JPS61232047A - Method for controlling temperature of molten metal for continuous casting - Google Patents

Abstract

PURPOSE:To improve the contact efficiency between an inert gas and molten steel and to form a good-quality ingot having no component segregation, etc. by blowing an inert gas to a submerged gate provided in a flow passage for the molten steel and adjusting the temp. of the molten metal. CONSTITUTION:The submerged gate 5 is provided on the down stream side of the position where a pouring pipe 2 of a tundish 1 is inserted in such a manner as to contact with the base of the tundish 1. The inert gas is blown from a porous plug 6 into the molten steel M under passage through the space part 4 of the gate 5 and the blowing rate of the inert gas is adjusted to decrease the temp. of the molten steel M down to the prescribed temp. The molten steel M which is decreased in the temp. flows successively from a refractory wall 3b toward the down stream. The inert gas blown into the space part 4 stagnates for a while in the space part 4 and contributes substantially with the temp. decrease of the molten steel M by contacting efficiently with the molten steel M in the space part 4 and thereafter the gas flows successively upward from the front and rear refractory walls 3a, 3b. The contact time of the molten metal M and the inert gas is therefore considerably extended and the cooling effect is improved.

Description

【発明の詳細な説明】 ［産業上の利用分野］ 本発明は連続鋳造用金属溶湯の温度制御方法に関し、殊
に、連続鋳造用金属溶湯を鋳型に注入するまでの段階で
、該金属溶湯に不活性ガスを吹込んで該溶湯の温度を可
及的一定に保ち、連続鋳造鋳片の表面品質及び内部品質
を高める技術に関するものである。Detailed Description of the Invention [Industrial Application Field] The present invention relates to a method for controlling the temperature of molten metal for continuous casting, and in particular, to a method for controlling the temperature of molten metal for continuous casting before pouring the molten metal into a mold. The present invention relates to a technique for keeping the temperature of the molten metal as constant as possible by blowing inert gas to improve the surface quality and internal quality of continuously cast slabs.

［従来の技術］ 金属の連続鋳造においては、金属溶湯の鋳型注入温度が
低過ぎるとノロ噛みが多発して鋳片の非金属介在物量が
増加する他、ノズル詰りも生じ易くなって操業安定性が
低下するところから、金属溶湯温度は若干高めにコント
ロールしながら連続鋳造を行なうのが通例である。しか
し鋳型注入温度が高過ぎると、鋳片に表面割れや内部欠
陥が発生し易くなる池内部偏析も生じ易くなり、更には
ブレークアウトを生じる恐れも出てくるので、溶湯温度
を高めるにしても十分な注意を払わなければならない、
また連続鋳造における鋳造開始温度は、金Ｎ威分の中心
偏析を少なくし且つ中心部への不純物の集中を避けると
いう意味から、当該金属の液相線に近い温度の方が好ま
しいとされている。[Prior art] In continuous metal casting, if the temperature at which the molten metal is poured into the mold is too low, slag bite occurs frequently and the amount of non-metallic inclusions in the slab increases, and nozzle clogging is likely to occur, resulting in operational stability. It is customary to carry out continuous casting while controlling the temperature of the molten metal to be slightly higher, since the temperature of the molten metal decreases. However, if the mold injection temperature is too high, surface cracks and internal defects are likely to occur in the slab, and internal segregation is also likely to occur, and there is also a risk of breakout, so even if the molten metal temperature is raised, must take due care,
In addition, it is said that the casting start temperature in continuous casting is preferably close to the liquidus line of the metal in order to reduce central segregation of gold and nitrogen components and to avoid concentration of impurities in the center. .

この様なところから金属溶湯の連続鋳造においては（後
記第４図参照）、鋳造開始温度を当該金属の液相線の若
干高温側に維持すべく、（イ）溶製炉からの出湯温度を
コントロールする方法、（ａ）取鍋内の溶湯に冷却材を
投入し或は不活性ガスを吹込んで所定の温度まで降温す
る方法、等が実施されている。しかしこれらの方法では
、取鍋からタンディツシュを経て鋳型へ注入するまでに
相当の時間がかかる為、鋳造初期と中期及び末期で溶湯
温度がかなり変化し、「鋳造開始温度を一定に保つ」と
いう本来の目的は十分に達成できない。From this point of view, in continuous casting of molten metal (see Figure 4 below), in order to maintain the casting start temperature slightly higher than the liquidus line of the metal, (a) the temperature at which the metal exits the smelting furnace is adjusted. Control methods include (a) cooling the molten metal in a ladle to a predetermined temperature by injecting a coolant or blowing inert gas into it, and the like. However, with these methods, it takes a considerable amount of time to pour from the ladle through the tundish into the mold, so the temperature of the molten metal changes considerably during the initial, middle, and final stages of casting, and the original goal of ``keeping the starting temperature constant'' is not met. objective cannot be fully achieved.

そこでタンディツシュ内へ注入される金属溶湯の温度を
やや高め（過加熱状ＷＢ）に設定し、タンディツシュ内
において、（ａ）金属細片を投入しその溶解潜熱を利用
して所定の鋳造開始温度まで降温させる方法、或は（ｂ
）金属溶湯に当該溶湯の温度に応じた量の不活性ガスを
吹込んで所定の温度まで降温させる方法、が提案されて
いる。Therefore, the temperature of the molten metal injected into the tundish is set to a slightly higher temperature (superheated WB), and inside the tundish, (a) metal pieces are introduced and the latent heat of melting is used to reach a predetermined casting start temperature. A method of lowering the temperature, or (b
) A method has been proposed in which an amount of inert gas corresponding to the temperature of the molten metal is blown into the molten metal to lower the temperature to a predetermined temperature.

ところがタンディツシュ内溶湯の過加熱温度（Δｔ）は
一般に６０℃程度以下と小さく、シかもタンディツシュ
内における溶湯の滞留時間は比較的短い為、この様な条
件のもとですみやかに溶解し得る様な金属細片の選択が
むつかしく、シかも投入量を誤ると未溶解の金属細片に
よってタンディツシュノズルが閉塞するといった事故を
生じたり鋳片あるいは、圧延されたあとの製品の欠陥原
因になることがある。その為工業規模での実用化を考え
れば前記（ｂ）の不活性ガス吹込み法が有効と考えられ
、この種の方法としては例えば特開昭５１−３７０３３
号が知られている。However, the superheating temperature (Δt) of the molten metal in the tundish is generally small, about 60°C or less, and the residence time of the molten metal in the tundish is relatively short, so it is difficult to melt the molten metal quickly under these conditions. It is difficult to select the metal strips, and if the amount of input is incorrect, unmelted metal strips can cause accidents such as clogging of the tundish nozzle or cause defects in the slabs or rolled products. be. Therefore, considering the practical use on an industrial scale, the above-mentioned inert gas injection method (b) is considered to be effective.
number is known.

［発明が解決しようとする問題点］ 不活性ガスの吹込みによって冷却する場合、タンディツ
シュの底部にポーラスプラグを設けて吹込む方法が考え
られるが、吹込まれた不活性ガスはすみやかに湯面上に
浮上してしまう為冷却効率は極めて低く、大量の不活性
ガスが無駄に消費されるという問題がある。しかもタン
ディツシュは取鍋等に比べて概して浅底であり、底部か
ら湯面までの長さは極めて短いので、溶湯中を浮上する
気泡と溶湯の接触時間が極めて短く、満足な冷却効率を
得ることができない、その為大部分の不活性ガスは溶湯
の冷却に供されることなく湯面から放散されてしまう、
こうした状況にもかかわらず被処理溶湯を十分に降温さ
せる為には、タンディツシュ底部のかなり広い面積に亘
ってポーラスプラグを設置して大量のガスを吹込まなけ
ればならず、それに伴ってタンディツシュ底部の強度不
足のため溶湯が漏出する危険性が生じたり、或は不活性
ガス吹込み量を少なくしたときにポーラスプラグの目詰
まり或は損傷といった問題も派生してくる。しかもタン
ディシュ内溶湯温度は後記第４図に破線で示すごとく鋳
造初期にはタンディシュ耐火物自身が吸熱するため低く
なり、中期には定常状態で一定高温状態が維持され、末
期には下がってくる。従って鋳造初期および末期の溶湯
温度を適切に維持するためには鋳造前の溶湯温度を全体
的に高める必要があり、その時鋳造中期の溶湯温度が高
すぎ前述のごとく内部割れや中心偏析の点で問題を残す
。[Problems to be Solved by the Invention] When cooling by blowing inert gas, it is possible to provide a porous plug at the bottom of the tundish and blow in, but the inert gas that is blown quickly rises above the hot water surface. The problem is that the cooling efficiency is extremely low and a large amount of inert gas is wasted. Furthermore, tundishes generally have a shallow bottom compared to ladles, etc., and the length from the bottom to the surface of the molten metal is extremely short, so the contact time between the bubbles floating in the molten metal and the molten metal is extremely short, resulting in satisfactory cooling efficiency. Therefore, most of the inert gas is dissipated from the surface of the molten metal without being used to cool the molten metal.
Despite these circumstances, in order to sufficiently cool down the molten metal to be treated, it is necessary to install a porous plug over a fairly wide area at the bottom of the tundish and blow in a large amount of gas. Problems arise such as the risk of molten metal leaking due to insufficient strength, or clogging or damage to the porous plug when the amount of inert gas blown is reduced. In addition, the temperature of the molten metal in the tundish decreases in the early stages of casting as the tundish refractory itself absorbs heat, as shown by the broken line in Figure 4 below, maintains a constant high temperature state in the middle stage, and decreases in the final stage. Therefore, in order to properly maintain the molten metal temperature at the initial and final stages of casting, it is necessary to raise the molten metal temperature as a whole before casting, and at this time, the molten metal temperature at the middle stage of casting is too high, causing internal cracks and center segregation as described above. leave the problem.

本発明はこうした問題点に着目してなされたものであっ
て、その目的は、鋳型への鋳込み直前の金属溶湯を、上
記の様な問題を生ずることなく比較的少量の不活性ガス
で効率良く冷却し、鋳込み温度を可及的一定に維持する
ことのできる方法を提供しようとするものである。The present invention has been made in view of these problems, and its purpose is to efficiently process molten metal just before it is poured into a mold using a relatively small amount of inert gas without causing the above-mentioned problems. The purpose is to provide a cooling method that can maintain the casting temperature as constant as possible.

ｃ問題点を解決する為の手段］ 本発明に係る連続鋳造用金属溶湯の温度制御方法は、多
数の金属溶湯通過孔を有する一対の耐火壁の間に空間部
を形成してなる潜り堰を、連続鋳造用金属溶湯流路の底
面に接して立設し、該潜り堰の前記空間部を通過する金
属溶湯に不活性ガスを吹込むと共に、該不活性ガスの吹
込み量を調整することによって金属溶湯の温度を一定の
範囲にコントロールするところに要旨を有するものであ
る。c. Means for Solving Problems] The method for controlling the temperature of molten metal for continuous casting according to the present invention includes a submerged weir formed by forming a space between a pair of fireproof walls having a large number of molten metal passage holes. , installed upright in contact with the bottom of the molten metal channel for continuous casting, blowing an inert gas into the molten metal passing through the space of the submerged weir, and adjusting the amount of the inert gas blown. The gist is that the temperature of the molten metal is controlled within a certain range.

［作用］ 本発明では、例えば第１図（模式図）に示す様な設備を
用いて金属溶湯（以下溶鋼で代表する）の連続鋳造を行
なう、即ち本例では、タンディツシュｌの注入管２装入
位置よりも下流側に、潜り堰［多数の溶鋼通過孔Ｐを有
する耐火壁３ａ。[Function] In the present invention, continuous casting of molten metal (hereinafter referred to as molten steel) is carried out using, for example, equipment as shown in FIG. 1 (schematic diagram). On the downstream side of the entry position, there is a submerged weir [fireproof wall 3a having a large number of molten steel passage holes P].

３ｂを、それぞれの間に空間部４が形成される様に配設
したちの１が、タンディツシュｌの底面に接して設けら
れており、且つ該空間部４の下面位置には不活性ガス吹
込み用のポーラスプラグ６（１つだけでもよく或は複数
個を紙面貫通方向に並設してもよい）が設けられている
。溶鋼鍋７から注入管２を経てタンディツシュｌ内へ注
入された溶鋼Ｍ（このときの溶鋼温度は、最適の鋳造開
始温度よりも若干高めに設定しておく）は、実線矢印で
示す如く耐火壁３ａ、３ｂ及び空間部４を通過した後、
越流堰から注出口９を経て鋳型１０へ順次鋳込まれてい
く０図中１２は溶融フラックスを示す。3b are arranged so that a space 4 is formed between them, and one of them is provided in contact with the bottom surface of the tundish l, and an inert gas blower is provided at the bottom of the space 4. A porous plug 6 for insertion (only one plug may be used, or a plurality of plugs may be arranged in parallel in the penetrating direction of the paper) is provided. The molten steel M injected into the tundish l from the molten steel ladle 7 via the injection pipe 2 (the molten steel temperature at this time is set slightly higher than the optimal casting start temperature) is poured into the refractory wall as shown by the solid line arrow. After passing through 3a, 3b and space 4,
12 in Figure 0 indicates the molten flux that is sequentially poured from the overflow weir into the mold 10 via the spout 9.

ここで本発明においては、空間部４を通過中の溶鋼Ｍに
、ポーラスプラグ６から不活性ガスを吹込み、該不活性
ガスの吹込み量を調整することによって該溶鋼Ｍを所定
の温度まで降温させ、降温した溶鋼Ｍは順次耐火壁３ｂ
から下流側へ流れていく、尚空間部４に吹込まれた不活
性ガスは該空間部４にしばらくの間滞留して該空間部４
内の溶鋼Ｍと効率良く接触し、溶鋼Ｍの降温に十分寄与
した後、前後の耐火壁３ａ、３ｂから上方へ浮上してい
く、従って単にタンディツシュの低部から不活性ガスを
吹込むだけの従来法に比べると、溶鋼Ｍと不活性ガスの
接触時間が著しく延長され。In the present invention, inert gas is blown into the molten steel M passing through the space 4 from the porous plug 6, and the molten steel M is heated to a predetermined temperature by adjusting the amount of the inert gas blown into the molten steel M. The temperature of the molten steel M is lowered, and the cooled molten steel M is sequentially heated to the fireproof wall 3b.
The inert gas blown into the space 4 remains in the space 4 for a while and flows downstream from the space 4.
After making efficient contact with the molten steel M in the tundish and sufficiently contributing to lowering the temperature of the molten steel M, the molten steel M floats upward from the front and rear fireproof walls 3a and 3b. Compared to the conventional method, the contact time between the molten steel M and the inert gas is significantly extended.

それにイ↑って不活性ガスによる冷却効果を大幅に高め
ることができる。その結果、溶鋼Ｍを一定温度降下させ
るのに要する不活性ガスの吹込み量を大幅に低減するこ
とができ、しかも不活性ガス吹込み量を低減させる分だ
けポーラスプラグ６の数を減少し、或はサイズを小さく
することができ、従来例で指摘した様なタンディツシュ
強度の劣化或は溶鋼の漏出といった問題を抑制すること
ができる。また溶鋼Ｍ中に混入している非金属介在物は
、不活性ガスの吹込みにより浮上分離し易くなることが
確認されているが１本発明によれば前述の様に溶鋼Ｍと
不活性ガスの接触効率が高められるので、非金属介在物
の除去も促進される。また溶鋼鍋７から注入されたすべ
ての溶鋼Ｍは潜り堰５の前記空間部４を通過する過程で
刃傷なく不活性ガスと接触するので、不活性ガスの吹込
み量を適正にコントロールすることによって溶鋼Ｍの鋳
込み温度を高精度で一定に維持することができる。In addition, the cooling effect of the inert gas can be greatly enhanced. As a result, the amount of inert gas blown into the molten steel M required to lower the temperature to a certain level can be significantly reduced, and the number of porous plugs 6 can be reduced by the amount of inert gas blown into the molten steel M. Alternatively, the size can be reduced, and problems such as deterioration of tundish strength or leakage of molten steel, as pointed out in the conventional example, can be suppressed. In addition, it has been confirmed that non-metallic inclusions mixed in molten steel M are easily floated and separated by injecting inert gas. Since the contact efficiency is increased, the removal of nonmetallic inclusions is also facilitated. In addition, all the molten steel M injected from the molten steel ladle 7 comes into contact with the inert gas without any scratches during the process of passing through the space 4 of the submerged weir 5, so by appropriately controlling the amount of inert gas blown into the weir 5. The casting temperature of the molten steel M can be maintained constant with high precision.

第２図は本発明で使用する潜り堰５を拡大して示す一部
切除見取り図であり、多数の溶鋼通過孔Ｐの穿設された
耐火物壁３ｂが、適当な空間部４が形成される様に対峙
して配置されている。尚第１図の例からも明らかな様に
被処理溶鋼は耐火壁３ａの溶鋼通過孔Ｐがら空間部４へ
流入して不活性ガスと接触した後、耐火壁３ｂの溶鋼通
過孔Ｐから下流側へ流出して行くものであり、こうした
溶鋼流のため、ポーラスプラグ６から吹込まれた不活性
ガス泡は、耐火壁３ｂの溶鋼通過孔Ｐから短時間のうち
に流出して行く傾向がある。従って空間部４内における
不活性ガスの滞留時間を長くして冷却効率を高めるうえ
では、下流側に配設される耐火壁３ｂの流通抵抗を若干
大きくしておくのが有利である。この為第２図では耐火
壁３ｂとして２枚の耐火壁を重ね合わせ、しかも第３図
の一部断面図に示す如く夫々の溶鋼通過孔Ｐ、Ｐが互い
に交錯し合う様に千鳥状に配列し、全体としての流通抵
抗を高めている。但し流通抵抗を高める手段はこれに限
定される訳ではなく、溶鋼通過孔Ｐの孔径を小さくした
り或は穿設数を少なくする等の手段で対処することも勿
論可能である。FIG. 2 is a partially cutaway diagram showing an enlarged submerged weir 5 used in the present invention, in which a refractory wall 3b with a large number of molten steel passage holes P is formed to form an appropriate space 4. They are placed facing each other. As is clear from the example shown in Fig. 1, the molten steel to be treated flows into the space 4 through the molten steel passage hole P of the fireproof wall 3a, contacts the inert gas, and then flows downstream from the molten steel passage hole P of the fireproof wall 3b. Because of this molten steel flow, the inert gas bubbles blown from the porous plug 6 tend to flow out from the molten steel passage hole P of the fireproof wall 3b in a short time. . Therefore, in order to increase the cooling efficiency by increasing the residence time of the inert gas in the space 4, it is advantageous to slightly increase the flow resistance of the fireproof wall 3b disposed on the downstream side. For this reason, in Fig. 2, two fireproof walls are overlapped as the fireproof wall 3b, and as shown in the partial cross-sectional view of Fig. 3, the respective molten steel passing holes P, P are arranged in a staggered manner so that they intersect with each other. This increases overall distribution resistance. However, the means for increasing the flow resistance is not limited to this, and it is of course possible to take measures such as reducing the diameter of the molten steel passage hole P or reducing the number of holes formed.

尚本発明で特徴付けられる潜り堰５の構成、即ち耐火壁
３ａ、３ｂの厚さ、溶鋼通過孔Ｐの大きさや孔数、或は
空間部４の容積等は、溶鋼Ｍの降温量や流量等に応じて
適宜選択して決定すべきものであり、−律に定めること
はできない、また耐火壁の材質も特に制限はないが、一
般的なのはアルミナ−カーボン質、高アルミナ質、石灰
質、マグネシア質、ジルコニア質あるいはマグネシア−
カーボン質等である。また上記ではタンディツシュ内に
おける温度調整の例を挙げて説明したが、この他溶鋼注
入樋等に同様の潜り堰を設けて温度調整を行なうことも
勿論可能である。The configuration of the submerged weir 5 characterized by the present invention, that is, the thickness of the fireproof walls 3a and 3b, the size and number of molten steel passage holes P, the volume of the space 4, etc., depends on the temperature drop and flow rate of the molten steel M. The material should be selected and determined as appropriate depending on the situation, etc., and cannot be set by law.Also, there are no particular restrictions on the material of the fireproof wall, but common materials include alumina-carbon, high alumina, calcareous, and magnesia. , zirconia or magnesia
Carbon quality etc. Moreover, although the above explanation has been given by giving an example of temperature adjustment in the tundish, it is of course possible to provide a similar submerged weir in the molten steel injection trough or the like to perform temperature adjustment.

［実施例］ ８０トン転炉にて溶製し、温度を鋳造開始目標温度（１
５２０〜１５４０℃）よりも５０〜６０℃高温に調整し
た溶鋼（０，８％Ｃの低合金鋼）を、第１〜３図に準じ
て設計した潜り堰を配置した小型タンディツシュに通し
、空間部の底部に設けた３個のポーラスプラグからの不
活性ガス吹込み量を調整（プラグ１個当たり１０〜６０
見／ｌｌ１ｎ　）することによって鋳造開始温度を可及
的一定に維持しながら連続鋳造を行ない、鋳込み温度の
変化及び鋳片の中心偏析の程度を調べた。[Example] Melting was carried out in an 80-ton converter, and the temperature was set to the casting start target temperature (1
Molten steel (0.8% C low alloy steel) adjusted to a temperature of 50 to 60 degrees Celsius (520 to 1,540 degrees Celsius) is passed through a small tundish equipped with a submerged weir designed according to Figures 1 to 3. Adjust the amount of inert gas blown from the three porous plugs installed at the bottom of the unit (10 to 600 gas per plug)
Continuous casting was carried out while keeping the casting start temperature as constant as possible, and the change in casting temperature and the degree of center segregation of the slab were investigated.

尚処理条件は下記の通りとした。The processing conditions were as follows.

く処理条件〉 潜り堰の構成 耐火壁の材質：Ａｌ２Ｏ３・・・９２〜９３％、５ｉＯ
ｚ・・・１〜２％、Ｃ・・・４ 〜５％ 耐火壁寸法　：　７５Ｇ　ｍ曽Ｘ９５０　ｓｓＸ　１２
Ｇ　ａｍ溶鋼通過孔　二８０■φ×６個×４段 耐火壁３ａ　　：１枚 耐火壁３ｂ　：１枚重ね 空間部厚さ　：３０層■ タンディツシュ容量＝１８トン タンディツシュ及び潜り堰の 予熱温度　：８００℃ 不活性ガス　：アルゴン、プラグ１個当たり１０〜６０
１／分 鋳造速度　　：０．５ｍ／ｗｉｎ 尚具体的な温度調整に当たっては、タンディツシュへの
溶鋼注入初期は溶鋼熱がタンディツシュ及び潜り堰の昇
温に消費されて溶鋼温度が降下する為、不活性ガス吹込
み量を最小限に抑え、注入の中期には溶鋼温度が最も高
くなる為不活性ガス吹込量を増大することによって昇温
を抑え、注入の末期には溶鋼温度が放熱により徐々に低
下してくるので、降温量に応じて不活性ガス吹込み量を
徐々に減少することによって鋳造開始温度を一定に保っ
た。Treatment conditions〉 Composition of submerged weir Material of fireproof wall: Al2O3...92-93%, 5iO
Z...1~2%, C...4~5% Fireproof wall dimensions: 75G msoX950 ssX 12
G am molten steel passage hole 280■ φ x 6 pieces x 4 stages Fireproof wall 3a: 1 layer Fireproof wall 3b: 1 layer Space thickness: 30 layers■ Tundish capacity = 18 tons Preheating temperature of tundish and submerged weir: 800℃ Inert gas: Argon, 10 to 60 per plug
1/min casting speed: 0.5m/win When specifically adjusting the temperature, in the early stage of pouring molten steel into the tundish, the heat of the molten steel is consumed to raise the temperature of the tundish and the submerged weir, and the temperature of the molten steel decreases. The amount of gas blown is kept to a minimum, and since the molten steel temperature reaches its highest during the middle stage of injection, the temperature rise is suppressed by increasing the amount of inert gas blown in. At the end of the injection, the molten steel temperature gradually decreases due to heat radiation. Therefore, the casting start temperature was kept constant by gradually decreasing the amount of inert gas blown in according to the amount of temperature drop.

この間の鋳造開始温度の変化を第４図に示す。Figure 4 shows the change in casting start temperature during this period.

また比較の為、不活性ガス吹込みによる温度調整を省略
した他は上記と同様にして鋳造を行なった場合の鋳造開
始温度の変化を第４図［破線（イ）（ロ）Ｊに併記する
。For comparison, Figure 4 shows the change in casting start temperature when casting was carried out in the same manner as above, except that the temperature adjustment by inert gas injection was omitted. .

第４図からも明らかな様に１本発明の方法を採用すれば
タンディツシュ等の吸熱を終えた中期以降における鋳造
開始温度の変化を２０℃以内に抑えることができる。こ
れに対し比較例では中期以降の鋳造開始温度が比較的安
定した後でも、その温度は３０〜４０℃の範囲で変動し
ている。As is clear from FIG. 4, if the method of the present invention is adopted, it is possible to suppress the change in the casting start temperature to within 20° C. after the middle stage after the heat absorption of the tandish etc. is completed. On the other hand, in the comparative example, even after the casting start temperature becomes relatively stable after the middle stage, the temperature fluctuates in the range of 30 to 40°C.

尚第５図は、上記と同じ低合金鋼を使用した場合におけ
る鋳造開始時溶湯温度（液相温度との温度差ΔＴで表示
）と鋳片の中心偏析指数の関係を示したグラフであり、
連続鋳造時における上記温度差ΔＴが大きくなるに従っ
て、鋳片のＣの中心偏析指数は大幅に高くなる傾向が見
られる。この点本発明法を採用すれば前記温度差を２０
℃程度以下に抑えることができるのでＣの中心偏析が最
小限に抑えられ、均質で表面正常の良好な鋳片を安定し
て製造することができる。FIG. 5 is a graph showing the relationship between the molten metal temperature at the start of casting (expressed as the temperature difference ΔT from the liquidus temperature) and the center segregation index of the slab when the same low alloy steel as above is used.
As the temperature difference ΔT during continuous casting increases, the central segregation index of C in the slab tends to increase significantly. In this regard, if the method of the present invention is adopted, the temperature difference can be reduced by 20
Since the temperature can be suppressed to about .degree. C. or less, central segregation of C can be minimized, and slabs with good homogeneity and surface normality can be stably produced.

こうした傾向を本発明に照らして考えてみると１本発明
では前述の如く比較的少量の不活性ガス吹込みで溶鋼の
温度を狭い温度範囲で可及的一定に維持することができ
る為、ΔＴの変動による内部品質の変動を最小限に抑え
ることができる。Considering these trends in the light of the present invention, 1. As mentioned above, in the present invention, the temperature of molten steel can be maintained as constant as possible within a narrow temperature range by injecting a relatively small amount of inert gas, so ΔT Variations in internal quality due to variations in quality can be minimized.

しかも溶鋼温度の変動を少なくし得るところから、鋳込
み温度を当該溶鋼の液相線温度に近ずけることができ（
即ちΔＴを小さくすることができ）、に＆分偏析自体を
最小限に抑えることができる。Moreover, since fluctuations in the molten steel temperature can be reduced, the casting temperature can be brought closer to the liquidus temperature of the molten steel (
In other words, ΔT can be made small), and the segregation itself can be minimized.

［発明の効果］ 本発明は以上の様に構成されるが、要は溶鋼流路に設け
た特殊な潜り堰に不活性ガスを吹込み、溶鋼の温度調整
を行なう様にしたから、不活性ガスと溶鋼の接触効率を
最大限に高めることができ、比較的少ない不活性ガス吹
込み量で溶鋼の鋳込み開始温度を安定に維持し、殊に鋳
造初期および末期の低温Ｐｊ造による鋳片の不良率を低
減し得ることになった。その結果鋳片の内部品質を一定
に保つことができるばかりでなく、鋳込み温度を当該溶
鋼の液相線温度に近ずけることが回部となり、成分偏析
等のない良質の鋳片を製造し得ることになった。[Effect of the invention] The present invention is constructed as described above, but the point is that inert gas is blown into a special submerged weir provided in the molten steel flow path to adjust the temperature of the molten steel. The contact efficiency between gas and molten steel can be maximized, and the casting start temperature of molten steel can be maintained stably with a relatively small amount of inert gas injection. This made it possible to reduce the defective rate. As a result, not only can the internal quality of the slab be kept constant, but also the casting temperature can be brought close to the liquidus temperature of the molten steel, producing high-quality slabs without component segregation. I ended up getting it.

【図面の簡単な説明】[Brief explanation of the drawing]

第１図は本発明の実施例を示す概略縦断面図。 第２図は本発明で使用される潜り堰を例示する−部破断
見取り図、第３図は該潜り堰の耐火壁を例示する一部断
面図、第４図は実施例で得た鋳造開始温度の変化を従来
例と対比して示すグラフ、第５図は、溶湯の液相線温度
と鋳造開始温度の差（ΔＴ）が鋳片の中心偏析に与える
影響を示すグラフである。 ｌ・・・タンディツシュ　　２・・・注入管３ａ、３ｂ
・・・耐火壁　　４・・・空間部５・・・潜り堰　　　
　　　６・・・ポーラスプラグＰ・・・溶鋼通過孔　　
　　ｌＯ・・・鋳型第４図 第５図 −Ｔ■）FIG. 1 is a schematic vertical sectional view showing an embodiment of the present invention. Fig. 2 is a partial cutaway diagram illustrating the submerged weir used in the present invention, Fig. 3 is a partial sectional view illustrating the fireproof wall of the submerged weir, and Fig. 4 is the casting start temperature obtained in the example. FIG. 5 is a graph showing the influence of the difference (ΔT) between the liquidus temperature of the molten metal and the casting start temperature on the center segregation of the slab. l...Tandish 2...Injection pipes 3a, 3b
... Fireproof wall 4 ... Space 5 ... Submerged weir
6... Porous plug P... Molten steel passage hole
lO...Mold Figure 4 Figure 5-T■)

Claims (1)

【特許請求の範囲】[Claims] 多数の金属溶湯通過孔を有する一対の耐火壁の間に空間
部を形成してなる潜り堰を、連続鋳造用金属溶湯流路の
底面に接して立設し、該潜り堰の前記空間部を通過する
金属溶湯に不活性ガスを吹込むと共に、該不活性ガスの
吹込み量を調整することによって金属溶湯の温度を一定
の範囲にコントロールすることを特徴とする、連続鋳造
用金属溶湯の温度制御方法。A submerged weir formed by forming a space between a pair of fireproof walls having a large number of molten metal passing holes is erected in contact with the bottom of a molten metal flow channel for continuous casting, and the space of the submerged weir is Temperature of molten metal for continuous casting, characterized in that the temperature of the molten metal is controlled within a certain range by blowing an inert gas into the molten metal passing through and adjusting the amount of inert gas blown into the molten metal. Control method.