JP4725244B2 - Ladle for continuous casting and method for producing slab - Google Patents
Ladle for continuous casting and method for producing slab Download PDFInfo
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本発明は、鋼の連続鋳造工程において連続鋳造される溶鋼を収容するために使用される取鍋、並びに、この取鍋を使用した鋳片の製造方法に関し、詳しくは、取鍋内に存在するスラグのタンディッシュへの流出を防止して鋳片の品質を向上させるとともに、溶鋼歩留まりを向上させることのできる取鍋、並びに、この取鍋を使用した鋳片の製造方法に関するものである。 TECHNICAL FIELD The present invention relates to a ladle used for containing molten steel continuously cast in a continuous casting process of steel, and a method for producing a slab using the ladle. The present invention relates to a ladle capable of preventing the outflow of slag to a tundish to improve the quality of a slab and improving the yield of molten steel, and a slab manufacturing method using the ladle.
鋼の連続鋳造においては、通常、取鍋内の溶鋼を一旦タンディッシュに注入し、タンディッシュ内に所定量の溶鋼が滞在した状態で、タンディッシュ内の溶鋼を鋳型に注入している。取鍋内の溶鋼がなくなった場合には、空の取鍋を別のヒートの溶鋼が収容された取鍋と交換して連続連続鋳造（以下、「連々鋳」と記す）が行われている。取鍋を交換せずに１ヒートのみで連続鋳造する場合もあるが、通常、連続鋳造機における生産性の向上、それによる製造コストの削減などの目的のために、複数ヒートの連々鋳が広く行われている。尚、取鍋にはその底部に溶鋼流出孔が設置されており、取鍋内の溶鋼はこの溶鋼流出孔を通ってタンディッシュに注入されている。 In continuous casting of steel, the molten steel in the ladle is usually once poured into the tundish, and the molten steel in the tundish is poured into the mold while a predetermined amount of molten steel stays in the tundish. When the molten steel in the ladle runs out, continuous empty casting (hereinafter referred to as “continuous casting”) is performed by replacing the empty ladle with a ladle containing molten steel of another heat. . In some cases, continuous casting with only one heat is possible without changing the ladle. Usually, continuous casting with multiple heats is widely used for the purpose of improving productivity in continuous casting machines and thereby reducing manufacturing costs. Has been done. The ladle is provided with a molten steel outflow hole at the bottom thereof, and the molten steel in the ladle is poured into the tundish through the molten steel outflow hole.
この連続鋳造工程においては、取鍋交換時の非定常部鋳片の品質が定常鋳造域の鋳片に比べて低下するという問題がある。これは、取鍋交換時、取鍋内に収容される溶鋼が少なくなった時点で、主に取鍋内の溶鋼の上部に存在するスラグが、取鍋内の溶鋼湯面位置の低下によって形成される溶鋼の渦流に巻き込まれるなどして溶鋼とともにタンディッシュ内に流出し、更にタンディッシュから鋳型内に注入されて鋳片に捕捉されるからである。取鍋交換時には、溶鋼量が減少することにより溶鋼温度が低下し、溶鋼中に懸濁したスラグが溶鋼から浮上分離し難くなることも鋳片の品質低下を助長させる要因となっている。 In this continuous casting process, there is a problem in that the quality of the unsteady portion slab when the ladle is replaced is lower than that of the slab in the steady casting region. This is because when the molten steel contained in the ladle is reduced when the ladle is replaced, the slag that exists mainly on the upper part of the molten steel in the ladle is formed due to a decrease in the position of the molten steel surface in the ladle. This is because the steel flows out into the tundish together with the molten steel by being caught in the vortex of the molten steel, and is further injected from the tundish into the mold and captured by the slab. When the ladle is replaced, the molten steel temperature decreases due to a decrease in the amount of molten steel, and it is difficult for the slag suspended in the molten steel to float and separate from the molten steel.
取鍋交換時などの、取鍋からタンディッシュへの溶鋼注入終了直前の注入末期（以下、単に「取鍋からの注入末期」とも記す）における取鍋内スラグのタンディッシュへの流出を防止するために、従来、多数の提案がなされている。例えば、特許文献１には、取鍋の溶鋼流出孔の直上に渦流防止用耐火物を設置し、この渦流防止用耐火物によって渦流の発生を防止することで、スラグの流出を防止する方法が提案されている。しかしながら、取鍋の溶鋼流出孔をストッパーによって開閉する場合にはストッパーに渦流防止用耐火物を設置することで、この方法を採用することができるが、ストッパーを使用せずにスライディングノズルやロータリーノズルなどのスライド式ゲートを用いて溶鋼流出孔を開閉する現在の操業形態では、渦流防止用耐火物を設置する適当な場所がないことから設置が困難であり、実用的ではない。 Prevents the slag in the ladle from flowing out to the tundish at the end of pouring immediately before the end of the pouring of molten steel from the ladle to the tundish, such as when changing the ladle. Therefore, many proposals have been conventionally made. For example, Patent Document 1 discloses a method for preventing the outflow of slag by installing a vortex-preventing refractory directly above the molten steel outflow hole of a ladle and preventing the generation of eddy currents by the eddy-current preventing refractory. Proposed. However, when opening and closing the molten steel outflow hole of the ladle with a stopper, this method can be adopted by installing a refractory for preventing eddy currents in the stopper. However, sliding nozzles and rotary nozzles can be used without using a stopper. In the current operation mode in which the molten steel outflow hole is opened and closed using a sliding gate such as the above, it is difficult to install because there is no appropriate place for installing a refractory for preventing eddy currents, and it is not practical.
特許文献２には、取鍋からの注入末期に取鍋を溶鋼流出孔の設置された側に傾斜させるとともに、溶鋼流出孔から不活性ガスを取鍋内の溶鋼湯面に向けて吹き込む方法が提案されている。この方法によれば、取鍋を傾斜させることによって溶鋼流出孔位置の湯面が高くなり、渦流の生成する時期が若干遅れるが、機構的な制約が大きく、大幅な改善効果は期待できない。しかも、湯面高さが低い状態で不活性ガスを吹き込むため、却って溶鋼とスラグとの混合が助長され、スラグの巻き込みを増大させる恐れもある。 Patent Document 2 discloses a method in which the ladle is inclined toward the side where the molten steel outflow hole is installed at the end of pouring from the ladle and an inert gas is blown from the molten steel outflow hole toward the molten steel surface in the ladle. Proposed. According to this method, by tilting the ladle, the surface of the molten steel outflow hole becomes higher, and the time when the eddy current is generated is slightly delayed, but the mechanical limitation is large and a significant improvement effect cannot be expected. In addition, since the inert gas is blown in a state in which the molten metal surface is low, mixing of the molten steel and slag is promoted, and there is a possibility of increasing the slag entrainment.
特許文献３には、溶鋼流出孔の鉛直方向上方のスラグ層に、溶鋼流出孔の面積よりも大きな面積を有する耐火物製の塊状体を浸漬させ、塊状体の吸熱作用によってスラグの粘度を他の部位のスラグよりも大きくするとともに、塊状体によって渦流の形成を妨害することでスラグの流出を防止する方法が提案されている。この方法では、塊状体が溶鋼流出孔の直上に存在すればスラグ流出の防止効果が得られるが、スラグは溶融していることからスラグの流動によって塊状体も移動してしまい、塊状体を溶鋼流出孔の直上に安定して存在させることが極めて困難であるという問題がある。 In Patent Document 3, a refractory lump having an area larger than the area of the molten steel outflow hole is immersed in the slag layer vertically above the molten steel outflow hole, and the slag viscosity is changed by the endothermic action of the lump. There has been proposed a method of preventing the outflow of slag by making the slag larger than the slag and preventing the formation of the vortex by the lump. In this method, the slag outflow prevention effect can be obtained if the lumps are present directly above the molten steel outflow hole, but since the slag is melted, the lumps also move due to the flow of the slag, and the lumps are moved to the molten steel. There is a problem that it is extremely difficult to stably exist directly above the outflow hole.
特許文献４には、取鍋内のスラグにＳｉＯ2 源を添加してスラグ中のＳｉＯ2 濃度を上昇させることによりスラグの粘度を上昇させ、スラグの渦流への巻き込みを抑制する方法が提案されている。特許文献４によれば、スラグの粘度は通常の場合に比べて約２倍になり、これによりスラグの巻き込み量は半減するとしているが、格段の効果は得られていない。
以上説明したように、鋼の連続鋳造工程においては、取鍋からの注入末期における取鍋内スラグの流出を防止して鋳片の品質を向上させる方法が切望されているにも拘わらず、未だ有効な手段が提案されておらず、従って、高品質の鋳片を鋳造する際には、スラグの流出を防止するために多量の溶鋼が取鍋内に残留している状態で取鍋からタンディッシュへの溶鋼の注入を終了し、溶鋼の歩留まりを低下させているのが現状である。 As described above, in the continuous casting process of steel, a method for preventing the outflow of slag in the ladle at the end of pouring from the ladle and improving the quality of the slab is still desired. No effective means have been proposed and, therefore, when casting high quality slabs, the tank is tapped from the ladle with a large amount of molten steel remaining in the ladle to prevent slag spillage. The current situation is that the injection of molten steel into the dish is terminated and the yield of molten steel is reduced.
本発明は上記事情に鑑みてなされたもので、その目的とするところは、鋼の連続鋳造工程において、取鍋からタンディッシュへの溶鋼注入終了直前の注入末期における取鍋内スラグのタンディッシュへの流出を防止して、鋳片の品質を向上させるとともに溶鋼歩留まりを向上させることのできる取鍋を提供することであり、また、この取鍋を用いた鋳片の製造方法を提供することである。 The present invention has been made in view of the above circumstances, and the object is to tundish the slag in the ladle at the end of pouring immediately before the end of pouring the molten steel from the ladle to the tundish in the continuous casting process of steel. Is to provide a ladle that can improve the quality of the slab and improve the yield of molten steel, and provide a method for producing a slab using this ladle. is there.
上記課題を解決するための第１の発明に係る連続鋳造用取鍋は、底部に溶鋼流出孔を有し、該溶鋼流出孔が設置される底部の部位が他の底部の部位よりも鉛直方向下方に突出した突出部を有する連続鋳造用取鍋であって、前記突出部の深さをｈとし、収容能力最大の溶鋼を収容したときの最大溶鋼深さをＨとしたときに両者の比（ｈ／Ｈ）が０．０７５〜０．１５の範囲であり、且つ、突出部の容積をＶs とし、収容能力最大の溶鋼を収容したときの取鍋の容積をＶ0としたときに両者の比（Ｖs ／Ｖ0 ）が０．００２〜０．０１５の範囲であることを特徴とするものである。 The ladle for continuous casting according to the first invention for solving the above-mentioned problem has a molten steel outflow hole at the bottom, and the bottom portion where the molten steel outflow hole is installed is perpendicular to the other bottom portion. A ladle for continuous casting having a projecting portion projecting downward, where the depth of the projecting portion is h, and the maximum molten steel depth when accommodating the molten steel with the maximum capacity is defined as H. When (h / H) is in the range of 0.075 to 0.15, the volume of the protrusion is V s, and the volume of the ladle when the molten steel with the maximum capacity is accommodated is V 0. The ratio (V s / V 0 ) between the two is in the range of 0.002 to 0.015.
第２の発明に係る鋳片の製造方法は、第１の発明に記載の連続鋳造用取鍋に収容された溶鋼をタンディッシュに注入し、次いでタンディッシュに注入された溶鋼を鋳型に注入して鋳造することを特徴とするものである。 According to a second aspect of the present invention, there is provided a method for producing a slab, wherein molten steel contained in a ladle for continuous casting according to the first aspect is poured into a tundish, and then molten steel poured into the tundish is poured into a mold. It is characterized by casting.
第３の発明に係る鋳片の製造方法は、第２の発明において、取鍋内の残溶鋼とスラグとの合計質量が１トンとならない時点で、取鍋からタンディッシュへの溶鋼の注入を終了することを特徴とするものである。 The method for producing a slab according to the third invention is the second invention, in which the molten steel is poured from the ladle into the tundish when the total mass of the residual molten steel and the slag in the ladle is not 1 ton. It is characterized by terminating.
本発明に係る連続鋳造用取鍋によれば、取鍋からの注入末期に取鍋内に残留する溶鋼が少なくなっても、溶鋼吐出孔の設置された位置の湯面高さは比較的高いので、溶鋼中に渦流が形成されずにスラグのタンディッシュへの流出が防止され、渦流が形成された時点では取鍋に残留する溶鋼量（以下、「取鍋残湯」とも記す）は極めて少ないので、歩留まりを改善することができる。また、渦流が形成される前に、つまりスラグの流出が発生する前に、取鍋からの溶鋼の注入を終了した場合にも、取鍋残湯は数トンでよく、従来の２０トン程度に比べて大幅に少なくすることができる。その結果、溶鋼の歩留まりを向上させることができると同時に、取鍋交換時などの非定常部鋳片の品質を向上させることができ、工業上有益な効果がもたらされる。 According to the ladle for continuous casting according to the present invention, even when the amount of molten steel remaining in the ladle at the end of pouring from the ladle decreases, the molten steel surface height at the position where the molten steel discharge hole is installed is relatively high. Therefore, the slag is prevented from flowing out into the tundish without forming a vortex in the molten steel, and the amount of molten steel remaining in the ladle (hereinafter also referred to as “the ladle remaining hot water”) is extremely low when the vortex is formed. Since the amount is small, the yield can be improved. In addition, even when the pouring of molten steel from the ladle is completed before the vortex flow is formed, that is, before the slag flows out, the ladle remaining hot water may be several tons, which is about 20 tons in the past. Compared to this, it can be greatly reduced. As a result, the yield of molten steel can be improved, and at the same time, the quality of the unsteady portion slab at the time of changing the ladle can be improved, resulting in an industrially beneficial effect.
以下、添付図面を参照して本発明を具体的に説明する。図１は、本発明に係る取鍋の側面概略図、図２は、本発明に係る取鍋の平面概略図である。 Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic side view of a ladle according to the present invention, and FIG. 2 is a schematic plan view of the ladle according to the present invention.
図１及び図２に示すように、本発明に係る連続鋳造用の取鍋１は、外殻を鉄皮２で形成され、鉄皮２の内側に耐火物３が施工されて構成されており、取鍋１の底部に鉛直方向下方に突出した突出部４が設置されている。突出部４も外殻は鉄皮２で形成され、鉄皮２の内側に耐火物３が施工されており、突出部４の底面には溶鋼流出孔５が設置されている。耐火物３としては、慣用の不定形耐火物や定形耐火物を使用すればよい。但し、突出部４の深さ及び突出部４の容積が取鍋１の寸法に応じて以下を満足するように、突出部４を設置する必要がある。 As shown in FIGS. 1 and 2, a ladle 1 for continuous casting according to the present invention is formed by forming an outer shell with an iron shell 2 and constructing a refractory 3 inside the iron shell 2. A projecting portion 4 projecting downward in the vertical direction is installed at the bottom of the ladle 1. The protrusion 4 also has an outer shell formed of an iron shell 2, a refractory 3 is applied to the inside of the iron shell 2, and a molten steel outflow hole 5 is provided on the bottom surface of the protrusion 4. As the refractory 3, a conventional amorphous refractory or a regular refractory may be used. However, it is necessary to install the protruding portion 4 so that the depth of the protruding portion 4 and the volume of the protruding portion 4 satisfy the following according to the dimensions of the ladle 1.
即ち、取鍋１において、突出部４の設置されていない底部耐火物の底面６と、突出部４の底部耐火物の底面７との間の距離、つまり突出部４の深さをｈとし、突出部４の底部耐火物の底面７と収容能力最大の溶鋼を収容したときの取鍋１の最大湯面高さ位置８との間の距離、つまり収容能力最大の溶鋼を収容したときの最大溶鋼深さをＨとしたときに、突出部４の深さ（ｈ）と最大溶鋼深さ（Ｈ）との比（ｈ／Ｈ）が０．０７５〜０．１５の範囲であり、且つ、突出部４の容積をＶs とし、取鍋１が収容能力最大の溶鋼を収容したときの取鍋１の容積をＶ0としたときに、突出部４の容積（Ｖs ）と取鍋１の収容能力最大の容積（Ｖ0 ）との比（Ｖs ／Ｖ0）が０．００２〜０．０１５の範囲となるように、突出部４の形状を定める必要がある。ここで、収容能力最大の溶鋼とは、溶鋼を収容した取鍋１をクレーン或いは台車などで搬送することによって取鍋内の溶鋼が流動しても、収容した溶鋼が取鍋から溢れ出ないだけの最低限のフリーボードが取鍋１の上部に形成される状態のときに収容される溶鋼量であり、通常、「３００トン取鍋」などと呼ぶ場合の「３００トン」がこれに該当する。 That is, in the ladle 1, the distance between the bottom surface 6 of the bottom refractory where the protrusion 4 is not installed and the bottom 7 of the bottom refractory of the protrusion 4, that is, the depth of the protrusion 4 is h, The distance between the bottom surface 7 of the bottom refractory of the protrusion 4 and the maximum hot water surface height position 8 of the ladle 1 when the molten steel with the maximum capacity is accommodated, that is, the maximum when the molten steel with the maximum capacity is accommodated When the molten steel depth is H, the ratio (h / H) between the depth (h) of the protrusion 4 and the maximum molten steel depth (H) is in the range of 0.075 to 0.15, and When the volume of the protruding portion 4 is V s and the volume of the ladle 1 when the ladle 1 contains molten steel having the maximum capacity is V 0 , the volume (V s ) of the protruding portion 4 and the ladle 1 It is necessary to determine the shape of the protruding portion 4 so that the ratio (V s / V 0 ) to the maximum capacity (V 0 ) of the storage capacity is in the range of 0.002 to 0.015. . Here, the molten steel having the maximum capacity is that the contained molten steel does not overflow from the ladle even if the molten steel in the ladle flows by conveying the ladle 1 containing the molten steel with a crane or a carriage. This is the amount of molten steel that is accommodated when the minimum free board is formed in the upper part of the ladle 1 and usually corresponds to “300 tons” when referred to as “300 ton ladle”. .
突出部４をこれらの条件を満足する形状とすることにより、取鍋からタンディッシュへの溶鋼注入終了直前の注入末期において、取鍋１に残留する溶鋼が少なくなっても、溶鋼吐出孔５の設置された位置の湯面高さは比較的高いので、溶鋼での渦流の形成及び溶鋼品質の悪化を避けることができる。溶鋼の渦流は溶鋼流出孔５の設置位置における湯面高さが或る所定の高さ以下になると発生するが、本発明に係る取鍋１では突出部４が設置してあるために、取鍋１に残留する溶鋼量が少なくなるまで渦流が発生し難い。例えば、本発明の取鍋１を用いることで、取鍋１に残留する溶鋼とスラグとの合計質量が１トン程度になる時点まで、渦流による溶鋼の品質悪化を回避することができる。 By making the protrusion 4 into a shape that satisfies these conditions, even if the molten steel remaining in the ladle 1 decreases at the end of the injection immediately before the end of the molten steel injection from the ladle to the tundish, Since the hot water surface height at the installed position is relatively high, it is possible to avoid formation of vortex flow in the molten steel and deterioration of the molten steel quality. The vortex flow of the molten steel is generated when the molten steel surface height at the position where the molten steel outflow hole 5 is set is lower than a predetermined height. However, in the ladle 1 according to the present invention, the protruding portion 4 is installed. Swirl is unlikely to occur until the amount of molten steel remaining in the pan 1 decreases. For example, by using the ladle 1 of the present invention, it is possible to avoid the deterioration of the quality of the molten steel due to the vortex until the total mass of the molten steel and slag remaining in the ladle 1 reaches about 1 ton.
つまり、実質上、取鍋内の溶鋼のほとんどを注入してしまうまで、品質を良好に保つことができる。また、取鍋内の残溶鋼とスラグとの合計質量が２〜５トンとなった時点で取鍋１からタンディッシュへの注入を終了すれば、取鍋交換部でも確実に品質を維持して、連々鋳を継続することができる。 In other words, the quality can be kept good until substantially all of the molten steel in the ladle has been poured. In addition, if the pouring from the ladle 1 to the tundish is finished when the total mass of the residual molten steel and slag in the ladle reaches 2 to 5 tons, the quality can be reliably maintained even in the ladle replacement part. Continuous casting can be continued.
即ち、比（ｈ／Ｈ）が０．０７５以上で且つ比（Ｖs ／Ｖ0 ）が０．００２以上の場合に、取鍋スラグの品質への影響を抑制することができる。比（ｈ／Ｈ）が０．１５を超える場合や、比（Ｖs／Ｖ0 ）が０．０１５を超える場合には、突出部４が大きくなり、耐火物３の施工時間や施工コストなどの弊害の懸念があることから、これ以上に大きくする必要がない。一方、本発明の範囲外である比（ｈ／Ｈ）が０．０７５未満では、突出部４の深さが不足し、また、比（Ｖs／Ｖ0 ）が０．００２未満では突出部４に収容される溶鋼量が少な過ぎ、渦流による品質の悪化が避けられない。突出部４の形状は、四角柱、六角柱、楕円柱などの適宜の形状でよい。 That is, when the ratio (h / H) is 0.075 or more and the ratio (V s / V 0 ) is 0.002 or more, the influence on the quality of the ladle slag can be suppressed. When the ratio (h / H) exceeds 0.15, or when the ratio (V s / V 0 ) exceeds 0.015, the protrusion 4 becomes large, and the construction time and construction cost of the refractory 3 etc. Therefore, there is no need to make it larger than this. On the other hand, if the ratio (h / H), which is outside the scope of the present invention, is less than 0.075, the depth of the protrusion 4 is insufficient, and if the ratio (V s / V 0 ) is less than 0.002, the protrusion The amount of molten steel accommodated in 4 is too small, and deterioration of quality due to eddy current is inevitable. The shape of the protrusion 4 may be an appropriate shape such as a quadrangular column, a hexagonal column, or an elliptical column.
尚、図１に示す取鍋１では、取鍋１の底部を形成する鉄皮２の一部が下方に突出して突出部４を構成しているが、底部の鉄皮２を平滑とし、底部を構成する耐火物３の施工によって、突出部４を形成することもできる。即ち、図３に示すように、取鍋１Ａにおいては、底部の耐火物３の施工を、底部耐火物の底面６の部位では厚くし、底部耐火物の底面７の部位では薄くすることで、突出部４が形成されている。取鍋１Ａは、その他の構造は図１に示す取鍋１と同一構造となっており、同一の部分は同一符号により示し、その説明は省略する。尚、図３は、本発明に係る取鍋の他の形態例を示す側面概略図である。 In the ladle 1 shown in FIG. 1, a part of the iron skin 2 that forms the bottom of the ladle 1 protrudes downward to form the protrusion 4. The protrusion 4 can also be formed by the construction of the refractory 3 that constitutes the above. That is, as shown in FIG. 3, in the ladle 1A, the construction of the bottom refractory 3 is made thicker at the bottom 6 part of the bottom refractory and thinned at the bottom 7 part of the bottom refractory. A protruding portion 4 is formed. The other structure of the ladle 1A is the same as that of the ladle 1 shown in FIG. 1, and the same portions are denoted by the same reference numerals, and the description thereof is omitted. FIG. 3 is a schematic side view showing another embodiment of the ladle according to the present invention.
このように構成される本発明に係る取鍋を用いて転炉などの精錬炉で精錬された溶鋼を受鋼し、更に必要に応じて取鍋内の溶鋼に二次精錬炉にて脱ガス精錬などを施した後、この溶鋼を連続鋳造機に搬送して連続鋳造する。図４に、本発明に係る取鍋に収容された溶鋼を連続鋳造する状況を示す。尚、図４中の取鍋は前述した図１に示す取鍋１である。 Receiving molten steel refined in a refining furnace such as a converter using the ladle according to the present invention configured as described above, and further degassing the molten steel in the ladle in a secondary refining furnace as necessary. After refining, the molten steel is conveyed to a continuous casting machine and continuously cast. In FIG. 4, the condition which continuously casts the molten steel accommodated in the ladle concerning this invention is shown. In addition, the ladle in FIG. 4 is the ladle 1 shown in FIG. 1 mentioned above.
図４において、内側を耐火物で施工されたタンディッシュ１３が、タンディッシュカー（図示せず）に搭載されて鋳型１７の上方所定位置に配置され、また、タンディッシュ１３の上方所定位置には、溶鋼９を収容した本発明に係る取鍋１が配置されている。取鍋１の底部の突出部４には、溶鋼流出孔５を形成する上ノズル１０が耐火物３と嵌合して設置され、この上ノズル１０の下面に接して、固定板１１Ａ及び摺動板１１Ｂからなるスライディングノズル１１が溶鋼流量制御装置として設置され、更に、スライディングノズル１１の下面に接して、大気を遮断するためのロングノズル１２が接続されている。摺動板１１Ｂは、往復型アクチュエーター（図示せず）に接続されており、往復型アクチュエーターの作動により、固定板１１Ａと密に接触したまま移動し、固定板１１Ａの開口部と摺動板１１Ｂの開口部との開口部面積を調整することにより溶鋼流出孔５を通過する溶鋼量が制御されるようになっている。スライディングノズル１１に代えて摺動板１１Ｂが回転するロータリーノズルとしてもよい。また、タンディッシュ１３の底部には上ノズル１４が配置され、この上ノズル１４の下面に接して、固定板１５Ａ及び摺動板１５Ｂからなるスライディングノズル１５が溶鋼流量制御装置として設置され、更に、スライディングノズル１５の下面に接して、先端を鋳型１７の内部の溶鋼９に浸漬させた浸漬ノズル１６が接続されている。摺動板１５Ｂは、往復型アクチュエーター（図示せず）に接続されており、往復型アクチュエーターの作動により、固定板１５Ａと密に接触したまま移動し、固定板１５Ａの開口部と摺動板１５Ｂの開口部との開口部面積を調整することによりタンディッシュ１３から鋳型１７への溶鋼注入量が制御されるようになっている。 In FIG. 4, the tundish 13 constructed with a refractory inside is mounted on a tundish car (not shown) and disposed at a predetermined position above the mold 17, and at a predetermined position above the tundish 13. A ladle 1 according to the present invention containing molten steel 9 is disposed. An upper nozzle 10 that forms a molten steel outflow hole 5 is fitted into the refractory 3 and installed on the protruding portion 4 at the bottom of the ladle 1. A sliding nozzle 11 made of a plate 11B is installed as a molten steel flow rate control device, and further, a long nozzle 12 for contacting the lower surface of the sliding nozzle 11 and blocking the atmosphere is connected. The sliding plate 11B is connected to a reciprocating actuator (not shown), and is moved in close contact with the fixed plate 11A by the operation of the reciprocating actuator, and the opening of the fixed plate 11A and the sliding plate 11B are moved. The amount of molten steel passing through the molten steel outflow hole 5 is controlled by adjusting the area of the opening with the opening. Instead of the sliding nozzle 11, a rotary nozzle that rotates the sliding plate 11B may be used. Further, an upper nozzle 14 is disposed at the bottom of the tundish 13, and a sliding nozzle 15 comprising a fixed plate 15A and a sliding plate 15B is installed as a molten steel flow rate control device in contact with the lower surface of the upper nozzle 14, An immersion nozzle 16 whose tip is immersed in the molten steel 9 inside the mold 17 is connected in contact with the lower surface of the sliding nozzle 15. The sliding plate 15B is connected to a reciprocating actuator (not shown), and is moved in close contact with the fixed plate 15A by the operation of the reciprocating actuator, and the opening of the fixed plate 15A and the sliding plate 15B are moved. The amount of molten steel injected from the tundish 13 to the mold 17 is controlled by adjusting the opening area with the opening.
鋳型１７に注入された溶鋼９は、鋳型１７と接触して冷却されて凝固シェル１９を形成し、外殻を凝固シェル１９として内部を未凝固の溶鋼９とする鋳片１８が鋳型１７の下方に連続的に引き抜かれ、やがて中心部まで完全に凝固して鋳片が製造される。鋳片１８の引き抜き中は、タンディッシュ１３の溶鋼量をほぼ一定値に調整するとともに、鋳型１７における溶鋼湯面位置をほぼ一定位置に制御する。取鍋１からタンディッシュ１３への溶鋼９の注入流はロングノズル１２によって大気と遮断され、タンディッシュ１３から鋳型１７への溶鋼９の注入流は浸漬ノズル１６によって大気と遮断されている。 The molten steel 9 injected into the mold 17 is cooled in contact with the mold 17 to form a solidified shell 19, and a slab 18 having an outer shell as the solidified shell 19 and an inside of the unsolidified molten steel 9 is below the mold 17. The slab is produced by continuously solidifying to the central part and eventually solidifying. While the slab 18 is being drawn, the molten steel amount of the tundish 13 is adjusted to a substantially constant value, and the molten steel surface position in the mold 17 is controlled to a substantially constant position. An injection flow of the molten steel 9 from the ladle 1 to the tundish 13 is blocked from the atmosphere by the long nozzle 12, and an injection flow of the molten steel 9 from the tundish 13 to the mold 17 is blocked from the atmosphere by the immersion nozzle 16.
このようにして鋳造することで、取鍋１に収容された溶鋼９は減少し、やがて溶鋼流出孔５の位置の溶鋼湯面高さが所定の高さになった時点で取鍋１に残留する溶鋼９に渦流が形成される。この渦流に、取鍋内の溶鋼９の上に存在するスラグ２０が巻き込まれてタンディッシュ１３に流出する。このスラグ２０のタンディッシュ１３への流出を、電磁気力を用いたスラグ流出検出器、タンディッシュ内湯面のスラグ目視観察、或いは取鍋１の質量計測などの慣用の手段によって確認し、その時点で摺動板１１Ｂを作動させ、取鍋１からタンディッシュ１３への注入を終了する。本発明に係る取鍋１では渦流が形成されてスラグ２０が流出する時点は、取鍋１に残留する溶鋼９とスラグ２０との合計質量が１トン程度になる時点であり、取鍋１に残留する溶鋼量を極めて少なくすることができる。また、スラグ２０の流出と同時に取鍋１からの注入を終了するので、スラグ２０による品質低下を限られた狭い範囲に抑えることができる。 By casting in this way, the molten steel 9 accommodated in the ladle 1 decreases, and when the molten steel surface level at the position of the molten steel outflow hole 5 eventually reaches a predetermined height, it remains in the ladle 1. An eddy current is formed in the molten steel 9. The slag 20 existing on the molten steel 9 in the ladle is caught in this vortex and flows out to the tundish 13. The outflow of the slag 20 to the tundish 13 is confirmed by a conventional means such as a slag outflow detector using electromagnetic force, visual observation of the slag in the tundish, or measurement of the mass of the ladle 1, and at that time The sliding plate 11B is operated, and the injection from the ladle 1 to the tundish 13 is finished. In the ladle 1 according to the present invention, when the vortex is formed and the slag 20 flows out, the total mass of the molten steel 9 and the slag 20 remaining in the ladle 1 is about 1 ton. The amount of remaining molten steel can be extremely reduced. Moreover, since the injection | pouring from the ladle 1 is complete | finished simultaneously with the outflow of the slag 20, the quality fall by the slag 20 can be suppressed to the limited narrow range.
前記はわずかなスラグの流出を許容する場合であるが、第２の方法として、溶鋼９に渦流が形成される以前、つまりスラグ２０がタンディッシュ１３に流出する以前に摺動板１１Ｂを作動させ、取鍋１からタンディッシュ１３への注入を終了するようにしてもよい。具体的には、取鍋１の質量計測などによって取鍋１に収容される溶鋼９の残量とスラグ２０との合計質量を計測し、取鍋内の残溶鋼とスラグとの合計質量が２〜５トン程度、望ましくは２〜３トンになった時点で注入を終了すれば、スラグ２０のタンディッシュ１３への流出を完全に防止することができる。つまり、取鍋１に残溶鋼とスラグとの合計量で２〜５トン程度を残留させるだけで、鋳片１８のスラグ２０による品質低下を未然に防止することができる。 The above is a case where slight slag outflow is allowed. However, as a second method, before the vortex is formed in the molten steel 9, that is, before the slag 20 flows out to the tundish 13, the sliding plate 11B is operated. The pouring from the ladle 1 into the tundish 13 may be terminated. Specifically, the total mass of the molten steel 9 accommodated in the ladle 1 and the slag 20 is measured by measuring the mass of the ladle 1 and the total mass of the residual molten steel and slag in the ladle is 2. If the injection is terminated when the amount reaches about -5 tons, preferably 2 to 3 tons, the slag 20 can be completely prevented from flowing out to the tundish 13. That is, it is possible to prevent deterioration in quality due to the slag 20 of the slab 18 only by leaving about 2 to 5 tons in the total amount of the molten steel and slag in the ladle 1.
連続鋳造を更に続ける場合には、鋳造を終了した取鍋１を取り除き、別のヒートの溶鋼９を収容した別の取鍋１をタンディッシュ１３の上方所定位置に配置し、スライディングノズル１１の下部にロングノズル１２を接続し、連々鋳を継続する。連々鋳の全てのヒートにおいて、取鍋１からタンディッシュ１３への注入終了時点を前述した２つの方法のうちの何れかの方法によって判定し、取鍋１からの注入を終了する。連々鋳の最後のヒートでは、取鍋１からの注入終了後はタンディッシュ１３に残留する溶鋼９を鋳型１７に注入し、タンディッシュ１３に残留する溶鋼９が所定の量になった時点で連々鋳を終了する。 When continuous casting is further continued, the ladle 1 that has finished casting is removed, another ladle 1 containing molten steel 9 of another heat is placed at a predetermined position above the tundish 13, and the bottom of the sliding nozzle 11 The long nozzle 12 is connected to and the casting is continued continuously. In all the continuous casting heats, the end point of pouring from the ladle 1 to the tundish 13 is determined by any one of the two methods described above, and pouring from the ladle 1 is terminated. In the last heat of continuous casting, after the pouring from the ladle 1 is finished, the molten steel 9 remaining in the tundish 13 is poured into the mold 17 and continuously when the molten steel 9 remaining in the tundish 13 reaches a predetermined amount. Finish casting.
本発明に係る取鍋１を使用することで、取鍋１に残留する溶鋼９が少なくなっても渦流による品質悪化を最小限に抑制することができ、渦流が形成された時点では取鍋１に残留する溶鋼９は極めて少ないので、取鍋残湯を少なくすることができ、その結果、溶鋼９の歩留まりを向上させることができる。また、渦流が形成される前に、つまりスラグ２０の流出が発生する前に、取鍋１からの溶鋼の注入を終了した場合にも、取鍋残湯は数トンでよく、従来の２０トン程度に比べて大幅に少なくすることができ、且つ、特に悪化しやすい取鍋交換部の溶鋼の品質を確実に向上させることができる。ここで、取鍋交換部の溶鋼とは、取鍋交換直前に取鍋からタンディッシュに注がれる溶鋼を指す。 By using the ladle 1 according to the present invention, even if the molten steel 9 remaining in the ladle 1 decreases, quality deterioration due to vortex flow can be suppressed to a minimum, and when the vortex flow is formed, the ladle 1 Since the amount of molten steel 9 remaining in the steel is extremely small, the ladle remaining hot water can be reduced, and as a result, the yield of the molten steel 9 can be improved. Also, even when the pouring of molten steel from the ladle 1 is completed before the vortex flow is formed, that is, before the outflow of the slag 20 occurs, the ladle remaining hot water may be several tons, and the conventional 20 tons The quality of the molten steel in the ladle replacement part, which can be greatly reduced compared to the degree, and which is particularly likely to deteriorate, can be reliably improved. Here, the molten steel of the ladle exchange part refers to molten steel poured into the tundish from the ladle immediately before the ladle exchange.
収容最大能力が３００トンの取鍋の形状を変更し、この取鍋に収容したＳＰＣＣ材（冷間圧延鋼板）を２ストランドの連続鋳造機で連続鋳造し、取鍋形状の鋳片品質に及ぼす影響を評価する試験を実施した。表１に、製鋼設備及び操業条件を示す。 The shape of the ladle with a maximum capacity of 300 tons is changed, and the SPCC material (cold rolled steel plate) accommodated in this ladle is continuously cast by a 2-strand continuous casting machine, which affects the quality of the ladle-shaped slab. A test was conducted to assess the impact. Table 1 shows steelmaking facilities and operating conditions.
取鍋には前述した図１に示すような突出部を設け、それぞれの寸法を変更し、鋳片品質との関係を調査した。表２に、取鍋及び突出部の寸法の１例を示す。 The ladle was provided with a protrusion as shown in FIG. 1 described above, and the dimensions were changed to investigate the relationship with the slab quality. Table 2 shows an example of the dimensions of the ladle and the protruding portion.
連続鋳造では、厚みが２２０ｍｍ、幅が１２００ｍｍのスラブ鋳片をストランド当たり６トン／分の鋳造速度で鋳造し、鋳造の際には、電磁気力を印加して、鋳型内湯面の１／４幅相当部の溶鋼流速が０．２ｍ／秒となるように制御した。鋳造中は取鍋内の溶鋼量とスラグ量との合計質量を連続して計測した。取鍋内の溶鋼量とスラグ量との合計質量は、受鋼前の空の状態の取鍋の質量計測値との差分から求めた。取鍋からタンディッシュへの注入終了時点は、取鍋内の溶鋼を全てタンディッシュ内に注入した時点とした。従って、取鍋内のスラグは、多い少ないの差はあるものの全ての条件でタンディッシュ内に流入した。鋳造後、鋳片を熱間圧延し、更に冷間圧延して０．２ｍｍの板厚とし、この薄鋼板において酸化物系非金属介在物（以下、「介在物」と記す）の個数を計測し、計測した介在物と鋳片の鋳造位置との関係を整理した。 In continuous casting, a slab slab having a thickness of 220 mm and a width of 1200 mm is cast at a casting speed of 6 ton / min per strand. In casting, an electromagnetic force is applied to make a quarter width of the hot water surface in the mold. It controlled so that the molten steel flow velocity of a considerable part might be set to 0.2 m / sec. During casting, the total mass of molten steel and slag in the ladle was continuously measured. The total mass of the amount of molten steel and the amount of slag in the ladle was determined from the difference from the measured value of the empty ladle before receiving steel. The end of pouring from the ladle into the tundish was the time when all the molten steel in the ladle was poured into the tundish. Therefore, the slag in the ladle flowed into the tundish under all conditions although there were many differences. After casting, the slab is hot-rolled and then cold-rolled to a thickness of 0.2 mm, and the number of oxide-based non-metallic inclusions (hereinafter referred to as “inclusions”) in this thin steel sheet is measured. The relationship between the measured inclusions and the casting position of the slab was organized.
タンディッシュ内にスラグが流出した後に取鍋からタンディッシュへの注入を終了したので、何れの条件でも取鍋からの注入末期に該当する部位の鋳片には介在物が検出され、しかも検出値は社内規定値（直径５０μｍ以上のものが１個／ｍ2 以上）を上回った。この取鍋スラグが混入した部位の鋳造長さ位置から、取鍋スラグが混入した時点における取鍋内の残溶鋼とスラグとの合計質量を求めた。求めた取鍋内の残溶鋼とスラグとの合計質量を、前述した表２に「巻き込み発生時の残湯量」として示す。 Since the injection from the ladle into the tundish was completed after the slag flowed into the tundish, inclusions were detected in the slab at the end of the pouring from the ladle under any condition, and the detected value Exceeded the in-house defined value (one with a diameter of 50 μm or more is 1 piece / m 2 or more). From the casting length position of the portion where the ladle slag was mixed, the total mass of the residual molten steel and slag in the ladle at the time when the ladle slag was mixed was determined. The total mass of the remaining molten steel and slag in the ladle obtained is shown as “the amount of remaining hot water at the time of entrainment” in Table 2 described above.
表２に示すように、対策を実施しなかった条件１では、取鍋内の残溶鋼とスラグとの合計質量、即ち残湯量が２０トンの時点で取鍋内スラグの流出が発生していた。従って、条件１において品質の良好な鋼板を得るためには、取鍋内に２０トン程度の溶鋼を残した状態で取鍋からタンディッシュへの注入を終了する必要のあることが分かった。 As shown in Table 2, in condition 1 where no measures were taken, the total mass of the residual molten steel and slag in the ladle, that is, the slag in the ladle occurred when the amount of remaining hot water was 20 tons. . Therefore, in order to obtain a steel plate with good quality under condition 1, it was found that the pouring from the ladle to the tundish had to be completed with about 20 tons of molten steel left in the ladle.
一方、突出部を設けた条件２〜５では、スラグ巻き込み発生時の残湯量は条件１に比べて大幅に少なくなることが明らかになった。特に、条件３及び条件５では、取鍋内の残湯量が１トンになる時点までスラグの流出が防止でき、品質の悪化する部位は狭い範囲に限られ、格段の効果があることが分かった。 On the other hand, in the conditions 2 to 5 where the protrusions were provided, it became clear that the amount of remaining hot water at the time of the occurrence of slag entrainment was significantly smaller than that in the condition 1. In particular, in conditions 3 and 5, it was found that the outflow of slag can be prevented until the amount of remaining hot water in the ladle reaches 1 ton, and the parts where quality deteriorates are limited to a narrow range, and it has been found that there is a remarkable effect. .
取鍋底部の突出部の形状を種々変更して、上記の方法で介在物を調査した結果を図５にまとめて示す。図５においては、取鍋内の残湯量が１トン以下となった時点でスラグの流出が発生した条件は○印で表示し、１トンを超える時点でスラグの流出が発生した条件は●印で表示している。図５に示すように、取鍋の底部に突出部を設け、突出部の寸法を、突出部の深さ（ｈ）と最大溶鋼深さ（Ｈ）との比（ｈ／Ｈ）が０．０７５以上で、且つ突出部の容積（Ｖs ）と取鍋の収容能力最大の容積（Ｖ0 ）との比（Ｖs／Ｖ0 ）が０．００２以上となるようにすることで、取鍋内の残湯量が１トンになる時点までスラグの流出を防止でき、鋳片品質を向上させることができることが明らかとなった。 The result of having investigated the inclusion by said method by changing the shape of the protrusion part of a ladle bottom part collectively is shown in FIG. In Fig. 5, the condition that the slag flowed out when the amount of remaining hot water in the ladle became less than 1 ton is indicated by a circle, and the condition that the slag flowed out when it exceeded 1 ton was marked with Is displayed. As shown in FIG. 5, a protrusion is provided at the bottom of the ladle, and the ratio of the protrusion depth (h) to the maximum molten steel depth (H) (h / H) is 0. By setting the ratio (V s / V 0 ) between 075 or more and the volume (V s ) of the protrusion to the maximum capacity (V 0 ) of the ladle to be 0.002 or more, It became clear that the outflow of slag can be prevented and the slab quality can be improved until the amount of remaining hot water in the pan reaches 1 ton.
１ 取鍋
２ 鉄皮
３ 耐火物
４ 突出部
５ 溶鋼流出孔
６ 底面
７ 底面
８ 最大湯面高さ位置
９ 溶鋼
１０ 上ノズル
１１ スライディングノズル
１２ ロングノズル
１３ タンディッシュ
１４ 上ノズル
１５ スライディングノズル
１６ 浸漬ノズル
１７ 鋳型
１８ 鋳片
１９ 凝固シェル
２０ スラグ
DESCRIPTION OF SYMBOLS 1 Ladle 2 Iron skin 3 Refractory 4 Protruding part 5 Molten steel outflow hole 6 Bottom surface 7 Bottom surface 8 Maximum molten metal surface height position 9 Molten steel 10 Upper nozzle 11 Sliding nozzle 12 Long nozzle 13 Tundish 14 Upper nozzle 15 Sliding nozzle 16 Immersion nozzle 17 Mold 18 Slab 19 Solidified Shell 20 Slag
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| ES2595214T3 (en) * | 2013-04-26 | 2016-12-28 | Refractory Intellectual Property Gmbh & Co. Kg | Wash spoon and bottom of it |
| JP6192604B2 (en) * | 2014-06-26 | 2017-09-06 | 株式会社神戸製鋼所 | Ladle operation method |
| JP6527069B2 (en) * | 2015-10-19 | 2019-06-05 | 株式会社神戸製鋼所 | Operating method of intermediate container for molten steel |
| CN109226734B (en) * | 2018-11-19 | 2023-08-25 | 泰州市旺鑫耐火材料有限公司 | Automatic flow control device for tundish nozzle |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6343752A (en) * | 1986-08-08 | 1988-02-24 | Nippon Kokan Kk <Nkk> | Molten metal vessel providing weir |
| JPH0952170A (en) * | 1995-08-15 | 1997-02-25 | Nippon Steel Corp | Container for molten metal |
| JP2000202596A (en) * | 1999-01-20 | 2000-07-25 | Kawasaki Steel Corp | Tundish for continuous casting and continuous casting method |
| JP2003230947A (en) * | 2002-02-06 | 2003-08-19 | Sanyo Special Steel Co Ltd | Method for casting high-cleanness steel |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6343752A (en) * | 1986-08-08 | 1988-02-24 | Nippon Kokan Kk <Nkk> | Molten metal vessel providing weir |
| JPH0952170A (en) * | 1995-08-15 | 1997-02-25 | Nippon Steel Corp | Container for molten metal |
| JP2000202596A (en) * | 1999-01-20 | 2000-07-25 | Kawasaki Steel Corp | Tundish for continuous casting and continuous casting method |
| JP2003230947A (en) * | 2002-02-06 | 2003-08-19 | Sanyo Special Steel Co Ltd | Method for casting high-cleanness steel |
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