し、仕上圧延するエンドレス圧延にて行い、仕上圧延後巻き取りまでの冷却を、ランナウトテーブル上を搬送される鋼板の上面側に、鋼板の進行方向に向けて傾斜させて棒状冷却水を噴射すると共に、その下流側に設けられた水切り手段により冷却水の水切りを行うことを特徴とする熱延鋼板の製造方法。   [1] After hot rolling the steel material to a sheet thickness of 2.3 mm or less, winding the steel material at a coiling temperature ≦ 600 ° C. to form a hot rolled steel sheet, hot rolling, rough rolling the slab, and rough rolling After winding and unwinding the sheet bar, the end of the sheet bar is joined to the tail end of the preceding sheet bar, and finish rolling is used for endless rolling, and cooling is performed on the run-out table after finishing rolling. A hot-rolled steel sheet characterized by spraying bar-shaped cooling water on the upper surface side of the steel sheet to be inclined toward the traveling direction of the steel sheet and draining the cooling water by a draining means provided on the downstream side thereof Manufacturing method.

［２］巻取り温度を４００℃以下とすることを特徴とする前記［１］に記載の熱延鋼板の製造方法。   [2] The method for producing a hot-rolled steel sheet according to [1], wherein the coiling temperature is 400 ° C. or lower.

本発明においては、高強度の熱延鋼板を安定して良好な品質で製造することができる。   In the present invention, a high-strength hot-rolled steel sheet can be stably produced with good quality.

本発明の一実施形態における熱間圧延設備を示す図である。It is a figure which shows the hot rolling installation in one Embodiment of this invention. 本発明の一実施形態における強冷却装置の上面冷却装置を示す図である。It is a figure which shows the upper surface cooling device of the strong cooling device in one Embodiment of this invention. 本発明の一実施形態における強冷却装置の上面冷却装置本体を示す図である。It is a figure which shows the upper surface cooling device main body of the strong cooling device in one Embodiment of this invention.

本発明の一実施形態を図面に基づいて説明する。   An embodiment of the present invention will be described with reference to the drawings.

図１は、本発明の一実施形態における熱間圧延設備を示すものである。   FIG. 1 shows a hot rolling facility in one embodiment of the present invention.

図１に示すように、この実施形態における熱間圧延設備１０は、粗圧延機（図示せず）と、エンドレス圧延用設備１１と、仕上圧延機１２と、ランナウトテーブル１３に設置された従来型冷却装置１４および強冷却装置１５と、巻取り装置（コイラ）１６とを備えている。   As shown in FIG. 1, the hot rolling facility 10 in this embodiment includes a roughing mill (not shown), an endless rolling facility 11, a finishing mill 12, and a conventional type installed on a runout table 13. A cooling device 14 and a strong cooling device 15 and a winding device (coiler) 16 are provided.

ここで、エンドレス圧延用設備１１は、先行するシートバーの尾端部と後行するシートバーの先端部を接合するために、接合装置、コイルボックス、接合用クロップシャーを備えている。更に、バリ取り装置、シートバーヒータ、エッジヒータ、接合部冷却装置、高速通板装置などを適宜設置してもよい。   Here, the endless rolling equipment 11 includes a joining device, a coil box, and a joining crop shear in order to join the tail end portion of the preceding sheet bar and the leading end portion of the following sheet bar. Further, a deburring device, a sheet bar heater, an edge heater, a joint cooling device, a high-speed plate device, and the like may be installed as appropriate.

また、従来型冷却装置１４は、ランナウトテーブル１３上を搬送される鋼板１の上面に対して冷却水を自由落下流として供給する複数の円管ラミナーノズルを有する上面冷却装置１４ａと、その鋼板１の下面に対してスプレー状の冷却水を供給する複数のスプレーノズルを有する下面冷却装置１４ｂを備えている。   The conventional cooling device 14 includes an upper surface cooling device 14a having a plurality of circular laminar nozzles for supplying cooling water as a free fall flow to the upper surface of the steel plate 1 transported on the run-out table 13, and the steel plate 1 The lower surface cooling device 14b having a plurality of spray nozzles for supplying spray-like cooling water to the lower surface of the liquid is provided.

そして、強冷却装置１５は、ランナウトテーブル１３上を搬送される鋼板１の上面に対して冷却水を供給する上面冷却装置１５ａと、その鋼板１の下面に対して冷却水を供給する下面冷却装置１５ｂを備えている。   The strong cooling device 15 includes an upper surface cooling device 15 a that supplies cooling water to the upper surface of the steel plate 1 conveyed on the run-out table 13, and a lower surface cooling device that supplies cooling water to the lower surface of the steel plate 1. 15b.

まず、強冷却装置１５の上面冷却装置１５ａは、図２に示すように、ランナウトテーブル１３上を搬送される鋼板１の上面側に、鋼板１の進行方向に向けて傾斜させて棒状冷却水を噴射する上面冷却装置本体２１と、その下流側に設けられた水切り手段２５とからなっている。   First, as shown in FIG. 2, the upper surface cooling device 15a of the strong cooling device 15 inclines the bar-shaped cooling water on the upper surface side of the steel plate 1 conveyed on the run-out table 13 by inclining it toward the traveling direction of the steel plate 1. It consists of an upper surface cooling device main body 21 to be sprayed and a draining means 25 provided on the downstream side thereof.

上面冷却装置本体２１には、図３に示すように、冷却ヘッダ２２に鋼板幅方向に所定のピッチ（例えば、６０ｍｍピッチ）で一列に配置された円管ノズル２３が、鋼板進行方向に所定のピッチ（例えば、１００ｍｍピッチ）で所定の列数（例えば、１００列）設けられている。なお、円管ノズル２３は各列毎に１本の冷却ヘッダ２２を経由して冷却水供給管２４に接続されており、各冷却水供給管２４は独立にオン−オフ制御可能となっている。   As shown in FIG. 3, the upper surface cooling device main body 21 has circular pipe nozzles 23 arranged in a row at a predetermined pitch (for example, 60 mm pitch) in the steel plate width direction on the cooling header 22 in a predetermined direction in the steel plate traveling direction. A predetermined number of columns (for example, 100 columns) is provided at a pitch (for example, 100 mm pitch). The circular tube nozzle 23 is connected to the cooling water supply pipe 24 via one cooling header 22 for each row, and each cooling water supply pipe 24 can be controlled on and off independently. .

円管ノズル２３は、所定の内径（例えば、８ｍｍφ）を備えた内面が滑らかな直管ノズルで、円管ノズル２３から供給される冷却水は棒状冷却水である。そして、この円管ノズル２３は、棒状冷却水を鋼板１の進行方向に向けて所定の噴射角度θ（例えば、θ＝５０°）で噴射するように傾斜して配置されている。   The circular tube nozzle 23 is a straight tube nozzle having a predetermined inner diameter (for example, 8 mmφ) and a smooth inner surface, and the cooling water supplied from the circular tube nozzle 23 is a rod-shaped cooling water. And this circular pipe nozzle 23 is inclined and arrange | positioned so that rod-shaped cooling water may be injected in the advancing direction of the steel plate 1 with predetermined | prescribed injection angle (theta) (for example, (theta) = 50 degrees).

ここで、本発明における棒状冷却水とは、円形状（楕円や多角の形状も含む）のノズル噴出口からある程度加圧された状態で噴射される冷却水であって、ノズル噴出口からの冷却水の噴射速度が７ｍ／ｓ以上であり、ノズル噴出口から鋼板に衝突するまでの水流の断面がほぼ円形に保たれた連続性と直進性のある水流の冷却水のことをいう。すなわち、円管ラミナーノズルからの自由落下流や、スプレーのような液滴状態で噴射されるものとは異なる。   Here, the rod-shaped cooling water in the present invention is cooling water injected in a state of being pressurized to some extent from a circular (including elliptical or polygonal) nozzle outlet, and is cooled from the nozzle outlet. The water injection speed is 7 m / s or more, and it refers to cooling water of continuous and straight water flow in which the cross section of the water flow from the nozzle outlet to the steel plate is maintained in a substantially circular shape. That is, it is different from a free fall flow from a circular tube laminar nozzle or a liquid ejected in a droplet state such as a spray.

また、水切り手段２５としては、水切り用流体を噴射するノズル（ここでは、棒状冷却水を噴射するノズル）２６が設置されている。この水切り用の棒状冷却水は、冷却を目的とするものではないが、上面冷却装置本体２１の円管ノズル２３からの棒状冷却水と同様に、冷却水を用い、加圧状態で噴射され、ノズル噴出口から鋼板１に衝突するまでの水流の断面がほぼ円形に保たれた連続性と直進性のある水流を用いるので、ここでは棒状冷却水と呼ぶこととする。   Further, as the draining means 25, a nozzle (in this case, a nozzle for ejecting rod-shaped cooling water) 26 for ejecting a draining fluid is installed. This rod-shaped cooling water for draining is not intended for cooling, but is used in the same manner as the rod-shaped cooling water from the circular tube nozzle 23 of the upper surface cooling device body 21, and is injected in a pressurized state, Since a continuous and straight water flow in which the cross section of the water flow from the nozzle outlet to the steel plate 1 is maintained in a substantially circular shape is used, it is referred to as rod-shaped cooling water here.

この棒状冷却水噴射ノズル２６は、所定のノズル径（例えば、内径５ｍｍ）、ノズルピッチ（例えば、３０ｍｍ）、列数（例えば、３列）で、上面冷却装置本体２１の下流側に配置されており、上面冷却装置本体２１からの棒状冷却水に対向するように、上面冷却装置本体２１側に向けて傾斜した棒状冷却水を噴射する。棒状冷却水噴射ノズル２６から噴射される棒状冷却水と鋼板１との成す角度ηは、上面冷却装置本体２１からの棒状冷却水の噴射角度θと同程度であり、６０°以下が好ましく、５５°以下が一層好ましい。   The rod-shaped cooling water injection nozzle 26 is arranged on the downstream side of the upper surface cooling device main body 21 with a predetermined nozzle diameter (for example, an inner diameter of 5 mm), a nozzle pitch (for example, 30 mm), and the number of rows (for example, three rows). In addition, the rod-shaped cooling water inclined toward the upper surface cooling device main body 21 side is sprayed so as to face the rod-shaped cooling water from the upper surface cooling device main body 21. The angle η formed by the rod-shaped cooling water sprayed from the rod-shaped cooling water spray nozzle 26 and the steel plate 1 is approximately the same as the spray angle θ of the rod-shaped cooling water from the upper surface cooling device body 21, and is preferably 60 ° or less, 55 More preferably, it is less than 0 °.

なお、水切り手段２５としては、上記の棒状冷却水噴射ノズル２６に替えて、ピンチロール方式の水切りロールを用いることでもよい。   In addition, as the draining means 25, it may replace with said rod-shaped cooling water injection nozzle 26, and may use the draining roll of a pinch roll system.

一方、強冷却装置１５の下面冷却装置１５ｂは、従来型冷却装置１４の下面冷却装置１４ｂと同様のものであり、鋼板１の下面に対してスプレー状の冷却水を供給する複数のスプレーノズルを有している。   On the other hand, the lower surface cooling device 15b of the strong cooling device 15 is the same as the lower surface cooling device 14b of the conventional cooling device 14, and includes a plurality of spray nozzles that supply spray-like cooling water to the lower surface of the steel plate 1. Have.

このように、強冷却装置１５が、棒状冷却水を鋼板１の進行方向に向けて噴射角度θで噴射する複数の円管ノズル２３と、上面冷却装置本体２１からの棒状冷却水に対向するように棒状冷却水を噴射する水切り用棒状冷却水噴射ノズル２６を備えていることから、円管ノズル２３から鋼板１上面に供給された後の冷却水（滞留水）が鋼板１の進行方向に向けて流動するとともに、流動した滞留水が水切り用棒状冷却水噴射ノズル２６からの棒状冷却水によって堰き止められるようになるので、冷却水による冷却領域が一定になる。そして、円管ノズル２３から棒状冷却水が噴射されるので、鋼板１上面の滞留水の水膜を破って鋼板１まで新鮮な冷却水を到達させることができる。これによって、均一で冷却速度の速い強冷却を行うことが可能となる。   In this way, the strong cooling device 15 faces the rod-shaped cooling water from the upper surface cooling device main body 21 and the plurality of circular tube nozzles 23 that inject the rod-shaped cooling water at the injection angle θ toward the traveling direction of the steel plate 1. Since the rod-shaped cooling water injection nozzle 26 for spraying the rod-shaped cooling water is provided on the upper surface of the steel plate 1, the cooling water (residual water) after being supplied from the circular tube nozzle 23 to the upper surface of the steel plate 1 is directed toward the traveling direction of the steel plate 1. In addition, the accumulated water that has flowed is blocked by the rod-shaped cooling water from the rod-shaped cooling water injection nozzle 26 for draining, so that the cooling area by the cooling water becomes constant. And since rod-shaped cooling water is injected from the circular tube nozzle 23, the water film of the staying water on the upper surface of the steel plate 1 can be broken, and fresh cooling water can reach the steel plate 1. This makes it possible to perform strong cooling that is uniform and has a high cooling rate.

そして、上記のように構成された熱間圧延設備１０において、板厚２．３ｍｍ以下の高強度熱延鋼板を製造する際には、以下のようにして行う。   And in the hot rolling equipment 10 comprised as mentioned above, when manufacturing a high intensity | strength hot-rolled steel plate with a plate | board thickness of 2.3 mm or less, it carries out as follows.

すなわち、まず、熱間圧延を、粗圧延機によってスラブ（鋼素材）を粗圧延し、エンドレス圧延用設備１１によって、粗圧延したシートバーを巻き取り、巻き戻した後、その先端部を先行シートバーの尾端部に接合し、仕上圧延機１２によってシートバーを目標板厚（２．３ｍｍ以下）に仕上圧延するエンドレス圧延にて行い、仕上圧延後の巻き取りまでの冷却を、ランナウトテーブル１３に設置された従来型冷却装置１４と強冷却装置１５で行って、６００℃以下（必要により、４００℃以下）の巻取り温度で巻取り装置（コイラ）１６に巻取る。   That is, first, hot rolling is performed, a slab (steel material) is roughly rolled by a roughing mill, and the roughly rolled sheet bar is taken up and rewound by the endless rolling equipment 11, and then the leading end portion is set as a preceding sheet. The runout table 13 is joined to the tail end of the bar, and is subjected to endless rolling in which the finish bar 12 finish-rolls the sheet bar to a target plate thickness (2.3 mm or less). The conventional cooling device 14 and the strong cooling device 15 installed on the winding device 16 are wound around the winding device (coiler) 16 at a winding temperature of 600 ° C. or lower (400 ° C. or lower if necessary).

これによって、この実施形態においては、板厚２．３ｍｍ以下の高強度熱延鋼板を安定して良好な品質で製造することができる。   Thereby, in this embodiment, a high-strength hot-rolled steel sheet having a thickness of 2.3 mm or less can be stably manufactured with good quality.

すなわち、低温巻取りを行うための冷却に、均一で冷却速度の速い強冷却を行うことが可能な強冷却装置１５（棒状冷却水を傾斜して噴射する複数の円管ノズル２３、水切り用棒状冷却水噴射ノズル２６）を用いていることによって、上記したような低温巻取りにおいても鋼板１の冷却を均一化できるとともに、Ｓｉ、Ｍｎなどの添加元素を増すことなく高強度化を実現できるようになり、溶接性を阻害することが回避されて、鋼板１の先端部および尾端部における不安定現象を抑制することが可能であるエンドレス圧延を行うことが容易になることから、鋼板１の先尾端の形状バラツキおよび材質バラツキを改善することができるようになる。   That is, a strong cooling device 15 (a plurality of circular pipe nozzles 23 for injecting a rod-shaped cooling water at an angle and a rod shape for draining) capable of performing strong cooling at a uniform and high cooling rate for cooling for low-temperature winding. By using the cooling water injection nozzle 26), the steel plate 1 can be uniformly cooled even in the low temperature winding as described above, and high strength can be realized without increasing additive elements such as Si and Mn. Therefore, it is easy to perform endless rolling that can suppress the instability phenomenon at the front end portion and the tail end portion of the steel plate 1 by preventing the weldability from being hindered. It becomes possible to improve the shape variation and material variation of the leading end.

また、強冷却装置１５の使用・不使用あるいは使用ノズル本数の変更により、冷却温度と巻取り温度を変更することができ、同一成分で複数の機械的特性（例えば、同一引張強度で高伸びと高伸びフランジや、引張強度３７０ＭＰａと４４０ＭＰａの造り分け）を実現できるという効果もある。   In addition, the cooling temperature and the coiling temperature can be changed by using / not using the strong cooling device 15 or changing the number of nozzles used, and a plurality of mechanical properties (for example, the same tensile strength and high elongation can be obtained). There is also an effect that it is possible to realize a high-elongation flange and the production of a tensile strength of 370 MPa and 440 MPa.

本発明の実施例として、板厚１．６ｍｍの高強度熱延鋼板を製造した。   As an example of the present invention, a high-strength hot-rolled steel sheet having a thickness of 1.6 mm was manufactured.

その際に、本発明例１として、上記の実施形態に基づいて、熱間圧延をエンドレス圧延にて行った後、仕上圧延機１２の出口での鋼板温度８５０℃から従来型冷却装置１４を使用して７００℃まで冷却し、強冷却装置１５によって４００℃まで冷却した。その結果、このときの鋼板１の全幅全長での温度バラツキは±１０℃以内を実現可能であった。   At that time, as Example 1 of the present invention, based on the above embodiment, after performing hot rolling by endless rolling, the conventional cooling device 14 is used from a steel plate temperature of 850 ° C. at the exit of the finishing mill 12. Then, it was cooled to 700 ° C. and cooled to 400 ° C. by the strong cooling device 15. As a result, the temperature variation over the entire width of the steel plate 1 at this time could be within ± 10 ° C.

これに対して、比較例１として、熱間圧延を従来通りのスラブ単位のバッチ式圧延で行った。その結果、このときの鋼板１の全幅全長での温度バラツキは±３０℃であった。   On the other hand, as Comparative Example 1, hot rolling was performed by conventional batch-type rolling in units of slabs. As a result, the temperature variation over the entire width of the steel plate 1 at this time was ± 30 ° C.

また、比較例２として、熱間圧延を従来通りのスラブ単位のバッチ式圧延で行うとともに、従来型冷却装置１４のみを使用して４００℃まで冷却した。その結果、巻取り温度は３００〜４２０℃であった。   Moreover, as Comparative Example 2, hot rolling was performed by conventional batch-type rolling in units of slabs, and cooled to 400 ° C. using only the conventional cooling device 14. As a result, the coiling temperature was 300 to 420 ° C.

また、本発明例１では、鋼板１の引張強度は４４０ＭＰａ相当であったが、本発明例２として、強冷却装置１５を半分の冷却能力とすることにより巻取り温度を５５０℃とした場合には、鋼板１の引張強度は３７０ＭＰａ相当となった。   Further, in Example 1 of the present invention, the tensile strength of the steel sheet 1 was equivalent to 440 MPa. However, as Example 2 of the present invention, when the coiling temperature was set to 550 ° C. by setting the strong cooling device 15 to a half cooling capacity. The tensile strength of the steel plate 1 was equivalent to 370 MPa.

さらに、本発明例３として、別の成分系で、強冷却装置１５を使用した場合は、鋼板１の引張強度は５９０ＭＰａ相当であったが、伸び２５％、伸びフランジ性１００％であったのに対して、本発明例４として、従来型冷却装置１４で５５０℃まで冷却し、強冷却装置１４で４００℃まで冷却した場合は、伸び２８％、伸びフランジ性８０％となった。   Further, as Example 3 of the present invention, when the strong cooling device 15 was used in another component system, the tensile strength of the steel sheet 1 was equivalent to 590 MPa, but the elongation was 25% and the stretch flangeability was 100%. On the other hand, as Example 4 of the present invention, when the conventional cooling device 14 was cooled to 550 ° C. and the strong cooling device 14 was cooled to 400 ° C., the elongation was 28% and the stretch flangeability was 80%.

１ 鋼板
１０ 熱間圧延設備
１１ エンドレス圧延用設備
１２ 仕上圧延機
１３ ランナウトテーブル
１４ 従来型冷却装置
１４ａ 従来型冷却装置の上面冷却装置
１４ｂ 従来型冷却装置の下面冷却装置
１５ 強冷却装置
１５ａ 強冷却装置の上面冷却装置
１５ｂ 強冷却装置の下面冷却装置
１６ 巻取り装置
２１ 上面冷却装置本体
２２ 冷却ヘッダ
２３ 円管ノズル
２４ 冷却水供給管
２５ 水切り手段
２６ 水切り用棒状冷却水噴射ノズル DESCRIPTION OF SYMBOLS 1 Steel plate 10 Hot rolling equipment 11 Endless rolling equipment 12 Finishing mill 13 Runout table 14 Conventional cooling device 14a Conventional cooling device upper surface cooling device 14b Conventional cooling device lower surface cooling device 15 Strong cooling device 15a Strong cooling device Upper surface cooling device 15b Lower surface cooling device of strong cooling device 16 Winding device 21 Upper surface cooling device body 22 Cooling header 23 Circular pipe nozzle 24 Cooling water supply pipe 25 Draining means 26 Drained rod cooling water jet nozzle

Claims (2)

鋼素材を、板厚２．３ｍｍ以下に熱間圧延後、巻取り温度≦６００℃で巻取り、熱延鋼板とするに際し、
熱間圧延を、スラブを粗圧延し、粗圧延したシートバーを巻き取り、巻き戻した後、その先端部を先行シートバーの尾端部に接合し、仕上圧延するエンドレス圧延にて行い、
仕上圧延後巻き取りまでの冷却を、従来型冷却装置と強冷却装置を用いて行い、
前記従来型冷却装置は、ランナウトテーブル上を搬送される鋼板の上面に対して冷却水を自由落下流として供給する複数の円管ラミナーノズルを有する上面冷却装置と、鋼板の下面に対してスプレー状の冷却水を供給する複数のスプレーノズルを有する下面冷却装置を備えており、
前記強冷却装置は、ランナウトテーブル上を搬送される鋼板の上面側に、鋼板の進行方向に向けて傾斜させて棒状冷却水を噴射すると共に、その下流側に設けられた水切り手段により冷却水の水切りを行う上面冷却装置と、鋼板の下面に対してスプレー状の冷却水を供給する複数のスプレーノズルを有する下面冷却装置を備えており、
前記強冷却装置の使用・不使用あるいは使用ノズル本数の変更により、冷却温度と巻取り温度を変更することによって、同一成分で複数の機械的特性の鋼板を造り分けることを特徴とする熱延鋼板の製造方法。 When the steel material is hot-rolled to a thickness of 2.3 mm or less and then wound at a coiling temperature ≦ 600 ° C. to obtain a hot-rolled steel sheet,
After hot rolling, roughly rolling the slab, winding the roughly rolled sheet bar, rewinding, joining the tip to the tail end of the preceding sheet bar, performing endless rolling to finish rolling,
Cooling from finish rolling to winding is performed using conventional cooling equipment and strong cooling equipment,
The conventional cooling device includes a top surface cooling device having a plurality of circular laminar nozzles for supplying cooling water as a free fall flow to the upper surface of the steel sheet conveyed on the run-out table, and a spray form on the lower surface of the steel sheet. A lower surface cooling device having a plurality of spray nozzles for supplying the cooling water of
The strong cooling device injects the bar-shaped cooling water on the upper surface side of the steel sheet conveyed on the run-out table in an inclined direction toward the traveling direction of the steel sheet, and the cooling water is provided by a draining means provided on the downstream side. An upper surface cooling device for draining water, and a lower surface cooling device having a plurality of spray nozzles for supplying spray-like cooling water to the lower surface of the steel plate,
A hot-rolled steel sheet characterized in that a steel plate having a plurality of mechanical properties with the same component is produced by changing the cooling temperature and the coiling temperature by using / not using the strong cooling device or changing the number of nozzles used. Manufacturing method. 巻取り温度を４００℃以下とすることを特徴とする請求項１に記載の熱延鋼板の製造方法。   The method for producing a hot-rolled steel sheet according to claim 1, wherein the coiling temperature is 400 ° C or lower.
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