JPH0299263A - Method for cleaning molten metal under reduced pressure - Google Patents
Method for cleaning molten metal under reduced pressureInfo
- Publication number
- JPH0299263A JPH0299263A JP63250806A JP25080688A JPH0299263A JP H0299263 A JPH0299263 A JP H0299263A JP 63250806 A JP63250806 A JP 63250806A JP 25080688 A JP25080688 A JP 25080688A JP H0299263 A JPH0299263 A JP H0299263A
- Authority
- JP
- Japan
- Prior art keywords
- molten metal
- gas
- inclusions
- pressure
- bubbling
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 239000002184 metal Substances 0.000 title claims abstract description 53
- 238000000034 method Methods 0.000 title claims description 32
- 238000004140 cleaning Methods 0.000 title claims description 4
- 239000007789 gas Substances 0.000 claims abstract description 35
- 230000005587 bubbling Effects 0.000 claims abstract description 21
- 238000007872 degassing Methods 0.000 claims abstract description 10
- 238000010407 vacuum cleaning Methods 0.000 claims description 4
- 239000011261 inert gas Substances 0.000 claims description 3
- 238000003756 stirring Methods 0.000 claims description 3
- 229910000831 Steel Inorganic materials 0.000 description 8
- 239000010959 steel Substances 0.000 description 8
- 238000007664 blowing Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 2
- 239000012467 final product Substances 0.000 description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 230000002787 reinforcement Effects 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 239000002436 steel type Substances 0.000 description 1
- 230000002747 voluntary effect Effects 0.000 description 1
Landscapes
- Casting Support Devices, Ladles, And Melt Control Thereby (AREA)
- Treatment Of Steel In Its Molten State (AREA)
- Continuous Casting (AREA)
Abstract
Description
〔産業上の利用分野〕
この発明は、溶融金属中に浮遊する介在物を除去する溶
融金属の減圧清浄化方法に関する。
〔従来の技術〕
溶融金属中に浮遊する介在物(例えば溶鋼中のアルミナ
系介在物)は、製品品質欠陥の原因となるため、その低
減・除去方法が種々提案されている。
その中で比較的効率が良いとして多用されている方法に
、常圧下で容器の底から溶融金属中に不活性ガスをバブ
リングすることで、ガス気泡に介在物をトラップさせ、
浮上後これを除去する方法がある。
ところが、高級材製造を目的とした場合、溶鋼中のトー
タル酸素量は15ppm以下に抑える必要があるが、上
記の方法によってはこのような溶融金属の超清浄化を達
成し得ないという問題があり、新たな手段の開発が望ま
れていた。
即ち、従来のガスバブリング法では、バブリング領域が
容器、底面のガス吹込み口から上方に摺り綿状に広がる
領域だけであり、しかも吹込み方法の制約から容器全域
からバブリングすることは難しいという問題があった。
又、バブリングによりできる気泡の大きさが大きいとい
うことが原因となり、該気泡が浮上する際、溶融金属は
その周りを迂回するように流れ、その流れと一緒に微細
介在物もこの気泡を避けて移動するため、微細介在物は
気泡にトラップされにくいといった問題もある。
そのため本発明者等は、次のような提案を行なった。そ
の提案内容は、加圧状態にした溶融金属を、それに可溶
なガスでバブリングして該溶融金属中にガスを溶解せし
め、その後急速に減圧して溶融金属中に微細ガス気泡を
発生させ、溶融金属中に浮遊する介在物をバブリングに
よるガス気泡及び減圧により発生した微細ガス気泡にト
ラップせしめて、浮上後これを除去するというものであ
る。
溶融金属中の通常の介在物は最初のバブリングでトラッ
プされ浮上せしめられることになる。
他方、このバブリングは加圧した溶融金属に対して行な
われるため、バブリングガスが多量に溶融金属中に溶け
込むことになる。その後の急速な減圧で、溶融金属中に
溶け込んでいたガスが微細なガス気泡となって溶融金属
全域から発生する。この時、微細な介在物は該ガス気泡
にトラップされて浮上する。
〔発明が解決しようとする問題点〕
このように溶融金属中の介在物を除去するには、極めて
効率の良い優れた方法ではあるが、処理工程の最初の段
階で溶融金属を加圧状態にしているため、減圧後の放置
時間が短い場合、−旦溶融金属中に溶け込んだバブリン
グガスは、減圧時にその一部が微細ガス気泡となって現
われるものの、残りは溶融金属中に依然溶け残ったまま
の状態となる。従って上記処理後に更に脱ガスを行なう
別処理工程が必要となり、該脱ガスのために設備増強や
処理工数の増加が問題となっていた。又、加圧容器を使
用するため設備コスト等も高くつくといった別の問題も
ある。
本発明は、以上のような問題に鑑み創案されたもので、
圧力調整を伴う上記のバブリング方法を改良し、加圧容
器を使用せず、しかも上記したような脱ガス工程を省く
ことができるようにしようとするものである。
〔問題点を解決するための手段〕
そのため本発明は、既提案の溶融金属の清浄化方法のう
ち最初に行なっていた溶融金属の加圧処理を止め、該溶
融金属に対して大気圧もしくはそれ以下の状態で、それ
に可溶なガスをバブリングし、その後に減圧処理を行な
う。特にこの減圧処理では、単に微細ガス気泡を発生さ
せるだけでなく、溶融金属中に溶け残っている前記バブ
リングガスも一緒に脱ガスすることになる。
但し、溶融金属浴の浴深が深い程、溶融金属に静圧がか
かるため、減圧時に浴深部における脱ガスを行なうこと
が難しくなる(特に該浴深が1.5m以上となるとその
傾向は強いようである)。このような場合は、溶融金属
に不活性ガスをバブリングして該溶融金属を撹拌せしめ
ることで、減圧による脱ガスを効率良く行なわしめるよ
うにすると良い。
添付図面は、本発明法を実施した場合にバブリングを行
なう最初の処理の際の容器内圧力(P 5tart )
と、減圧処理を行なう後の処理工程における容器内圧力
(P end )を座標に採って、処理後に得られる溶
融金属中の介在物T・(0)と最終[N]の量を調べて
示したものである。
図中、交差する線Aで示した領域は、上記介在物が減少
し、且つ最終(N)が最終製品に与える影響が少なく問
題とならない本発明法による領域を示している。又、斜
線Bで示した領域は。
該介在物は減少するが、最終(N)が問題となる領域で
あり、鋼種によっては、この処理後新たに脱Nを行なう
工程が必要となる。尚、以下に示す実施例で行なった本
発明法は同グラフ図中・(黒点)で示した所で行なわれ
たことになる。
〔実施例〕
以下本発明法の具体的実施例につき説明する。
最初に本発明者等は、50ton V OD設備内で5
0ton溶鋼を1660℃で300torrに保ち、取
鍋底部よりポーラスプラグで10分間6Nm’のN2ガ
スを吹き込んだ。その後VAD設備内に該溶鋼を移し熱
補償を行ないながら急速に1torrまで減圧させ20
分間保持した。この時、同時に取鍋底部からArガスを
15ONn/minでバブリングした。
又、従来のArガスバブリング法と、N2ガスバブリン
グ時に加圧状態にして行なう既提案に係る加圧減圧法を
上記実験と共に実施した。そのうち従来法は50ton
の溶鋼を真空取鍋内で0.5〜1torrに維持したま
ま取鍋底部よりArガスを15ON4/+++inの吹
込み速度で20分間バブリングしたものである。又、加
圧減圧法はN2ガス吹込み時に3気圧まで加圧し、その
後の減圧処理時には0.5torrまで減圧することに
より行なわれるもので、その他は本発明法と同様な条件
で処理された。
但し減圧時にはArガス吹込みによる撹拌は行なってお
らず、又、減圧処理後における脱ガス処理も行なってい
ない。
以上の3法を実施した時の溶鋼成分とT・[Industrial Application Field] The present invention relates to a method for vacuum cleaning molten metal for removing inclusions floating in molten metal. [Prior Art] Inclusions floating in molten metal (for example, alumina inclusions in molten steel) cause product quality defects, and various methods have been proposed to reduce and remove them. Among these methods, one method that is widely used as it is relatively efficient is to bubble inert gas into the molten metal from the bottom of the container under normal pressure to trap inclusions in the gas bubbles.
There is a way to remove this after surfacing. However, if the purpose is to manufacture high-grade materials, the total amount of oxygen in molten steel must be kept to 15 ppm or less, but there is a problem that such ultra-cleaning of molten metal cannot be achieved depending on the method described above. , it was hoped that a new method would be developed. That is, in the conventional gas bubbling method, the bubbling area is limited to the area that spreads upward from the gas inlet at the bottom of the container, and it is difficult to bubble from the entire area of the container due to restrictions on the bubbling method. was there. Another cause is that the bubbles created by bubbling are large, and when the bubbles float up, the molten metal flows around them, and along with the flow, fine inclusions also avoid the bubbles. There is also the problem that fine inclusions are difficult to be trapped by air bubbles because they move. Therefore, the present inventors made the following proposal. The proposal involves bubbling pressurized molten metal with a soluble gas to dissolve the gas in the molten metal, and then rapidly reducing the pressure to generate fine gas bubbles in the molten metal. Inclusions floating in molten metal are trapped in gas bubbles caused by bubbling and fine gas bubbles generated by reduced pressure, and are removed after floating. Normal inclusions in the molten metal will be trapped and brought to the surface by the initial bubbling. On the other hand, since this bubbling is performed on pressurized molten metal, a large amount of bubbling gas dissolves into the molten metal. Due to the subsequent rapid depressurization, the gas dissolved in the molten metal becomes fine gas bubbles and is generated from the entire area of the molten metal. At this time, fine inclusions are trapped by the gas bubbles and float up. [Problems to be solved by the invention] Although this is an excellent and extremely efficient method for removing inclusions from molten metal, it is difficult to pressurize the molten metal at the first stage of the treatment process. Therefore, if the standing time after depressurization is short, some of the bubbling gas that has dissolved into the molten metal will appear as fine gas bubbles when the pressure is decompressed, but the rest will remain dissolved in the molten metal. It will remain as it is. Therefore, after the above-mentioned treatment, a separate treatment step for further degassing is required, which poses a problem of equipment reinforcement and an increase in the number of processing steps for the degassing. In addition, there is another problem that equipment costs are high because a pressurized container is used. The present invention was created in view of the above problems, and
The present invention aims to improve the above-mentioned bubbling method involving pressure adjustment so that a pressurized container is not used and the degassing step as described above can be omitted. [Means for Solving the Problems] Therefore, the present invention stops the pressure treatment of the molten metal that was initially performed in the previously proposed molten metal cleaning methods, and applies atmospheric pressure or a lower pressure to the molten metal. In the following conditions, a soluble gas is bubbled therein, and then a reduced pressure treatment is performed. In particular, this depressurization process not only generates fine gas bubbles, but also degasses the bubbling gas remaining dissolved in the molten metal. However, the deeper the bath depth of the molten metal bath, the more static pressure is applied to the molten metal, making it difficult to degas the deep part of the bath during depressurization (this tendency is especially strong when the bath depth is 1.5 m or more). ). In such a case, it is preferable to bubble an inert gas into the molten metal and stir the molten metal to efficiently degas the metal under reduced pressure. The attached drawing shows the pressure inside the container (P 5tart ) during the first bubbling process when the method of the present invention is implemented.
By taking the pressure inside the container (P end ) in the treatment step after performing the depressurization treatment as coordinates, the amount of inclusions T・(0) and the final [N] in the molten metal obtained after the treatment is investigated and shown. It is something that In the figure, the area indicated by the intersecting line A indicates the area where the inclusions are reduced and the final product (N) has little influence on the final product and does not pose a problem using the method of the present invention. Also, the area indicated by diagonal line B is. Although the inclusions are reduced, the final (N) is a problem area, and depending on the steel type, a new de-N process is required after this treatment. It should be noted that the method of the present invention carried out in the examples shown below was carried out at the points indicated by (black dots) in the same graph. [Example] Specific examples of the method of the present invention will be described below. First, the inventors developed a 50 ton VOD equipment
0 ton of molten steel was maintained at 1660° C. and 300 torr, and 6 Nm' of N2 gas was blown into it from the bottom of the ladle using a porous plug for 10 minutes. After that, the molten steel was transferred into the VAD equipment and the pressure was rapidly reduced to 1 torr while performing heat compensation.
Hold for minutes. At this time, Ar gas was simultaneously bubbled from the bottom of the ladle at 15 ONn/min. In addition, the conventional Ar gas bubbling method and the previously proposed pressurization and depressurization method, in which the N2 gas is brought into a pressurized state during bubbling, were carried out together with the above experiments. Of these, the conventional method is 50 tons
While maintaining the molten steel at 0.5 to 1 torr in a vacuum ladle, Ar gas was bubbled through the bottom of the ladle at a blowing rate of 15 ON4/++in for 20 minutes. The pressurization and depressurization method was carried out by increasing the pressure to 3 atm when blowing N2 gas, and reducing the pressure to 0.5 torr during the subsequent depressurization treatment, and other conditions were the same as in the method of the present invention. However, when the pressure was reduced, stirring by blowing Ar gas was not performed, and no degassing treatment was performed after the pressure reduction treatment. Molten steel composition and T・
〔0〕及びT
・(N)の成分変化を下表に示す。
上記表からも明らかなように、本発明法は加圧減圧法と
略同程度に溶鋼中の介在物の除去がなされており、しか
もその後に脱ガス処理を行なわなくても溶鋼中のN2ガ
スは十分に低減せしめられていることがわかる。
〔発明の効果〕
以上詳述したように本発明の減圧清浄化方法によれば、
溶融金属中の介在物が十分に除去されることになると共
に、加圧処理を行なっていないため加圧容器を必要とせ
ず、且つ減圧時に脱ガスも十分になされるため、その後
脱ガスを別処理工程として行なう必要がなくなって、該
処理設備の増設を不要とすることができ、又、その分処
理工数も減らすことが可能となる等、優れた効果を有し
ている。[0] and T
・The table below shows the changes in the components of (N). As is clear from the table above, the method of the present invention removes inclusions from molten steel to the same extent as the pressurization and depressurization method, and moreover, the N2 gas in the molten steel is removed even without subsequent degassing treatment. It can be seen that this has been sufficiently reduced. [Effects of the Invention] As detailed above, according to the vacuum cleaning method of the present invention,
Inclusions in the molten metal are sufficiently removed, and since no pressure treatment is performed, no pressurized container is required, and sufficient degassing occurs during depressurization, so subsequent degassing is not necessary. It is no longer necessary to carry out this process as a treatment step, making it unnecessary to install additional processing equipment, and it has excellent effects such as being able to reduce the number of processing steps accordingly.
図面は本発明法を実施した場合に最初に行なわれた処理
の際の容器内圧力と、その後の減圧処理時の容器内圧力
を座標に採り、処理後に得られる溶融金属中の介在物と
最終(N)の量を調ベて示したグラフ図である。
P end
(torr)
手続補正書
(自発)
平成元年12月28日The drawing shows the coordinates of the pressure inside the container during the first treatment performed when the method of the present invention is carried out, and the pressure inside the container during the subsequent depressurization treatment, and shows the inclusions in the molten metal obtained after the treatment and the final It is a graph diagram showing the amount of (N) investigated. P end (torr) Procedural amendment (voluntary) December 28, 1989
Claims (1)
可溶なガスでバブリングして該溶融金属中にガスを溶解
せしめ、その後急速に減圧して溶融金属中に微細ガス気
泡を発生させると共に、この減圧で該溶融金属中に溶け
残っているバブリングガスの脱ガスを合わせて行ない、
溶融金属中に浮遊する介在物をバブリングによるガス気
泡及び減圧により発生した微細ガス気泡にトラップせし
めて、浮上後これを除去することを特徴とする溶融金属
の減圧清浄化方法。 2、前項記載の溶融金属の減圧清浄化方法を実施するに
当り、溶融金属中に不活性ガスをバブリングせしめて該
溶融金属を撹拌しながら急速に減圧せしめることを特徴
とする溶融金属の減圧清浄化方法。[Claims] 1. The gas is dissolved in the molten metal by bubbling the molten metal with a gas soluble in the molten metal at atmospheric pressure or lower, and then the pressure is rapidly reduced to form a fine gas in the molten metal. Generating bubbles and degassing the bubbling gas remaining dissolved in the molten metal using this reduced pressure,
A method for cleaning molten metal under reduced pressure, which comprises trapping inclusions floating in molten metal in gas bubbles caused by bubbling and fine gas bubbles generated by reduced pressure, and removing the inclusions after floating. 2. In carrying out the vacuum cleaning method for molten metal described in the preceding paragraph, vacuum cleaning of molten metal is characterized by bubbling an inert gas into the molten metal and rapidly reducing the pressure while stirring the molten metal. method.
Priority Applications (9)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP25080688A JP2718096B2 (en) | 1988-10-06 | 1988-10-06 | Vacuum cleaning method for molten metal |
CA000614559A CA1339703C (en) | 1988-10-06 | 1989-09-29 | Method for cleaning molten metal |
AU42457/89A AU4245789A (en) | 1988-10-06 | 1989-10-02 | Method for cleaning molten metal |
DE8989118517T DE68905741T2 (en) | 1988-10-06 | 1989-10-05 | METHOD FOR CLEANING METAL. |
EP89118517A EP0362851B1 (en) | 1988-10-06 | 1989-10-05 | Method for cleaning molten metal |
BR898905068A BR8905068A (en) | 1988-10-06 | 1989-10-05 | METAL FUSION CLEANING PROCESS |
KR1019890014420A KR920006578B1 (en) | 1988-10-06 | 1989-10-06 | Method for cleaning molten metal and apparatus therefor |
US07/516,478 US5091000A (en) | 1987-12-25 | 1990-04-30 | Method for cleaning molten metal and apparatus therefor |
AU13976/92A AU655245B2 (en) | 1988-10-06 | 1992-04-02 | Method for cleaning molten metal |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP25080688A JP2718096B2 (en) | 1988-10-06 | 1988-10-06 | Vacuum cleaning method for molten metal |
Publications (2)
Publication Number | Publication Date |
---|---|
JPH0299263A true JPH0299263A (en) | 1990-04-11 |
JP2718096B2 JP2718096B2 (en) | 1998-02-25 |
Family
ID=17213325
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP25080688A Expired - Lifetime JP2718096B2 (en) | 1987-12-25 | 1988-10-06 | Vacuum cleaning method for molten metal |
Country Status (1)
Country | Link |
---|---|
JP (1) | JP2718096B2 (en) |
-
1988
- 1988-10-06 JP JP25080688A patent/JP2718096B2/en not_active Expired - Lifetime
Also Published As
Publication number | Publication date |
---|---|
JP2718096B2 (en) | 1998-02-25 |
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