JP6575355B2

JP6575355B2 - Continuous casting machine

Info

Publication number: JP6575355B2
Application number: JP2015257005A
Authority: JP
Inventors: 塚口　友一; 友一塚口
Original assignee: Nippon Steel Corp
Current assignee: Nippon Steel Corp
Priority date: 2015-12-28
Filing date: 2015-12-28
Publication date: 2019-09-18
Anticipated expiration: 2035-12-28
Also published as: JP2017119296A

Description

本発明は、鋼の連続鋳造において取鍋からタンディッシュへの注湯に筒状の注入管を用いる連続鋳造機および連続鋳造方法に関する。 The present invention relates to a continuous casting machine and a continuous casting method using a cylindrical injection pipe for pouring from a ladle to a tundish in continuous casting of steel.

鋼を連続鋳造するに際しては、大気中における酸化による介在物発生を防止することが必須である。このためには、取鍋からタンディッシュに溶鋼を注入する際に、外部雰囲気からの酸化を防止すべく、注入溶鋼流の周囲を耐火物製の筒状体である注入管又はロングノズルにより覆い、注入流を外気と遮断して注入を行う。 In continuous casting of steel, it is essential to prevent inclusions from being oxidized due to oxidation in the atmosphere. For this purpose, when pouring molten steel from the ladle into the tundish, in order to prevent oxidation from the external atmosphere, the periphery of the molten molten steel flow is covered with an injection tube or a long nozzle made of a refractory cylinder. The injection flow is cut off from the outside air.

注入管を用いて溶鋼を注入する場合、注入管はタンディッシュ蓋に設けられ、筒状体である注入管下端はタンディッシュ内の溶鋼中に浸漬し、注入管の上部は天蓋（いわゆる陣笠）で覆われる。天蓋は、取鍋底部のスライディングノズル部に取り付けられ、スライディングノズル下の取鍋ノズルが天蓋の開口部を貫通して下部に注入孔を向けて配置される。定常の鋳造時には、天蓋が注入管の上面に当接して蓋をし、取鍋ノズルからタンディッシュへの注入流が外部から遮断され、内部に導入した不活性ガスにより注入流がシールされる。注入管内を不活性ガスでシールする場合、注入管の上部に配置された天蓋に不活性ガス導入孔を設置し、あるいは注入管の側面に不活性ガス導入孔を設置して、注入管内にＡｒガスを噴出・供給している（特許文献１〜５参照）。
注入管内の湯面では、取鍋からの注入流が注入管内の雰囲気であるＡｒ等の不活性ガスを叩き込んで、溶鋼中に多くの気泡が発生する。発生した気泡は、溶鋼中に懸濁する非金属介在物を捕捉するとともにタンディッシュ内に緩やかな上昇流を生じることによって溶鋼を清浄化する効果を有する。 When injecting molten steel using an injection tube, the injection tube is provided on the tundish lid, the lower end of the injection tube, which is a cylindrical body, is immersed in the molten steel in the tundish, and the top of the injection tube is a canopy (so-called Jinkasa) Covered with. The canopy is attached to the sliding nozzle portion at the bottom of the ladle, and the ladle nozzle under the sliding nozzle is disposed through the opening of the canopy with the injection hole facing downward. At the time of steady casting, the canopy abuts on the upper surface of the injection tube to cover it, the injection flow from the ladle nozzle to the tundish is shut off from the outside, and the injection flow is sealed by the inert gas introduced inside. When sealing the inside of the injection tube with an inert gas, an inert gas introduction hole is installed in the canopy arranged at the top of the injection tube, or an inert gas introduction hole is installed on the side of the injection tube, and Ar is placed in the injection tube. Gas is ejected and supplied (see Patent Documents 1 to 5).
On the molten metal surface in the injection pipe, the injection flow from the ladle strikes an inert gas such as Ar, which is the atmosphere in the injection pipe, and many bubbles are generated in the molten steel. The generated bubbles have an effect of cleaning the molten steel by capturing non-metallic inclusions suspended in the molten steel and generating a gentle upward flow in the tundish.

一つのタンディッシュで、取鍋からの溶鋼注入が完了した後に続けて次の取鍋の溶鋼を注入し、次々に複数の取鍋の溶鋼を連続して連続鋳造する方法を連続連続鋳造（連々鋳）と呼んでいる。取鍋を交換した時点でタンディッシュ内に入っていた溶鋼を鋳造した鋳片を、取鍋交換時の鋳片、あるいは非定常鋳片と呼ぶ。非定常鋳片は、下記に示す理由により、酸化物系介在物の含有量が定常部の鋳片よりも多くなりやすい。 In one tundish, after the molten steel injection from the ladle is completed, the molten steel of the next ladle is injected, and the continuous continuous casting method of continuously casting the molten steel of multiple ladles one after another (continuously Called casting). The slab cast from the molten steel that was in the tundish when the ladle was replaced is called the slab when the ladle was replaced, or the unsteady slab. The unsteady slab is likely to have a higher content of oxide inclusions than the slab of the stationary part for the following reasons.

連々鋳において、一つの取鍋からの溶鋼注入が完了した後も、鋳片の引き抜きは定常部と同じ鋳造速度で継続するので、タンディッシュ内溶鋼量が減少し、タンディッシュ内湯面レベルが逐次低下する。次の取鍋からの溶鋼注入を迅速に開始できたときは、タンディッシュ内溶鋼湯面レベルが注入管の下端に到達する前に溶鋼注入が再開され、その後はタンディッシュ内溶鋼湯面レベルが上昇を開始する。 In continuous casting, even after the molten steel injection from one ladle is completed, the slab drawing continues at the same casting speed as the steady part, so the amount of molten steel in the tundish decreases and the level of the tundish inner surface gradually increases. descend. When the molten steel injection from the next ladle could be started quickly, the molten steel injection was resumed before the molten steel level in the tundish reached the lower end of the injection pipe, and then the molten steel level in the tundish was Start climbing.

連々鋳において、一つの取鍋の溶鋼をタンディッシュに注入し、注入が完了する時点において、取鍋底部のスライディングノズルから流出する注入流が、溶鋼から取鍋スラグに変化した時点でスライディングノズルを閉として注入を終了する。このとき、取鍋から流出した取鍋スラグは、注入管内の溶鋼表面に残留する。上述のように、タンディッシュ内溶鋼湯面レベルが注入管の下端に到達する前に次の取鍋からの溶鋼注入を開始すると、注入管内の溶鋼表面に残留した取鍋スラグが溶鋼注入流によってタンディッシュ内溶鋼中にたたき込まれる。取鍋スラグは通常、ＦｅＯやＭｎＯといった低級酸化物を多く含むので、タンディッシュ内溶鋼を汚染する源となり、当該溶鋼を鋳造した非定常鋳片の清浄性を阻害する原因となる。 In continuous casting, molten steel from one ladle is poured into the tundish, and when the pouring is completed, the sliding nozzle is turned on when the injection flow flowing out of the sliding nozzle at the bottom of the ladle changes from molten steel to ladle slag. The injection is terminated as closed. At this time, ladle slag flowing out of the ladle remains on the surface of the molten steel in the injection pipe. As described above, when the molten steel injection from the next ladle is started before the molten steel level in the tundish reaches the lower end of the injection pipe, the ladle slag remaining on the molten steel surface in the injection pipe is caused by the molten steel injection flow. It is beaten into molten steel in the tundish. Since the ladle slag usually contains a large amount of lower oxides such as FeO and MnO, the ladle slag becomes a source of contamination of the molten steel in the tundish and becomes a cause of hindering the cleanability of the unsteady slab cast from the molten steel.

次の取鍋からの溶鋼注入開始前に注入管内に残存した前の取鍋の取鍋スラグを取り除こうとすると、次の取鍋からの溶鋼注入開始を意図的に遅らせ、タンディッシュ内溶鋼湯面レベルが注入管下端位置よりも低い位置とし、注入管が非浸漬状態とすればよい。これにより、注入管内に残存していた取鍋スラグは、タンディッシュ内溶鋼表面に広がるので、注入管から排出することができる。ところが、タンディッシュ内湯面が下がると、タンディッシュ内に溶鋼が滞留する時間（溶鋼滞留時間）が短くなって、非金属介在物の浮上が阻害される問題が生じる。加えて、注入管下端が非浸漬状態となると、注入管内はタンディッシュ内雰囲気と接触することになり、注入管内はシール効果が損なわれる。この状態で次の取鍋からの溶鋼注入を再開するので、タンディッシュ内溶鋼湯面レベルが上昇して注入管下端位置よりも高くなるまでの間、取鍋からタンディシュへの溶鋼注入流は酸化性雰囲気に曝されることになる。これによりタンディッシュ内溶鋼が汚染され、当該溶鋼を鋳造した非定常鋳片の清浄性を阻害する原因となる。 If you try to remove the ladle slag from the previous ladle before the start of the molten steel injection from the next ladle, the start of the molten steel injection from the next ladle is intentionally delayed, and the molten steel surface in the tundish The level may be lower than the lower end position of the injection tube, and the injection tube may be in a non-immersed state. Thereby, since the ladle slag remaining in the injection pipe spreads on the surface of the molten steel in the tundish, it can be discharged from the injection pipe. However, when the hot water level of the tundish falls, the time that the molten steel stays in the tundish (molten steel residence time) is shortened, resulting in a problem that the floating of nonmetallic inclusions is hindered. In addition, when the lower end of the injection tube is not immersed, the inside of the injection tube comes into contact with the atmosphere in the tundish, and the sealing effect is impaired in the injection tube. Since the molten steel injection from the next ladle is resumed in this state, the molten steel injection flow from the ladle to the tundish is oxidized until the molten steel level in the tundish rises and becomes higher than the lower end position of the injection pipe. You will be exposed to a sex atmosphere. As a result, the molten steel in the tundish is contaminated and becomes a cause of impairing the cleanability of the unsteady cast slab in which the molten steel is cast.

取鍋交換時の注入中断によるタンディッシュ内湯面レベルの低下代は、鋳型サイズや鋳造速度、あるいは取鍋交換時間の影響を受けて変動する。例えば鋳型サイズや鋳造速度が大きく、かつ取鍋交換時間がかかった場合にはタンディッシュ内湯面は大きく低下する。このような場合も、やはり注入管下端が非浸漬状態となり、次の取鍋からの注入流が酸化性雰囲気にさらされるためにタンディッシュ内溶鋼が汚染され、当該溶鋼を鋳造した非定常鋳片の清浄性を阻害する原因となる。 The allowance for lowering the level of the tundish inside hot water due to the interruption of pouring at the time of changing the ladle varies depending on the mold size, casting speed, or ladle changing time. For example, when the mold size and casting speed are large and it takes a ladle exchange time, the tundish hot water level greatly decreases. Also in such a case, the lower end of the injection pipe is still in a non-immersed state, and the molten steel in the tundish is contaminated because the injection flow from the next ladle is exposed to the oxidizing atmosphere, and the unsteady cast slab in which the molten steel is cast It becomes a cause to inhibit the cleanliness of.

特開昭６２−１６８６４９号公報JP 62-168649 A 特開昭６２−８１２５３号公報JP 62-81253 A 特開平５−２９３６１４号公報JP-A-5-293614 特開平７−３０８７４１号公報JP 7-308741 A 特開平９−１５０２４２号公報Japanese Patent Laid-Open No. 9-15242

上述のとおり、連々鋳の取鍋交換時において、注入管内の溶鋼表面に前回注入の取鍋スラグが残存したままで次の取鍋溶鋼注入を開始することによる問題（以下「第１の問題」という。）と、タンディッシュ内溶鋼表面が注入管下端部よりも低下してから次の取鍋溶鋼を開始することによる問題（以下「第２の問題」という。）のいずれかが、避けて通れない問題として存在した。本発明は、第１の問題と第２の問題をいずれも解消することのできる、連続鋳造機及び連続鋳造方法を提供することを目的とする。 As described above, at the time of continuous ladle replacement, the problem caused by starting the next ladle molten steel injection while the ladle slag of the previous injection remained on the molten steel surface in the injection pipe (hereinafter referred to as “first problem”) )) And the problem of starting the next ladle molten steel after the surface of the molten steel in the tundish falls below the lower end of the injection pipe (hereinafter referred to as “second problem”). It existed as an inability to pass. An object of this invention is to provide the continuous casting machine and continuous casting method which can eliminate both the 1st problem and the 2nd problem.

即ち、本発明の要旨とするところは以下のとおりである。
（１）耐火物製の筒状体であって、内径が３００ｍｍ以上であり、鋼の連続鋳造において取鍋ノズルからの自由落下流を覆うとともに定常鋳造時において当該筒状体の下端がタンディッシュ内の溶鋼中に浸漬した位置となるもの（以下、当該筒状体を「注入管」と呼び、定常鋳造時における注入管高さを「定常鋳造時注入管高さ」と呼ぶ。）をタンディッシュに設置し、
前記注入管を、前記定常鋳造時注入管高さより高い位置から低い位置までの範囲で昇降させることのできる昇降装置を設け、
取鍋からの溶鋼注入時に注入管上部を遮蔽する天蓋を有し、天蓋中心部には取鍋ノズルを通す穴が穿たれており、
前記昇降装置が注入管受台と注入管受台を昇降させる昇降機構から成り、
注入管上端は前記注入管受台の上端よりも下にあり、かつ該注入管受台の上端は内径が８００ｍｍ以上であって注入管上端の直径よりも水平方向に拡大されており、該注入管受台の上昇または取鍋の下降によって注入管受台上端と天蓋との間を密着させられることを特徴とする、連続鋳造機。
（２）前記天蓋から前記注入管内にＡｒガスを吹き込むガス導入孔を有することを特徴とする、上記（１）に記載の連続鋳造機。 That is, the gist of the present invention is as follows.
(1) A refractory cylindrical body having an inner diameter of 300 mm or more, covering a free fall flow from the ladle nozzle in continuous casting of steel, and the lower end of the cylindrical body being tundish during steady casting (Hereinafter referred to as the “injection tube”, and the height of the injection tube during steady casting is referred to as the “injection tube height during steady casting”). Installed in the dish,
An elevating device capable of elevating and lowering the injection pipe in a range from a position higher than the injection pipe height during the steady casting to a lower position;
It has a canopy that shields the top of the injection pipe when molten steel is poured from the ladle, and a hole through which the ladle nozzle is passed is drilled in the center of the canopy .
The lifting device is composed of an injection tube cradle and a lifting mechanism that lifts and lowers the injection tube cradle,
The upper end of the injection tube is below the upper end of the injection tube cradle, and the upper end of the injection tube cradle has an inner diameter of 800 mm or more and is expanded in the horizontal direction beyond the diameter of the upper end of the injection tube. A continuous casting machine characterized in that the upper end of the injection tube cradle and the canopy can be brought into close contact with each other by raising the tube cradle or lowering the ladle .
(2) The continuous casting machine according to (1) above, further comprising a gas introduction hole for blowing Ar gas into the injection pipe from the canopy .

本発明は、タンディッシュに対する注入管高さを変化させる昇降装置を有しているので、連々鋳の取鍋交換時において、前の取鍋注入終了後に注入管を上昇させて注入管内部に残存する取鍋スラグを排出し、次の取鍋注入開始前に注入管を下降させて溶鋼への浸漬状態を保持したままで注入を開始できるので、タンディッシュ内溶鋼の汚染を防止し、当該溶鋼を鋳造した非定常鋳片の清浄性を改善することができる。 Since the present invention has an elevating device that changes the height of the injection tube relative to the tundish, when changing the ladle for continuous casting, the injection tube is raised after the previous ladle injection is completed and remains inside the injection tube The ladle slag is discharged, and before the start of the next ladle pouring, the pouring pipe can be lowered to start pouring while maintaining the immersion state in the molten steel, so that the molten steel in the tundish is prevented from being contaminated, It is possible to improve the cleanliness of the unsteady cast slab casted with No. 2.

本発明の連続鋳造機の一例を示す部分断面図である。It is a fragmentary sectional view showing an example of the continuous casting machine of the present invention. 本発明の連続鋳造機の一例を示す部分断面図である。It is a fragmentary sectional view showing an example of the continuous casting machine of the present invention. 本発明の連続鋳造機の一例を示す部分断面図である。It is a fragmentary sectional view showing an example of the continuous casting machine of the present invention. 本発明の連続鋳造機の一例を示す部分断面図である。It is a fragmentary sectional view showing an example of the continuous casting machine of the present invention. 従来の連続鋳造機の一例を示す部分断面図である。It is a fragmentary sectional view showing an example of the conventional continuous casting machine. 取鍋交換時の前後における鋳片トータル酸素量の推移を示す図である。It is a figure which shows transition of the slab total oxygen amount before and behind at the time of ladle exchange. 取鍋交換時前後の定常部と非定常部における鋳片トータル酸素量の挙動を示す図である。It is a figure which shows the behavior of the slab total oxygen amount in the stationary part and unsteady part before and after the ladle exchange.

図１〜図５に基づいて本発明の説明を行う。 The present invention will be described with reference to FIGS.

本発明は、タンディッシュ２を用いた鋼の連続鋳造において、取鍋１からタンディッシュ２に溶鋼を注入する際に、取鍋ノズル４から自由落下する注入流３３を覆う耐火物製の筒状体である注入管１１を用いる場合を対象とする。注入管１１は、ロングノズルと異なり、その内径が３００ｍｍ以上と大きな直径を有することを特徴とする。注入管は取鍋ではなくタンディッシュに設置されるので、タンディッシュに対する取鍋のセット位置がずれた時に、注入管内径が小さいと溶鋼が注入管外に飛散する懸念があることから、直径を３００ｍｍ以上としている。 In the present invention, in the continuous casting of steel using the tundish 2, when molten steel is injected from the ladle 1 into the tundish 2, the cylindrical shape made of a refractory material covers the injection flow 33 that freely falls from the ladle nozzle 4. The case where the injection tube 11 which is a body is used is targeted. Unlike the long nozzle, the injection tube 11 has a large diameter of 300 mm or more. Since the injection tube is installed in the tundish instead of the ladle, when the setting position of the ladle relative to the tundish is shifted, there is a concern that the molten steel may scatter outside the injection tube if the injection tube inner diameter is small. It is set to 300 mm or more.

注入管１１は、定常鋳造時において注入管下端２２がタンディッシュ内の溶鋼３１中に浸漬した位置となる。また、取鍋１からの溶鋼注入時に注入管上端２１の上部を遮蔽する天蓋１２を有し、天蓋中心部には取鍋ノズル４を通す穴１３が穿たれている。これにより、筒状体である注入管１１の下部は溶鋼３１に浸漬して外気から遮断され、注入管１１の上部は天蓋１２で覆われて外気から遮断される。取鍋１からの注入時において、取鍋ノズル４の先端は天蓋１２の穴１３を貫通して注入管１１の内部に溶鋼を注入することができる。このように外気と遮断された注入管１１の内部に不活性ガスを供給することにより、注入中における注入管１１の内部を不活性ガス雰囲気とすることができる。 The injection pipe 11 is located at a position where the lower end 22 of the injection pipe is immersed in the molten steel 31 in the tundish at the time of steady casting. Moreover, it has the canopy 12 which shields the upper part of the injection pipe upper end 21 at the time of the molten steel injection | pouring from the ladle 1, and the hole 13 which lets the ladle nozzle 4 pass is drilled in the canopy center part. Thereby, the lower part of the injection tube 11 which is a cylindrical body is immersed in the molten steel 31 and is cut off from the outside air, and the upper part of the injection tube 11 is covered with the canopy 12 and is cut off from the outside air. When pouring from the ladle 1, the tip of the ladle nozzle 4 can penetrate the hole 13 of the canopy 12 to inject molten steel into the pouring tube 11. By supplying the inert gas to the inside of the injection pipe 11 thus blocked from the outside air, the inside of the injection pipe 11 during the injection can be made an inert gas atmosphere.

このように注入管１１内部を不活性ガスで満たすことによって、注入管内の湯面では、取鍋１からの注入流３３が不活性ガスを叩き込んで、溶鋼中に多くの気泡が発生する。発生した気泡は、溶鋼中に懸濁する非金属介在物を捕捉するとともにタンディッシュ内に緩やかな上昇流を生じることによって溶鋼を清浄化する。 By filling the inside of the injection pipe 11 with the inert gas in this way, the injection flow 33 from the ladle 1 strikes the inert gas on the molten metal surface in the injection pipe, and many bubbles are generated in the molten steel. The generated bubbles capture nonmetallic inclusions suspended in the molten steel and clean the molten steel by generating a gentle upward flow in the tundish.

定常鋳造時におけるタンディッシュ２内溶鋼３１の湯面３２レベルは、当該タンディッシュ２の機能を発揮する上で最適なレベルが定められる。また、定常鋳造時における注入管下端２２の浸漬深さは、注入管１１の有する溶鋼清浄化作用を最大化する品質適正な浸漬深さがある。ただし、従来のように注入管１１が昇降しない機構である場合、品質適正な浸漬深さとすると、取鍋交換時の注入中断中にタンディッシュ内湯面レベルが低下して注入管下端２２が非浸漬状態となることが頻発するため、品質適正な浸漬深さよりも深い浸漬深さ（操業適正な浸漬深さ）に設定されていた。注入管浸漬深さを確保することは、無用に長い注入管を必要とし、経済的な不利益を生じることにもなる。定常鋳造時において目標とする浸漬深さを実現する注入管高さを「定常鋳造時注入管高さ」と呼ぶ。 The level of the molten metal surface 32 of the molten steel 31 in the tundish 2 at the time of steady casting is determined to be an optimum level for exhibiting the function of the tundish 2. Further, the immersion depth of the lower end 22 of the injection pipe at the time of steady casting has an appropriate immersion depth that maximizes the molten steel cleaning action of the injection pipe 11. However, when the injection pipe 11 does not move up and down as in the prior art, if the immersion depth is appropriate for quality, the level of the inner surface of the tundish falls while the injection is interrupted when the ladle is replaced and the lower end 22 of the injection pipe is not immersed Since the state frequently occurs, the immersion depth deeper than the quality appropriate immersion depth (operation appropriate immersion depth) was set. Ensuring the injection tube immersion depth requires an unnecessarily long injection tube, and also causes an economic disadvantage. The injection pipe height that achieves the target immersion depth during steady casting is referred to as “injection pipe height during steady casting”.

まず、本発明の連続鋳造機について説明する。 First, the continuous casting machine of this invention is demonstrated.

本発明の連続鋳造機は、注入管１１を、定常鋳造時注入管高さより高い位置から低い位置までの範囲で昇降させることのできる昇降装置１８を設けることを特徴とする。注入管１１を昇降装置１８で昇降させたとき、注入管１１を最も高い位置としたときの高さを注入管上限高さと呼び、注入管１１を最も低い位置としたときの高さを注入管下限高さと呼ぶ。 The continuous casting machine of the present invention is characterized in that an elevating device 18 capable of elevating and lowering the injection pipe 11 in a range from a position higher than the injection pipe height during steady casting to a lower position is provided. When the injection tube 11 is moved up and down by the lifting device 18, the height when the injection tube 11 is at the highest position is called the injection tube upper limit height, and the height when the injection tube 11 is at the lowest position is the injection tube This is called the lower limit height.

前述のように、連々鋳の取鍋交換時において、注入管内の溶鋼表面に前回注入の取鍋スラグが残存したままで次の取鍋溶鋼注入を開始すると、注入管内の溶鋼表面に残留したスラグが自由落下する注入流３３によってタンディッシュ内溶鋼３１中にたたき込まれる。取鍋スラグは通常、ＦｅＯやＭｎＯといった低級酸化物を多く含むので、タンディッシュ内溶鋼３２を汚染する源となり、当該溶鋼３２を鋳造した非定常鋳片の清浄性を阻害するという問題（第１の問題）があった。また、タンディッシュ内溶鋼表面（湯面３２）が注入管下端２２よりも低下してから次の取鍋溶鋼を開始すると、上記第１の問題は解消されるものの、注入管内が酸化性雰囲気となった状態で注入を開始するため、タンディッシュ内溶鋼３１が汚染され、当該溶鋼３１を鋳造した非定常鋳片の清浄性を阻害するという問題（第２の問題）が生じる。 As described above, when the ladle slag is continuously cast, when the next ladle molten steel injection is started while the previous ladle slag remains on the molten steel surface in the injection pipe, the slag remaining on the molten steel surface in the injection pipe Is tapped into the molten steel 31 in the tundish by the injection flow 33 that falls freely. Since ladle slag usually contains a large amount of lower oxides such as FeO and MnO, it becomes a source of contaminating the molten steel 32 in the tundish, and the problem of impairing the cleanability of the unsteady slab cast from the molten steel 32 (first) Problem). Moreover, when the next ladle molten steel is started after the molten steel surface in the tundish (the molten metal surface 32) is lower than the lower end 22 of the injection pipe, the first problem is solved, but the inside of the injection pipe has an oxidizing atmosphere. Since the injection is started in the state, the molten steel 31 in the tundish is contaminated, and there arises a problem (second problem) that impairs the cleanability of the unsteady cast slab in which the molten steel 31 is cast.

本発明においては、取鍋交換時に、前の取鍋注入が終了した後、昇降装置１８によって注入管１１を定常鋳造時注入管高さよりも上昇させ、次の取鍋注入開始前に注入管下端２２位置をタンディッシュ内湯面３２レベルよりも高くして非浸漬状態とすることにより、上記第１の問題を解決した。注入管１１が非浸漬状態となると、注入管１１の内部の溶鋼表面に蓄積していた取鍋スラグは、タンディッシュ内の湯面上を広く拡散する。その後に再度注入管１１を下降して浸漬状態に戻すと、注入管内の溶鋼表面からは取鍋スラグが排除された状態となる。この状態で次の取鍋の注入を開始することにより、上記第２の問題をも回避することができる。 In the present invention, at the time of replacing the ladle, after the previous ladle injection is completed, the elevating device 18 raises the injection pipe 11 from the height of the injection pipe during steady casting, and before the next ladle injection starts, The 22nd position was made higher than the level of the tundish hot water surface 32 to make it a non-immersion state, thereby solving the first problem. When the injection tube 11 is in a non-immersed state, the ladle slag accumulated on the molten steel surface inside the injection tube 11 diffuses widely on the hot water surface in the tundish. Thereafter, when the injection tube 11 is lowered again to return to the immersed state, the ladle slag is removed from the molten steel surface in the injection tube. By starting the injection of the next ladle in this state, the second problem can also be avoided.

前の取鍋１の注入を終了し、取鍋１を交換し、次の取鍋１の注入を開始するまでの間も、鋳型での鋳片引き抜きは継続し、タンディッシュ２から鋳型への溶鋼の供給は続くので、取鍋交換時の溶鋼注入中断中はタンディッシュ内湯面３２レベルが逐次低下する。何らかの理由で取鍋交換時の注入中断時間が長くなりすぎると、注入管高さを定常鋳造時注入管高さに維持したのでは注入管下端２２が非浸漬状態となり、前記第２の問題が生じる。 The slab drawing with the mold continues until the previous ladle 1 is poured, the ladle 1 is replaced, and the next ladle 1 is poured, and the tundish 2 is poured into the mold. Since the supply of the molten steel continues, the level of the tundish hot water surface 32 gradually decreases while the molten steel injection is interrupted when the ladle is replaced. If for some reason the injection interruption time when replacing the ladle becomes too long, if the injection pipe height is maintained at the injection pipe height during steady casting, the lower end 22 of the injection pipe becomes non-immersed, and the second problem arises. Arise.

本発明では、取鍋交換時、次の取鍋１からの溶鋼注入を開始する時点において、タンディッシュ内湯面３２レベルの低下状況に応じて、昇降装置１８によって注入管１１を定常鋳造時注入管高さよりも下降させ、注入管下端２２位置を次の取鍋注入開始時のタンディッシュ内湯面３２レベルよりも低くして浸漬状態とすることにより、上記第２の問題を解決した。注入管高さは定常鋳造時注入管高さよりも低いので、取鍋１についても、通常鋳造時の取鍋位置よりも低い位置とし、注入を開始する。次の取鍋１の注入開始後、鋳型への鋳造量よりも多い量の溶鋼を取鍋１から注入することにより、タンディッシュ内湯面３２レベルが逐次上昇するので、注入管１１についても湯面３２上昇に応じて逐次上昇する。注入管１１の上昇に伴い、取鍋１も同じ上昇速度で上昇させる。 In the present invention, at the time of starting the pouring of molten steel from the next ladle 1 when the ladle is replaced, the elevating device 18 is used to inject the injection pipe 11 by the elevating device 18 according to the state of lowering the level of the tundish hot water surface 32. The second problem was solved by lowering the height and lowering the pouring pipe lower end 22 position below the level of the tundish hot water surface 32 at the start of the next ladle pouring. Since the injection pipe height is lower than the injection pipe height during steady casting, the ladle 1 is also set to a position lower than the ladle position during normal casting, and injection is started. After the start of pouring of the next ladle 1, the level of tundish hot water surface 32 gradually rises by pouring a larger amount of molten steel from the ladle 1 than the amount cast into the mold. 32 Ascending in response to ascending. As the injection tube 11 rises, the ladle 1 is also raised at the same ascent rate.

注入管１１を上昇させることのできる最高高さである注入管上限高さについては、取鍋交換時、次の取鍋１からの注入を開始する前の段階において、注入管１１を非浸漬状態とすることのできる高さであればよい。注入管上限高さと定常鋳造時注入管高さとの差が、注入管１１の浸漬深さよりも大きければ、注入管１１を非浸漬状態とすることができる。注入管１１を下降させることのできる最低高さである注入管下限高さについては、取鍋交換時、次の取鍋１からの注入開始時に想定されるタンディッシュ内の最低湯面３２レベルにおいて、注入管１１を浸漬状態とすることのできる高さであればよい。 About the upper limit height of the injection pipe, which is the maximum height at which the injection pipe 11 can be raised, when the ladle is replaced, the injection pipe 11 is not immersed in the stage before the start of the injection from the next ladle 1 Any height can be used. If the difference between the upper limit of the injection pipe and the injection pipe height during steady casting is larger than the immersion depth of the injection pipe 11, the injection pipe 11 can be brought into a non-immersion state. Regarding the lower limit height of the injection pipe, which is the minimum height at which the injection pipe 11 can be lowered, at the level of the lowest hot water level 32 in the tundish assumed at the start of injection from the next ladle 1 when the ladle is replaced. Any height that allows the injection tube 11 to be immersed is acceptable.

注入管１１、天蓋１２、タンディッシュ内溶鋼３１で囲まれた空間には、Ａｒガスなどの不活性ガスを供給することにより、不活性ガス雰囲気とする。不活性ガスを供給するガス導入孔２０の配置位置として、天蓋１２（いわゆる陣笠部）に配置（特許文献２、３、４の従来技術）、注入管１１の途中に配置（特許文献１、２、３、４）などが開示されており、いずれの箇所にガス導入孔２０を設けても、注入管内部空間を不活性ガス雰囲気とすることができる。 An inert gas atmosphere is created by supplying an inert gas such as Ar gas to the space surrounded by the injection tube 11, the canopy 12 and the molten steel 31 in the tundish. As the arrangement position of the gas introduction hole 20 for supplying the inert gas, it is arranged on the canopy 12 (so-called Jinkasa) (prior art of Patent Documents 2, 3 and 4), and arranged in the middle of the injection pipe 11 (Patent Documents 1 and 2). 3, 4), etc., and the inner space of the injection tube can be made an inert gas atmosphere even if the gas introduction hole 20 is provided at any location.

本発明の連続鋳造機において好ましくは、天蓋１２から注入管内にＡｒガスを吹き込むガス導入孔２０を有することとする。取鍋ノズル４から溶鋼を流出させるに際し、溶鋼流は下方に流れて注入流３３を形成するのみならず、側方にも飛散することがある。取鍋ノズル４下端よりも下方にガス導入孔２０を設けると、取鍋ノズル４から飛散した溶鋼がガス導入孔２０に付着し、ガス導入孔２０が閉塞してしまうことがある。従って、ガス導入孔２０は飛散した溶鋼が付着し難い場所に設けることが好ましい。ガス導入孔２０配置位置を天蓋１２に設けることとすれば、ガス導入孔２０を、取鍋ノズル４下端と同じ高さあるいはそれよりも高い位置とすることができ、取鍋ノズル４からの飛散溶鋼の付着を防ぐことができるので、取鍋ノズル４から飛散した溶鋼が最も付着しにくいからである。 The continuous casting machine of the present invention preferably has a gas introduction hole 20 for blowing Ar gas from the canopy 12 into the injection pipe. When the molten steel is caused to flow out from the ladle nozzle 4, the molten steel flow not only flows downward to form the injection flow 33 but may also scatter to the side. If the gas introduction hole 20 is provided below the lower end of the ladle nozzle 4, the molten steel scattered from the ladle nozzle 4 may adhere to the gas introduction hole 20 and the gas introduction hole 20 may be blocked. Therefore, it is preferable to provide the gas introduction hole 20 in a place where the scattered molten steel is difficult to adhere. If the gas introduction hole 20 is arranged in the canopy 12, the gas introduction hole 20 can be set to the same height as the lower end of the ladle nozzle 4 or a position higher than that, and the scattering from the ladle nozzle 4 This is because molten steel can be prevented from adhering, and the molten steel scattered from the ladle nozzle 4 is most difficult to adhere.

また、注入管内に吹き込むＡｒガスは、取鍋ノズル４から自由落下する注入流３３がタンディッシュ内湯面３２に達する湯落ち領域に向けて吹き込むことが望ましい。天蓋１２にガス導入孔２０を設けることによって、湯落ち領域に向けた吹き込みが可能となるのである。湯落ち領域では溶鋼注入流３３と雰囲気が激しく攪拌され、雰囲気による溶鋼の汚染が生じやすい。湯落ち領域に向けてＡｒガスを吹き込むことによって、湯落ち領域の雰囲気の酸素分圧を効果的に下げることができるので、雰囲気による溶鋼の汚染を防止できる。 Further, it is desirable that the Ar gas blown into the injection pipe is blown toward the hot water dropping region where the injection flow 33 that freely falls from the ladle nozzle 4 reaches the tundish hot water surface 32. By providing the gas introduction hole 20 in the canopy 12, it is possible to blow toward the hot water dropping area. In the molten metal region, the molten steel injection flow 33 and the atmosphere are vigorously stirred, and the molten steel is easily contaminated by the atmosphere. By blowing Ar gas toward the hot water drop region, the oxygen partial pressure of the atmosphere in the hot water drop region can be effectively lowered, so that contamination of the molten steel by the atmosphere can be prevented.

注入管１１と昇降装置１８との好ましい位置関係について説明する。注入管上端２１には注入管外方に張り出した凸部１９を設ける。凸部１９は、注入管１１の円周方向全周に設けると好ましい。また、注入管受台１４を設け、注入管受台１４は注入管１１を貫通して受ける受け部１５を有し、受け部１５の内径は注入管１１の外径よりも大きく凸部１９の外径よりも小さく形成する。注入管１１を注入管受台１４の受け部１５に挿入し、受け部１５の上端が注入管１１の凸部１９と当接することにより、注入管１１が注入管受台１４に配置される。注入管受台１４とタンディッシュ蓋３との間に昇降機構１７を設け、注入管受台１４と昇降機構１７とで昇降装置１８を形成する。タンディッシュ２を静置状態としたところで、昇降機構１７を動作させて注入管受台１４を上昇させれば注入管１１を上昇させることができ、注入管受台１４を下降させれば注入管１１を下降させることができる。昇降機構１７としては、昇降ジャッキを好ましく用いることができる。 A preferred positional relationship between the injection tube 11 and the lifting device 18 will be described. The upper end 21 of the injection tube is provided with a convex portion 19 projecting outward from the injection tube. The convex portion 19 is preferably provided on the entire circumference of the injection tube 11 in the circumferential direction. Further, an injection tube pedestal 14 is provided, and the injection tube pedestal 14 has a receiving portion 15 that passes through the injection tube 11. The inner diameter of the receiving portion 15 is larger than the outer diameter of the injection tube 11, and the convex portion 19. It is formed smaller than the outer diameter. The injection tube 11 is placed in the injection tube cradle 14 by inserting the injection tube 11 into the receiving portion 15 of the injection tube pedestal 14 and the upper end of the receiving portion 15 comes into contact with the convex portion 19 of the injection tube 11. An elevating mechanism 17 is provided between the injection tube receiver 14 and the tundish lid 3, and the injection tube receiver 14 and the elevating mechanism 17 form an elevator device 18. When the tundish 2 is in a stationary state, the elevating mechanism 17 is operated to raise the injection tube pedestal 14 to raise the injection tube 11, and when the injection tube pedestal 14 is lowered, the injection tube 11 can be lowered. As the lifting mechanism 17, a lifting jack can be preferably used.

上記本発明の注入管受台１４は、図４に示すように受け部１５のみで形成することができる。この場合、天蓋１２は注入管上端２１と当接する構造となるので、注入管受台１４の上昇または取鍋１の下降によって注入管上端２１と天蓋１２との間を密着させられる。 The injection tube pedestal 14 of the present invention can be formed of only the receiving portion 15 as shown in FIG. In this case, since the canopy 12 has a structure in contact with the upper end 21 of the injection tube, the upper end 21 of the injection tube 21 and the canopy 12 can be brought into close contact with the rising of the injection tube receiving base 14 or the lowering of the ladle 1.

さらに図２、３に示すように、注入管受台１４を受け部１５よりも上方に伸張することもできる。この場合、注入管上端２１は注入管受台の上端２３よりも下にある。注入管受台１４の受台側部１６は、注入管上端２１の凸部１９よりも外方に位置することになる。溶鋼注入時には、受台側部１６の上端（注入管受台の上端２３）に天蓋１２が当接する。注入管１１と受台側部１６とで円筒状の空間を形成し、さらに注入管下端２２部が溶鋼３１に浸漬し、受台側部１６の上端に天蓋１２が当接することにより、外気と遮断された空間を形成することができる。注入管内にＡｒガスを吹き込むガス導入孔２０について、図２に示す例では受台側部１６にガス導入孔２０が設けられ、図３に示す例では天蓋１２にガス導入孔２０が設けられ、図４に示す例では注入管１１側部の上端付近にガス導入孔２０が設けられている。注入管受台１４の上昇または取鍋１の下降によって注入管受台上端と天蓋との間を密着させられる。注入管受台１４と注入管上端２１との接続部には、図２、３に示すように、注入管固定用のモルタル２８を配置すると好ましい。 Further, as shown in FIGS. 2 and 3, the injection tube cradle 14 can be extended upward from the receiving portion 15. In this case, the upper end 21 of the injection tube is below the upper end 23 of the injection tube cradle. The cradle side portion 16 of the injection tube cradle 14 is positioned outward from the convex portion 19 of the injection tube upper end 21. At the time of molten steel pouring, the canopy 12 contacts the upper end of the cradle side portion 16 (the upper end 23 of the pouring tube cradle). The injection tube 11 and the cradle side portion 16 form a cylindrical space, the lower end 22 portion of the injection tube is immersed in the molten steel 31, and the canopy 12 comes into contact with the upper end of the cradle side portion 16, thereby A blocked space can be formed. As for the gas introduction hole 20 for blowing Ar gas into the injection tube, the gas introduction hole 20 is provided in the cradle side portion 16 in the example shown in FIG. 2, and the gas introduction hole 20 is provided in the canopy 12 in the example shown in FIG. In the example shown in FIG. 4, a gas introduction hole 20 is provided near the upper end of the side portion of the injection tube 11. The upper end of the injection tube cradle and the canopy are brought into close contact with each other by raising the injection tube cradle 14 or lowering the ladle 1. As shown in FIGS. 2 and 3, a mortar 28 for fixing the injection tube is preferably disposed at the connection portion between the injection tube receiving base 14 and the injection tube upper end 21.

図１に示す例では、注入管受台１４が受台側部１６を有し、さらに受台側部１６の内径を８００ｍｍ以上に大きくしている点が特徴である。即ち、注入管受台１４の上端は内径が８００ｍｍ以上であって注入管上端２１の直径よりも水平方向に拡大されている。受台側部上端の内径が大きいので、受台側部上端に当接する天蓋１２も大きなものを用いる。 The example shown in FIG. 1 is characterized in that the injection tube cradle 14 has a cradle side 16 and the inner diameter of the cradle side 16 is increased to 800 mm or more. In other words, the upper end of the injection tube receiving base 14 has an inner diameter of 800 mm or more and is expanded in the horizontal direction more than the diameter of the injection tube upper end 21. Since the inner diameter of the upper end of the cradle side is large, a large canopy 12 that contacts the upper end of the cradle side is used.

取鍋ノズル４から流出する溶鋼は操業中に飛散することがあるので、天蓋１２が当接する部位（注入管上端２１又は注入管受台の上端２３、以下「天蓋当接部２４」という。）には飛散した溶鋼が凝固して付着し凹凸を生じやすい。通常は、天蓋当接部２４が天蓋１２に押しつけられているので飛散した溶鋼がそこに付着することはないが、取鍋１からの溶鋼注入開始時や、タンディッシュ２の高さを変更するなどの非定常操業時には、天蓋当接部２４と天蓋１２との間があくことがあり、その際に飛散した溶鋼が天蓋当接部２４に付着するのである。そのような場合に天蓋当接部２４を直接天蓋１２に押し付けても両者間を密着することができず、注入管内部の空間の気密性を高めることは難しい。一方、飛散した溶鋼が付着しない程度まで注入管１１の直径を拡大することは、無用な耐火物コスト上昇を招く。そこで図１に示すように、注入管受台１４の上端内径を８００ｍｍ以上として注入管上端の直径よりも水平方向に大きく拡大し、注入管受台の上端２３が注入管上端２１よりも上にある状態で、注入管受台上端２３と天蓋１２との間を密着させられる構造とすることによって、溶鋼飛散の影響を受けずに安定して注入管内部の空間の気密性を高めることができるのである。 Since the molten steel flowing out from the ladle nozzle 4 may scatter during operation, the portion where the canopy 12 comes into contact (the upper end 21 of the injection tube or the upper end 23 of the injection tube cradle, hereinafter referred to as the “canopy contact portion 24”). The scattered molten steel is solidified and adheres to it, and unevenness tends to occur. Usually, since the canopy abutment portion 24 is pressed against the canopy 12, the molten steel scattered does not adhere to the canopy 12, but the molten steel from the ladle 1 is started and the height of the tundish 2 is changed. During unsteady operations such as the above, there may be a gap between the canopy contact portion 24 and the canopy 12, and the molten steel scattered at that time adheres to the canopy contact portion 24. In such a case, even if the canopy contact portion 24 is pressed directly against the canopy 12, the two cannot be brought into close contact with each other, and it is difficult to improve the airtightness of the space inside the injection tube. On the other hand, enlarging the diameter of the injection tube 11 to such an extent that scattered molten steel does not adhere causes unnecessary refractory cost increase. Therefore, as shown in FIG. 1, the upper end inner diameter of the injection tube pedestal 14 is set to 800 mm or more so as to be greatly expanded in the horizontal direction than the diameter of the upper end of the injection tube. By adopting a structure in which the upper end 23 of the injection tube cradle and the canopy 12 are in close contact with each other in a certain state, the airtightness of the space inside the injection tube can be improved stably without being affected by the molten steel scattering. It is.

図１〜３にあるように、注入管受台の上端２３（天蓋当接部２４）が注入管上端２１よりも上にある位置関係の場合、図４のように注入管上端２１が天蓋当接部２４である場合と比較し、注入管１１の長さを短くすることができる。注入管１１は寿命が５〜１０チャージ程度と低寿命であるのに対し、注入管受台１４は半永久的に使用可能であるため、注入管１１の長さを短くできる本発明は耐火物コストを低減することが可能となる。 As shown in FIGS. 1 to 3, when the upper end 23 (canopy contact portion 24) of the injection tube cradle is positioned above the upper end 21 of the injection tube, the upper end 21 of the injection tube is attached to the canopy as shown in FIG. 4. Compared to the case of the contact portion 24, the length of the injection tube 11 can be shortened. The injection tube 11 has a low life of about 5 to 10 charges, whereas the injection tube pedestal 14 can be used semi-permanently, so that the length of the injection tube 11 can be shortened. Can be reduced.

以上詳述した機構を有する本発明の連続鋳造機を用いた連続鋳造方法について説明する。 A continuous casting method using the continuous casting machine of the present invention having the mechanism detailed above will be described.

連続鋳造中の取鍋交換時、取鍋１内の溶鋼をタンディッシュ２内へ注ぎ終わった時点で、注入管下端２２がタンディッシュ内湯面３２よりも上になるよう注入管１１を上昇させて、溶鋼と共に注入管１１内に流出した取鍋スラグを排出し、その後、注入管１１を前記定常鋳造時注入管高さよりも低い位置まで下降させて、取鍋交換中に下がったタンディッシュ湯面３２に注入管下端２２が浸漬した状態を保ちつつ、次の取鍋１からの溶鋼の注入を開始する。 When the ladle is replaced during continuous casting, when the molten steel in the ladle 1 is poured into the tundish 2, the pouring pipe 11 is raised so that the lower end 22 of the pouring pipe is above the hot water surface 32 of the tundish. The ladle slag that has flowed into the injection pipe 11 together with the molten steel is discharged, and then the injection pipe 11 is lowered to a position lower than the injection pipe height at the time of steady casting, and the tundish hot water surface lowered during the ladle replacement The injection of the molten steel from the next ladle 1 is started while maintaining the state where the lower end 22 of the injection tube is immersed in 32.

取鍋１内の溶鋼をタンディッシュ２内へ注ぎ終わった時点で、注入管下端２２がタンディッシュ内湯面３２よりも上になるよう上昇させ、注入管１１を非浸漬状態とすることにより、溶鋼と共に注入管内に流出した取鍋スラグを排出することができる。および、その後、注入管１１を定常鋳造時注入管高さよりも低い位置まで下降させて、取鍋交換中に下がったタンディッシュ湯面３２に注入管下端２２が浸漬した状態を保ちつつ、次の取鍋１からの溶鋼の注入を開始することは、注入管１１を用いた連続鋳造操業における改善課題である取鍋スラグの排出と次取鍋からの溶鋼注入開始時に注入管下端２２の浸漬状態を維持できない問題を、同時に解消するものである。 When pouring the molten steel in the ladle 1 into the tundish 2, the lower end 22 of the injection pipe is raised above the inner surface 32 of the tundish, and the injection pipe 11 is brought into a non-immersed state. At the same time, the ladle slag flowing into the injection pipe can be discharged. And after that, the injection pipe 11 is lowered to a position lower than the injection pipe height at the time of steady casting, and while maintaining the state where the injection pipe lower end 22 is immersed in the tundish hot water surface 32 lowered during the ladle exchange, Starting the pouring of molten steel from the ladle 1 means that the ladle slag is discharged in the continuous casting operation using the pouring pipe 11 and that the lower end 22 of the pouring pipe is immersed when starting the pouring of molten steel from the next ladle. The problem that cannot be maintained is solved at the same time.

さらに、注入管１１を定常鋳造時注入管高さよりも下降させられることは、取鍋交換に時間を要しタンディッシュ内の湯面３２レベルが低下した際にも、注入管下端２２がタンディッシュ内の溶鋼３１に浸漬した状態を維持できる利点をもたらす。注入管下端２２がタンディッシュ内の溶鋼３１に浸漬していると、次の取鍋１が準備され注入管１１の上部に天蓋１２が設置された際に、注入管１１内が閉空間となるので、Ａｒガスによる雰囲気の置換が速やかに進行し、取鍋１から注入された溶鋼の雰囲気中酸素による汚染を低減できるのである。 Furthermore, the injection pipe 11 can be lowered from the injection pipe height during steady casting because it takes time to replace the ladle and the lower end 22 of the injection pipe is tundish even when the level 32 in the tundish is lowered. The advantage which can maintain the state immersed in the inner molten steel 31 is brought about. If the lower end 22 of the injection tube is immersed in the molten steel 31 in the tundish, the inside of the injection tube 11 becomes a closed space when the next ladle 1 is prepared and the canopy 12 is installed above the injection tube 11. Therefore, the replacement of the atmosphere with Ar gas proceeds promptly, and the contamination of the molten steel injected from the ladle 1 with oxygen in the atmosphere can be reduced.

ところで注入管１１は、通常内径が３００〜８００ｍｍ、肉厚が３０〜５０ｍｍ、長さが８００〜１８００ｍｍ、断面形状が円または楕円の筒状体である。また注入管１１は、下部をタンディッシュ内の溶鋼３１に浸漬し、内部の空間を溶鋼の注入流３３が降下するので、１０００℃以上の高温にさらされる。さらにタンディッシュ内外の湯面上のスラグによる浸食を受けるので、一般的にアルミナ−グラファイトやマグネシア−グラファイト等の酸化物−黒鉛質の耐火物から構成される。 By the way, the injection tube 11 is a cylindrical body having an inner diameter of 300 to 800 mm, a wall thickness of 30 to 50 mm, a length of 800 to 1800 mm, and a cross-sectional shape of a circle or an ellipse. Further, the lower portion of the injection tube 11 is immersed in the molten steel 31 in the tundish, and the molten steel injection flow 33 descends in the inner space, so that it is exposed to a high temperature of 1000 ° C. or higher. Further, since it is eroded by slag on the surface of the hot water inside and outside the tundish, it is generally composed of an oxide-graphitic refractory such as alumina-graphite or magnesia-graphite.

注入管１１の内径は、４００ｍｍ以上とするとより好ましい。また、注入管受台１４であってその上端が注入管上端２１よりも上方にあるものを有する本発明において、注入管受台１４の上端の内径を８００ｍｍ以上とすることにより、天蓋１２と接触する天蓋当接部２４である注入管受台上端への溶鋼飛沫付着を有効に防止することができるので、注入管内径を徒に大きくする必要がなくなり、注入管１１の内径を７００ｍｍ以下とすることができる。 The inner diameter of the injection tube 11 is more preferably 400 mm or more. Further, in the present invention having the injection tube pedestal 14 whose upper end is above the injection tube upper end 21, the inner diameter of the upper end of the injection tube pedestal 14 is set to 800 mm or more so that it contacts the canopy 12. Therefore, it is possible to effectively prevent the molten steel droplets from adhering to the upper end of the injection tube cradle, which is the canopy contact portion 24, so that it is not necessary to increase the inner diameter of the injection tube and the inner diameter of the injection tube 11 is set to 700 mm or less. be able to.

垂直曲げ型のスラブ連続鋳造機を用いて本発明を実施した。表１に化学組成範囲を示す低炭素アルミキルド鋼を毎分４〜６ｔｏｎの注入速度で取鍋１からタンディッシュ２へ注ぐ連続鋳造を取鍋６杯分行った。鋳型厚みは２５０ｍｍ、鋳型幅は１６００ｍｍ〜１２００ｍｍの範囲であった。タンディッシュ２の容量は３５ｔｏｎ、取鍋１杯の容量は２５０ｔｏｎである。タンディッシュ内溶鋼中に浸漬する注入管１１を用いて溶鋼を注入するに際し、品質適正な浸漬深さは２００ｍｍであることがわかっている。 The present invention was implemented using a vertical bending type slab continuous casting machine. The continuous casting of the low-carbon aluminum killed steel having a chemical composition range shown in Table 1 from the ladle 1 to the tundish 2 at an injection rate of 4 to 6 tons per minute was performed for 6 cups. The mold thickness was 250 mm, and the mold width was in the range of 1600 mm to 1200 mm. The capacity of the tundish 2 is 35 ton, and the capacity of one ladle is 250 ton. When injecting molten steel using the injection tube 11 immersed in the molten steel in the tundish, it is known that the immersion depth suitable for quality is 200 mm.

実施例Ａとして図１に示す本発明を用いた場合、実施例Ｂとして図２に示す本発明を用いた場合、実施例Ｃとして図３に示す本発明を用いた場合、比較例Ｄとして図５に示す例を用いた場合について鋳造を行った。 When the present invention shown in FIG. 1 is used as Example A, when the present invention shown in FIG. 2 is used as Example B, when the present invention shown in FIG. Casting was performed using the example shown in FIG.

実施例Ａ（図１）の連続鋳造機は、注入管受台１４に乗った注入管１１を昇降させる昇降機構１７として昇降ジャッキを有し、注入管１１が定常鋳造時注入管高さから３００ｍｍの上昇ならびに３００ｍｍの下降が可能である。取鍋１のスライディングゲート金物５の下部には防熱板を兼ねた直径１２００ｍｍの天蓋１２が設けられ、天蓋１２中心の穴１３からは取鍋ノズル４が出ている。天蓋１２は鋼製フレームの下部に耐火物層２７であるＭｇＯ製の断熱ボードを貼り付けて成る。注入管１１は内径が５５０ｍｍ、定常鋳造時注入管高さにおいて浸漬深さが２００ｍｍとなる。 The continuous casting machine of Example A (FIG. 1) has a lifting jack as a lifting mechanism 17 that lifts and lowers the injection pipe 11 on the injection pipe pedestal 14, and the injection pipe 11 is 300 mm from the height of the injection pipe during steady casting. As well as a 300 mm drop. A canopy 12 having a diameter of 1200 mm, which also serves as a heat insulating plate, is provided below the sliding gate hardware 5 of the ladle 1, and a ladle nozzle 4 protrudes from a hole 13 at the center of the canopy 12. The canopy 12 is formed by sticking a heat insulating board made of MgO as the refractory layer 27 to the lower part of the steel frame. The injection tube 11 has an inner diameter of 550 mm and an immersion depth of 200 mm at the height of the injection tube during steady casting.

注入管受台１４は受け部１５と受台側部１６とを有し、注入管受台１４の上端は注入管上端２１よりも２００ｍｍ上にあり、かつ注入管受台の上端２３は、注入管上端２１の直径よりも水平方向に大きく拡大され、外径：１１００ｍｍ、内径：１０００ｍｍを有している。注入管受台１４の上昇または取鍋１の下降によって注入管受台の上端２３と天蓋１２とを密着させることができる。注入管受台１４は鋼製であり、天蓋１２と密着させる上端部にはパッキン２６としてステンレス鋼製のメタルパッキンを配置している。天蓋１２の外周部もステンレス鋼製であり、注入管受台１４と天蓋１２外周部とは平滑な金属面同士が密着して気密性を確保する構造である。 The injection tube cradle 14 has a receiving portion 15 and a cradle side portion 16, the upper end of the injection tube pedestal 14 is 200 mm above the upper end 21 of the injection tube, and the upper end 23 of the injection tube cradle 14 It is enlarged in the horizontal direction larger than the diameter of the pipe upper end 21 and has an outer diameter of 1100 mm and an inner diameter of 1000 mm. The upper end 23 of the injection tube holder and the canopy 12 can be brought into close contact with each other by raising the injection tube holder 14 or lowering the ladle 1. The injection tube pedestal 14 is made of steel, and a stainless steel metal packing is disposed as a packing 26 at the upper end portion to be in close contact with the canopy 12. The outer peripheral part of the canopy 12 is also made of stainless steel, and the injection tube pedestal 14 and the outer peripheral part of the canopy 12 have a structure in which smooth metal surfaces are in close contact to ensure airtightness.

天蓋１２の中心から２００ｍｍ離れた２ヶ所には注入管内にＡｒガスを吹き込むガス導入孔２０があり、それぞれＡｒ配管に繋がっている。 There are gas introduction holes 20 for blowing Ar gas into the injection pipe at two locations 200 mm away from the center of the canopy 12, and each is connected to the Ar pipe.

実施例Ｂ（図２）の連続鋳造機は、注入管受台１４に乗った注入管１１を昇降させる昇降機構１７として昇降ジャッキを有し、注入管１１が定常鋳造時注入管高さから３００ｍｍの上昇ならびに４００ｍｍの下降が可能である。取鍋ノズル４には直径８００ｍｍの天蓋１２が直接取り付けられている。天蓋１２は鋼製フレームの内部に耐火物層２７としてハイアルミナキャスタブル耐火物を流し込んだ構造である。注入管１１は内径が４００ｍｍ、定常鋳造時注入管高さにおいて浸漬深さが２００ｍｍとなる。 The continuous casting machine of Example B (FIG. 2) has a lifting jack as a lifting mechanism 17 that lifts and lowers the injection pipe 11 on the injection pipe pedestal 14, and the injection pipe 11 is 300 mm from the height of the injection pipe during steady casting. As well as 400 mm can be lowered. A canopy 12 having a diameter of 800 mm is directly attached to the ladle nozzle 4. The canopy 12 has a structure in which a high alumina castable refractory is poured as a refractory layer 27 into a steel frame. The injection tube 11 has an inner diameter of 400 mm and an immersion depth of 200 mm at the height of the injection tube during steady casting.

注入管受台１４の上端は注入管上端２１よりも３００ｍｍ上にあり、かつ注入管受台１４の上端は、注入管上端２１の直径よりも水平方向に拡大され、外径：８００ｍｍ、内径：７００ｍｍを有している。注入管受台１４の上昇または取鍋１の下降によって注入管受台の上端２３と天蓋１２とを密着させることができる。注入管受台１４はハイアルミナ耐火物製であり、天蓋１２と密着させる上端部にはパッキン２６としてＡｌ₂Ｏ₃−ＳｉＯ₂製の円環シート状パッキンを乗せている。 The upper end of the injection tube pedestal 14 is 300 mm above the injection tube upper end 21, and the upper end of the injection tube pedestal 14 is expanded in the horizontal direction more than the diameter of the injection tube upper end 21, and has an outer diameter of 800 mm and an inner diameter: 700mm. The upper end 23 of the injection tube holder and the canopy 12 can be brought into close contact with each other by raising the injection tube holder 14 or lowering the ladle 1. The injection tube pedestal 14 is made of a high alumina refractory, and an annular sheet-like packing made of Al ₂ O ₃ —SiO ₂ is placed as a packing 26 on the upper end portion to be in close contact with the canopy 12.

注入管１１内へのＡｒガスの吹き込みは、注入管受台１４の受台側部１６の周囲４ヶ所からガス導入孔２０を通して行う。これらのガス導入孔２０は、耐熱ホースを介してＡｒ配管に繋がっている。 Ar gas is blown into the injection pipe 11 from four locations around the receiving side 16 of the injection pipe receiving base 14 through the gas introduction holes 20. These gas introduction holes 20 are connected to the Ar pipe via a heat-resistant hose.

実施例Ｃ（図３）の連続鋳造機は、注入管受台１４に乗った注入管１１を昇降させる昇降機構１７として把持装置を有し、注入管１１が定常鋳造時注入管高さから２５０ｍｍの上昇ならびに３００ｍｍの下降が可能である。取鍋ノズル４には直径８００ｍｍの天蓋１２が直接取り付けられている。天蓋１２は鋼製フレームの内部に耐火物層２７としてハイアルミナキャスタブル耐火物を流し込んだ構造である。注入管１１は内径が４００ｍｍ、定常鋳造時注入管高さにおいて浸漬深さが２００ｍｍとなる。 The continuous casting machine of Example C (FIG. 3) has a gripping device as an elevating mechanism 17 for raising and lowering the injection pipe 11 on the injection pipe cradle 14, and the injection pipe 11 is 250 mm from the height of the injection pipe during steady casting. As well as a 300 mm drop. A canopy 12 having a diameter of 800 mm is directly attached to the ladle nozzle 4. The canopy 12 has a structure in which a high alumina castable refractory is poured as a refractory layer 27 into a steel frame. The injection tube 11 has an inner diameter of 400 mm and an immersion depth of 200 mm at the height of the injection tube during steady casting.

注入管受台１４の上端は注入管上端２１よりも２５０ｍｍ上にあり、かつ注入管受台１４の上端は、注入管上端２１の直径よりも水平方向に拡大され、外径：８００ｍｍ、内径：７００ｍｍを有している。注入管受台１４の上昇または取鍋１の下降によって注入管受台の上端２３と天蓋１２とを密着させることができる。注入管受台１４はハイアルミナ耐火物製であり、天蓋１２と密着させる上端部にはパッキン２６としてＡｌ₂Ｏ₃−ＳｉＯ₂製の円環シート状パッキンを乗せている。 The upper end of the injection tube pedestal 14 is 250 mm above the injection tube upper end 21, and the upper end of the injection tube pedestal 14 is expanded in the horizontal direction more than the diameter of the injection tube upper end 21, outer diameter: 800 mm, inner diameter: 700mm. The upper end 23 of the injection tube holder and the canopy 12 can be brought into close contact with each other by raising the injection tube holder 14 or lowering the ladle 1. The injection tube pedestal 14 is made of a high alumina refractory, and an annular sheet-like packing made of Al ₂ O ₃ —SiO ₂ is placed as a packing 26 on the upper end portion to be in close contact with the canopy 12.

天蓋１２の中心から２００ｍｍ離れた２ヶ所には注入管１１内にＡｒガスを吹き込むガス導入孔２０があり、それぞれＡｒ配管に繋がっている。 There are gas introduction holes 20 for blowing Ar gas into the injection pipe 11 at two locations 200 mm away from the center of the canopy 12, and each is connected to the Ar pipe.

比較例Ｄ（図５）の連続鋳造機は、注入管１１をタンディッシュ蓋３上の固定受台２５に直接置いた構成であり注入管１１は昇降しない。取鍋ノズル４には直径８００ｍｍの天蓋１２が取り付けられている。天蓋１２は鋼製フレームの内部に耐火物層２７としてハイアルミナキャスタブル耐火物を流し込んだ構造である。 The continuous casting machine of Comparative Example D (FIG. 5) has a configuration in which the injection tube 11 is placed directly on the fixed cradle 25 on the tundish lid 3, and the injection tube 11 does not move up and down. A canopy 12 having a diameter of 800 mm is attached to the ladle nozzle 4. The canopy 12 has a structure in which a high alumina castable refractory is poured as a refractory layer 27 into a steel frame.

注入管１１は、外径：８００ｍｍ、内径：７２０ｍｍを有し、その上端の天蓋１２を密着させる部分にはパッキン２６としてＡｌ₂Ｏ₃−ＳｉＯ₂製の円環シート状パッキンを乗せている。比較例Ｄにおいては、天蓋１２と当接する天蓋当接部２４が注入管上端２１であるため、取鍋ノズル４から天蓋当接部２４への溶鋼スプラッシュを少しでも防止する目的で、注入管１１の内径として７２０ｍｍを採用した。また、定常鋳造時注入管高さにおいて浸漬深さが３００ｍｍとなる。前述のとおり、品質適正な浸漬深さは２００ｍｍであるが、比較例Ｄでは注入管１１が昇降しないので、取鍋交換時にタンディッシュ内湯面３２レベルが下降したときの注入管非浸漬を極力防止するため、浸漬深さを３００ｍｍとしたものである。 The injection tube 11 has an outer diameter of 800 mm and an inner diameter of 720 mm, and an annular sheet-like packing made of Al ₂ O ₃ —SiO ₂ is placed as a packing 26 on a portion where the top canopy 12 is in close contact. In Comparative Example D, the canopy abutment portion 24 that abuts the canopy 12 is the upper end 21 of the injection tube, and therefore the injection tube 11 is used for the purpose of preventing any molten steel splash from the ladle nozzle 4 to the canopy contact portion 24. The inner diameter of 720 mm was adopted. In addition, the immersion depth is 300 mm at the height of the injection pipe during steady casting. As described above, the immersion depth suitable for quality is 200 mm. However, in Comparative Example D, the injection tube 11 does not move up and down, so that non-immersion of the injection tube when the level of the tundish hot water surface 32 is lowered when replacing the ladle is minimized. Therefore, the immersion depth is set to 300 mm.

注入管１１の上部にはＡｒガスを吹き込むガス導入孔２０があり、それぞれＡｒ配管に繋がっている。 A gas introduction hole 20 for blowing Ar gas is provided in the upper part of the injection pipe 11 and is connected to an Ar pipe.

以上準備した実施例Ａ〜Ｃ、比較例Ｄの連続鋳造機を用い、連続鋳造を行った。前記表１に化学組成範囲を示す低炭素アルミキルド鋼を毎分４〜６ｔｏｎの注入速度で取鍋１からタンディッシュ２へ注ぐ連続鋳造を、連々鋳で取鍋６杯分行った。途中５回の取鍋交換作業において、注入中断時間については、５回のうちの３回は３分間を要し、残りの２回は作業遅れが生じたために５分間を要した。次の取鍋注入開始時におけるタンディッシュ内湯面３２レベルは、注入中断時間が３分間の場合には定常時に比較して２２０ｍｍ下降しており、注入中断時間が５分間の場合には定常時に比較して３７０ｍｍ下降していた。定常鋳造時は注入管１１の下部２００ｍｍ（実施例Ａ〜Ｃ）もしくは３００ｍｍ（比較例Ｄ）が溶鋼３２に浸漬していた。それぞれのガス導入孔２０からは５００ＮＬ／ｍｉｎのＡｒを注入管内の空間に吹き込みながら鋳造を行った。 Continuous casting was performed using the prepared continuous casting machines of Examples A to C and Comparative Example D. Continuous casting, in which low carbon aluminum killed steel having a chemical composition range shown in Table 1 is poured from the ladle 1 to the tundish 2 at an injection rate of 4 to 6 tons per minute, was performed continuously for 6 cups of the ladle. In the ladle changing operation 5 times, 3 times out of 5 times required 3 minutes, and the remaining 2 times required 5 minutes because the work was delayed. The tundish hot water level 32 at the start of the next ladle pouring is lowered by 220 mm compared with the steady state when the pouring interruption time is 3 minutes, and compared with the steady state when the pouring interruption time is 5 minutes. It was lowered 370 mm. At the time of steady casting, the lower part 200 mm (Examples A to C) or 300 mm (Comparative Example D) of the injection tube 11 was immersed in the molten steel 32. Casting was performed while blowing 500 NL / min Ar into the space in the injection pipe from each gas introduction hole 20.

取鍋１内の溶鋼を注ぎ終える際に、毎回約１０ｋｇの取鍋スラグが注入管１１内に流出した。実施例Ａ〜Ｃについては、取鍋交換中に注入管１１を定常鋳造時注入管高さに対して２５０ｍｍ上昇して注入管下端２２を非浸漬状態とし、注入管内に残存していた取鍋スラグを排出した。その後、注入管１１を定常鋳造時注入管高さに対して３００ｍｍ下げて溶鋼３１中に注入管下端２２が浸漬した状態で、次の取鍋１からの溶鋼注入を開始した。溶鋼注入開始後、タンディッシュ内湯面高さが定常高さに達した時点で、注入管１１および取鍋１を定常高さに戻した。比較例Ｄについては注入管１１が固定であるため、注入中断時間が３分の場合には次の取鍋注入開始まで注入管１１の浸漬が保たれて取鍋スラグが注入管内の溶鋼表面上に残存し、その取鍋スラグは次取鍋１からの溶鋼流に叩き込まれて注入管外に流出した。また、取鍋交換時の注入中断時間が５分の場合には、注入管下端２２の溶鋼３１中への浸漬状態が維持できずに、注入管下端２２を浸漬しない状態で次取鍋からの注入を開始することとなった。 When pouring the molten steel in the ladle 1, about 10 kg of ladle slag flowed into the injection pipe 11 each time. For Examples A to C, the ladle that had remained in the pouring tube was changed by raising the pouring tube 11 by 250 mm with respect to the pouring tube height during steady casting while the ladle was replaced and the lower end 22 of the pouring tube was not immersed. Slag was discharged. Thereafter, the injection of molten steel from the next ladle 1 was started in a state where the injection tube 11 was lowered by 300 mm with respect to the height of the injection tube during steady casting and the lower end 22 of the injection tube was immersed in the molten steel 31. After the start of molten steel injection, when the tundish hot water level reached a steady height, the injection pipe 11 and the ladle 1 were returned to the steady height. In Comparative Example D, since the injection tube 11 is fixed, when the injection interruption time is 3 minutes, the immersion of the injection tube 11 is maintained until the start of the next ladle injection, and the ladle slag is on the surface of the molten steel in the injection tube. The ladle slag was driven into the molten steel flow from the next ladle 1 and flowed out of the injection pipe. Moreover, when the injection interruption time at the time of ladle replacement | exchange is 5 minutes, the immersion state in the molten steel 31 of the injection pipe lower end 22 cannot be maintained, and it is from the next ladle in the state which does not immerse the injection pipe lower end 22 The injection was started.

それぞれの鋳造において、鋳片の１／２幅および両側１／４幅（幅方向３ヶ所）のそれぞれにおいて厚み方向を８等分した各部位から分析用試料を切り出し、非金属介在物濃度をトータル酸素分析法で評価した。評価には、幅方向３ヶ所×厚み方向８ヶ所の計２４ヶ所の分析値の平均値を用いた。 In each casting, a sample for analysis was cut out from each part of which the thickness direction was divided into 8 parts at each of the ½ width of the slab and ¼ width on both sides (three places in the width direction), and the total concentration of nonmetallic inclusions was totaled Oxygen analysis was used for evaluation. For the evaluation, the average value of the analysis values of a total of 24 places of 3 places in the width direction × 8 places in the thickness direction was used.

図６にはそれぞれの鋳造における鋳片のトータル酸素分析値を、取鍋交換からの溶鋼注入量に対して示す。図６中には各鋳造チャンスに５回ある取鍋交換前後のデータを重ねて表示している。図６の結果には多少のばらつきがあるものの、本発明の請求項１，２および３を満たす実施例Ａの場合に、最も低く、比較例Ｄの場合に最も高くなった。請求項１を満たす実施例Ｂや請求項１および２を満たす実施例Ｃの結果は、両者の中間であった。実施例Ｂにおいてはガス導入孔２０が天蓋１２ではなく受台側部１６に位置しているため、鋳造の進行に伴ってＡｒガス導入孔２０に飛散した溶鋼が凝固して徐々に付着し、注入管内のＡｒ気流が乱れて、注入流３３がタンディッシュ内湯面に到達する湯落ち領域の酸素分圧を効果的に下げることができなかったので、雰囲気による溶鋼の汚染が増えたのである。また、天蓋当接部２４の直径が８００ｍｍ未満である実施例Ｂ、Ｃにおいては、鋳造の進行に伴って取鍋ノズル４から横方向に飛散した溶鋼が凝固して、注入管受台上端の天蓋当接部２４に徐々に付着し、注入管受台上端と天蓋１２との密着が悪化して、雰囲気中酸素による溶鋼の汚染が増えたのである。 In FIG. 6, the total oxygen analysis value of the slab in each casting is shown with respect to the molten steel injection amount from ladle exchange. In FIG. 6, the data before and after the ladle change, which is five times at each casting chance, are superimposed and displayed. Although there are some variations in the results of FIG. 6, the results are the lowest in Example A satisfying Claims 1, 2 and 3 of the present invention, and the highest in Comparative Example D. The results of Example B satisfying claim 1 and Example C satisfying claims 1 and 2 were intermediate between the two. In Example B, since the gas introduction hole 20 is located not on the canopy 12 but on the cradle side portion 16, the molten steel scattered in the Ar gas introduction hole 20 as the casting progresses solidifies and gradually adheres, Since the Ar air flow in the injection pipe was disturbed, and the oxygen partial pressure in the hot water dropping area where the injection flow 33 reached the tundish hot water surface could not be effectively reduced, the contamination of the molten steel by the atmosphere increased. Further, in Examples B and C in which the diameter of the canopy contact part 24 is less than 800 mm, the molten steel splashed in the lateral direction from the ladle nozzle 4 as the casting progresses solidifies, and the upper end of the injection tube cradle is solidified. It gradually adhered to the canopy contact part 24, and the adhesion between the upper end of the injection tube cradle and the canopy 12 deteriorated, and contamination of molten steel due to oxygen in the atmosphere increased.

図６に表れた本発明の効果についてさらに詳しく説明する。取鍋交換時前後には取鍋スラグの混入や取鍋交換中に注入管内に大気が流入する影響で、溶鋼中の非金属介在物が増加し、鋳片のトータル酸素分析値が上昇する。ところが、注入管１１の上昇によって注入管内スラグの排出を促進し、加えて注入管１１の下降によって注入管下端２２が溶鋼３１に浸漬した状態で次取鍋１からの溶鋼注入を開始できた本発明の各実施例においては、取鍋スラグによる汚染と雰囲気中酸素による汚染が共に抑制されたので、取鍋交換後のトータル酸素分析値の上昇が軽微に抑制できた。 The effect of the present invention shown in FIG. 6 will be described in more detail. Before and after the ladle exchange, due to the influence of ladle slag mixing and the atmosphere flowing into the injection pipe during the ladle exchange, non-metallic inclusions in the molten steel increase and the total oxygen analysis value of the slab rises. However, the rise of the injection pipe 11 promotes the discharge of the slag in the injection pipe. In addition, the injection of the molten steel from the next ladle 1 can be started while the lower end 22 of the injection pipe is immersed in the molten steel 31 by the lowering of the injection pipe 11. In each example of the invention, both the contamination by the ladle slag and the contamination by oxygen in the atmosphere were suppressed, so that the increase in the total oxygen analysis value after the ladle replacement could be slightly suppressed.

また、本発明の実施例は、定常操業時にも、注入管内への外気浸入抑制や、取鍋注入流がタンディッシュ内湯面に到達する湯落ち領域の酸素分圧低下に有利なので、注入管内における溶鋼汚染が低減され、定常操業中の鋳片トータル酸素分析値も低下した。 In addition, the embodiment of the present invention is advantageous for suppressing the intrusion of outside air into the injection pipe and for reducing the oxygen partial pressure in the hot water falling area where the ladle injection flow reaches the tundish hot water surface even during steady operation. Molten steel contamination was reduced, and the slab total oxygen analysis value during steady operation was also reduced.

図６において、Ｘ軸すなわち取鍋交換からの溶鋼注入量が−５０ｔｏｎ〜−２０ｔｏｎの間および＋３０ｔｏｎ〜＋５０ｔｏｎの間を定常部、０ｔｏｎ〜＋２０ｔｏｎの間を非定常部と定義し、それぞれの領域における鋳片トータル酸素分析値を平均して図７に比較して示す。上述したように、定常部・非定常部にかかわらず、請求項１，２および３を満たす実施例Ａが最も優れており、比較例Ｄが最も劣る。本発明の一部の請求項を満たす実施例ＢおよびＣの結果は、両者の中間であることが、平均値からも伺える。 In FIG. 6, the molten steel injection amount from the X axis, that is, the ladle exchange, is defined as a stationary part between -50 ton and -20 ton and between +30 ton and +50 ton, and an unsteady part between 0 ton and +20 ton, and in each region The slab total oxygen analysis values are averaged and shown in comparison with FIG. As described above, the example A that satisfies claims 1, 2 and 3 is the most excellent, and the comparative example D is the most inferior, regardless of the stationary part / unsteady part. It can also be seen from the average that the results of Examples B and C satisfying some claims of the present invention are intermediate between the two.

図７で非定常部の成績比較に着目すると、実施例Ａの改善効果が優れている。実施例Ａは、注入管受台上端の天蓋当接部２４の直径が大きく、天蓋当接部２４への飛沫付着が少ないので天蓋１２との密閉性が保持される。そのため、取鍋交換時に次の取鍋１を配置して天蓋１２を当接した後、Ａｒガス吹き込みによって迅速に注入管内部空間がＡｒガスで置換されるため、非定常部の鋳片品質が特に向上したものと推測される。 Focusing on the comparison of the results of the unsteady part in FIG. 7, the improvement effect of Example A is excellent. In Example A, since the diameter of the canopy contact portion 24 at the upper end of the injection tube cradle is large and the amount of droplets adhering to the canopy contact portion 24 is small, the sealing performance with the canopy 12 is maintained. Therefore, after placing the next ladle 1 at the time of ladle replacement and contacting the canopy 12, the inner space of the injection pipe is quickly replaced with Ar gas by Ar gas blowing, so the slab quality of the unsteady part is It is speculated that this is particularly improved.

実施例Ａ〜Ｃは、定常鋳造時の注入管浸漬深さが２００ｍｍであり、品質適正な浸漬深さに合致している。それに対して比較例Ｄは、取鍋交換時の注入管非浸漬を極力回避させるために定常鋳造時の注入管浸漬深さを３００ｍｍとしている。この点からも、本発明を用いたときの品質向上効果が期待できる。また本発明は、浸漬深さを浅くする分だけ注入管の長さを短くできるので、注入管製造コストを低減する効果もある。また本発明は、昇降装置を設けることによって、タンディッシュ内湯面高さが変動しても、注入管下端の浸漬深さを適正に維持できる点でも、有利である。 In Examples A to C, the immersion tube immersion depth at the time of steady casting is 200 mm, which is consistent with the quality appropriate immersion depth. On the other hand, in Comparative Example D, the immersion tube immersion depth during steady casting is set to 300 mm in order to avoid as much as possible the injection tube non-immersion during ladle replacement. Also from this point, the quality improvement effect when using the present invention can be expected. In addition, the present invention can shorten the length of the injection tube by the amount that the immersion depth is reduced, and thus has an effect of reducing the manufacturing cost of the injection tube. In addition, the present invention is advantageous in that, by providing the lifting device, the immersion depth at the lower end of the injection pipe can be properly maintained even if the hot water level of the tundish varies.

１取鍋
２タンディッシュ
３タンディッシュ蓋
４取鍋ノズル
５取鍋スライディングゲート金物
１１注入管
１２天蓋
１３穴
１４注入管受台
１５受け部
１６受台側部
１７昇降機構
１８昇降装置
１９凸部
２０ガス導入孔
２１注入管上端
２２注入管下端
２３注入管受台の上端
２４天蓋当接部
２５固定受台
２６パッキン
２７耐火物層
２８モルタル
３１溶鋼
３２湯面
３３注入流 DESCRIPTION OF SYMBOLS 1 Ladle 2 Tundish 3 Tundish lid 4 Ladle nozzle 5 Ladle sliding gate hardware 11 Injection pipe 12 Canopy 13 Hole 14 Injection pipe receiving stand 15 Receiving part 16 Receiving side part 17 Elevating mechanism 18 Elevating apparatus 19 Convex part 20 Gas inlet hole 21 Injection pipe upper end 22 Injection pipe lower end 23 Injection pipe cradle upper end 24 Canopy contact part 25 Fixed cradle 26 Packing 27 Refractory layer 28 Mortar 31 Molten steel 32 Hot water surface 33 Injection flow

Claims

A refractory cylindrical body having an inner diameter of 300 mm or more, covering a free fall flow from the ladle nozzle in continuous casting of steel, and the lower end of the cylindrical body in molten steel in the tundish during steady casting Installed in the tundish (hereinafter referred to as the “injection pipe”, the height of the injection pipe at the time of steady casting is called the “injection pipe height at the time of steady casting”) that becomes the position immersed in the inside And
An elevating device capable of elevating and lowering the injection pipe in a range from a position higher than the injection pipe height during the steady casting to a lower position;
It has a canopy that shields the top of the injection pipe when molten steel is poured from the ladle, and a hole through which the ladle nozzle is passed is drilled in the center of the canopy .
The lifting device is composed of an injection tube cradle and a lifting mechanism that lifts and lowers the injection tube cradle,
The upper end of the injection tube is below the upper end of the injection tube cradle, and the upper end of the injection tube cradle has an inner diameter of 800 mm or more and is expanded in the horizontal direction beyond the diameter of the upper end of the injection tube. A continuous casting machine characterized in that the upper end of the injection tube cradle and the canopy can be brought into close contact with each other by raising the tube cradle or lowering the ladle .

The continuous casting machine according to claim 1, further comprising a gas introduction hole for blowing Ar gas into the injection pipe from the canopy.