JP2005226148A - Refinery method - Google Patents

Refinery method Download PDF

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JP2005226148A
JP2005226148A JP2004038510A JP2004038510A JP2005226148A JP 2005226148 A JP2005226148 A JP 2005226148A JP 2004038510 A JP2004038510 A JP 2004038510A JP 2004038510 A JP2004038510 A JP 2004038510A JP 2005226148 A JP2005226148 A JP 2005226148A
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slag
refining
temperature
solid phase
treatment
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JP4648640B2 (en
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Naoto Sasaki
直人 佐々木
Hiroshi Nagahama
洋 永浜
Yuji Ogawa
雄司 小川
Hideaki Suito
英昭 水渡
Akira Inoue
亮 井上
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Nippon Steel Corp
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  • Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a refinery method by which highly efficient treatment with high productivity is actualized using a little quantity of a refining agent by considering a solid phase in slag and the optimization of both solid and liquid phases. <P>SOLUTION: In the refinery method, the average composition of slag after being refined is adjusted in the equilibrium diagram of three elements so that a range in which either or both of 2CaO-SiO<SB>2</SB>-3CaO-P<SB>2</SB>O<SB>5</SB>solid solution and nCaO-P<SB>2</SB>O<SB>5</SB>solid (wherein, n is at least one among 2, 3, 4) exist is obtained at a temperature after the refining-treatment. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

本発明はＣａＯを主成分として用いる溶鉄の精錬処理において、少量で高効率かつ生産性の高い処理を可能とする脱りん方法に関する。   The present invention relates to a dephosphorization method that enables high-efficiency and high-productivity processing in a small amount in refining processing of molten iron using CaO as a main component.

溶鉄の精錬では不純物を安定的に除去するためにＣａＯを主成分に含む精錬剤が用いられる。スラグ発生量の低減や精錬コストの削減のためには少量の精錬剤で効率良く処理を行うことが望まれるが、ＣａＯ分として生石灰や石灰石などを直接添加する場合は滓化性が悪く、反応性が低いという問題があった。   In the refining of molten iron, a refining agent containing CaO as a main component is used to stably remove impurities. In order to reduce slag generation and refining costs, efficient treatment with a small amount of refining agent is desired. However, when quick lime or limestone is added directly as CaO, hatchability is poor and the reaction There was a problem of low nature.

この問題に対してこれまでに、例えば特許文献１では、ハロゲン化物などを添加することによって滓化性を改善した溶銑脱りん剤の製法が開示されているが、ハロゲン化物の添加はＣａＯ分の滓化を容易ならしめる一方で、精錬容器の耐火物の損傷を招くという問題がある。また、特許文献２では、ＣａＯを６０−７０％含む造滓剤（精錬剤）に、やはり滓化改善を目的としてＦｅ２Ｏ３などに加えてＡｌ２Ｏ３を８−１３％添加することを提案している。しかし、Ａｌ２Ｏ３を８％以上添加した場合、スラグの粘度が上昇しスロッピングが生じるなどの問題があり、また、Ａｌ２Ｏ３濃度が高い場合はＣａＯ濃度が相対的に低下するために脱りん能が低下するという問題がある。さらに、特許文献３では、処理中のスラグ条件を塩基度（％ＣａＯ／％ＳｉＯ２）＝１．２〜２．０、Ａｌ２Ｏ３＝２〜１６質量％、Ｔ．Ｆｅ＝７〜３０質量％にする溶銑の脱りん方法が開示されている。しかし、この場合もＡｌ２Ｏ３により脱りん能が低下するという問題がある。 To date, for example, Patent Document 1 discloses a method for producing a hot metal dephosphorizing agent that has improved hatchability by adding a halide or the like. While facilitating hatching, there is a problem of causing damage to the refractory in the smelting vessel. In Patent Document 2, the forming agent (refining agent) containing CaO 60-70%, the addition of Al 2 O 3 8-13% of still slag formation improved in addition to such Fe 2 O 3 for the purpose Has proposed. However, when Al 2 O 3 is added in an amount of 8% or more, there is a problem that the viscosity of the slag increases and slopping occurs, and when the Al 2 O 3 concentration is high, the CaO concentration relatively decreases. However, there is a problem that the dephosphorization ability decreases. Furthermore, Patent Document 3, the slag condition in process basicity (% CaO /% SiO 2) = 1.2~2.0, Al 2 O 3 = 2~16 wt%, T. A hot metal dephosphorization method in which Fe = 7 to 30% by mass is disclosed. However, even in this case, there is a problem that the dephosphorization ability is lowered by Al 2 O 3 .

一方で、本来、精錬反応中のスラグは固液共存状態であるが、スラグ内に存在する固相は反応に寄与しないと考えられていた。また、固液共存状態のスラグを定量的に取り扱う知見が乏しかったことから、従来多くの場合において例えば固液を区別しないスラグ全体の平均組成を用いて脱りん能を評価するなど、均一液相であるかの如き議論がなされてきた。しかし、実際のスラグは固液共存組成であり、発明者らが特許文献４に開示したように、スラグ中固相の積極利用により精錬の効率化が可能である。したがって、スラグを固液共存状態として捉え、固・液両相をそれぞれ最適化する必要があるが、上述した特許文献１、特許文献２および特許文献３ではＣａＯ分の滓化に主眼があり、未滓化ＣａＯ分以外のスラグ相の状態に関する考慮がなされていないという問題もある。   On the other hand, slag during the refining reaction is originally in a solid-liquid coexistence state, but it was thought that the solid phase present in the slag does not contribute to the reaction. In addition, since there has been little knowledge of quantitatively handling slag in the coexisting state of solid and liquid, in many conventional cases, for example, evaluating the dephosphorization ability using the average composition of the entire slag that does not distinguish between solid and liquid, etc. The debate has been made. However, the actual slag has a solid-liquid coexisting composition, and as disclosed by the inventors in Patent Document 4, the efficiency of refining can be improved by positive use of the solid phase in the slag. Therefore, it is necessary to consider the slag as a solid-liquid coexistence state and optimize both the solid and liquid phases. However, the above-mentioned Patent Document 1, Patent Document 2 and Patent Document 3 focus on the hatching of CaO, There is also a problem that no consideration is given to the state of the slag phase other than the undehydrated CaO content.

発明者らは、特許文献４において、処理後スラグ中に２ＣａＯ・ＳｉＯ２（以降Ｃ２Ｓと称す）固相を存在せしめる方法を提案したが、異なる温度範囲での適用に対して開示していない。
また、特許文献４では、溶銑の脱りんを想定している。Ｃ２Ｓ固相は、ＣａＯとＳｉＯ２の質量濃度の比が比較的低い、液相の脱りん能が低い範囲でしか存在しない。１６００℃超という高温での処理となる脱炭精錬においては、Ｃ２Ｓ固相を利用しようとする場合は液相の精錬能が低く、固相を利用したとしても充分な精錬能の確保が困難となるという問題がある。
特開昭５７−１３１０９号公報 特開昭５５−３４６５３号公報 特開平８−１５７９２１号公報 特開２００１−２６８０７号公報 Inventors have proposed a method in which a 2CaO.SiO 2 (hereinafter referred to as C 2 S) solid phase is present in the slag after treatment in Patent Document 4, but this is disclosed for application in different temperature ranges. Absent.
Moreover, in patent document 4, dephosphorization of hot metal is assumed. The C 2 S solid phase exists only in a range where the ratio of mass concentration of CaO and SiO 2 is relatively low and the dephosphorization ability of the liquid phase is low. In decarburization refining, which is a process at a high temperature of over 1600 ° C, the refining ability of the liquid phase is low when using the C 2 S solid phase, and even if the solid phase is used, sufficient refining ability can be secured. There is a problem that it becomes difficult.
JP-A-57-13109 JP 55-34653 A JP-A-8-157721 JP 2001-26807 A

本発明は、上記の問題を解決するもので、精錬処理温度に応じてスラグ内の固相を考慮し、固・液両相の最適化を考慮することによって、少量で高効率かつ生産性の高い処理が可能な精錬方法を提供することを目的とする。   The present invention solves the above-mentioned problems, considering the solid phase in the slag according to the refining treatment temperature, and considering the optimization of both the solid and liquid phases, so that high efficiency and productivity can be achieved in a small amount. It aims at providing the refining method in which high processing is possible.

本発明の要旨は以下の各方法にある。   The gist of the present invention resides in the following methods.

（１）精錬処理後スラグの平均組成が、精錬処理後温度において、２ＣａＯ・ＳｉＯ２−３ＣａＯ・Ｐ２Ｏ５固溶体、ｎＣａＯ・Ｐ２Ｏ５固相（ここでｎは２，３，４のうち少なくとも一つ）のいずれか一方または双方が存在する領域となる様に調整する、精錬方法。 (1) The average composition of the slag after refining treatment is 2CaO · SiO 2 -3CaO · P 2 O 5 solid solution, nCaO · P 2 O 5 solid phase (where n is 2,3,4) at the temperature after refining treatment A refining method of adjusting so that one or both of (at least one of them) exists.

（２）精錬処理後温度が１３２５℃未満の場合に、精錬処理後スラグの平均組成を、図１に示す斜線部の領域とする、前記（１）に記載の精錬方法。   (2) The refining method according to (1), wherein when the temperature after refining treatment is less than 1325 ° C., the average composition of the slag after refining treatment is set to the shaded area shown in FIG.

（３）精錬処理後温度が１３２５℃以上１３７５℃未満の場合に、精錬処理後スラグの平均組成を図２に示す斜線部の領域とする、前記（１）に記載の精錬方法。   (3) The refining method according to (1), wherein when the temperature after refining treatment is 1325 ° C. or higher and lower than 1375 ° C., the average composition of the slag after refining treatment is set to the shaded area shown in FIG.

（４）精錬処理後温度が１３７５℃以上１４２５℃未満の場合に、精錬処理後スラグの平均組成を図３に示す斜線部の領域とする、前記（１）に記載の精錬方法。   (4) The refining method according to (1), wherein when the temperature after refining treatment is 1375 ° C. or higher and lower than 1425 ° C., the average composition of the slag after refining treatment is set to the shaded area shown in FIG.

（５）精錬処理後温度が１４２５℃以上１４７５℃未満の場合に、精錬処理後スラグの平均組成を図４に示す斜線部の領域とする、前記（１）に記載の精錬方法。   (5) The refining method according to (1), wherein when the temperature after refining treatment is 1425 ° C. or higher and lower than 1475 ° C., the average composition of the slag after refining treatment is set to the shaded area shown in FIG.

（６）精錬処理後温度が１４７５℃以上１５２５℃未満の場合に、精錬処理後スラグの平均組成を図５に示す斜線部の領域とする、前記（１）に記載の精錬方法。   (6) The refining method according to (1), wherein when the temperature after refining treatment is 1475 ° C. or higher and lower than 1525 ° C., the average composition of the slag after refining treatment is set to the shaded area shown in FIG.

（７）精錬処理後温度が１５２５℃以上１５７５℃未満の場合に、精錬処理後スラグの平均組成を図６に示す斜線部の領域とする、前記（１）に記載の精錬方法。   (7) The refining method according to (1), wherein when the temperature after refining treatment is 1525 ° C. or higher and lower than 1575 ° C., the average composition of the slag after refining treatment is set to the shaded area shown in FIG.

（８）精錬処理後温度が１５７５℃以上１６２５℃未満の場合に、精錬処理後スラグの平均組成を図７に示す斜線部の領域とする、前記（１）に記載の精錬方法。   (8) The refining method according to (1), wherein when the temperature after refining treatment is 1575 ° C. or higher and lower than 1625 ° C., the average composition of the slag after refining treatment is the hatched area shown in FIG.

（９）精錬処理後温度が１６２５℃以上１６７５℃未満の場合に、精錬処理後スラグの平均組成を図８に示す斜線部の領域とする、前記（１）に記載の精錬方法。   (9) The refining method according to (1), wherein when the temperature after refining treatment is 1625 ° C. or higher and lower than 1675 ° C., the average composition of the slag after refining treatment is set to the shaded area shown in FIG.

（１０）精錬処理後温度が１６７５℃以上１７２５℃未満の場合に、精錬処理後スラグの平均組成を図９に示す斜線部の領域とする、前記（１）に記載の精錬方法。   (10) The refining method according to (1), wherein when the temperature after refining treatment is 1675 ° C. or higher and lower than 1725 ° C., the average composition of the slag after refining treatment is set to the shaded area shown in FIG.

（１１）精錬処理後温度が１７２５℃以上１７７５℃未満の場合に、精錬処理後スラグの平均組成を図１０に示す斜線部の領域とする、前記（１）に記載の精錬方法。   (11) The refining method according to (1), wherein when the temperature after refining treatment is 1725 ° C. or higher and lower than 1775 ° C., the average composition of the slag after refining treatment is set to the shaded area shown in FIG.

（１２）精錬処理後温度が１７７５℃以上の場合に、精錬処理後のスラグ平均組成を図１１に示す斜線部の領域とする、前記（１）に記載の精錬方法。   (12) The refining method according to (1), wherein when the temperature after refining treatment is 1775 ° C. or higher, the slag average composition after refining treatment is set to the shaded area shown in FIG.

（１３）精錬処理後スラグにおける、２ＣａＯ・ＳｉＯ２−３ＣａＯ・Ｐ２Ｏ５固溶体、ｎＣａＯ・Ｐ２Ｏ５固相（ここでｎは２，３，４のうち少なくとも一つ）のいずれか一方または双方を、精錬処理後スラグ全体の５〜８０質量％とする、前記（１）〜（１２）のいずれか１つに記載の精錬方法。 (13) One of 2CaO · SiO 2 -3CaO · P 2 O 5 solid solution and nCaO · P 2 O 5 solid phase (where n is at least one of 2, 3 and 4) in the slag after refining treatment Or the refining method as described in any one of said (1)-(12) which sets both to 5-80 mass% of the whole slag after a refining process.

（１４）精錬処理後スラグにおける、２ＣａＯ・ＳｉＯ２−３ＣａＯ・Ｐ２Ｏ５固溶体、ｎＣａＯ・Ｐ２Ｏ５固相（ここでｎは２，３，４のうち少なくとも一つ）のいずれか一方または双方の固相中のＰ濃度を、それ以外の相の平均Ｐ濃度よりも高くする、前記（１）〜（１３）のいずれか１つに記載の精錬方法。 (14) One of 2CaO · SiO 2 -3CaO · P 2 O 5 solid solution and nCaO · P 2 O 5 solid phase (where n is at least one of 2, 3, 4) in the slag after refining treatment Alternatively, the refining method according to any one of (1) to (13), wherein the P concentration in both solid phases is higher than the average P concentration in the other phases.

（１５）精錬処理時間のうち精錬処理開始時から５０％〜８０％が経過する期間内の任意の時期のスラグの平均組成を、図１〜図１１をそれぞれ用いて求まる液相率９０％以上の組成領域とする、前記（２）〜（１４）のいずれか１つに記載の精錬方法。   (15) A liquid phase ratio of 90% or more obtained from the average composition of slag at any time within a period in which 50% to 80% elapses from the start of the refining process in the refining process time. The refining method according to any one of (2) to (14), wherein

（１６）精錬処理用フラックスとして、ハロゲン化物を含まないものを用いることを特徴とする（１）〜（１５）のいずれかに記載の精錬方法。   (16) The refining method according to any one of (1) to (15), wherein a flux not containing halide is used as a refining treatment flux.

本発明によって、スラグ内の固相を考慮し、固・液両相の最適化を考慮し、少量で高効率かつ生産性の高い処理が可能な脱りん法を得ることができる。   According to the present invention, a dephosphorization method capable of high-efficiency and high-productivity processing in a small amount can be obtained in consideration of the solid phase in the slag and the optimization of both the solid and liquid phases.

本発明者らは、精錬処理後温度に応じて、スラグの組成を適切な範囲に調整することで、スラグ内の固・液両相の最適化を図り、効率良く脱りんを行えることを新たに見出した。   The inventors of the present invention have made it possible to optimize the solid and liquid phases in the slag by adjusting the composition of the slag to an appropriate range according to the temperature after the refining treatment, and to newly perform dephosphorization efficiently. I found it.

スラグの組成を精錬処理温度に応じて適切に調整することによる脱りん反応の形態は２つあり、これらを適宜、単独または併用させることができる。   There are two forms of dephosphorization reaction by appropriately adjusting the composition of slag according to the refining treatment temperature, and these can be used alone or in combination as appropriate.

以下に、これら２つの脱りん反応の形態について説明する。   Below, the form of these two dephosphorization reactions is demonstrated.

まず、１つ目の形態は、スラグ液相中にＰが含まれる場合に、５０μｍ程度の粒径のＣ２Ｓ固相が５秒程度で周囲の液相に見合った組成の２ＣａＯ・ＳｉＯ２と３ＣａＯ・Ｐ２Ｏ５との固溶体（以降Ｃ２ＳＳＳと称す）に変化するものである。 First, first embodiment, when it is included P in the slag liquid phase, particle size of about 50 [mu] m C 2 S in the solid phase is commensurate with the periphery of the liquid phase in about 5 seconds composition 2CaO · SiO 2 And 3CaO · P 2 O 5 (hereinafter referred to as C 2 S SS ).

固相が関与する反応における従来からの技術常識では、このような短時間で反応が平衡に到達することはほとんど考えられておらず、この知見は本発明者らの詳細な研究を通して初めて明らかにされたものである。   In the conventional technical common sense in the reaction involving the solid phase, it is hardly considered that the reaction reaches the equilibrium in such a short time, and this knowledge is revealed for the first time through the detailed study of the present inventors. It has been done.

したがって、精錬処理中のスラグにＣ２Ｓを固相として存在せしめることができる様に、精錬処理温度に応じてスラグの組成を調整することによって、遅延なくＣ２Ｓ相とＰとが反応してＣ２ＳＳＳを生じ、固相内にＰを濃縮しスラグ全体の脱りん能を向上する手法を考案したものである。 Therefore, the C 2 S phase and P react without delay by adjusting the composition of the slag according to the refining treatment temperature so that C 2 S can exist as a solid phase in the slag during the refining treatment. Thus, C 2 S SS is generated and P is concentrated in the solid phase to devise a technique for improving the dephosphorization ability of the entire slag.

スラグ液相中にＰがわずかでも含まれていれば上記の固相内へのＰの濃縮が生じるが、スラグ全体を平均したＰ濃度が２質量％以上の場合に顕著である。   If even a small amount of P is contained in the slag liquid phase, the concentration of P in the solid phase occurs, but this is remarkable when the average P concentration of the entire slag is 2% by mass or more.

次に、２つ目の形態は、精錬反応中にｎＣａＯ・Ｐ２Ｏ５（ｎ＝４，３，２）といったＰを含む固相を晶出させるものである。 Next, the second form is to crystallize a solid phase containing P such as nCaO.P 2 O 5 (n = 4, 3, 2) during the refining reaction.

従来の平衡論的な知見では、例えばＣａＯ−ＳｉＯ２−ＦｅｔＯ系（ここでＦｅｔＯは２価と３価の鉄の酸化物の総和を意味しており、本明細書ではＦｅｔＯと記載する）におけるＣａＯ単相飽和領域では液相中にＰが存在しても、ｎＣａＯ・Ｐ２Ｏ５（ｎ＝４，３，２）といったＰを含む固相は存在しないと考えられてきた。 According to the conventional equilibrium theory knowledge, for example, the CaO—SiO 2 —Fe t O system (where Fe t O means the sum of divalent and trivalent iron oxides, and in this specification, Fe t In the CaO single-phase saturated region in O), even if P is present in the liquid phase, it is considered that there is no solid phase containing P such as nCaO · P 2 O 5 (n = 4, 3, 2). I came.

しかし、本発明者らの詳細な研究の結果、ＣａＯ飽和組成において液相中にＰが含まれていればｎＣａＯ・Ｐ２Ｏ５（ｎ＝４，３，２）が安定して存在することが明らかとなった。これは、ＣａＯと平衡する比較的ＣａＯ濃度の高い液相中にメタルから酸化されたＰが移行した際、Ｐ分とＣａＯ分が反応してｎＣａＯ・Ｐ２Ｏ５（ｎ＝４，３，２）固相が生成し晶出するためと考えられる。 However, as a result of detailed studies by the present inventors, nCaO.P 2 O 5 (n = 4, 3, 2) is stably present if P is contained in the liquid phase in the CaO saturated composition. Became clear. This is because when P oxidized from a metal is transferred into a liquid phase having a relatively high CaO concentration in equilibrium with CaO, the P content and CaO content react to cause nCaO · P 2 O 5 (n = 4, 3, 2) It is considered that a solid phase is generated and crystallizes.

スラグ液相中にＰがわずかでも含まれていれば上記の固相内へのＰの濃縮が生じるが、スラグ全体を平均したＰ濃度が２質量％以上の場合に顕著である。   If even a small amount of P is contained in the slag liquid phase, the concentration of P in the solid phase occurs, but this is remarkable when the average P concentration of the entire slag is 2% by mass or more.

また、ＦｅｔＯ濃度が吹酸等で減少することなく適切に維持された場合、不足したＣａＯ分を補うためにＣａＯ固相からＣａＯがスラグ液相に供給されると考えられる。 In addition, when the Fe t O concentration is appropriately maintained without being decreased by blowing acid or the like, it is considered that CaO is supplied from the CaO solid phase to the slag liquid phase in order to compensate for the insufficient CaO content.

このように、ＣａＯ固相が精錬処理中のスラグに存在する場合において、ＣａＯ固相内にＰを濃化させることによって液相中のＰ濃度が上昇せず、精錬能を向上できることを見出した。   As described above, when the CaO solid phase is present in the slag during the refining treatment, it was found that by concentrating P in the CaO solid phase, the P concentration in the liquid phase does not increase and the refining ability can be improved. .

従って、精錬処理中のスラグにＣａＯ固相を存在せしめることによって、ＣａＯとＰ分が反応してｎＣａＯ・Ｐ２Ｏ５固相を晶出させることで、Ｐを濃縮しスラグ全体の脱りん能を向上する手法を考案したものである。 Therefore, by allowing the CaO solid phase to be present in the slag during the refining process, the CaO and P components react to crystallize the nCaO · P 2 O 5 solid phase, thereby concentrating P and dephosphorizing the entire slag. A method to improve

上記の１つ目の形態のＣ２Ｓ固相を用いた場合と比較すると、２つ目の形態のｎＣａＯ・Ｐ２Ｏ５（ｎ＝４，３，２）固相を晶出させる場合の方が、平衡論的には脱りん能が良好である。しかし温度によっては固相率が著しく高くなり反応が阻害される。 Compared to the case of using the first form of the C 2 S solid phase, the second form of the nCaO · P 2 O 5 (n = 4, 3, 2) solid phase is crystallized. However, the dephosphorization ability is better in terms of equilibrium. However, depending on the temperature, the solid phase ratio becomes remarkably high and the reaction is inhibited.

従って、精錬処理前の溶銑のＰ濃度や、製品に要求されるＰレベルに応じて、Ｃ２Ｓ固相を用いる場合、ｎＣａＯ・Ｐ２Ｏ５（ｎ＝４，３，２）固相を晶出させる場合、或いはこれら両方を用いる場合を、適宜選択すれば良い。 Therefore, when using a C 2 S solid phase depending on the P concentration of the hot metal before refining treatment and the P level required for the product, the nCaO · P 2 O 5 (n = 4, 3, 2) solid phase is used. What is necessary is just to select suitably the case where it crystallizes, or the case where both of these are used.

また、脱炭精錬においては、通常約１６００℃程度と高温のため、Ｃ２Ｓ固相を脱りんに利用した場合、スラグ液相の精錬能が低いためにスラグ液相中のＰ濃度が上昇しにくく、Ｃ２Ｓ固相を用いたとしても、スラグ液相からスラグ中Ｃ２Ｓ固相へのＰの固溶が、効率良く進まないと言う問題が生じる場合もある。この様な場合は、ｎＣａＯ・Ｐ２Ｏ５（ｎ＝４，３，２）固相を晶出させる脱りんを選択することが好ましい。 Also, in decarburization refining, since the high temperature is usually about 1600 ° C, when the C 2 S solid phase is used for dephosphorization, the slag liquid phase refining ability is low, so the P concentration in the slag liquid phase increases. Even if a C 2 S solid phase is used, there may be a problem that the solid solution of P does not proceed efficiently from the slag liquid phase to the C 2 S solid phase in the slag. In such a case, it is preferable to select dephosphorization that crystallizes the nCaO · P 2 O 5 (n = 4, 3, 2) solid phase.

上記の事実に鑑み、精錬処理後スラグの平均組成が、精錬処理後温度において、２ＣａＯ・ＳｉＯ２−３ＣａＯ・Ｐ２Ｏ５固溶体、ｎＣａＯ・Ｐ２Ｏ５固相（ここでｎは２，３，４のうち少なくとも一つ）のいずれか一方または双方が存在する領域となる様に調整することを特徴とする反応効率の高い精錬方法を提案する。 In view of the above fact, the average composition of the slag after refining treatment is 2CaO · SiO 2 -3CaO · P 2 O 5 solid solution, nCaO · P 2 O 5 solid phase (where n is 2, 3) , 4), a refining method with high reaction efficiency, characterized in that adjustment is made so that one or both of them exist.

尚、ある温度においてＣ２Ｓ固相やＣａＯ固相を存在させるには、その温度におけるＣａＯ−ＳｉＯ２−ＦｅｔＯの３元系状態図を用いて、スラグ組成を調整することで、基本的には達成できる。 Note that the presence of C 2 S solid or CaO solid phase at a certain temperature, by using a ternary phase diagram of CaO-SiO 2 -Fe t O at that temperature, by adjusting the slag composition, the basic Can be achieved.

本願のスラグ組成を規定するに際し、「精錬処理後温度において」としたのは、スラグ組成を一定とした場合は、異なる温度において異なる固相率となる事実による。例えば、溶銑処理のような１３５０℃程度の温度における、ある組成のスラグのＣ２Ｓ固相率は、これと同一組成のスラグの脱炭処理のような１６５０℃程度の温度における固相率とは異なる。 In defining the slag composition of the present application, “at the temperature after the refining treatment” is based on the fact that when the slag composition is constant, the solid phase ratio is different at different temperatures. For example, the C 2 S solid fraction of a slag having a certain composition at a temperature of about 1350 ° C. as in the hot metal treatment is equal to the solid fraction at a temperature of about 1650 ° C. in the decarburization treatment of the slag having the same composition as this. Is different.

したがって、目的とする精錬処理の温度において、平衡論的に目的の固相が存在する組成を選択することが重要である。この考え方は、固相の反応への寄与を考慮して初めて提案されたものである。   Therefore, it is important to select a composition in which the target solid phase exists in an equilibrium manner at the target refining temperature. This idea was proposed for the first time in consideration of the contribution to the reaction of the solid phase.

また、精錬処理中ではなく、精錬処理後スラグの組成で規定しているのは、精錬処理中では精錬処理の進行に伴い投入した固体の副原料が溶解するため、精錬処理の途中では固相の中にＰが充分含まれていないためである。   In addition, the composition of the slag after the refining process is regulated by the slag after refining process, because the solid secondary material that was introduced with the progress of the refining process is dissolved during the refining process. This is because P is not sufficiently contained in.

さらに、スラグの平均組成とは、未溶解の副原料、固相、液相をすべて含んだスラグの組成と定義する。精錬処理後スラグに固相が２種類以上存在する場合でも、これらをすべて含有したものをスラグの平均組成とする。   Further, the average composition of slag is defined as the composition of slag including all undissolved auxiliary materials, solid phase, and liquid phase. Even when two or more kinds of solid phases exist in the slag after the refining treatment, the average composition of the slag is the one containing all of them.

また、精錬処理後スラグの組成はサンプリング箇所によって多少ばらついているものの、その影響はほとんど問題にはならない程度であることが確認されているため、任意の箇所からサンプルを採取すれば、代表性があると考えられる。   In addition, although the composition of the slag after refining treatment varies somewhat depending on the sampling location, it has been confirmed that the effect is almost non-problematic. It is believed that there is.

従って、スラグの平均組成を実際に管理する場合は、任意の箇所から採取した１ｇ以上のスラグサンプル全量の成分分析値を用いることが出来る。   Therefore, when the average composition of slag is actually managed, the component analysis value of the total amount of 1 g or more of slag sample collected from an arbitrary location can be used.

また、上述の通り、存在させる固相の種類は求める処理温度によって決定することができる。たとえば溶銑処理のような比較的低温で、予備処理として軽脱りんをする場合はＣ２ＳＳＳを存在させる様にスラグ組成を調整することで充分な脱りん能が得られる。一方で、予備処理をせずに脱炭工程で製品レベルまでＰを除去する場合には、ＣａＯ固相が共存する様にスラグ組成を調整することで、４ＣａＯ・Ｐ２Ｏ５相を共存せしめることができ、高い脱りん能が得られる。この考え方は、スラグを固液共存状態として捉え、固・液相それぞれの相の組成の最適化を提案するものである。 Further, as described above, the type of solid phase to be present can be determined by the required processing temperature. For example, when light dephosphorization is performed as a preliminary treatment at a relatively low temperature such as hot metal treatment, sufficient dephosphorization ability can be obtained by adjusting the slag composition so that C 2 S SS is present. On the other hand, when removing P to the product level in the decarburization step without pretreatment, the 4CaO · P 2 O 5 phase is allowed to coexist by adjusting the slag composition so that the CaO solid phase coexists. High dephosphorization ability. This concept proposes optimizing the composition of the solid and liquid phases, taking slag as a solid-liquid coexistence state.

上記の２例のスラグ組成の中間のような組成領域では、Ｃ２ＳＳＳとｎＣａＯ・Ｐ２Ｏ５相が共存する。また、スラグの混合状態によっては、スラグ中のＰ２Ｏ５濃度などがスラグ部位によって異なり、そのために４ＣａＯ・Ｐ２Ｏ５相と３ＣａＯ・Ｐ２Ｏ５相などが共存することもある。 In the composition region like the middle of the slag compositions of the above two examples, the C 2 S SS and the nCaO · P 2 O 5 phase coexist. Also, depending on the mixed state of the slag, such as P 2 O 5 concentration in the slag depends slag site, sometimes Accordingly etc. 4CaO · P 2 O 5 phase and 3CaO · P 2 O 5 phase coexist.

いずれの場合も液相中にわずかでもＰが存在すればＰを含有した固相を存在させることができるが、より顕著な濃縮のためには処理後のスラグ全体の平均組成でＰ２Ｏ５が２質量％以上あることが望ましい。 In any case, if even a small amount of P is present in the liquid phase, a solid phase containing P can be present. However, for more remarkable concentration, the average composition of the entire slag after treatment is P 2 O 5. Is preferably 2% by mass or more.

また、本願の「精錬処理後スラグ」とは、原則としては精錬処理が終了した後に、溶鉄とスラグの一部あるいは大半が分離される時点でのスラグを指す。但し、この時点でのスラグを管理できない場合は、例えば転炉であれば吹き止め時点、鍋やトーピードカーを用いた精錬では処理場を離れる時点で採取したスラグで管理しても良い。   In addition, the “slag after refining process” in the present application indicates a slag at the time when a part or most of the molten iron and slag are separated after the refining process is completed. However, when the slag at this time cannot be managed, for example, in the case of a converter, the slag may be managed at the time of blowing off, or in the refining using a pot or torpedo car, the slag collected at the time of leaving the treatment plant.

また、多くの場合、精錬終了後に、溶鉄と分離された後のスラグ組成はあまり変わらない。このため、排滓場などで採取されるスラグで管理することも可能である。   In many cases, the composition of the slag after separation from the molten iron does not change much after completion of the refining. For this reason, it is also possible to manage with slag collected at a dumping site.

いずれの場合においても、急冷されて反応中の状態を保持したスラグを採取して反応中の固相・液相を区別することが理想である。但し、徐冷スラグであっても、状態図や鉱物相の形態から反応中に固相であった相と徐冷中に晶析出した固相を区別することができる。   In any case, it is ideal to collect the slag that has been quenched and kept in the reaction state to distinguish the solid phase and the liquid phase during the reaction. However, even in the case of slow cooling slag, the phase that was a solid phase during the reaction and the solid phase that crystallized during the slow cooling can be distinguished from the phase diagram and the form of the mineral phase.

「精錬処理後温度」に関しても上記のスラグと同様に、溶鉄とスラグの一部あるいは大半が分離される時点での温度を意味している。但し、この時点での温度を管理できない場合は、例えば転炉であれば吹き止め時点、鍋やトーピードカーを用いた精錬では処理場を離れる時点の温度で管理しても良い。また、温度に関しては過去の実績から推定することも可能である。   The “temperature after refining treatment” also means the temperature at the time when part or most of the molten iron and slag are separated, as in the case of the above slag. However, if the temperature at this time cannot be managed, for example, in the case of a converter, the temperature may be controlled at the time of blowing off, or in the refining using a pot or torpedo car, the temperature at the time of leaving the treatment plant. Also, the temperature can be estimated from past results.

また、精錬処理後スラグの平均組成の制御は、溶鉄組成および投入する副原料を物質収支や過去の実績などを元に調整して行う。副原料としては通常製鋼工程で用いられるもので良く、例えば、生石灰、石灰石、消石灰などのＣａＯ含有物、珪砂、珪石などのＳｉＯ２含有物、鉄鉱石、ミルスケール、ダストなどの酸化鉄成分に加え、Ｍｎ鉱石、ドロマイト、さらには、転炉滓や使用済み耐火物などの製鋼工程で発生する副産物を使用することが可能である。 The average composition of the slag after the refining process is controlled by adjusting the molten iron composition and the auxiliary raw material to be added based on the material balance and past results. As an auxiliary material, it may be one normally used in the steel making process, for example, CaO containing materials such as quick lime, limestone, slaked lime, SiO 2 containing materials such as silica sand and silica, iron oxide components such as iron ore, mill scale, and dust. In addition, it is possible to use Mn ore, dolomite, and by-products generated in the steel making process such as converter dredging and used refractories.

Ｆｅ，Ｍｎ，Ｍｇ，およびＰなどはＣ２Ｓ固相に固溶するものであり、本発明ではこれらの固溶体を含めてＣ２Ｓ固相あるいはＣ２ＳＳＳとする。また、ＦｅはＣａＯ固相に固溶するものであり、本発明ではこの固溶体を含めてＣａＯ固相とする。さらに、Ｆｅ２Ｏ３はＣａＯと複合酸化物を形成することが知られているが、このＣａＯ−Ｆｅ２Ｏ３固相が存在する場合も液相の精錬能は大きく変わらず、またＣａＯの供給源でもあるため、この複合酸化物をＣａＯ固相とする。 Fe, Mn, Mg, P and the like are solid-dissolved in the C 2 S solid phase, and in the present invention, these solid solutions are included as C 2 S solid phase or C 2 S SS . In addition, Fe is a solid solution in a CaO solid phase, and in the present invention, this solid solution is included in the CaO solid phase. Furthermore, it is known that Fe 2 O 3 forms a complex oxide with CaO. However, even when this CaO—Fe 2 O 3 solid phase is present, the refining ability of the liquid phase does not change greatly, and the CaO Since it is also a supply source, this complex oxide is used as a CaO solid phase.

次に、具体的な精錬処理後温度において、精錬処理後スラグの平均組成に、２ＣａＯ・ＳｉＯ２−３ＣａＯ・Ｐ２Ｏ５固溶体、ｎＣａＯ・Ｐ２Ｏ５固相（ここでｎは２，３，４のうち少なくとも一つ）のいずれか一方または双方を存在させるために、それぞれの該当する温度でＣ２Ｓ固相やＣａＯ固相を存在させて良好な脱りんを行うためのスラグ組成の領域を、ＣａＯ−ＳｉＯ２−ＦｅｔＯの３元系状態図の図１〜１１の斜線部に示す。 Next, at a specific temperature after refining treatment, the average composition of the slag after refining treatment is changed to 2CaO · SiO 2 -3CaO · P 2 O 5 solid solution, nCaO · P 2 O 5 solid phase (where n is 2, 3 Slag composition for performing good dephosphorization in the presence of a C 2 S solid phase or a CaO solid phase at the respective corresponding temperatures. the region indicated by the shaded portion of Figure 1-11 ternary phase diagram of CaO-SiO 2 -Fe t O.

図１〜１１の斜線部の領域は、詳細な基礎実験を元に、精錬処理後温度５０℃きざみの範囲で、該当する温度範囲ごとに、最適なスラグ組成領域を提案したものである。   The region indicated by the shaded area in FIGS. 1 to 11 proposes an optimum slag composition region for each applicable temperature range within a temperature range of 50 ° C. after the refining process based on detailed basic experiments.

ここで、精錬処理後温度の範囲は５０℃としているが、温度範囲はより細かくする方が、精度の点ではより好ましくなる。但し、温度範囲が５０℃以下であれば、精度の点で許容できるため、温度範囲を５０℃として、図１〜１１を提案したものである。   Here, the range of the temperature after the refining treatment is 50 ° C., but it is more preferable in terms of accuracy to make the temperature range finer. However, if the temperature range is 50 ° C. or less, it is acceptable in terms of accuracy, and therefore, the temperature range is set to 50 ° C. and FIGS. 1 to 11 are proposed.

また、図１の精錬処理後温度範囲の下限は、溶銑の凝固温度と処理や搬送中の温度降下を考慮して１，２００℃とすることが好ましい。さらに、図１１の精錬処理後温度範囲の上限は、耐火物の損耗を考慮して１，８００℃とすることが好ましい。   Further, the lower limit of the temperature range after the refining treatment in FIG. 1 is preferably set to 1,200 ° C. in consideration of the solidification temperature of the hot metal and the temperature drop during the treatment and conveyance. Furthermore, the upper limit of the temperature range after the refining treatment in FIG. 11 is preferably set to 1,800 ° C. in consideration of wear of the refractory.

さらに、図１〜１１の斜線の領域は、Ａｌ２Ｏ３，ＭｎＯ，ＭｇＯ，Ｐ２Ｏ５濃度の合計が１０質量％以下の条件で、ＣａＯ−ＦｅＯ−ＳｉＯ２の３元系に割り戻して算出したものである。ここで、Ａｌ２Ｏ３，ＭｎＯ，ＭｇＯ，Ｐ２Ｏ５濃度の合計が１０質量％以下としたのは、不可避的に混入したこれらの成分の濃度の影響を、実際のスラグサンプルの分析値を用いて検討したところ、この濃度以下であれば、便宜的にＣａＯ−ＳｉＯ２−ＦｅｔＯの３元系状態図を用いても、本願発明の議論にほとんど影響がないためである。 Furthermore, the hatched region in FIGS. 1 to 11 is rebated into a CaO—FeO—SiO 2 ternary system under the condition that the total concentration of Al 2 O 3 , MnO, MgO, and P 2 O 5 is 10 mass% or less. Calculated. Here, the total concentration of Al 2 O 3 , MnO, MgO, and P 2 O 5 was set to 10% by mass or less because the influence of the concentration of these components inevitably mixed is an analysis value of an actual slag sample. It was examined using, if this concentration will be used ternary phase diagram of convenience CaO-SiO 2 -Fe t O, because there is almost no effect on the discussion of the present invention.

本願の図１〜１１は、従来知られているこの３元系の平衡状態図と比較すると３ＣａＯ・ＳｉＯ２の領域も含んでいる。本発明者らの実験によれば、Ｐ２Ｏ５の存在下ではＣ２Ｓの安定領域が拡大し、３ＣａＯ・ＳｉＯ２は確認されず、Ｐを固溶したＣ２Ｓ相が確認された。したがって図示した領域のスラグ組成に制御することによってＰを含有する固相を存在せしめることが可能となる。なお、太線および破線上の点も含む。 FIGS. 1 to 11 of the present application also include a region of 3CaO.SiO 2 as compared with the conventionally known ternary equilibrium diagram. According to the experiments by the present inventors, the stable region of C 2 S was expanded in the presence of P 2 O 5 , 3CaO · SiO 2 was not confirmed, and a C 2 S phase in which P was dissolved was confirmed. . Therefore, it is possible to make a solid phase containing P exist by controlling the slag composition in the illustrated region. In addition, the point on a thick line and a broken line is also included.

さらに、精錬処理後スラグにおける、２ＣａＯ・ＳｉＯ２−３ＣａＯ・Ｐ２Ｏ５固溶体、ｎＣａＯ・Ｐ２Ｏ５固相（ここでｎは２，３，４のうち少なくとも一つ）のいずれか一方または双方を、精錬処理後スラグ全体の５〜８０質量％とすることが好ましい。 Further, any one of 2CaO · SiO 2 -3CaO · P 2 O 5 solid solution and nCaO · P 2 O 5 solid phase (where n is at least one of 2, 3, 4) in the slag after refining treatment or Both are preferably 5 to 80% by mass of the entire slag after refining treatment.

ここで「精錬処理後スラグ全体」とは、未滓化石灰を含む精錬処理容器内の固液共存スラグを指す。上記の精錬処理後スラグにおける、２ＣａＯ・ＳｉＯ２−３ＣａＯ・Ｐ２Ｏ５固溶体、ｎＣａＯ・Ｐ２Ｏ５固相（ここでｎは２，３，４のうち少なくとも一つ）のいずれか一方または双方が５質量％未満の場合は、固相の効果が充分に得られにくく、逆に８０質量％超の場合は、固相率が高くなり、溶鉄からの脱りん反応に直接寄与する液相スラグ量が少なくなって脱りん反応が停滞し易くなる。 Here, the “entire slag after refining treatment” refers to solid-liquid coexistence slag in a refining treatment vessel containing uncontained lime. Any one of 2CaO · SiO 2 -3CaO · P 2 O 5 solid solution and nCaO · P 2 O 5 solid phase (where n is at least one of 2, 3, 4) in the slag after the refining treatment or When both are less than 5% by mass, it is difficult to obtain the effect of the solid phase. On the other hand, when it exceeds 80% by mass, the solid phase ratio increases, and the liquid phase contributes directly to the dephosphorization reaction from molten iron. The amount of slag is reduced and the dephosphorization reaction is likely to stagnate.

また、精錬処理後スラグにおける、２ＣａＯ・ＳｉＯ２−３ＣａＯ・Ｐ２Ｏ５固溶体、ｎＣａＯ・Ｐ２Ｏ５固相（ここでｎは２，３，４のうち少なくとも一つ）のいずれか一方または双方を、精錬処理後スラグ全体の５〜８０質量％とするには、図１から１１のそれぞれ相当する温度の図において、太線を各温度域における液相線、点Ａ，Ｂを固相組成、点Ｃを固相Ａ，Ｂと共存する液相組成として、固相率５〜８０質量％の範囲を基本的な周知の方法により求め、その組成にスラグ平均組成を制御することにより実施できる。 In addition, any one of 2CaO · SiO 2 -3CaO · P 2 O 5 solid solution and nCaO · P 2 O 5 solid phase (where n is at least one of 2, 3, 4) in the slag after refining treatment or In order to make both slag 5 to 80% by mass of the slag after refining treatment, in each of the temperature diagrams corresponding to FIGS. 1 to 11, the thick line represents the liquidus in each temperature region, and points A and B represent the solid phase composition. As a liquid phase composition in which the point C coexists with the solid phases A and B, a range of a solid phase ratio of 5 to 80% by mass can be obtained by a basic well-known method, and the slag average composition can be controlled by that composition. .

また、精錬処理後スラグにおける、２ＣａＯ・ＳｉＯ２−３ＣａＯ・Ｐ２Ｏ５固溶体、ｎＣａＯ・Ｐ２Ｏ５固相（ここでｎは２，３，４のうち少なくとも一つ）のいずれか一方または双方の固相中のＰ濃度を、それ以外の相の平均Ｐ濃度よりも高くすることが好ましい。 In addition, any one of 2CaO · SiO 2 -3CaO · P 2 O 5 solid solution and nCaO · P 2 O 5 solid phase (where n is at least one of 2, 3, 4) in the slag after refining treatment or It is preferable that the P concentration in both solid phases is higher than the average P concentration in the other phases.

反応中のスラグにＣ２Ｓ固相やＣａＯ固相を存在させることで、これらの固相中にはＰが固溶されたり、或いはｎＣａＯ・Ｐ２Ｏ５固相（ここでｎは２，３，４のうち少なくとも一つ）を生成する。 By allowing a C 2 S solid phase or a CaO solid phase to exist in the slag during the reaction, P is dissolved in these solid phases, or nCaO · P 2 O 5 solid phase (where n is 2, 3 or 4).

脱りん反応の進行に伴い、２ＣａＯ・ＳｉＯ２−３ＣａＯ・Ｐ２Ｏ５固溶体、ｎＣａＯ・Ｐ２Ｏ５固相（ここでｎは２，３，４のうち少なくとも一つ）が生成するため、これら生成した固相中のＰ濃度が増加する。 As the dephosphorization reaction proceeds, 2CaO · SiO 2 -3CaO · P 2 O 5 solid solution and nCaO · P 2 O 5 solid phase (where n is at least one of 2, 3, and 4) are generated. The P concentration in the generated solid phase increases.

従って、これらのＰ含有固相のＰ濃度が、液相やＰを含有しない固相のＰ濃度よりも高くなるまで脱りんを行うことで、スラグが液相のみであった場合よりも少ないスラグ量でより多量のＰをスラグ中に保つことができるため、精錬効率の面で好ましい。   Therefore, dephosphorization is carried out until the P concentration of these P-containing solid phases becomes higher than the P concentration of the solid phase not containing the liquid phase or P, so that less slag is obtained than when the slag is only the liquid phase. Since a larger amount of P can be kept in the slag, it is preferable in terms of refining efficiency.

また、精錬処理時間のうち精錬処理開始時から５０％〜８０％が経過する期間内の任意の時期のスラグの平均組成を、図１〜図１１をそれぞれ用いて求まる液相率９０％以上の組成領域とすることが好ましい。これは、精錬処理中のスラグ組成推移の制御指針を提案するものである。   In addition, the average composition of slag at any time within a period in which 50% to 80% elapses from the start of the refining process in the refining process time, and the liquid phase ratio obtained by using FIGS. A composition region is preferable. This proposes a control guideline for slag composition transition during the refining process.

精錬処理の末期に、スラグ脱りん能を良好に確保することは、スラグ中にＰを含有する固相を存在させることで達成できるが、精錬処理前半は相対的に溶鉄中Ｐ濃度が高いため、スラグ脱りん能が比較的低くても、脱りん速度は低下しない。   In the final stage of the refining process, it is possible to achieve a good slag dephosphorization ability by the presence of a solid phase containing P in the slag, but the P concentration in the molten iron is relatively high in the first half of the refining process. Even if the slag dephosphorization ability is relatively low, the dephosphorization rate does not decrease.

一方、相対的に溶鉄中Ｐ濃度が低くなり、スラグ液相中のＰ濃度が高くなる、精錬処理の後半においては、スラグ脱りん能が低いままであれば、脱りん速度は低下する。   On the other hand, in the second half of the refining process in which the P concentration in the molten iron is relatively low and the P concentration in the slag liquid phase is high, the dephosphorization rate decreases if the slag dephosphorization ability remains low.

そこで、精錬処理の後半に、スラグ中に固相を存在させてスラグ脱りん能を高くすることにより、精錬処理の後半も良好な脱りんを達成できる。   Therefore, in the second half of the refining treatment, a solid phase can be present in the slag to increase the slag dephosphorization ability, so that good dephosphorization can also be achieved in the second half of the refining treatment.

また、本発明者らの実験結果から、精錬処理の前半は、スラグ中に固相を多く存在させるよりも、むしろスラグ液相率を高くすることで、スラグ側物質移動が良好になるために、脱りん反応速度がより良好になることが明らかとなった。このため、精錬処理前半はスラグ液相率が高い条件が好ましい。   In addition, from the results of our experiments, the first half of the refining process is to increase the slag liquid phase ratio rather than having a large amount of solid phase in the slag, so that the slag-side mass transfer becomes better. It was revealed that the dephosphorization reaction rate was improved. For this reason, the conditions where the slag liquid phase rate is high are preferable in the first half of the refining treatment.

ここで精錬処理の前半とは、吹酸開始から吹止までの時間のうち５０％以上８０％以内を指す。５０％以上８０％以内とした理由は、５０％以上の場合に副原料の溶解の大部分が進みスラグ組成も安定するためであり、８０％以内においてはスラグの平衡論的な脱りん能よりも反応速度が重要、つまり、固相を生成せしめてスラグ全体の脱りん能を向上させるよりも、固相率を低位としてスラグ中の物質移動を促進した方が脱りんが向上するためである。   Here, the first half of the refining treatment refers to 50% or more and 80% or less of the time from the start of blowing acid to the stop of blowing. The reason why it is 50% or more and 80% or less is that when the amount is 50% or more, most of the secondary raw material is dissolved and the slag composition is stabilized, and within 80%, the equilibrium dephosphorization ability of the slag However, the reaction rate is important, that is, the dephosphorization is improved by promoting the mass transfer in the slag by lowering the solid phase rate rather than generating the solid phase and improving the dephosphorization ability of the whole slag. .

精錬処理の前半の期間内にスラグ液相率を高くすることで、鋼中Ｐ濃度が高い領域での反応速度を高く保つことが出来るため好ましい。   It is preferable to increase the slag liquid phase ratio during the first half of the refining treatment because the reaction rate in the region where the P concentration in steel is high can be kept high.

また精錬処理の後半とは、処理前半の期間内で図１〜図１１をそれぞれ用いて求まる液相率９０％以上の組成領域となった後の期間を指す。   Further, the latter half of the refining process refers to a period after a composition region having a liquid phase ratio of 90% or more obtained using each of FIGS.

精錬処理の後半のスラグの最適組成は、精錬処理の前半の期間内のスラグ液相率未満の領域とすることが望ましい。   It is desirable that the optimum composition of the slag in the second half of the refining process be an area that is less than the slag liquid phase ratio in the first half of the refining process.

また、本発明者らは、広範な温度域において３ｔ規模の溶鉄を用いた実験を行い、精錬処理前半の好ましいスラグ液相率とするためのスラグ平均組成を明らかとした。   In addition, the present inventors conducted experiments using 3t scale molten iron in a wide temperature range, and clarified the slag average composition for obtaining a preferable slag liquid phase ratio in the first half of the refining treatment.

まず、精錬処理前半のスラグ組成は、図１から１１の、太線を各温度域における液相線、点Ａ，Ｂを固相組成、点Ｃを固相Ａ，Ｂと共存する液相組成として求まる液相率９０％以上の領域とすることが好ましいことが判明した。   First, the slag composition in the first half of the refining process is shown in FIGS. 1 to 11, where the thick line is the liquid phase line in each temperature range, the points A and B are the solid phase composition, and the point C is the liquid phase composition coexisting with the solid phases A and B. It has been found that it is preferable to set the liquid phase ratio to be 90% or more.

また、精錬処理後半のスラグ組成は、同様に液相率９０％未満とすることが好ましい。   Similarly, the slag composition in the latter half of the refining treatment is preferably less than 90% of the liquid phase ratio.

図は吹止温度が該当する図を用いても良いが、実際には、計測あるいは推定した吹錬中の温度推移をもとに、当該温度領域の図を用いることが望ましい。   The figure may be a figure corresponding to the blowing temperature, but actually, it is desirable to use the figure of the temperature region based on the measured or estimated temperature transition during blowing.

本来、精錬処理スラグはＡｌ２Ｏ３，ＭｎＯ，ＭｇＯ，Ｐ２Ｏ５などを含んだ多元系であるため、これらを含んだ固相を考慮することが必要な場合がある。しかし、本実験では吹錬中に、耐火物起因と推測されるＭｇを含んだ固相が１〜５質量％程度存在していても、脱りんへの影響は認められなかったため、液相率を求めるに際し、上記の議論ではＡｌ２Ｏ３，ＭｎＯ，ＭｇＯ，Ｐ２Ｏ５の影響は無視しても良い。 Originally, the refining slag is a multi-component system containing Al 2 O 3 , MnO, MgO, P 2 O 5, etc., so it may be necessary to consider a solid phase containing these. However, in this experiment, there was no influence on dephosphorization even if there was about 1-5% by mass of Mg-containing solid phase presumed to be due to refractory during blowing. In the above discussion, the influence of Al 2 O 3 , MnO, MgO, P 2 O 5 may be ignored.

基本的な周知の方法として液相率・固相率の求め方は以下のようになる。例えば図１２の丸数字１の平均組成であるスラグは丸数字１の組成を持つ液相のみが存在することが考えられ、液相率１００％となる。また丸数字２の平均組成であれば、存在する固相は点Ａ（Ｃ２Ｓ）であり、したがって点Ａから丸数字２を通る液相線までの線分上で「てこの原理」を用いて、液相率が８０％、固相（Ｃ２Ｓ）が２０％と判明する。同様に、丸数字３は点Ａ、ＢすなわちＣ２Ｓ，ＣａＯの両相飽和領域で液相組成は点Ｃとなり、液相率およびＣ２Ｓ，ＣａＯ両固相率は点Ａ，Ｂ，Ｃを頂点とする三角形から求められる。すなわち、点Ａ，Ｂ，Ｃから引いた点（丸数字３）を通る直線が各対辺と交わる点をａ，ｂ，ｃとしたとき、各相の存在比はＡ相：Ｂ相：Ｃ相＝丸数字３〜ａ／Ａａ：丸数字３〜ｂ／Ｂｂ：丸数字３〜ｃ／Ｃｃとなる。ここで、丸数字３〜ａ／Ａａとは、（点（丸数字３）と点ａとを結ぶ線分の長さ）／（点Ａと点ａとを結ぶ線分の長さ）ということを意味している。丸数字３〜ｂ／Ｂｂおよび丸数字３〜ｃ／Ｃｃも同様である。 As a basic well-known method, the liquid phase ratio and the solid phase ratio are obtained as follows. For example, in the slag having the average composition of the circled numeral 1 in FIG. 12, it is considered that only the liquid phase having the composition of the circled numeral 1 exists, and the liquid phase ratio becomes 100%. If the average composition of the circled number 2 is present, the solid phase present is the point A (C 2 S). Therefore, the “leverage principle” is applied on the line segment from the point A to the liquidus line passing through the circled number 2. It is found that the liquid phase ratio is 80% and the solid phase (C 2 S) is 20%. Similarly, the circled numeral 3 is point A, B, that is, the liquid phase composition is point C in the C 2 S, CaO both phase saturation region, and the liquid phase ratio and the C 2 S, CaO both solid phase ratio are points A, B, It is obtained from a triangle having C as a vertex. That is, when a, b, and c are points where a straight line passing through points (circle numeral 3) drawn from points A, B, and C intersects the opposite sides, the abundance ratio of each phase is A phase: B phase: C phase = Circular number 3-a / Aa: Round number 3-b / Bb: Round number 3-c / Cc. Here, the circled numbers 3 to a / Aa are (the length of the line segment connecting the point (round numeral 3) and the point a) / (the length of the line segment connecting the point A and the point a). Means. The same applies to the circled numbers 3 to b / Bb and the circled numbers 3 to c / Cc.

また、点（丸数字４）の平均組成ではＣａＯ単相飽和であり、点Ｂ（ＣａＯ）を固相として丸数字１と同様の方法で液相率、固相率を求めることが出来る。１４７５℃未満の場合は図１〜４に示すように液相線がＣａＯ−ＳｉＯ２を結ぶ線と交わっていない。平均組成が点Ｄ，Ｅ，Ａを結ぶ三角形内にあるような、例えば点（丸数字５）で示した場合は、固相Ａ、Ｄ、液相Ｅの比を上述の点（丸数字３）で示した例と同様の手法で求めることが出来る。 In addition, the average composition at the point (circle numeral 4) is CaO single phase saturation, and the liquid phase ratio and the solid phase ratio can be obtained by the same method as the circle numeral 1 with the point B (CaO) as the solid phase. When the temperature is lower than 1475 ° C., the liquidus line does not intersect with the line connecting CaO—SiO 2 as shown in FIGS. When the average composition is within a triangle connecting points D, E, A, for example, indicated by a point (circle numeral 5), the ratio of solid phases A, D and liquid phase E is set to the above-mentioned point (circle numeral 3). ) Can be obtained by a method similar to that shown in the example.

スラグ液相率は、温度とスラグの組成で決定されるが、温度は処理の都合上制御することが通常は困難である。そのため、吹錬中にスラグ組成を変化させることによって、各温度域に合わせて液相率とＰ含有固相率とを制御する手法が適切である。   The slag liquid phase ratio is determined by the temperature and the composition of the slag, but the temperature is usually difficult to control for the convenience of processing. Therefore, a method of controlling the liquid phase rate and the P-containing solid phase rate in accordance with each temperature range by changing the slag composition during blowing is appropriate.

実際のスラグ組成の制御は、以下のようにして行う。   The actual control of the slag composition is performed as follows.

まず、ＣａＯ濃度は、石灰石、生石灰、ドロマイト、スラグなどのＣａＯ分を含有する副原料を複数回に分割して添加することにより、吹錬中に増加させることが出来る。この際、後から添加する石灰は迅速に滓化することが望ましく、粉体や低融点化合物の形で添加したほうが良い。   First, CaO density | concentration can be increased during blowing by adding the auxiliary material containing CaO content, such as limestone, quicklime, dolomite, and slag, divided | segmented into multiple times. At this time, it is desirable that lime added later is rapidly hatched, and it is better to add lime in the form of powder or a low melting point compound.

また、酸化鉄濃度の制御は、鉄鉱石の初期添加、初期ソフトブロー、初期弱攪拌とし、末期ハードブロー、強攪拌とすることによって行うことができる。   The iron oxide concentration can be controlled by initial addition of iron ore, initial soft blow, and initial weak stirring, and end hard blow and strong stirring.

ここで、酸化鉄濃度は、スラグ中のＦｅの２価と３価の酸化物の和を指し、全鉄濃度分析値から金属鉄濃度分析値を引いた値をＦｅＯ濃度に換算して管理する。   Here, the iron oxide concentration refers to the sum of the divalent and trivalent oxides of Fe in the slag, and is managed by converting the total iron concentration analysis value to the metal iron concentration analysis value into the FeO concentration. .

また、精錬処理用フラックスとして、ハロゲン化物を含まないものを用いることが好ましい。   Moreover, it is preferable to use a flux that does not contain a halide as the refining treatment flux.

上述の通り、精錬反応中に存在するスラグ中の固相を脱りんに利用するのが本発明の思想であり、ハロゲン化物を用いた場合、固相率が顕著に低下する恐れがあり、また耐火物など溶損の問題も起こり易い。ちなみに、ハロゲン化物としては、ＣａＦ２やＣａＣｌ２等が例示できる。 As described above, it is the idea of the present invention to use the solid phase in the slag present during the refining reaction for dephosphorization, and when a halide is used, the solid phase ratio may be significantly reduced, Problems with melting, such as refractories, are also likely to occur. Incidentally, examples of the halide include CaF 2 and CaCl 2 .

従って、ハロゲン化物を用いないことによって、スラグ中の固相の脱りんへの積極利用や、精錬コストの低下を達成できる。   Therefore, by not using a halide, it is possible to actively use the solid phase in the slag for dephosphorization and to reduce the refining cost.

実施例、比較例ともに、３００ｔ規模の上底吹き転炉を用いたものである。これらの例では、酸素は上吹きランスから供給し、底吹きは小径集合管羽口から処理の全般にわたってＣＯ２を供給した。 Both the examples and comparative examples use a 300 t scale top-bottom converter. In these examples, oxygen was supplied from the top blowing lance, and the bottom blowing supplied CO 2 from the small diameter collecting tube tuyere throughout the process.

溶銑の初期組成はＣ：４．４５〜４．６３質量％、Ｓｉ：０．２８〜０．３２質量％、Ｍｎ：０．２５〜０．２８質量％、Ｐ：０．０９〜０．１１質量％、Ｓ：０．０１４〜０．０１６質量％で、温度は１３３０〜１３５０℃であった。   The initial composition of the hot metal was C: 4.45 to 4.63 mass%, Si: 0.28 to 0.32 mass%, Mn: 0.25 to 0.28 mass%, P: 0.09 to 0.11. Mass%, S: 0.014 to 0.016 mass%, and temperature was 1330 to 1350 ° C.

実施例４から１１、比較例の４から１１では、この溶銑を予め脱珪処理した溶銑を用いた。このときの脱珪後溶銑組成は、Ｃ：４．１２〜４．２４質量％、Ｓｉ：０．１２〜０．１８質量％、Ｍｎ：０．２４〜０．２６質量％、Ｐ：０．０９〜０．１１質量％、Ｓ：０．０１４〜０．０１６質量％で、温度は１３５０〜１３８０℃であった。   In Examples 4 to 11 and Comparative Examples 4 to 11, hot metal obtained by desiliconizing this hot metal in advance was used. At this time, the hot metal composition after desiliconization was C: 4.12 to 4.24 mass%, Si: 0.12 to 0.18 mass%, Mn: 0.24 to 0.26 mass%, P: 0.00. 09-0.11 mass%, S: 0.014-0.016 mass%, The temperature was 1350-1380 degreeC.

実施例１２では、生石灰を分割添加した以外は実施例１と同様の処理を行った。この時、装入生石灰のうち７０質量％を初期に一括で添加した後、吹錬時間の５０％が経過した時点で残りの生石灰３０質量％、を装入した。表中の「実施例１２前半」は残りの生石灰装入直前にサンプリングした値である。   In Example 12, the same treatment as in Example 1 was performed except that quicklime was added in portions. At this time, 70 mass% of the charged quick lime was initially added in a lump, and then the remaining 30 mass% of quick lime was charged when 50% of the blowing time had elapsed. “First half of Example 12” in the table is a value sampled immediately before the rest of the quicklime charging.

酸素吹錬停止時を「精錬処理後」としてその時点の温度Ｔｅ、メタル組成、スラグ組成、精錬処理後の急冷スラグのＥＰＭＡ（電子線マイクロアナライザ）分析から求めたＰ含有固相率（％Ｐ＿Ｓｏｌｉｄ）を表１に示す。ただし、スラグ組成はＣａＯ−ＳｉＯ２−ＦｅＯの３元系に割り戻して示した。 P-containing solid phase ratio (% P_Solid) obtained from EPMA (electron beam microanalyzer) analysis of temperature Te, metal composition, slag composition, and quenching slag after refining treatment at the time when oxygen blowing was stopped as “after refining treatment” ) Is shown in Table 1. However, the slag composition is shown by reverting to a ternary system of CaO—SiO 2 —FeO.

実施例１〜１２では、各スラグ組成は各温度に対応する図１〜１１の斜線部にあり、また急冷スラグの鉱物相解析の結果、２ＣａＯ・ＳｉＯ２−３ＣａＯ・Ｐ２Ｏ５固溶体、ｎＣａＯ・Ｐ２Ｏ５固相（ここでｎは２，３，４のうち少なくとも一つ）のいずれか一方または双方が存在しており、かつ、この固相にＰが含まれていることを確認した。また、メタル中のＰを低減できており、良好な脱りんを実施できた。 In Examples 1-12, the slag composition is in the hatched portion in FIG. 1 to 11 corresponding to each temperature and the results of the mineral phase analysis of the quenched slag, 2CaO · SiO 2 -3CaO · P 2 O 5 solid solution, NCaO Confirm that one or both of P 2 O 5 solid phase (where n is at least one of 2, 3 and 4) or both are present, and that this solid phase contains P did. Moreover, P in the metal could be reduced and good dephosphorization could be carried out.

一方、比較例１〜１１では、各スラグ組成は各温度に対応する図１〜１１の斜線部からはずれており、また急冷スラグの鉱物相解析の結果、２ＣａＯ・ＳｉＯ２−３ＣａＯ・Ｐ２Ｏ５固溶体、ｎＣａＯ・Ｐ２Ｏ５固相（ここでｎは２，３，４のうち少なくとも一つ）のいずれも確認できなかった。また、メタル中のＰを充分に低減できておらず、充分な脱りんを実施できなかった。 On the other hand, in Comparative Examples 1-11, each slag composition has deviated from the shaded part of FIGS. 1-11 corresponding to each temperature, and as a result of the mineral phase analysis of the quenched slag, 2CaO · SiO 2 -3CaO · P 2 O Neither 5 solid solution nor nCaO · P 2 O 5 solid phase (wherein n is at least one of 2, 3 and 4) could not be confirmed. Further, P in the metal could not be sufficiently reduced, and sufficient dephosphorization could not be performed.

このように、本発明で提案したスラグ組成に制御することによって良好な脱りん処理を行うことが出来た。   Thus, the good dephosphorization process was able to be performed by controlling to the slag composition proposed by this invention.

Figure 2005226148
Figure 2005226148

処理後温度が１３２５℃未満の場合に、望ましい処理後のスラグ平均組成領域を示す図である。It is a figure which shows the slag average composition area | region after a preferable process when the temperature after a process is less than 1325 degreeC. 処理後温度が１３２５℃以上１３７５℃未満の場合に、望ましい処理後のスラグ平均組成領域を示す図である。It is a figure which shows the slag average composition area | region after a desirable process when the temperature after a process is 1325 degreeC or more and less than 1375 degreeC. 処理後温度が１３７５℃以上１４２５℃未満の場合に、望ましい処理後のスラグ平均組成領域を示す図である。It is a figure which shows the slag average composition area | region after a preferable process when the temperature after a process is 1375 degreeC or more and less than 1425 degreeC. 処理後温度が１４２５℃以上１４７５℃未満の場合に、望ましい処理後のスラグ平均組成領域を示す図である。It is a figure which shows the desirable slag average composition area | region after a process when the temperature after a process is 1425 degreeC or more and less than 1475 degreeC. 処理後温度が１４７５℃以上１５２５℃未満の場合に、望ましい処理後のスラグ平均組成領域を示す図である。It is a figure which shows the desirable slag average composition area | region after a process when the temperature after a process is 1475 degreeC or more and less than 1525 degreeC. 処理後温度が１５２５℃以上１５７５℃未満の場合に、望ましい処理後のスラグ平均組成領域を示す図である。It is a figure which shows the desirable slag average composition area | region after a process when the temperature after a process is 1525 degreeC or more and less than 1575 degreeC. 処理後温度が１５７５℃以上１６２５℃未満の場合に、望ましい処理後のスラグ平均組成領域を示す図である。It is a figure which shows the desirable slag average composition area | region after a process when the temperature after a process is 1575 degreeC or more and less than 1625 degreeC. 処理後温度が１６２５℃以上１６７５℃未満の場合に、望ましい処理後のスラグ平均組成領域を示す図である。It is a figure which shows the desirable slag average composition area | region after a process, when the temperature after a process is 1625 degreeC or more and less than 1675 degreeC. 処理後温度が１６７５℃以上１７２５℃未満の場合に、望ましい処理後のスラグ平均組成領域を示す図である。It is a figure which shows the desirable slag average composition area | region after a process, when the temperature after a process is 1675 degreeC or more and less than 1725 degreeC. 処理後温度が１７２５℃以上１７７５℃未満の場合に、望ましい処理後のスラグ平均組成領域を示す図である。It is a figure which shows the desirable slag average composition area | region after a process, when the temperature after a process is 1725 degreeC or more and less than 1775 degreeC. 処理後温度が１７７５℃以上の場合に、望ましい処理後のスラグ平均組成領域を示す図である。It is a figure which shows the desirable slag average composition area | region after a process when the temperature after a process is 1775 degreeC or more. 液相率および固相率の求め方を示す図である。It is a figure which shows how to obtain | require a liquid phase rate and a solid-phase rate.

Claims (16)

精錬処理後スラグの平均組成が、精錬処理後温度において、２ＣａＯ・ＳｉＯ２−３ＣａＯ・Ｐ２Ｏ５固溶体、ｎＣａＯ・Ｐ２Ｏ５固相（ここでｎは２，３，４のうち少なくとも一つ）のいずれか一方または双方が存在する領域となる様に調整する、精錬方法。 The average composition of the slag after refining treatment is 2CaO · SiO 2 -3CaO · P 2 O 5 solid solution, nCaO · P 2 O 5 solid phase (where n is at least one of 2, 3 and 4) at the temperature after refining treatment. The refining method is adjusted so that one or both of the two exist. 精錬処理後温度が１３２５℃未満の場合に、精錬処理後スラグの平均組成を、図１に示す斜線部の領域とする、請求項１に記載の精錬方法。   2. The refining method according to claim 1, wherein when the temperature after refining treatment is less than 1325 ° C., the average composition of the slag after refining treatment is set to the shaded area shown in FIG. 1. 精錬処理後温度が１３２５℃以上１３７５℃未満の場合に、精錬処理後スラグの平均組成を図２に示す斜線部の領域とする、請求項１に記載の精錬方法。   2. The refining method according to claim 1, wherein when the temperature after refining treatment is 1325 ° C. or higher and lower than 1375 ° C., the average composition of the slag after refining treatment is set to the shaded area shown in FIG. 2. 精錬処理後温度が１３７５℃以上１４２５℃未満の場合に、精錬処理後スラグの平均組成を図３に示す斜線部の領域とする、請求項１に記載の精錬方法。   The refining method according to claim 1, wherein when the temperature after refining treatment is 1375 ° C. or higher and lower than 1425 ° C., the average composition of the slag after refining treatment is set to the shaded area shown in FIG. 3. 精錬処理後温度が１４２５℃以上１４７５℃未満の場合に、精錬処理後スラグの平均組成を図４に示す斜線部の領域とする、請求項１に記載の精錬方法。   The refining method according to claim 1, wherein when the temperature after refining treatment is 1425 ° C. or higher and lower than 1475 ° C., the average composition of the slag after refining treatment is set to the shaded area shown in FIG. 4. 精錬処理後温度が１４７５℃以上１５２５℃未満の場合に、精錬処理後スラグの平均組成を図５に示す斜線部の領域とする、請求項１に記載の精錬方法。   The refining method according to claim 1, wherein when the temperature after refining treatment is 1475 ° C. or higher and lower than 1525 ° C., the average composition of the slag after refining treatment is set to the shaded area shown in FIG. 5. 精錬処理後温度が１５２５℃以上１５７５℃未満の場合に、精錬処理後スラグの平均組成を図６に示す斜線部の領域とする、請求項１に記載の精錬方法。   The refining method according to claim 1, wherein when the temperature after refining treatment is 1525 ° C. or higher and lower than 1575 ° C., the average composition of the slag after refining treatment is set to the shaded area shown in FIG. 6. 精錬処理後温度が１５７５℃以上１６２５℃未満の場合に、精錬処理後スラグの平均組成を図７に示す斜線部の領域とする、請求項１に記載の精錬方法。   The refining method according to claim 1, wherein when the temperature after refining treatment is 1575 ° C. or higher and lower than 1625 ° C., the average composition of the slag after refining treatment is set to the shaded area shown in FIG. 7. 精錬処理後温度が１６２５℃以上１６７５℃未満の場合に、精錬処理後スラグの平均組成を図８に示す斜線部の領域とする、請求項１に記載の精錬方法。   The refining method according to claim 1, wherein when the temperature after refining treatment is 1625 ° C. or higher and lower than 1675 ° C., the average composition of the slag after refining treatment is set to the shaded area shown in FIG. 8. 精錬処理後温度が１６７５℃以上１７２５℃未満の場合に、精錬処理後スラグの平均組成を図９に示す斜線部の領域とする、請求項１に記載の精錬方法。   The refining method according to claim 1, wherein when the temperature after refining treatment is 1675 ° C. or higher and lower than 1725 ° C., the average composition of the slag after refining treatment is set to the shaded area shown in FIG. 9. 精錬処理後温度が１７２５℃以上１７７５℃未満の場合に、精錬処理後スラグの平均組成を図１０に示す斜線部の領域とする、請求項１に記載の精錬方法。   The refining method according to claim 1, wherein when the temperature after refining treatment is not less than 1725 ° C. and less than 1775 ° C., the average composition of the slag after refining treatment is set to the shaded area shown in FIG. 10. 精錬処理後温度が１７７５℃以上の場合に、精錬処理後のスラグ平均組成を図１１に示す斜線部の領域とする、請求項１に記載の精錬方法。   The refining method according to claim 1, wherein when the temperature after the refining treatment is 1775 ° C. or higher, the slag average composition after the refining treatment is set to the shaded area shown in FIG. 11. 精錬処理後スラグにおける、２ＣａＯ・ＳｉＯ２−３ＣａＯ・Ｐ２Ｏ５固溶体、ｎＣａＯ・Ｐ２Ｏ５固相（ここでｎは２，３，４のうち少なくとも一つ）のいずれか一方または双方を、精錬処理後スラグ全体の５〜８０質量％とする、請求項１〜１２のいずれか１項に記載の精錬方法。 One or both of 2CaO · SiO 2 -3CaO · P 2 O 5 solid solution and nCaO · P 2 O 5 solid phase (where n is at least one of 2, 3, 4) in the slag after refining treatment The refining method according to any one of claims 1 to 12, wherein the total amount of slag after refining is 5 to 80% by mass. 精錬処理後スラグにおける、２ＣａＯ・ＳｉＯ２−３ＣａＯ・Ｐ２Ｏ５固溶体、ｎＣａＯ・Ｐ２Ｏ５固相（ここでｎは２，３，４のうち少なくとも一つ）のいずれか一方または双方の固相中のＰ濃度を、それ以外の相の平均Ｐ濃度よりも高くする、請求項１〜１３のいずれか１項に記載の精錬方法。 One or both of 2CaO · SiO 2 -3CaO · P 2 O 5 solid solution and nCaO · P 2 O 5 solid phase (where n is at least one of 2, 3, 4) in the slag after refining treatment The refining method according to any one of claims 1 to 13, wherein the P concentration in the solid phase is higher than the average P concentration in the other phases. 精錬処理時間のうち精錬処理開始時から５０％〜８０％が経過する期間内の任意の時期のスラグの平均組成を、図１〜図１１をそれぞれ用いて求まる液相率９０％以上の組成領域とする、請求項２〜１４のいずれか１項に記載の精錬方法。   Composition range of 90% or more of liquid phase ratio obtained by using FIG. 1 to FIG. 11 for the average composition of slag at any time within a period of 50% to 80% from the start of the refining process. The refining method according to any one of claims 2 to 14. 精錬処理用フラックスとして、ハロゲン化物を含まないものを用いる、請求項１〜１５のいずれか１項に記載の精錬方法。   The refining method according to any one of claims 1 to 15, wherein a flux not containing a halide is used as a refining treatment flux.
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JPH09143529A (en) * 1995-11-29 1997-06-03 Nippon Steel Corp Method for dephosphorizing molten iron
JP2001026807A (en) * 1999-07-14 2001-01-30 Nippon Steel Corp Method for dephosphorizing molten iron
JP2002212620A (en) * 2001-01-11 2002-07-31 Nippon Steel Corp Method for dephosphorizing molten iron

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH09143529A (en) * 1995-11-29 1997-06-03 Nippon Steel Corp Method for dephosphorizing molten iron
JP2001026807A (en) * 1999-07-14 2001-01-30 Nippon Steel Corp Method for dephosphorizing molten iron
JP2002212620A (en) * 2001-01-11 2002-07-31 Nippon Steel Corp Method for dephosphorizing molten iron

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