JP2020032464A - Method for reducing internal defect of slab and slab production facility - Google Patents
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Abstract
Description
本発明は、連続鋳造機にて鋳造された鋳片の内部欠陥低減方法及び鋳片製造設備に関する。 The present invention relates to a method for reducing internal defects in a slab cast by a continuous casting machine and a slab manufacturing facility.
鋳片には、凝固タイミングの不均一などにより空隙や偏析が発生する。鋳片に空隙や偏析が残存すると、最終製品の品質を損ねるという課題がある。このような内質欠陥（空隙等）を改善するためには、鋳片に圧下を加えることが有効であることが知られている（例えば、特許文献１）。 Voids and segregation occur in the slab due to uneven solidification timing and the like. If voids and segregation remain in the slab, there is a problem that the quality of the final product is impaired. It is known that, in order to improve such internal defects (voids, etc.), it is effective to apply a reduction to a slab (for example, Patent Document 1).
内部欠陥は、最終凝固部に密集しやすい。最終凝固部は、鋳片の板厚中心近傍にあるが、スラブのように厚さに対して幅の広い鋳片においては、その幅方向位置は、幅中央部よりもむしろ幅端部近傍に発生しやすい。そこで、鋳片の幅端部近傍での改善効果を高めるための手法として、例えば特許文献２には、極厚鋼板を対象として、鋳片幅方向の両端部を１５０ｍｍ以上の幅圧下により幅端部を増肉させた上でプレスにより水平圧下を加える方法が開示されている。 Internal defects tend to be concentrated in the final solidification part. The final solidified portion is near the center of the thickness of the slab, but in a slab such as a slab that has a large width relative to its thickness, its width direction position is closer to the width end than to the width center. Likely to happen. Therefore, as a technique for increasing the improvement effect in the vicinity of the width end of the slab, for example, Patent Document 2 discloses an ultra-thin steel plate, in which both ends of the slab in the width direction of the slab are reduced by a width reduction of 150 mm or more. A method is disclosed in which a part is increased in thickness and then horizontal reduction is performed by a press.
しかし、上記特許文献２に記載の技術では、水平圧延をプレス機により行っているが、極厚鋼板を対象としているため、例えば６０００トン級の巨大な装置が必要となる。それゆえ、巨大な装置による間欠型の操業となるため、生産性が低下する。 However, in the technology described in Patent Document 2, horizontal rolling is performed by a press machine. However, since the target is an extremely thick steel plate, a huge device of, for example, 6000 ton class is required. Therefore, the operation is intermittent by a huge device, and the productivity is reduced.
そこで、本発明は、上記問題に鑑みてなされたものであり、本発明の目的とするところは、コンパクトな設備で、かつ、生産性を低下させることなく、鋳片の内部欠陥を低減することが可能な、新規かつ改良された鋳片の内部欠陥低減方法及び鋳片製造設備を提供することにある。 Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to reduce internal defects of a slab, with compact equipment, and without reducing productivity. It is an object of the present invention to provide a new and improved method for reducing internal defects of a slab and a slab manufacturing facility, which are capable of reducing the number of defects.
上記課題を解決するために、本発明のある観点によれば、連続鋳造機から連続して送り出される鋳片を連続鋳造機の機内または下流側で幅圧下した後、幅圧下された鋳片を水平圧延する、鋳片の内部欠陥低減方法が提供される。 In order to solve the above problems, according to an aspect of the present invention, after the width of a cast piece continuously fed from a continuous casting machine is reduced in the machine or on the downstream side of the continuous casting machine, the width of the cast piece is reduced. A method for reducing internal defects in a slab, which is horizontally rolled, is provided.
ここで、横断面における鋳片の凝固状態が完全凝固状態となった後に、鋳片の幅圧下及び水平圧延を行ってもよい。 Here, after the solidified state of the slab in the cross section is completely solidified, the width reduction and horizontal rolling of the slab may be performed.
また、連続鋳造機による鋳造速度、鋳型の冷却温度、電磁攪拌装置による鋳型内溶鋼の電磁攪拌条件、二次冷却装置による冷却条件のうち少なくとも１つを制御することにより、鋳片の幅方向における最終凝固点の幅方向位置を鋳片の幅端部近傍に位置させてもよい。ここで、鋳片の最終凝固点の幅方向位置とは、鋳片の最終凝固点の幅方向分布において、鋳型内の溶鋼湯面から最も遠くなる点の幅方向位置のことを指す。 Also, by controlling at least one of the casting speed by the continuous casting machine, the cooling temperature of the mold, the electromagnetic stirring condition of the molten steel in the mold by the electromagnetic stirring device, and the cooling condition by the secondary cooling device, the width direction of the slab is controlled. The width direction position of the final solidification point may be located near the width end of the slab. Here, the width direction position of the final solidification point of the slab refers to the width direction position of the point farthest from the molten steel surface in the mold in the width direction distribution of the final solidification point of the slab.
ここで、鋳片の板厚をＨ、板幅をＷとしたとき、鋳片の最終凝固点の幅方向位置は、鋳片の幅端部から０．５Ｈ〜０．２５Ｗの範囲としてもよく、または、鋳片の幅端部から０．５Ｈ〜２．０Ｈの範囲としてもよい。 Here, when the plate thickness of the slab is H and the plate width is W, the width direction position of the final solidification point of the slab may be in the range of 0.5H to 0.25W from the width end of the slab, Alternatively, it may be in the range of 0.5H to 2.0H from the width end of the slab.
また、幅圧下された鋳片の横断面中心部の温度が鋳片の表面の温度よりも高い状態で、幅圧下された鋳片を水平圧延してもよい。 Alternatively, the slab whose width has been reduced may be horizontally rolled in a state where the temperature of the center of the cross section of the slab whose width has been reduced is higher than the temperature of the surface of the slab.
幅圧下による鋳片の幅圧下量は、５ｍｍ以上としてもよい。 The width reduction amount of the slab by width reduction may be 5 mm or more.
また、水平圧延では、鋳片の厚さが少なくとも幅圧下する前の鋳片の厚さとなるように、鋳片を圧下するようにしてもよい。 In the horizontal rolling, the slab may be reduced so that the thickness of the slab is at least the thickness of the slab before the width reduction.
さらに、鋳片を幅圧下する前、または、鋳片を水平圧延した後に、鋳片を水平圧延してもよい。 Further, the slab may be horizontally rolled before the width of the slab is reduced or after the slab is horizontally rolled.
また、上記課題を解決するために、本発明の別の観点によれば、連続鋳造機の機内または下流側に、連続鋳造機から連続して送り出される鋳片を幅圧下する幅圧下装置と、幅圧下装置の圧延方向下流側に設けられ、鋳片を水平圧延する水平圧延装置と、を備える、鋳片製造設備が提供される。 In order to solve the above problems, according to another aspect of the present invention, a width reduction device for reducing the width of a slab continuously fed from the continuous casting machine to the inside or downstream of the continuous casting machine, A slab manufacturing facility is provided, which is provided on the downstream side in the rolling direction of the width reduction device and includes a horizontal rolling device for horizontally rolling slabs.
鋳片製造設備は、幅圧下装置に対して圧延方向上流側、または、水平圧延装置に対して圧延方向下流側に、鋳片を水平圧延する第２の水平圧延装置を備えてもよい。 The slab manufacturing facility may include a second horizontal rolling device that horizontally rolls the slab, upstream of the width reduction device in the rolling direction or downstream of the horizontal rolling device in the rolling direction.
以上説明したように本発明によれば、コンパクトな設備で、かつ、生産性を低下させることなく、鋳片の内部欠陥を低減することができる。 As described above, according to the present invention, internal defects of a slab can be reduced with a compact facility without lowering productivity.
以下に添付図面を参照しながら、本発明の好適な実施の形態について詳細に説明する。なお、本明細書及び図面において、実質的に同一の機能構成を有する構成要素については、同一の符号を付することにより重複説明を省略する。 Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the specification and the drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.
＜１．設備構成＞
本発明の各実施形態に係る鋳片の内部欠陥低減方法を説明するにあたり、まず、図１〜図３に基づいて、当該鋳片の内部欠陥低減方法を実施するための設備構成について説明する。図１は、本実施形態に係る鋳片の内部欠陥低減方法を実施するための連続鋳造設備の一構成例を示す説明図である。図２は、図１の連続鋳造設備に設置される幅圧下装置１３０及び水平圧延装置１４０の一例を示す平面図である。図３は、本実施形態に係る鋳片の内部欠陥低減方法を実施するための連続鋳造設備の他の一構成例を示す説明図である。
<1. Equipment Configuration>
Before describing the method for reducing internal defects in a slab according to each embodiment of the present invention, first, based on FIGS. 1 to 3, a facility configuration for performing the method for reducing internal defects in a slab will be described. FIG. 1 is an explanatory diagram showing an example of a configuration of a continuous casting facility for performing a method for reducing internal defects in a slab according to the present embodiment. FIG. 2 is a plan view showing an example of the width reduction device 130 and the horizontal rolling device 140 installed in the continuous casting facility of FIG. FIG. 3 is an explanatory diagram showing another configuration example of a continuous casting facility for performing the method for reducing internal defects in a slab according to the present embodiment.
本実施形態に係る鋳片の内部欠陥低減方法は、連続鋳造直後の鋳片を幅圧下した後、水平圧延を行うものである。鋳片の幅中央ではなく幅端部近傍に内質欠陥が多く発生する鋳片に対し、表面側に比べて内部の温度が高い状態で幅圧下及び水平圧延を行うことで、鋳片の空隙等の内部欠陥を効果的に低減させる。特に、幅圧下後の水平圧延時に、鋳片の横断面中心部の温度が鋳片の表面の温度よりも高い状態で、幅圧下された鋳片の水平圧延を行うのが効果的である。ここで、厚さに対して幅の広い鋳片であるスラブは、幅端部近傍に内質欠陥が多く発生し、幅と厚さとがほぼ等しいビレットやブルームといった棒線形管向けの鋳片では、内質欠陥はその幅中心部に多く発生する。したがって、本発明に係る方法により内部欠陥を低減させる対象とする鋳片は、スラブ等の厚さに対して幅の広い鋳片となる。 The method for reducing internal defects in a slab according to the present embodiment is to perform horizontal rolling after reducing the width of a slab immediately after continuous casting. By performing width reduction and horizontal rolling in a state where the internal temperature is higher than the surface side, the gap of the slab is cast on the slab where many internal defects are generated near the width end rather than the center of the slab. And other internal defects are effectively reduced. In particular, it is effective to perform horizontal rolling of the width-reduced slab in the state where the temperature of the center of the cross section of the slab is higher than the temperature of the surface of the slab during the horizontal rolling after the width reduction. Here, the slab, which is a slab that is wide with respect to its thickness, has many internal defects near the width end, and is a slab for rod-shaped pipes such as billets and blooms whose width and thickness are almost equal. In addition, many internal defects occur at the center of the width. Therefore, a slab whose internal defects are to be reduced by the method according to the present invention is a slab that is wider than the thickness of the slab or the like.
本実施形態に係る鋳片の内部欠陥低減方法を実施するための設備としては、例えば図１に示すように幅圧下装置１３０及び水平圧延装置１４０が機内に設置された連続鋳造設備１００、あるいは、図２に示すような、幅圧下装置２２０及び水平圧延装置２３０が設置された熱間圧延薄スラブ連続鋳造設備２００等がある。 As equipment for performing the method of reducing internal defects in a slab according to the present embodiment, for example, as shown in FIG. 1, a continuous casting equipment 100 in which a width reduction device 130 and a horizontal rolling device 140 are installed, or As shown in FIG. 2, there is a hot-rolled thin slab continuous casting facility 200 in which a width reduction device 220 and a horizontal rolling device 230 are installed.
図１に示す連続鋳造設備１００は、連続鋳造用の鋳型１１５を用いて溶鋼を連続鋳造し、鋳片５を製造するための設備である。図１に示す連続鋳造設備１００は、垂直曲げ型の連続鋳造設備であるが、本発明はかかる例に限定されず、湾曲型、垂直型等の連続鋳造設備であってもよい。連続鋳造設備１００は、図１に示すように、取鍋１１１と、タンディッシュ１１３と、鋳型１１５と、二次冷却装置１２０と、幅圧下装置１３０と、水平圧延装置１４０と、鋳片切断機１５０とを備える。 A continuous casting facility 100 shown in FIG. 1 is a facility for continuously casting molten steel using a continuous casting mold 115 to produce a slab 5. Although the continuous casting equipment 100 shown in FIG. 1 is a vertical bending type continuous casting equipment, the present invention is not limited to such an example, and may be a continuous casting equipment such as a curved type or a vertical type. As shown in FIG. 1, the continuous casting equipment 100 includes a ladle 111, a tundish 113, a mold 115, a secondary cooling device 120, a width reduction device 130, a horizontal rolling device 140, and a slab cutting machine. 150.
溶鋼を搬送する可動式の容器である取鍋１１１は、タンディッシュ１１３の上方から、取鍋１１１内の溶鋼をタンディッシュ１１３に供給する。タンディッシュ１１３に供給された溶鋼は、タンディッシュ１１３内で溶鋼中の介在物が除去された後、鋳型１１５内へ連続供給される。鋳型１１５に供給された溶鋼は、鋳型板との接触部分が冷却され、外殻の凝固シェルの内部に未凝固部を含む鋳片５となる。鋳片５は、鋳型１１５の下方に移動するにつれて内部の未凝固部の凝固が進行し、外殻の凝固シェルの厚さが徐々に厚くなる。かかる凝固シェルと未凝固部を含む鋳片５は、鋳型１１５の下端から引き抜かれる。鋳型１１５から引き抜かれた鋳片５は、二次冷却装置１２０を支持ロール１２１によって支持されながら、鋳造方向下流側へ移動される。二次冷却装置１２０の移動中、鋳片５にはスプレーノズル（図示せず。）によって冷却水が噴射されている。 Ladle 111, which is a movable container for transporting molten steel, supplies molten steel in ladle 111 to tundish 113 from above tundish 113. The molten steel supplied to the tundish 113 is continuously supplied into the mold 115 after inclusions in the molten steel are removed in the tundish 113. The molten steel supplied to the mold 115 is cooled at the portion in contact with the mold plate, and becomes a slab 5 including an unsolidified portion inside the solidified shell of the outer shell. As the slab 5 moves below the mold 115, the solidification of the unsolidified portion inside progresses, and the thickness of the solidified shell of the outer shell gradually increases. The slab 5 including the solidified shell and the unsolidified portion is pulled out from the lower end of the mold 115. The slab 5 pulled out of the mold 115 is moved downstream in the casting direction while the secondary cooling device 120 is supported by the support roll 121. During the movement of the secondary cooling device 120, cooling water is being sprayed onto the slab 5 by a spray nozzle (not shown).
二次冷却装置１２０を通過した鋳片５は、幅圧下装置１３０により板幅方向に圧下された後、水平圧延装置１４０により水平圧延される。幅圧下装置１３０は、図２に示すように、鋳片５の板幅方向両端に設けられたエッジャロール１３１、１３１からなるエッジャ圧延機であってもよい。しかし、本発明はかかる例に限定されず、幅圧下装置１３０は、例えばサイジングプレス等のエッジャ圧延機以外の圧延機であってもよい。水平圧延装置１４０により圧延された鋳片５は、図１に示すように、鋳片切断機１５０によって所定の長さに切断され、切断された厚板状の鋳片７は、テーブルロールにより次工程の設備に搬送される。 The slab 5 that has passed through the secondary cooling device 120 is horizontally reduced by the horizontal rolling device 140 after being reduced in the sheet width direction by the width reduction device 130. As shown in FIG. 2, the width reduction device 130 may be an edger rolling mill including edger rolls 131 provided on both ends of the slab 5 in the sheet width direction. However, the present invention is not limited to this example, and the width reduction device 130 may be a rolling mill other than an edger rolling mill such as a sizing press. The slab 5 rolled by the horizontal rolling device 140 is cut to a predetermined length by a slab cutter 150 as shown in FIG. It is transported to the process equipment.
図３に示す熱間圧延薄スラブ連続鋳造設備２００は、薄板材を製造するための設備であって、厚さに対して幅の広い鋳片５を連続鋳造から熱間圧延までエンドレスで製造する。熱間圧延薄スラブ連続鋳造設備２００は、図３に示すように、薄スラブ連続鋳造機２１０と、幅圧下装置２２０と、水平圧延装置２３０と、粗圧延機２４０と、仕上圧延機２５０と、冷却装置２６０と、巻取機２７０とを備える。薄スラブ連続鋳造機２１０は、取鍋２１１と、タンディッシュ２１３と、鋳型２１５と、二次冷却装置２１７とからなり、図１に示した連続鋳造設備１００と同様に構成されている。薄スラブ連続鋳造機２１０により鋳造された鋳片５は、幅圧下装置２２０により板幅方向に圧下された後、水平圧延装置２３０により水平圧延される。幅圧下装置２２０及び水平圧延装置２３０は、図１の連続鋳造設備１００同等、図２に示したように構成することができる。水平圧延装置２３０により圧延された鋳片５は、粗圧延機２４０及び仕上圧延機２５０を通過して所定の板厚に圧延され、冷却装置２６０により冷却される。冷却装置２６０により冷却された鋳片５は、巻取機２７０によってコイル状に巻き取られる。 The hot-rolled thin slab continuous casting equipment 200 shown in FIG. 3 is an equipment for manufacturing a sheet material, and manufactures a slab 5 having a wide width with respect to its thickness from continuous casting to hot rolling in an endless manner. . As shown in FIG. 3, the hot-rolled thin slab continuous casting facility 200 includes a thin slab continuous caster 210, a width reduction device 220, a horizontal rolling device 230, a rough rolling device 240, a finishing rolling device 250, A cooling device 260 and a winder 270 are provided. The thin slab continuous casting machine 210 includes a ladle 211, a tundish 213, a mold 215, and a secondary cooling device 217, and is configured similarly to the continuous casting facility 100 shown in FIG. The slab 5 cast by the thin slab continuous casting machine 210 is horizontally rolled by the horizontal rolling device 230 after being reduced in the sheet width direction by the width reduction device 220. The width reduction device 220 and the horizontal rolling device 230 can be configured as shown in FIG. 2 equivalent to the continuous casting equipment 100 of FIG. The slab 5 rolled by the horizontal rolling device 230 passes through a rough rolling mill 240 and a finishing rolling mill 250, is rolled to a predetermined thickness, and is cooled by a cooling device 260. The slab 5 cooled by the cooling device 260 is wound into a coil shape by a winder 270.
図１に示す連続鋳造設備１００、図３に示す熱間圧延薄スラブ連続鋳造設備２００のいずれにおいても、連続鋳造の直後、すなわち図１の連続鋳造設備１００では、二次冷却装置１２０による冷却を終えた後であって鋳片切断機１５０によって切断される前、図３の熱間圧延薄スラブ連続鋳造設備２００では、薄スラブ連続鋳造機２１０から送り出された後であって粗圧延機２４０により粗圧延される前に、鋳片５に対して幅圧下と水平圧延とを行う。連続鋳造の直後において鋳片５に対して幅圧下と水平圧延とを行うことで、鋳片５の内部欠陥が改善される。設備内に幅圧下装置及び水平圧延機を加えるため、コンパクトな設備で鋳片５の内部欠陥を低減させることができる。また、幅圧下装置をエッジャ圧延機とすれば、プレス機を用いた場合のように間欠型の操業ではなく連続型の操業となるため、生産性を低下させることなく、鋳片５の内部欠陥を低減させることができる。 In any of the continuous casting facility 100 shown in FIG. 1 and the hot-rolled thin slab continuous casting facility 200 shown in FIG. 3, immediately after continuous casting, that is, in the continuous casting facility 100 shown in FIG. After being finished and before being cut by the slab cutter 150, in the hot-rolled thin slab continuous casting machine 200 of FIG. Before the rough rolling, the slab 5 is subjected to width reduction and horizontal rolling. By performing width reduction and horizontal rolling on the slab 5 immediately after continuous casting, internal defects of the slab 5 are improved. Since the width reduction device and the horizontal rolling mill are added to the equipment, internal defects of the slab 5 can be reduced with a compact equipment. In addition, if the width reduction device is an edger rolling mill, the continuous operation is performed instead of the intermittent operation as in the case of using a press machine. Can be reduced.
＜２．第１の実施形態＞
［２−１．メカニズム］
まず、図４に基づいて、本発明の第１の実施形態に係る鋳片の内部欠陥低減方法により内部欠陥が低減されるメカニズムを説明する。図４は、連続鋳造後、幅圧下後、及び、水平圧延後の鋳片５の横断面形状を示す模式図である。
<2. First Embodiment>
[2-1. mechanism]
First, a mechanism for reducing internal defects by the method for reducing internal defects in a cast slab according to the first embodiment of the present invention will be described with reference to FIG. FIG. 4 is a schematic view showing a cross-sectional shape of the slab 5 after continuous casting, after width reduction, and after horizontal rolling.
鋳片の内部に発生する空隙等の内部欠陥は、鋳片の板厚中心近傍の最終凝固部に密集しやすく、厚さに対して幅の広い鋳片では幅方向においては幅中央部よりも幅端部近傍に発生しやすい。鋳片の内部欠陥の改善には、鋳片を圧下することが有効であり、このとき、内部欠陥部分に大きな静水圧を付与した状態で塑性変形させることが効果的である。これより、鋳片の最終凝固部に対し、高い静水圧応力下で大きな塑性変形が生じるような圧延を施すことで、鋳片の内質が改善され、最終製品の品質を向上できる。 Internal defects such as voids generated inside the slab tend to be concentrated in the final solidified part near the center of the slab thickness, and in the slab having a large width with respect to the thickness, the slab is wider than the central part in the width direction. It is easy to occur near the width end. In order to improve the internal defect of the cast slab, it is effective to reduce the cast slab. At this time, it is effective to plastically deform the internal slab in a state where a large hydrostatic pressure is applied to the internal defective portion. Thus, by performing rolling such that large plastic deformation occurs under a high hydrostatic stress on the final solidified portion of the slab, the internal quality of the slab is improved, and the quality of the final product can be improved.
そこで、本願発明者は、鋳片において内部欠陥の発生しやすい幅端部近傍に高い静水圧下で大きな塑性変形を付与するために、幅圧下により増肉させた後、水平圧延を行うことが有効と考えた。 Therefore, the present inventor, in order to impart a large plastic deformation under high hydrostatic pressure in the vicinity of the width end portion where internal defects are likely to occur in the slab, after increasing the wall thickness by width reduction, it is possible to perform horizontal rolling I thought it was effective.
ここで、鋳片に対して幅圧下と水平圧延とを実施したとき、鋳片５の横断面形状は、図４に示すように変化する。 Here, when width reduction and horizontal rolling are performed on the slab, the cross-sectional shape of the slab 5 changes as shown in FIG.
図４上側の連続鋳造直後の鋳片の横断面形状は、図１の連続鋳造設備１００の二次冷却装置１２０を通過した後の鋳片５、あるいは、図３の熱間圧延薄スラブ連続鋳造設備２００の薄スラブ連続鋳造機２１０を通過した後の鋳片５の横断面形状である。このとき、鋳片５は、板厚Ｈ、板幅Ｗの略矩形状の横断面形状を有している。鋳片５の領域５ａは、空隙等の内部欠陥が発生しやすい板幅端部の領域を示している。 The cross-sectional shape of the slab immediately after continuous casting on the upper side in FIG. 4 is the slab 5 after passing through the secondary cooling device 120 of the continuous casting facility 100 in FIG. 1 or the hot-rolled thin slab continuous casting in FIG. It is a cross-sectional shape of the slab 5 after passing through the thin slab continuous casting machine 210 of the equipment 200. At this time, the slab 5 has a substantially rectangular cross-sectional shape having a plate thickness H and a plate width W. A region 5a of the slab 5 indicates a region at an end portion of the plate width where internal defects such as voids are likely to occur.
連続鋳造直後の鋳片５を幅圧下装置により幅圧下量ΔＥだけ幅圧下すると、鋳片５は、図４中央のような幅端部に増肉が集中する、いわゆるドックボーン形状となる。このとき、空隙等の内部欠陥が発生しやすい領域５ａは、鋳片５の厚肉部分に位置する。その後、幅圧下された鋳片５を水平圧延すると、図４下側のように板厚ｈの略矩形状の鋳片５となる。このとき、幅圧下後の鋳片５の端部側の厚肉部分が幅中央より圧下されるため、領域５ａに高い静水圧応力と大きな塑性変形とが効果的に付与され、その結果、鋳片内部の空隙が低減される。このように、連続鋳造直後の鋳片５を幅圧下した後、水平圧延を行うことで、鋳片内部の空隙を低減させることができる。 When the slab 5 immediately after continuous casting is reduced in width by the width reduction amount ΔE by the width reduction device, the slab 5 has a so-called dock bone shape in which the wall thickness increases at the width end as shown in the center of FIG. At this time, the region 5 a where internal defects such as voids are likely to occur is located in the thick portion of the slab 5. Thereafter, when the slab 5 whose width has been reduced is horizontally rolled, it becomes a substantially rectangular slab 5 having a plate thickness h as shown in the lower side of FIG. At this time, since the thick portion on the end side of the slab 5 after the width reduction is reduced from the center of the width, high hydrostatic stress and large plastic deformation are effectively applied to the region 5a, and as a result, Voids inside the piece are reduced. As described above, by reducing the width of the slab 5 immediately after continuous casting and then performing horizontal rolling, it is possible to reduce voids inside the slab.
なお、鋳片の幅圧下及び水平圧延は、鋳片の横断面における凝固状態が完全凝固状態となった後に行ってもよく、未凝固状態で行ってもよい。 The width reduction and horizontal rolling of the slab may be performed after the solidification state in the cross section of the slab has become a completely solidified state, or may be performed in an unsolidified state.
［２−２．幅圧下量ΔＥ］
本実施形態に係る鋳片の内部欠陥低減方法において、幅圧下装置により鋳片を幅圧下する幅圧下量ΔＥは５ｍｍ以上であればよい。幅圧下量ΔＥが小さすぎると幅端部の増肉部分と幅中央部との板厚差は小さくなるため、幅圧下後に行う水平圧延で、空隙等の内部欠陥が発生しやすい領域５ａに十分な静水圧応力、塑性変形を付与できず、鋳片内部に空隙が残存する。
[2-2. Width reduction ΔE]
In the method for reducing internal defects of a slab according to the present embodiment, the width reduction amount ΔE for reducing the width of the slab by the width reduction device may be 5 mm or more. If the width reduction amount [Delta] E is too small, the thickness difference between the thickened portion at the width end portion and the center portion of the width becomes small. Therefore, the horizontal rolling performed after the width reduction is sufficient for the region 5a where internal defects such as voids are likely to occur. Uneven hydrostatic stress and plastic deformation cannot be applied, and voids remain inside the slab.
有効な幅圧下量ΔＥの値を調べるため、以下の検証を行った。本検証では、板厚２５０ｍｍ、板幅１６００ｍｍに鋳造された一般低炭素鋼の鋳片に対し、連続鋳造機出側にて幅圧下量ΔＥだけ幅圧下を行った後に、１パスの水平圧延により厚さ２２０ｍｍまで圧延した。このようにして得られた鋳片の板幅端部からそれぞれ１００〜３００ｍｍの範囲に対し、ＪＩＳ Ｇ ０８０１で規定された超音波探傷試験を実施し、鋳片の内質を評価した。その結果を図５に示す。図５において、○印はＪＩＳ Ｇ ０８０１に規定された鋳片の超音波探傷試験において合格の品質レベルを示し、×印は不合格の品質レベルを示す。図５より、幅圧下量ΔＥを５ｍｍ以上確保すれば、内質の優れた鋳片を得られることがわかった。 The following verification was performed to check the value of the effective width reduction ΔE. In this verification, the width of the slab of general low carbon steel cast to a thickness of 250 mm and a width of 1600 mm was reduced by the width reduction amount ΔE on the exit side of the continuous casting machine, followed by one-pass horizontal rolling. It was rolled to a thickness of 220 mm. Ultrasonic testing specified in JIS G 0801 was performed on the thus obtained slabs in a range of 100 to 300 mm from the end of the width of the slabs to evaluate the inner quality of the slabs. The result is shown in FIG. In FIG. 5, the mark “○” indicates a quality level of a pass in the ultrasonic flaw detection test of the slab specified in JIS G 0801, and the mark “X” indicates a rejection quality level. From FIG. 5, it was found that if the width reduction ΔE was 5 mm or more, a slab having excellent internal quality could be obtained.
また、別の鋼種の鋳片を用いて、同様の検証を行った。ここでは、板厚２００ｍｍ、板幅１２００ｍｍに鋳造された中炭素鋼の鋳片に対し、連続鋳造機出側にてΔＥだけ幅圧下を行った後に、１パスの水平圧延により厚さ１６０ｍｍまで圧延した。このようにして得られた鋳片の板幅端部からそれぞれ１００〜３００ｍｍの範囲に対し、ＪＩＳ Ｇ ０８０１で規定された超音波探傷試験を実施し、鋳片の内質を評価した。その結果を図６に示す。図６において、○印はＪＩＳ Ｇ ０８０１に規定された鋳片の超音波探傷試験において合格の品質レベルを示し、×印は不合格の品質レベルを示す。図６より、図５の場合と同様、幅圧下量ΔＥを５ｍｍ以上確保すれば、内質の優れた鋳片を得られることがわかった。 In addition, similar verification was performed using a slab of another steel type. Here, a slab of medium carbon steel cast to a sheet thickness of 200 mm and a sheet width of 1200 mm was reduced in width by ΔE on the exit side of the continuous casting machine, and then rolled to a thickness of 160 mm by one-pass horizontal rolling. did. Ultrasonic testing specified in JIS G 0801 was performed on the thus obtained slabs in a range of 100 to 300 mm from the end of the width of the slabs to evaluate the inner quality of the slabs. FIG. 6 shows the result. In FIG. 6, a mark “を” indicates a quality level of acceptance in an ultrasonic flaw detection test of a slab specified in JIS G 0801, and a mark “X” indicates a rejection quality level. From FIG. 6, it was found that, as in the case of FIG. 5, if the width reduction ΔE was 5 mm or more, a cast slab with excellent internal quality was obtained.
以上より、幅圧下装置により鋳片を幅圧下する幅圧下量ΔＥは５ｍｍ以上であればよいといえる。なお、幅圧下量ΔＥの上限値は、図５及び図６に示すように空隙を低減させるとの観点においては特に制限はないが、幅圧下量ΔＥを大きくしすぎると、連続鋳造直後の鋳片は延性が低いため鋳片にワレが発生する可能性がある。本実施形態に係る鋳片の内部欠陥低減方法では、例えば５〜１０ｍｍ程度の幅圧下を行えば十分である。 From the above, it can be said that the width reduction amount ΔE for reducing the width of the slab by the width reduction device should be 5 mm or more. The upper limit of the width reduction ΔE is not particularly limited in view of reducing the gap as shown in FIGS. 5 and 6, but if the width reduction ΔE is too large, the casting immediately after the continuous casting is not performed. Since the piece has low ductility, cracks may occur in the cast piece. In the method for reducing internal defects in a slab according to the present embodiment, it is sufficient to reduce the width by, for example, about 5 to 10 mm.
［２−３．水平圧延での圧下量（水平圧延後の板厚ｈ）］
また、本実施形態に係る鋳片の内部欠陥低減方法において、幅圧下装置により幅圧下された鋳片５を水平圧延で水平圧延するが、このとき、水平圧延後の鋳片５の板厚ｈは、少なくとも幅圧下前の鋳片５の板厚Ｈ以下となるようにするのがよい。水平圧延後の鋳片５の板厚ｈが幅圧下前の鋳片５の板厚Ｈよりも大きいと、鋳片内部の空隙等の内部欠陥を十分に低減させることができないためである。
[2-3. Reduction in horizontal rolling (thickness h after horizontal rolling)]
In the method for reducing internal defects in a slab according to the present embodiment, the slab 5 whose width has been reduced by the width reduction device is horizontally rolled by horizontal rolling. At this time, the thickness h of the slab 5 after the horizontal rolling is obtained. It is preferable that the thickness be at least equal to or less than the thickness H of the slab 5 before the width reduction. If the thickness h of the slab 5 after the horizontal rolling is larger than the thickness H of the slab 5 before the width reduction, internal defects such as voids inside the slab cannot be sufficiently reduced.
有効な水平圧延後の板厚ｈを調べるため、以下の検証を行った。本検証では、厚さ２５０ｍｍ、幅１６００ｍｍに鋳造された一般低炭素鋼の鋳片に対し、連続鋳造出側にて２０ｍｍの幅圧下を行った後に、１パスの水平圧延により厚さｈまで圧延した。このようにして得られた鋳片の板幅端部からそれぞれ１００〜３００ｍｍの範囲に対し、ＪＩＳ Ｇ ０８０１で規定された超音波探傷試験を実施し、鋳片の内質を評価した。その結果を図７に示す。図７において、○印はＪＩＳ Ｇ ０８０１に規定された鋳片の超音波探傷試験において合格の品質レベルを示し、×印は不合格の品質レベルを示す。図７より、水平圧延後の板厚ｈを２５０ｍｍ、つまり、幅圧下前の板厚Ｈと同等以下とすれば内質の優れた鋳片を得られることがわかる。 In order to examine the effective thickness h after horizontal rolling, the following verification was performed. In this verification, a slab of general low carbon steel cast to a thickness of 250 mm and a width of 1600 mm was rolled down to a thickness h by one-pass horizontal rolling after performing a 20 mm width reduction on the continuous casting side. did. Ultrasonic testing specified in JIS G 0801 was performed on the thus obtained slabs in a range of 100 to 300 mm from the end of the width of the slabs to evaluate the inner quality of the slabs. FIG. 7 shows the result. In FIG. 7, a mark “を” indicates a quality level of acceptance in an ultrasonic flaw detection test of a slab specified in JIS G 0801, and a mark “X” indicates a quality level of rejection. From FIG. 7, it can be seen that when the thickness h after the horizontal rolling is 250 mm, that is, equal to or less than the thickness H before the width reduction, it is possible to obtain a slab with excellent internal quality.
また、別の鋼種の鋳片を用いて、同様の検証を行った。ここでは、厚さ２２０ｍｍ、幅１５００ｍｍに鋳造された中炭素鋼の鋳片に対し、連続鋳造出側にて２０ｍｍの幅圧下を行った後に、１パスの水平圧延により厚さｈまで圧延した。このようにして得られた鋳片の板幅端部からそれぞれ１００〜３００ｍｍの範囲に対し、ＪＩＳ Ｇ ０８０１で規定された超音波探傷試験を実施し、鋳片の内質を評価した。その結果を図８に示す。図８において、○印はＪＩＳ Ｇ ０８０１に規定された鋳片の超音波探傷試験において合格の品質レベルを示し、×印は不合格の品質レベルを示す。図８より、水平圧延後の板厚ｈを２２０ｍｍ、つまり、幅圧下前の板厚Ｈと同等以下とすれば、内質の優れた鋳片を得られることがわかる。 In addition, similar verification was performed using a slab of another steel type. Here, a slab of medium carbon steel cast to a thickness of 220 mm and a width of 1500 mm was reduced in width by 20 mm on the continuous casting exit side, and then rolled to a thickness h by one-pass horizontal rolling. Ultrasonic testing specified in JIS G 0801 was performed on the thus obtained slabs in a range of 100 to 300 mm from the end of the width of the slabs to evaluate the inner quality of the slabs. FIG. 8 shows the result. In FIG. 8, the mark “○” indicates a quality level of a pass in the ultrasonic flaw detection test of the slab specified in JIS G 0801, and the mark “X” indicates a rejected quality level. From FIG. 8, it can be seen that when the thickness h after the horizontal rolling is set to 220 mm, that is, equal to or less than the thickness H before the width reduction, a slab having excellent internal quality can be obtained.
［２−４．幅中央部付近の鋳片の内質改善］
本実施形態に係る鋳片の内部欠陥低減方法では、図１あるいは図３に示したように、連続鋳造後の鋳片５を幅圧下した後、水平圧延することで、空隙等の内部欠陥が発生しやすい領域に高い静水圧応力と大きな塑性変形と効果的に付与し、鋳片５の内部欠陥を低減させる。このとき、さらに鋳片５の幅方向中央付近における内質を改善させるため、幅圧下装置に対して圧延方向上流側、または、水平圧延装置に対して圧延方向下流側に、第２の水平圧延装置をさらに設けてもよい。
[2-4. Improving the quality of cast slabs near the center of width]
In the method for reducing internal defects in a slab according to the present embodiment, as shown in FIG. 1 or FIG. 3, after the slab 5 after continuous casting is reduced in width and then horizontally rolled, internal defects such as voids are reduced. A high hydrostatic stress and a large plastic deformation are effectively applied to a region which is likely to occur, and internal defects of the slab 5 are reduced. At this time, in order to further improve the internal quality near the center in the width direction of the slab 5, the second horizontal rolling is performed on the upstream side in the rolling direction with respect to the width reduction device or on the downstream side in the rolling direction with respect to the horizontal rolling device. A device may be further provided.
例えば、第２の水平圧延装置を幅圧下装置の圧延方向上流側に配置することで、鋳片５の幅方向中央付近における内質を改善させることができる。この場合には、さらに、鋳片５の延性を改善し、また、鋳片５の内質を改善するために必要な幅圧下量ΔＥを確保することもできる。具体的な設備構成としては、例えば図９に示す連続鋳造設備１００Ａのように、図１に示した連続鋳造設備１００の幅圧下装置１３０の圧延方向上流側に、第２の水平圧延装置１６０を設ければよい。図３に示した熱間圧延薄スラブ連続鋳造設備２００の場合も同様に、幅圧下装置２２０の圧延方向上流側に第２の水平圧延装置を設ければよい。 For example, by arranging the second horizontal rolling device on the upstream side in the rolling direction of the width reduction device, the internal quality of the slab 5 near the center in the width direction can be improved. In this case, the width reduction ΔE required for improving the ductility of the slab 5 and improving the internal quality of the slab 5 can be further secured. As a specific equipment configuration, for example, as in a continuous casting equipment 100A shown in FIG. 9, a second horizontal rolling mill 160 is provided on the upstream side in the rolling direction of the width reduction device 130 of the continuous casting equipment 100 shown in FIG. It may be provided. Similarly, in the case of the hot-rolled thin slab continuous casting facility 200 shown in FIG. 3, a second horizontal rolling mill may be provided on the upstream side of the width reduction device 220 in the rolling direction.
また、第２の水平圧延装置を水平圧延装置の圧延方向下流側に配置することによっても、鋳片５の幅方向中央付近における内質を改善させることができる。この場合、第２の水平圧延装置は、水平圧延装置の直後、すなわち、図１に示した連続鋳造設備１００の水平圧延装置１４０の直後、あるいは、図３に示した熱間圧延薄スラブ連続鋳造設備２００の水平圧延装置２３０と粗圧延機２４０との間に設置すればよい。なお、熱間圧延薄スラブ連続鋳造設備２００の場合には、粗圧延機２４０による圧延を第２の水平圧延装置による圧延として利用することも可能である。また、第２の水平圧延装置を水平圧延装置の圧延方向下流側に配置する場合には、必ずしも幅圧下装置及び水平圧延装置と同一の設備内に第２の水平圧延装置を配置する必要はない。例えば図１０に示すように、図１に示した連続鋳造設備１００の後工程の設備、例えば熱間圧延設備３００に、第２の水平圧延装置３１０を設置してもよい。 In addition, by arranging the second horizontal rolling device on the downstream side in the rolling direction of the horizontal rolling device, it is also possible to improve the internal quality in the vicinity of the center of the slab 5 in the width direction. In this case, the second horizontal rolling device is immediately after the horizontal rolling device, that is, immediately after the horizontal rolling device 140 of the continuous casting equipment 100 shown in FIG. 1, or the hot-rolled thin slab continuous casting shown in FIG. What is necessary is just to install between the horizontal rolling device 230 and the rough rolling mill 240 of the installation 200. In the case of the hot-rolled thin slab continuous casting equipment 200, rolling by the rough rolling mill 240 can be used as rolling by the second horizontal rolling device. In addition, when the second horizontal rolling device is disposed downstream of the horizontal rolling device in the rolling direction, it is not always necessary to dispose the second horizontal rolling device in the same equipment as the width reduction device and the horizontal rolling device. . For example, as shown in FIG. 10, the second horizontal rolling device 310 may be installed in a post-process facility of the continuous casting facility 100 shown in FIG. 1, for example, in a hot rolling facility 300.
＜３．第２の実施形態＞
［３−１．概要］
上記第１の実施形態では、鋳片の圧下による内質改善に関し、鋳片の幅断面における凝固状態が完全凝固状態または未凝固状態であるときに、鋳片を幅圧下してドッグボーン形状に増肉させた上で水平圧延した。これは、内質欠陥が密集しやすい最終凝固点（クレータエンドとも呼ばれる）の幅方向位置が幅中央部よりも幅端部近傍に生じやすいことを踏まえたものである。
<3. Second Embodiment>
[3-1. Overview]
In the first embodiment, the inner quality is improved by reducing the slab, and when the solidified state in the cross section of the slab is in a completely solidified state or an unsolidified state, the slab is reduced in width to a dog bone shape. After being thickened, it was horizontally rolled. This is based on the fact that the position in the width direction of the final solidification point (also referred to as a crater end) where internal defects are likely to be concentrated is more likely to occur near the width end than at the width center.
一方で、これまでの連続鋳造では、最終凝固点の幅方向均一化を指向することで、内質欠陥の幅端部近傍への密集を抑制、防止しようとしていた。具体的には、連続鋳造機による鋳造速度、鋳型の冷却温度、モールドでの溶鋼の電磁攪拌条件（例えば溶鋼の流動）、または、二次冷却装置による冷却条件を制御することで、最終凝固点の鋳片幅方向分布の形状（すなわち、クレーターエンドの形状）が幅方向に一様となるように指向してきた。しかしながら、鋳片幅方向に均一な最終凝固点を安定的に得ることは難しい。これは、最終凝固点の鋳片幅方向分布の形状は、鋳型に供給される溶鋼の温度、鋳型内の溶鋼の流動挙動に強い影響を受けるが、これらはいずれも、鋳造条件や時間経過に伴って少なからず変化してしまい、このような変化に対応して、電磁撹拌条件、鋳型や二次冷却水による鋳片の冷却条件などを綿密かつ適切に制御することが不可欠なためである。 On the other hand, in the conventional continuous casting, an attempt has been made to suppress and prevent the density defect of the internal defect near the width end by aiming at the uniformization in the width direction of the final solidification point. Specifically, by controlling the casting speed by the continuous casting machine, the cooling temperature of the mold, the electromagnetic stirring conditions of the molten steel in the mold (for example, the flow of molten steel), or the cooling conditions by the secondary cooling device, the final solidification point is controlled. The shape of the slab width direction distribution (that is, the shape of the crater end) has been oriented so as to be uniform in the width direction. However, it is difficult to stably obtain a uniform final solidification point in the slab width direction. This is because the shape of the distribution of final solidification point in the slab width direction is strongly affected by the temperature of molten steel supplied to the mold and the flow behavior of molten steel in the mold. The reason is that it is inevitable to control the electromagnetic stirring condition, the cooling condition of the casting slab by the mold and the secondary cooling water, etc. in a precise and appropriate manner in response to such a change.
そこで、本実施形態では、鋳片の最終凝固点をあえて幅方向に不均一とし、鋳片の最終凝固点の幅方向位置を幅端部近傍に位置させる条件で鋳造した上で、連続鋳造機の機内または下流側で幅圧下した後、幅圧下された鋳片を水平圧延する。これは、上記第１の実施形態にて説明したように、鋳片に幅圧下を加えた上で水平圧延すると幅端部近傍で内質向上効果が最大となることを踏まえ、幅端部近傍の最終凝固点が幅中央部近傍の最終凝固点よりも下流側となるようにして、この最終凝固点の幅方向位置近傍に内質欠陥を集中させることにより、鋳片品質をさらに効果的に向上できると考えることによる。また、特に未凝固圧下を行う場合は圧下位置における固相率が所望の値となるように制御することが重要となるが、本実施形態に係る内質欠陥低減方法によれば、未凝固状態での圧下を必須としないことから、最終凝固点の幅方向不均一をある程度は許容できるため、操業の自由度も高まるとの利点もある。 Therefore, in this embodiment, the final solidification point of the slab is intentionally made non-uniform in the width direction, casting is performed under the condition that the width direction position of the final solidification point of the slab is located near the width end, and then the inside of the continuous casting machine Alternatively, after the width is reduced on the downstream side, the width reduced slab is horizontally rolled. This is because, as described in the first embodiment, when the slab is subjected to horizontal rolling after being subjected to width reduction, the effect of improving the internal quality is maximized in the vicinity of the width end. The final solidification point is located downstream from the final solidification point near the center of the width, and by concentrating the internal defects near the width direction position of the final solidification point, the slab quality can be more effectively improved. By thinking. In particular, when performing unsolidified rolling, it is important to control the solid fraction at the rolling position to a desired value. However, according to the method for reducing internal defects according to the present embodiment, the unsolidified state is reduced. Since it is not essential to reduce the pressure in the process, the unevenness in the width of the final solidification point in the width direction can be tolerated to some extent, and there is also an advantage that the degree of freedom of operation is increased.
［３−２．最終凝固点の制御］
まず、図１１Ａ及び図１１Ｂに基づき、鋳片の最終凝固点の幅方向位置を幅端部近傍に位置させる理由について、説明する。図１１Ａ及び図１１Ｂは、鋳片の幅圧下後の水平圧延における内質改善効果の幅方向分布の一例を示すグラフである。図１１Ａでは幅端部からの幅方向位置を鋳片厚で無次元化して表した場合の結果を示し、図１１Ｂでは幅端部からの幅方向位置を鋳片幅で無次元化して表した場合の結果を示している。図１１Ａ及び図１１Ｂでは、鋳片の板厚Ｈが１００ｍｍ、板幅Ｗが１２００ｍｍの場合（ケース１）、板厚Ｈが２５０ｍｍ、板幅Ｗが１２００ｍｍの場合（ケース２）、及び、板厚Ｈが２５０ｍｍ、板幅Ｗが２０００ｍｍの場合（ケース３）の例を示している。図１１Ａ及び図１１Ｂの横軸は、左側の位置０が幅端部を示し、右側に向かうほど幅中央へ向かうことを示している。
[3-2. Control of final freezing point]
First, the reason why the width direction position of the final solidification point of the slab is located near the width end will be described with reference to FIGS. 11A and 11B. FIG. 11A and FIG. 11B are graphs each showing an example of a width direction distribution of an internal quality improvement effect in horizontal rolling after width reduction of a slab. FIG. 11A shows a result in the case where the width direction position from the width end is represented as dimensionless by the slab thickness, and in FIG. 11B, the width direction position from the width end is represented as dimensionless by the slab width. The result of the case is shown. 11A and 11B, when the thickness H of the slab is 100 mm and the width W is 1200 mm (case 1), when the thickness H is 250 mm and the width W is 1200 mm (case 2), and An example in which H is 250 mm and plate width W is 2000 mm (case 3) is shown. The horizontal axis in FIGS. 11A and 11B indicates that the position 0 on the left side indicates the width end, and that the position toward the right side is toward the center of the width.
図１１Ａ及び図１１Ｂの縦軸に示した内質改善効果は、図１に示した連続鋳造設備を用いて幅圧下した後に水平圧延することによって生じた鋳片の変形から数値解析により得られた応力、ひずみ挙動に基づいて算出したものであり、上に向かうほど内質改善効果が高いことを示す。図１１Ａ及び図１１Ｂを見ると、ケース１〜３のいずれについても、幅端部と幅中央との間で内質改善効果が極大を示す。そこで、内質改善効果が極大を示している領域近傍に鋳片の内質欠陥を集積させた上で、該鋳片に幅圧下を加えた後、水平圧下することで、該領域の内質を飛躍的に向上させることができる。 11A and 11B were obtained by numerical analysis from deformation of a slab caused by horizontal rolling after width reduction using the continuous casting facility shown in FIG. 1. It is calculated based on stress and strain behavior, and shows that the effect of improving the internal quality is higher as going upward. 11A and 11B, in any of Cases 1 to 3, the effect of improving the quality of the inside shows the maximum between the width end and the width center. Therefore, after accumulating the internal defects of the slab in the vicinity of the region where the internal quality improvement effect shows the maximum, after applying the width reduction to the slab, and then performing the horizontal reduction, the internal quality of the region is reduced. Can be dramatically improved.
ここで、側端面からの冷却により、鋳片の幅端部から０．５Ｈまでの範囲には、内質欠陥が集積しにくいことが知られている。さらに、高い内質改善効果が得られるのは、図１１Ａより鋳片の幅端部から２．０Ｈまでの範囲であり、また、図１１Ｂより鋳片の幅端部から０．２５Ｗまでの範囲である。そこで、鋳片の幅端部から０．５Ｈ〜０．２５Ｗの範囲、あるいは、鋳片の幅端部から０．５Ｈ〜２．０Ｈの範囲に内部欠陥を集積させた上で、幅圧下により幅端部を増肉した後に水平圧延することで、鋳片の幅方向全域にわたってさらに良好な内質を得ることができる。これは、鋳片の内質欠陥を上記幅端部近傍に集積させたため、かかる領域以外の領域（例えば、幅中央部付近）においては幅圧下、水平圧延する前の段階で、既に良好な内質を得ることができる。それゆえ、本実施形態に係る補法の適用により、鋳片の幅方向全域にわたって良好な内質を得ることができ、最終製品の品質を向上させることができる。 Here, it is known that due to cooling from the side end surface, internal defects are unlikely to accumulate in a range from the width end of the slab to 0.5H. Further, a high internal quality improvement effect is obtained in the range from the width end of the slab to 2.0H from FIG. 11A, and in the range from 0.25 W to the width end of the slab from FIG. 11B. It is. Therefore, after accumulating internal defects in the range of 0.5H to 0.25W from the width end of the slab or in the range of 0.5H to 2.0H from the width end of the slab, the width is reduced by width reduction. By performing horizontal rolling after increasing the width of the width end, it is possible to obtain a better internal quality over the entire width direction of the slab. This is because the internal defects of the slab were accumulated in the vicinity of the above-mentioned width end portion, and in a region other than such a region (for example, in the vicinity of the width center portion), the width of the slab was reduced before the horizontal rolling. You can get the quality. Therefore, by applying the supplementary method according to the present embodiment, it is possible to obtain a good internal quality over the entire width direction of the slab, and to improve the quality of the final product.
なお、最終凝固位置の検出は既存の手法を用いればよく、例えば予め鋲打ち込み試験を実施して把握する方法や、超音波等を用いた非接触式の検出方法、凝固伝熱解析から算出する方法等を用いればよい。 The final solidification position may be detected by using an existing method, for example, a method of grasping by conducting a tack driving test in advance, a non-contact detection method using ultrasonic waves or the like, and calculating from a solidification heat transfer analysis. A method or the like may be used.
鋳片の最終凝固点の幅方向位置が所望の位置となるように制御する方法としては、連続鋳造機による鋳造速度、鋳型の冷却温度や電磁攪拌装置による鋳型内溶鋼の電磁攪拌条件、または、二次冷却装置による冷却条件のうち少なくともいずれか１つを制御することが考えられる。このうち、二次冷却装置による冷却条件制御は、生産性や鋳片の表面品質などに大きな悪影響を及ぼさずに、鋳片の最終凝固点の幅方向位置を制御できるため、好ましい。そこで、本実施形態に係る鋳片の最終凝固点の幅方向位置制御の一例として、図１２及び図１３に基づいて、二次冷却装置の冷却条件の制御による最終凝固点の幅方向位置の制御方法を説明する。図１２は、連続鋳造設備１００の二次冷却装置１２０の一構成例を示す説明図である。図１３は、スプレーノズルの配置の一例を示す説明図である。 Methods for controlling the width direction position of the final solidification point of the slab to a desired position include a casting speed by a continuous casting machine, a cooling temperature of the mold, electromagnetic stirring conditions of molten steel in the mold by an electromagnetic stirring device, or It is conceivable to control at least one of the cooling conditions of the secondary cooling device. Of these, the cooling condition control by the secondary cooling device is preferable because the position in the width direction of the final solidification point of the slab can be controlled without significantly affecting the productivity and the surface quality of the slab. Therefore, as an example of the width direction position control of the final solidification point of the slab according to the present embodiment, a method of controlling the width direction position of the final solidification point by controlling the cooling conditions of the secondary cooling device based on FIGS. 12 and 13. explain. FIG. 12 is an explanatory diagram illustrating a configuration example of the secondary cooling device 120 of the continuous casting facility 100. FIG. 13 is an explanatory diagram illustrating an example of the arrangement of the spray nozzles.
図１２は、図１の連続鋳造設備１００の二次冷却装置１２０をより詳細に示したものである。図１２に示すように、二次冷却装置１２０は、二次冷却帯において鋳片を挟み込むように対向して配置された複数の支持ロール１２１と、二次冷却帯を通過する鋳片５を冷却する冷却装置（図示せず。）とを有して構成されている。支持ロール１２１は、鋳片５を鋳片通路に沿った鋳造方向Ａに案内するように、鋳片の可動面側（いわゆるＬ面側）の支持ロール群１２１ａと、固定面側（いわゆるＦ面側）の支持ロール群１２１ｂとにより構成される。 FIG. 12 shows the secondary cooling device 120 of the continuous casting facility 100 of FIG. 1 in more detail. As shown in FIG. 12, the secondary cooling device 120 cools the slab 5 passing through the secondary cooling zone and the plurality of support rolls 121 arranged so as to sandwich the slab in the secondary cooling zone. And a cooling device (not shown). The support roll 121 is provided with a support roll group 121a on the movable surface side (so-called L surface side) of the slab and a fixed surface side (so-called F surface) so as to guide the slab 5 in the casting direction A along the slab path. Side) and a support roll group 121b.
鋳型１１５の直下から引き出された鋳片５は、湾曲部１２Ａを通過した後、水平部１２Ｂを通過する。湾曲部１２Ａの最下流側は、鋳片５の形状を垂直から水平にさせる矯正部１２Ｃとなっており、矯正部１２Ｃを通過する際に、鋳片５は湾曲した形状から水平に矯正される。 The slab 5 pulled out from just below the mold 115 passes through the curved portion 12A and then passes through the horizontal portion 12B. The most downstream side of the curved portion 12A is a straightening portion 12C that changes the shape of the cast piece 5 from vertical to horizontal, and when passing through the straightening portion 12C, the cast piece 5 is straightened horizontally from the curved shape. .
二次冷却装置１２０は、鋳型１１５の直下から幅圧下装置（図１の幅圧下装置１３０参照）までの間に設置されている。二次冷却装置１２０により、鋳片５を冷却する冷却ゾーンａ１〜ａ１２が構成される。各冷却ゾーンａ１〜ａ１２には、鋳片５の長辺面に向けて二次冷却水を噴霧する複数のスプレーノズルが配置されている。二次冷却装置１２０を構成する複数のスプレーノズルは、例えば図１３に示すように、幅中央側に設置されるスプレーノズル１２５ｃと、幅端部側に設置されるスプレーノズル１２５ｅとからなる。スプレーノズル１２５ｃは、鋳片長辺面の幅中央側に二次冷却水を噴射し、スプレーノズル１２５ｅは鋳片長辺面の幅端部側に二次冷却水を噴射する。これらのスプレーノズル１２５ｃ、１２５ｅは、鋳片通路のＬ面側とＦ面側の両方に設けられており、鋳片５の両方の長辺面の全体に対して二次冷却水を噴射する。 The secondary cooling device 120 is installed between immediately below the mold 115 and the width reduction device (see the width reduction device 130 in FIG. 1). The secondary cooling device 120 forms cooling zones a1 to a12 for cooling the slab 5. In each of the cooling zones a1 to a12, a plurality of spray nozzles for spraying secondary cooling water toward the long side surface of the slab 5 are arranged. The plurality of spray nozzles constituting the secondary cooling device 120 include, for example, as shown in FIG. 13, a spray nozzle 125c installed at the center of the width and a spray nozzle 125e installed at the end of the width. The spray nozzle 125c injects secondary cooling water toward the width center side of the slab long side surface, and the spray nozzle 125e sprays secondary cooling water toward the width end side of the slab long side surface. These spray nozzles 125c and 125e are provided on both the L surface side and the F surface side of the slab passage, and spray secondary cooling water to the entire long side surface of the slab 5.
幅中央側に設置されるスプレーノズル１２５ｃの二次冷却水の水量密度Ｘ（ｌ／ｍｉｎ／ｍ２）と、幅端部側に設置されるスプレーノズル１２５ｅの二次冷却水の水量密度Ｙ（ｌ／ｍｉｎ／ｍ２）は、独立して制御可能に構成される。これにより、鋳片５の幅方向の位置における冷却能力を異なって設定することができる。本実施形態では、例えば、ある基準条件に対し、鋳片の最終凝固点をより幅端部側に位置させる場合、少なくとも幅端部側の冷却能力を弱めること、または、幅中央側の冷却能力を強めることのいずれかを行えばよい。したがって、少なくとも、幅端部側に設置されるスプレーノズル１２５ｅの二次冷却水の水量密度Ｙを小さくすること、または、幅中央側に設置されるスプレーノズル１２５ｃの二次冷却水の水量密度Ｘを大きくすることのいずれかを行うように、冷却装置は制御される。 The water density X (l / min / m 2 ) of the secondary cooling water of the spray nozzle 125c installed at the width center side and the water density Y (secondary cooling water) of the spray nozzle 125e installed at the width end side. 1 / min / m 2 ) is configured to be independently controllable. Thereby, the cooling capacity at the position in the width direction of the slab 5 can be set differently. In the present embodiment, for example, with respect to a certain reference condition, when the final solidification point of the slab is located closer to the width end, at least the cooling capacity at the width end is weakened, or the cooling capacity at the width center is reduced. You can do one of the strengthening. Therefore, at least, the water density Y of the secondary cooling water of the spray nozzle 125e installed on the width end side is reduced, or the water density X of the secondary cooling water of the spray nozzle 125c installed on the width center side is reduced. The cooling device is controlled to do either of the following.
なお、幅端部側に設置されるスプレーノズル１２５ｅの設置範囲は、幅端部から距離Ｌの範囲内であるが、かかる設置範囲は、例えば図１１Ａ及び図１１Ｂに示した内質改善効果が最大となる位置に応じて決定すればよい。また、図１３では、二次冷却水の水量密度は、幅端部側と幅中央部側とで独立して制御可能としたが、本発明はかかる例に限定されず、幅方向においてより細かく二次冷却水の水量密度を制御可能なように冷却装置を構成してもよい。このように、二次冷却装置１２０の冷却条件、例えば二次冷却水の水量密度を制御することで、鋳片の最終凝固点の幅方向位置を制御することができる。 Note that the installation range of the spray nozzle 125e installed on the width end side is within a range of a distance L from the width end, and such an installation range is, for example, such that the inner quality improvement effect shown in FIGS. What is necessary is just to determine according to the position which becomes the maximum. Further, in FIG. 13, the water amount density of the secondary cooling water can be independently controlled on the width end side and the width center side, but the present invention is not limited to such an example, and the width is finer in the width direction. The cooling device may be configured so that the water density of the secondary cooling water can be controlled. As described above, by controlling the cooling conditions of the secondary cooling device 120, for example, the water density of the secondary cooling water, the width direction position of the final solidification point of the slab can be controlled.
また、二次冷却装置１２０の冷却条件を制御する以外にも、連続鋳造機による鋳造速度を変更したり、鋳型１１５の冷却温度や電磁攪拌装置１１７による鋳型内溶鋼の電磁攪拌条件を変更したりすることで、鋳片の最終凝固点の幅方向位置を制御することができる。鋳片の最終凝固点の幅方向位置の制御は、これらの条件のうち少なくともいずれか１つを変更することで行ってもよい。上述したように、二次冷却装置１２０の冷却条件を制御することが操業上は好ましいが、これだけでは鋳片の最終凝固点の幅方向位置を所望の位置に制御するのが難しいことも考えられる。そこで、複数の条件を変更することで、鋳片の最終凝固点の幅方向位置の制御をより柔軟に行うことができる。 In addition to controlling the cooling condition of the secondary cooling device 120, the casting speed by the continuous casting machine is changed, and the cooling temperature of the mold 115 and the electromagnetic stirring condition of the molten steel in the mold by the electromagnetic stirring device 117 are changed. By doing so, the width direction position of the final solidification point of the slab can be controlled. Control of the width direction position of the final solidification point of the slab may be performed by changing at least one of these conditions. As described above, it is preferable in terms of operation to control the cooling condition of the secondary cooling device 120, but it may be difficult to control the widthwise position of the final solidification point of the slab to a desired position only with this. Therefore, by changing a plurality of conditions, the width direction position of the final solidification point of the slab can be controlled more flexibly.
二次冷却装置１２０による冷却後の鋳片５の処理は、第１の実施形態と同様、幅圧下後、水平圧延を行えばよい。このため、本実施形態では詳細な説明を省略する。 The treatment of the cast slab 5 after cooling by the secondary cooling device 120 may be performed by horizontal rolling after reducing the width similarly to the first embodiment. Therefore, a detailed description is omitted in the present embodiment.
［Ａ．連続鋳造直後の鋳片の幅圧下及び水平圧延］
まず、連続鋳造直後の鋳片に対して、幅圧下及び水平圧延を行うことによる効果を検証した。本検証では、板厚２５０ｍｍ、板幅１６００ｍｍに鋳造された一般低炭素鋼の鋳片に対し、実施例１として連続鋳造機（ＣＣ）出側にて３０ｍｍの幅圧下を行った後に、１パスの水平圧延により厚さ２２０ｍｍまで圧延した上で熱間圧延を行い、板厚５０ｍｍの厚鋼板を製造した。
[A. Width reduction and horizontal rolling of slab just after continuous casting]
First, the effect of performing width reduction and horizontal rolling on a slab immediately after continuous casting was verified. In the present verification, as a first example, a slab of general low carbon steel cast to a plate thickness of 250 mm and a plate width of 1600 mm was subjected to a 30 mm width reduction on the exit side of a continuous casting machine (CC), followed by one pass. Was rolled to a thickness of 220 mm by horizontal rolling, and then hot-rolled to produce a thick steel plate having a thickness of 50 mm.
比較例１として、実施例１と同様の一般低炭素鋼の鋳片に対して幅圧下を行わなかった（すなわち、厚さ２２０ｍｍまでの１パスの水平圧延のみを実施した）上で熱間圧延を行い、板厚５０ｍｍの厚鋼板を製造した。また、比較例２として、実施例１と同様の一般低炭素鋼の鋳片に対して３０ｍｍの幅圧下及び１パスの水平圧延による厚さ２２０ｍｍまでの圧延を、連続鋳造直後ではなく、熱間圧延ラインでの再加熱後に行い、板厚５０ｍｍの厚鋼板を製造した。 As Comparative Example 1, hot rolling was performed on the same low-carbon steel slab as in Example 1 without performing width reduction (ie, performing only one-pass horizontal rolling up to a thickness of 220 mm). Was carried out to produce a thick steel plate having a thickness of 50 mm. Further, as Comparative Example 2, rolling to a thickness of 220 mm by a 30 mm width reduction and one-pass horizontal rolling was performed on a slab of general low carbon steel similar to that in Example 1, not immediately after continuous casting but by hot working. This was performed after reheating in the rolling line to produce a thick steel plate having a thickness of 50 mm.
製造されたこれらの厚鋼板について、鋼板長手方向のミドル部において幅端部から１００〜２００ｍｍの領域、かつ、板厚中心±１０ｍｍの領域から試片を切り出し、顕微鏡にて空隙（ポロシティ）の大きさと個数を観察して調べた。その結果を表１に示す。 For these manufactured thick steel plates, a specimen is cut out from a region of 100 to 200 mm from the width end and a region of ± 10 mm in the center of the thickness in the middle part in the longitudinal direction of the steel plate, and the size of the porosity is measured with a microscope. The number and the number were observed and examined. Table 1 shows the results.
実施例１では、鋼板内部に空隙は確認されず、幅圧下とこれに続く水平圧延を連続鋳造機（ＣＣ）出側にて行うことで、内部欠陥が低減された鋼板が得られた。これは、幅圧下により幅端部を増厚した上で水平圧延を行ったこと、また、鋳片の横断面における温度分布が、鋳片の中心部が鋳片の表面側（すなわち、板厚方向及び板幅方向の端部側）よりも高い温度分布となっている連続鋳造機（ＣＣ）出側にて鋳片に圧下を加えたことによる。鋳片の中心部が鋳片の表面側よりも高い温度分布を有しているとき、鋳片の中心部は、鋳片の表面部よりも変形抵抗が低くなるような分布を有している。したがって、このような鋳片に対して幅圧下及び水平圧延を行うことで、鋳片に存在した内部欠陥の発生領域に高い静水圧応力と大きな塑性変形とを付与することができ、内質の良好な鋳片を熱間圧延に供することができたと考えられる。 In Example 1, no void was observed inside the steel sheet, and a steel sheet with reduced internal defects was obtained by performing width reduction and subsequent horizontal rolling on the exit side of the continuous casting machine (CC). This is because horizontal rolling was performed after the width end was increased by reducing the width, and the temperature distribution in the cross section of the slab was such that the center of the slab was located on the surface side of the slab (that is, the thickness of the slab). This is due to the fact that the slab was pressed down on the exit side of the continuous casting machine (CC) having a higher temperature distribution than the end side in the sheet width direction and the plate width direction). When the center of the slab has a higher temperature distribution than the surface side of the slab, the center of the slab has a distribution such that the deformation resistance is lower than the surface of the slab. . Therefore, by performing width reduction and horizontal rolling on such a slab, it is possible to impart high hydrostatic stress and large plastic deformation to the region where internal defects existed in the slab, and to improve the quality of the inner material. It is considered that good slabs could be subjected to hot rolling.
これに対し、水平圧延のみ実施した比較例１では、鋳片の幅端部が増厚されていない状態で水平圧延を行うため、鋳片の厚み中心かつ幅端部近傍に十分な静水圧応力ならびに塑性変形を付与できず空隙が残存した。また、比較例２では、鋳片（被圧延材）を加熱炉で再加熱した後に幅圧下及び水平圧延を行っているので、熱間圧延において被圧延材の中心部が被圧延材の表面側よりも低い温度分布となる。このため、熱間圧延における幅圧下とこれに続く水平圧延では被圧延材の中心部に十分な静水圧応力を付与できず、空隙が残存した。 On the other hand, in Comparative Example 1 in which only horizontal rolling was performed, since horizontal rolling was performed in a state where the width end of the slab was not increased, sufficient hydrostatic stress was applied to the center of the thickness of the slab and in the vicinity of the width end. In addition, no plastic deformation could be given, and voids remained. In Comparative Example 2, since the slab (rolled material) was reheated in a heating furnace and then subjected to width reduction and horizontal rolling, the central portion of the material to be rolled in hot rolling was on the surface side of the material to be rolled. Lower temperature distribution. For this reason, sufficient hydrostatic stress could not be applied to the center of the material to be rolled in the width reduction in hot rolling and the subsequent horizontal rolling, and voids remained.
［Ｂ．第２の水平圧延装置の設置］
次に、鋳片の幅中央部付近の内質も向上させるために設置する第２の水平圧延装置による効果について検証した。
[B. Installation of second horizontal rolling mill]
Next, the effect of the second horizontal rolling mill installed to improve the inner quality near the center of the width of the slab was verified.
本検証では、板厚２５０ｍｍ、板幅１６００ｍｍに鋳造された一般低炭素鋼の鋳片に対し、実施例２として、連続鋳造機（ＣＣ）出側にて２０ｍｍの幅圧下を行った後に、１パス目の水平圧延により厚さ２２０ｍｍまで圧延した上で熱間圧延を行い、板厚１００ｍｍの厚鋼板を製造した。 In this verification, as a second example, after a 20 mm width reduction was performed on the slab of general low carbon steel cast to a thickness of 250 mm and a width of 1600 mm at the exit side of the continuous casting machine (CC), After rolling to a thickness of 220 mm by horizontal rolling in the pass, hot rolling was performed to produce a thick steel plate having a thickness of 100 mm.
また、実施例３として、実施例２と同様の一般低炭素鋼の鋳片に対して連続鋳造出側にて２０ｍｍの幅圧下を行った後に、１パス目の水平圧延により厚さ２２０ｍｍまで圧延し、さらに第２の水平圧延装置による２パス目の水平圧延により厚さ１８０ｍｍまで圧延した上で、熱間圧延を行い、板厚１００ｍｍの厚鋼板を製造した。 In addition, as Example 3, the same low-carbon steel slab as in Example 2 was subjected to a 20 mm width reduction on the continuous casting side, and then rolled to a thickness of 220 mm by horizontal rolling in the first pass. Then, after rolling to a thickness of 180 mm by the second pass horizontal rolling by a second horizontal rolling device, hot rolling was performed to produce a thick steel plate having a thickness of 100 mm.
さらに、実施例４として、実施例２と同様の一般低炭素鋼の鋳片に対して連続鋳造出側にて水平圧延により厚さ２２０ｍｍまで圧延した後に２０ｍｍの幅圧下を行い、さらに第２の水平圧延装置による水平圧延により厚さ１８０ｍｍまで圧延した上で、熱間圧延を行い、板厚１００ｍｍの厚鋼板を製造した。 Furthermore, as Example 4, the same general low carbon steel slab as in Example 2 was rolled to a thickness of 220 mm by horizontal rolling on the continuous casting side, and then subjected to a 20 mm width reduction. After rolling to a thickness of 180 mm by horizontal rolling using a horizontal rolling device, hot rolling was performed to produce a thick steel plate having a thickness of 100 mm.
一方、比較例３として、幅圧下を行わずに，１パス目の水平圧延により厚さ２２０ｍｍまで，２パス目の水平圧延により厚さ１８０ｍｍまで圧延した上で、熱間圧延を行い、板厚１００ｍｍの厚鋼板を製造した。 On the other hand, as Comparative Example 3, the sheet was rolled to a thickness of 220 mm by horizontal rolling in the first pass and to a thickness of 180 mm by horizontal rolling in the second pass without performing width reduction, and then hot-rolled. A 100 mm thick steel plate was manufactured.
製造されたこれらの厚鋼板について、鋼板長手方向のミドル部において幅端部から１００〜２００ｍｍの領域、かつ、板厚中心±１０ｍｍの領域から試片を切り出し、顕微鏡にて空隙（ポロシティ）の大きさと個数を観察して調べた。その結果を表２に示す。表２において、空隙（ポロシティ）の大きさ及び個数は、板幅中央から±４００ｍｍの範囲におけるものと、両幅端部からそれぞれ４００ｍｍの範囲におけるものとに分けて示した。 For these manufactured thick steel plates, a specimen is cut out from a region of 100 to 200 mm from the width end and a region of ± 10 mm in the center of the thickness in the middle part in the longitudinal direction of the steel plate, and the size of the porosity is measured with a microscope. The number and the number were observed and examined. Table 2 shows the results. In Table 2, the size and the number of voids (porosity) are shown separately in a range of ± 400 mm from the center of the plate width and in a range of 400 mm from both ends of the width.
表２より、比較例３に対し、本発明の実施例２〜４のいずれでも内質の優れた鋼板を得られることがわかる。特に、連続鋳造直後での幅圧下及び水平圧延の実施に加え、さらに水平圧延を１パス以上追加した実施例３及び４では、比較例２よりも空隙の数が減少し、内質のより優れた鋼板を得られることがわかる。本検証で用いた鋳片のように鋳片厚に対して製造厚が厚いものは内部欠陥が存在しやすいが、連続鋳造機（ＣＣ）出側にて幅圧下を行った後、２パスの水平圧延を行う、あるいは、連続鋳造機（ＣＣ）出側にて水平圧延を実施した後、幅圧下を行い、その後さらに１パスの水平圧延を行うことで、内質の良好な鋳片を熱間圧延に提供することができたためと考えられる。 From Table 2, it can be seen that, in comparison with Comparative Example 3, any of Examples 2 to 4 of the present invention can provide a steel sheet with excellent internal quality. In particular, in Examples 3 and 4 in which horizontal rolling was added by one or more passes in addition to the width reduction and horizontal rolling immediately after continuous casting, the number of voids was smaller than in Comparative Example 2, and the inner quality was more excellent. It can be seen that the obtained steel sheet can be obtained. As for the slabs used in this verification, those with a large production thickness relative to the slab thickness are likely to have internal defects. However, after performing the width reduction at the exit side of the continuous casting machine (CC), two passes are required. After horizontal rolling or horizontal rolling at the exit side of the continuous casting machine (CC), width reduction is performed, and then horizontal rolling is further performed for one pass, so that slabs with good internal quality can be heated. It is considered that it could be provided for the inter-rolling.
［Ｃ．最終凝固点の幅方向位置の制御］
次に、鋳片の最終凝固点の幅方向位置を幅端部側に位置させる効果について検証した。
[C. Control of final solidification point in width direction]
Next, the effect of positioning the width direction position of the final solidification point of the slab on the width end side was verified.
本検証では、連続鋳造機にて板厚２５０ｍｍ、板幅１６００ｍｍに鋳造された一般低炭素鋼の鋳片に対し、連続鋳造機出側にて３０ｍｍの幅圧下を行った後に、１パス目の水平圧延により厚さ２２０ｍｍまで圧延した上で熱間圧延を行い、板厚（Ｈ）１００ｍｍの厚鋼板を製造した。 In this verification, the width of a cast piece of general low carbon steel cast to a thickness of 250 mm and a width of 1600 mm by a continuous casting machine was reduced by 30 mm on the exit side of the continuous casting machine, and then the first pass was performed. After rolling to a thickness of 220 mm by horizontal rolling, hot rolling was performed to produce a thick steel plate having a sheet thickness (H) of 100 mm.
本検証では、図１２及び図１３に示した連続鋳造機内の二次冷却帯において、鋳片の幅方向の二次冷却水の水量密度を複数変化させて、鋳片を鋳造した。すなわち、鋳片の幅方向の二次冷却水の水量密度を変化させ、複数の最終凝固点の鋳片幅方向分布の形状（すなわち、クレーターエンドの形状）を有する鋳片を得た。なお、最終凝固点の鋳片幅方向分布の形状は凝固伝熱解析により求めた。 In this verification, in the secondary cooling zone in the continuous casting machine shown in FIGS. 12 and 13, a slab was cast by changing the water density of the secondary cooling water in the width direction of the slab a plurality of times. That is, the water density of the secondary cooling water in the width direction of the slab was changed to obtain a slab having a shape of the slab width direction distribution of a plurality of final solidification points (ie, a crater end shape). In addition, the shape of the slab width direction distribution of the final solidification point was determined by solidification heat transfer analysis.
製造されたこれらの厚鋼板の内質を評価するために、鋼板長手方向のミドル部において、板厚中心±１０ｍｍの領域から試片を切り出し、顕微鏡において空隙（ポロシティ）の大きさと個数を観察して調べた。最終凝固点の鋳片幅方向位置と空隙（ポロシティ）の大きさ及び個数との関係を表３に示す。 In order to evaluate the internal quality of these manufactured thick steel plates, a test piece was cut out from a region of ± 10 mm in the center of the thickness in the middle part in the longitudinal direction of the steel plate, and the size and number of voids (porosity) were observed with a microscope. I checked. Table 3 shows the relationship between the position of the final solidification point in the slab width direction and the size and number of voids (porosity).
表３より、良好な内質を有する厚鋼板が得られたのは、最終凝固点の鋳片幅方向位置が鋳片幅端部から１２５ｍｍ〜５００ｍｍの範囲、つまり、０．５Ｈ〜２．０Ｈの範囲に位置した場合であった。これは、幅圧下による鋳片の幅端部の増肉により、その後の水平圧延においてより高い静水圧応力下で大きな塑性変形が生じる鋳片幅端から０．５Ｈ〜２．０Ｈの範囲に最終凝固位点の幅方向置が位置するように制御することで、当該領域に内部欠陥を集積させた状態で水平圧下が行われ、内質が効果的に改善したためと考えられる。 From Table 3, the reason why the thick steel plate having a good internal quality was obtained is that the position of the final solidification point in the slab width direction is 125 mm to 500 mm from the slab width end, that is, 0.5H to 2.0H. It was a case where it was located in the range. This is because the thickening of the width end of the slab due to width reduction causes a large plastic deformation under higher hydrostatic stress in the subsequent horizontal rolling. It is considered that by controlling the position of the solidification point in the width direction to be located, horizontal reduction was performed in a state where internal defects were accumulated in the region, and the internal quality was effectively improved.
以上、添付図面を参照しながら本発明の好適な実施形態について詳細に説明したが、本発明はかかる例に限定されない。本発明の属する技術の分野における通常の知識を有する者であれば、特許請求の範囲に記載された技術的思想の範疇内において、各種の変更例または修正例に想到し得ることは明らかであり、これらについても、当然に本発明の技術的範囲に属するものと了解される。 As described above, the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that those skilled in the art to which the present invention pertains can conceive various changes or modifications within the scope of the technical idea described in the claims. It is understood that these also belong to the technical scope of the present invention.
なお、以上の説明では本発明を垂直曲げ型の連続鋳造機に適用した例を説明したが、これに限らず、本発明はロール群を垂直に配置した垂直型の連続鋳造機や湾曲型の連続鋳造機などにも適用できる。また、本発明は、スラブに限らずブルームなど鋳片の鋳造にも適用できる。 In the above description, an example in which the present invention is applied to a vertical bending type continuous casting machine has been described. However, the present invention is not limited to this, and the present invention is applicable to a vertical type continuous casting machine in which roll groups are arranged vertically and a curved type casting machine. It can also be applied to continuous casting machines. In addition, the present invention is not limited to slabs, and can be applied to casting of slabs such as blooms.
５ 鋳片
５ａ 内部欠陥が発生しやすい板幅端部の領域
７ 鋳片（切断後）
１１１、２１１ 取鍋
１１３、２１３ タンディッシュ
１１７ 電磁攪拌装置
１１５、２１５ 鋳型
１２０、２１７ 二次冷却装置
１２１ 支持ロール
１２５ｃ、１２５ｅ スプレーノズル
１３０、２２０ 幅圧下装置
１３１ エッジャロール
１４０、２３０ 水平圧延装置
１５０ 鋳片切断機
１６０、３１０ 第２の水平圧延装置
２１０ 薄スラブ連続鋳造機
２４０ 粗圧延機
２５０ 仕上圧延機
２６０ 冷却装置
２７０ 巻取機
5 Cast slab 5a Area at the edge of the plate width where internal defects are likely to occur 7 Cast slab (after cutting)
111, 211 Ladle 113, 213 Tundish 117 Electromagnetic stirring device 115, 215 Mold 120, 217 Secondary cooling device 121 Support roll 125c, 125e Spray nozzle 130, 220 Width reduction device 131 Edger roll 140, 230 Horizontal rolling device 150 Cast piece Cutting machine 160, 310 Second horizontal rolling machine 210 Thin slab continuous casting machine 240 Rough rolling mill 250 Finish rolling mill 260 Cooling device 270 Winding machine
Claims (11)
前記連続鋳造機から連続して送り出される鋳片を幅圧下する幅圧下装置と、
前記幅圧下装置の圧延方向下流側に設けられ、前記鋳片を水平圧延する水平圧延装置と、
を備える、鋳片製造設備。 Inside or downstream of the continuous casting machine,
A width reduction device for reducing the width of a slab continuously fed from the continuous casting machine,
A horizontal rolling device that is provided on the downstream side in the rolling direction of the width reduction device and horizontally rolls the slab,
A slab manufacturing facility comprising:
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6087903A (en) * | 1983-10-18 | 1985-05-17 | Ishikawajima Harima Heavy Ind Co Ltd | Installation for producing steel sheet |
| JPH10263614A (en) * | 1997-03-27 | 1998-10-06 | Kawasaki Steel Corp | Production of extra thick steel plate |
| JPH11701A (en) * | 1997-06-09 | 1999-01-06 | Nkk Corp | Manufacture of ultra-thick steel plate through continuously cast slab |
| JPH11114601A (en) * | 1997-10-14 | 1999-04-27 | Ishikawajima Harima Heavy Ind Co Ltd | Method for rolling-reducing slab width and equipment therefor |
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2019
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6087903A (en) * | 1983-10-18 | 1985-05-17 | Ishikawajima Harima Heavy Ind Co Ltd | Installation for producing steel sheet |
| JPH10263614A (en) * | 1997-03-27 | 1998-10-06 | Kawasaki Steel Corp | Production of extra thick steel plate |
| JPH11701A (en) * | 1997-06-09 | 1999-01-06 | Nkk Corp | Manufacture of ultra-thick steel plate through continuously cast slab |
| JPH11114601A (en) * | 1997-10-14 | 1999-04-27 | Ishikawajima Harima Heavy Ind Co Ltd | Method for rolling-reducing slab width and equipment therefor |
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