JP4646849B2 - Mold powder for continuous casting of high aluminum steel - Google Patents
Mold powder for continuous casting of high aluminum steel Download PDFInfo
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本発明は、高アルミニウム鋼、殊に溶存Ａｌ量が０．１質量％以上である鋼の連続鋳造に用いられるモールドパウダーに関するものである。 The present invention relates to a mold powder used for continuous casting of high aluminum steel, particularly steel having a dissolved Al content of 0.1% by mass or more.
鋼の連続鋳造では、モールドパウダーが、鋳型内の溶鋼表面上に添加される。これは、溶鋼からの熱で滓化溶融し、溶融スラグ層を形成し、順次鋳型と凝固シェルとの隙間に流入して、消費される。モールドパウダーは、主にＣａＯとＳｉＯ2とからなり、さらに溶融スラグの粘度や凝固温度を調整するためにＡｌ2Ｏ3、ＭｇＯ、Ｎａ2Ｏ、ＦやＬｉ2Ｏなど、またスラグの溶融速度を調整するためにＣなどが加えられている。このモールドパウダーの主な役割としては、（ア）鋳型および凝固シェル間の潤滑性を確保すること、および（イ）凝固シェルから鋳型への抜熱速度を抑えて緩冷却させることなどが挙げられる。 In continuous casting of steel, mold powder is added onto the molten steel surface in the mold. This melts and melts with the heat from the molten steel, forms a molten slag layer, and then flows into the gap between the mold and the solidified shell and is consumed. The mold powder is mainly composed of CaO and SiO 2, and Al 2 O 3 , MgO, Na 2 O, F, Li 2 O, etc. to adjust the viscosity and solidification temperature of the molten slag, and the slag melting rate C or the like is added to adjust the value. The main roles of this mold powder include (a) ensuring lubricity between the mold and the solidified shell, and (b) slow cooling by suppressing the heat removal rate from the solidified shell to the mold. .
まず上記（ア）で挙げた鋳型および凝固シェル間の潤滑性を確保するためには、鋳型および凝固シェルの隙間にモールドパウダーから得られる溶融スラグが適正量流入するように、その粘度および凝固温度を適正に設定することが重要である。一般的に高速鋳造となるほど、溶融スラグの流入量を確保するため、低粘度のものが使用される。 First, in order to ensure lubricity between the mold and the solidified shell mentioned in (a) above, the viscosity and solidification temperature so that an appropriate amount of molten slag obtained from mold powder flows into the gap between the mold and the solidified shell. It is important to set properly. In general, the higher the casting speed, the lower the viscosity of the molten slag in order to ensure the inflow.
また上記（イ）の緩冷却は、得られる鋳片の表面品質に直結するため重要である。亜包晶鋼のように鋳片表面割れの発生しやすい鋼種では、特に緩冷却が必要とされる。緩冷却のためには、モールドパウダーから得られるスラグフィルム中、特にその鋳型側表面に結晶を晶出させることが有効である。スラグフィルムの鋳型側表面に結晶が晶出すると、フィルムと鋳型との間に凹凸が形成され、この凹凸に含まれる空気層が断熱層として作用するからである。この結晶として、カスピダイン（３ＣａＯ・２ＳｉＯ2・ＣａＦ2）が、一般的に利用されている。 In addition, the slow cooling (b) is important because it directly affects the surface quality of the resulting slab. In the case of a steel type such as hypoperitectic steel, where slab surface cracks are likely to occur, particularly slow cooling is required. For slow cooling, it is effective to crystallize the slag film obtained from the mold powder, particularly on the mold side surface. This is because when crystals crystallize on the mold side surface of the slag film, irregularities are formed between the film and the mold, and the air layer contained in the irregularities acts as a heat insulating layer. As this crystal, caspidine (3CaO · 2SiO 2 · CaF 2 ) is generally used.
しかし溶存Ａｌ量が０．１％以上であるような高アルミニウム鋼の連続鋳造では、（ア）の潤滑性の確保、および（イ）の緩冷却が困難となる。なぜなら高アルミニウム鋼の連続鋳造では、下記の式（３）：
４Ａｌ＋３ＳｉＯ2 → ２Ａｌ2Ｏ3＋３Ｓｉ … （３）
で表される化学反応により、ＳｉＯ2が消費されるからである。そのため溶融スラグ中における塩基度［ＣａＯ］／［ＳｉＯ2］が上昇して、凝固温度が著しく上昇する。そして鋳型壁面にスラグベアと呼ばれる硬い焼結物ができ、溶融スラグの流入が阻害される。その結果、潤滑性が損なわれて、凝固シェルと鋳型とが焼き付き、ブレークアウトが発生してしまう。
However, in continuous casting of high aluminum steel having a dissolved Al content of 0.1% or more, it becomes difficult to ensure the lubricity of (a) and to slowly cool (a). Because in the continuous casting of high aluminum steel, the following formula (3):
4Al + 3SiO 2 → 2Al 2 O 3 + 3Si (3)
This is because SiO 2 is consumed by the chemical reaction represented by Therefore, the basicity [CaO] / [SiO 2 ] in the molten slag is increased, and the solidification temperature is remarkably increased. And a hard sintered material called a slag bear is made on the mold wall surface, and the inflow of molten slag is hindered. As a result, the lubricity is impaired, the solidified shell and the mold are seized, and breakout occurs.
また上記（３）式の反応により、溶融スラグが組成変動を受けるため、カスピダインを安定して生成させることが困難になる。このように高アルミニウム鋼の連続鋳造では、上記式（３）の反応による組成変動が生ずるために、表面品質に優れた鋳片を、安定して製造することが難しい。 In addition, due to the reaction of the above formula (3), the molten slag is subjected to composition fluctuations, so that it is difficult to stably generate caspidine. Thus, in the continuous casting of high aluminum steel, composition fluctuations due to the reaction of the above formula (3) occur, and it is difficult to stably produce a slab having excellent surface quality.
そこで特許文献１は、高アルミニウム鋼の連続鋳造でも表面品質に優れた鋳片を製造するため、殊にスラグベアの生成を抑制するため、低塩基度で、かつ高粘度で結晶が晶出しにくい組成および物性を有するモールドパウダーを提案している（特許請求の範囲、段落［０００４］および［０００７］）。 Therefore, Patent Document 1 is a composition having a low basicity and a high viscosity that makes it difficult for crystals to crystallize in order to produce a slab excellent in surface quality even in continuous casting of high aluminum steel, and particularly to suppress the formation of slag bear. And mold powders having physical properties are proposed (claims, paragraphs [0004] and [0007]).
また特許文献２は、カスピダインとは異なる複合結晶を生じさせて緩冷却を達成するため、周期律表ＩＡ族に属する元素の酸化物を２種類以上含有するモールドパウダーを開示している（特許請求の範囲および段落［００１３］）。なお特許文献２の発明では、想定する複合結晶として、ＬｉＣａ2ＦＳｉＯ4やＮａＣａ2ＦＳｉＯ4などを開示しているが、実施例で用いられている周期律表ＩＡ族に属する元素の酸化物の中では、Ｎａ2Ｏ量が最も多いことから、メインの複合結晶としてＮａＣａ2ＦＳｉＯ4を想定していると考えられる（段落［００２０］および［００３０］）。また特許文献２の発明は、モールドパウダーの軟化温度を低減させることが目的であるため、周期律表ＩＡ族に属する元素の酸化物を２種類以上含有することを特徴としている（段落［００２４］）。 Patent Document 2 discloses a mold powder containing two or more kinds of oxides of elements belonging to Group IA of the Periodic Table in order to achieve a slow cooling by generating a composite crystal different from caspidine. And paragraph [0013]). In the invention of Patent Document 2, LiCa 2 FSiO 4 and NaCa 2 FSiO 4 are disclosed as assumed composite crystals. However, oxides of elements belonging to group IA of the periodic table used in the examples are disclosed. Among them, since the amount of Na 2 O is the largest, it is considered that NaCa 2 FSiO 4 is assumed as the main composite crystal (paragraphs [0020] and [0030]). The invention of Patent Document 2 is characterized by containing two or more oxides of elements belonging to Group IA of the Periodic Table because the purpose is to reduce the softening temperature of the mold powder (paragraph [0024] ).
特許文献３は、高アルミニウム鋼の連続鋳造において、ＡｌとＳｉＯ2との反応（上記式（３））によりＡｌ2Ｏ3含有率が増加する際に、凝固温度および粘度が増加して、ブレークアウトの発生および鋳片の表面品質の悪化を防止するために、ＣａＯ、ＳｉＯ2 、Ｌｉ2Ｏ、Ｆ、Ｎａ2Ｏ、Ｋ2ＯおよびＡｌ2Ｏ3含有率が所定の式を満たし、溶融層が凝固したフィルム中に、カスピダインの結晶が晶出するような組成を有するモールドパウダーを提案している（特許請求の範囲、段落［００１１］および［００１７］）。
上記のように従来技術では、鋼（殊に高アルミニウム鋼）の連続鋳造で表面品質に優れた鋳片を製造するために、様々なモールドパウダーが提案されている。しかし技術分野では、さらなる改良が絶えず求められる。従って本発明の目的は、溶存Ａｌ量が０．１％以上である高アルミニウム鋼を連続鋳造する場合でも、鋳片表面の凹みや割れの発生を防止して、表面品質に優れた鋳片を製造できるモールドパウダーを提供することにある。 As described above, in the prior art, various mold powders have been proposed in order to produce a slab excellent in surface quality by continuous casting of steel (particularly high aluminum steel). However, further improvements are continually required in the technical field. Therefore, the object of the present invention is to prevent the occurrence of dents and cracks on the surface of the slab, even when continuously casting high aluminum steel having a dissolved Al content of 0.1% or more, and to produce a slab having excellent surface quality. The object is to provide a mold powder that can be manufactured.
上記目的を達成し得た本発明のモールドパウダーとは、
Ｔ−ＣａＯ：３５〜５５％（質量％の意味、以下同じ）、
ＳｉＯ2：１０〜３０％、
Ａｌ2Ｏ3：４．０％以下（０％を含まない）、
ＭｇＯ：０．２〜１．０％、
Ｌｉ2Ｏ：７〜１３％、
Ｆ：７〜１３％、
Ｃ：１０．５〜１４％、
および不可避不純物からなり、
下記式（１）および（２）：
１．６≦［Ｔ−ＣａＯ］／［ＳｉＯ2］≦５ … （１）
０．２≦［Ｌｉ2Ｏ］／［ＳｉＯ2］≦１．１ … （２）
〔式中、［Ｔ−ＣａＯ］、［ＳｉＯ2］および［Ｌｉ2Ｏ］は、それぞれ、Ｔ−ＣａＯ、ＳｉＯ2およびＬｉ2Ｏのモールドパウダー中の含有量（質量％）を表す。〕
を満たすことを特徴とする、溶存Ａｌ量が０．１％以上である鋼を連続鋳造するためのモールドパウダーである。
The mold powder of the present invention that can achieve the above-mentioned object is:
T-CaO: 35 to 55% (meaning mass%, the same shall apply hereinafter),
SiO 2: 10~30%,
Al 2 O 3 : 4.0% or less (excluding 0%),
MgO: 0.2-1.0%,
Li 2 O: 7-13%
F: 7-13%
C: 10.5-14%
And consisting of inevitable impurities
The following formulas (1) and (2):
1.6 ≦ [T-CaO] / [SiO 2 ] ≦ 5 (1)
0.2 ≦ [Li 2 O] / [SiO 2 ] ≦ 1.1 (2)
[Wherein, [T-CaO], [SiO 2 ] and [Li 2 O] represent the contents (mass%) of T-CaO, SiO 2 and Li 2 O in the mold powder, respectively. ]
A mold powder for continuously casting steel having a dissolved Al content of 0.1% or more.
本発明のモールドパウダーを連続鋳造に用いると、鋳片表面の凹みや割れが防止されて表面品質に優れた高アルミニウム鋼を製造することができる。 When the mold powder of the present invention is used for continuous casting, dents and cracks on the surface of the slab can be prevented and high aluminum steel having excellent surface quality can be produced.
亜包晶鋼のように鋳片表面割れの発生しやすい鋼種では、割れを抑制するために、抜熱速度を低下させて、緩冷却することが重要である。そのため従来では、一般的に、モールドパウダーから得られるスラグフィルム中にカスピダイン（３ＣａＯ・２ＳｉＯ2・ＣａＦ2）を晶出させて、その鋳型側表面に凹凸（空気による断熱層）を形成させることにより、緩冷却を達成していた。しかし高アルミニウム鋼の場合は、組成変動のために、カスピダインを安定して生成させることが困難である。そこで本発明者らは、スラグフィルム中に、カスピダインに代わる結晶を晶出させることを検討した。 In a steel type such as hypoperitectic steel, where slab surface cracks are likely to occur, it is important to cool slowly by decreasing the heat removal rate in order to suppress cracking. Therefore, conventionally, by generally crystallizing caspidine (3CaO · 2SiO 2 · CaF 2 ) in a slag film obtained from mold powder, an unevenness (heat insulation layer by air) is formed on the mold side surface. Was achieving slow cooling. However, in the case of high aluminum steel, it is difficult to stably produce cuspidyne due to composition variation. Accordingly, the present inventors have studied to crystallize crystals instead of cuspidine in a slag film.
しかし緩冷却のために、ダイカルシウムシリケート（２ＣａＯ・ＳｉＯ2）、メイエナイト（１２ＣａＯ・７Ａｌ2Ｏ3）およびゲーレナイト（３ＣａＯ・２ＳｉＯ2・Ａｌ2Ｏ3）のような結晶を晶出させると、鋳型銅板温度の変動が大きくなる問題がある上に、鋳片の凹みや割れの防止には有効ではない。これらは、粗大な結晶として、スラグフィルム中で不均一に晶出するため、鋳型側の表面に不均一な凹凸（空気層）を形成し、その結果、抜熱速度にバラツキが生ずる。そうすると凝固シェルの厚みが不均一になるため、変態収縮で、鋳片表面に凹みや割れが発生すると考えられる。 However, when crystals such as dicalcium silicate (2CaO · SiO 2 ), mayenite (12CaO · 7Al 2 O 3 ) and gelenite (3CaO · 2SiO 2 · Al 2 O 3 ) are crystallized for slow cooling, the template In addition to the problem of large fluctuations in the copper plate temperature, it is not effective in preventing slab dents and cracks. Since these crystallize non-uniformly in the slag film as coarse crystals, non-uniform irregularities (air layers) are formed on the surface on the mold side, resulting in variations in the heat removal rate. Then, since the thickness of the solidified shell becomes non-uniform, it is considered that dents and cracks are generated on the slab surface due to transformation shrinkage.
そこで鋭意検討した結果、カスピダインの代わりに、ＬｉＡｌＯ2をスラグフィルム中に晶出させることで、鋳片の凹みや割れを、有効に防止できることを見出した。ＬｉＡｌＯ2を晶出させることにより、鋳片の凹みや割れを防止できる正確なメカニズムは不明であるが、次のように推定できる。 As a result of intensive studies, it was found that dents and cracks in the slab can be effectively prevented by allowing LiAlO 2 to crystallize in the slag film instead of caspidine. The exact mechanism by which LiAlO 2 is crystallized to prevent slab dents and cracks is unknown, but can be estimated as follows.
ＬｉＡｌＯ2は、スラグフィルムの鋳型側表面に、微細な結晶として均一に晶出するため、均一な空気層が形成される。その結果、均一な抜熱が達成され、鋳型銅板温度の変動が小さく、また緩冷却により、割れが防止されることに加えて、均一な厚みの凝固シェルが形成されることにより、変態収縮による鋳片の凹凸や割れも抑制されると考えられる。但し、本発明はこのような推定メカニズムに限定されない。 Since LiAlO 2 crystallizes uniformly as fine crystals on the mold side surface of the slag film, a uniform air layer is formed. As a result, uniform heat removal is achieved, fluctuations in the mold copper plate temperature are small, and cracking is prevented by slow cooling, and a solidified shell of uniform thickness is formed, resulting in transformation shrinkage. It is thought that unevenness and cracking of the slab are also suppressed. However, the present invention is not limited to such an estimation mechanism.
本発明では、モールドパウダーからのＳｉＯ2と溶鋼からのＡｌとが反応して形成されるＡｌ2Ｏ3に、モールドパウダーからのＬｉ2Ｏを反応させて、ＬｉＡｌＯ2を晶出させることを意図している。即ち、本発明は、高アルミニウム鋼の連続鋳造で、組成変動の原因となる上記式（３）のＳｉＯ2とＡｌとの反応を利用して、ＬｉＡｌＯ2を晶出させる点に要旨がある。そこで本発明のモールドパウダーは、ＬｉＡｌＯ2を晶出させるために、各成分量、殊にＴ−ＣａＯ、ＳｉＯ2およびＬｉ2Ｏ量、並びにこれらの質量比［Ｌｉ2Ｏ］／［ＳｉＯ2］および塩基度［Ｔ−ＣａＯ］／［ＳｉＯ2］が、適正範囲に調整されていることを特徴とする。 The present invention intends to crystallize LiAlO 2 by reacting Li 2 O from mold powder with Al 2 O 3 formed by reaction of SiO 2 from mold powder and Al from molten steel. is doing. That is, the gist of the present invention is to crystallize LiAlO 2 by utilizing the reaction between SiO 2 and Al of the above formula (3), which causes composition fluctuations, in continuous casting of high aluminum steel. Therefore, the mold powder of the present invention is used to crystallize LiAlO 2 , the amount of each component, in particular, the amount of T-CaO, SiO 2 and Li 2 O, and their mass ratio [Li 2 O] / [SiO 2 ]. and basicity [T-CaO] / [SiO 2] , characterized in that it is adjusted to a proper range.
さらに溶融スラグ（モールドパウダー）の凝固温度を適正範囲に調整して、潤滑性を確保するという観点から、各成分組成が適正範囲に調整されていることも、本発明のモールドパウダーの特徴である。以下、本発明のモールドパウダー中の各成分量、塩基度［Ｔ−ＣａＯ］／［ＳｉＯ2］および質量比［Ｌｉ2Ｏ］／［ＳｉＯ2］を、それぞれ説明する。 Further, from the viewpoint of ensuring lubricity by adjusting the solidification temperature of molten slag (mold powder) to an appropriate range, it is also a feature of the mold powder of the present invention that each component composition is adjusted to an appropriate range. . Hereinafter, each component amount, basicity [T-CaO] / [SiO 2 ] and mass ratio [Li 2 O] / [SiO 2 ] in the mold powder of the present invention will be described.
〈Ｔ−ＣａＯ：３５〜５５％〉
本発明において「Ｔ−ＣａＯ」とは、モールドパウダー中に含まれる全てのＣａを、ＣａＯに換算した際のＣａＯ量（質量％）を表す。モールドパウダー中のＴ−ＣａＯ量は、３５％以上、好ましくは３８％以上、より好ましくは４０％以上であり、５５％以下、好ましくは５０％以下、より好ましくは４８％以下である。Ｔ−ＣａＯ量が３５％未満であると、相対的にＳｉＯ2量が増加し、その結果、式（３）の反応によりＡｌ2Ｏ3量も増加し、ＬｉＡｌＯ2が晶出しやすい組成範囲から外れて、ＬｉＡｌＯ2が晶出しにくくなる。またゲーレナイト（３ＣａＯ・２ＳｉＯ2・Ａｌ2Ｏ3）も生成しやすくなる。逆にＴ−ＣａＯ量が５５％を超えても、相対的にＬｉ2ＯおよびＳｉＯ2量が低下し、その結果、式（３）の反応によりＡｌ2Ｏ3量も低下して、充分な量のＬｉＡｌＯ2が確保できなくなる。また溶融スラグの凝固温度が高くなりすぎる。
<T-CaO: 35-55%>
In the present invention, “T-CaO” represents the CaO amount (% by mass) when all Ca contained in the mold powder is converted to CaO. The amount of T-CaO in the mold powder is 35% or more, preferably 38% or more, more preferably 40% or more, 55% or less, preferably 50% or less, more preferably 48% or less. When the amount of T-CaO is less than 35%, the amount of SiO 2 is relatively increased. As a result, the amount of Al 2 O 3 is also increased by the reaction of formula (3), and LiAlO 2 is easily crystallized. This makes it difficult to crystallize LiAlO 2 . Also, gehlenite (3CaO.2SiO 2 .Al 2 O 3 ) is easily generated. On the other hand, even if the amount of T-CaO exceeds 55%, the amounts of Li 2 O and SiO 2 are relatively decreased, and as a result, the amount of Al 2 O 3 is also decreased due to the reaction of formula (3). An amount of LiAlO 2 cannot be secured. Also, the solidification temperature of the molten slag becomes too high.
〈ＳｉＯ2：１０〜３０％〉
ＳｉＯ2量は、１０％以上、好ましくは１５％以上であり、３０％以下、好ましくは２８％以下、より好ましくは２５％以下である。ガラス形成元素であるＳｉＯ2量が１０％未満であると、結晶が発達しやすいため、粗大な結晶が形成されて、スラグフィルムの鋳型側表面に不均一な凹凸が形成される。また凝固温度も上昇し、潤滑性が損なわれて、スラグベアが生成しやすくなる。逆にＳｉＯ2量が３０％を超えると、ＬｉＡｌＯ2よりも、ゲーレナイト（３ＣａＯ・２ＳｉＯ2・Ａｌ2Ｏ3）やダイカルシウムシリケート（２ＣａＯ・ＳｉＯ2）が多く晶出する。
<SiO 2: 10~30%>
The amount of SiO 2 is 10% or more, preferably 15% or more, 30% or less, preferably 28% or less, more preferably 25% or less. If the amount of SiO 2 that is a glass-forming element is less than 10%, crystals are likely to develop, so that coarse crystals are formed and uneven irregularities are formed on the mold side surface of the slag film. In addition, the solidification temperature rises, the lubricity is impaired, and slag bear is easily generated. On the contrary, when the amount of SiO 2 exceeds 30%, more gehlenite (3CaO · 2SiO 2 · Al 2 O 3 ) and dicalcium silicate (2CaO · SiO 2 ) are crystallized than LiAlO 2 .
〈Ａｌ2Ｏ3：４．０％以下（０％を含まない）〉
溶融スラグの凝固温度および粘度の上昇を防止するため、Ａｌ2Ｏ3量は、４．０％以下、好ましくは３％以下、より好ましくは２％以下である。但しＡｌ2Ｏ3は、モールドパウダーの製造で不可避不純物として混入されるため、この量を０％にすることは工業的に困難である。
<Al 2 O 3 : 4.0% or less (excluding 0%)>
In order to prevent the solidification temperature and viscosity of the molten slag from increasing, the amount of Al 2 O 3 is 4.0% or less, preferably 3% or less, more preferably 2% or less. However, since Al 2 O 3 is mixed as an inevitable impurity in the production of mold powder, it is industrially difficult to reduce this amount to 0%.
〈ＭｇＯ：０．２〜１．０％〉
ＭｇＯ量は、０．２％以上、好ましくは０．３％以上、より好ましくは０．４％以上であり、１．０％以下、好ましくは０．９％以下、より好ましくは０．８％以下である。ＭｇＯは、スラグフィルム中で結晶が晶出するための核として作用する。そのためＭｇＯ量が１．０％を超えると、核が多くなりすぎて結晶の晶出を適切に制御できなくなり、殊にモールドパウダー組成によっては、ダイカルシウムシリケート（２ＣａＯ・ＳｉＯ2）やメイエナイト（１２ＣａＯ・７Ａｌ2Ｏ3）が優先的に晶出する場合がある。一方、ＭｇＯ量が０．２％未満であると、結晶の核が少なすぎるため、低温の平衡温度に達するまでは結晶が充分に晶出せず、殊に溶鋼が高温である鋳型メニスカス直下では、緩冷却が行いにくい。また平衡温度に達すると、粗大な結晶が一度に晶出するため、抜熱速度にバラツキが生じる。
<MgO: 0.2 to 1.0%>
The amount of MgO is 0.2% or more, preferably 0.3% or more, more preferably 0.4% or more, 1.0% or less, preferably 0.9% or less, more preferably 0.8%. It is as follows. MgO acts as a nucleus for crystallizing in the slag film. For that reason MgO content exceeds 1.0%, the nucleus becomes too many will not be able to properly control the crystallization of the crystal, by particular mold powder composition, dicalcium silicate (2CaO · SiO 2) and Meienaito (12CaO · 7Al 2 O 3) is sometimes crystallizes preferentially. On the other hand, if the amount of MgO is less than 0.2%, the number of crystal nuclei is too small, so that the crystal does not crystallize sufficiently until the low temperature equilibrium temperature is reached. It is difficult to perform slow cooling. Also, when the equilibrium temperature is reached, coarse crystals are crystallized at a time, resulting in variations in the heat removal rate.
〈Ｌｉ2Ｏ：７〜１３％〉
Ｌｉ2Ｏ量は、７％以上、好ましくは７．５％以上、より好ましくは８．０％以上であり、１３％以下、好ましくは１２％以下、より好ましくは１１％以下である。Ｌｉ2Ｏ量が７％未満であると、充分な量のＬｉＡｌＯ2を晶出させることが難しく、また溶融スラグの凝固温度および粘度が上昇して、潤滑性が確保できない場合がある。逆にＬｉ2Ｏ量が１３％を超えても、ＬｉＡｌＯ2が晶出する最適範囲から外れて、その晶出量が低下し、緩冷却が達成されない場合がある。さらに溶融パウダーの粘度が大きく低下して、溶融スラグが局所的に過剰流入したり、脈動が生じて、連続鋳造の安定操業に悪影響を及ぼすことがある。
<Li 2 O: 7~13%>
The amount of Li 2 O is 7% or more, preferably 7.5% or more, more preferably 8.0% or more, and 13% or less, preferably 12% or less, more preferably 11% or less. When the amount of Li 2 O is less than 7%, it is difficult to crystallize a sufficient amount of LiAlO 2 , and the solidification temperature and viscosity of the molten slag increase, and lubricity may not be ensured. On the other hand, even if the Li 2 O content exceeds 13%, the LiAlO 2 may deviate from the optimum range for crystallization, the crystallization amount may decrease, and slow cooling may not be achieved. Further, the viscosity of the molten powder is greatly reduced, and the molten slag may locally flow excessively or pulsate, which may adversely affect the stable operation of continuous casting.
〈Ｆ：７〜１３％〉
Ｆ量は、７％以上、好ましくは７．５％以上、より好ましくは８．０％以上であり、１３％以下、好ましくは１２％以下、より好ましくは１１％以下である。Ｆ量が７％未満であると、溶融スラグの粘度が上昇し、潤滑性を確保できなくなる場合がある。一方、Ｆは、ＬｉＡｌＯ2の晶出を抑制する作用を有し、殊にＦ量が１３％を超えると、ＬｉＡｌＯ2の晶出量が急激に低減する。
<F: 7-13%>
The amount of F is 7% or more, preferably 7.5% or more, more preferably 8.0% or more, and 13% or less, preferably 12% or less, more preferably 11% or less. If the F amount is less than 7%, the viscosity of the molten slag increases, and lubricity may not be ensured. On the other hand, F has an effect of suppressing crystallization of LiAlO 2 , and particularly when the F amount exceeds 13%, the crystallization amount of LiAlO 2 is rapidly reduced.
〈Ｃ：１０．５〜１４％〉
本発明で規定するＣ量は、モールドパウダー中に含まれる全てのＣ量を表す。即ち本発明のＣ量は、モールドパウダーの原料として添加されるような、単体の炭素量（遊離Ｃ量）と、例えばＬｉ2Ｏ原料として添加されるＬｉ2ＣＯ3などの化合物中の炭素量との合計を表す。モールドパウダー中のＣ量は、１０．５％以上、好ましくは１１．０％以上、より好ましくは１１．５％以上であり、１４％以下、好ましくは１３．５％以下、より好ましくは１３％以下である。Ｃ量が１０．５％未満であると、モールドパウダーの溶融速度が大きくなりすぎて、流入過多となり、不均一流入が生ずる。その結果、鋳片の縦割れが発生しやすくなる。逆にＣ量が１４％を超えると、溶融速度が小さくなりすぎて、充分なスラグフィルムの厚みが確保できなくなる。その結果、工業生産上で不可避的に発生する鋳型内の湯面変動の際に、スラグフィルムの膜切れを起こし、焼付きや、溶鋼が直接鋳型に接することによる急冷のために、鋳片の表面品質が劣化する。
<C: 10.5-14%>
The amount of C specified in the present invention represents all the amount of C contained in the mold powder. That C content of the present invention, such as is added as a raw material for mold powder, carbon content alone (free C amount) and, for example, the amount of carbon compounds in such Li 2 CO 3 added as Li 2 O feed And the total. The amount of C in the mold powder is 10.5% or more, preferably 11.0% or more, more preferably 11.5% or more, 14% or less, preferably 13.5% or less, more preferably 13%. It is as follows. If the amount of C is less than 10.5%, the melting rate of the mold powder becomes too high, resulting in excessive inflow and non-uniform inflow. As a result, the vertical crack of the slab is likely to occur. On the other hand, if the amount of C exceeds 14%, the melting rate becomes too small and a sufficient thickness of the slag film cannot be secured. As a result, slag film breakage occurs when the molten metal level in the mold inevitably occurs in industrial production, causing seizure and rapid cooling due to direct contact of the molten steel with the mold. Surface quality is degraded.
本発明のモールドパウダーは、上記成分および不可避不純物からなる。なお一般的なモールドパウダーには、粘度、凝固温度を低減させるために、Ｎａ2ＯやＫ2Ｏが添加されているが、本発明のモールドパウダーは、これらを含有しないことも特徴とする。なぜなら高アルミニウム鋼の連続鋳造では、下記の反応式（４）および（５）：
２Ａｌ＋３Ｎａ2Ｏ → Ａｌ2Ｏ3＋６Ｎａ … （４）
２Ａｌ＋３Ｋ2Ｏ → ２Ａｌ2Ｏ3＋６Ｋ … （５）
で示される化学反応が起こるため、Ｎａ2ＯやＫ2Ｏが消費されて、これらの作用が充分に発揮されず、本発明が想定する以上のＡｌ2Ｏ3が生成して、溶融スラグの凝固温度などに悪影響を及ぼすからである。またＮａ2Ｏが存在すると、Ｎａ−Ａｌ−Ｏ結晶が不均一に晶出して、スラグフィルムの凹凸（空気層）にバラツキが生ずることがある。
The mold powder of the present invention comprises the above components and inevitable impurities. In addition, in order to reduce viscosity and solidification temperature, Na 2 O and K 2 O are added to general mold powder, but the mold powder of the present invention is also characterized by not containing these. Because in the continuous casting of high aluminum steel, the following reaction formulas (4) and (5):
2Al + 3Na 2 O → Al 2 O 3 + 6Na (4)
2Al + 3K 2 O → 2Al 2 O 3 + 6K (5)
Therefore, Na 2 O and K 2 O are consumed, and these effects are not fully exhibited, and Al 2 O 3 more than expected by the present invention is generated, resulting in the formation of molten slag. This is because the coagulation temperature is adversely affected. In addition, when Na 2 O is present, Na—Al—O crystals may be crystallized non-uniformly, and unevenness in the slag film (air layer) may occur.
〈１．６≦［Ｔ−ＣａＯ］／［ＳｉＯ2］≦５〉
塩基度［Ｔ−ＣａＯ］／［ＳｉＯ2］は、１．６以上、好ましくは１．８以上、より好ましくは２．０以上であり、５以下、好ましくは４以下、より好ましくは３以下である。塩基度が１．６未満であると、相対的にＳｉＯ2量が増加し、ＬｉＡｌＯ2が晶出しやすい組成範囲から外れて、ＬｉＡｌＯ2が晶出しにくくなる。またゲーレナイト（３ＣａＯ・２ＳｉＯ2・Ａｌ2Ｏ3）も生成しやすくなる。逆に塩基度が５を超えても、相対的にＳｉＯ2量が減少し、それに伴いＡｌ2Ｏ3量およびＬｉＡｌＯ2量が減少する。またにガラス形成成分であるＳｉＯ2量が減少することで、メイエナイト（１２ＣａＯ・７Ａｌ2Ｏ3）が過度に発達してしまう。さらに凝固温度が高くなって潤滑性に悪影響を及ぼし得る。
<1.6 ≦ [T-CaO] / [SiO 2 ] ≦ 5>
The basicity [T-CaO] / [SiO 2 ] is 1.6 or more, preferably 1.8 or more, more preferably 2.0 or more, 5 or less, preferably 4 or less, more preferably 3 or less. is there. When the basicity is less than 1.6, the amount of SiO 2 is relatively increased, and LiAlO 2 deviates from the composition range in which LiAlO 2 is easily crystallized, and LiAlO 2 is hardly crystallized. Also, gehlenite (3CaO.2SiO 2 .Al 2 O 3 ) is easily generated. Conversely, even if the basicity exceeds 5, the amount of SiO 2 is relatively decreased, and the amounts of Al 2 O 3 and LiAlO 2 are decreased accordingly. Moreover, mayenite (12CaO · 7Al 2 O 3 ) develops excessively as the amount of SiO 2 that is a glass forming component decreases. Furthermore, the solidification temperature is increased, which can adversely affect the lubricity.
〈０．２≦［Ｌｉ2Ｏ］／［ＳｉＯ2］≦１．１〉
質量比［Ｌｉ2Ｏ］／［ＳｉＯ2］は、０．２以上、好ましくは０．３以上、より好ましくは０．４以上であり、１．１以下、好ましくは１．０以下、より好ましくは０．９以下である。［Ｌｉ2Ｏ］／［ＳｉＯ2］が０．２未満であると、Ｌｉ2Ｏ量が不充分となるため、ＬｉＡｌＯ2が充分に生成されなくなる。逆に［Ｌｉ2Ｏ］／［ＳｉＯ2］が１．１を超えても、ＬｉＡｌＯ2晶出のための最適範囲から外れるために、ＬｉＡｌＯ2が晶出しにくくなる。
<0.2 ≦ [Li 2 O] / [SiO 2 ] ≦ 1.1>
The mass ratio [Li 2 O] / [SiO 2 ] is 0.2 or more, preferably 0.3 or more, more preferably 0.4 or more, 1.1 or less, preferably 1.0 or less, more preferably Is 0.9 or less. When [Li 2 O] / [SiO 2 ] is less than 0.2, the amount of Li 2 O becomes insufficient, so that LiAlO 2 is not sufficiently generated. On the other hand, even if [Li 2 O] / [SiO 2 ] exceeds 1.1, it is out of the optimum range for LiAlO 2 crystallization, so that LiAlO 2 is difficult to crystallize.
本発明のモールドパウダー（溶融スラグ）の凝固温度は、好ましくは９５０〜１２００℃、より好ましくは１０００〜１１５０℃である。凝固温度が９５０℃未満であると、結晶が晶出しにくくなり、緩冷却の効果を充分に発揮させることができないおそれがある。一方、凝固温度が１２００℃を超えると、スラグベアが生成し、スラグベアによる不均一流入のために、ブレークアウトや鋳片表面の割れが生ずる場合がある。 The solidification temperature of the mold powder (molten slag) of the present invention is preferably 950 to 1200 ° C, more preferably 1000 to 1150 ° C. If the solidification temperature is less than 950 ° C., the crystals are difficult to crystallize, and the effect of slow cooling may not be fully exhibited. On the other hand, when the solidification temperature exceeds 1200 ° C., slag bear is generated, and breakout or cracking of the slab surface may occur due to non-uniform inflow by the slag bear.
連続鋳造する鋼の溶存Ａｌ量は、本発明のモールドパウダーの効果を充分に発揮させるために、０．１％以上、好ましくは０．３％以上、より好ましくは０．５％以上であり、２．５％以下、好ましくは２．０％以下、より好ましくは１．７％以下である。ここで鋼の溶存Ａｌ量とは、連続鋳造に用いる溶鋼中に溶けているＡｌの量を表し、この量には、Ａｌ2Ｏ3等の化合物として存在しているＡｌ量は含まれない。 The amount of dissolved Al in continuously cast steel is 0.1% or more, preferably 0.3% or more, more preferably 0.5% or more, in order to sufficiently exert the effect of the mold powder of the present invention. It is 2.5% or less, preferably 2.0% or less, and more preferably 1.7% or less. Here, the amount of dissolved Al in the steel represents the amount of Al dissolved in the molten steel used for continuous casting, and this amount does not include the amount of Al present as a compound such as Al 2 O 3 .
以下、実施例を挙げて本発明をより具体的に説明するが、本発明は以下の実施例によって制限を受けるものではなく、上記・下記の趣旨に適合し得る範囲で適当に変更を加えて実施することも勿論可能であり、それらはいずれも本発明の技術的範囲に包含される。 EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited by the following examples, and appropriate modifications are made within a range that can meet the above and the following purposes. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.
垂直曲げ型連続鋳造機を用いて、１ヒート２４０トンの溶鋼から、Ｃｒ−Ｍｏ添加鋼を鋳造した。この実施例では、以下の表１に示す組成のモールドパウダーと、Ｃ量が０．１８％、Ｓｉ量が０．０４％、Ｍｎ量が２．１％、Ｃｒ、Ｍｏ、ＮｉおよびＰ量が１％以下、溶存Ａｌ量が１．６％であり、残部がＦｅおよび不可避不純物からなる溶鋼とを用いた。連続鋳造におけるモールドサイズは２４０×１２３０ｍｍであり、鋳造速度は１．４ｍ／分である。 Using a vertical bending type continuous casting machine, Cr-Mo added steel was cast from molten steel of 240 tons per heat. In this example, the mold powder having the composition shown in Table 1 below, the amount of C is 0.18%, the amount of Si is 0.04%, the amount of Mn is 2.1%, and the amounts of Cr, Mo, Ni and P are 1% or less, the amount of dissolved Al was 1.6%, and the balance was molten steel consisting of Fe and inevitable impurities. The mold size in continuous casting is 240 × 1230 mm, and the casting speed is 1.4 m / min.
モールドパウダーから得られるスラグフィルム中に存在するＬｉＡｌＯ2、カスピダイン（３ＣａＯ・２ＳｉＯ2・ＣａＦ2）、ダイカルシウムシリケート（２ＣａＯ・ＳｉＯ2）、メイエナイト（１２ＣａＯ・７Ａｌ2Ｏ3）およびゲーレナイト（３ＣａＯ・２ＳｉＯ2・Ａｌ2Ｏ3）の量を調べるために、鋳造終了後に鋳型内からスラグフィルムを採取し、Ｘ線回折（Ｃｕ管球４０ｋＶ、２００ｍＡ）で、それぞれの結晶のＸ線回折強度を測定した。これらのＸ線回折強度の大小を、表２に示す。 LiAlO 2 , cuspidine (3CaO · 2SiO 2 · CaF 2 ), dicalcium silicate (2CaO · SiO 2 ), mayenite (12CaO · 7Al 2 O 3 ) and gelenite (3CaO · 2SiO) present in the slag film obtained from the mold powder In order to investigate the amount of ( 2 · Al 2 O 3 ), a slag film was taken from the mold after the casting was finished, and the X-ray diffraction intensity of each crystal was measured by X-ray diffraction (Cu tube 40 kV, 200 mA). . Table 2 shows the magnitude of these X-ray diffraction intensities.
潤滑性の指針として、モールドパウダー（溶融スラグ）の凝固温度および消費量を算出した。凝固温度（℃）は、溶融スラグの粘度ηおよび温度Ｔから算出した。具体的には振動片法により、昇温しながら溶融スラグの粘度ηを連続的に測定し、粘度ηの対数ｌｏｇηを縦軸に、粘度の測定温度Ｔの逆数１／Ｔを横軸にとったグラフを作成し、このグラフの変曲点に対応する温度Ｔを凝固温度として求めた。消費量（ｋｇ／ｍ2）は、長さ１０ｍの鋳片が鋳造される毎に鋳型内に添加したモールドパウダー量を測定し、その添加量を鋳造された鋳片の表面積で割ることにより求めた。これらの結果を表３に示す。なお表３に示す消費量の値は、鋳造の最トップおよび最ボトム部の鋳造速度低下部分を除いた値の平均値である。 As a guideline for lubricity, the solidification temperature and consumption of mold powder (molten slag) were calculated. The solidification temperature (° C.) was calculated from the viscosity η and temperature T of the molten slag. Specifically, the viscosity η of the molten slag is continuously measured while raising the temperature by the vibrating piece method, the logarithm log η of the viscosity η is taken on the vertical axis, and the reciprocal 1 / T of the viscosity measurement temperature T is taken on the horizontal axis. The temperature T corresponding to the inflection point of this graph was determined as the solidification temperature. The consumption (kg / m 2 ) is obtained by measuring the amount of mold powder added into the mold every time a 10 m long slab is cast, and dividing the added amount by the surface area of the cast slab. It was. These results are shown in Table 3. In addition, the value of the consumption shown in Table 3 is an average value of values excluding the casting speed reduction portions at the top and bottom of the casting.
緩冷却の指針として、鋳型熱流束（ＭＷ／ｍ2）を算出した。鋳型熱流束は、鋳型冷却水の流量と入口出口の温度差とから、鋳型での総抜熱量を求め、これを、鋳型銅板と鋳片との接触面積で割ることにより算出した。熱流束値が１．５ＭＷ／ｍ2以上のものを「強冷却」、１．５ＭＷ／ｍ2未満のものを「緩冷却」と判定した。この結果を表３に示す。 The mold heat flux (MW / m 2 ) was calculated as a guide for slow cooling. The mold heat flux was calculated by obtaining the total heat removal amount in the mold from the flow rate of the mold cooling water and the temperature difference between the inlet and outlet, and dividing this by the contact area between the mold copper plate and the slab. A sample having a heat flux value of 1.5 MW / m 2 or more was determined as “strong cooling”, and a sample having a heat flux value of less than 1.5 MW / m 2 was determined as “slow cooling”. The results are shown in Table 3.
連続鋳造の安定操業の指針として、鋳型銅板に埋設した熱電対を用いて、一定速度で鋳造した一定区間における温度変動（℃）を測定した。この結果を表３に示す。なお連続鋳造では、温度変動が１５℃を超えると、鋳造速度の減速措置、それでも変動が収まらない場合は鋳造停止措置を行う場合がある。 As a guideline for stable operation of continuous casting, the temperature fluctuation (° C.) in a fixed section cast at a constant speed was measured using a thermocouple embedded in a mold copper plate. The results are shown in Table 3. In continuous casting, when the temperature fluctuation exceeds 15 ° C., the casting speed may be reduced, and if the fluctuation still does not stop, the casting stoppage may be taken.
鋳片の表面品質の指針として、凹みおよび割れを評価した。鋳片表面の凹みは、定常状態で鋳造できた部位のスラブを１ヒートから２枚任意に抜き取りし、スラブ広面の表裏面を目視検査して、凹みが認められた部位について凹み深さを測定し、深さが２ｍｍ以上の凹みがあるものを、「凹み有り」と評価した。鋳片表面の割れは、鋳片の広面の表面および裏面を目視観察し、長さ１００ｍｍ以上の割れが１つでも存在するものを、「割れ有り」と評価した。これらの結果を表３に示す。 As an indicator of the surface quality of the slab, dents and cracks were evaluated. As for the dent on the surface of the slab, two slabs of the part that could be cast in a steady state are arbitrarily extracted from one heat, and the front and back surfaces of the wide surface of the slab are visually inspected, and the dent depth is measured at the part where the dent is recognized And the thing with a dent with a depth of 2 mm or more was evaluated as "with a dent". The crack on the surface of the slab was evaluated by visually observing the front and back surfaces of the wide surface of the slab and having one crack having a length of 100 mm or more as “having a crack”. These results are shown in Table 3.
表１〜３の結果から示されるように、本発明の要件を満たすモールドパウダーＮｏ．１〜１０は、そのスラグフィルム中にカスピダインが形成されなくとも、緩冷却を実現でき、凹みや割れの無い表面品質に優れた鋳片を製造することができる。この緩冷却は、スラグフィルム中のＬｉＡｌＯ2により達成されると考えられる。またモールドパウダーＮｏ．１〜１０は、その凝固温度が適正範囲内にあり、適正な潤滑性を有していることが分かる。またこれらを用いた連続鋳造では、温度変動が少なく、安定に操業することができる。 As shown from the results in Tables 1 to 3, the mold powder No. 1 satisfying the requirements of the present invention. Nos. 1 to 10 can realize slow cooling without producing caspidyne in the slag film, and can produce a slab excellent in surface quality free from dents and cracks. This slow cooling is believed to be achieved by LiAlO 2 in the slag film. Mold powder No. As for 1-10, it turns out that the coagulation | solidification temperature exists in an appropriate range, and has appropriate lubricity. Moreover, in continuous casting using these, there is little temperature fluctuation and it can operate stably.
これらに対して、本発明の要件を満たさないモールドパウダーＮｏ．１１〜２３を用いた連続鋳造では、以下に記載する理由により、凹みや割れの有る鋳片しか得られなかった。
Ｎｏ．１１は、ＭｇＯ量が少なく、粗大な結晶が晶出したため、抜熱速度にバラツキが生じ、鋳片の凹みや割れが発生した。
Ｎｏ．１２は、ＭｇＯ量が多く、メイエナイトなどが優先的に晶出したため、抜熱速度にバラツキが生じ、鋳片の凹みや割れが発生した。
On the other hand, mold powder No. which does not satisfy the requirements of the present invention. In continuous casting using 11 to 23, only slabs with dents and cracks were obtained for the reasons described below.
No. In No. 11, since the amount of MgO was small and coarse crystals were crystallized, the heat extraction speed varied, and slabs and cracks were generated.
No. In No. 12, since the amount of MgO was large and mayenite crystallized preferentially, the heat extraction rate varied, and the slab was indented or cracked.
Ｎｏ．１３は、ＳｉＯ2量が少ないため、スラグベアが多量に生成し、鋳片の凹みや割れが発生した。
Ｎｏ．１４は、Ｌｉ2Ｏ量およびＬｉ2Ｏ／ＳｉＯ2が大きいため、溶融スラグの粘度が低下したと考えられる。そのため過剰流入および脈動が生じ、温度変動が大きくなった。また適正な潤滑性が確保されずに、鋳片の凹みや割れが発生した。
Ｎｏ．１５は、Ｌｉ2Ｏ量およびＬｉ2Ｏ／ＳｉＯ2が小さいため、溶融スラグの凝固温度および粘度が高くなって適正な潤滑性が確保されず、またメイエナイトやダイカルシウムシリケートが多く晶出して抜熱速度にバラツキが生じたために、鋳片の凹みや割れが発生した。
No. In No. 13, since the amount of SiO 2 was small, a large amount of slag bear was generated, and dents and cracks in the slab were generated.
No. 14, since Li 2 O amount and Li 2 O / SiO 2 is larger, considered the viscosity of the molten slag is lowered. As a result, excessive inflow and pulsation occurred, and the temperature fluctuation increased. Moreover, dents and cracks in the slab were generated without ensuring proper lubricity.
No. 15, since Li 2 O amount and Li 2 O / SiO 2 is small, not ensured proper lubrication property becomes high solidification temperature and viscosity of the molten slag, also Meienaito and Dicalcium silicate most crystallized disconnect Due to the variation in the heat speed, the slab was dented or cracked.
Ｎｏ．１６は、Ｆ量が少なく、溶融スラグの粘度が上昇して、適正な潤滑性が確保できず、鋳片の凹みや割れが発生した。
Ｎｏ．１７は、Ｆ量が多くて、ＬｉＡｌＯ2が充分に晶出されず、抜熱速度にバラツキが生じ、鋳片の凹みや割れが発生した。
Ｎｏ．１８は、塩基度［Ｔ−ＣａＯ］／［ＳｉＯ2］が低く、粗大なゲーレナイトが多く生じたため、抜熱速度にバラツキが生じ、鋳片の凹みや割れが発生した。
No. In No. 16, the amount of F was small, the viscosity of the molten slag increased, and proper lubricity could not be ensured, and slabs and cracks occurred.
No. In No. 17, the amount of F was large, LiAlO 2 was not sufficiently crystallized, the heat extraction speed varied, and the slab was dented or cracked.
No. No. 18 had a low basicity [T-CaO] / [SiO 2 ] and a large amount of coarse gehlenite was generated, resulting in variations in the heat removal rate, and indentations and cracks in the slab.
Ｎｏ．１９は、Ｌｉ2Ｏ量が少ないため、凝固温度が高くなりすぎて、適正な潤滑性が確保できず、鋳片の割れが発生した。
Ｎｏ．２０は、Ｌｉ2Ｏが多すぎるため、充分な量のＬｉＡｌＯ2が晶出されず、抜熱速度にバラツキが生じて、鋳片の割れが発生した。
No. No. 19 had a small amount of Li 2 O, so the solidification temperature was too high, and proper lubricity could not be ensured, resulting in cracking of the slab.
No. In No. 20, since there was too much Li 2 O, a sufficient amount of LiAlO 2 was not crystallized, the heat removal rate varied, and the slab cracked.
Ｎｏ．２１は、Ｃ量が多くて溶融速度が不充分であるため、スラグフィルムが充分に形成されない部分が生じ、その部分が急冷されて、割れが発生した。
Ｎｏ．２２は、Ｃ量が少なくて溶融速度が増大したため、流入過多および不均一流入が生じ、鋳片の凹みや割れが発生した。
Ｎｏ．２３は、塩基度［Ｔ−ＣａＯ］／［ＳｉＯ2］が低く、粗大なゲーレナイトが多く生じたため、抜熱速度のバラツキが生じ、鋳片の割れが発生した。またＮａ2Ｏも存在するため、Ｎａ−Ａｌ−Ｏ結晶が不均一に晶出し、これも抜熱速度のバラツキに悪影響を及ぼしたと考えられる。
No. In No. 21, since the amount of C was large and the melting rate was insufficient, a portion where the slag film was not sufficiently formed was generated, and the portion was rapidly cooled to cause cracks.
No. In No. 22, since the amount of C was small and the melting rate was increased, excessive inflow and non-uniform inflow occurred, resulting in dents and cracks in the slab.
No. No. 23 had a low basicity [T-CaO] / [SiO 2 ] and a large amount of coarse gehlenite was generated, resulting in variations in heat removal rate and cracking of the slab. Further, since Na 2 O is also present, Na—Al—O crystals are crystallized non-uniformly, which is considered to have adversely affected the variation in the heat extraction rate.
Claims (1)
Ｔ−ＣａＯ：３５〜５５％（質量％の意味、以下同じ）、
ＳｉＯ2：１０〜３０％、
Ａｌ2Ｏ3：４．０％以下（０％を含まない）、
ＭｇＯ：０．２〜０．９％、
Ｌｉ2Ｏ：７〜１３％、
Ｆ：７〜１３％、
Ｃ：１０．５〜１４％、
および不可避不純物からなり、
下記式（１）および（２）：
１．６≦［Ｔ−ＣａＯ］／［ＳｉＯ2］≦５ … （１）
０．２≦［Ｌｉ2Ｏ］／［ＳｉＯ2］≦１．１ … （２）
〔式中、［Ｔ−ＣａＯ］、［ＳｉＯ2］および［Ｌｉ2Ｏ］は、それぞれ、Ｔ−ＣａＯ、ＳｉＯ2およびＬｉ2Ｏのモールドパウダー中の含有量（質量％）を表す。〕
を満たすことを特徴とする、溶存Ａｌ量が０．１％以上である鋼を連続鋳造するためのモールドパウダー。 Mold powder used for continuous casting of steel,
T-CaO: 35 to 55% (meaning mass%, the same shall apply hereinafter),
SiO 2: 10~30%,
Al 2 O 3 : 4.0% or less (excluding 0%),
MgO: 0.2 to 0.9 %,
Li 2 O: 7-13%
F: 7-13%
C: 10.5-14%
And consisting of inevitable impurities
The following formulas (1) and (2):
1.6 ≦ [T-CaO] / [SiO 2 ] ≦ 5 (1)
0.2 ≦ [Li 2 O] / [SiO 2 ] ≦ 1.1 (2)
[In the formula, [T-CaO], [SiO 2 ] and [Li 2 O] represent the contents (mass%) of T-CaO, SiO 2 and Li 2 O in the mold powder, respectively. ]
A mold powder for continuously casting steel having a dissolved Al content of 0.1% or more.
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| JP2006120786A JP4646849B2 (en) | 2006-04-25 | 2006-04-25 | Mold powder for continuous casting of high aluminum steel |
| GB0821413A GB2450855B (en) | 2006-04-25 | 2007-04-23 | Method of continuous casting of high-aluminium steel and mold powder |
| CN2007800230321A CN101472691B (en) | 2006-04-25 | 2007-04-23 | Method of continuous casting of high-aluminum steel and mold powder |
| PCT/JP2007/058751 WO2007125871A1 (en) | 2006-04-25 | 2007-04-23 | Method of continuous casting of high-aluminum steel and mold powder |
| KR1020087026242A KR101057950B1 (en) | 2006-04-25 | 2007-04-23 | Continuous casting method and mold powder of high aluminum steel |
| US12/297,984 US8146649B2 (en) | 2006-04-25 | 2007-04-23 | Method of continuous casting of high-aluminum steel and mold powder |
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| JP5136994B2 (en) * | 2009-07-07 | 2013-02-06 | 新日鐵住金株式会社 | Continuous casting method of steel using mold flux |
| CN102389955B (en) * | 2011-11-26 | 2013-08-28 | 重庆大学 | Crystallizer casting powder for high-aluminum steel continuous casting |
| CN102756103B (en) * | 2012-08-10 | 2014-10-08 | 重庆大学 | Crystallizer casting powder for high-crystallinity high-lubricity continuous casting |
| CN103317112B (en) * | 2013-05-31 | 2015-06-10 | 西峡县恒基冶材有限公司 | High-alkalinity crystallizer casting powder for peritectic steel continuous casting and process for preparing high-alkalinity crystallizer casting powder |
| ES2700353T3 (en) * | 2014-06-10 | 2019-02-15 | Nippon Steel & Sumitomo Metal Corp | Method of continuous casting of sub-peritectic steel containing Ti using flux for mold |
| KR20190028577A (en) * | 2014-09-11 | 2019-03-18 | 신닛테츠스미킨 카부시키카이샤 | Mold flux for continuous casting of steel |
| JP6169648B2 (en) * | 2015-06-29 | 2017-07-26 | 品川リフラクトリーズ株式会社 | Mold powder for continuous casting of steel and continuous casting method of steel |
| CA3002344A1 (en) | 2015-11-05 | 2017-05-11 | Nippon Steel & Sumitomo Metal Corporation | Mold flux for continuous casting and continuous casting method |
| JP6674093B2 (en) * | 2016-03-24 | 2020-04-01 | 品川リフラクトリーズ株式会社 | Mold powder for continuous casting of steel and continuous casting method |
| CN108127094B (en) * | 2018-01-11 | 2019-05-31 | 重庆大学 | A kind of non-reacted covering slag of high titanium steel |
| CN109877287B (en) * | 2019-03-05 | 2020-05-08 | 北京科技大学 | Method for controlling fine cracks on surface of sub-peritectic steel bar |
| KR102629377B1 (en) * | 2019-06-04 | 2024-01-24 | 제이에프이 스틸 가부시키가이샤 | Mold powder and continuous casting method for continuous casting of Al-containing apostatic steel |
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| JP2003181606A (en) * | 2001-12-12 | 2003-07-02 | Nippon Steel Metal Prod Co Ltd | MOLD FLUX FOR CONTINUOUSLY CASTING STEEL HAVING HIGH Al, Y AND REM CONTENTS |
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| LAPS | Cancellation because of no payment of annual fees |