JP5292853B2 - Vacuum degassing apparatus for molten steel and vacuum degassing refining method - Google Patents

Vacuum degassing apparatus for molten steel and vacuum degassing refining method Download PDF

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JP5292853B2
JP5292853B2 JP2008049062A JP2008049062A JP5292853B2 JP 5292853 B2 JP5292853 B2 JP 5292853B2 JP 2008049062 A JP2008049062 A JP 2008049062A JP 2008049062 A JP2008049062 A JP 2008049062A JP 5292853 B2 JP5292853 B2 JP 5292853B2
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molten steel
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ladle
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JP2009203539A (en
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由枝 中井
郁宏 鷲見
誠司 鍋島
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JFE Steel Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a vacuum-degassing treating apparatus capable of increasing the circulation amount of molten steel, increasing the degassing refining reaction rate, and shortening the treatment time while any new device need not be installed, and the treatment cost is not increased when refining molten steel by using the vacuum-degassing treating apparatus having two immersion tubes such as an RH vacuum-degassing treating apparatus. <P>SOLUTION: The vacuum-degassing treating apparatus 1 has two immersion tubes of a rising side immersion tube 8 for guiding molten steel 3 in a ladle 2 into the degassing tank, and a descending side immersion tube 9 for returning molten steel treated in the degassing tank from the degassing tank to the ladle below a degassing tank 5. The inside diameter (Dd) of the descending side immersion tube is larger than the inside diameter (Du) of the ascending side immersion tube in a range satisfying inequalities (1): Du&lt;Dd&lt;1.4&times;Du, where Du denotes the inside diameter of the ascending side immersion tube and Du denotes the inside diameter of the descending side immersion tube. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

本発明は、取鍋内の溶鋼を脱ガス槽内に導くための上昇側浸漬管と、脱ガス槽で処理した溶鋼を脱ガス槽から取鍋へ戻すための下降側浸漬管とを有する溶鋼の真空脱ガス処理装置、並びに、この真空脱ガス処理装置を用いた溶鋼の真空脱ガス精錬方法に関するものである。   The present invention is a molten steel having an ascending side dip tube for guiding the molten steel in the ladle into the degassing tank and a descending side dip tube for returning the molten steel treated in the degassing tank from the degassing tank to the ladle. The present invention relates to a vacuum degassing apparatus and a vacuum degassing refining method for molten steel using the vacuum degassing apparatus.

鋼材の高級化並びにその需要の多様化に伴い、真空脱ガス処理を要する鋼種及び数量は益々増加する傾向にあり、真空脱ガス処理に要する時間を短縮することによって、脱ガス処理能力の向上並びに転炉からの出鋼時の溶鋼温度低下による製造コストの削減が強く望まれる状況にある。   Steel grades and quantities that require vacuum degassing tend to increase with the upgrading of steel materials and diversification of demands. By reducing the time required for vacuum degassing, the degassing capacity can be improved and There is a strong demand for a reduction in manufacturing cost due to a drop in molten steel temperature when steel is output from a converter.

このような状況下、真空脱ガス処理設備としては、処理能力に優れることから、RH真空脱ガス装置が広く使用されている。このRH真空脱ガス装置は、溶鋼を減圧下で処理するための脱ガス槽の下部に2本の浸漬管を有し、一方を上昇側浸漬管、他方を下降側浸漬管として、これら2本の浸漬管を取鍋内の溶鋼に浸漬させ、脱ガス槽内を減圧することにより、上昇側浸漬管から吹き込む不活性ガスによるガスリフト効果を利用して取鍋内の溶鋼を上昇側浸漬管から脱ガス槽に導き、脱ガス槽内で溶鋼を減圧下に曝して精錬し、その後、溶鋼を下降側浸漬管から取鍋に戻し、この循環を連続して実施して、溶鋼に脱ガス精錬を施すという装置である。取鍋から脱ガス槽を循環する溶鋼の流れを「環流」と呼んでいる。   Under such circumstances, the RH vacuum degassing apparatus is widely used as the vacuum degassing processing equipment because of its excellent processing capability. This RH vacuum degassing apparatus has two dip pipes in the lower part of a degassing tank for treating molten steel under reduced pressure, one as an ascending side dip pipe and the other as a descending side dip pipe. By immersing the dip tube in the molten steel in the ladle and reducing the pressure in the degassing tank, the molten steel in the ladle is removed from the ascending side dip tube using the gas lift effect of the inert gas blown from the ascending side dip tube. Guided to degassing tank, refining by exposing molten steel under reduced pressure in degassing tank, then returning molten steel from descending dip tube to ladle and continuously performing this circulation to degas refining to molten steel It is a device that applies. The flow of molten steel that circulates from the ladle to the degassing tank is called “circular flow”.

RH真空脱ガス装置では、溶鋼の減圧下での脱炭精錬、取鍋と脱ガス槽とを循環する溶鋼に脱硫剤を添加して行う脱硫精錬、溶鋼中の窒素や水素などのガス成分を減圧下で除去するガス成分除去精錬、更には、強攪拌を利用した、溶鋼中に懸濁する非金属介在物の分離除去精錬が行われている。つまり、溶鋼中の不純物成分を除去し、高純度で高清浄性の溶鋼を溶製する目的で使用されている。これらの精錬において、不純物成分を速やかに除去するには、単位時間当りの還流する溶鋼量(「環流量」という)を増加させることが効果的であり、そのために、環流量を増加させるための手段が多数提案されている。   In RH vacuum degassing equipment, decarburization refining of molten steel under reduced pressure, desulfurization refining performed by adding a desulfurizing agent to molten steel circulating in the ladle and degassing tank, and gas components such as nitrogen and hydrogen in the molten steel Gas component removal refining to be removed under reduced pressure, and further separation and refining of nonmetallic inclusions suspended in molten steel using strong stirring are performed. In other words, it is used for the purpose of removing high-purity and high-cleanness molten steel by removing impurity components in the molten steel. In these refining, it is effective to increase the amount of molten steel recirculating per unit time (referred to as “annular flow rate”) in order to quickly remove impurity components. Many means have been proposed.

例えば、特許文献1には、200℃ないし1000℃に加熱した、脱ガス槽の真空度及び上昇側浸漬管の内径から定められる所定量の不活性ガスを0.5MPa以上の圧力で上昇側浸漬管に吹き込んで行う真空脱ガス処理方法が提案されている。しかし、この方法では、不活性ガスを加熱するための設備が必要であり、これにより処理コストが上昇するという問題点がある。   For example, Patent Document 1 discloses that a predetermined amount of inert gas heated to 200 ° C. to 1000 ° C. and determined from the degree of vacuum of the degassing tank and the inner diameter of the rising side dip tube is immersed on the rising side at a pressure of 0.5 MPa or more. There has been proposed a vacuum degassing method performed by blowing into a tube. However, this method requires a facility for heating the inert gas, which increases the processing cost.

特許文献2には、脱ガス槽を下方に延長して下向きに開口した外側浸漬筒を設け、この外側浸漬筒の内部に同心に上下方向に開口した内側浸漬筒を配設し、内側浸漬筒に設けた環流用ガス吹き込み口からArガスを吹き込んで溶鋼を上昇させ、一方、内側浸漬筒と外側浸漬筒との間隙を溶鋼の下降流路とする、溶鋼の環流量を増大させた真空脱ガス処理装置が提案されている。しかし、この装置では、内側浸漬筒と外側浸漬筒とが必要であり、装置が複雑になるばかりでなく、耐火物などの使用する資材が多くなり、これにより処理コストが上昇するという問題点がある。   Patent Document 2 includes an outer immersion cylinder that extends downward from the degassing tank and opens downward, and an inner immersion cylinder that opens concentrically in the vertical direction is disposed inside the outer immersion cylinder. The vacuum degassing with an increased flow rate of the molten steel, with Ar gas being blown from the circulating gas blowing port provided in the upper part of the molten steel to raise the molten steel, while the gap between the inner and outer immersed cylinders is used as a downward flow path of the molten steel. Gas processing devices have been proposed. However, this apparatus requires an inner immersion cylinder and an outer immersion cylinder, which not only complicates the apparatus but also increases the amount of materials used such as refractories, which increases the processing cost. is there.

特許文献3には、RH真空脱ガス装置において、上昇側浸漬管の下端部の内径を下向きに拡大させることが提案されている。しかし、この方法では、上昇側浸漬管の形状が複雑になり、複雑であることから使用中の熱応力により亀裂が発生しやすく、耐火物の寿命が短くなり、補修時間が多くなるなどの操業阻害が生ずるのみならず、処理コストも高くなるという問題点がある。   Patent Document 3 proposes that in the RH vacuum degassing apparatus, the inner diameter of the lower end portion of the ascending-side dip tube is expanded downward. However, this method complicates the shape of the ascending side dip tube, so that it is prone to cracking due to thermal stress during use, shortening the life of the refractory and increasing repair time. There is a problem that not only the inhibition occurs but also the processing cost becomes high.

特許文献4には、上昇側浸漬管の直下位置に相当する取鍋底部にポーラス煉瓦を配置し、このポーラス煉瓦から不活性ガスを吹き込み、上昇側浸漬管に吹き込む環流用ガスによる環流を強化する方法が提案されている。しかし、この方法では、取鍋に別途ポーラス煉瓦を設置する必要があり、これにより処理コストが上昇するという問題点がある。   In Patent Document 4, a porous brick is arranged at the bottom of the ladle corresponding to the position directly below the ascending side dip pipe, an inert gas is blown from the porous brick, and the recirculation by the recirculation gas blown into the ascending side dip pipe is reinforced. A method has been proposed. However, in this method, it is necessary to separately install a porous brick in the ladle, which causes a problem that the processing cost increases.

特許文献5には、上昇側浸漬管に配置する環流用ガス吹き込み管を、内部に向かって斜め上向きとなるように配置することが提案されている。環流用不活性ガスは溶鋼に対して比重が極めて小さく、水平方向に吹き込んだ場合も環流用不活性ガスは直ちに上向き方向に移動することから、単に斜め上向きに吹き込む上記方法のみでは、環流量の大幅な増加は期待できない。   Patent Document 5 proposes that the reflux gas blowing tube disposed in the ascending-side dip tube is disposed so as to be obliquely upward toward the inside. The inert gas for recirculation has a very low specific gravity with respect to the molten steel, and even when blown in the horizontal direction, the inert gas for recirculation immediately moves in the upward direction. A significant increase cannot be expected.

また、特許文献6には、上昇側浸漬管に設置される環流用ガス吹き込み口の近傍の浸漬管内周面に超音波加振子を配置し、この超音波加振子によって環流用ガス吹き込み口から吹き込まれた不活性ガスの気泡を微細化することが提案されている。しかし、この方法では、超音波加振子や超音波発信装置が必要であり、これにより処理コストが上昇するという問題点がある。   Further, in Patent Document 6, an ultrasonic exciter is disposed on the inner peripheral surface of the dip pipe in the vicinity of the reflux gas blowing port installed in the ascending side dip pipe, and the ultrasonic shaker blows from the reflux gas blow inlet. It has been proposed to refine the inert gas bubbles. However, this method requires an ultrasonic exciter and an ultrasonic transmission device, which increases the processing cost.

ところで、RH真空脱ガス装置における環流量は、一般的に下記の(2)式で計算されることが多い。
Q=11.4×G1/3×D4/3×[ln(P1/P2)]1/3…(2)
但し、(2)式において、Qは溶鋼環流量(トン/min)、Gは環流用ガス流量(NL/min)、Dは浸漬管内径(m)、P1は大気圧(Pa)、P2は脱ガス槽内圧力(Pa)である。
By the way, the ring flow rate in the RH vacuum degassing apparatus is generally calculated by the following equation (2).
Q = 11.4 × G 1/3 × D 4/3 × [ln (P 1 / P 2 )] 1/3 (2)
However, in the formula (2), Q is the flow rate of molten steel (ton / min), G is the flow rate of circulating gas (NL / min), D is the inner diameter of the dip tube (m), P 1 is atmospheric pressure (Pa), P 2 is the degassing tank internal pressure (Pa).

(2)式において、浸漬管内径(D)のべき数は、環流用ガス流量(G)のべき数に較べて大きいことから、溶鋼環流量の増加には、浸漬管内径(D)を拡大した方が環流用ガス流量(G)を増加することよりも効果のあることが明らかであり、一般に、脱ガス精錬の反応効率を向上させる手段として、溶鋼環流量を増大させるべく、浸漬管の内径を拡大することが行われている。   In equation (2), the power of the dip tube inner diameter (D) is larger than the power of the reflux gas flow rate (G), so the dip tube inner diameter (D) is expanded to increase the molten steel ring flow rate. It is clear that this is more effective than increasing the reflux gas flow rate (G). In general, as a means of improving the reaction efficiency of degassing refining, in order to increase the molten steel ring flow rate, Enlarging the inner diameter is performed.

しかしながら、RH真空脱ガス装置は、上昇側浸漬管及び下降側浸漬管を脱ガス槽の下部に並べて設置する必要があり、浸漬管を構成する耐火物の厚みを考慮すると、浸漬管の内径は必然的に脱ガス槽の内径の1/2未満になる。このため、浸漬管の断面積は、脱ガス槽の断面積の1/4より小さくなる。一方、脱ガス槽の内径は、脱ガス精錬中に脱ガス槽の下端部を取鍋の上端位置よりも取鍋内部側に挿入させる必要があることから、自ずと取鍋の内径に制約を受ける。   However, in the RH vacuum degassing apparatus, it is necessary to arrange the ascending-side dip tube and the descending-side dip tube in the lower part of the degassing tank, and considering the thickness of the refractory constituting the dip tube, the inner diameter of the dip tube is Naturally, it becomes less than 1/2 of the inner diameter of the degassing tank. For this reason, the cross-sectional area of a dip tube becomes smaller than 1/4 of the cross-sectional area of a degassing tank. On the other hand, the inner diameter of the degassing tank is naturally limited by the inner diameter of the ladle because it is necessary to insert the lower end of the degassing tank to the inner side of the ladle from the upper end position of the ladle during degassing refining. .

このような事情から、上昇側浸漬管及び下降側浸漬管ともに、内径拡大による環流量の向上は限界に達しているのが実情である。
特開2007−31820号公報 特開平8−269534号公報 特開平7−150225号公報 特開平4−131316号公報 特開平5−1319号公報 特開平2−173205号公報
Under such circumstances, the actual situation is that the improvement of the ring flow rate due to the expansion of the inner diameter has reached the limit in both the ascending side dip tube and the descending side dip tube.
JP 2007-31820 A JP-A-8-269534 Japanese Patent Laid-Open No. 7-150225 JP-A-4-131316 JP-A-5-1319 Japanese Patent Laid-Open No. 2-173205

上記説明のように、従来、RH真空脱ガス装置において、環流量を増大させるための手段が多数提案されているが、何れも新たな装置を設置する必要があったり、装置の形状が複雑になったり、或いは、耐火物寿命が短くなったりするなどによって、処理コストの上昇を余儀なくされていた。   As described above, conventionally, in the RH vacuum degassing apparatus, many means for increasing the ring flow rate have been proposed, but any of them requires installation of a new apparatus or the shape of the apparatus is complicated. As a result, or the life of the refractory is shortened, the processing cost has been increased.

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、RH真空脱ガス装置のような2本の浸漬管を有する真空脱ガス処理装置を用いて溶鋼の精錬を行うに際し、新たな装置を設置する必要がなく、処理コストの上昇を招くことなく、溶鋼の環流量を増大させ、脱ガス精錬反応速度の向上並びに処理時間の短縮を達成することのできる真空脱ガス処理装置を提供することであり、且つ、当該真空脱ガス処理装置を使用した真空脱ガス精錬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 its object is to refine a molten steel using a vacuum degassing apparatus having two dip tubes such as an RH vacuum degassing apparatus, Vacuum degassing equipment that can increase the flow rate of molten steel, increase the degassing refining reaction rate, and shorten the processing time without the need to install new equipment And a vacuum degassing refining method using the vacuum degassing apparatus.

上記課題を解決するための第1の発明に係る溶鋼の真空脱ガス処理装置は、脱ガス槽の下部に、取鍋内の溶鋼を脱ガス槽内に導くための上昇側浸漬管と、脱ガス槽で処理した溶鋼を脱ガス槽から取鍋へ戻すための下降側浸漬管との2本の浸漬管を有する真空脱ガス処理装置において、前記上昇側浸漬管の内径(Du)と前記下降側浸漬管の内径(Dd)とが下記の(1)式の関係の範囲内で、下降側浸漬管の内径(Dd)が上昇側浸漬管の内径(Du)よりも大きいことを特徴とする。
Du<Dd<1.4×Du …(1)
また、第2の発明に係る溶鋼の真空脱ガス精錬方法は、第1の発明に記載の溶鋼の真空脱ガス処理装置を用い、前記上昇側浸漬管によって取鍋内の溶鋼を脱ガス槽に導入すると同時に、前記下降側浸漬管によって脱ガス槽内の溶鋼を取鍋内に排出させ、かくして取鍋内の溶鋼を取鍋と脱ガス槽との間で環流させながら精錬することを特徴とする。
A vacuum degassing apparatus for molten steel according to a first aspect of the present invention for solving the above-described problems includes a rising side dip tube for guiding the molten steel in the ladle into the degassing tank, a degassing tank at the bottom of the degassing tank, In a vacuum degassing apparatus having two dip pipes, a dipping side dip pipe for returning molten steel treated in a gas tank from a degas tank to a ladle, the inner diameter (Du) of the rise side dip pipe and the descent The inner diameter (Dd) of the descending side dip tube is larger than the inner diameter (Du) of the rising side dip tube, with the inner diameter (Dd) of the side dip tube being within the range of the relationship of the following equation (1). .
Du <Dd <1.4 × Du (1)
Moreover, the vacuum degassing refining method of the molten steel which concerns on 2nd invention uses the vacuum degassing processing apparatus of the molten steel as described in 1st invention, The molten steel in a ladle is made into a degassing tank by the said rising side dip tube. At the same time as introducing, the molten steel in the degassing tank is discharged into the ladle by the descending side dip pipe, and thus the molten steel in the ladle is refined while being recirculated between the ladle and the degassing tank. To do.

本発明によれば、下降側浸漬管の内径を上昇側浸漬管の内径に対して所定の範囲内で大きくするので、下降側環流管における流れに対する抵抗が最小となり、新たな装置を設置しなくとも、溶鋼の環流量を増大させることができる。その結果、脱ガス精錬反応速度の向上並びに処理時間の短縮が可能となり、大幅な処理コストの削減が達成される。   According to the present invention, since the inner diameter of the descending dip tube is increased within a predetermined range with respect to the inner diameter of the ascending dip tube, the resistance to the flow in the descending reflux tube is minimized, and no new device is installed. In both cases, the flow rate of the molten steel can be increased. As a result, the degassing refining reaction rate can be improved and the processing time can be shortened, and the processing cost can be greatly reduced.

以下、本発明を具体的に説明する。先ず、本発明に至った経緯を説明する。   Hereinafter, the present invention will be specifically described. First, the background to the present invention will be described.

本発明者等は、上昇側浸漬管及び下降側浸漬管の2本の浸漬管を有する真空脱ガス処理装置として最も代表的な装置であるRH真空脱ガス装置において、取鍋と脱ガス槽とを還流する溶鋼の環流量を増加させることを研究・検討した。その結果、上昇側浸漬管と下降側浸漬管とが同一の内径の場合には、下降側浸漬管における溶鋼の流れが、装置全体の環流量の律速となっていることを知見した。   In the RH vacuum degassing apparatus which is the most representative apparatus as a vacuum degassing apparatus having two dip pipes, an ascending side dip pipe and a descending side dip pipe, the ladle, degassing tank, The research and examination of increasing the ring flow rate of molten steel refluxing the steel. As a result, it was found that when the ascending-side dip tube and the descending-side dip tube have the same inner diameter, the flow of the molten steel in the descending-side dip tube is the rate-limiting factor for the entire apparatus.

そこで、下降側浸漬管の内径を上昇側浸漬管の内径よりも大きくする方向で、それぞれの浸漬管の内径を変化させて環流量を測定した。その結果、下降側浸漬管の内径を上昇側浸漬管の内径よりも大きくすることにより、環流量が増加することを確認した。しかしながら、下降側浸漬管の内径を大きくし過ぎると、具体的には、上昇側環流管の内径の1.4倍を超える内径に拡大すると、逆に、還流量は、内径が同一であった場合よりも減少することを確認した。そして、最も環流量が増加するのは、下降側浸漬管の内径を上昇側浸漬管の内径の約1.15〜1.25倍とする範囲であることも分かった。   Therefore, the annular flow rate was measured by changing the inner diameter of each dip tube in the direction in which the inner diameter of the lower dip tube was made larger than the inner diameter of the riser dip tube. As a result, it was confirmed that the ring flow rate was increased by making the inner diameter of the descending dip tube larger than the inner diameter of the ascending dip tube. However, if the inner diameter of the descending dip tube is made too large, specifically, if the inner diameter exceeds 1.4 times the inner diameter of the ascending reflux tube, the reflux amount is the same on the contrary. It was confirmed that it decreased more than the case. It was also found that the flow rate of the ring increased most in the range where the inner diameter of the descending dip tube was about 1.15 to 1.25 times the inner diameter of the ascending dip tube.

本発明は、これらの知見に基づくものであり、取鍋内の溶鋼を脱ガス槽内に導くための上昇側浸漬管と、脱ガス槽で処理した溶鋼を脱ガス槽から取鍋へ戻すための下降側浸漬管との2本の浸漬管を有する真空脱ガス処理装置において、下降側浸漬管の内径を、上昇側浸漬管の内径の1.4倍を超えない範囲で、上昇側浸漬管の内径よりも大きくすることを特徴としている。   The present invention is based on these findings and is for returning the molten steel treated in the degassing tank from the degassing tank to the ladle from the rising side dip pipe for guiding the molten steel in the ladle into the degassing tank. In the vacuum degassing apparatus having two dip tubes with the lower dip tube, the inner diameter of the lower dip tube is within a range not exceeding 1.4 times the inner diameter of the rise dip tube. It is characterized in that it is larger than the inner diameter.

次に、本発明に係る真空脱ガス処理装置を、RH真空脱ガス装置を例として説明する。図1は、上昇側浸漬管の内径よりも下降側浸漬管の内径の方が大きい、本発明に係るRH真空脱ガス装置の縦断面概略図である。   Next, a vacuum degassing apparatus according to the present invention will be described using an RH vacuum degassing apparatus as an example. FIG. 1 is a schematic vertical cross-sectional view of an RH vacuum degassing apparatus according to the present invention in which the inner diameter of the descending dip tube is larger than the inner diameter of the ascending dip tube.

図1に示すように、RH真空脱ガス装置1は、上部槽6及び下部槽7からなる脱ガス槽5と、下部槽7の下部に設けられた上昇側浸漬管8及び下降側浸漬管9の2つの浸漬管とを備えており、上部槽6には、排気装置(図示せず)と接続するダクト11と、成分調整用合金鉄や脱硫剤などを投入するための原料投入口12と、脱ガス槽5の内部を上下方向に移動可能な上吹きランス13と、が設けられ、また、上昇側浸漬管8には環流用ガス吹き込み管10が設けられている。環流用ガス吹き込み管10からは環流用ガスとしてArガスが上昇側浸漬管8の内部に吹き込まれる構造となっている。図1では、環流用ガス吹き込み管10を1本のみ記載しているが、上昇側浸漬管8にはその円周方向に、1つの供給管から枝分かれした複数個の環流用ガス吹き込み管10が、その吐出方向を上昇側浸漬管8の中心部に向けて設置されている。また、上吹きランス13は、酸素ガスを脱ガス槽5の内部の溶鋼3に向かって吹き付けることができるように構成されている。但し、希ガスのみを吹き込んだり、希ガスと酸素ガスとの混合ガスを吹き込んだりすることもできるのみならず、CaO系媒溶剤などを搬送用ガスとともに溶鋼3に向かって吹き付けることもできるように構成されている。   As shown in FIG. 1, the RH vacuum degassing apparatus 1 includes a degassing tank 5 composed of an upper tank 6 and a lower tank 7, and an ascending side dip pipe 8 and a descending side dip pipe 9 provided at the lower part of the lower tank 7. The upper tub 6 has a duct 11 connected to an exhaust device (not shown), a raw material inlet 12 for introducing a component adjusting alloy iron, a desulfurizing agent, and the like. An upper blowing lance 13 that is movable in the vertical direction inside the degassing tank 5 is provided, and a recirculation gas blowing pipe 10 is provided on the ascending-side dip pipe 8. From the reflux gas blowing tube 10, Ar gas is blown into the rising side immersion tube 8 as the reflux gas. In FIG. 1, only one recirculation gas blowing tube 10 is shown, but the ascending-side dip tube 8 has a plurality of recirculation gas blowing tubes 10 branched from one supply tube in the circumferential direction. The discharge direction is set toward the center of the ascending-side dip tube 8. Further, the upper blowing lance 13 is configured to be able to blow oxygen gas toward the molten steel 3 inside the degassing tank 5. However, not only a rare gas can be blown in, or a mixed gas of a rare gas and an oxygen gas can be blown, but also a CaO-based solvent or the like can be blown toward the molten steel 3 together with a carrier gas. It is configured.

図中、Duは上昇側浸漬管8の内径、Ddは下降側浸漬管9の内径である。この下降側浸漬管9の内径Ddは、上昇側浸漬管8の内径Duの1.4倍を超えない範囲で、上昇側浸漬管8の内径Duよりも大きくなっている。この場合、環流量増加の効果が最も大きくなることから、下降側浸漬管9の内径Ddを、上昇側浸漬管8の内径Duの1.15〜1.25倍の範囲内とすることが好ましい。尚、上昇側浸漬管8の内径Du及び下降側浸漬管9の内径Ddは、両者で径は異なるものの一定であり、下方或いは上方に向かって内径が拡大するなどのことはない。また、上昇側浸漬管8及び下降側浸漬管9は、厚みの略中央部に芯金(図示せず)を有し、その両側にアルミナ質耐火物、マグネシア質耐火物、或いはマグネシア−クロム質耐火物などが施工されて構成されている。   In the figure, Du is the inner diameter of the ascending side dip tube 8 and Dd is the inner diameter of the descending side dip tube 9. The inner diameter Dd of the descending dip tube 9 is larger than the inner diameter Du of the ascending dip tube 8 in a range not exceeding 1.4 times the inner diameter Du of the ascending side dip tube 8. In this case, since the effect of increasing the ring flow rate is maximized, it is preferable that the inner diameter Dd of the descending side dip tube 9 is within a range of 1.15 to 1.25 times the inner diameter Du of the ascending side dip tube 8. . Note that the inner diameter Du of the ascending-side dip tube 8 and the inner diameter Dd of the descending-side dip tube 9 are constant, although the diameters of both are different, and the inner diameter does not increase downward or upward. The ascending-side dip tube 8 and the descending-side dip tube 9 have a metal core (not shown) at a substantially central portion of the thickness, and alumina refractories, magnesia refractories, or magnesia-chromium on both sides thereof. Refractories are constructed and constructed.

このように構成されるRH真空脱ガス装置1において、次のようにして溶鋼3を精錬する。転炉や電気炉などで精錬した溶鋼3を収納する取鍋2を、脱ガス槽5の直下に搬送し、取鍋2を昇降装置(図示せず)によって上昇させ、上昇側浸漬管8及び下降側浸漬管9を取鍋2に収容された溶鋼3に浸漬させる。溶鋼3の上にはスラグ4が存在するので、スラグ4が脱ガス槽5の内部に入らないようにするために、例えば、薄鋼板などを、上昇側浸漬管8及び下降側浸漬管9を浸漬する前にその下方に配置する。浸漬後、環流用ガス吹き込み管10から上昇側浸漬管8の内部にArガスを環流用ガスとして吹き込むとともに、脱ガス槽5の内部をダクト11に連結される排気装置にて排気して脱ガス槽5の内部を減圧する。脱ガス槽5の内部が減圧されると、取鍋2に収容された溶鋼3は、環流用ガス吹き込み管10から吹き込まれるArガスとともにガスリフト効果によって上昇側浸漬管8を上昇して脱ガス槽5の内部に流入し、その後、下降側浸漬管9を介して取鍋2に戻る流れ、所謂、環流を形成してRH真空脱ガス精錬が施される。   In the RH vacuum degassing apparatus 1 configured as described above, the molten steel 3 is refined as follows. The ladle 2 containing the molten steel 3 refined in a converter or electric furnace is transported directly under the degassing tank 5, and the ladle 2 is raised by an elevating device (not shown). The descending side dip tube 9 is immersed in the molten steel 3 accommodated in the pan 2. Since the slag 4 exists on the molten steel 3, in order to prevent the slag 4 from entering the degassing tank 5, for example, a thin steel plate or the like is used for the ascending side dip tube 8 and the descending side dip tube 9. Prior to soaking, place it below. After dipping, Ar gas is blown into the rising side dip pipe 8 from the recirculation gas blowing pipe 10 as recirculation gas, and the inside of the degassing tank 5 is evacuated by an exhaust device connected to the duct 11 for degassing. The inside of the tank 5 is depressurized. When the inside of the degassing tank 5 is depressurized, the molten steel 3 accommodated in the ladle 2 ascends the rising side dip pipe 8 by the gas lift effect together with the Ar gas blown from the reflux gas blowing pipe 10 and degassed tank. 5 flows into the ladle 5 and then returns to the ladle 2 via the descending-side dip pipe 9, so-called recirculation is formed, and RH vacuum degassing is performed.

即ち、溶鋼3は、脱ガス槽5の内部で減圧下に曝され、その結果、溶鋼3に含まれる不純物成分である炭素、窒素、水素は、取鍋内における大気圧下での平衡状態から減圧下での平衡状態へと強制的に移行させられ、溶鋼3に対して、脱炭精錬及びガス成分除去精錬が施される。また、溶鋼3は、前記環流により激しく攪拌され、この攪拌によって脱酸生成物である酸化物系非金属介在物の凝集・合体が促進され、酸化物系非金属介在物の分離除去精錬が行われている。また、更に、原料投入口12などから脱硫剤を添加した場合には、前述した溶鋼3の強攪拌によって溶鋼3と脱硫剤との混合が促進され、溶鋼中の硫黄と脱硫剤とが反応して脱硫精錬が行われる。硫黄を捕り込んだ脱硫剤は下降側浸漬管9から排出された後、スラグ4に吸収される。   That is, the molten steel 3 is exposed to the reduced pressure inside the degassing tank 5, and as a result, the carbon, nitrogen, and hydrogen that are impurity components contained in the molten steel 3 are in an equilibrium state under atmospheric pressure in the ladle. It is forcibly shifted to an equilibrium state under reduced pressure, and the molten steel 3 is subjected to decarburization refining and gas component removal refining. In addition, the molten steel 3 is vigorously stirred by the recirculation, and this stirring promotes agglomeration and coalescence of oxide-based nonmetallic inclusions, which are deoxidation products, and separation and refining of oxide-based nonmetallic inclusions is performed. It has been broken. Further, when a desulfurizing agent is added from the raw material inlet 12 or the like, the mixing of the molten steel 3 and the desulfurizing agent is promoted by the strong stirring of the molten steel 3 described above, and the sulfur in the molten steel reacts with the desulfurizing agent. Desulfurization refining is performed. The desulfurizing agent that traps sulfur is discharged from the descending side dip tube 9 and then absorbed by the slag 4.

これらの精錬は、溶鋼3の環流量が多いほど促進され、短時間で終了する。上記構成のRH真空脱ガス装置1においては、下降側浸漬管9の内径Ddの方が、上昇側浸漬管8の内径Duよりも大きいので、上昇側環流管8及び下降側環流管9の内径が同一である従来の場合に比較して環流量が増加し、短時間で所望する脱ガス精錬を完了することが可能となる。   These refining is promoted as the flow rate of the molten steel 3 increases, and is completed in a short time. In the RH vacuum degassing apparatus 1 configured as described above, the inner diameter Dd of the descending side dip tube 9 is larger than the inner diameter Du of the ascending side dip tube 8, and therefore the inner diameters of the ascending side reflux tube 8 and the descending side reflux tube 9. As compared with the conventional case where the same is the case, the flow rate of the ring is increased, and the desired degassing refining can be completed in a short time.

以下に、RH真空脱ガス装置1において溶鋼3に対して行われる脱ガス精錬について詳しく説明する。尚、水素及び窒素を除去するガス成分除去精錬及び脱酸生成物などの酸化物系非金属介在物の分離除去精錬は、RH真空脱ガス装置1において溶鋼3を取鍋2と脱ガス槽5との間で環流させることにより必然的に施される精錬であるので、それ以外の人為的に行われる脱炭精錬及び脱硫精錬について説明する。ここでは、脱炭精錬及び脱硫精錬の両方を実施する場合について説明する。尚、RH真空脱ガス装置1で行われる減圧下での脱炭精錬を「真空脱炭精錬」と呼び、大気圧下での転炉における脱炭精錬と区別している。   Below, the degassing refining performed with respect to the molten steel 3 in the RH vacuum degassing apparatus 1 is demonstrated in detail. Note that gas component removal refining for removing hydrogen and nitrogen and separation removal refining of oxide-based non-metallic inclusions such as deoxidation products are performed in a RH vacuum degassing apparatus 1 with a ladle 2 and a degassing tank 5. Therefore, the decarburization refining and desulfurization refining performed artificially other than that will be described. Here, the case where both decarburization refining and desulfurization refining are implemented is demonstrated. Note that decarburization refining under reduced pressure performed in the RH vacuum degassing apparatus 1 is called “vacuum decarburization refining”, and is distinguished from decarburization refining in a converter under atmospheric pressure.

真空脱炭精錬は、溶鋼中の溶存酸素濃度が高いほど進行するので、転炉或いは電気炉で溶製した溶鋼を、脱酸処理せずに未脱酸のまま取鍋2に出鋼し、RH真空脱ガス装置1に搬送する。転炉或いは電気炉からの出鋼時、炉内のスラグの一部が溶鋼とともに取鍋2に流出し、取鍋2の溶鋼上にスラグ4として滞留する。このスラグ4は、脱酸処理後の溶鋼中のAlと反応して溶鋼3の清浄性を損なうので、スラグ4に金属Alなどのスラグ改質剤を添加して、スラグ4を改質することが好ましい。   Since the vacuum decarburization refining progresses as the dissolved oxygen concentration in the molten steel increases, the molten steel melted in the converter or electric furnace is put into the ladle 2 without being deoxidized without being deoxidized, It is conveyed to the RH vacuum degassing apparatus 1. At the time of steel output from the converter or electric furnace, a part of the slag in the furnace flows out into the ladle 2 together with the molten steel and stays as slag 4 on the molten steel in the ladle 2. Since this slag 4 reacts with Al in the molten steel after deoxidation treatment and impairs the cleanliness of the molten steel 3, the slag 4 is modified by adding a slag modifier such as metal Al to the slag 4. Is preferred.

未脱酸の溶鋼3を脱ガス槽5の内部の減圧雰囲気に曝すと、脱ガス槽5の内部雰囲気のCOガス分圧は大気圧下で実施した転炉或いは電気炉での脱炭精錬時に比べて大幅に小さいので、溶鋼中の炭素と溶存酸素との反応が発生する。つまり、脱炭反応が発生し、溶鋼3に含まれる炭素はCOガスとなって排ガスとともに脱ガス槽5からダクト11を介して排出され、溶鋼3に真空脱炭精錬が施される。この場合に、溶鋼3の溶存酸素が不足するなどの理由で脱炭反応が遅延する場合には、上吹きランス13から脱ガス槽5の内部の溶鋼3に向かって酸素ガス或いは酸素ガスと希ガスとの混合ガスを吹き付けて、脱炭反応を促進させることもできる。   When the undeoxidized molten steel 3 is exposed to a reduced pressure atmosphere inside the degassing tank 5, the CO gas partial pressure in the inner atmosphere of the degassing tank 5 is reduced during decarburization and refining in a converter or electric furnace performed at atmospheric pressure. Since it is much smaller than that, a reaction between carbon in the molten steel and dissolved oxygen occurs. That is, decarburization reaction occurs, carbon contained in the molten steel 3 becomes CO gas and is discharged together with the exhaust gas from the degas tank 5 through the duct 11, and the molten steel 3 is subjected to vacuum decarburization refining. In this case, when the decarburization reaction is delayed due to a shortage of dissolved oxygen in the molten steel 3, oxygen gas or oxygen gas and a rare gas are supplied from the top blowing lance 13 toward the molten steel 3 inside the degassing tank 5. The decarburization reaction can be promoted by spraying a mixed gas with the gas.

このようにして真空脱炭精錬を継続し、溶鋼3の炭素含有量が所定の値以下となったなら、原料投入口12から溶鋼3に金属Alなどの脱酸剤を添加して溶鋼3を脱酸処理する。この脱酸処理により、溶鋼中の溶存酸素濃度が急激に低下し、真空脱炭精錬が終了する。真空脱炭精錬中、酸素ガスや酸化鉄などを脱ガス槽5に供給していた場合には、前記脱酸剤を添加する前に、酸素ガスや酸化鉄などの供給を停止する。   In this way, when the vacuum decarburization refining is continued and the carbon content of the molten steel 3 becomes a predetermined value or less, a deoxidizer such as metal Al is added to the molten steel 3 from the raw material inlet 12 to obtain the molten steel 3. Deoxidize. By this deoxidation treatment, the dissolved oxygen concentration in the molten steel is rapidly reduced, and the vacuum decarburization refining is completed. If oxygen gas or iron oxide is supplied to the degassing tank 5 during vacuum decarburization refining, the supply of oxygen gas or iron oxide is stopped before the deoxidizer is added.

溶鋼3を脱酸処理した後、原料投入口12から脱硫剤を投入し、脱硫精錬を実施する。この場合、上吹きランス13から、Arガスを搬送用ガスとして、脱硫剤を脱ガス槽5の内部の溶鋼3に向けて吹き付けてもよい。所定量の脱硫剤の添加を完了した以降、更に、数分間の環流を継続し、脱硫剤の浮上・分離を促進させる。更に、その後必要に応じて溶鋼3を還流しながら、Al、Si、Mn、Ni、Cr、Cu、Nb、Ti、V、Bなどの成分調整剤を原料投入口12から溶鋼3に投入して溶鋼3の成分を調整する。成分調整後、脱ガス槽5の内部を大気圧に戻してRH真空脱ガス精錬を終了する。真空脱炭精錬を不要とする場合は、処理開始後直ちに脱硫精錬を実施し、また、脱硫精錬を不要とする場合は、脱酸処理後、直ちに溶鋼3の成分を調整すればよい。   After deoxidizing the molten steel 3, a desulfurizing agent is introduced from the raw material inlet 12, and desulfurization refining is performed. In this case, the desulfurizing agent may be sprayed from the top blowing lance 13 toward the molten steel 3 inside the degassing tank 5 using Ar gas as a carrier gas. After the addition of a predetermined amount of the desulfurizing agent is completed, the refluxing for several minutes is further continued to promote the floating and separation of the desulfurizing agent. Further, while supplying the molten steel 3 as necessary, component modifiers such as Al, Si, Mn, Ni, Cr, Cu, Nb, Ti, V, and B are introduced into the molten steel 3 from the raw material inlet 12. The components of the molten steel 3 are adjusted. After the component adjustment, the inside of the degassing tank 5 is returned to atmospheric pressure, and the RH vacuum degassing refining is completed. When vacuum decarburization refining is not necessary, desulfurization refining is performed immediately after the start of the treatment, and when desulfurization refining is not required, the components of the molten steel 3 may be adjusted immediately after the deoxidation treatment.

以上説明したように、本発明によれば、下降側浸漬管9の内径Ddを上昇側浸漬管8の内径Duに対して所定の範囲内で大きくするので、下降側環流管9における流れに対する抵抗が最小となり、新たな装置を設置しなくとも、溶鋼3の環流量を増大させることができ、その結果、脱ガス精錬反応速度の向上並びに処理時間の短縮が可能となる。   As described above, according to the present invention, the inner diameter Dd of the descending side dip tube 9 is made larger than the inner diameter Du of the ascending side dip tube 8 within a predetermined range. Therefore, the ring flow rate of the molten steel 3 can be increased without installing a new device, and as a result, the degassing refining reaction rate can be improved and the processing time can be shortened.

RH真空脱ガス装置にて、上昇側浸漬管の内径Duと、下降側浸漬管の内径Ddとの関係を種々に変更し、溶鋼にトレーサーとして銅を添加し、均一混合時間を測定した。そして、この均一混合時間から溶鋼の環流量を求めた。   In the RH vacuum degassing apparatus, the relationship between the inner diameter Du of the ascending side dip tube and the inner diameter Dd of the descending side dip tube was variously changed, copper was added as a tracer to the molten steel, and the uniform mixing time was measured. And the ring flow rate of molten steel was calculated | required from this uniform mixing time.

用いた溶鋼の化学成分は、C:0.03〜0.035質量%、Si:0.05質量%以下、Mn:0.3質量%以下、P:0.02質量%以下、S:0.003質量%以下であり、溶鋼温度は1600〜1650℃であった。   The chemical components of the molten steel used were C: 0.03 to 0.035% by mass, Si: 0.05% by mass or less, Mn: 0.3% by mass or less, P: 0.02% by mass or less, S: 0 0.003 mass% or less, and the molten steel temperature was 1600 to 1650 ° C.

図2に、横軸を、上昇側浸漬管の内径Duと下降側浸漬管の内径Ddとの比(Dd/Du)とし、縦軸を環流量比として、得られた試験結果を示す。ここで、縦軸の環流量比とは、上昇側浸漬管の内径Duと、下降側浸漬管の内径Ddとが同じ場合、つまり比(Dd/Du)が1.0の場合の環流量を1.0として表示している。   FIG. 2 shows the test results obtained with the horizontal axis as the ratio (Dd / Du) between the inner diameter Du of the ascending side dip tube and the inner diameter Dd of the descending side dip tube and the vertical axis as the ring flow ratio. Here, the ring flow rate ratio on the vertical axis is the ring flow rate when the inner diameter Du of the ascending-side dip tube and the inner diameter Dd of the descending-side dip tube are the same, that is, when the ratio (Dd / Du) is 1.0. It is displayed as 1.0.

図2に示すように、比(Dd/Du)が1.0よりも大きい場合、つまり、下降側浸漬管の内径Ddが上昇側浸漬管の内径Duよりも大きい場合に、環流量比が増加することが確認できた。しかしながら、比(Dd/Du)が1.4よりも大きくなると、逆に、環流量比は1.0よりも小さくなることが確認できた。   As shown in FIG. 2, when the ratio (Dd / Du) is larger than 1.0, that is, when the inner diameter Dd of the descending dip tube is larger than the inner diameter Du of the ascending dip tube, the ring flow ratio increases. I was able to confirm. However, it was confirmed that when the ratio (Dd / Du) is larger than 1.4, the ring flow rate ratio is smaller than 1.0.

この結果から、比(Dd/Du)を1.0よりも大きく且つ1.4未満とすることで、環流量が増加することが確認できた。   From this result, it was confirmed that the ring flow rate was increased by setting the ratio (Dd / Du) to be greater than 1.0 and less than 1.4.

RH真空脱ガス装置において溶鋼の真空脱炭精錬を実施する際に、上昇側浸漬管の内径Duと、下降側浸漬管の内径Ddとの関係を種々に変更し、試験を実施した。この真空脱炭精錬中、取鍋内の溶鋼から分析試料を採取して、溶鋼中の炭素濃度の経時変化を調査し、炭素濃度が所定値になった時点を処理完了時点として、それまでの所用時間を脱炭処理時間と定義した。   When carrying out vacuum decarburization refining of molten steel in the RH vacuum degassing apparatus, the relationship between the inner diameter Du of the ascending-side dip tube and the inner diameter Dd of the descending-side dip tube was changed in various ways, and tests were performed. During this vacuum decarburization refining, an analytical sample is taken from the molten steel in the ladle, the change in the carbon concentration in the molten steel over time is investigated, and the time when the carbon concentration reaches the predetermined value is defined as the processing completion time. The required time was defined as the decarburization time.

図3に、横軸を、上昇側浸漬管の内径Duと下降側浸漬管の内径Ddとの比(Dd/Du)とし、縦軸を脱炭処理時間比として、得られた試験結果を示す。ここで、縦軸の脱炭処理時間比とは、上昇側浸漬管の内径Duと、下降側浸漬管の内径Ddとが同じ場合、つまり比(Dd/Du)が1.0の場合の脱炭処理時間を1.0として表示している。   FIG. 3 shows the test results obtained with the horizontal axis as the ratio (Dd / Du) of the inner diameter Du of the ascending side dip tube and the inner diameter Dd of the descending side dip tube and the vertical axis as the decarburization treatment time ratio. . Here, the decarburization treatment time ratio on the vertical axis is the decarburization when the inner diameter Du of the ascending-side dip tube and the inner diameter Dd of the descending-side dip tube are the same, that is, when the ratio (Dd / Du) is 1.0. Charcoal processing time is displayed as 1.0.

図3に示すように、比(Dd/Du)が1.0よりも大きい場合、つまり、下降側浸漬管の内径Ddが上昇側浸漬管の内径Duよりも大きい場合に、脱炭処理時間比が減少することが確認できた。しかしながら、比(Dd/Du)が1.4よりも大きくなると、逆に、脱炭処理時間比は1.0よりも大きくなることが確認できた。   As shown in FIG. 3, when the ratio (Dd / Du) is larger than 1.0, that is, when the inner diameter Dd of the descending dip tube is larger than the inner diameter Du of the ascending dip tube, the decarburization processing time ratio Was confirmed to decrease. However, it was confirmed that when the ratio (Dd / Du) is larger than 1.4, the decarburization time ratio is larger than 1.0.

この結果から、比(Dd/Du)を1.0よりも大きく且つ1.4未満とすることで、脱炭処理時間が従来よりも短くなることが確認できた。   From this result, it was confirmed that the decarburization time was shorter than before by setting the ratio (Dd / Du) to be greater than 1.0 and less than 1.4.

RH真空脱ガス装置において溶鋼の脱硫精錬を実施する際に、上昇側浸漬管の内径Duと、下降側浸漬管の内径Ddとの関係を種々に変更し、試験を実施した。この脱硫精錬中、取鍋内の溶鋼から分析試料を採取して、溶鋼中の硫黄濃度の経時変化を調査し、硫黄濃度が所定値になった時点を処理完了時点として、それまでの所用時間を脱硫処理時間と定義した。   When performing desulfurization and refining of molten steel in the RH vacuum degassing apparatus, tests were performed by variously changing the relationship between the inner diameter Du of the ascending side dip tube and the inner diameter Dd of the descending dip tube. During this desulfurization and refining, an analytical sample is taken from the molten steel in the ladle, the change in the sulfur concentration in the molten steel over time is investigated, and the time when the sulfur concentration reaches the specified value is defined as the processing completion time. Was defined as desulfurization time.

図4に、横軸を、上昇側浸漬管の内径Duと下降側浸漬管の内径Ddとの比(Dd/Du)とし、縦軸を脱硫処理時間比として、得られた試験結果を示す。ここで、縦軸の脱硫処理時間比とは、上昇側浸漬管の内径Duと、下降側浸漬管の内径Ddとが同じ場合、つまり比(Dd/Du)が1.0の場合の脱硫処理時間を1.0として表示している。   FIG. 4 shows the test results obtained with the horizontal axis as the ratio (Dd / Du) between the inner diameter Du of the ascending-side dip tube and the inner diameter Dd of the descending-side dip tube, and the ordinate as the desulfurization treatment time ratio. Here, the desulfurization treatment time ratio on the vertical axis is the desulfurization treatment when the inner diameter Du of the ascending-side dip tube is the same as the inner diameter Dd of the descending-side dip tube, that is, when the ratio (Dd / Du) is 1.0. The time is displayed as 1.0.

図4に示すように、比(Dd/Du)が1.0よりも大きい場合、つまり、下降側浸漬管の内径Ddが上昇側浸漬管の内径Duよりも大きい場合に、脱硫処理時間比が減少することが確認できた。しかしながら、比(Dd/Du)が1.4よりも大きくなると、逆に、脱硫処理時間比は1.0よりも大きくなることが確認できた。   As shown in FIG. 4, when the ratio (Dd / Du) is larger than 1.0, that is, when the inner diameter Dd of the descending dip tube is larger than the inner diameter Du of the ascending dip tube, the desulfurization treatment time ratio is It was confirmed that it decreased. However, it was confirmed that when the ratio (Dd / Du) is larger than 1.4, the desulfurization treatment time ratio is larger than 1.0.

この結果から、比(Dd/Du)を1.0よりも大きく且つ1.4未満とすることで、脱硫処理時間が従来よりも短くなることが確認できた。   From this result, it was confirmed that the desulfurization time was shorter than before by setting the ratio (Dd / Du) to be greater than 1.0 and less than 1.4.

本発明に係るRH真空脱ガス装置の縦断面概略図である。It is the longitudinal cross-sectional schematic of the RH vacuum degassing apparatus which concerns on this invention. 比(Dd/Du)と環流量比との関係を示す図である。It is a figure which shows the relationship between ratio (Dd / Du) and a ring flow rate ratio. 比(Dd/Du)と脱炭処理時間比との関係を示す図である。It is a figure which shows the relationship between ratio (Dd / Du) and decarburization processing time ratio. 比(Dd/Du)と脱硫処理時間比との関係を示す図である。It is a figure which shows the relationship between ratio (Dd / Du) and desulfurization process time ratio.

符号の説明Explanation of symbols

1 RH真空脱ガス装置
2 取鍋
3 溶鋼
4 スラグ
5 脱ガス槽
6 上部槽
7 下部槽
8 上昇側浸漬管
9 下降側浸漬管
10 環流用ガス吹き込み管
11 ダクト
12 原料投入口
13 上吹きランス
DESCRIPTION OF SYMBOLS 1 RH vacuum degassing apparatus 2 Ladle 3 Molten steel 4 Slag 5 Degassing tank 6 Upper tank 7 Lower tank 8 Rising side immersion pipe 9 Lowering side immersion pipe 10 Recirculation gas blowing pipe 11 Duct 12 Raw material inlet 13 Upper blowing lance

Claims (2)

脱ガス槽の下部に、取鍋内の溶鋼を脱ガス槽内に導くための上昇側浸漬管と、脱ガス槽で処理した溶鋼を脱ガス槽から取鍋へ戻すための下降側浸漬管との2本の浸漬管を有する真空脱ガス処理装置において、前記上昇側浸漬管の内径(Du)と前記下降側浸漬管の内径(Dd)とが下記の(1)式の関係の範囲内で、下降側浸漬管の内径(Dd)が上昇側浸漬管の内径(Du)よりも大きいことを特徴とする、溶鋼の真空脱ガス処理装置。
1.15Du≦Dd≦1.25×Du(但し、Dd/Du=180/145を除く) …(1)
An ascending side dip pipe for guiding the molten steel in the ladle into the degassing tank, and a descending side dip pipe for returning the molten steel treated in the degassing tank from the degassing tank to the ladle at the bottom of the degassing tank In the vacuum degassing apparatus having two dip tubes, the inner diameter (Du) of the ascending-side dip tube and the inner diameter (Dd) of the descending-side dip tube are within the range of the following formula (1). An apparatus for vacuum degassing of molten steel, characterized in that the inner diameter (Dd) of the descending dip tube is larger than the inner diameter (Du) of the ascending dip tube.
1.15 Du ≦ Dd ≦ 1.25 × Du (excluding Dd / Du = 180/145) (1)
請求項1に記載の溶鋼の真空脱ガス処理装置を用い、前記上昇側浸漬管によって取鍋内の溶鋼を脱ガス槽に導入すると同時に、前記下降側浸漬管によって脱ガス槽内の溶鋼を取鍋内に排出させ、かくして取鍋内の溶鋼を取鍋と脱ガス槽との間で環流させながら精錬することを特徴とする、溶鋼の真空脱ガス精錬方法。   Using the vacuum degassing apparatus for molten steel according to claim 1, the molten steel in the ladle is introduced into the degassing tank by the rising side dip pipe, and at the same time, the molten steel in the degassing tank is removed by the descending side dip pipe. A method for vacuum degassing and refining molten steel, characterized in that the molten steel is discharged into the pan and thus refined while circulating the molten steel in the ladle between the ladle and the degassing tank.
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