JPH02290929A - Vacuum refining method for molten metal - Google Patents
Vacuum refining method for molten metalInfo
- Publication number
- JPH02290929A JPH02290929A JP10717889A JP10717889A JPH02290929A JP H02290929 A JPH02290929 A JP H02290929A JP 10717889 A JP10717889 A JP 10717889A JP 10717889 A JP10717889 A JP 10717889A JP H02290929 A JPH02290929 A JP H02290929A
- Authority
- JP
- Japan
- Prior art keywords
- molten metal
- gas
- pressure
- bubbles
- inclusions
- 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.)
- Pending
Links
- 239000002184 metal Substances 0.000 title claims abstract description 42
- 238000007670 refining Methods 0.000 title claims abstract description 17
- 238000000034 method Methods 0.000 title claims description 17
- 238000006243 chemical reaction Methods 0.000 claims description 6
- 239000012535 impurity Substances 0.000 claims description 6
- 239000002893 slag Substances 0.000 claims description 6
- 230000001276 controlling effect Effects 0.000 abstract 1
- 238000004090 dissolution Methods 0.000 abstract 1
- 230000001105 regulatory effect Effects 0.000 abstract 1
- 229910000831 Steel Inorganic materials 0.000 description 5
- 238000007872 degassing Methods 0.000 description 5
- 239000010959 steel Substances 0.000 description 5
- 230000006837 decompression Effects 0.000 description 2
- 230000001133 acceleration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 238000006477 desulfuration reaction Methods 0.000 description 1
- 230000023556 desulfurization Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000011946 reduction process Methods 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
Landscapes
- Manufacture And Refinement Of Metals (AREA)
- Treatment Of Steel In Its Molten State (AREA)
Abstract
Description
〔産業上の利用分野〕
この発明は溶融金属中の不純物・介在物を除去する真空
精錬法に関する。
〔従来の技術〕
本発明者等は溶融金属中の介在物除去効率を高めるため
，次のような提案を行なった。即ち，溶融金属に、これ
に可溶なガスをパブリングして溶解せしめると共に、減
圧によって該溶融金属中に微細ガス気泡を発生させると
いうものである。この方法によれば溶融金属中の介在物
は微細なものまでこの気泡にトラップされて浮上するこ
とになり、介在物除去能力が非常に高いものとなる。
一方本発明者等は、上記の介在物除去における気泡浮上
の状態にヒントを得て、これを脱ガス精錬法またはスラ
グ精錬法に応用する開発を行なった．即ち、上記の手順
に従って溶融金属中に微細ガス気泡を発生せしめ、その
浮上により該溶融金属と雰囲気との界面あるいは溶融金
属と溶融スラグの界面をばたつかせてその反応界面積を
増大せしめるというものである。このガス気泡は溶融金
属全域から発生するため，上記界面のばたつきは該界面
全面に及ぶ。しかも、そのガス気泡は微細なものが多量
に発生するため、上記反応界面積の増大は顕著なものと
なり、脱ガス精錬やスラブ精錬による不純物除去能力は
非常に高いものとなる．〔発明が解決しようとする問題
点〕
いずれの精錬法も溶融金属中の介在物・不純物を除去し
、超清浄溶湯を得るには非常に効率の良い方法であるが
，減圧処理時間が依然２０分程度必要であり、これを更
に短縮せしめて効率化を図りたいという要請があった。
本発明は以上の問題に鑑み創案されたものであり、上述
した真空精錬法における減圧処理条件の最適化を図り、
以ってその処理時間を短縮せしめようとするものである
。
〔問題点を解決するための手段〕
そのため本発明は上述した介在物除去方法及び介在物・
不純物除去方法において、減圧時に溶融金属中の可溶ガ
ス成分の平衡ガス分圧Ｐｘに対し、処理する炉内の雰囲
気圧力Ｐａを下式に示される条件で制御することを基本
的特徴としている。
Ｐ ｘ ？ ａ≧０ ． ０ ５ （ａｔｍ）この構
成の創案に当っては、次に述べることがそのベースとな
った。即ち、微細ガス気泡による介在物トラップ効率は
、微細ガス気泡生成量が同じであれば，気泡径が小さい
程又浴の深い所から生成する程良好になる．又ガス気泡
の浮上で溶融スラグとの界面をばたつかせ、反応界面積
の増大を図る場合にもその反応効率の面からは気泡径が
小さい程良い．一方、気泡発生条件としては、例えば第
２図に示すように可溶ガスＸを溶湯（１）中にパブリン
グして溶かした場合、そのガス成分（Ｘ）が微細ガス気
泡（２）として発生するための条件は、その平衡ガス分
圧Ｐｘに対し、次式を満たすものでなければならない。
２ σ
Ｐｘ ≧ Ｐａ ＋ρｇｈ＋−
ｒ
Ｐａ： 脱ガス時の炉内雰囲気圧力
ｇ ： 重力加速度
ｈ ： 気泡発生深さ
σ ：溶湯の表面張力
ｒ ：臨界気泡半径
該式から明らかように、炉内の雰囲気圧力Ｐａが減圧時
に低い値となればなる程、微細ガス気泡（２）が発生し
易くなる。又浴の深い（ｈの大きい）所からの気泡（２
）発生も可能となるし、更に該気泡（２）の径自身も小
さいものが得られ易くなる．そこで本発明者等は、後述
する実施例の試験を行ない、その試験結果から、溶湯（
１）中の可溶ガス成分（Ｘ）の平衡ガス分圧Ｐｘに対し
、どの程度炉内の雰囲気圧力Ｐａを下げたら、介在物・
不純物の除去処理に有効かを明らかにした．即ち、減圧
処理中にＰｘ−Ｐａ≧０．０５ ａｔｍになるように圧
力を制御することにより、浴中深くから微細なガス気泡
を大量に発生させ，精錬効率を大幅に上昇させることが
可能であることを見い出し、以上の構成を本発明として
提案したものである。
〔実施例〕
以上本発明の具体的実施例につき説明する。
本発明者等は，５０ｔｏｎＶＡＤ設備内にＴ，（０）＝
＝ ２ ５ ｐｐｌ１、（Ｎ）＝ ２ ６ ０ｐｐｍの
溶鋼５０ｔｏｎを入れ、１６６０℃で６ ５ ０ ｔｏ
ｒｒに保ちながら、取鍋底部よりポーラスプラグで１０
分間かけて６Ｎ１１３のＮｔガスを吹込んだ．その後急
速に減圧しそのまま放置した．この時同時に取鍋底部か
らＡｒガスを３ Ｑ Ｎ Ｑ ／ｗｉｎでパブリングし
、溶鋼の撹拌を行なった。第１図は溶鋼中のＮ８ガスの
平衡ガス分圧Ｐｘに対し炉内ガス圧力Ｐａをそれ以下に
下げた場合に、減圧開始当初Ｔ・[Industrial Application Field] This invention relates to a vacuum refining method for removing impurities and inclusions in molten metal. [Prior Art] The present inventors have proposed the following in order to improve the efficiency of removing inclusions from molten metal. That is, a gas soluble in the molten metal is bubbled into the molten metal to dissolve it, and fine gas bubbles are generated in the molten metal by reducing the pressure. According to this method, even minute inclusions in the molten metal are trapped by the bubbles and floated to the surface, resulting in extremely high inclusion removal ability. On the other hand, the present inventors got a hint from the bubble floating state in the above-mentioned inclusion removal, and developed the application of this to a degassing refining method or a slag refining method. That is, according to the above procedure, fine gas bubbles are generated in the molten metal, and their floating causes the interface between the molten metal and the atmosphere or the interface between the molten metal and molten slag to flutter, thereby increasing the reaction interface area. It is. Since these gas bubbles are generated from the entire area of the molten metal, the flutter at the interface extends over the entire area of the interface. Moreover, since a large number of fine gas bubbles are generated, the increase in the reaction interface area becomes remarkable, and the ability to remove impurities by degassing refining or slab refining becomes extremely high. [Problems to be solved by the invention] Both refining methods are very efficient methods for removing inclusions and impurities in molten metal and obtaining ultra-clean molten metal, but the decompression processing time still takes 20 minutes. There was a request to further shorten this time and improve efficiency. The present invention was devised in view of the above problems, and aims to optimize the reduced pressure processing conditions in the vacuum refining method described above.
This is intended to shorten the processing time. [Means for solving the problem] Therefore, the present invention provides the above-mentioned method for removing inclusions and
The basic feature of the impurity removal method is that the atmospheric pressure Pa in the processing furnace is controlled under the conditions shown in the following formula with respect to the equilibrium gas partial pressure Px of the soluble gas component in the molten metal during pressure reduction. Px? a≧0. 0 5 (atm) The following was the basis for creating this configuration. In other words, the inclusion trapping efficiency by fine gas bubbles becomes better as the bubble diameter becomes smaller and the bubbles are generated from deeper in the bath, provided that the amount of fine gas bubbles generated is the same. Also, when attempting to increase the reaction interface area by flapping the interface with the molten slag by floating gas bubbles, the smaller the bubble diameter, the better from the standpoint of reaction efficiency. On the other hand, as a bubble generation condition, for example, when soluble gas X is bubbled into molten metal (1) and dissolved as shown in Fig. 2, the gas component (X) is generated as fine gas bubbles (2). The conditions for this must satisfy the following equation for the equilibrium gas partial pressure Px. 2 σ Px ≧ Pa +ρgh+- r Pa: Atmospheric pressure in the furnace during degassing g: Gravitational acceleration h: Bubble generation depth σ: Surface tension of the molten metal r: Critical bubble radius As is clear from the equation, the atmosphere inside the furnace The lower the pressure Pa becomes during depressurization, the more likely fine gas bubbles (2) are generated. Also, air bubbles (2
) can be generated, and furthermore, the diameter of the bubbles (2) itself becomes smaller. Therefore, the present inventors conducted tests in the examples described below, and from the test results, the molten metal (
1) To what extent should the atmospheric pressure Pa in the furnace be lowered relative to the equilibrium gas partial pressure Px of the soluble gas component (X) in the mixture?
We clarified whether this method is effective in removing impurities. In other words, by controlling the pressure so that Px-Pa≧0.05 atm during the depressurization process, it is possible to generate a large amount of fine gas bubbles from deep within the bath, thereby greatly increasing the refining efficiency. We have discovered this and proposed the above configuration as the present invention. [Example] Specific examples of the present invention will be described above. The present inventors installed T, (0)=
= 25 ppl1, (N) = 50 tons of molten steel of 260 ppm and heated at 1660°C to 650 to
10 with a porous plug from the bottom of the ladle while keeping it at rr.
6N113 Nt gas was injected over a period of minutes. Afterwards, the pressure was rapidly reduced and the specimen was left as it was. At the same time, Ar gas was bubbled from the bottom of the ladle at a rate of 3 Q N Q /win to stir the molten steel. Figure 1 shows that when the furnace gas pressure Pa is lowered below the equilibrium gas partial pressure Px of N8 gas in molten steel, T
〔０〕が２５ｐｐｍあ
った溶鋼が６ ｐｐｍ以下となるまでに要する減圧開始
後の放置時間（脱酸時間）を調べ、グラフにしたもので
ある．尚、同図のＸ軸座標は、前記平衡ガス分圧Ｐｘと
炉内ガス圧力Ｐａとの差（Ｐｘ−Ｐａ）に関し、減圧処
理中におけるその平均を採ったものである。
同図から明らかなように、平均（Ｐｘ−Ｐａ）が０，０
５ ａｔｍを境に脱酸に要する放置時間が大幅に短くな
っており、従って減圧時にこの差が０．０５ａｔｍ以上
になるよう（好ましくは０．１ａｔＩＩ１以上になるよ
う）に炉内圧力Ｐａを制御することで、全体の処理時間
の短縮化が図れることが明らかとなった。
又、脱ガス精錬やスラグ精錬においても、一旦溶鋼中八
Ｎ２ガスを吹込んで後の減圧処理時に、上記の範囲の圧
力差になるように炉内圧力Ｐａを制御することでそれぞ
れ脱Ｈ反応、脱硫反応の進行が著しくなり、処理時間の
短縮化に有効であることを確認している。
尚、減圧時に、炉内の雰囲気圧力Ｐａを急激に低くする
と、微細ガス気泡のみが大量に生成し、介在物をトラッ
プせずに浮上し抜け出してしまうので、可溶ガス成分（
Ｘ）の脱ガス挙動を見ながら或いは予測して炉内の雰囲
気圧力Ｐａを適宜制御し、結果として平衡ガス分圧Ｐｘ
との差の平均が上述の範囲となるようにすると良い。This is a graph of the standing time (deoxidation time) required after the start of decompression for the molten steel, which had 25 ppm of [0], to become 6 ppm or less. Note that the X-axis coordinate in the figure is the average of the difference (Px-Pa) between the equilibrium gas partial pressure Px and the furnace gas pressure Pa during the pressure reduction process. As is clear from the figure, the average (Px-Pa) is 0,0
The standing time required for deoxidation is significantly shorter after 5 atm, so the furnace pressure Pa is controlled so that this difference is 0.05 atm or more (preferably 0.1atII1 or more) when depressurizing. It has become clear that by doing so, the overall processing time can be shortened. In addition, in degassing refining and slag refining, the dehydration reaction and slag refining can be achieved by controlling the furnace pressure Pa so that the pressure difference is within the above range during the depressurization treatment after once injecting N2 gas into the molten steel. It has been confirmed that the desulfurization reaction progresses significantly and is effective in shortening processing time. Note that if the atmospheric pressure Pa in the furnace is suddenly lowered during depressurization, only fine gas bubbles will be generated in large quantities and will float up and escape without trapping inclusions, so soluble gas components (
The atmospheric pressure Pa in the furnace is appropriately controlled while observing or predicting the degassing behavior of X), and as a result, the equilibrium gas partial pressure Px
It is preferable that the average difference between the two values falls within the above range.
第１図は脱酸時間と平均（Ｐｘ−Ｐａ）の相関関係を示
すグラフ図、第２図は溶湯中に溶解せしめたガスの微細
ガス気泡発生条件を示す説明図である。
図中（１）は溶湯、（２）は微細ガス気泡を各示す。
脱酸峙間（分）FIG. 1 is a graph showing the correlation between deoxidation time and average (Px-Pa), and FIG. 2 is an explanatory diagram showing the conditions for generating fine gas bubbles in the gas dissolved in the molten metal. In the figure, (1) shows the molten metal, and (2) shows the fine gas bubbles. Deoxidation time (min)
Claims (1)
れと同時に或いはその後に減圧し、該溶融金属中に微細
ガス気泡を発生させ、この気泡にトラップせしめて溶融
金属中の介在物を除去する溶融金属の真空精錬法におい
て、減圧時に該溶融金属中の可溶ガス成分の平衡ガス分
圧Ｐｘに対し、処理する炉内の雰囲気圧力Ｐａを下式に
示される条件で制御することを特徴とする溶融金属の真
空精錬法。 Ｐｘ−Ｐａ≧０．０５（ａｔｍ） ２、溶融金属中に、これに可溶なガスを溶解せしめ、そ
れと同時に或いはその後に減圧し、該溶融金属中に微細
ガス気泡を発生させ、この気泡にトラップせしめて溶融
金属中の介在物を除去すると共に、該気泡の浮上により
溶融金属と雰囲気の界面および／または溶融金属と溶融
スラグの界面をばたつかせてその反応界面積を増大させ
、溶融金属中の不純物を除去する溶融金属の真空精錬法
において、減圧時に該溶融金属中の可溶ガス成分の平衡
ガス分圧Ｐｘに対し、処理する炉内の雰囲気圧力Ｐａを
下式に示される条件で制御することを特徴とする溶融金
属の真空精錬法。 Ｐｘ−Ｐａ≧０．０５（ａｔｍ）[Claims] 1. Dissolve a gas soluble in the molten metal, reduce the pressure at the same time or after that, generate fine gas bubbles in the molten metal, trap the gas in the molten metal, and melt the metal. In a vacuum refining method for molten metal to remove inclusions in the metal, the atmospheric pressure Pa in the processing furnace is expressed by the following formula with respect to the equilibrium gas partial pressure Px of the soluble gas component in the molten metal when the pressure is reduced. A vacuum refining method for molten metal characterized by controlled conditions. Px-Pa≧0.05 (atm) 2. Dissolve a soluble gas in the molten metal, and reduce the pressure at the same time or after that to generate fine gas bubbles in the molten metal, and In addition to removing inclusions in the molten metal by trapping them, the floating of the bubbles causes the interface between the molten metal and the atmosphere and/or the interface between the molten metal and molten slag to flutter, increasing the reaction interface area, and removing the molten metal. In the vacuum refining method of molten metal to remove impurities in the molten metal, the atmospheric pressure Pa in the processing furnace is set under the conditions shown in the following formula with respect to the equilibrium gas partial pressure Px of the soluble gas component in the molten metal when the pressure is reduced. A vacuum refining method for molten metal characterized by control. Px-Pa≧0.05 (atm)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10717889A JPH02290929A (en) | 1989-04-28 | 1989-04-28 | Vacuum refining method for molten metal |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10717889A JPH02290929A (en) | 1989-04-28 | 1989-04-28 | Vacuum refining method for molten metal |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH02290929A true JPH02290929A (en) | 1990-11-30 |
Family
ID=14452448
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP10717889A Pending JPH02290929A (en) | 1989-04-28 | 1989-04-28 | Vacuum refining method for molten metal |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH02290929A (en) |
-
1989
- 1989-04-28 JP JP10717889A patent/JPH02290929A/en active Pending
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