JP3987704B2 - Hot phosphorus dephosphorization method - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、溶銑の脱燐方法に関するものである。
【０００２】
【従来の技術】
近年、高級鋼製造に対する要請が増大するにつれて、低燐鋼を安く製造する方法が強く望まれている。溶銑の脱燐法としては、ＣａＯ−酸化鉄−ＣａＦ2系フラックスおよび炭酸ソーダ等が古くから用いられている。中でも、炭酸ソーダは脱燐能が極めて高く、低燐鋼を安定的に製造する方法として広く利用されてきた。
しかし、炭酸ソーダを単味で用いると、その分解反応により温度低下を招くこと、或いは溶銑中〔Ｃ〕との反応による蒸発ロスが多くコストが高くつくという欠点を有していた。そこで、少量のＮａ2ＯをＣａＯ−酸化鉄−ＣａＦ2系フラックスに配合してコストを低減する方法として、例えば特開昭６１−１５９５０６号公報に見られるようなＮａ2Ｏを３％（以下％は全てｍａｓｓ％を示す）以下の配合に抑えたＣａＯ−ＣａＦ2−ＳｉＯ2系スラグからなる脱燐剤が提案されている。
【０００３】
【発明が解決しようとする課題】
しかしながら、特開昭６１−１５９５０６号公報に示される方法では、１０％以上ものＣａＦ2 を含んだスラグであるため、耐火物溶損が激しいことによる操業上の課題およびフッ素の溶出に伴う環境への影響に配慮するために多くは使えないという課題が残っていた。
本発明は、ＣａＦ2 を積極的に添加すること無く、ＣａＯ−酸化鉄（Ｔ・Ｆｅ）にＮａ2 Ｏを僅かに添加して、脱燐反応効を飛躍的に高めて、低コストで溶銑脱燐を行うための方法を提供するものである。
【０００４】
【課題を解決するための手段】
本発明の要旨は以下の通りである。
（１）転炉を用いて、転炉にＣａＯ源とＮａ2Ｏ源を添加し、酸素を上吹きして脱燐処理をした後に生成するスラグの中の塩基度（％ＣａＯ／％ＳｉＯ2），Ｎａ2Ｏ，Ｔ・Ｆｅを、以下の条件を満たすように調整し、さらに脱燐処理後のスラグ中フッ素濃度を２ｍａｓｓ％以下に調整することを特徴とする溶銑の脱燐方法。
（％ＣａＯ／％ＳｉＯ2）＝１．２〜３．０
Ｎａ2Ｏ＝３．４〜６ｍａｓｓ％
Ｔ・Ｆｅ＝３〜２５ｍａｓｓ％
（２）ＣａＯ源として、転炉で鋼を製造した際に発生する転炉滓または転炉滓と溶鋼取鍋滓を使用する（１）記載の溶銑の脱燐方法。
（３）Ｎａ2Ｏ源として、鉄鋼精錬プロセスでソーダ灰を精錬剤として使用した際に発生するダストを使用する（１）記載の溶銑の脱燐方法。
【０００５】
【発明の実施の形態】
本発明者らは、少量のＮａ2 Ｏの配合で、高脱燐能を有するフラックスとして、ＣａＦ2 使用前提のＣａＦ2 −ＣａＯ−ＳｉＯ2 系スラグにＮａ2 Ｏを少量添加したフラックスの脱燐能が高いという知見（鉄と鋼，第７１年（１９８５），ｐ．６９３）にヒントを得て、必ずしもＣａＦ2 の存在が無くとも、十分高い脱燐能が得られるのではないかとの推測に基づき、ラボ実験を行った。
すなわち、１００ｋｇ大気溶解炉を用いて、１３５０℃の人工溶銑を溶製し、ＣａＯと少量のＮａ2 ＣＯ3 と酸化鉄の混合物で溶銑を脱燐した際、生成するスラグ組成を種々変えて脱燐率の変化を見た。
なお、処理前の溶銑成分は、［Ｃ］＝４．０〜４．５％，［Ｓｉ］＝０．１〜０．４％，［Ｍｎ］＝０．２〜０．３％，［Ｐ］＝０．０８〜０．１２％，［Ｓ］＝０．０２８〜０．０３３％であった。
【０００６】
図１は、生成スラグのＴ・Ｆｅが１０〜１５％のデータを対象に、脱燐率におよぼす生成スラグの塩基度（％ＣａＯ／％ＳｉＯ2 ）の影響を示したものである。図から分かるように（％ＣａＯ／％ＳｉＯ2 ）が高いほど脱燐率が向上しており、特に１．２を境にしてそれ以上で急激に高い値となり、少なくとも脱燐処理を仕上げるのに必要な７５％を超える安定した脱燐率が得られている。
図１に示したスラグには、いずれもＮａ2 Ｏを３％含んでおり、これにより良好に脱燐が進行している。また、（％ＣａＯ／％ＳｉＯ2 ）が３以上では脱燐率が飽和してしまう現象が認められた。（％ＣａＯ／％ＳｉＯ2 ）が増大するに従って、スラグの脱燐能が増大し、高い脱燐率が得られる現象は一般的であるが、（％ＣａＯ／％ＳｉＯ2 ）が３を超えると脱燐率が低下するとともにバラツキも大きくなっている。これは、スラグの過剰な高塩基度化に伴う滓化不良によるものである。すなわち、ＣａＯが多すぎて無駄に成るとともに、反応も不安定になる。したがって、適正な脱燐のための（％ＣａＯ／％ＳｉＯ2 ）は１．２〜３．０の範囲である。
【０００７】
図２は、生成スラグの（％ＣａＯ／％ＳｉＯ2 ）＝１．５〜２．５且つＮａ2Ｏ＝３〜５％のものを対象に、Ｔ・Ｆｅ％を変化させた時の脱燐率の変化を示した。
Ｔ・Ｆｅが３％より小さい場合は、酸化力不足で脱燐率が急激に低下する。また、Ｔ・Ｆｅが２５％より大きい場合は、生成スラグ中のＣａＯ濃度が希釈されて、脱燐能の急激な減少に伴って、脱燐率が急激に低下している。従って、脱燐のために適正なＴ・Ｆｅ濃度は、３〜２５％の範囲である。
【０００８】
図３は、生成スラグの（％ＣａＯ／％ＳｉＯ2 ）＝１．５〜２．５且つＴ・Ｆｅ＝１０〜１５％のものを対象に、％Ｎａ2 Ｏを変化させた時の脱燐率の変化を示した。Ｎａ2 Ｏが１％以上で、脱燐率の大きな向上効果が得られ、６％を超えると耐火物の溶損が激しくなり、操業上の支障をきたすし、反応効率も飽和する。従って、脱燐のための適正なＮａ2 Ｏ濃度は１〜６％の範囲である。
【０００９】
なお、脱燐処理後スラグ中には、ＭｎＯ，ＭｇＯ，Ａｌ2 Ｏ3 などの不可避的不純物が５〜２０％程度混入し、共存してくるが、脱燐反応そのものには殆ど影響が無く、図１〜図３の結果に影響を与えるものでは無い。
【００１０】
上記一連の実験に使用したＣａＯの代わりにＣａＯ分を多く含む転炉滓または転炉滓および溶鋼取鍋滓をリサイクル使用しても、脱燐のための上記適正範囲に脱燐スラグ組成を調整した場合は、図１〜図３と全く同じ効果を表すことも確認した。使用した転炉滓と溶鋼取鍋滓の化学組成の一例を、表１および表２に示した。
【００１１】
【表１】
【表２】
ここで言う溶鋼取鍋滓とは、転炉で鋼を製造した後、取鍋に溶鋼を受けた際、転炉から取鍋に流出したスラグであり、鋼を鋳造する迄に脱酸工程を経るために、Ａｌ2 Ｏ3 分を多く含むのが特徴的である。脱燐に対するＡｌ2 Ｏ3 分の影響としては、ＣａＯの滓化促進に有効なことから脱燐を促進することは有っても、阻害することは無い。
しかし、現実的には、ＣａＯ分にリサイクルスラグを活用する場合は、多量に発生する転炉滓が主体となり、溶鋼取鍋滓は補助的に添加する程度となるため、事実上脱燐反応には殆ど影響は与えない。
【００１４】
また、Ｎａ2 Ｏ源としてＮａ2 ＣＯ3 試薬の炭酸ナトリウム（炭酸ソーダとも言う）を使用したが、工業的にはソーダ灰を用いるのが一般的であり、上記Ｎａ2 ＣＯ3 試薬を用いた場合と全く同じ効果を有する。更に、本発明者らは、Ｎａ2 ＣＯ3 源として、鉄鋼精錬プロセスでソーダ灰を精錬剤として使用した際に発生するダスト（Ｎａ2 ＣＯ3 分を５０−９０％含む）をリサイクル活用する実験も行ったが、脱燐のための上記適正範囲に脱燐スラグ組成を調整した場合は、図１〜図３と全く同じ効果を表すことを確認した。
更に、ＣａＯ源として転炉滓または転炉滓および溶鋼取鍋滓を用い、且つソーダ灰精錬ダストを用いても、上記脱燐のための適正組成範囲にスラグを調整すれば、図１〜図３と全く同じ効果が得られることも確認した。
【００１５】
脱燐スラグ中のフッ素濃度に関しては、図４で示すように、２％を超えると耐火物の溶損が激しくなるので、２％以下に抑えるのが操業上望ましい。
【００１６】
【実施例】
１．溶銑温度
処理前温度：１２５０℃〜１３００℃
処理後温度：１３００℃〜１３５０℃
２．反応容器と溶銑量
上底吹き転炉 ３５０ｔ
３．脱燐剤添加方法
ＣａＯ源、Ｎａ2 Ｏ源、酸化鉄、酸素ガスを転炉内に上方より添加。
ＣａＯ原単位＝１０ｋｇ／ｔ一定として、Ｎａ2 Ｏ源および酸素源（酸化鉄および上吹き酸素ガス）を振らして、脱燐挙動を見た。
４．溶銑初期成分（％）
〔Ｃ〕＝４．０〜４．５％、〔Ｓｉ〕＝０．１０〜０．４０％、
〔Ｍｎ〕＝０．２〜０．４％、〔Ｐ〕＝０．０８０〜０．１１０％、
〔Ｓ〕＝０．０２８〜０．０３０％
５．操業条件の詳細および結果
表３にまとめて記す。
【００１７】
【表３】
表３は、本発明の実施例および比較例を示したものであり、実施例では、いずれも８９〜９３％と高い脱燐率が得られている。一方。比較例１では、（％ＣａＯ／％ＳｉＯ2 ）が低すぎて、また、比較例２ではＴ・Ｆｅが低すぎて、更に、比較例３はＮａ2 Ｏが低すぎて、適正範囲から外れるため、脱燐処理に必要な脱燐率の下限値７５％より低い低脱燐率になっている。
比較例４では脱燐率は高いが、Ｆ濃度が高すぎて、耐火物溶損が大きいと言う問題が生じている。
【００１９】
【発明の効果】
本発明によれば、脱燐処理操業コストの大幅低減と同時に、容易に低燐鋼等の高級鋼を製造できるので、本発明がこの種の産業分野にもたらす効果は極めて大きい。
【図面の簡単な説明】
【図１】（ＣａＯ／ＳｉＯ2 ）と脱燐率の関係を示す図。
【図２】Ｔ・Ｆｅと脱燐率の関係を示す図。
【図３】Ｎａ2 Ｏと脱燐率の関係を示す図。
【図４】Ｆと耐火物溶損の関係を示す図。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hot metal dephosphorization method .
[0002]
[Prior art]
In recent years, as demand for high-grade steel production increases, a method for producing low-phosphorus steel at low cost is strongly desired. As a hot metal dephosphorization method, CaO-iron oxide-CaF 2 flux, sodium carbonate, and the like have been used for a long time. Among them, sodium carbonate has a very high dephosphorization ability and has been widely used as a method for stably producing low phosphorus steel.
However, the use of sodium carbonate in a single taste, the decomposition reaction causing a temperature drop by, or cost much evaporation loss due to reaction with molten iron (C) had the disadvantage that costly. Therefore, as a method for reducing the cost by adding a small amount of Na 2 O to a CaO-iron oxide-CaF 2 type flux, for example, 3% of Na 2 O as shown in Japanese Patent Application Laid-Open No. 61-159506 (hereinafter referred to as “No. percent dephosphorization agent has been proposed consisting of CaO-CaF 2 -SiO 2 system slag suppressed all show the mass%) or less of the formulation.
[0003]
[Problems to be solved by the invention]
However, in the method disclosed in Japanese Patent Application Laid-Open No. 61-159506, since it is a slag containing 10% or more of CaF 2 , there are operational problems due to severe refractory erosion, and the environment accompanying elution of fluorine. The problem remains that many cannot be used to take into account the effects of
The present invention, without the addition of CaF 2 positively, CaO-iron oxide (T · Fe) slightly added Na 2 O, and dramatically increased the dephosphorization reaction efficiency, the molten iron at a low cost A method for performing dephosphorization is provided.
[0004]
[Means for Solving the Problems]
The gist of the present invention is as follows.
(1) Using a converter, a basicity (% CaO /% SiO 2) in slag produced after adding a CaO source and a Na 2 O source to the converter and dephosphorizing by blowing up oxygen. ), Na 2 O, T · Fe are adjusted so as to satisfy the following conditions, and the fluorine concentration in the slag after the dephosphorization treatment is adjusted to 2 mass% or less .
(% CaO /% SiO 2) = 1.2~3.0
Na 2 O = 3.4 to 6 mass %
T ・ Fe = 3-25 mass %
( 2 ) The hot metal dephosphorization method according to (1), wherein a converter slag or a converter slag and a ladle slag generated when steel is produced in a converter is used as a CaO source.
( 3 ) The hot metal dephosphorization method according to (1), wherein dust generated when soda ash is used as a refining agent in a steel refining process is used as a Na 2 O source.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
The present inventors have found that by blending a small amount of Na 2 O, high as dephosphorization capacity flux having the dephosphorization of flux was added a small amount of Na 2 O in CaF 2 -CaO-SiO 2 slag of CaF 2 used premise Based on the finding that the ability is high (Iron and steel, 71st year (1985), p.693), it is speculated that a sufficiently high dephosphorization ability can be obtained without the presence of CaF 2. Based on this, a laboratory experiment was conducted.
That is, when a 1350 ° C. artificial hot metal is melted using a 100 kg atmospheric melting furnace and the hot metal is dephosphorized with a mixture of CaO, a small amount of Na 2 CO 3 and iron oxide, the slag composition produced is changed in various ways. I saw a change in the phosphorus rate.
In addition, the hot metal component before processing is [C] = 4.0-4.5%, [Si] = 0.1-0.4%, [Mn] = 0.2-0.3%, [P ] = 0.08-0.12% and [S] = 0.080-0.033%.
[0006]
FIG. 1 shows the influence of the basicity (% CaO /% SiO 2 ) of the generated slag on the dephosphorization rate for data of 10 to 15% of T · Fe of the generated slag. As can be seen from the figure, the higher the (% CaO /% SiO 2 ), the higher the dephosphorization rate. In particular, the dephosphorization rate increases rapidly beyond 1.2, and at least to finish the dephosphorization treatment. A stable dephosphorization rate exceeding the required 75% is obtained.
All of the slags shown in FIG. 1 contain 3% Na 2 O, and thus dephosphorization proceeds well. In addition, when (% CaO /% SiO 2 ) was 3 or more, a phenomenon that the dephosphorization rate was saturated was observed. As (% CaO /% SiO 2 ) increases, the dephosphorization ability of the slag increases and a high dephosphorization rate is common, but when (% CaO /% SiO 2 ) exceeds 3, As the dephosphorization rate decreases, the variation also increases. This is due to poor hatching due to excessive basicity of slag. That is, too much CaO is wasted and the reaction becomes unstable. Therefore, (% CaO /% SiO 2 ) for the proper dephosphorization is in the range of 1.2 to 3.0.
[0007]
Figure 2, (% CaO /% SiO 2 ) of the product slag = 1.5-2.5 and targeting those Na 2 O = 3 to 5%, dephosphorization when changing the T · Fe% The change in rate was shown.
When T · Fe is less than 3%, the dephosphorization rate decreases rapidly due to insufficient oxidizing power. Further, when T · Fe is larger than 25%, the CaO concentration in the produced slag is diluted, and the dephosphorization rate is drastically decreased with the rapid decrease of the dephosphorization ability. Therefore, the proper T · Fe concentration for dephosphorization is in the range of 3 to 25%.
[0008]
FIG. 3 shows the dephosphorization when% Na 2 O is changed for the slag produced (% CaO /% SiO 2 ) = 1.5 to 2.5 and T · Fe = 10 to 15%. The change in rate was shown. When Na 2 O is 1% or more, a great effect of improving the dephosphorization rate is obtained, and when it exceeds 6%, the refractory melts severely, resulting in operational problems and saturation of the reaction efficiency. Therefore, the proper Na 2 O concentration for dephosphorization is in the range of 1-6%.
[0009]
In addition, in the slag after the dephosphorization treatment, inevitable impurities such as MnO, MgO, and Al 2 O 3 are mixed by about 5 to 20% and coexist, but there is almost no influence on the dephosphorization reaction itself. It does not affect the results of FIGS.
[0010]
Regardless of the CaO used in the above series of experiments, the dephosphorization slag composition is adjusted to the above-mentioned appropriate range for dephosphorization even if the recycler or converter fume containing a large amount of CaO or the molten steel ladle is recycled. In this case, it was confirmed that the same effect as in FIGS. Tables 1 and 2 show examples of chemical compositions of the used converter slag and molten steel ladle slag.
[0011]
[Table 1]
[Table 2]
The ladle ladle mentioned here is the slag that flows from the converter to the ladle when the ladle is subjected to molten steel after the steel is produced in the converter, and the deoxidation process is performed before the steel is cast. In order to pass, it is characteristic that it contains a lot of Al 2 O 3 component . As the influence of Al 2 O 3 on dephosphorization, it is effective in promoting the hatching of CaO, and therefore, although dephosphorization is promoted, it is not inhibited.
However, in reality, when recycling slag is used for the CaO content, the converter slag that is generated in large quantities is the main component, and the molten steel ladle slag is only added as a supplement. Has little effect.
[0014]
In addition, sodium carbonate of Na 2 CO 3 reagent (also referred to as sodium carbonate) was used as the Na 2 O source, but industrial use of soda ash is common, and the above Na 2 CO 3 reagent was used. Has exactly the same effect as the case. Furthermore, the present inventors, Na as 2 CO 3 source, utilizing recycled dust (Na including 2 CO 3 minutes 50-90%) that occurs when using soda ash as a refining agent in the steel refining process experiments However, it was confirmed that when the dephosphorization slag composition was adjusted to the appropriate range for dephosphorization, the same effect as in FIGS.
Furthermore, even if a converter slag or a converter slag and a molten steel ladle slag are used as a CaO source and soda ash refining dust is used, if the slag is adjusted to an appropriate composition range for dephosphorization, FIG. It was also confirmed that exactly the same effect as 3 was obtained.
[0015]
Regarding the fluorine concentration in the dephosphorization slag, as shown in FIG. 4, if it exceeds 2%, the refractory melts severely, so it is desirable to keep it to 2% or less.
[0016]
【Example】
1. Hot metal temperature Pretreatment temperature: 1250 ° C-1300 ° C
Post-treatment temperature: 1300 ° C to 1350 ° C
2. 350t of reaction vessel and hot metal amount top bottom blowing converter
3. Dephosphorizing agent addition method CaO source, Na 2 O source, iron oxide and oxygen gas are added into the converter from above.
The dephosphorization behavior was observed by shaking the Na 2 O source and the oxygen source (iron oxide and top-blown oxygen gas) with the CaO basic unit = 10 kg / t constant.
4). Hot metal initial component (%)
[C] = 4.0 to 4.5%, [Si] = 0.10 to 0.40%,
[Mn] = 0.2 to 0.4%, [P] = 0.080 to 0.110%,
[S] = 0.028-0.030%
5). Details of operating conditions and results are summarized in Table 3.
[0017]
[Table 3]
Table 3 shows examples and comparative examples of the present invention. In the examples, a high dephosphorization rate of 89 to 93% was obtained. on the other hand. In Comparative Example 1, (% CaO /% SiO 2 ) is too low, in Comparative Example 2, T · Fe is too low, and in Comparative Example 3, Na 2 O is too low, which is out of the proper range. Therefore, the low dephosphorization rate is lower than the lower limit 75% of the dephosphorization rate necessary for the dephosphorization treatment.
In Comparative Example 4, the dephosphorization rate is high, but the problem is that the F concentration is too high and the refractory melt damage is large.
[0019]
【The invention's effect】
According to the present invention, high-grade steel such as low-phosphorus steel can be easily manufactured at the same time as the cost of dephosphorization treatment is greatly reduced, and thus the effect of the present invention on this type of industrial field is extremely great.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between (CaO / SiO 2 ) and the dephosphorization rate.
FIG. 2 is a graph showing the relationship between T · Fe and the dephosphorization rate.
FIG. 3 is a graph showing the relationship between Na 2 O and the dephosphorization rate.
FIG. 4 is a diagram showing the relationship between F and refractory material damage.
Claims (3)
（％ＣａＯ／％ＳｉＯ2）＝１．２〜３．０
Ｎａ2Ｏ＝３．４〜６ｍａｓｓ％
Ｔ・Ｆｅ＝３〜２５ｍａｓｓ％Using the converter, the CaO source and the Na 2 O source were added to the converter, and the basicity, Na 2 O, T · Fe in the slag generated after dephosphorization treatment by blowing up oxygen, dephosphorization methods molten iron, characterized in that the following conditions were adjusted so as to satisfy the further adjusting the slag fluorine concentration after dephosphorization below 2mass%.
(% CaO /% SiO 2) = 1.2~3.0
Na 2 O = 3.4 to 6 mass %
T ・ Fe = 3-25 mass %
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