JP2017075399A - Top-blown lance, vacuum degasser and vacuum degassing treatment method - Google Patents

Top-blown lance, vacuum degasser and vacuum degassing treatment method Download PDF

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JP2017075399A
JP2017075399A JP2016201082A JP2016201082A JP2017075399A JP 2017075399 A JP2017075399 A JP 2017075399A JP 2016201082 A JP2016201082 A JP 2016201082A JP 2016201082 A JP2016201082 A JP 2016201082A JP 2017075399 A JP2017075399 A JP 2017075399A
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vacuum
molten steel
vacuum degassing
blowing lance
oxygen gas
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JP6372540B2 (en
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新司 小関
Shinji Koseki
新司 小関
新吾 佐藤
Shingo Sato
新吾 佐藤
安藤　誠
Makoto Ando
誠 安藤
直哉 澁田
Naoya Shibuta
直哉 澁田
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JFE Steel Corp
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Abstract

PROBLEM TO BE SOLVED: To provide a top-blown lance, a vacuum degasser and a vacuum degassing treatment method in which, in the vacuum degassing treatment accompanying decarburization reaction by blowing oxygen gas, the amount of splash generation can be reduced under a high degree of vacuum.SOLUTION: Provided is a top-blown lance 9 used in a vacuum degasser 1 and for injecting oxygen gas into a molten steel 3 in a vacuum tank 4 of the vacuum degasser 1, and including one single Laval type nozzle 92 having a throat diameter d1 of 30 mm or more and 70 mm or less as well as an outlet diameter d2 of 80 mm or more and 140 mm or less at the tip.SELECTED DRAWING: Figure 2

Description

本開示は、上吹きランス、真空脱ガス装置および真空脱ガス処理方法に関する。   The present disclosure relates to an upper blowing lance, a vacuum degassing apparatus, and a vacuum degassing processing method.

製鉄の製鋼プロセスでは、転炉等で一次精錬処理された溶鋼の成分を調整するために、ＲＨ法や、ＤＨ−ＡＤ法、ＬＶＤ法等の各種真空脱ガス方式を用いた二次精錬処理が行われる。このうち、ＲＨ法では、真空槽内で高真空に曝した溶鋼に対してＡｒガスを吹き込み、溶鋼を還流・攪拌することで、主に溶鋼中のガス成分が除去される（真空脱ガス処理）。さらに、ＲＨ法では、真空脱ガス処理中の溶鋼に対して、上吹きランスから酸素ガスを吹き付けることにより、溶鋼中の炭素が除去（脱炭）されるため、高品質な鋼を製造することができる。   In the steelmaking process, secondary refining processes using various vacuum degassing methods such as the RH method, DH-AD method, and LVD method are used to adjust the components of the molten steel that has been subjected to the primary refining process in a converter or the like. Done. Among them, in the RH method, Ar gas is blown into the molten steel exposed to high vacuum in a vacuum chamber, and the molten steel is refluxed and stirred to mainly remove gas components in the molten steel (vacuum degassing treatment). ). Furthermore, in the RH method, carbon in the molten steel is removed (decarburized) by blowing oxygen gas from the top blowing lance against the molten steel being vacuum degassed, so that high quality steel is manufactured. Can do.

このＲＨ法では、近年、二次精錬プロセスの効率化や処理速度の向上を目的とした様々な取り組みが行われている。例えば、特許文献１には、真空脱ガス処理中の溶鋼に対して、上吹きランスから酸素と燃料ガスとを噴出させ、燃焼させることにより、溶鋼の温度上昇を図る方法が記載されている。また、特許文献２には、真空脱ガス処理中の溶鋼に対して、複数のランスから酸素を吹き付けることにより、脱炭反応を促進させる方法が開示されている。   In recent years, various efforts have been made in the RH method for the purpose of improving the efficiency of the secondary refining process and improving the processing speed. For example, Patent Document 1 describes a method of increasing the temperature of molten steel by injecting oxygen and fuel gas from an upper blowing lance to the molten steel being vacuum degassed and burning it. Patent Document 2 discloses a method of promoting a decarburization reaction by blowing oxygen from a plurality of lances to molten steel being vacuum degassed.

特許第２７５９０２１号公報Japanese Patent No. 2759021 特開２００２−２９４３２９号公報JP 2002-294329 A

ところで、ＲＨ法では、溶鋼から水素や窒素等のガス成分を除去する際、真空槽中の真空度を高めることにより、脱ガス反応が促進されることが知られている。しかし、例えば５０Ｔｏｒｒ以下の高い真空度下において、特許文献１，２に記載の方法のように上吹きランス等から酸素を溶鋼に吹き付けて脱炭処理を行う場合、吹き付ける酸素の体積が増大することで吹き付け流速が増大し、浴面動圧が高まることにより、スプラッシュの発生量が増大することが問題であった。スプラッシュは、溶鋼が表面のガス流動によって飛散する現象であり、これが生じると装置壁面や上吹きランスへの地金付着により操業が困難となる。
そこで、本発明は、上記の課題に着目してなされたものであり、酸素ガス吹き付けによる脱炭反応を伴う真空脱ガス処理において、高い真空度下でスプラッシュの発生量を低減することができる上吹きランス、真空脱ガス装置および真空脱ガス処理方法を提供することを目的としている。 By the way, in the RH method, it is known that the degassing reaction is promoted by increasing the degree of vacuum in the vacuum chamber when removing gas components such as hydrogen and nitrogen from the molten steel. However, when the decarburization process is performed by blowing oxygen onto the molten steel from the top blowing lance or the like under the high vacuum degree of 50 Torr or less, for example, the volume of the blowing oxygen increases. As a result, the spray flow rate increases and the bath surface dynamic pressure increases, which increases the amount of splash generated. Splash is a phenomenon in which molten steel scatters due to gas flow on the surface, and when this occurs, operation becomes difficult due to adhesion of metal to the wall surface of the apparatus and the upper blowing lance.
Therefore, the present invention has been made paying attention to the above-described problem, and in the vacuum degassing process involving the decarburization reaction by blowing oxygen gas, the amount of splash generated can be reduced under a high degree of vacuum. It aims at providing a blow lance, a vacuum degassing apparatus, and a vacuum degassing processing method.

本発明は、上記課題の解決のためになされたものであって、以下の特徴を有している。
[１]真空脱ガス装置で用いられ、前記真空脱ガス装置の真空槽内の溶鋼に酸素ガスを噴射する上吹きランスであって、スロート径が３０ｍｍ以上７０ｍｍ以下、且つ出口径が８０ｍｍ以上１４０ｍｍ以下の１つのラバール型のノズルを先端に備えることを特徴とする上吹きランス。
[２]前記ノズルのスロート長さは、７０ｍｍ以上であることを特徴とする[１]に記載の上吹きランス。 The present invention has been made to solve the above problems, and has the following features.
[1] An upper blowing lance that is used in a vacuum degassing apparatus and injects oxygen gas into molten steel in the vacuum tank of the vacuum degassing apparatus, and has a throat diameter of 30 mm to 70 mm and an outlet diameter of 80 mm to 140 mm An upper blowing lance comprising the following one Laval nozzle at the tip.
[2] The top blowing lance according to [1], wherein the nozzle has a throat length of 70 mm or more.

[３]５０Ｔｏｒｒ以下の真空度で溶鋼を真空脱ガス処理する真空槽と、前記真空槽内の溶鋼に酸素ガスを噴射する上吹きランスとを備え、前記上吹きランスは、スロート径が３０ｍｍ以上１４０ｍｍ以下、且つ出口径が８０ｍｍ以上１４０ｍｍ以下の１つのラバール型のノズルを先端に備えることを特徴とする真空脱ガス装置。
[４]真空脱ガス装置の真空槽内で真空脱ガス処理される溶鋼に、上吹きランスから酸素ガスを噴射することで前記溶鋼を脱炭する際に、５０Ｔｏｒｒ以下の真空度で前記溶鋼を真空脱ガス処理し、スロート径が３０ｍｍ以上１４０ｍｍ以下、且つ出口径が８０ｍｍ以上１４０ｍｍ以下の１つのラバール型のノズルを先端に備える前記上吹きランスを用いることを特徴とする真空脱ガス処理方法。 [3] A vacuum tank for vacuum degassing the molten steel at a vacuum degree of 50 Torr or less, and an upper blowing lance for injecting oxygen gas to the molten steel in the vacuum tank, the upper blowing lance having a throat diameter of 30 mm or more A vacuum degassing apparatus comprising a single Laval type nozzle having an outlet diameter of not more than 140 mm and an outlet diameter of not less than 80 mm and not more than 140 mm at the tip.
[4] When the molten steel is decarburized by injecting oxygen gas from an upper blowing lance to the molten steel to be vacuum degassed in a vacuum tank of a vacuum degassing apparatus, the molten steel is removed at a vacuum degree of 50 Torr or less. A vacuum degassing method using the upper blowing lance which is vacuum degassed and has one Laval nozzle having a throat diameter of 30 mm to 140 mm and an outlet diameter of 80 mm to 140 mm at the tip.

本発明の一態様によれば、酸素ガス吹き付けによる脱炭反応を伴う真空脱ガス処理において、高い真空度であってもスプラッシュの発生量を低減することができる。   According to one embodiment of the present invention, in a vacuum degassing process involving a decarburization reaction by blowing oxygen gas, the amount of splash generated can be reduced even at a high degree of vacuum.

本発明の一実施形態に係る真空脱ガス装置を示す断面図である。It is sectional drawing which shows the vacuum degassing apparatus which concerns on one Embodiment of this invention. 上吹きランスの先端を示す一部断面図である。It is a partial cross section figure which shows the front-end | tip of an upper blowing lance.

以下の詳細な説明では、本発明の実施形態の完全な理解を提供するように多くの特定の細部について記載される。しかしながら、かかる特定の細部がなくても１つ以上の実施態様が実施できることは明らかであろう。他にも、図面を簡潔にするために、周知の構造及び装置が略図で示されている。
＜真空脱ガス装置の構成＞
はじめに、図１および図２を参照して、本発明の一実施形態に係る真空脱ガス装置１について説明する。真空脱ガス装置１は、ＲＨ方式の脱ガス装置であり、取鍋２に収容された溶鋼３に対して脱ガスや脱炭等の精錬処理を行う。溶鋼３は、予め転炉等の精錬装置において、一次精錬処理される。 In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of embodiments of the present invention. However, it will be apparent that one or more embodiments may be practiced without such specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawing.
<Configuration of vacuum degasser>
First, with reference to FIG. 1 and FIG. 2, the vacuum degassing apparatus 1 which concerns on one Embodiment of this invention is demonstrated. The vacuum degassing apparatus 1 is an RH type degassing apparatus, and performs a refining process such as degassing and decarburizing on the molten steel 3 accommodated in the ladle 2. The molten steel 3 is subjected to a primary refining process in advance in a refining apparatus such as a converter.

真空脱ガス装置１は、真空槽４と、上昇側浸漬管５と、下降側浸漬管６と、ダクト７と、副原料投入管８と、上吹きランス９とを有する。
真空槽４は、内面に耐火物が設けられた略円筒容器状の容器であり、上昇側浸漬管５および下降側浸漬管６、ならびに上部にダクト７および副原料投入管８がそれぞれ接続される。 The vacuum degassing apparatus 1 includes a vacuum chamber 4, an ascending side dip tube 5, a descending side dip tube 6, a duct 7, an auxiliary material charging tube 8, and an upper blowing lance 9.
The vacuum chamber 4 is a substantially cylindrical container with a refractory provided on the inner surface, and the ascending-side dip tube 5 and the descending-side dip tube 6 are connected to the duct 7 and the auxiliary material charging tube 8 at the upper part, respectively. .

上昇側浸漬管５および下降側浸漬管６は、略円筒状の形状を有し、内面および下端側の外面に耐火物が設けられる。また、上昇側浸漬管５は、不図示のガス供給装置から供給されるガスを内面から吹き込むように構成される。
ダクト７は、不図示の真空排気装置と接続され、真空排気装置によって真空槽４の内部の気圧を低くすることができるように構成される。
副原料投入管８は、不図示の複数のホッパーに接続され、各ホッパーから合金鉄等の各種副原料が送られることで、真空槽４内の溶鋼３に副原料を投入する。 The ascending-side dip tube 5 and the descending-side dip tube 6 have a substantially cylindrical shape, and a refractory is provided on the inner surface and the outer surface on the lower end side. The ascending-side dip tube 5 is configured to blow gas supplied from a gas supply device (not shown) from the inner surface.
The duct 7 is connected to an unillustrated evacuation device, and is configured so that the atmospheric pressure inside the vacuum chamber 4 can be lowered by the evacuation device.
The auxiliary raw material charging pipe 8 is connected to a plurality of hoppers (not shown), and various auxiliary raw materials such as alloy iron are sent from the hoppers to input the auxiliary raw materials to the molten steel 3 in the vacuum chamber 4.

上吹きランス９は、図２に示すように、長手方向（図１，２の紙面に対する上下方向）に酸素供給路９１が内部に形成され、下端にノズル９２が設けられる。ノズル９２は、ラバール型の形状を有し、酸素供給路９１側のスロート部におけるスロート径ｄ１が３０ｍｍ以上７０ｍｍ以下、且つ下端側の出口径ｄ２が８０ｍｍ以上１４０ｍｍ以下である。スロート径ｄ１が３０ｍｍ未満または出口径ｄ２が８０ｍｍ未満となる場合、酸素ガスの動圧が過度に高くなり、スプラッシュの発生量が増大してしまう。一方、スロート径ｄ１が８０ｍｍ超または出口径ｄ２が１４０ｍｍ超となる場合、酸素ガスの動圧が過度に低くなり、脱炭速度が低下してしまう。なお、スロート径ｄ１と出口径ｄ２とは、噴出流速と動圧とが最大となる適正開口比である必要は無い。これは最適開口比から意図的に外した設計とすることで酸素ガスの噴流が広がり、火点面積の増大が見込めるためである。また、ノズル９２のスロート部から出口までの酸素ガス噴射方向の長さであるスロート長さＬは、７０ｍｍ以上であることが好ましい。スロート長さＬを７０ｍｍ以上とすることで、安定した噴流挙動を得ることができるため、酸素ガスの最適な動圧をより確実に確保することができる。さらに、上吹きランス９の真空槽４の外に配された上端側は、不図示の酸素供給装置に接続される。このような構成の上吹きランスは、酸素供給装置を介して送られる酸素ガスを、ノズル９２から真空槽４内の溶鋼３に噴射する。   As shown in FIG. 2, the upper blowing lance 9 has an oxygen supply passage 91 formed therein in the longitudinal direction (vertical direction with respect to the plane of FIGS. 1 and 2), and a nozzle 92 provided at the lower end. The nozzle 92 has a Laval shape, and the throat diameter d1 at the throat portion on the oxygen supply passage 91 side is 30 mm or more and 70 mm or less, and the outlet diameter d2 on the lower end side is 80 mm or more and 140 mm or less. When the throat diameter d1 is less than 30 mm or the outlet diameter d2 is less than 80 mm, the dynamic pressure of the oxygen gas becomes excessively high and the amount of splash generated increases. On the other hand, when the throat diameter d1 exceeds 80 mm or the outlet diameter d2 exceeds 140 mm, the dynamic pressure of oxygen gas becomes excessively low, and the decarburization speed decreases. It should be noted that the throat diameter d1 and the outlet diameter d2 do not need to be an appropriate opening ratio that maximizes the ejection flow velocity and the dynamic pressure. This is because the oxygen gas jet is expanded by intentionally removing the design from the optimum aperture ratio, and an increase in the hot spot area can be expected. The throat length L, which is the length in the oxygen gas injection direction from the throat portion of the nozzle 92 to the outlet, is preferably 70 mm or more. By setting the throat length L to 70 mm or more, a stable jet behavior can be obtained, so that the optimum dynamic pressure of oxygen gas can be ensured more reliably. Further, the upper end side of the upper blowing lance 9 disposed outside the vacuum chamber 4 is connected to an oxygen supply device (not shown). The upper blowing lance having such a configuration injects oxygen gas sent through the oxygen supply device from the nozzle 92 to the molten steel 3 in the vacuum chamber 4.

＜真空脱ガス処理方法＞
次に、本実施形態に係る真空脱ガス処理方法について説明する。まず、真空槽４を下降させ、取鍋２内に収容された溶鋼３に上昇側浸漬管５および下降側浸漬管６を浸漬させる。なお、溶鋼３は、炭素濃度が１．０ｍａｓｓ％以下のものであればよい。溶鋼３の炭素濃度が１．０ｍａｓｓ％超となると脱炭時間が非常に長くなるため、真空脱ガス処理前に炭素濃度を１．０ｍａｓｓ％以下まで低減しておくことが望ましい。 <Vacuum degassing method>
Next, the vacuum degassing method according to this embodiment will be described. First, the vacuum chamber 4 is lowered, and the ascending side dip tube 5 and the descending side dip tube 6 are immersed in the molten steel 3 accommodated in the ladle 2. In addition, the molten steel 3 should just be a carbon concentration of 1.0 mass% or less. When the carbon concentration of the molten steel 3 exceeds 1.0 mass%, the decarburization time becomes very long. Therefore, it is desirable to reduce the carbon concentration to 1.0 mass% or less before the vacuum degassing treatment.

次いで、真空槽４内の真空度を５０Ｔｏｒｒ以下とし、真空槽４内の所定の高さまで溶鋼３を吸い上げる。さらに、上昇側浸漬管５の内面からＡｒガスを吹き込むことにより、溶鋼３を還流させる。これにより、溶鋼３中の水素や窒素といったガス成分が除去される。なお、真空度を、真空脱ガス処理の全ての期間にわたって、１０Ｔｏｒｒ以上５０Ｔｏｒｒ以下とすることが好ましい。通常の真空脱ガス装置では、６０Ｔｏｒｒ程度の真空度で脱炭を伴う真空脱ガス処理が行われることが多いが、本実施形態では、真空度を５０Ｔｏｒｒ以下とすることで通常よりも高い脱ガス速度で処理を行うことができる。一方、真空度が１０Ｔｏｒｒ以下になると、ガスの体積膨張が激しくなり、溶鋼３の浴面における酸素ガスの動圧が低くなる可能性があるため、真空度を１０Ｔｏｒｒ以上とすることが好ましい。なお、ここで言う真空度は、絶対圧基準での真空度とする。   Next, the degree of vacuum in the vacuum chamber 4 is set to 50 Torr or less, and the molten steel 3 is sucked up to a predetermined height in the vacuum chamber 4. Further, the molten steel 3 is refluxed by blowing Ar gas from the inner surface of the ascending-side dip tube 5. Thereby, gas components, such as hydrogen and nitrogen, in the molten steel 3 are removed. Note that the degree of vacuum is preferably 10 Torr or more and 50 Torr or less over the entire period of the vacuum degassing process. In a normal vacuum degassing apparatus, vacuum degassing with decarburization is often performed at a vacuum degree of about 60 Torr, but in this embodiment, degassing higher than usual is achieved by setting the vacuum degree to 50 Torr or less. Processing can be done at speed. On the other hand, when the degree of vacuum is 10 Torr or less, the volume expansion of the gas becomes violent and the dynamic pressure of oxygen gas on the bath surface of the molten steel 3 may be lowered. Therefore, the degree of vacuum is preferably 10 Torr or more. The degree of vacuum referred to here is the degree of vacuum based on absolute pressure.

そして、溶鋼３を還流させた状態で、上吹きランス９から酸素ガスを溶鋼３に吹き込み、溶鋼３中の炭素を酸化除去する。この際、上吹きランス９の下端から溶鋼３の浴面までの高さ（ランス高さ）を３５００ｍｍ以上５５００ｍｍ以下、酸素ガスの送酸量を２０００Ｎｍ３／ｈ以上３０００Ｎｍ３／ｈ以下とすることで、一般的なＲＨ方式の真空脱ガス装置１において適用することができる。また、炭素の酸化除去によって生じるＣＯ気泡によってもガス成分が除去される。酸素ガスの吹込みは、所定量の酸素ガスが吹き込まれるまで行われる。酸素ガスの吹込み量は、真空脱ガス処理する前の溶鋼３の炭素濃度および処理後の目標炭素濃度、ならびに処理後の目標温度等によって決定される。 And in the state which made the molten steel 3 recirculate | reflux, oxygen gas was blown into the molten steel 3 from the top blowing lance 9, and the carbon in the molten steel 3 was oxidized and removed. At this time, the height (lance height) from the lower end of the top blowing lance 9 to the bath surface of the molten steel 3 is 3500 mm or more and 5500 mm or less, and the amount of oxygen gas sent is 2000 Nm 3 / h or more and 3000 Nm 3 / h or less. Thus, the present invention can be applied to a general RH type vacuum degassing apparatus 1. Further, gas components are also removed by CO bubbles generated by oxidative removal of carbon. The oxygen gas is blown until a predetermined amount of oxygen gas is blown. The amount of oxygen gas blown is determined by the carbon concentration of the molten steel 3 before vacuum degassing treatment, the target carbon concentration after treatment, the target temperature after treatment, and the like.

なお、ＲＨ方式の真空脱ガス装置１において、ランス高さを３５００ｍｍ以上とすることで、上吹きランス９への地金の付着を抑えることができ、さらに酸素ガスの噴流が十分に広がった状態で溶鋼３へ到達するため、火点面積が確保され安定した脱炭速度を得ることができる。一方、ランス高さを５５００ｍｍ以下とすることで、酸素ガスが確実に溶鋼３へ到達するため、脱炭速度を十分に速くすることができる。また、脱炭反応で生じるＣＯガスによって酸素ガスの溶鋼３への到達が妨げられる可能性があるが、ランス高さを５５００ｍｍ以下とすることで、ＣＯガスの発生量に関わらず酸素ガスを確実に溶鋼３へ到達させることができる。さらに、送酸量を２０００Ｎｍ３／ｈ以上とすることで、十分な脱炭速度を得ることができる。一方、送酸量を３０００Ｎｍ３／ｈ以下とすることで、１０Ｔｏｒｒ程度の高い真空度においても、スプラッシュの発生を防止することができる。
その後、溶鋼３が所定の成分および温度となるまで溶鋼３の還流が行われることで、真空脱ガス処理が終了する。なお、真空脱ガス処理中は、必要に応じて合金鉄や脱酸剤（金属アルミ等）といった副原料が、副原料投入管８から投入される。 In the RH-type vacuum degassing apparatus 1, by setting the lance height to 3500 mm or more, it is possible to suppress the adhesion of the metal to the top blowing lance 9, and further, the oxygen gas jet is sufficiently expanded Therefore, the hot spot area is secured and a stable decarburization rate can be obtained. On the other hand, when the lance height is 5500 mm or less, the oxygen gas reliably reaches the molten steel 3, so that the decarburization speed can be sufficiently increased. In addition, the CO gas generated by the decarburization reaction may prevent the oxygen gas from reaching the molten steel 3, but by setting the lance height to 5500 mm or less, the oxygen gas can be reliably obtained regardless of the amount of CO gas generated. Can reach the molten steel 3. Furthermore, a sufficient decarburization rate can be obtained by setting the amount of acid sent to 2000 Nm 3 / h or more. On the other hand, when the amount of acid sent is 3000 Nm 3 / h or less, the occurrence of splash can be prevented even at a high degree of vacuum of about 10 Torr.
Thereafter, the molten steel 3 is refluxed until the molten steel 3 reaches a predetermined component and temperature, thereby completing the vacuum degassing process. During the vacuum degassing process, auxiliary materials such as iron alloy and deoxidizer (metal aluminum, etc.) are input from the auxiliary material input pipe 8 as necessary.

以上で、特定の実施形態を参照して本発明を説明したが、これら説明によって発明を限定することを意図するものではない。本発明の説明を参照することにより、当業者には、開示された実施形態の種々の変形例とともに本発明の別の実施形態も明らかである。従って、特許請求の範囲は、本発明の範囲及び要旨に含まれるこれらの変形例または実施形態も網羅すると解すべきである。   Although the present invention has been described above with reference to specific embodiments, it is not intended that the present invention be limited by these descriptions. From the description of the invention, other embodiments of the invention will be apparent to persons skilled in the art, along with various variations of the disclosed embodiments. Therefore, it is to be understood that the claims encompass these modifications and embodiments that fall within the scope and spirit of the present invention.

＜実施形態の効果＞
（１）本発明の一態様に係る上吹きランス９は、真空脱ガス装置１で用いられ、真空脱ガス装置１の真空槽４内の溶鋼３に酸素ガスを噴射する上吹きランス９であって、スロート径ｄ１が３０ｍｍ以上７０ｍｍ以下、且つ出口径ｄ２が８０ｍｍ以上１４０ｍｍ以下の１つのラバール型のノズル９２を先端に備える。
上記構成によれば、ノズル９２のスロート径ｄ１および出口径ｄ２を上記範囲内とすることにより、溶鋼３への酸素ガスの動圧をコントロールすることができる。このため、上記構成の上吹きランス９を用いて、酸素ガス吹き付けによる脱炭反応を伴う真空脱ガス処理を行う際に、５０Ｔｏｒｒ以下の高い真空度下においてスプラッシュの発生量を操業上の問題がない程度に低減することができる。 <Effect of embodiment>
(1) The top blowing lance 9 according to one aspect of the present invention is a top blowing lance 9 that is used in the vacuum degassing apparatus 1 and injects oxygen gas into the molten steel 3 in the vacuum tank 4 of the vacuum degassing apparatus 1. In addition, one tip of a Laval type nozzle 92 having a throat diameter d1 of 30 mm to 70 mm and an outlet diameter d2 of 80 mm to 140 mm is provided at the tip.
According to the said structure, the dynamic pressure of the oxygen gas to the molten steel 3 can be controlled by making the throat diameter d1 and the exit diameter d2 of the nozzle 92 into the said range. For this reason, when performing the vacuum degassing process accompanied by the decarburization reaction by oxygen gas blowing using the top blowing lance 9 having the above-described configuration, there is an operational problem with the amount of splash generated under a high degree of vacuum of 50 Torr or less. It can be reduced to the extent that it is not.

ここで、通常の真空脱ガス装置にて溶鋼３を真空脱ガス処理する場合、脱ガス反応を促進させるために真空度を高くする必要がある。しかし、真空度が高い程ガスの体積が増加してスプラッシュが発生し易くなるため、高い真空度での真空脱ガス処理中に脱炭を行う場合、吹き込む酸素ガスや発生するＣＯガスによるスプラッシュの発生が問題となる。このため、例えば５０Ｔｏｒｒ以下の真空度で脱炭反応を伴う真空脱ガス処理をするには、上吹きランスから噴射される酸素ガスの送酸速度を低くする必要があった。送酸速度を低くすることでガス成分の体積が小さくなり、スプラッシュの発生を抑えることができる。一方で脱炭速度が低くなるため、真空脱ガス処理に掛かる時間が長くなることが問題であった。しかし、上記構成によれば、送酸速度を低くすることなく、高い真空度での真空脱ガス処理を安定して行うことができるようになるため、脱ガス効率および脱炭速度を共に向上させることができる。これにより、高い真空脱ガス処理に掛かる時間を短くすることができ、生産性を向上させることができる。   Here, when the molten steel 3 is vacuum degassed with a normal vacuum degassing apparatus, it is necessary to increase the degree of vacuum in order to promote the degassing reaction. However, as the degree of vacuum increases, the volume of gas increases, and splash is likely to occur. Therefore, when decarburization is performed during vacuum degassing at a high degree of vacuum, splashing due to oxygen gas to be blown in or generated CO gas is likely to occur. Occurrence becomes a problem. For this reason, for example, in order to perform vacuum degassing with decarburization at a degree of vacuum of 50 Torr or less, it is necessary to reduce the oxygen feed rate of oxygen gas injected from the top blowing lance. By reducing the acid feed rate, the volume of the gas component is reduced, and the occurrence of splash can be suppressed. On the other hand, since the decarburization speed becomes low, the problem is that the time required for the vacuum degassing process becomes long. However, according to the above configuration, it is possible to stably perform the vacuum degassing process at a high degree of vacuum without lowering the acid feed rate, thereby improving both the degassing efficiency and the decarburizing speed. be able to. Thereby, the time required for high vacuum degassing treatment can be shortened, and productivity can be improved.

さらに、脱炭反応を伴う真空脱ガス処理では、溶鋼３の炭素濃度が高くなるに従い、処理中に発生するＣＯガスの発生量が増加する。また高真空下では、発生したＣＯガスが膨張し、それによって溶鋼３が泡立って跳ね上がるため、スプラッシュの発生量が増大する。このため、高い炭素濃度（特に、０．３ｍａｓｓ％以上の炭素濃度）の溶鋼３を脱炭する際にはスプラッシュの発生が問題となる。しかし、上記構成によれば、真空脱ガス装置１で高い炭素濃度の溶鋼３を脱炭する場合でも、スプラッシュの発生を低減することができ、安定して処理を行うことができる。
（２）上記（１）の構成において、ノズル９２のスロート長さＬは、７０ｍｍ以上である。
上記構成によれば、（１）のみの構成に比べ、安定した噴流挙動を得ることができるため、酸素ガスの最適な動圧をより確実に実現することができる。 Furthermore, in the vacuum degassing process accompanied by the decarburization reaction, the amount of CO gas generated during the process increases as the carbon concentration of the molten steel 3 increases. Further, under high vacuum, the generated CO gas expands, and as a result, the molten steel 3 bubbles and jumps up, so that the amount of splash generated increases. For this reason, when decarburizing the molten steel 3 having a high carbon concentration (particularly, a carbon concentration of 0.3 mass% or more), the occurrence of splash becomes a problem. However, according to the said structure, generation | occurrence | production of a splash can be reduced even when decarburizing the molten steel 3 with a high carbon concentration with the vacuum degassing apparatus 1, and it can process stably.
(2) In the configuration of (1) above, the throat length L of the nozzle 92 is 70 mm or more.
According to the above configuration, stable jet behavior can be obtained as compared with the configuration of only (1), and thus the optimum dynamic pressure of oxygen gas can be realized more reliably.

（３）本発明の一態様に係る真空脱ガス装置１は、５０Ｔｏｒｒ以下の真空度で溶鋼３を真空脱ガス処理する真空槽４と、真空槽４内の溶鋼３に酸素ガスを噴射する上吹きランス９とを備え、上吹きランス９は、スロート径ｄ１が３０ｍｍ以上１４０ｍｍ以下、且つ出口径ｄ２が８０ｍｍ以上１４０ｍｍ以下の１つのラバール型のノズル９２を先端に備える。   (3) The vacuum degassing apparatus 1 according to one aspect of the present invention includes a vacuum tank 4 for vacuum degassing the molten steel 3 at a degree of vacuum of 50 Torr or less, and an oxygen gas injection to the molten steel 3 in the vacuum tank 4 The top lance 9 includes a single Laval nozzle 92 having a throat diameter d1 of 30 mm to 140 mm and an outlet diameter d2 of 80 mm to 140 mm at the tip.

（４）本発明の一態様に係る真空脱ガス処理方法は、真空脱ガス装置１の真空槽４内で真空脱ガス処理される溶鋼３に、上吹きランス９から酸素ガスを噴射することで溶鋼３を脱炭する際に、５０Ｔｏｒｒ以下の真空度で溶鋼３を真空脱ガス処理し、スロート径ｄ１が３０ｍｍ以上１４０ｍｍ以下、且つ出口径ｄ２が８０ｍｍ以上１４０ｍｍ以下の１つのラバール型のノズル９２を先端に備える上吹きランス９を用いる。   (4) In the vacuum degassing method according to one aspect of the present invention, oxygen gas is injected from the top blowing lance 9 into the molten steel 3 to be vacuum degassed in the vacuum tank 4 of the vacuum degassing apparatus 1. When the molten steel 3 is decarburized, the molten steel 3 is vacuum degassed at a vacuum degree of 50 Torr or less, and one Laval type nozzle 92 having a throat diameter d1 of 30 mm to 140 mm and an outlet diameter d2 of 80 mm to 140 mm. An upper blowing lance 9 having a tip is used.

上記（３），（４）の構成によれば、（１）と同様な効果を得ることができる。また、５０Ｔｏｒｒ以下の真空度でも、脱炭反応を伴う真空脱ガス処理を行うことができるようになるため、脱ガス効率を向上させることができる。さらに、例えば特許文献２の方法のように、動圧を低減させるために複数のランスや付帯設備を設ける必要がなく、上吹きランス自体を変更するだけで一般的な真空脱ガス装置に本発明を適用することができる。このため、設備の導入や維持に掛かるコストを低減させることができる。   According to the configurations of (3) and (4) above, the same effect as in (1) can be obtained. Moreover, since the vacuum degassing process accompanied with the decarburization reaction can be performed even at a vacuum degree of 50 Torr or less, the degassing efficiency can be improved. Further, as in the method of Patent Document 2, for example, it is not necessary to provide a plurality of lances and incidental equipment to reduce dynamic pressure, and the present invention is applied to a general vacuum degassing apparatus by simply changing the top blowing lance itself. Can be applied. For this reason, the cost concerning introduction and maintenance of equipment can be reduced.

次に、本発明者らが行った実施例について説明する。実施例では、上記実施形態と同様にＲＨ方式の真空脱ガス装置１を用いて、炭素濃度が０．３ｍａｓｓ％程度の溶鋼３について、脱炭反応を含む真空脱ガス処理をした。この際、上吹きランス９のスロート径ｄ１や出口径ｄ２、真空度、ランス高さ、送酸量といった条件を変え、これらの条件がスプラッシュの発生量や精錬効率に与える影響について確認をした。また、スロート長さＬは、全ての条件において７０ｍｍとした。なお、実施例では、実操業下で上吹きランス９の交換を頻繁に行うことが困難であったことから、一部の条件については実機の真空脱ガス装置１を用いて処理を行い、その他の条件については実機で得られた結果と数値解析とから評価を行った。数値解析による評価では、上昇側浸漬管５および下降側浸漬管６よりも下側の領域については解析モデルに含めずに、真空槽４内の領域についての解析モデルを用いて数値解析を行い、さらに溶鋼３の浴面よりも上側の領域について各種評価を行った。   Next, examples performed by the present inventors will be described. In the examples, the vacuum degassing process including the decarburization reaction was performed on the molten steel 3 having a carbon concentration of about 0.3 mass% using the RH vacuum degassing apparatus 1 as in the above embodiment. At this time, conditions such as the throat diameter d1 and outlet diameter d2 of the top blowing lance 9, the degree of vacuum, the lance height, and the amount of acid delivered were changed, and the influence of these conditions on the amount of splash generated and the refining efficiency was confirmed. The throat length L was 70 mm under all conditions. In the embodiment, since it was difficult to frequently replace the top blowing lance 9 under actual operation, some conditions were processed using the actual vacuum degassing apparatus 1 and others. These conditions were evaluated from the results obtained with the actual machine and numerical analysis. In the evaluation by numerical analysis, the area below the ascending-side dip pipe 5 and the descending-side dip pipe 6 is not included in the analysis model, and numerical analysis is performed using the analysis model for the area in the vacuum chamber 4; Furthermore, various evaluation was performed about the area | region above the bath surface of the molten steel 3. FIG.

表１に、実施例における真空度、スロート径ｄ１、出口径ｄ２、ランス高さおよび送酸量の条件と、評価の結果とを示す。なお、実施例では、上記実施形態に係る上吹きランスを用いた真空脱ガス処理の条件として、ノズル９２の形状や真空度、ランス高さ、送酸量の条件を変えた実施例１〜２３の２３条件で真空脱ガス処理を行った。また、スロート径ｄ１および出口径ｄ２の条件が上記実施形態と異なる比較例として、比較例１〜１１の１１条件で真空脱ガス処理を行った。   Table 1 shows the conditions of the degree of vacuum, the throat diameter d1, the outlet diameter d2, the lance height and the amount of acid delivered in the examples, and the evaluation results. In Examples, Examples 1 to 23 in which the shape of the nozzle 92, the degree of vacuum, the lance height, and the amount of acid supplied were changed as the conditions for the vacuum degassing process using the top blowing lance according to the above embodiment. The vacuum degassing treatment was performed under the following 23 conditions. Further, as a comparative example in which the conditions of the throat diameter d1 and the outlet diameter d2 are different from those of the above embodiment, vacuum degassing treatment was performed under 11 conditions of Comparative Examples 1-11.

表１に示すように、実施例では、スプラッシュの発生量の評価として、真空脱ガス処理後の上吹きランス９への地金の付着量を用いた。つまり、上吹きランス９に付着した地金の量からスプラッシュの発生量を判断した。そして、通常行われている条件となる比較例１に対して地金の付着量が同等または少なければ「○」とし、比較例１に対して地金の付着量が多ければ「×」とした。なお、数値解析による評価の場合、気液二相の解析モデルを用いて解析を行うことでスプラッシュの発生量を推定し、比較例１の条件におけるスプラッシュの発生量と比較することで評価を行った。   As shown in Table 1, in the examples, as the evaluation of the generation amount of splash, the adhesion amount of the base metal to the upper blowing lance 9 after the vacuum degassing process was used. That is, the amount of splash generated was determined from the amount of metal attached to the top blowing lance 9. And it is set as "(circle)" when the adhesion amount of a bullion is equal or small with respect to the comparative example 1 used as the conditions normally performed, and it is set as "*" when there is a large amount of bullion adhesion compared with the comparative example 1. . In the case of evaluation by numerical analysis, the amount of splash generation is estimated by performing analysis using a gas-liquid two-phase analysis model, and evaluation is performed by comparing with the amount of splash generation under the conditions of Comparative Example 1. It was.

また、脱炭速度の評価では、真空脱ガス処理中に発生する排ガス量および排ガス中のＣＯガス濃度から脱炭速度を測定した。なお、数値解析による評価の場合、実際に真空脱ガス処理を行った条件での脱炭速度と、各条件における計算上の動圧との関係を調べ、得られたこの関係と、数値解析による評価を行う条件での計算上の動圧とから脱炭速度を推定した。例えば、計算上の動圧が同程度である場合、脱炭速度も同程度であるとみなした。   In the evaluation of the decarburization rate, the decarburization rate was measured from the amount of exhaust gas generated during the vacuum degassing process and the CO gas concentration in the exhaust gas. In the case of evaluation by numerical analysis, the relationship between the decarburization speed under the actual vacuum degassing conditions and the calculated dynamic pressure under each condition was investigated, and this relationship obtained and numerical analysis The decarburization rate was estimated from the calculated dynamic pressure under the evaluation conditions. For example, when the calculated dynamic pressure was the same, the decarburization rate was considered to be the same.

さらに、脱ガス速度の評価では、真空脱ガス処理中の溶鋼３中の窒素濃度および水素濃度をそれぞれ測定し、脱ガス速度として脱窒素速度および脱水速度を算出した。そして、比較例１に対して、脱ガス速度が向上していれば「○」または「◎」とし、特に顕著に向上した場合を「◎」とした。そして、最終的な評価として、スプラッシュの評価が「○」、且つ脱炭速度が比較例１の脱炭速度以上、且つ脱ガス速度の評価が「○」または「◎」であった条件を「○」として、これらの評価のうち少なくとも１つが条件を外れたものについては「×」とした。   Further, in the evaluation of the degassing rate, the nitrogen concentration and the hydrogen concentration in the molten steel 3 during the vacuum degassing treatment were measured, respectively, and the denitrogenation rate and the dehydration rate were calculated as the degassing rate. And compared with the comparative example 1, it was set as "(circle)" or "(double-circle)" when the degassing speed was improving, and the case where it improved notably was set as "(double-circle)". Then, as a final evaluation, the condition that the evaluation of the splash was “◯”, the decarburization rate was equal to or higher than the decarburization rate of Comparative Example 1, and the evaluation of the degassing rate was “O” or “◎” was “ As “◯”, those in which at least one of these evaluations was out of the condition were marked “x”.

Figure 2017075399
Figure 2017075399

実施例の結果、比較例２〜１１および実施例１〜２３の条件では、５０Ｔｏｒｒ以下と高い真空度にすることで、比較例１よりも脱ガス速度が速くなることを確認した。特に、真空度を３０Ｔｏｒｒ以下とすることで、より高い脱ガス速度が得られた。
また、上記実施形態の条件と異なり、スロート径ｄ１を２０ｍｍおよび出口径ｄ２を６０ｍｍ以下とした比較例２〜４の場合、スプラッシュの発生量が多くなった。さらに、スロート径ｄ１を２０ｍｍもしくは８０ｍｍとした比較例５〜８，１０，１１、または出口径ｄ２を６０ｍｍとした比較例９の場合、脱炭速度が０．００４ｍａｓｓ％／ｍｉｎとなり、比較例１に比べ低下した。つまり、比較例２〜１１では、スロート径ｄ１および出口径ｄ２の少なくともいずれかの条件が、上記実施形態の範囲を超えることで、スプラッシュの発生量および脱炭速度の少なくともいずれかの評価が悪くなることを確認した。 As a result of Examples, it was confirmed that the degassing rate was higher than that of Comparative Example 1 by setting the degree of vacuum to 50 Torr or less under the conditions of Comparative Examples 2 to 11 and Examples 1 to 23. In particular, when the degree of vacuum was 30 Torr or less, a higher degassing rate was obtained.
Further, unlike the conditions of the above embodiment, in the case of Comparative Examples 2 to 4 in which the throat diameter d1 was 20 mm and the outlet diameter d2 was 60 mm or less, the amount of splash was increased. Further, in Comparative Examples 5 to 8, 10, and 11 in which the throat diameter d1 is 20 mm or 80 mm, or in Comparative Example 9 in which the outlet diameter d2 is 60 mm, the decarburization speed is 0.004 mass% / min. Compared to That is, in Comparative Examples 2 to 11, when at least one of the conditions of the throat diameter d1 and the outlet diameter d2 exceeds the range of the above embodiment, the evaluation of at least one of the amount of splash generation and the decarburization speed is poor. It was confirmed that

一方、実施例１〜２３の条件では、スロート径ｄ１、出口径ｄ２、真空度、ランス高さおよび送酸量に関わらず、すべての条件において、スプラッシュの発生量および脱炭速度の評価がよくなることを確認した。つまり、上記実施形態の構成とすることにより、５０Ｔｏｒｒ以下の真空度であっても、操業上問題になるようなスプラッシュの発生が防止され、さらに、脱炭速度および脱ガス速度が速くなることを確認できた。   On the other hand, in the conditions of Examples 1 to 23, regardless of the throat diameter d1, the outlet diameter d2, the degree of vacuum, the lance height, and the amount of acid fed, the evaluation of the amount of splash and the decarburization rate are improved in all conditions. It was confirmed. In other words, by adopting the configuration of the above-described embodiment, it is possible to prevent the occurrence of splash that causes an operational problem even at a vacuum level of 50 Torr or less, and to further increase the decarburization rate and the degassing rate. It could be confirmed.

１ 真空脱ガス装置
２ 取鍋
３ 溶鋼
４ 真空槽
５ 上昇側浸漬管
６ 下降側浸漬管
７ ダクト
８ 副原料投入管
９ 上吹きランス
９１ 酸素供給路
９２ ノズル
ｄ１ スロート径
ｄ２ 出口径
Ｌ スロート長さ DESCRIPTION OF SYMBOLS 1 Vacuum degassing apparatus 2 Ladle 3 Molten steel 4 Vacuum tank 5 Ascending side immersion pipe 6 Decreasing side immersion pipe 7 Duct 8 Sub raw material input pipe 9 Top blowing lance 91 Oxygen supply path 92 Nozzle d1 Throat diameter d2 Outlet diameter L Throat length

Claims (4)

真空脱ガス装置で用いられ、前記真空脱ガス装置の真空槽内の溶鋼に酸素ガスを噴射する上吹きランスであって、
スロート径が３０ｍｍ以上７０ｍｍ以下、且つ出口径が８０ｍｍ以上１４０ｍｍ以下の１つのラバール型のノズルを先端に備えることを特徴とする上吹きランス。 An upper blowing lance used in a vacuum degassing device, for injecting oxygen gas into molten steel in a vacuum tank of the vacuum degassing device,
An upper blowing lance comprising a single Laval nozzle having a throat diameter of 30 mm to 70 mm and an outlet diameter of 80 mm to 140 mm at the tip. 前記ノズルのスロート長さは、７０ｍｍ以上であることを特徴とする請求項１に記載の上吹きランス。   The top blowing lance according to claim 1, wherein a throat length of the nozzle is 70 mm or more. ５０Ｔｏｒｒ以下の真空度で溶鋼を真空脱ガス処理する真空槽と、
前記真空槽内の溶鋼に酸素ガスを噴射する上吹きランスと
を備え、
前記上吹きランスは、スロート径が３０ｍｍ以上１４０ｍｍ以下、且つ出口径が８０ｍｍ以上１４０ｍｍ以下の１つのラバール型のノズルを先端に備えることを特徴とする真空脱ガス装置。 A vacuum chamber for vacuum degassing of molten steel at a vacuum degree of 50 Torr or less;
An upper blowing lance for injecting oxygen gas to the molten steel in the vacuum chamber,
A vacuum degassing apparatus characterized in that the upper blowing lance is provided with one Laval type nozzle having a throat diameter of 30 mm to 140 mm and an outlet diameter of 80 mm to 140 mm at the tip. 真空脱ガス装置の真空槽内で真空脱ガス処理される溶鋼に、上吹きランスから酸素ガスを噴射することで前記溶鋼を脱炭する際に、
５０Ｔｏｒｒ以下の真空度で前記溶鋼を真空脱ガス処理し、
スロート径が３０ｍｍ以上１４０ｍｍ以下、且つ出口径が８０ｍｍ以上１４０ｍｍ以下の１つのラバール型のノズルを先端に備える前記上吹きランスを用いることを特徴とする真空脱ガス処理方法。 When decarburizing the molten steel by injecting oxygen gas from the top blowing lance to the molten steel to be vacuum degassed in the vacuum tank of the vacuum degassing device,
Vacuum degassing the molten steel at a vacuum degree of 50 Torr or less,
A vacuum degassing method characterized by using the upper blowing lance provided with one Laval nozzle having a throat diameter of 30 mm to 140 mm and an outlet diameter of 80 mm to 140 mm at the tip.
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JP2020111775A (en) * 2019-01-10 2020-07-27 日本製鉄株式会社 Refining method of molten steel

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