JP5134516B2 - Continuous casting nozzle - Google Patents

Description

  The present invention has a nozzle used for continuous casting of molten steel, in particular, a refractory for a continuous casting nozzle composed of a tubular refractory structure having an inner hole through which molten steel passes in the axial direction, and the refractory thereof. The present invention relates to a nozzle for continuous casting.

  In the present invention, the term “tubular” refers to all shapes having an inner hole in the axial direction, and the cross-sectional shape in the direction orthogonal to the axial direction is not limited. That is, the cross-sectional shape in the direction orthogonal to the axial direction is not limited to a circle, and may be an elliptical shape, a rectangle, a polygon, or the like.

  In recent years, there has been an increase in non-metallic inclusions in molten steel such as alumina accompanying the upgrading of steel, etc., and adhesion of inclusions centering on alumina on the inner surface of nozzles for continuous casting or blockage of inner holes, etc. This is one of the major factors that determine the life of a continuous casting nozzle.

Under such circumstances, there is an increasing demand for a continuous casting nozzle with high durability by reducing adhesion or blockage of non-metallic inclusions to the inner hole surface. Therefore, various proposals have been made regarding the refractory layer on the inner surface of the continuous casting nozzle in order to reduce or prevent the inclusion of inclusion components such as Al ₂ O ₃ from the molten steel on the inner surface. ing.

For example, in Patent Document 1, at least the inner hole part of the nozzle and / or the part in contact with the molten steel does not contain a carbon component, SiO ₂ is 5 to 10% by weight, and Al ₂ O ₃ is 90 to 95% by weight. There is shown a continuous casting nozzle composed of an Al ₂ O ₃ —SiO ₂ based refractory material having a main mineral phase of mullite and corundum and / or β-alumina.

However, such a refractory material that does not contain a carbon component has extremely low resistance to thermal shock, and in particular, there is a high risk of destruction due to thermal shock such as at the start of molten steel injection. Moreover, even if it does not contain a carbon component, such an Al ₂ O ₃ —SiO ₂ refractory material cannot sufficiently suppress the inclusion of inclusions centering on alumina or blockage of inner holes.

  Therefore, the material of the refractory layer on the inner hole surface side contains a large amount of CaO component that easily reacts with inclusions centering on alumina to generate a low melt, Many proposals have been made to suppress occlusion and the like.

  For example, Patent Document 2 shows that a lining layer of a composition containing 40 to 90% by weight of CaO, 0 to 50% by weight of MgO and 0 to 20% by weight of C is disposed in the inner hole of the nozzle. Yes. However, in such a lining layer, especially when the content of CaO is large, CaO exists as a free lime that is very easily hydrated. . Further, such a composition such as CaO has a very large thermal expansion property, and the outer main body layer, that is, the continuous casting nozzle itself is destroyed by the thermal expansion of the lining layer by this composition.

For such problems of CaO, for example, Patent Document 3 contains 16 to 35% by weight of CaO, 20 to 95% by weight of calcium zirconate-based clinker mainly composed of CaZrO ₃ , 5 to 50% by weight of graphite, etc. A ZrO ₂ —CaO-containing nozzle for continuous casting made of zirconia clinker containing 3 to 35% by weight of CaO (containing CubicZrO ₂ and CaZrO ₃ as a mineral composition) is 40 to 85%. %, Graphite, 10-30% by weight, silica 1-15% by weight, and magnesia 1-15% by weight. A nozzle is shown. In these materials, CaO is not present as a free lime, so that it is present as a mineral having a crystal structure with ZrO ₂ or the like.

However, a refractory composed of such components has a small effect for reducing or preventing the inclusion of inclusion components such as Al ₂ O _{3 on} the inner surface in an actual continuous casting operation, and is sufficient for continuous casting. The service life of the nozzle cannot be secured. In addition, although the digestion problem can be solved, the thermal expansibility can be lowered to the same level as the alumina-graphite refractory of the main body of a continuous casting nozzle located outside the inner hole side layer. However, in a structure in which these are integrally installed, the continuous casting nozzle cannot be sufficiently prevented from being damaged by thermal shock.

  In order to install such a layer having a high thermal expansion property on the inner hole side, it is necessary to improve the thermal shock resistance on the structural surface of the continuous casting nozzle. For example, in Patent Document 5, a base material nozzle is externally mounted on a CaO nozzle made of a refractory having a CaO content of 70% by weight or more and an apparent porosity of 50% or less, and an inner hole side CaO nozzle and an outer base material nozzle are provided. A casting nozzle is shown in which a gap corresponding to the thermal expansion allowance of the CaO nozzle is provided therebetween.

  However, such a special structure such as providing a gap between the inner hole side layer and the outer peripheral side layer has a problem that it becomes difficult to provide a continuous casting operation as a normal integral molded body. . In addition, there is a problem that the risk of causing displacement or peeling of the inner hole side layer or damage or destruction of the continuous casting nozzle is increased.

As described above, when a CaO-based refractory is arranged on the inner hole side, it often has many difficult problems such as structural design, manufacturing, handling, and the like. There are still many unresolved issues in the industry, such as requiring
JP-A-10-128507 Japanese Patent Laid-Open No. 01-289549 Japanese Patent Publication No. 02-023494 Japanese Patent Publication No. 03-014540 Japanese Patent Application Laid-Open No. 07-232249

The problem to be solved by the present invention is to prevent nozzle clogging in a continuous casting nozzle made of a steel grade that is particularly susceptible to nozzle clogging, such as aluminum killed steel, and more specifically, as a monolithic structure. For refractory and continuous casting that can be used in casting operations, solves problems inherent to CaO-containing refractories that cause digestion and high expansion, and has little inclusion of inclusions such as Al ₂ O ₃ It is to provide a nozzle.

The continuous casting nozzle according to one aspect of the present invention, the one or two out of SiO ₂ and B ₂ O _3, CaO and _R 2 O: Total (R Na, K, Li) and one or two of in 8.0 wt% to 1.0 wt% or less, including less 34.5 wt% 20.0 wt% carbon, the balance being Al ₂ O ₃ except for unavoidable components in the raw material or manufacturing, and, A refractory having a mass ratio (CaO + R ₂ O) / (SiO ₂ + B ₂ O ₃ ) of 0.5 or more and 2.0 or less is arranged on a part or all of the surface in contact with the molten steel. ). Moreover, the nozzle for continuous casting according to another aspect of the present invention is one or two of SiO ₂ and B ₂ O ₃ and one or two of CaO and R ₂ O (R: Na, K, Li). And 1.0 to 8.0% by mass in total, 20.0 to 34.5% by mass of carbon , 9% by mass or less of one or two of SiC and ZrO ₂ , and the balance A refractory consisting of Al ₂ O ₃ excluding inevitable components in the raw material or production and having a mass ratio (CaO + R ₂ O) / (SiO ₂ + B ₂ O ₃ ) of 0.5 or more and 2.0 or less. It arrange | positions to a part or all of the surface which contact | connects molten steel (Claim 2).

Here, “R” of “R ₂ O” is Na, K, and Li as described above, and thus “R ₂ O” is Na ₂ O, K ₂ O, and Li ₂ O. In the present invention, the chemical component value is based on the measured value of the sample after heat treatment in a non-oxidizing atmosphere at 1000 ° C.

In other words, the refractory of the present invention is 1.0% by mass or more and 8.0% in total of the (SiO ₂ + B ₂ O ₃ ) component as the glass forming oxide and the (CaO + R ₂ O) component as the glass modifying oxide. The mass ratio of glass modified oxide / glass forming oxide, that is, the mass ratio of (CaO + R ₂ O) / (SiO ₂ + B ₂ O ₃ ) is 0.5 or more and 2.0 or less. hints 20.0 mass% or more 34.5% by mass or less, the balance being mainly composed of _Al 2 _{O 3.}

Thus, in the present invention, an appropriate vitrification component (referred to as a generic term for glass-forming oxides and glass-modified oxides) is contained inside the refractory matrix. As a result, a molten glass phase in which SiO ₂ and B ₂ O ₃ are glass-forming oxides and CaO and R ₂ O are glass-modified oxides is formed at the molten steel and refractory interface. The molten film-like glass phase formed on the working surface maintaining an appropriate viscosity at the temperature of the molten steel (about 1500 ° C.) is composed of Al ₂ O _{3 and the} like from the molten steel by the smoothing action and protective film action of the working surface. Inclusion particles are allowed to flow into the molten steel without being fixed to the refractory.

More specifically, by including the above-mentioned vitrification component in the refractory, the interface between the refractory and the molten steel is caused by the reaction between the nonmetallic inclusions (Al ₂ O ₃ ) present in the molten steel and the vitrification phase. A dense and viscous glass coating layer is produced. The dense and viscous glass coating layer refers to a state in which the direct contact between the molten steel and the refractory is prevented by the glass coating, and the glass coating does not easily flow out due to the molten steel flow. By forming this glass coating layer at the interface between the molten steel and the refractory, the surface of the surface of the refractory is smoothed, and the action of suppressing micro turbulence (molten steel vortex) of the molten steel is also obtained. Suppression of the molten steel vortex on the refractory wall surface suppresses the collision of non-metallic inclusions such as Al ₂ O ₃ suspended in the molten steel due to the inertial force of the molten steel vortex on the refractory surface. Suppress the phenomenon. Furthermore, the formation of a dense and viscous glass coating layer on the refractory operating surface suppresses the dissolution of refractory components such as carbon and silicon into molten steel, and the inclusion of inclusions such as Al ₂ O ₃ It becomes possible to prevent the phenomenon. When the refractory material comes into direct contact with the molten steel and the refractory components such as carbon and silicon melt into the molten steel, a surface tension gradient of the molten steel is generated along with the solute concentration gradient in the molten steel near the wall surface. It promotes the phenomenon of alumina adhesion on the object wall.

  Thus, in order to form a dense and viscous glass coating layer at the interface between the refractory and the molten steel, while suppressing the reaction with the composition excluding the glass phase, on the other hand, the formation of the glass phase on the operating surface It is necessary to make sure.

The present inventors investigated how these vitrification components affect the alumina adhesion phenomenon at a molten steel flow rate by a rotating test method in molten steel. As a result, a total of (SiO ₂ + B ₂ O ₃ ) component and (CaO + R ₂ O) component is contained in an amount of 1.0% by mass or more and 8.0% by mass or less, and the (CaO + R ₂ O) / (SiO ₂ + B ₂ O _3). It was found that the alumina adhesion phenomenon can be suppressed when the mass ratio of) is 0.5 or more and 2.0 or less.

When the total of SiO ₂ , B ₂ O ₃ , CaO and R ₂ O is less than 1.0% by mass, these are dispersed in the refractory structure, and the amount thereof is relative to other refractory aggregates. Too little, it does not lead to the formation of a glass phase as a uniform film layer.

Even if the total of SiO ₂ , B ₂ O ₃ , CaO and R ₂ O is 1.0% by mass or more and 8.0% by mass or less, the mass ratio of (CaO + R ₂ O) / (SiO ₂ + B ₂ O ₃ ) If it is less than 0.5 or exceeds 2.0, a dense and viscous glass coating layer is not formed on the molten steel working surface, and the effect of preventing the inclusion of inclusions such as Al ₂ O ₃ (the effect of the target range) is achieved. Can't get. That is, when the mass ratio is less than 0.5, the amount of the glass phase with a high viscosity stays scattered in a part of the refractory structure, and the amount thereof is small. A glass coating layer having such a low viscosity as to decrease is not formed. On the other hand, if the mass ratio exceeds 2.0, a soft coating layer in which the low-viscosity glass phase is distributed throughout the refractory structure, and the molten steel operation surface exceeds the extent of reducing adhesion of inclusions in the molten steel. As a result, the tendency of melting damage due to molten steel wear increases.

Further, if the total of SiO ₂ , B ₂ O ₃ , CaO and R ₂ O exceeds 8.0% by mass, the progress of vitrification in the refractory structure in the temperature range of the molten steel temperature level becomes large. Problems such as a decrease in the degree and an increase in melting damage occur.

In order to maintain the matrix structure including such a glass phase while maintaining the strength required as a refractory for a continuous casting nozzle, the above-described components (SiO ₂ , B ₂ O that contribute to the formation of a glass phase). ₃ , CaO and R ₂ O) and the aggregate part (mainly about 0.001 mm or more and 1 mm or less in particle size) as a balance other than carbon is mainly composed of Al ₂ O ₃ . The mineral phase of Al ₂ O ₃ is preferably a thermally stable corundum phase. If it is Al ₂ O ₃ as a corundum, it will not melt | dissolve at an early stage with respect to the said glass phase, and the lifetime of a moderate nozzle can be maintained. In addition, since it can have the same thermal expansion characteristics as the alumina-graphite material, which is the material for the main body of general continuous casting nozzles, it is easy to handle in terms of thermal shock resistance and erosion resistance. There is also an advantage.

  The present invention includes the inevitable component and the inevitable amount derived from raw materials used in a general continuous casting refractory or mixed in a general continuous casting refractory manufacturing method in the remaining part. The effect is not significantly impaired.

  The refractory of the present invention contains carbon in an amount of 20.0% by mass or more and 34.5% by mass or less in order to obtain thermal shock resistance comparable to that of the alumina-graphite refractory in the main body of a continuous casting nozzle. Including. This carbon refers to the total of carbon as aggregate particles such as graphite and carbon as a binder.

  Carbon as aggregate particles is graphite aggregate, which is added as a filler between carbonaceous connective tissues to increase structure strength, increase thermal conductivity, and increase thermal expansion coefficient. The thermal shock resistance can be improved by the action of lowering. In addition, the presence of carbonaceous aggregate particles (carbon as a binder can also be regarded as a part of this) between oxides, etc., has the effect of suppressing oxide sintering and low melting reaction. Yes, stabilization of casting quality can be expected.

  The amount of carbon in the aggregate particles (graphite aggregate) is preferably 18.0% by mass or more and 33.5% by mass or less. If it is less than 18.0% by mass, it becomes difficult to ensure sufficient resistance against thermal shock when the molten steel is received from a preheated state of about 1000 ° C. If it exceeds 33.5% by mass, it will be easily damaged by the wear of the molten steel flow, the service life of the continuous casting nozzle will be shortened, and local wear due to molten steel drift will be likely to occur.

  Carbon as a binder bears the strength of the refractory itself, maintains its form as a structure, and mainly imparts fracture resistance to thermal shock. The carbon as the binder is preferably obtained mainly from a resin, pitch, tar, or the like that has a large amount of fixed carbon and forms a carbon bond at a high temperature (in a non-oxidizing atmosphere of about 1000 ° C. or higher). The carbon as the binder is preferably 1.0% by mass or more. If it is less than 1.0% by mass, it is difficult to obtain sufficient strength to maintain a structure in which aggregates are bonded with carbon. Further, when the thickness of the refractory according to the present invention is relatively small (for example, about 10 mm or less), it is preferable to increase the initial strength, or when the continuous casting nozzle is manufactured by applying the refractory according to the present invention. When it is sometimes preferable to further improve the uniformity and filling properties, 2.0% by mass or more is more preferable. The upper limit is preferably 5.0% by mass or less. If it exceeds 5.0% by mass, the structure strength of the carbon bond is sufficient, but it is not preferable because the thermal shock resistance and the yield in producing the product tend to be reduced. What is necessary is just to determine the carbon amount as this binder according to the conditions, the condition, etc. at the time of individual operation or manufacture.

The refractory of the present invention described above can prevent adhesion of inclusions such as Al ₂ O ₃ or clogging in the nozzle by disposing the refractory of the present invention on a part or all of the surface in contact with the molten steel in the continuous casting nozzle. (Claim 2). That is, the part with much adhesion may be mainly arranged according to the condition of individual operation and the adhesion situation of inclusions such as Al ₂ O ₃ . In addition, the thickness is determined in consideration of the degree of erosion of the refractory according to the present invention, the degree of adhesion of inclusions such as Al ₂ O _3, and the set service life according to the conditions of individual operations. do it.

  The continuous casting nozzle in which the layer made of the refractory according to the present invention is arranged on the inner hole side has the same thermal expansion characteristics as the alumina-graphitic layer of the main body of the continuous refractory according to the present invention. Therefore, between the inner hole side layer made of the refractory of the present invention and the alumina-graphite layer on the outer peripheral side, there is a space or other special mortar layer for the purpose of relaxing stress. There is no need for a unique structure such as installation. That is, it can be set as the integral structure which formed simultaneously the inner-hole side layer which consists of a refractory material of this invention, and the alumina-graphite layer of the outer peripheral side (Claim 3).

With the refractory material of the present invention and the continuous casting nozzle in which the refractory material is disposed, it is possible to prevent the inclusion of inclusions such as Al ₂ O ₃ or the clogging in the nozzle in the continuous casting nozzle.

  Further, the thermal expansion characteristics between the refractory of the present invention and a refractory for a general continuous casting nozzle are comparable, and the composition and structure of the refractory such as refractory aggregate, graphite, carbon bond, etc. Since they are approximate to the extent that they can be regarded as almost the same, there is no need for a special structure for the purpose of buffering various phenomena between these refractories. Furthermore, in the production of a continuous casting nozzle in which this refractory is arranged, it is possible to handle almost the same refractory as a soil, a molded body, etc., and simultaneous integral molding is possible. By these, the nozzle for continuous casting as an integral structure product advantageous in strength, handling, etc. can be used for continuous casting operation, which can contribute to stabilization of continuous casting operation.

  As described above, the refractory according to the present invention mainly includes the same refractory aggregate as the general refractory for continuous casting nozzles used mainly for the main body of the continuous casting nozzle other than the refractory according to the present invention. And almost the same structure (graphite, dispersed state of various refractory aggregates, connective structure, etc.). Therefore, the thermal expansion characteristics between the refractory of the present invention and the other refractories are approximately the same (a degree that does not cause mutual destruction and buffer).

On the other hand, the thermal expansion coefficient in the high temperature range from about 1000 ° C. to the vicinity of the molten steel temperature (about 1500 ° C.) of the refractory containing CaO in such an amount that adhesion of Al ₂ O ₃ inclusions can be prevented. Is about 1.5 to about 2 times that of a refractory for a general continuous casting nozzle body. In a structure in which such a CaO-containing refractory having thermal expansion characteristics is disposed on the inner hole side of a refractory for a main body of a general continuous casting nozzle, the CaO-containing refractory breaks the refractory on the outer peripheral side. There are problems such as. Furthermore, since the refractory containing a CaO amount that can prevent adhesion of Al ₂ O ₃ inclusions is easy to disintegrate due to the hydration of CaO, there are restrictions on the components and structure of the raw material used as the CaO source. There are inherent difficulties in handling raw materials, manufacturing processes, product storage and handling, and the like.

The refractory according to the present invention does not have a problem inherent to a refractory containing a CaO amount sufficient to prevent the above-described adhesion of Al ₂ O ₃ inclusions. Therefore, the continuous casting nozzle having the refractory according to the present invention does not require a special structure for the purpose of buffering various phenomena between different refractories. Furthermore, also in the manufacture of the continuous casting nozzle having the refractory of the present invention, the same handling as the raw material and manufacturing process of a general continuous casting nozzle is possible. From these facts, the continuous casting nozzle in which the refractory according to the present invention is arranged as the inner hole side layer can be simultaneously and integrally formed with the refractory forming the main body of a general continuous casting nozzle.

The manufacturing method of the refractory material of this invention is described.
Examples of raw materials for glass-forming oxides of SiO ₂ and B ₂ O ₃ include amorphous silica and boric acid, and raw materials for glass-modified oxides of CaO and R ₂ O include alkaline earth oxides and alkali metal oxides. Reagents with high purity are preferred, but various silica fine powders mainly composed of SiO ₂ , boric acid powder, borosilicate glass, industrial glass powder, frit powder, synthetic slag powder, Portland cement , Alumina cement, boric acid compound, borax powder, borate compound, dolomite powder, various silicates, and various carbonates can be used. Moreover, the alkali silicate etc. which consist of a vitrification base material component and a vitrification adjuvant component can also be used. However, for uniform vitrification, it is preferable to use glass frit fine powder whose components have been adjusted and melt-pulverized in advance.

By addition of these vitrification components, and in a refractory structure, SiO ₂ , B ₂ O ₃ , CaO and R ₂ O are included in a total of 1.0% by mass or more and 8.0% by mass or less, and (CaO + R ₂ O) When the mass ratio of / (SiO ₂ + B ₂ O ₃ ) satisfies the condition of 0.5 or more and 2.0 or less, the molten steel flow velocity is used in a steel type that easily causes inclusions such as alumina or other inclusions such as alumina or clogging of the inner hole. It is possible to obtain a glass film layer that is viscous enough to obtain the effect of preventing clogging and the like below.

  Moreover, these vitrification components exhibit the effect by disperse | distributing uniformly in a refractory structure. The aggregate particle size used for refractories for continuous casting nozzles such as immersion nozzles and long nozzles generally has a maximum size of about 1 mm from the viewpoint of the homogeneity of the structure, thermal shock resistance, and corrosion resistance. Therefore, in order to disperse the vitrification component evenly in the matrix between the aggregates of the refractory, the addition of these vitrification components is to reduce the particles of 0.1 mm or less, which is 1/10 or less of the aggregate size. Addition in a powder containing 90.0% by mass or more is preferable. When 0.1 mm or less is less than 90.0% by mass, the vitrification component is not evenly dispersed in the structure, the vitrification component is unevenly distributed, the refractory and the molten steel come into contact, and the refractory operating surface Thus, it becomes difficult to form a dense and viscous glass coating layer uniformly.

  As the carbon as the aggregate particle, it is preferable to use a graphite aggregate in which a hexagonal net surface crystal such as scale-like graphite, earth-like graphite particle, and artificial graphite is developed. In particular, the use of naturally occurring scaly graphite is most preferable in terms of thermal shock. The carbon content in the graphite aggregate is preferably 90.0% by mass or more (including 100% by mass excluding inevitable impurities). The reason is that the purity is less than 90.0% by mass, resulting in a high elastic modulus of the refractory structure due to a sintering reaction between impurities or impurities and other raw material particles, etc., resulting in a decrease in thermal shock resistance. It is to do.

  As described above, these graphite aggregates are added as fillers between carbonaceous connective tissues, thereby increasing the strength of the structure, increasing the thermal conductivity, and reducing the thermal expansion coefficient. Can improve. In addition, since the carbon including the binder is uniformly dispersed between the oxides and the like, there is an effect of suppressing the sintering of the oxide and the low melting reaction, and the quality during the casting can be stabilized. In order to make it exist in the state disperse | distributed uniformly in this way, it is preferable to use the graphite aggregate whose particle size is 2 mm or less. However, when a graphite aggregate whose particle size is smaller than 0.1 mm is mainly used, the homogeneity of the structure is excellent, but the thermal shock resistance is lowered. On the other hand, when the particle size is larger than 2 mm, the thermal shock resistance is excellent, but the components are likely to be unevenly distributed in the structure. Therefore, the particle size of the graphite aggregate is preferably 0.1 mm or more and 2 mm or less.

The refractory of the present invention may be composed of Al ₂ O ₃ except for the aforementioned vitrification components (SiO ₂ , B ₂ O ₃ , CaO, R ₂ O) and the remainder other than carbon except raw materials or inevitable components in production. Features. Al ₂ O ₃ having a particle size of more than 0.1 mm is preferably 80.0% by mass or more, more preferably 90.0% by mass or more, based on the entire aggregate. The reason for this is that the portion forming the glass phase is preferably dispersed only in the refractory matrix with only those components as much as possible, and other skeletons that maintain the structure and strength of other refractories. This is because the particles are dissolved in the glass phase or react with the glass component to produce a low-melt material, and the factors that cause the deterioration of the structure are made as small as possible. In addition, a part of Al ₂ O ₃ aggregate is in a range of 10.0% by mass or less with respect to the refractory aggregate and the aggregate as a whole, which hardly reacts with raw materials of vitrification components such as SiC, ZrO _{2 and} zirconia compounds. It is possible to substitute.

Here, the balance other than the vitrifying component and carbon described above, in addition to Al ₂ O ₃ described above, which may contain inevitable components such as to be mixed in the raw material origin or production. Among these unavoidable components, impurities such as Fe ₂ O ₃ and TiO ₂ are preferably suppressed to about 1.0% by mass or less.

  These powders are mixed to make a uniform powder mixture. Then, a binder such as a phenolic resin, pitch, or tar as a carbonaceous raw material that bears the connective structure is appropriately selected and added to the powder mixture and uniformly kneaded to obtain a molding clay. The raw material used as the binder may be either powder or liquid, but it is important to adjust the plasticity of the earth according to the characteristics of the earth suitable for molding.

  Next, an example is described about the manufacturing method of the nozzle for continuous casting which installed the refractory material obtained from the said refractory material of this invention in the inner-hole side layer.

  Separately from the refractory clay of the present invention, an outer layer, that is, a clay for the main body of the nozzle for continuous casting is prepared (a general manufacturing method may be used). Next, a step of providing a plurality of spaces partitioned to a predetermined size for forming the inner hole side layer and the outer peripheral side layer in the molding mold, and each space in the molding mold were produced exclusively for each. Yes. Adjacent soil is directly contacted, such as by filling it with soil and removing the partition of the space.

  These directly contacted soils are simultaneously pressed by a CIP device to be integrally formed. The obtained molded body is heat-treated at 600 ° C. or higher and 1300 ° C. or lower in a non-oxidizing atmosphere or in an oxidizing atmosphere with the surface subjected to an antioxidant treatment. Prior to the heat treatment step, an independent heat treatment step may be included at a temperature lower than the above temperature for the purpose of removing volatile components and curing the resin. Finally, processing or the like is appropriately performed in the same manner as in the manufacture of a normal continuous casting nozzle.

  The basic operation / working method of each process described above, the apparatus to be used, and the like may be the same as those of a general continuous casting nozzle manufacturing method.

  As described above, the refractory for the continuous casting nozzle of the present invention is arranged as the inner hole side layer only on the inner hole surface of the continuous casting nozzle, as described in the first embodiment. However, the present invention can be used not only for the inner hole side layer but also for other parts, for example, the aforementioned “main part” and the entire continuous casting nozzle.

  The manufacturing method of the continuous casting nozzle using the refractory material of the present invention is not limited to an integrated manufacturing method with other materials as the inner hole side layer, and (1) manufactured as a cylindrical molded body. A method of attaching a tube body to an inner hole of a separately manufactured main body portion and fixing it with a mortar or the like, and (2) forming a nozzle main body portion and an inner hole side layer portion as a single body of the material of the present invention. The method can be adopted.

  Next, examples of the present invention will be described.

<Example A>
In Example A, the total amount of SiO ₂ , B ₂ O ₃ , CaO and R ₂ O contained in the refractory, and the mass ratio of (CaO + R ₂ O) / (SiO ₂ + B ₂ O ₃ ) are Al _2. O ₃ or the like shows the results of investigating the effect on erosion rate of deposition rate or refractory inclusions.

The investigation was conducted by a test method in which the target sample was immersed in molten steel and the sample was further rotated in the molten steel (hereinafter, this test method is simply referred to as “rotating test in molten steel”). This rotating test in molten steel was established by confirming the correlation between the adhesion phenomenon and the erosion phenomenon of inclusions such as Al ₂ O ₃ with the phenomena in the actual furnace with a large number of materials, etc. with respect to the refractory in contact with the molten steel. This is a survey and evaluation method.

On the other hand, a refractory having a composition that enhances the adhesion prevention effect of inclusions such as Al ₂ O ₃ tends to have a larger erosion than a normal refractory (not enhancing the adhesion prevention effect). The effect of preventing the adhesion of inclusions such as Al ₂ O ₃ and meltability must be in an optimal balance, and in the case of a refractory with excessive meltability, Al ₂ O ₃ Even if the effect of preventing the adhesion of the inclusions is sufficient, the life of the nozzle for continuous casting may be shortened due to melting, which may hinder the actual operation. Therefore, when conducting a refractory test for enhancing the effect of preventing inclusions such as Al ₂ O _{3 from} adhering, it is necessary to simultaneously evaluate the erosion resistance.

In the rotating test in molten steel, the deposition rate of inclusions such as Al ₂ O ₃ (hereinafter referred to as “+”) is 15 μm / min or less and the loss rate (hereinafter referred to as “−”) from many investigations. CaO-based refractories developed for the same purpose without any trouble in the continuous casting operation in the actual equipment of the steel type with many inclusions such as Al ₂ O ₃ . It has been found that it has the same anti-adhesion effect.

  From the above, in the test of Example A, the dimensional change rate of the target sample was evaluated in the range of +15 μm / min to −15 μm / min as an example of a range in which the problem of the present invention can be solved. .

  The method of the rotating test in molten steel is shown below with FIG.

  FIG. 1 shows a state in which a holder 2 holding a target sample (hereinafter referred to as “test sample”) 1 processed into a predetermined shape at the bottom is immersed in molten steel 3 in a crucible 4. Four test samples 1 are installed in a rectangular parallelepiped, and are respectively fixed to four surfaces of the lower part of the square pole holder 2. This test sample 1 is inserted through a mortar into a recess provided in a square pole holder 2 and can be removed by pulling it out after the test. The upper part of the holder 2 is connected to a rotating shaft (not shown) and is rotatably held with the longitudinal axis as the rotating shaft. Further, the holder 2 has a square shape with a side of 40 mm in the horizontal section with respect to the longitudinal axis, the length in the longitudinal direction is 160 mm, and is made of a zirconia-carbon refractory. In the test sample 1, the exposed part from the holder 2 is 20 mm long, 20 mm wide, and the length L is 25 mm. Further, the lower end surface 1 a of the test sample 1 is attached at a position 10 mm above the lower end surface 2 a of the holder 2.

  The crucible 4 is made of a cylindrical refractory having an inner diameter of 130 mm and a depth of 190 mm. The molten steel 3 is stored in the crucible 4, and the crucible 4 is built in the high frequency induction furnace 5, and the molten state and temperature of the molten steel 3 can be controlled. The immersion depth of the holder 2 in the molten steel 3 is 50 mm or more. Although not shown, the upper surface can be covered.

  In the rotating test in molten steel, the test sample is preheated for 5 minutes immediately above the molten steel, then immersed in the molten low-carbon aluminum killed steel, and the average peripheral speed of 1 m / sec on the outermost peripheral surface of the test sample. Rotate with During the test, the oxygen concentration is kept in the range of 10 to 50 ppm by adding aluminum into the molten steel, and the temperature is kept in the range of 1550 to 1600 ° C. Pull up after 3 hours and measure the dimensions of the test sample.

  For the measurement of the adhesion or erosion rate, as shown in FIG. 2, the test sample 1 after completion of the test is removed from the holder and cut along a horizontal plane (surface in the rotational circumferential direction) perpendicular to the rotation axis. On the test surface, six lengths are measured and averaged at a pitch of 3 mm from the side end surface 1b toward the rotation axis direction. The test sample before the molten steel rotation test is also measured and averaged at the same position. The average value (μm) after the rotating test in molten steel is subtracted from the average value (μm) before the rotating test in molten steel, and the adhesion or erosion rate (μm / min) is calculated by dividing the value by the test time of 180 minutes. To do.

Tables 1 and 2 show the composition and results of the refractories.
As a result of the rotating test in molten steel, the total amount of SiO ₂ , B ₂ O ₃ , CaO and R ₂ O is 1.0 mass% or more and 8.0 mass% or less, and (CaO + R ₂ O) / (SiO ₂ + B ₂ O ₃ ) Is in the range of 0.5 to 2.0, it can be seen that the rate of dimensional change can satisfy the range of +15 μm / min to −15 μm / min.

Further, each of SiO ₂ , B ₂ O ₃ , CaO and R ₂ O in total is close to the lower limit of about 1% by mass, and (CaO + R ₂ O) / (SiO ₂ + B ₂ O ₃ ) is 0.5 which is the lower limit. Also in the examples (Examples 1 to 6), about 71% to about 52% deposition compared to the deposition rate of +21 μm / min of Comparative Example 1 containing no SiO ₂ , B ₂ O ₃ , CaO and R ₂ O. It is a speed, and the adhesion speed reduction effect is observed. Note that R in R ₂ O, that is, Na, K, and Li, show almost the same effect.

In Comparative Examples 2 to 5, in which silica was simply added to Comparative Example 1 containing no silica and the amount thereof was increased, ie, (CaO + R ₂ O) / (SiO ₂ + B ₂ O ₃ ) was zero, The adhesion rate tends to increase with increasing amount, and none of them satisfies the target value for adhesion. This is considered to be because a viscous glass coating layer was not formed and Al in the molten steel was oxidized by silica and an indirect reaction involving a reaction with carbon.

Comparative Example 7 in which (CaO + R ₂ O) / (SiO ₂ + B ₂ O ₃ ) is less than 0.5 even if the total of SiO ₂ , B ₂ O ₃ , CaO and R ₂ O is 1.0 mass% or more, In Comparative Example 9, the deposition rate is high, and none of them satisfies the target value of the deposition rate.

In Example 14 in which the total of SiO ₂ , B ₂ O ₃ , CaO and R ₂ O was 8.0% by mass and (CaO + R ₂ O) / (SiO ₂ + B ₂ O ₃ ) was 2.0, the erosion loss Although it is a trend, it satisfies the target value. However, even if the total of SiO ₂ , B ₂ O ₃ , CaO and R ₂ O is 8% by mass, Comparative Example 10 in which CaO + R ₂ O) / (SiO ₂ + B ₂ O ₃ ) exceeds 2.0, _{Further, CaO + R 2 O) /} (SiO 2 + B 2 O 3) is _SiO 2 be in the range of _0.5~2.0, B ₂ O _3, the total of CaO and _{R 2} O is 8.0 wt% In Comparative Example 11 and Comparative Example 12 that exceed the above values, the erosion rate increases, and none of them satisfies the target value of the erosion rate.

<Example B>
Example B shows the result of investigating the influence of the amount of carbon contained in the refractory material on the deposition rate of inclusions such as Al ₂ O ₃ or the erosion rate of the refractory material. _{Further, SiO 2, B 2 O 3} , other than CaO and _{R 2} O and carbon, _Al 2 _{O 3} or the like interposed in the case of _Al 2 _{O 3} to the remainder mainly comprising a case and ZrO ₂ and SiC containing ZrO ₂ The result of investigating the influence on the deposition rate of objects or the rate of refractory melting is also shown.

  The investigation was carried out by a rotating test in molten steel similar to Example A. Table 3 shows the composition and results of the refractory.

As a result of the rotation test in molten steel, in Comparative Example 13 where the carbon content is 19.0% by mass, the deposition rate of Al ₂ O ₃ inclusions and the like is 17 μm / min exceeding the target of 15 μm / min, whereas the carbon content There reduced deposition rates, such as example 15, _Al 2 _{O 3} inclusions 20.0% by weight and abruptly 8 [mu] m / min, within 15 [mu] m / min, which is a target value of the deposition rate of _Al 2 _{O 3} or the like inclusions It can be seen that can be obtained. Further, in Comparative Example 14 in which the carbon content is 35.5% by mass, the erosion rate is 21 μm / min exceeding the target of 15 μm / min, whereas in Example 19 with 34.5% by mass, the erosion rate is 15 μm. It can be seen that the target value of the erosion rate within 15 μm / min can be obtained. From the above, it can be seen that the carbon content range needs to be 20.0 mass% or more and 34.5 mass% or less.

Moreover, in the case where ZrO ₂ is contained in the remainder mainly composed of Al ₂ O ₃ with respect to the refractory having the composition of the content of SiO ₂ , B ₂ O ₃ , CaO and R ₂ O and carbon of Example 10. Also in Example 20 and Example 21 containing ZrO ₂ and SiC, it can be seen that a target value of ± 15 μm / min, which is the target value of the rotating test in molten steel, can be obtained.

<Example C>
Example C is an refractory material of the present invention, an alumina-graphite refractory material (hereinafter simply referred to as “AG refractory material for main body”) used as a material for the main body of a conventional continuous casting nozzle of the prior art. CaO-MgO refractories (hereinafter simply referred to as “CMG refractories”) used as a countermeasure against adhesion of inclusions such as Al ₂ O _{3. In} actual operation, stress buffer such as mortar is provided between the layers of the main body. The result of comparing the thermal expansion characteristics of a layer having a function is required).

  In addition to the main refractory aggregate, the amounts of graphite and carbon contained in each refractory material having a great influence on the thermal expansion characteristics were compared to each other.

Tables 1 to 3 show the raw materials and the like that are subject to the total ratio of (CaO + R ₂ O) / (SiO ₂ + B ₂ O ₃ ) of SiO ₂ , B ₂ O ₃ , CaO and R ₂ O of the refractory of the present invention. Each of the raw materials added to the outer shell was adjusted to a predetermined ratio. Several representative test results were obtained, and an average value was calculated from the test results.

  The results are shown in Table 4.

  The refractories of the present invention (Examples 22 and 23) exhibit substantially the same thermal expansion characteristics as the main body AG refractories (Comparative Examples 15 and 16). Therefore, in the continuous casting nozzle of the composite structure in which the refractory of the present invention is installed in the inner hole side layer using the AG refractory for the main body portion in the main body portion, the inner hole side layer is not installed. It can be regarded as the same in terms of thermal expansion with a continuous casting nozzle having a structure composed of a single layer of AG refractory for the main body. That is, regarding thermal expansion, it can be regarded as the same thing as a continuous casting nozzle having a structure composed of a single-layer AG refractory body layer without an inner hole side layer.

  This is because in the continuous casting nozzle of the composite structure in which the refractory of the present invention is used for the main body portion and the refractory of the present invention is installed in the inner hole side layer, the inner hole side between the layers of both refractories A third layer such as a mortar layer having a function of relieving stress associated with thermal expansion of the layer (refractory material of the present invention) is not required, and can be a continuous structure (integrated structure) in direct contact; and In the production, it is shown that a production method such as integrally molding a soil can be adopted.

  On the other hand, the CMG refractories (Comparative Example 17 and Comparative Example 18) show larger thermal expansion characteristics than the AG refractories for the main body (Comparative Examples 15 and 16). This is because, in a continuous casting nozzle having a composite structure in which an AG refractory for the main body is used for the main body and the CMG refractory is installed in the inner hole side layer, the inner hole side layer ( CMG refractory) requires a third layer such as a mortar layer that has a function to relieve the stress associated with thermal expansion, and normally, the body and the inner hole side layer are manufactured separately. And it proves that means such as the last combination is necessary.

<Example D>
Example D shows the result of investigating the effect of subjecting the refractory of the present invention to operation of a continuous casting nozzle in actual equipment.

  As the refractory of the example of the present invention, the refractory of Example 10 having a good balance between melting loss and adhesion was used, and the refractory of Comparative Example 1 (alumina-graphite refractory) was used as a comparative example. .

  As shown in FIG. 3, the continuous casting nozzle (immersion nozzle) of the embodiment has the refractory 10 of the present invention disposed only on the inner hole 11 side with a thickness of 10 mm over the entire length of the inner hole 11, and the body portion is made of alumina. -It was set as the structure which has arrange | positioned the graphite refractory 12. In addition, the continuous casting nozzle (immersion nozzle) of the example was manufactured by simultaneous integral molding of the refractory for the main body portion and the inner hole side layer, and had an integrated structure in which the layers were in direct contact and formed into a continuous structure.

  The structure of the nozzle for continuous casting (immersion nozzle) of the comparative example was a structure in which the inner hole side layer and the main body portion were composed of a single layer made of the refractory material of Comparative Example 1. However, in both Examples and Comparative Examples, zirconia-graphitic refractory (13 in FIG. 3) was arranged in the powder portion on the outermost peripheral side of the continuous casting nozzle.

  Using the continuous casting nozzles of the examples and comparative examples, casting was performed for 3 ch for about 3 hours with low-carbon aluminum killed steel. As a result, alumina adhesion was slight in the continuous casting nozzle of the present invention. On the other hand, in the continuous casting nozzle of the comparative example, alumina adhered to the inner hole portion and a clogging phenomenon was observed.

  In the continuous casting nozzle of the embodiment shown in FIG. 3, the refractory material of the present invention is arranged over the entire length of the inner hole. However, depending on the use conditions of the continuous casting nozzle, etc. You may arrange | position the refractory material of this invention partially.

It is explanatory drawing which shows the method of a rotating test in molten steel. It is an image figure of the cross section of the test sample after a rotation test in molten steel, (a) shows the case of adhesion and (b) shows the case of melting damage. It is sectional drawing which shows an example of the nozzle for continuous casting of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Test sample 1a Lower end surface of test sample 1b Side end surface of test sample 2 Holder 2a Lower end surface of holder 3 Molten steel 4 Crucible 5 High frequency generator 10 Refractory of the present invention 11 Inner hole of nozzle for continuous casting 12 Alumina-graphite refractory 13 Zirconia-graphite refractory

Claims (2)

One or two of SiO ₂ and B ₂ O ₃ and one or two of CaO and R ₂ O (R: Na, K, Li) are 1.0% by mass or more and 8.0% by mass in total. hereinafter, comprising less 34.5 wt% 20.0 wt% carbon, the balance being Al ₂ O ₃ except for unavoidable components in the raw material or manufacturing, and the mass ratio _{(CaO + R 2 O) /} (SiO 2 + B ₂ O ₃ ) is a continuous casting nozzle in which a refractory having 0.5 or more and 2.0 or less is disposed on a part or all of a surface in contact with molten steel.   SiO ₂ And B ₂ O ₃ One or two of them, CaO and R ₂ A total of one or two of O (R: Na, K, Li) is 1.0% by mass or more and 8.0% by mass or less, carbon is 20.0% by mass or more and 34.5% by mass or less, SiC and ZrO ₂ Among them, one or two of them are contained in an amount of 9% by mass or less, and the balance is Al except for raw materials or inevitable components in production. ₂ O ₃ And the mass ratio (CaO + R ₂ O) / (SiO ₂ + B ₂ O ₃ ) Is a continuous casting nozzle in which a refractory having a value of 0.5 or more and 2.0 or less is disposed on a part or all of the surface in contact with the molten steel.

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