JP2004074242A - Refractory for continuous casting and continuous casting method using this refractory - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refractory for continuous casting with which even in the case of being much suspended amount of alumina during casting for long time or in molten steel when the aluminum-killed steel is cast, a sufficient alumina-deposition preventive effect can be obtained. <P>SOLUTION: In the refractory for continuous casting, in which CaO-MgO base refractory containing CaO as a mineral phase is deposited in at least a part of the surface contacting with molten steel and integrally formed with a main body part, in the main body part, MgO-C base material having 0 to 15 mass% the total content of Al<SB>2</SB>O<SB>3</SB>and SiO<SB>2</SB>is applied. In this way, the alumina-deposition preventive function can be held for long time by restraining the reaction of CaO component and main body part in the inner layer part or the outer layer part material with Al<SB>2</SB>O<SB>3</SB>and SiO<SB>2</SB>used for strength-up and improving spalling-resistance. <P>COPYRIGHT: (C)2004,JPO

Description

これらの配合物Ａを成形圧１０００ｋｇ／ｃｍ^２でＣＩＰによって成形し、最高１０００℃で還元焼成して、図１に示す浸漬ノズル１０を作製した。
【００２２】
本体１の配合物の構成割合は、表１に示す通りである。パウダーライン部２は、黒鉛１０質量％とジルコニア９０質量％とからなるＺｒＯ_２−Ｃ質の配合物にフェノールレジンを適量添加して配合物を作製したものである。　内孔体３の配合物Ａは、ＣａＯ−ＭｇＯクリンカーの粒径１〜０．５ｍｍの粒子を４０質量％と、粒径０．２〜０．５ｍｍ未満の粒子を１５質量％と、０．２ｍｍ未満の粒子を２０質量％と、黒鉛の粒径０．５ｍｍ以下の粒子を２５質量％とからなる配合物にフェノールレジンを適量添加した作製したものである。　内孔部３を形成するＣａＯ−ＭｇＯ系材質の厚さは、この実施例では５ｍｍとしたが、３〜１５ｍｍ程度あればよい。
【００２３】
図１に示す浸漬ノズルを、アルミキルド鋼の鋳造に適用して、内孔体３の内面へのアルミナ付着速度を算出し、実施例１の付着速度を１００とした指数で表１に示す。数宇が大きいほど付着速度が大きく好ましくない。鋳造条件は、鍋容量が２５０ｔｏｎ、ＴＤ容量が４５ｔｏｎ、鋳片の引き抜き速度は１．０〜１．３ｍ／分、鋳造時間は４５０〜５００分であった。
【００２４】
この結果から、Ａｌ_２Ｏ_３とＳｉＯ_２の合量は少ないほど付着が少なく、本体用ＭｇＯ−Ｃ材質中のＡ１_２Ｏ_３とＳｉＯ_２の合量は１５質量％以下であることが好ましいことが判る。　その合量が１５質量％を越えると付着速度が急激に増加し、鋳片の品質上好ましくない。
【００２５】
実施例　ＩＩ
この実施例は、本発明を図２に示す本体１の内孔体３からなる上ノズル２０に適用した例を示す。
【００２６】
表２は、ＣａＯ−ＭｇＯ系内孔体３の材質に対し、本体１としてＭｇＯ−Ｃ系材質を適用した場合の本体材質中のＡｌ_２Ｏ_３とＳｉＯ_２の影響をアルミナおよびシリカの量を変化させて調査したものである。
【００２７】
表２に示す内孔体の配合Ｂは、実施例６〜１０と、比較例４〜６の何れの例も、ＣａＯ−ＭｇＯクリンカーの粒径３〜１ｍｍを３５質量％、１〜０．２ｍｍを２５質量％、０．２ｍｍ未満を４０質量％、フェノールレジンを適量添加したものである。また、本体の配合物は、同表の本体配合割合に示す組成を有する。
【００２８】
【表２】

図２に示す上ノズル２０を、表２に示す内孔体の配合Ｂと本体配合物を成形圧１０００ｋｇ／ｃｍ^２でＣＩＰにて成形し、最高１０００℃で還元焼成して上ノズルを作製した。内孔体３のＣａＯ−ＭｇＯ系材質は、本例では厚さ５ｍｍとしたが、３〜１５ｍｍ程度あればよい。
【００２９】
この上ノズル２０を、アルミキルド鋼の鋳造に適用して、内孔体材質へのアルミナ付着速度を算出し、実施例６の付着速度を１００とした指数を表２に示す。数字が大きいほど付着速度が大きく好ましくない。　鋳造条件は、表１に示す実施例Ｉの場合と同様である。
【００３０】
この例の場合も、実施例１の表１に示す結果と同様に、Ａｌ_２Ｏ_３とＳｉＯ_２の合量は少ないほど付着が少ない。とくに、その合量が１５質量％までは付着速度が極めて少なく、１５質量％を超えると急激に増加し、鋳片の品質上好ましくない。従って、本体用ＭｇＯ−Ｃ材質中のＡｌ_２Ｏ_３とＳｉＯ_２の合量は１５質量％以下が良いことがわかる。
【００３１】
【発明の効果】
本発明によれば、ＭｇＯ−Ｃ系材質の本体部分に含まれるＡｌ_２Ｏ_３やＳｉＯ_２成分量を、強度アップや耐スポール性改善のために必要な最低限に制限することで、ＣａＯ−ＭｇＯ系耐火物によるアルミナ付着防止効果を長時間継続して維持することができ、これによって、長期にわたって高品質の鋼材を得ることが可能となった。
【図面の簡単な説明】
【図１】本発明を適用した浸漬ノズルの構成図を示す。
【図２】本発明を適用した上ノズルの構成図を示す。
【符号の説明】
１　　　本体部分
２　　　パウダーライン部分
３　　　内孔体部分
１０　　浸漬ノズル
２０　　上ノズル[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a refractory and a continuous casting method for preventing adhesion of alumina during continuous casting of molten steel.
[0002]
[Prior art]
In recent years, aluminum deoxidized steel, so-called aluminum-killed steel, which is cast as a high-grade steel such as a thin plate, is required to adhere to stricter quality requirements. Much effort has been put into preventing this. Alumina adhering to the nozzle coalesces to form large inclusions, which are taken into the slab together with the molten steel flow and become defects in the slab, thereby deteriorating the quality.
[0003]
As an example of the countermeasure, there is a method of physically preventing adhesion of alumina by blowing argon gas into molten steel from the inner surface of the nozzle. However, in this method, if the amount of argon gas blown is too large, bubbles are taken into the slab and become pinholes in the slab to cause defects. Therefore, this method must restrict the amount of gas blown in order to prevent the occurrence of defects in the slab, and cannot be a sufficient measure.
[0004]
As another example of the countermeasure, CaO is contained in a refractory material for continuous casting constituting a nozzle or the like used in continuous casting, and a low melt is produced by reacting the adhered alumina with CaO in the refractory material. There is also a method in which the refractory material has an alumina adhesion preventing function for preventing the adhesion of alumina to the refractory material. For example, Japanese Patent Application Laid-Open No. 61-53150 discloses that the surface layer of a runner is formed from 20 to 97% by mass of calcareous material and 3 to 80% of carbonaceous material, and the outer layer is formed of 50 to 95% by mass of alumina material and 5 to 95% by mass. Nozzles for casting molten steel of ~ 50% carbonaceous are disclosed. However, such a nozzle has a problem that a sufficient effect of preventing adhesion of alumina cannot be obtained when casting for a long time or when the amount of alumina suspended in molten steel is large.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a refractory for continuous casting, which can provide a sufficient effect of preventing alumina from being adhered, even when casting aluminum killed steel for a long time or when the amount of suspended alumina in molten steel is large. Is to do.
[0006]
[Means for Solving the Problems]
The present invention, as a result of examining the cause of the adhesion of alumina to the molten steel casting nozzle manufactured by integral molding, not only the adhesion of alumina from the molten steel in the calcareous inner layer during use, but also the alumina of the outer layer -Investigate that alumina is diffused from carbonaceous refractories, and when casting for a long time or when the amount of alumina suspended in molten steel is large, the alumina absorption capacity in the inner layer reaches the limit, and alumina adheres. This is based on the finding that occurs.
[0007]
Further, as shown in Example 10 of JP-A-61-53150, when silica is contained in the outer layer material, the silica diffuses into the inner layer to form a compound with CaO. In addition, it was also found that the ability of CaO to absorb alumina was reduced.
[0008]
In order to prevent such a decrease in the ability of the alumina to prevent adhesion of alumina due to CaO and to reduce the amount of the material on the outer layer side of the nozzle to be diffused to the inner layer side, the content of the diffused alumina and silica components is reduced. It was completed with the recognition that it needed to be restricted.
[0009]
That is, the present invention is a refractory for continuous casting, in which a CaO-MgO-based refractory containing CaO as a mineral phase is disposed on at least a part of a surface in contact with molten steel, and is integrally formed with a main body. the total amount of _A1 2 _{O 3} and SiO ₂ is equal to or applying the material of 15 wt% or less of MgO-C system parts.
[0010]
If the CaO-MgO-based refractory is applied to the nozzle body (except for the powder line portion in the case of the immersion nozzle), a decrease in strength when digested adversely affects the entire nozzle. Therefore, in the present invention, it is a reasonable material arrangement to apply only to the surface where the CaO-MgO-based refractory comes into contact with molten steel.
[0011]
When a CaO-MgO-based refractory containing CaO as a mineral phase is applied to the surface in contact with the molten steel, it is most preferable to apply an MgO-C-based material as the main body material. Since MgO does not diffuse into the CaO-MgO-based refractory, the presence of MgO in the CaO-MgO-based refractory does not hinder the ability of CaO to absorb alumina.
[0012]
Further, carbon in the MgO-C material is indispensable for imparting spall resistance to the refractory. As the magnesia aggregate in the MgO-C material of the main body, 75 to 95% by mass of synthetic or natural material such as electrofused magnesia and sintered magnesia, and 5 to 25% by mass of carbon material such as artificial or natural graphite Within the range, known ones conventionally used can be applied.
[0013]
In the MgO-C material, alumina or fused silica is preferably used in place of magnesia or a part of carbon aggregate in order to improve strength and spall resistance. It is necessary that the used amount be 15% by mass or less as a total amount of A1 ₂ O ₃ + SiO ₂ . It exceeds 15 wt%, the capacity to absorb alumina in the molten steel by _Al 2 _{O 3} or SiO ₂ which is diffused from the body material into CaO-MgO based refractory is to significantly reduced. A1 ₂ O ₃ and SiO ₂ in composition ratio is not particularly limited, it is also possible to either a 15 wt%. In order to improve the strength of the MgO-C material, Al ₂ O ₃ + SiO ₂ may be added in the case where Al, Si, an Al-Si alloy, or the like is added instead of the oxide in order to improve the strength. To 15% by mass or less.
[0014]
Examples of CaO-MgO refractories containing CaO as a mineral phase include dolomite, dolomite carbon, CaO dolomite, CaO dolomite carbon, magnesia dolomite, magnesia dolomite carbon, and the like. Is mentioned.
[0015]
The CaO-MgO-based refractory containing CaO as a mineral phase is preferably disposed on all surfaces in contact with the molten steel, but may be disposed only on a part of the surfaces. In particular, it is important to apply it to a portion where alumina adheres frequently. The thickness is not particularly limited, but if it is too thin, the ability to absorb alumina in the molten steel is insufficient, so it is preferably at least 3 mm, more preferably at least 5 mm.
[0016]
The present invention is applicable to refractories for continuous casting such as immersion nozzles, upper nozzles, lower nozzles, sliding nozzles, long nozzles, stopper heads, long stoppers and the like. And the quality of the slab is improved.
[0017]
Further, the present invention is suitable for casting not only aluminum-killed steel but also aluminum-silicon-killed steel and titanium-aluminum-killed steel using aluminum in combination with another deoxidizing agent.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the present invention will be described with reference to examples.
[0019]
Example I
This embodiment shows an example in which the present invention is applied to an immersion nozzle 10 including a main body 1, a powder line 2, and an inner hole 3 shown in FIG.
[0020]
Table 1, carried out CaO-MgO-based as the material A of the inner bore of the immersion nozzle, the effect of _A1 2 _{O 3} and SiO ₂ in an amount in the body material of the application of the MgO-C based material to the main body case Investigation results are shown as Formulations A shown in Nos. 1 to 5 and Comparative Examples 1 to 3.
[0021]
[Table 1]

These formulations A were molded by CIP at a molding pressure of 1000 kg / cm ² , and reduced and fired at a maximum of 1000 ° C. to produce the immersion nozzle 10 shown in FIG.
[0022]
The composition ratio of the composition of the main body 1 is as shown in Table 1. The powder line portion 2 was prepared by adding an appropriate amount of phenolic resin to a ZrO ₂ -C-based compound composed of 10% by mass of graphite and 90% by mass of zirconia. In the composition A of the inner pore body 3, 40% by mass of particles having a particle size of 1 to 0.5 mm and 15% by mass of particles having a particle size of less than 0.2 to 0.5 mm were obtained. It was prepared by adding an appropriate amount of phenolic resin to a blend of 20% by mass of particles of less than 2 mm and 25% by mass of particles of graphite having a particle size of 0.5 mm or less. The thickness of the CaO-MgO-based material forming the inner hole 3 is 5 mm in this embodiment, but may be about 3 to 15 mm.
[0023]
The immersion nozzle shown in FIG. 1 was applied to the casting of aluminum-killed steel, and the alumina deposition rate on the inner surface of the inner hole body 3 was calculated. The larger the number, the higher the adhesion speed, which is not preferable. The casting conditions were a pot capacity of 250 tons, a TD capacity of 45 tons, a casting speed of 1.0 to 1.3 m / min, and a casting time of 450 to 500 minutes.
[0024]
This result, _Al 2 _{O 3} and the total amount of SiO ₂ is less deposited as small, it is preferably _A1 2 _{O 3} and the total amount of SiO ₂ in the MgO-C material for the body is less than 15 wt% I understand. If the total amount exceeds 15% by mass, the deposition rate sharply increases, which is not preferable in terms of the quality of the slab.
[0025]
Example II
This embodiment shows an example in which the present invention is applied to an upper nozzle 20 including an inner hole 3 of a main body 1 shown in FIG.
[0026]
Table 2 shows the effect of Al ₂ O ₃ and SiO ₂ in the body material when the MgO—C material is used as the body 1 with respect to the material of the CaO—MgO inner bore 3, and the amounts of alumina and silica. It was changed and investigated.
[0027]
As for the composition B of the inner body shown in Table 2, in Examples 6 to 10 and Comparative Examples 4 to 6, the particle diameter of CaO-MgO clinker was 3 to 1 mm at 35% by mass and 1 to 0.2 mm. , 25% by mass, 40% by mass less than 0.2 mm, and an appropriate amount of phenol resin. The composition of the main body has a composition shown in the main body mixing ratio in the same table.
[0028]
[Table 2]

The upper nozzle 20 shown in FIG. 2 was formed by molding the composition B of the inner body shown in Table 2 and the body composition by CIP at a molding pressure of 1000 kg / cm ² , and reducing and firing at a maximum of 1000 ° C. to produce an upper nozzle. . The CaO—MgO-based material of the inner hole body 3 is 5 mm in thickness in this example, but may be about 3 to 15 mm.
[0029]
The upper nozzle 20 was applied to the casting of aluminum-killed steel, and the alumina deposition rate on the material of the inner hole body was calculated. The larger the number, the higher the adhesion speed, which is not preferable. The casting conditions were the same as in Example I shown in Table 1.
[0030]
Also in the case of this example, similar to the results shown in Table 1 of Example 1, the smaller the total amount of Al ₂ O ₃ and SiO ₂ , the less the adhesion. In particular, when the total amount is up to 15% by mass, the adhesion speed is extremely low, and when it exceeds 15% by mass, the adhesion speed is sharply increased, which is not preferable in terms of the quality of the slab. Accordingly, it is understood that the total amount of Al ₂ O ₃ and SiO _{2 in} the MgO—C material for the main body is preferably 15% by mass or less.
[0031]
【The invention's effect】
According to the present invention, the amount of Al ₂ O ₃ and SiO ₂ components contained in the main body of the MgO—C-based material is restricted to the minimum necessary for increasing the strength and improving the spall resistance. The effect of preventing the adhesion of alumina by the MgO-based refractory can be continuously maintained for a long time, thereby making it possible to obtain a high-quality steel material for a long time.
[Brief description of the drawings]
FIG. 1 shows a configuration diagram of an immersion nozzle to which the present invention is applied.
FIG. 2 shows a configuration diagram of an upper nozzle to which the present invention is applied.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Main body part 2 Powder line part 3 Inner body part 10 Immersion nozzle 20 Upper nozzle

Claims (2)

A CaO-MgO-based refractory containing CaO as a mineral phase is disposed on at least a part of a surface in contact with molten steel, and in a refractory for continuous casting integrally formed with a main body,
_A1 2 _{O 3} and continuous casting refractories content was applied MgO-C based material of 0-15 wt% of the total of SiO ₂ to the main body portion. A continuous casting method using the refractory for continuous casting according to claim 1 for casting aluminum killed steel.

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