JP3317258B2 - Mold powder for continuous casting of high Mn round section slabs - Google Patents
Mold powder for continuous casting of high Mn round section slabsInfo
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- JP3317258B2 JP3317258B2 JP35130598A JP35130598A JP3317258B2 JP 3317258 B2 JP3317258 B2 JP 3317258B2 JP 35130598 A JP35130598 A JP 35130598A JP 35130598 A JP35130598 A JP 35130598A JP 3317258 B2 JP3317258 B2 JP 3317258B2
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Description
【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION
【0001】[0001]
【発明の属する技術分野】本発明は、丸断面鋳片の連続
鋳造に際し、特に表皮直下に発生する気泡性欠陥の少な
い高品質な鋳片を得ることを可能とする高Mn丸断面鋳片
の連続鋳造用モールドパウダとそれを使用した連続鋳造
方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-Mn round-section slab which is capable of obtaining a high-quality slab having few bubble defects generated immediately below the skin in continuous casting of a round-section slab. The present invention relates to a continuous casting mold powder and a continuous casting method using the same.
【0002】[0002]
【従来の技術】鋼の連続鋳造においては、浸漬ノズルか
らモールド内へ注入された溶鋼表面にモールドパウダを
添加する。通常、このモールドパウダは、複数種類の酸
化物や炭素材等の粉末を混合、あるいは混合後、顆粒状
に成形したものが使用される。2. Description of the Related Art In continuous casting of steel, mold powder is added to the surface of molten steel poured into a mold from an immersion nozzle. Usually, as the mold powder, a powder obtained by mixing a plurality of kinds of powders of oxides, carbon materials, or the like, or after mixing, is formed into granules.
【0003】鋳型内に投入されたモールドパウダは、以
下に挙げる役割を担う。 (1) 溶鋼の保温および酸化防止、 (2) 溶鋼中の気泡および介在物の吸収、 (3) 鋳型内壁と凝固殻との潤滑性の確保、 (4) 鋳型内壁と凝固殻との間隙の熱伝導度の調整。[0003] The mold powder put into the mold plays the following roles. (1) Insulation of molten steel and prevention of oxidation, (2) Absorption of bubbles and inclusions in molten steel, (3) Ensuring lubricity between mold inner wall and solidified shell, (4) Clearance of gap between mold inner wall and solidified shell Adjustment of thermal conductivity.
【0004】このような役割の達成のため、鋳造条件に
応じてモールドパウダの組成が検討され、溶融・滓化速
度、溶融時の粘度および凝固温度、そして凝固後の結晶
化率等の特性が調整される。[0004] In order to achieve such a role, the composition of the mold powder is examined according to the casting conditions, and characteristics such as melting / slagging speed, viscosity and solidification temperature during melting, and crystallization ratio after solidification are determined. Adjusted.
【0005】丸断面鋳片の連続鋳造の場合には、凝固シ
ェルが円環状であるがゆえにバルジング (溶鋼静圧によ
る膨張) が少ないから、断面矩形鋳片の場合と比較し
て、凝固シェルのモールド壁への密着性が劣る。ゆえ
に、モールド壁と凝固シェルとの間隙に流入した溶融パ
ウダが過度に結晶化した場合には、パウダフィルム中の
ガラス質が不足し、モールド壁と凝固シェル間隙への充
填性が失われるのでモールド壁と凝固シェルとの間に多
くの空隙を生じる。上記の理由により丸断面鋳片の連続
鋳造に供されるパウダは、溶融してモールド・シェル間
隙に流入した後、凝固するに際し結晶化の度合いが過度
であってはならない。結晶化が過度であるとモールド・
シェル間に多くの空隙が生じ、その空隙生成部位のモー
ルド冷却能が局部的に著しく低下するため、鋳片の凝固
が不均一となり縦割れ等の表面欠陥が発生するからであ
る。In the case of continuous casting of a slab having a round cross section, bulging (expansion due to static pressure of molten steel) is small because the solidified shell is annular, so that the solidified shell has a smaller shape than a slab having a rectangular cross section. Poor adhesion to mold wall. Therefore, when the molten powder flowing into the gap between the mold wall and the solidified shell is excessively crystallized, the glass quality in the powder film becomes insufficient, and the filling property between the mold wall and the solidified shell gap is lost. Many voids are created between the wall and the solidified shell. For the above reasons, the powder used for continuous casting of round section slabs must not be excessively crystallized when solidifying after melting and flowing into the mold-shell gap. If the crystallization is excessive, the mold
This is because many voids are generated between the shells, and the mold cooling ability at the void generating portion is significantly reduced locally, so that the solidification of the slab becomes uneven and surface defects such as vertical cracks occur.
【0006】これらの事情により、従来、例えばCAMP I
SIJ VOL.8(1995)-1013や特開平7−214263号公報、特開
平8−25008 号公報に示されているように、丸断面鋳片
の連続鋳造には、CaO*とSiO2との重量比CaO*/SiO2(以
下、塩基度) を0.9 以下に制限することによって、溶融
パウダの凝固時の結晶化を抑制する化学組成のモールド
パウダが適用されてきた。なお、上記のCaO*は総CaのCa
O 換算重量である。Under these circumstances, conventionally, for example, CAMP I
SIJ VOL.8 (1995) -1013 and Japanese Patent 7-214263 discloses, as shown in JP-A-8-25008, the continuous casting of round cross-section billet, the CaO * and SiO 2 Mold powder having a chemical composition that suppresses crystallization during solidification of molten powder by limiting the weight ratio CaO * / SiO 2 (hereinafter, basicity) to 0.9 or less has been applied. Note that the above CaO * is the total Ca
O-converted weight.
【0007】[0007]
【発明が解決しようとする課題】しかしながら、鋼中Mn
濃度が0.8 mass%以上の鋼 (以下、高Mn鋼) を鋳造する
場合、塩基度を0.9 以下に制限したモールドパウダを適
用すると、溶融パウダ中のSiO2が鋼中Mnを酸化する反応
[下記(1) 式] が進行し、MnO が生成してパウダ溶融層
中に富化することが、本発明者らの研究により明らかと
なった。However, Mn in steel
When casting a steel with a concentration of 0.8 mass% or more (hereinafter referred to as high Mn steel), if mold powder with a basicity of 0.9 or less is applied, SiO 2 in the molten powder oxidizes Mn in the steel.
The study of the present inventors has clarified that the following [Formula (1)] progresses, and MnO 2 is generated and enriched in the powder molten layer.
【0008】 1/2SiO2 + Mn → MnO + 1/2Si ・・・ (1) 初期SiO2濃度、Mn濃度が高く、MnO 濃度、Si濃度が低い
場合には、(1) 式の反応は、ある平衡状態に達するまで
進行するのである。1 / 2SiO 2 + Mn → MnO + 1 / 2Si (1) When the initial SiO 2 concentration and the Mn concentration are high and the MnO concentration and the Si concentration are low, the reaction of the equation (1) is as follows. It proceeds until a certain equilibrium state is reached.
【0009】図1は、鋼中Mn濃度 ([%Mn])とパウダ溶融
層中に富化したMnO の濃度(%MnO)および使用前パウダが
溶融パウダとなる間に生じた塩基度変化 [Δ(CaO/Si
O2)] との関係を示すグラフである。FIG. 1 shows the Mn concentration in steel ([% Mn]), the concentration of MnO enriched in the powder molten layer (% MnO), and the change in basicity that occurred before the powder before use became molten powder. Δ (CaO / Si
O 2 )].
【0010】ここで、パウダ溶融層 (溶融パウダ) の化
学組成は、モールド・凝固シェルの間隙に流入した溶融
パウダが薄いフィルムとなりモールド出口より排出され
たものを回収・分析して求めた。Here, the chemical composition of the powder melted layer (melted powder) was determined by collecting and analyzing a thin film in which the molten powder flowing into the gap between the mold and the solidified shell became a thin film and was discharged from the mold outlet.
【0011】この調査に際し、鋼成分としてC:0.2 ma
ss%、Mn:1.4 mass%の溶鋼を採用し、そのとき使用し
たパウダは、後述する表1の比較例Gのそれであった。
図1より高Mn鋼の鋳造時には塩基度が上昇 (SiO2が減
少) しMnO が濃化することから、前述の(1) 式に示した
反応が進行していることがわかる。In this investigation, C: 0.2 ma was used as the steel component.
The molten steel used was ss% and Mn: 1.4 mass%, and the powder used at that time was that of Comparative Example G in Table 1 described later.
From FIG. 1, the basicity increases (SiO 2 decreases) and MnO is concentrated during casting of a high Mn steel, indicating that the reaction shown in the above equation (1) is proceeding.
【0012】さらにルツボを用いた実験室での実験によ
り、溶融前のパウダ中SiO2濃度と、パウダの溶融後に溶
融パウダ層中に富化するMnO 濃度との関係を調査した結
果を図2に示す。Further, FIG. 2 shows the results of an investigation in a laboratory using a crucible to investigate the relationship between the SiO 2 concentration in the powder before melting and the MnO concentration enriched in the molten powder layer after the melting of the powder. Show.
【0013】図2より、低SiO2濃度のパウダを用いる
と、パウダが溶融したスラグ中にはMnO はほとんど富化
しないことが確認された。この結果もまた、パウダ中Si
O2が前述の(1) 式の反応を介してMnO を生じさせること
を裏付けている。From FIG. 2, it was confirmed that when powder having a low SiO 2 concentration was used, MnO was hardly enriched in the slag in which the powder was melted. This result also shows that
This supports that O 2 generates MnO 2 through the reaction of the above-mentioned formula (1).
【0014】このように、SiO2の多い、つまり塩基度の
低いモールドパウダはMnO を生じさせる。こうして生じ
たMnO はパウダ中に滓化抑制剤として配合されるカーボ
ンと反応し、下掲の(2) 式の反応によりCOガスを生じる
と考えられている。As described above, mold powder containing a large amount of SiO 2 , that is, having a low basicity generates MnO. It is believed that the MnO thus generated reacts with the carbon compounded as a slagging inhibitor in the powder, and generates CO gas by the reaction of the following formula (2).
【0015】 MnO(溶融ハ゜ウタ゛)+C(粉ハ゜ウタ゛)→ Mn(溶鋼)+CO(カ゛ス) ・・・ (2) 特にパウダ溶融層の厚さが薄く、かつ、モールド内湯面
が大きく変動した場合には、カーボンを含む未滓化パウ
ダと、MnO が富化した溶融パウダとが溶鋼と反応し、上
記(2) 式の反応によりCOガスが生じ、これが凝固シェル
に取込まれ気泡性欠陥となり易い。MnO (Molten Powder) + C (Powder Powder) → Mn (Molten Steel) + CO (Case) (2) Especially when the thickness of the powder molten layer is thin and the level of the molten metal in the mold changes greatly The unslagified powder containing carbon and the molten powder enriched in MnO react with the molten steel, and a CO gas is generated by the reaction of the above formula (2), which is taken into the solidified shell and easily becomes a cellular defect.
【0016】連続鋳造機においては、モールド内溶鋼を
電磁攪拌 (以下、EMS)によって回転させることにより、
結晶の核を発生させ等軸晶を増やし、鋳片中心部のポロ
シティ (引け巣) や成分偏析を軽減することが広く行わ
れる。ところが、丸断面モールド内において、EMS によ
る回転流を与えると、図3に模式的に示すように遠心力
によりモールド壁近傍の溶鋼が盛り上がるので、この部
位のパウダ溶融層が薄くなり、ゆえに、前述の気泡性欠
陥の発生率が高くなる。これは前述の(2) 式により溶鋼
へのMnの移行が行われることに相当する。In a continuous casting machine, the molten steel in a mold is rotated by electromagnetic stirring (hereinafter, referred to as EMS).
It is widely practiced to increase the number of equiaxed crystals by generating crystal nuclei to reduce porosity (shrinkage cavities) and component segregation in the center of the slab. However, when a rotating flow is given by EMS in a round cross-section mold, the molten steel near the mold wall rises due to centrifugal force as schematically shown in FIG. 3, so that the powder molten layer at this portion becomes thinner. Increases the rate of occurrence of cellular defects. This corresponds to the transfer of Mn to the molten steel according to the above equation (2).
【0017】図中、モールド10内に浸漬ノズル12から注
入される溶鋼14に矢印で示すEMS による回転流が生じ、
モールド壁近傍の溶鋼表面が盛り上がっているのが分か
る。その結果、パウダ層16の下部に形成されるパウダの
溶融層18はモールド近傍において薄層化し、未滓化パウ
ダと溶融パウダとさらに溶鋼との間の上記(2) 式の反応
を促進し、気泡性欠陥を増加させる結果となる。In the figure, the molten steel 14 injected from the immersion nozzle 12 into the mold 10 generates a rotating flow by EMS indicated by an arrow,
It can be seen that the surface of the molten steel near the mold wall is raised. As a result, the molten layer 18 of the powder formed below the powder layer 16 is thinned in the vicinity of the mold, and promotes the reaction of the formula (2) between the unslagged powder, the molten powder, and the molten steel, This results in increased cellular defects.
【0018】実際、この気泡性欠陥は図4に示すよう
に、当然のことながら高Mn鋼において発生が顕著であ
る。図4は、溶鋼中のMn濃度と指数で示す気泡性欠陥の
生成傾向とをグラフで示すもので、気泡性欠陥の発生
は、溶鋼のMn濃度に比例していることが分かる。In fact, as shown in FIG. 4, the occurrence of the cellular defect is remarkable in a high Mn steel as a matter of course. FIG. 4 is a graph showing the Mn concentration in the molten steel and the tendency to generate cellular defects indicated by an index. It can be seen that the generation of the cellular defects is proportional to the Mn concentration in the molten steel.
【0019】本発明の課題は、このように、特に丸断面
モールドの連続鋳造機において、モールド内溶鋼を回転
させつつ高Mn鋼を鋳造する場合に、発生し易い気泡性欠
陥を防止することのできるモールドパウダを提供するこ
とである。SUMMARY OF THE INVENTION It is an object of the present invention to prevent a bubble defect that easily occurs when a high Mn steel is cast while rotating molten steel in a mold, particularly in a continuous casting machine having a round section mold. To provide a mold powder that can be used.
【0020】[0020]
【課題を解決するための手段】かかる課題の解決に当た
って、前述の(1) 式および(2) 式の反応を介して発生す
る気泡性欠陥を防止するためには、(1) 式の反応の進行
を抑制する意図をもってモールドパウダ中のSiO2濃度を
低減することが有効であることは容易に推察される。Means for Solving the Problems In order to solve the above problems, in order to prevent bubble defects generated through the reactions of the above-mentioned equations (1) and (2), the reaction of the equation (1) It is easily presumed that it is effective to reduce the SiO 2 concentration in the mold powder with the intention of suppressing the progress.
【0021】このような、SiO2濃度の低減に関しては、
従来、特開昭57−184563号公報に示されるように、アル
ミキルド鋼を鋳造する場合に、溶鋼中のAlの酸化抑制等
を目的に Al2O3−CaO を主体としSiO2濃度を7.0 重量%
以下に低下させたモールドパウダが提案されている。ま
た、特開昭60−133956号公報には、Al2O3 、CaO および
MgO を基材としSiO2を含有しないモールドパウダが提示
されている。With respect to such reduction of the SiO 2 concentration,
Conventionally, as shown in JP-A-57-184563, in the case of casting aluminum-killed steel, 7.0 weight SiO 2 concentration mainly of Al 2 O 3 -CaO the purpose of suppressing oxidation and the like of Al in the molten steel %
The following reduced mold powder has been proposed. Further, Japanese Patent Application Laid-Open No. Sho 60-133396 discloses that Al 2 O 3 , CaO and
A mold powder based on MgO and containing no SiO 2 has been proposed.
【0022】本発明者らは、当初、(1) 式に示される反
応を抑制し、気泡性欠陥を防止するためには、徹底した
SiO2濃度の低減が必要と考え、特開昭57−184563号公報
あるいは特開昭60−133956号公報に開示されたものと同
様のモールドパウダを試作し実験に供しようとした。し
かしながら、これらの低SiO2のパウダは溶融したスラグ
の粘度・凝固温度あるいは凝固後の結晶化率という特性
を丸断面鋳片の連続鋳造に適するように調整することが
非常に困難であり、本発明者らが試作した数10銘柄の範
囲では、実際に鋳造に供することができるパウダを得る
ことは不可能であった。At first, the present inventors have taken thorough measures to suppress the reaction represented by the formula (1) and prevent bubble defects.
Since it was considered necessary to reduce the SiO 2 concentration, a mold powder similar to the one disclosed in JP-A-57-184563 or JP-A-60-133956 was trial-produced and tried to be used for experiments. However, it is very difficult for these low SiO 2 powders to adjust the characteristics such as the viscosity and solidification temperature of the molten slag or the crystallization rate after solidification so as to be suitable for continuous casting of round-section slabs. In the range of several tens of brands prototyped by the inventors, it was impossible to obtain powder that could be actually used for casting.
【0023】ここで丸断面鋳片の連続鋳造に適したパウ
ダの特性とは、溶融したスラグの1300℃における粘度
は、特開平8−25008 号公報に開示されているように、
0.3 〜0.7 Pa・s 、凝固温度は、CAMP-ISIJ VoL.8(199
5)-1013に開示されているように、例えば炭素濃度が0.2
から0.5 mass%の炭素鋼を鋳込む場合においては、105
0〜1150℃程度、さらに結晶化の度合は前述の如く過度
でないことが求められる。Here, the characteristics of powder suitable for continuous casting of a round section slab are as follows. The viscosity of molten slag at 1300 ° C. is as disclosed in Japanese Patent Application Laid-Open No. 8-25008.
0.3 to 0.7 Pas, solidification temperature is CAMP-ISIJ VoL.8 (199
5) As disclosed in -1013, for example, when the carbon concentration is 0.2
When casting 0.5 mass% of carbon steel from
About 0 to 1150 ° C., and the degree of crystallization is required not to be excessive as described above.
【0024】このように、徹底したSiO2濃度の低減は実
現が困難であったことに鑑み、本発明者らは種々検討を
重ねた末、SiO2濃度を徹底して低減しなくとも、SiO2の
活量を1/2 程度にまで低下させることができれば、前述
の気泡性欠陥は、実用上問題のないレベルにまで低減で
きることに思い至った。In view of the fact that it has been difficult to achieve a thorough reduction of the SiO 2 concentration in this way, the present inventors have made various studies and found that even if the SiO 2 concentration was not thoroughly reduced, the SiO 2 concentration could not be reduced. It was thought that if the activity of No. 2 could be reduced to about 1/2, the above-mentioned bubble-like defect could be reduced to a level having no practical problem.
【0025】例えば、図1において、鋼中Mn濃度が0.6
%程度の鋼を鋳造する際には2%程度MnO が溶融パウダ
中に富化しているにもかかわらず、図4に示すように、
鋼中Mn濃度が0.6 %程度であれば実用上気泡性欠陥発生
率は問題のない程度である。For example, in FIG. 1, the Mn concentration in steel is 0.6
When casting about 2% steel, although about 2% MnO is enriched in the molten powder, as shown in FIG.
If the Mn concentration in the steel is about 0.6%, the occurrence rate of bubble defects is practically negligible.
【0026】(1) 式において左辺から右辺への反応を抑
制するという観点からは、鋼中Mn濃度 (厳密にはMn活
量) 低下とパウダ中SiO2活量低下とは等価であるので、
SiO2活量を例えば1/2 に低下させることができれば、Mn
O 生成量を問題のない程度にまで抑制できる可能性があ
る。ここで、活量とは、モル濃度に活量係数を乗じたも
のであり、化学反応活性を示す指標である。From the viewpoint of suppressing the reaction from the left side to the right side in equation (1), a decrease in the Mn concentration in steel (strictly speaking, the Mn activity) is equivalent to a decrease in the SiO 2 activity in the powder.
If the activity of SiO 2 can be reduced to half, for example, Mn
There is a possibility that the amount of O generated can be suppressed to a level that does not cause any problem. Here, the activity is obtained by multiplying the molar concentration by the activity coefficient and is an index indicating the chemical reaction activity.
【0027】本発明者らは、モールドパウダの主成分で
あるCaO-SiO2-Al2O3 3元系におけるSiO2の活量に着目し
たところ、塩基度が0.9 を超えると、塩基度上昇に対し
SiO2活量が急激に低下することを見出した。さらに、従
来の丸断面連続鋳造用パウダは塩基度が0.9 を超えると
凝固時の結晶化が過度となり鋳造に支障を来たしていた
のに対し、Al2O3 濃度を高めたパウダの場合は両性酸化
物であるAl2O3 が酸性酸化物として作用し結晶化を抑制
することを発見し、本発明を完成した。[0027] The present inventors have focused on the activity of SiO 2 in the CaO-SiO 2 -Al 2 O 3 3 -way system, which is a main component of mold powder, when the basicity exceeds 0.9, the basicity increases Against
It has been found that the SiO 2 activity decreases rapidly. In addition, conventional round-section continuous casting powders, when the basicity exceeds 0.9, excessively crystallize during solidification and hinder casting.On the other hand, in the case of powders with increased Al 2 O 3 concentration, The present inventors have discovered that Al 2 O 3 as an oxide acts as an acidic oxide and suppresses crystallization, and thus completed the present invention.
【0028】ここに、本発明は、次の通りである。 (1) Mn:0.8 mass%以上含有する高Mn丸断面鋳片の連続
鋳造用モールドパウダであって、CaO*を総CaのCaO 換算
重量とすると、 CaO*とSiO2の重量比、CaO*/SiO2 =0.95〜1.40 Al2O3 濃度 Al2O3 =10〜30mass% Na2O 濃度 Na2O≦4mass% を満足する化学組成を有することを特徴とするモールド
パウダ。Here, the present invention is as follows. (1) Mn: A mold powder for continuous casting of high-Mn round section slabs containing 0.8 mass% or more, where CaO * is the weight of total Ca in terms of CaO, and the weight ratio of CaO * to SiO 2 , CaO * Mold powder characterized by having a chemical composition satisfying: / SiO 2 = 0.95 to 1.40 Al 2 O 3 concentration Al 2 O 3 = 10 to 30 mass% Na 2 O concentration Na 2 O ≦ 4 mass%
【0029】(2) 鋳型内電磁攪拌を行いながらMn:0.8
mass%以上含有する高Mn丸断面鋳片を連続鋳造する際
に、モールド内の溶鋼表面に、上記(1) 記載のモールド
パウダを投入することを特徴とする高Mn丸断面鋳片の連
続鋳造方法。(2) Mn: 0.8 while performing electromagnetic stirring in the mold
The continuous casting of a high Mn round section slab is characterized in that, when continuously casting a high Mn round section slab containing at least mass%, the mold powder described in (1) above is poured into the molten steel surface in the mold. Method.
【0030】[0030]
【発明の実施の形態】本発明において上述のようにパウ
ダの化学組成を限定した理由について説明する。本発明
にかかるパウダは、主成分であるCaO およびSiO2がCaO*
/SiO2 の比 (塩基度) が0.95〜1.40を満足する限り、特
にそれぞれの配合量は制限されない。なお、CaO*はパウ
ダに配合されるCa分をすべてCaO に換算したものであ
る。DESCRIPTION OF THE PREFERRED EMBODIMENTS The reasons for limiting the chemical composition of powder in the present invention as described above will be described. In the powder according to the present invention, the main components CaO and SiO 2 are CaO *
As long as the / SiO 2 ratio (basicity) satisfies 0.95 to 1.40, the amount of each component is not particularly limited. In addition, CaO * is the value obtained by converting all the Ca content in the powder into CaO.
【0031】従来、塩基度が0.9 を超えると溶融パウダ
が凝固する際の結晶化が過度となり、丸鋳片の連続鋳造
には不適合であることがわかっていたが、両性酸化物で
あるAl2O3 はこの程度の組成領域であれば酸性酸化物と
して作用するので、Al2O3 が10mass%以上含有されれば
塩基度が0.9 を超えても、過度の結晶化による弊害は生
じないことが明らかとなった。本発明においては塩基度
が0.95以上で実際上の効果が表われるので下限を0.95と
した。[0031] Conventional, Al 2 basicity becomes excessive crystallization at the time of solidification and melting powder exceeds 0.9, although the continuous casting of round billet was found to be incompatible, amphoteric oxide Since O 3 acts as an acidic oxide in this composition range, even if the basicity exceeds 0.9 if Al 2 O 3 is contained at 10 mass% or more, no adverse effect due to excessive crystallization occurs. Became clear. In the present invention, the lower limit is set to 0.95 because a practical effect is exhibited when the basicity is 0.95 or more.
【0032】一方、塩基度 (CaO*/SiO2)は1.40を超える
とAl2O3 濃度を30mass%を越えて増しても、結晶化の抑
制が困難となる。ここにAl2O3 濃度は、30mass%を超え
ると図5に示すように溶融パウダーの粘度が上昇する。
粘度はFの添加量を増すと低下するが、F添加量の増大
は鋳型内における浸漬ノズル溶損増大等の弊害を生じる
ことから、Al2O3 濃度は最大30mass%に制限した。好ま
しくはAl2O3 濃度は10〜20%である。On the other hand, if the basicity (CaO * / SiO 2 ) exceeds 1.40, it becomes difficult to suppress crystallization even if the Al 2 O 3 concentration is increased beyond 30 mass%. Here, when the Al 2 O 3 concentration exceeds 30 mass%, the viscosity of the molten powder increases as shown in FIG.
Although the viscosity decreases as the added amount of F increases, an increase in the added amount of F causes adverse effects such as an increase in the erosion of the immersion nozzle in the mold. Therefore, the Al 2 O 3 concentration is limited to a maximum of 30 mass%. Preferably the concentration of Al 2 O 3 is 10-20%.
【0033】また、図6に示すように塩基度が高くなる
と凝固温度が高くなるので、適正な凝固温度に保つため
にはF添加量を増す必要が生じる。一方で、F添加量の
増大は鋳型内浸漬ノズルの溶損を増す等の弊害を生じ
る。なお、Fは蛍石などとして配合され、凝固温度およ
び粘度降下剤であり、通常3〜10mass%配合してもよ
い。As shown in FIG. 6, when the basicity increases, the coagulation temperature increases. Therefore, in order to maintain an appropriate coagulation temperature, it is necessary to increase the amount of F added. On the other hand, an increase in the amount of added F causes adverse effects such as an increase in the melting damage of the immersion nozzle in the mold. In addition, F is compounded as fluorite or the like, and is a coagulation temperature and a viscosity lowering agent, and may be usually compounded at 3 to 10% by mass.
【0034】これらの事情により塩基度 (CaO*/SiO2)の
上限は、1.40とした。Na2OはSiO2と反応し約800 ℃の比
較的低温にて液相を生成するので、これがバインダとな
り図7に示されるようなスラグリム82と呼ばれる焼結体
の生成原因となる。図中、未滓化パウダ80は、Na2Oが含
まれていると、焼結体を内部に形成する。この焼結体が
スラグリム82である。スラグリムは、パウダ供給や鋳型
内確認等作業の障害となるので、生成しないことが望ま
しく、この観点よりNa2O濃度は4mass%以下に制限し
た。Under these circumstances, the upper limit of the basicity (CaO * / SiO 2 ) was set to 1.40. Since Na 2 O reacts with SiO 2 and generates a liquid phase at a relatively low temperature of about 800 ° C., it becomes a binder and causes the formation of a sintered body called a slag rim 82 as shown in FIG. In the drawing, the unslag-free powder 80 forms a sintered body when Na 2 O is contained. This sintered body is the slag rim 82. Since slag rims hinder operations such as powder supply and confirmation in a mold, it is desirable not to produce slag rims. From this viewpoint, the Na 2 O concentration was limited to 4 mass% or less.
【0035】図8に示されるようにNa2O濃度が、4mass
%以下であれば、スラグリムの成長は小さく操業上の問
題は生じない。なお、K2O 、Li2Oなどの他のアルカリ金
属酸化物も同様の作用を有することからそれらが配合さ
れるときは低濃度であることが望ましい。As shown in FIG. 8, the Na 2 O concentration was 4 mass
% Or less, the growth of the slag rim is small and no operational problems occur. Since other alkali metal oxides such as K 2 O and Li 2 O also have the same action, when they are blended, it is desirable that they have a low concentration.
【0036】本発明にかかるパウダは、必要により、凝
固温度、粘度の調整のため、あるいはAl2O3 原料等の不
純分としてMgO を、また滓化速度調整のためにCを含有
してもよいが、その他、炭酸塩等の通常のパウダが含有
するものであれば、それらを含有することに何等の制限
はない。The powder according to the present invention may contain MgO for adjusting the coagulation temperature and viscosity, or as an impurity such as Al 2 O 3 raw material, and C for adjusting the slagging rate, if necessary. It is good, but there is no particular limitation on the inclusion thereof as long as it is contained in ordinary powders such as carbonates.
【0037】本発明の好適態様によれば、本発明にかか
るパウダは、一般的には、次の組成を有する。 CaO*/SiO2 : 0.95〜1.40、 Al2O3 : 10〜30mass%、 Na2O : 0 〜 4 mass %、 F 分 : 3 〜 10mass %、 MgO : 0 〜 5 mass %、 C分 : 2 〜 7 mass %。According to a preferred embodiment of the present invention, the powder according to the present invention generally has the following composition. CaO * / SiO 2: 0.95~1.40, Al 2 O 3: 10~30mass%, Na 2 O: 0 ~ 4 mass%, F min: 3 ~ 10mass%, MgO: 0 ~ 5 mass%, C content: 2 ~ 7 mass%.
【0038】ただし、CaO*は総Ca量のCaO 換算値であ
り、F 分は、蛍石などとして配合する原料のF 分だけ、
そしてC分はコークス粉やカーボンブラック等の添加カ
ーボンおよび炭酸塩として配合される原料の炭素分だけ
を考慮したものである。次に、実施例によって本発明の
作用効果についてさらに具体的に説明する。However, CaO * is a CaO converted value of the total Ca amount, and the F component is the F component of the raw material to be blended as fluorite or the like.
The C content takes into account only the added carbon such as coke powder and carbon black and the carbon content of the raw material blended as the carbonate. Next, the working effects of the present invention will be described more specifically with reference to examples.
【0039】[0039]
【実施例】表1に本発明の実施例および比較例を示す。
なお、鋳片サイズは直径225 mm、鋳込速度は2.0 m/分、
EMS は平面回転流で実施した。Examples Table 1 shows examples of the present invention and comparative examples.
The slab size was 225 mm in diameter, the casting speed was 2.0 m / min,
EMS was performed with a plane rotating flow.
【0040】[0040]
【表1】 [Table 1]
【0041】実施例A〜Fは本発明によるパウダ組成の
例である。本発明においては、SiO2活量を低減し鋼中の
合金成分であるMnの酸化を抑制することが目的であるか
ら、SiO2よりもさらに低級な酸化物であるFe2O3 等は当
然のことながら添加されることはなく、2mass%以下の
低濃度に抑えることが好ましい。Examples AF are examples of powder compositions according to the present invention. In the present invention, since the purpose is to reduce the activity of SiO 2 and suppress the oxidation of Mn, which is an alloy component in steel, Fe 2 O 3 and the like, which are oxides lower than SiO 2 , are naturally used. However, it is not added, and it is preferable to suppress the concentration to a low concentration of 2 mass% or less.
【0042】実施例A〜Fのパウダを用いて鋳造すれ
ば、パウダ溶融層中のMnO 濃度は2mass%以下と問題の
ない低濃度に抑制することができた。さらに、溶融した
パウダがモールド・凝固シェルの間隔に流入後、凝固す
る際の結晶化が適度であるので鋳込中のモールド内熱流
束変動は小さい。また、スラグリムの成長も小さく、操
業上・品質上の問題がない。When casting was performed using the powders of Examples A to F, the MnO concentration in the powder molten layer could be suppressed to 2 mass% or less, which was a problem-free low concentration. Furthermore, since the molten powder flows into the space between the mold and the solidified shell and then solidifies properly when solidified, the heat flux fluctuation in the mold during casting is small. In addition, the growth of slag rim is small, and there are no operational and quality problems.
【0043】それに対し、丸断面鋳片の連続鋳造に従来
広く供されてきたパウダの1例である比較例Gは、CaO*
/SiO2 の比が小さくAl2O3 濃度も低いのでSiO2活量が高
い。その結果、パウダ溶融層中のMnO 濃度が高く品質上
の問題を生じた。On the other hand, Comparative Example G, which is an example of a powder that has been widely used in the continuous casting of cast slabs having a round cross section, is CaO *
Since the ratio of / SiO 2 is small and the concentration of Al 2 O 3 is low, the activity of SiO 2 is high. As a result, the MnO concentration in the powder melted layer was high and caused a quality problem.
【0044】比較例Hは、CaO*/SiO2 が1.00と高いので
溶融パウダ中MnO 濃度は低位であるものの、酸性酸化物
として作用するAl2O3 濃度が5.5 %と低いので溶融した
パウダが、モールド・凝固シェル間隔に流入後凝固する
際に過度に結晶化するので、鋳込中のモールド内熱流束
変動が大きくなるという問題を生じた。モールド内熱流
束変動が大きいと、局部的な冷却不均一が生じ鋳片表面
の割れ性欠陥や、鋳片割れに起因するブレークアウトが
発生するなどの品質ならびに操業上のトラブルとなる。
さらに比較例HではNa2O濃度が高いのでスラグリムが大
きく成長し操業を阻害した。In Comparative Example H, although the CaO * / SiO 2 content was as high as 1.00, the concentration of MnO in the molten powder was low, but the concentration of Al 2 O 3 acting as an acidic oxide was as low as 5.5%, so that the molten powder was not. However, since excessive crystallization occurs during solidification after flowing into the gap between the mold and the solidified shell, there has been a problem that heat flux fluctuations in the mold during casting become large. If the heat flux variation in the mold is large, local cooling unevenness occurs, resulting in quality and operation troubles such as cracking defects on the slab surface and breakout due to slab cracking.
Further, in Comparative Example H, since the concentration of Na 2 O was high, the slag rim grew greatly and hindered the operation.
【0045】比較例IはCaO-Al2O3 を主組成とする特開
昭57−184563号公報に開示された発明例である。このパ
ウダはSiO2濃度が低いのでパウダ溶融層中のMnO 濃度は
低いものの、極めて高塩基度であるために、Al2O3 濃度
の上昇によっても凝固時の結晶化抑制が不十分であっ
た。ゆえに、鋳込中のモールド内熱流束変動が大きく、
実操業への適用は困難であった。さらに、物性調整のた
めに加えられたFの濃度が10mass%と高いので、モール
ド内に浸漬された耐火物製溶鋼注入ノズルの溶損が大き
いという操業上の問題を生じた。Comparative Example I is an example of the invention disclosed in JP-A-57-184563 having CaO-Al 2 O 3 as a main composition. This powder has a low SiO 2 concentration, so the MnO concentration in the powder melt layer is low, but it has a very high basicity, and the crystallization suppression during solidification was insufficient even with an increase in Al 2 O 3 concentration. . Therefore, the heat flux fluctuation in the mold during casting is large,
Application to actual operations was difficult. Furthermore, since the concentration of F added for adjusting the physical properties is as high as 10 mass%, there is an operational problem that the molten steel injection nozzle immersed in the mold has a large melt damage.
【0046】また、比較例IはNa2O濃度が5mass%と高
いが、スラグリムの成長はほとんどなかった。これは、
Na2Oと反応し低融点液相と生じるSiO2の濃度が低いため
と考えられる。In Comparative Example I, although the Na 2 O concentration was as high as 5 mass%, the growth of slag rim hardly occurred. this is,
This is probably due to the low concentration of SiO 2 that forms a low melting point liquid phase by reacting with Na 2 O.
【0047】[0047]
【発明の効果】このように本発明によるパウダは、丸断
面鋳片の連続鋳造に際し、要求される諸機能を満足する
と同時に、高Mn鋼鋳込時のパウダ溶融層中MnO 濃度が低
いので、MnO に起因する気泡性欠陥が発生せず良好な鋳
片表面性状を得ることができる。As described above, the powder according to the present invention satisfies various functions required for continuous casting of a slab having a round cross section and, at the same time, has a low MnO concentration in a powder molten layer at the time of high Mn steel casting. Good slab surface properties can be obtained without generation of bubble defects caused by MnO.
【図1】溶鋼中のMn濃度と溶融パウダ層のMnO 濃度およ
び塩基度変化との関係を示すグラフである。FIG. 1 is a graph showing the relationship between the Mn concentration in molten steel, the MnO concentration in a molten powder layer, and a change in basicity.
【図2】溶融前のパウダのSiO2濃度と溶融パウダ中のMn
O 濃度との関係を示すグラフである。FIG. 2 SiO 2 concentration of powder before melting and Mn in molten powder
4 is a graph showing a relationship with O concentration.
【図3】遠心力をかけたときに溶融パウダから溶鋼への
Mnの移行が促進される様子を示す模式的説明図である。FIG. 3 shows that when centrifugal force is applied,
FIG. 9 is a schematic explanatory view showing a state where the transfer of Mn is promoted.
【図4】溶鋼中のMn濃度と気泡性欠陥の発生傾向との関
係を示すグラフである。FIG. 4 is a graph showing the relationship between the Mn concentration in molten steel and the tendency to generate cellular defects.
【図5】Al2O3 濃度と1300℃における粘度との関係を示
すグラフである。FIG. 5 is a graph showing the relationship between Al 2 O 3 concentration and viscosity at 1300 ° C.
【図6】塩基度と凝固温度との関係を示すグラフであ
る。FIG. 6 is a graph showing the relationship between basicity and solidification temperature.
【図7】スラグリムの形成機構の模式的説明図である。FIG. 7 is a schematic explanatory view of a slag rim forming mechanism.
【図8】Na2O濃度とスラグリム成長速度との関係を示す
グラフである。FIG. 8 is a graph showing the relationship between Na 2 O concentration and slag rim growth rate.
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 平2−284749(JP,A) 特開 昭50−77209(JP,A) 特開 平4−224063(JP,A) 特開 平4−319056(JP,A) 特開 昭63−188459(JP,A) 特開 平7−214263(JP,A) 特開 平8−25008(JP,A) 特開 昭57−184563(JP,A) 特開 昭60−133956(JP,A) 特開 平11−320058(JP,A) 特開 平5−185195(JP,A) 特開 平9−85404(JP,A) (58)調査した分野(Int.Cl.7,DB名) B22D 11/108 B22D 11/00 B22D 11/115 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-284749 (JP, A) JP-A-50-77209 (JP, A) JP-A-4-224063 (JP, A) JP-A-4-27 319056 (JP, A) JP-A-63-188459 (JP, A) JP-A-7-214263 (JP, A) JP-A 8-25008 (JP, A) JP-A-57-184563 (JP, A) JP-A-60-133956 (JP, A) JP-A-11-320058 (JP, A) JP-A-5-185195 (JP, A) JP-A-9-85404 (JP, A) (58) (Int.Cl. 7 , DB name) B22D 11/108 B22D 11/00 B22D 11/115
Claims (2)
鋳片の連続鋳造用モールドパウダであって、CaO*を総Ca
のCaO 換算重量とすると、 CaO*とSiO2の重量比、CaO*/SiO2 =0.95〜1.40 Al2O3 濃度 Al2O3 =10〜30mass% Na2O 濃度 Na2O≦4mass% を満足する化学組成を有することを特徴とするモールド
パウダ。1. A mold powder for continuous casting of a high-Mn round section cast slab containing Mn: 0.8 mass% or more, wherein CaO * is a total Ca
When the CaO-converted weight, CaO * the weight ratio of SiO 2, CaO * / SiO 2 = 0.95~1.40 Al 2 O 3 concentration Al 2 O 3 = 10~30mass% Na 2 O concentration Na 2 O ≦ 4mass% of A mold powder having a satisfactory chemical composition.
ss%以上含有する高Mn丸断面鋳片を連続鋳造する際に、
モールド内の溶鋼表面に、請求項1記載のモールドパウ
ダを投入することを特徴とする高Mn丸断面鋳片の連続鋳
造方法。2. Mn: 0.8 ma while performing electromagnetic stirring in the mold.
When continuously casting high Mn round section slabs containing ss% or more,
A method for continuously casting a high-Mn round-section slab, wherein the mold powder according to claim 1 is poured into a surface of molten steel in a mold.
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JP35130598A JP3317258B2 (en) | 1998-01-09 | 1998-12-10 | Mold powder for continuous casting of high Mn round section slabs |
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JP10-3090 | 1998-01-09 | ||
JP309098 | 1998-01-09 | ||
JP35130598A JP3317258B2 (en) | 1998-01-09 | 1998-12-10 | Mold powder for continuous casting of high Mn round section slabs |
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KR100524432B1 (en) * | 2002-09-28 | 2005-10-27 | 스톨베르그 앤드 삼일 주식회사 | Premelted manganese slag composition for production of mold flux and mold flux manufactured therefrom |
JP2010115714A (en) * | 2010-03-05 | 2010-05-27 | Jfe Engineering Corp | Mold powder |
KR101235609B1 (en) | 2011-01-28 | 2013-02-21 | 현대제철 주식회사 | Mold powder composition for high-manganese steel |
JP6102501B2 (en) * | 2013-05-20 | 2017-03-29 | 新日鐵住金株式会社 | High Cr steel continuous casting method |
CN104084550B (en) * | 2014-07-28 | 2016-04-27 | 重庆钢铁(集团)有限责任公司 | The continuous casting steel billet production control method of rolling slab |
CN104607608B (en) * | 2015-01-29 | 2017-02-22 | 中南大学 | Medium manganese steel casting powder for automobile and application thereof |
CN109382489A (en) * | 2017-08-10 | 2019-02-26 | 上海梅山钢铁股份有限公司 | A kind of carbon aluminium-killed steel crystallizer protecting residue |
CN109439943B (en) * | 2018-12-06 | 2020-01-07 | 广州纳联材料科技有限公司 | Flux for smelting cobalt-chromium alloy and application thereof |
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