JP3987823B2 - Method for reforming ladle slag - Google Patents
Method for reforming ladle slag Download PDFInfo
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- JP3987823B2 JP3987823B2 JP2003320911A JP2003320911A JP3987823B2 JP 3987823 B2 JP3987823 B2 JP 3987823B2 JP 2003320911 A JP2003320911 A JP 2003320911A JP 2003320911 A JP2003320911 A JP 2003320911A JP 3987823 B2 JP3987823 B2 JP 3987823B2
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- 239000002893 slag Substances 0.000 title claims description 48
- 238000002407 reforming Methods 0.000 title claims description 16
- 238000000034 method Methods 0.000 title claims description 13
- 229910000831 Steel Inorganic materials 0.000 claims description 49
- 239000010959 steel Substances 0.000 claims description 49
- 229910052761 rare earth metal Inorganic materials 0.000 claims description 25
- 239000000654 additive Substances 0.000 claims description 15
- 230000000996 additive effect Effects 0.000 claims description 15
- 229910018125 Al-Si Inorganic materials 0.000 claims description 5
- 229910018520 Al—Si Inorganic materials 0.000 claims description 5
- 229910052779 Neodymium Inorganic materials 0.000 claims description 4
- 229910052777 Praseodymium Inorganic materials 0.000 claims description 4
- 229910052746 lanthanum Inorganic materials 0.000 claims description 4
- 239000000700 radioactive tracer Substances 0.000 claims description 4
- 230000005587 bubbling Effects 0.000 claims description 3
- 238000003756 stirring Methods 0.000 description 17
- 230000003647 oxidation Effects 0.000 description 8
- 238000007254 oxidation reaction Methods 0.000 description 8
- 230000003749 cleanliness Effects 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 239000003607 modifier Substances 0.000 description 4
- 101150006573 PAN1 gene Proteins 0.000 description 3
- 238000005266 casting Methods 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 230000007423 decrease Effects 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 229910052684 Cerium Inorganic materials 0.000 description 1
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 238000010405 reoxidation reaction Methods 0.000 description 1
- 238000009849 vacuum degassing Methods 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
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Description
本発明は、Ａｌ脱酸またはＡｌ-Ｓｉ脱酸した溶鋼を収納した溶鋼中に添加した取鍋内スラグの改質方法に関するものである。 The present invention relates to a method for reforming slag in a ladle added to molten steel containing molten steel that has undergone Al deoxidation or Al-Si deoxidation.
Ａｌ脱酸またはＡｌ-Ｓｉ脱酸した溶鋼を取鍋に収納したとき、溶鋼表面のスラグに含まれるＦｅＯ，ＭｇＯ等の低級酸化物によって溶鋼中のＡｌが再酸化され、アルミナが生成される。その結果、鋼の清浄性が悪化し、鋼の靭性低下、鋼の表面品位低下、鋳造時ノズル詰まりなどが発生する。 When Al deoxidized or Al-Si deoxidized molten steel is stored in a ladle, Al in the molten steel is reoxidized by lower oxides such as FeO and MgO contained in the slag on the surface of the molten steel to produce alumina. As a result, the cleanliness of the steel deteriorates, and the toughness of the steel decreases, the surface quality of the steel decreases, and the nozzle clogging occurs during casting.
そこで従来から特許文献２〜４に示されるように、取鍋のスラグ上に改質材を添加することにより、スラグ中の低級酸化物を還元あるいは希釈し、溶鋼中のAｌの再酸化を抑制する方法が用いられている。これらの特許文献には、スラグ上にＡｌ，Ｓｉ，Ｔｉ，Ｃａ，Ｍｇ，Ｚｒ，ＭｇＯ，ＣａＯ−Ａｌ２Ｏ３等のスラグ改質材を添加することが開示されている。
Therefore, as shown in
しかし、これらのスラグ改質材は還元力が不足しており、改質のために多量の添加を必要とする。また、溶鋼の清浄性を悪化させるのは主としてスラグが溶鋼と接する溶鋼側の界面であるから、スラグ上面から改質材を投入する場合には大量の投入が必要となる。このように従来の改質法では、改質材の多量添加を必要とし、コスト面の問題があった。
本発明は上記した従来の問題点を解決し、多量のスラグ改質材を用いることなく、鋼の清浄性を向上させることができ、鋼の靭性向上、表面品位向上、鋳造時ノズル詰まりの抑制などの効果を得ることができる取鍋内スラグの改質方法を提供するためになされたものである。 The present invention solves the above-mentioned conventional problems, can improve the cleanliness of steel without using a large amount of slag modifier, improves the toughness of the steel, improves the surface quality, and suppresses nozzle clogging during casting. It is made in order to provide the modification | reformation method of the slag in a ladle which can acquire the effects of these.
上記の課題を解決するためになされた本発明の取鍋内スラグの改質方法は、Ａｌ脱酸またはＡｌ-Ｓｉ脱酸した溶鋼中に、Ｃｅを含む希土類元素添加剤をＣｅ濃度が３ｐｐｍ以上となるように添加したうえ、溶鋼中に添加したＳをトレーサーとして、平衡濃度の±５％に達した時間として定義される均一混合時間τの２〜１０倍の時間にわたり、ＣＡＳ，ＲＨ、ボトムバブリングのいずれかの方法によって溶鋼を攪拌することにより、上記希土類元素添加剤により取鍋内スラグを還元することを特徴とするものである。なお、Ｃｅを含む希土類元素添加剤として、ＣｅのほかにＬａ，Ｐｒ，Ｎｄから選択された１種以上の希土類元素を含むものを用いることができる。 The method for reforming slag in a ladle according to the present invention made to solve the above-mentioned problem is that a rare earth element additive containing Ce is added in a molten steel obtained by deoxidizing Al or deoxidizing Al-Si with a Ce concentration of 3 ppm or more. after having added to a, the S added to molten steel as a tracer, over 2 to 10 times the uniform mixing time τ, which is defined as the time reaches ± 5% of the equilibrium concentration, CAS, RH, bottom By stirring the molten steel by any method of bubbling , the slag in the ladle is reduced by the rare earth element additive . In addition, as the rare earth element additive containing Ce, one containing one or more rare earth elements selected from La, Pr, and Nd in addition to Ce can be used.
本発明の取鍋内スラグの改質方法によれば、Ａｌよりもはるかに強力な脱酸力を持つＲＥＭを溶鋼中に添加し、均一混合時間τの２〜１０倍の時間にわたり攪拌を行うことにより、ＲＥＭとスラグとの接触性を高め、スラグの溶鋼側界面を優先して改質することができる。このため、従来のような大量の改質材を用いることなく低コストでスラグを改質することができ、鋼の清浄性の向上、鋼の靭性向上、表面品位向上、鋳造時ノズル詰まりの抑制などの効果を得ることができる。 According to the method for reforming slag in a ladle according to the present invention, REM having a deoxidizing power much stronger than that of Al is added to molten steel, and stirring is performed for 2 to 10 times the uniform mixing time τ. Thereby, the contact property of REM and slag can be improved, and the molten steel side interface of slag can be improved preferentially. For this reason, it is possible to modify slag at low cost without using a large amount of modifying material as in the past, improving steel cleanliness, improving steel toughness, improving surface quality, and suppressing nozzle clogging during casting. Such effects can be obtained.
図１は本発明の実施形態を示す断面図である。溶鋼鍋１中のＡｌ脱酸またはＡｌ-Ｓｉ脱酸された溶鋼２に、Ｃｅを含む希土類元素添加剤３が添加され、スラグ４の改質が行われる。希土類元素添加剤３としては、ＣｅのほかにＬａ，Ｐｒ，Ｎｄから選択された１種以上の希土類元素を含むものを用いることができる。この実施形態では、溶鋼鍋１中の溶鋼２はＲＨ（真空脱ガス設備）５により攪拌処理されている。しかし、溶鋼２の攪拌方法はこの実施形態に示したＲＨのほか、ＣＡＳ，ＢＢ（ボトムバブリング）など任意の方法を採用することができる。
FIG. 1 is a sectional view showing an embodiment of the present invention. A rare
溶鋼２中に通常の合金成分を添加した場合には、均一混合時間τに相当する時間だけ攪拌を行うのが普通である。この均一混合時間τは、溶鋼中に添加した、通常はＳ、場合によってはＣｕ等をトレーサーとして、トレーサーの濃度が平衡濃度の±５％に達した時間として定義されたものである。しかし本発明では、希土類元素添加剤３を溶鋼２中に均一分散させることが目的ではないので、添加した後の攪拌時間は、均一混合時間τの２〜１０倍の時間とする。
When ordinary alloy components are added to the
このように希土類元素添加剤３の添加後に長時間の攪拌を行うことにより、希土類元素添加剤３は溶鋼２の表面のスラグ４と接触し、３ＭＯ＋２Ｒ→Ｒ２Ｏ３＋３Ｍの反応式（ただしＭ：Ｆｅ，Ｍｎ、Ｒ：Ｃｅ，Ｌａ，Ｐｒ，Ｎｄ）に従ってスラグ４中のＦｅＯやＭｎＯを還元し、スラグ４を改質する。
In this way, the rare
このように溶鋼２中に添加した希土類元素添加剤３によってスラグ４の改質を行わせるには、均一混合時間τの２倍以上の時間にわたり攪拌を継続することが必要である。図２のグラフは、攪拌時間によるスラグ酸化度の変化を示すもので、攪拌時間が均一混合時間τの２〜１０倍の範囲でスラグ酸化度が最も低下していることが分る。攪拌時間が長すぎると、溶鋼２の温度が低下するうえ、溶鋼鍋１などの耐火物の溶損も生じ易いので、コスト的にも見合わなくなる。
In order to cause the
なお、溶鋼の脱酸元素としてはＡｌが一般的である。しかし図３、図４のグラフに示すように、希土類元素添加剤はＡｌに比較して非常に微量で優れた脱酸効果を示す。図３、図４の縦軸はスラグ酸化度指数であり、スラグ中のＦｅＯ、ＭｎＯ等の低級酸化物の濃度を指数化したものである。すなわち、図４に示すように溶鋼中のスラグ酸化度指数を例えば６にするためには、Ａｌを用いるとその濃度は５００ｐｐｍとしなければならない。これに対して脱酸元素としてＲＥＭの一種であるＣｅを用いた場合、図３に示されるように、スラグ酸化度指数を同じ６にするために必要なＣｅの濃度は３ｐｐｍでよく、添加量を非常に少なくすることができる。このため本発明によれば、脱酸元素であるＣｅの添加量は従来に比較してごく微量でよい。 In addition, Al is common as a deoxidizing element for molten steel. However, as shown in the graphs of FIGS. 3 and 4, the rare earth element additive exhibits an excellent deoxidation effect in a very small amount as compared with Al. The vertical axis in FIGS. 3 and 4 is the slag oxidation degree index, which is an index of the concentration of lower oxides such as FeO and MnO in the slag. That is, as shown in FIG. 4 , in order to set the slag oxidation degree index in molten steel to 6, for example, when Al is used, its concentration must be 500 ppm. On the other hand, when Ce which is a kind of REM is used as a deoxidizing element, as shown in FIG. 3 , the concentration of Ce necessary for making the slag oxidation degree index the same 6 may be 3 ppm. Can be greatly reduced. Therefore, according to the present invention, the addition amount of Ce , which is a deoxidizing element, may be very small as compared with the conventional case.
また本発明によれば、従来のようにスラグ４の上面から改質材を投入するのではなく、溶鋼２との接触によりスラグ改質が行われる。このため鋼の性状に影響を与えるスラグ４の溶鋼側界面を優先して改質できる利点があり、この点からもスラグ改質材の過剰投入が不要となる。
Further, according to the present invention, the slag reforming is performed by contact with the
図１に示した溶鋼鍋内の１６００℃の極低炭素鋼の溶鋼２８０トンに対して、Ｃｅを含む希土類元素添加剤として表１に示す組成のＦｅ-Ｓｉ-ＲＥＭを１００ｋｇ添加し、ＲＨにより攪拌した。その均一混合時間τは７０秒であるのに対し、攪拌時間は１２０秒とし、攪拌時間／均一混合時間τの値は１.７である。この結果、溶鋼界面スラグ中のＴ−Ｆｅ＋ＭｎＯは４％となり、十分なスラグ改質がなされた。 100 kg of Fe-Si-REM having the composition shown in Table 1 as a rare earth element additive containing Ce is added to 280 tons of ultra-low carbon steel at 1600 ° C. in the molten steel pan shown in FIG. Stir. The uniform mixing time τ is 70 seconds, whereas the stirring time is 120 seconds, and the value of stirring time / uniform mixing time τ is 1.7. As a result, T-Fe + MnO in the molten steel interface slag was 4%, and sufficient slag reforming was performed.
第１の比較例：上記実施例において、他の条件は同一としたままでＲＥＭの添加をなくしたところ、溶鋼界面スラグ中のＦｅＯ＋ＭｎＯは２５％であり、スラグ改質がなされていない。 First comparative example: In the above example, when REM was not added while the other conditions were the same, FeO + MnO in the molten steel interface slag was 25%, and slag reforming was not performed.
第２の比較例：上記実施例において、ＲＥＭの添加量を１０ｋｇとし、攪拌時間を１０秒とした。この場合は攪拌時間／均一混合時間τの値は０.１４である。この場合、溶鋼界面スラグ中のＦｅＯ＋ＭｎＯは２２％であり、スラグ改質がなされていない。 Second Comparative Example: In the above example, the amount of REM added was 10 kg, and the stirring time was 10 seconds. In this case, the value of the stirring time / uniform mixing time τ is 0.14. In this case, FeO + MnO in the molten steel interface slag is 22%, and slag reforming is not performed.
第３の比較例：実施例と同一条件の溶鋼に表２に示す組成のショットＡｌを８００ｋｇ添加した後、１８０秒攪拌した。この場合は攪拌時間／均一混合時間τの値は２.５７である。この場合、溶鋼界面スラグ中のＦｅＯ＋ＭｎＯは６％でありかなりのスラグ改質がなされたが、ショットＡｌの添加量は実施例のＲＥＭ添加量に比較して８倍を要した。 Third Comparative Example: After 800 kg of shot Al having the composition shown in Table 2 was added to molten steel having the same conditions as in the example, the mixture was stirred for 180 seconds. In this case, the value of the stirring time / uniform mixing time τ is 2.57. In this case, FeO + MnO in the molten steel interface slag was 6%, and considerable slag reforming was performed. However, the amount of shot Al added was 8 times the amount of REM added in the example.
１ 溶鋼鍋
２ 溶鋼
３ Ｃｅを含む希土類元素添加剤
４ スラグ
５ ＲＨ
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| JP7087727B2 (en) * | 2018-06-26 | 2022-06-21 | 日本製鉄株式会社 | Steel manufacturing method |
| CN110512051B (en) * | 2019-09-05 | 2021-07-23 | 首钢集团有限公司 | Rare earth alloying method for avoiding continuous casting nozzle nodulation |
| CN113088791B (en) * | 2021-03-24 | 2022-02-25 | 钢铁研究总院 | Method for preparing rare earth steel by reducing rare earth oxide step by step in refining process |
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