Specification
Title of the invention: CaO-ZrO2 composition, method for producing CaO-ZrO2 composition, refractory containing CaO-ZrO2 and nozzle for casting.
Technical field
[0001]
The present invention suppresses the adhesion of alumina generated during continuous casting of CaO-ZrO 2 composition having 　a special composition and structure, a method for producing the CaO-ZrO 2 composition thereof, and molten steel, especially aluminum killed steel, which is harmful. It relates to a refractory material capable of reducing inclusions, and a casting nozzle using the refractory material (hereinafter, also simply referred to as “nozzle”).
Background technology
[0002]
　Alumina-based inclusions in molten steel have the property of depositing on the surface of refractories due to physical contact with the molten steel and chemical action, and the deposits grow into large inclusions, which together with the molten steel are slabs. It is taken into the inside and becomes a defect of the slab, which deteriorates the quality. In addition, alumina-based inclusions in the molten steel are deposited in the inner holes of casting nozzles such as immersion nozzles and the discharge holes that have a large effect on the flow of hot water in the mold, and their initial shape changes. When it arrives, the molten steel does not flow evenly in the mold, and so-called drift may cause mold powder, air bubbles, etc. to be caught in the slab, degrading the quality.
　In recent years, there has been an increasing demand for higher quality steel and higher durability of casting nozzles. Therefore, in addition to preventing alumina from adhering to refractories of casting nozzles and improving the nozzle structure, fire resistance is also increasing. Various measures have been attempted in terms of materials to minimize the amount of material wear and adhesion.
[0003]
　There is a method of containing CaO in order to increase the ability to produce a compound having a melting point equal to or lower than the molten steel temperature. By containing CaO, the alumina precipitated from the molten steel reacts with CaO in the nozzle material to generate a reactant having a lower melting point than the alumina. Since this reactant is a low melting point substance, it has a low viscosity and is easily discharged by the molten steel flow to suppress adhesion to the inner wall of the nozzle. Therefore, alumina is less likely to grow on the refractory wall and cause nozzle blockage.
[0004]
　Attempts have been made to make the composition mainly composed of CaO quality and CaO-MgO quality in which the amount of CaO in the refractory is increased in order to enhance the resistance to adhesion. The core element of these technologies is the presence of CaO, which reacts with alumina inclusions, in the highest possible content, giving high self-fluxability to the contact surface of the refractory with molten steel and suppressing adhesion to the inner hole surface of the nozzle. Furthermore, alumina is to be removed by flowing down and floating as a compound having a low melting point.
[0005]
　As a refractory mainly containing CaO, for example, Patent Document 1 discloses a refractory containing a dolomite composition as a CaO source.
[0006]
　Such a refractory mainly composed of CaO quality will contain a large amount of free CaO, that is, CaO in a form that is not a compound or a solid solution. Free CaO easily produces calcium hydroxide (Ca (OH) 2
) 　when it comes into direct contact with moisture in the air or directly (causing a so-called digestion phenomenon). When particles containing CaO are digested, not only intragranular destruction but also refractory structure may be destroyed due to volume expansion when Ca (OH) 2 is hydrated, making it difficult to maintain the shape of the structure. Not a few. Such a simple increase in the amount of free CaO causes serious problems not only in manufacturing but also in storage, transportation, and use (when used for steel casting). 　Further, since CaO (lime) has a large thermal expansion, a refractory material containing a large amount of CaO component is likely to be destroyed by thermal shock or static stress due to the large thermal expansion in addition to digestion.
[0007]
　In order to solve the problem caused by the digestion of free Ca0, the present inventors have invented a refractory in which the surface of Ca0 is coated with carbonic acid oxide or the like as shown in Patent Document 2, for example.
　Although the technique of Patent Document 2 can significantly improve the fracture caused by digestion and thermal expansion, there are still problems due to corrosion resistance and strength depending on the operating conditions such as casting time and steel grade. May occur.
[0008]
　On the other hand, refractories containing a large amount of CaO component are free while containing CaO component for the purpose of solving problems such as digestion and thermal expansion caused by the above-mentioned CaO, and further improving corrosion resistance and strength. A refractory that does not contain CaO has been proposed.
　For example, Patent Document 3 describes a C-less material having CaO: 5 to 40% by mass, SiO 2 : 2 to 30% by mass, ZrO 2 : 35 to 80% by mass, and carbon: less than 5% by mass (including zero). Refractories are disclosed.
　However, since it is premised that the refractory substance as in Patent Document 3 is not digested, for example, in the case of the CaO-ZrO2 system, in order to maximize the CaO content, CaO / ZrO containing no free CaO is used. There is no choice but to use two compounds, and the amount of CaO must be limited to about 31% by mass or less. This CaO content of less than about 31% by mass is not sufficient to react or flow down with inclusions in steel mainly composed of alumina, and still often causes adhesion of alumina or clogging of the nozzle inner hole. Furthermore, a slag phase containing ZrO 2
　as a low melting point phase is generated by a contact reaction with alumina, which is an inclusion in steel, on the working surface of the refractory, but it becomes highly viscous, and inclusions such as alumina are generated depending on the flow velocity of the molten steel. It may adhere to the surface of the refractory without flowing down, and there is a problem that stable difficult-to-adhere performance cannot be ensured due to the influence of steel type and operating conditions. 　Also, SiO 2
Since the addition of the component is contained in the entire refractory, not only the self-solubilization on the contact surface with the molten steel but also the softening or self-solubilization of the entire refractory structure is promoted, and the corrosion resistance and strength are excessive. There are also problems such as deterioration.
Prior art literature
Patent documents
[0009]
Patent Document 1: Japanese Patent Application Laid-Open No. 2010-167481
Patent Document 2: International Publication No. 2013/81113
Patent Document 3: Japanese Patent Application Laid-Open No. 2003-040672
Outline of the invention
Problems to be solved by the invention
[0010]
　The problem to be solved by the present invention is a ZrO2-CaO-C refractory containing free CaO, which has remarkable digestibility, suppresses self-solubilization, that is, has corrosion resistance, and is high. It is an object of the present invention to provide a ZrO2 - CaO-C refractory capable of maintaining poor adhesion for a long period of time . Further, it is an object of the present invention to provide a ZrO2 -
CaO composition 　as a refractory raw material for imparting the above-mentioned characteristics to the refractory, a method for producing the same, and a casting nozzle in which the refractory is arranged.
Means to solve problems
[0011]
　The refractory of the present invention is premised on the function of suppressing the adhesion or deposition of oxides (so-called inclusions) derived from molten steel, mainly alumina, which is a deoxidizing product of molten steel, on the surface of the refractory during casting. I have to.
[0012]
　In conventional CaO-containing refractories, the supply of CaO is insufficient from the inside of the material at the interface, causing alumina adhesion, or the CaO-Al 2 O 3 melt generated at the interface during casting is silica in the material. Since the viscosity is lowered due to the influence of such factors, there is a problem that the self-solubilizing property is increased. In order to compensate for such a defect, in the present invention, the ZrO 2 component is contained in the CaO-Al 2 O 3 system composition, thereby improving the stability of the coating film in the CaO-Al 2 O 3 system composition. The present inventors have found that it is possible to obtain the effect of suppressing the above-mentioned damage.
[0013]
　Further, in the present invention, as a means for enhancing the resistance to adhesion of the ZrO2 - CaO-C refractory, the content of the CaO component is adjusted to the CaO amount (31% by mass) of the non - digestable compound CaO / ZrO2. ) Is one of the features of increasing CaO to a content of 40% by mass or more.
　However, it is free by simply adding a large amount of CaO-based composition (for example, lime clinker) in the ZrO 2 -CaO -C refractory that does not contain free CaO, or simply increasing the proportion of the CaO component. This book states that refractories, especially digestibility, cannot be improved by methods such as using a ZrO2-CaO-based composition containing CaO (general / conventional manufacturing method) as a raw material . The inventors have found out.
[0014]
　On the other hand, as described above, the present inventors disclose in the above-mentioned Patent Document 2 for a refractory of CaO-C quality and CaO-MgO-C quality having a high CaO content and a nozzle using such a refractory. We have developed a technique and succeeded in imparting remarkable digestibility and remarkable low thermal expansion. An attempt was made to apply this technique to refractories of ZrO2-CaO-C quality in which the content of CaO component was simply increased by adding CaO clinker, but even if the technique of Patent Document 2 is simply applied, it is fireproof
　. The present inventors have also found that the digestibility of a substance cannot be improved.
[0015]
　Therefore, the present invention has been made to improve the digestibility and the like of the ZrO 2 -CaO -based composition containing free CaO, that is, the raw material particles themselves. That is, the free CaO in the ZrO 2 -CaO raw material particles containing CaO (free CaO) exceeding the solid solubility in ZrO 2
　as the mineral phase is atomized and formed on the surface of the ZrO 2 -CaO raw material particles. The basic feature is to reduce the area of ​​one section in which the exposed CaO portion, that is, the free CaO portion in the ZrO2 - CaO-based raw material particles is in contact with the outside. This makes it possible to prevent hydration of ZrO2 - CaO-based raw material particles 　containing free CaO and improve digestibility. A carbon oxide, an inorganic film, or the like can be further formed on the ZrO 2-CaO-based raw material particles having the basic characteristics, which is unique to the ZrO 2-CaO-based raw material particles having the characteristics of the 　present invention . It is possible to obtain a structure that seamlessly protects the entire surface of the ZrO 2 -CaO raw material particles, which has never been seen before.

[0016]
By applying ZrO2 - CaO- based raw material particles having 　these characteristics to ZrO2 - CaO-C refractories, nozzles, etc., the refractory, heat-impact resistance, and crack resistance of the refractories and nozzles are alleviated. Destructiveness and the like can be improved.
[0017]
　That is, the present invention comprises the following methods for producing 1 to 3 CaO-ZrO 2 compositions, 4 to 5 CaO-ZrO 2 compositions, 6 to 11 CaO-ZrO 2 -containing refractories, and 12 to 14 castings. It is a nozzle for.
1. 1.
　The CaO component is contained in an amount of 40% by mass or more and 60% by mass or less, the mass ratio of the CaO / ZrO2 component is 0.67 or more and 1.5 or less, and the eutectic structure of the CaO crystal and the CaZrO3 crystal is contained . A CaO-ZrO 2 composition in which the width of CaO crystals observable in the structure of the cross section is 50 μm or less .
2. 2. The CaO-ZrO 2 composition according
　to 1 above, wherein the width of the CaO crystal is 20 μm or less . 3. 3. The CaO according to 1 or 2 above, wherein a coating of CaCO 3 having a thickness of 0.1 μm or more and 5 μm or less is continuously present on the surfaces of the CaO crystal and the CaZrO 3 crystal on the surface of the 　CaO-ZrO 2 composition. -ZrO 2 composition.

4.
　A step of heating the CaO raw material and the ZrO 2 raw material to a molten state above the liquidus line in the composition of the CaO component and the ZrO 2 component, and a rate of 10 ° C./sec or more from the above-mentioned molten state to the solid phase temperature. The method for producing a CaO-ZrO 2 composition according to any one of 1 to 3 above, which comprises a step of cooling with .
5.
　The CaO raw material is one or more selected from CaO compounds or quicklime that becomes CaO at the temperature at the time of melting, excluding unavoidable impurities, and the size of the CaO raw material is 10 mm or less
　. The ZrO 2 raw material is one or more selected from CaO-stabilized ZrO 2 , CaO partially stabilized ZrO 2 or unstabilized ZrO 2 , and the size of the ZrO 2 raw material is 10 mm or less. The method for producing a CaO-ZrO 2 composition according to 4 above.
6. A refractory material containing the CaO-ZrO 2 composition according to
　any one of 1 to 3 above .
　When the mass ratio of the CaO / ZrO 2 component is 0.5 or more and 2.2 or less and the total amount excluding the components unavoidable in production is 100% by mass, the total amount of the CaO component and the ZrO 2 component is 65% by mass. A refractory containing CaO-ZrO 2 containing 98% by mass or less and 2% by mass or more and 30% by mass or less of a free carbon component .
7. The CaO-ZrO 2 - containing refractory according to 6 above, wherein the mass ratio of the
　CaO / ZrO 2 component is 0.67 or more and 1.5 or less. 8. 　The CaO according to 6 or 7 above, wherein the content of the free carbon component is 4% by mass or more and 15% by mass or less, and the coefficient of thermal expansion at 1000 ° C. in a non-oxidizing atmosphere is 0.5% or less. -ZrO 2 containing refractory. 9. 　B 2 O 3 , TIO 2 , P 2 O 5 , and V 2 O 5

CaO and B 2 O 3
are contained on the surface of at least CaO crystal of the 　CaO-ZrO 2 composition containing 0.1% by mass or more and 5.0% by mass or less in total of one or more kinds of components selected from. , TiO 2 , P 2 O 5 and V 2 O 5 are formed with an inorganic film having a thickness of 0.1 μm or more and 15 μm or less, which is composed of a compound with one or more kinds of components selected from the above 6 To the Refractory containing CaO-ZrO 2 according to any one of the above 8 . 10. 　Any of the above 6 to 9 above, in which CaCO 3 exists in contact with at least a part of the inorganic film and the content of CaCO 3 is 0.1% by mass or more and about 2.5% by mass or less. The refractory containing CaO-ZrO 2 according to item 1. 11. 　SiC, metallic Si, and B 4

It further contains one or more kinds selected from C, and
　is 10% by mass or less for SiC and 2% by mass or less in total for either one or both of
　metallic Si and B4 C. The Refractory containing　 CaO-ZrO 2 according to any one of the above items.
12. The CaO-ZrO 2
-containing refractory according 　to any one of 6 to 11 is arranged as a single layer on the back surface side from the surface in contact with the molten steel in a part or all of the region in contact with the molten steel. Nozzle for casting. 13. The CaO-ZrO 2 - containing refractory according 　to any one of 6 to 11 is arranged in a part or all of the region of the surface in contact with the molten steel, and the back surface thereof is the surface in contact with the molten steel. A casting nozzle having a plurality of layers in which a layer made of a refractory having a composition different from that of the refractory partially or completely arranged is arranged. 14. 　12. The casting nozzle according to 12 or 13 above, wherein a part of the inner hole is provided with a layer made of a refractory material for blowing gas.

[0018]
　The chemical components of the various components contained in the CaO-ZrO 2 composition and the refractory of the present invention were measured by a method according to JIS R2216 for the sample "after heating in a non-oxidizing atmosphere at 1000 ° C.". The reason for this is to improve the analysis accuracy by removing components such as water, organic substances, hydrates, and carbonic acid compounds in the refractory, and stabilizing the chemical components of the refractory by carbonizing the organic binder component. be. From this point, the heating time shall be until the weight change due to heating disappears (the same shall apply hereinafter).
[0019]
　In the present invention, "free carbon" refers to carbon composed of elemental carbon components excluding unavoidable impurities other than compounds such as carbides such as B4 C and SiC, and various organic binders, pitches, tars, and the like. Continuous carbon black produced by heating at 1000 ° C in a non-oxidizing atmosphere, regardless of whether it is amorphous or crystalline such as graphite, and whether it is particulate (including fibrous) or does not have a specific shape. Refers to all carbon present in the refractory structure regardless of its shape and structure, such as being present in the refractory structure in a targeted or intermittent state. Hereinafter, this "free carbon" is simply referred to as "carbon".
[0020]
The width of the CaO crystal in the CaO-ZrO 2 composition of 　the present invention is the CaO of the particle in the visual field when the cross section of the particle obtained by performing the predetermined sizing of the CaO-ZrO 2 composition is observed with a microscope . Refers to the shorter length of the crystal.
　That is, since CaO crystals often exist continuously in an elongated thin layered form so as to divide the CaO-ZrO 2 crystal structure (see FIG. 4), the "width" is the shorter length of this elongated shape. Point to. Even if the CaO crystals are continuously present in an elongated and thin layer, the CaO crystals may appear as particles, rods, ellipses, or circles depending on how the cross section is cut (see FIG. 4). Again, the "width" refers to the shorter length of the CaO crystal.
[0021]
In the CaO-ZrO 2 composition of 　the present invention, the content of the CaO component is 40% by mass or more and 60% by mass or less, free CaO is present, and a eutectic structure of CaO crystals and CaZrO3 crystals is contained . When this is shown by the mass ratio of the CaO / ZrO 2 components, it is 0.67 or more and 1.5 or less.
　In the conventional general technique, the width of CaO crystals in such a composition is such that, in a composition in which a free CaO component is present (more than about 31% by mass in CaO), the larger the CaO content, the more CaO. The crystalline part is concentrated, and the phase of the continuous structure at that position tends to be large.
　The presence of such a large CaO crystal phase results in extremely low digestibility of such compositions or refractories using such compositions.
[0022]
　The reason for this is that such a large crystal structure is exposed to the outside of the composition (raw material particles) over a wide area, which makes it easy to react with water and the like, and further, the surface of CaO crystals. In order to improve digestibility, a film of carbon oxide CaCO 3 can be formed, but the surface of CaO crystals exposed over such a large area can be coated with a film of carbon oxide or the like. This is because it is difficult to maintain continuity with the CaZrO3 crystals around the CaO crystals, and their coatings and the like tend to fall off easily. By reducing the width of CaO crystals in the CaO-ZrO 2 composition to approximately 50 μm or less, the
　present inventors do not need to install the inorganic or carbon oxide film described later on the surface of the particulate CaO-ZrO 2 composition. , It is possible to remarkably suppress the hydration of CaO crystals, and further, in order to improve digestibility and heat impact resistance, an inorganic film or a film of carbon oxide CaCO 3 described later is formed on the surface of CaO crystals. Even in this case, by reducing the width of the CaO crystal to about 50 μm or less, the inorganic film or the CaCO 3 film can be continuously present on the surface of the CaO crystal and the CaZrO 3 crystal layer, which is a problem of the above-mentioned prior art. I found it along with the points. 　The details of the mechanism are unknown, but particulate CaO-ZrO 2
Due to the small width of the CaO crystals exposed on the outer surface of the composition, the spacing between the CaZrO3 crystals existing between the multiple CaO crystals on the particle surface is also small, and the spacing between the inorganic or carbonic acid oxides near the boundaries of the multiple CaO crystals is also small. It is considered that the coating easily crosslinks with the coating of inorganic or carbonic acid oxide near the adjacent CaO crystal boundary. It is considered that the stability of the crosslinked structure is also enhanced because the film of the inorganic or carbonic acid oxide is bonded to the CaO crystal phase like a large number of spikes.
[0023]
The content of the CaO component in the CaO-ZrO 2 composition of 　the present invention is 40% by mass or more and 60% by mass or less. A preferable region is a eutectic composition region in which the amount of CaO is about 50%, in which CaO is easily crystallized as a fine structure.
　In order to obtain a remarkable adhesion-resistant effect as a refractory (compared to a CaO-ZrO 2 composition containing no free CaO), a CaO content of 40% by mass or more is required. Even in the CaO-ZrO 2
composition of 　the present invention, when the content of the CaO component exceeds 60% by mass, the CaO crystal portion tends to be easily concentrated and the phase of one continuous structure tends to be large. In addition, the digestibility of the composition tends to decrease, and since the composition has a high melting point, the meltability at the time of electric fusion decreases, which causes a problem in terms of production. Therefore, the CaO content should be 60% by mass or less.
[0024]
　It is more preferable that the width of the CaO crystal described above is about 20 μm or less in order to further enhance the effect of suppressing the hydration reaction and the stability of the inorganic or carbide film placed on the surface thereof.
[0025]
　When a coating of calcium oxide CaCO 3 is formed on the surface of CaO crystals, the thickness of the coating of CaCO 3 is preferably 0.1 μm or more and 5 μm or less. A portion where the coating of CaCO 3 is missing during transportation of the CaO-ZrO 2 composition or other handling, or when kneading with other refractory raw materials as a refractory raw material , whether it is less than 0.1 μm or more than 5 μm. This is because there is a high possibility that
[0026]
The refractory of the present invention containing the above-mentioned CaO-ZrO 　2 composition uses only the above-mentioned CaO-ZrO 2 composition as a main raw material, that is, all of the CaO component and the ZrO 2 component of the present invention are CaO-ZrO of the present invention. It is most preferable to use a refractory derived from the two compositions, and in this case, the mass ratio of the CaO / ZrO 2 component is 0.67 or more and 1.5 or less, which is the same as the CaO-ZrO 2 composition of the present invention. ..
　In this case, when the total amount excluding the components unavoidable in manufacturing is 100% by mass, the total amount of CaO and ZrO2 is 65% by mass or more and 98% by mass or less, and the free carbon component is 2% by mass or more and 30% by mass. % Or less will be included.
[0027]
　Further, the refractory material of the present invention containing the above-mentioned CaO-ZrO 2 composition uses the above-mentioned CaO-ZrO 2 composition as a main raw material, but other CaO component-containing compositions such as lime clinker and dolomite. Or, other zirconia component-containing compositions such as unstabilized zirconia, partially stabilized zirconia, stabilized zirconia, and zirconia can also be contained.
　When such another CaO component-containing composition or other zirconia component-containing composition is also contained, the mass ratio of the CaO / ZrO2 component is 0.5 or more and 2.2 or less, excluding the components unavoidable in production. When the total amount is 100% by mass, the total amount of the CaO component and the ZrO2 component is 65% by mass or more and 98% by mass or less.
　The reason for this is that when the other CaO component is contained, there is a high possibility that the other CaO component will be digested, so the amount of the other CaO component must be less than or equal to the extent that the refractory tissue due to the digestion is not destroyed. Because there is. That is, when the mass ratio of the CaO / ZrO2 component in the refractory exceeds 2.2, the possibility that the CaO component is digested increases .
　Further, when the other ZrO 2 component is contained, there is a high possibility that the difficulty in adhesion is lowered by the other ZrO 2 component, so that the other ZrO 2 component is likely to be lowered.This is because the amount of the component needs to be less than or equal to the extent that the poor adhesion is not reduced. That is, if the mass ratio of the CaO / ZrO 2 component in the refractory is less than 0.5 and the total amount of CaO and ZrO 2 is less than 65% by mass, it becomes difficult to obtain a sufficient effect of improving the adhesiveness. ..
[0028]
The mass ratio of the 　CaO / ZrO 2 component, the total amount of the CaO component and the ZrO 2 component may be determined in their ranges according to the required characteristics such as the degree of resistance to adhesion and the strength according to the individual operating conditions.
　In order to maintain high digestibility or suppress excessive self-solubilization, all CaO components in the refractory are derived from the CaO-ZrO 2 composition of the present invention, for example, quicklime or dolomite (for example, quicklime or dolomite (). It is preferable not to contain a raw material containing free CaO derived from CaO-MgO clinker). In this preferable case, the upper limit of the mass ratio of the CaO / ZrO2 component in the refractory is 1.5.
[0029]
　From the viewpoint of resistance to adhesion, it is not necessary to set an upper limit of the total amount of CaO and ZrO 2 in the refractory, but if the total amount of CaO and ZrO 2 exceeds 98% by mass, the refractory is bonded. The carbon component as a material becomes too small, the strength as a refractory is insufficient, and the heat impact resistance is greatly reduced.
　Therefore, the free carbon component in the refractory is 2% by mass or more, but a carbon component such as graphite may be added to further increase the carbon as a binder or improve the heat impact resistance. can.
　If this free carbon component exceeds 30% by mass, the corrosion resistance and wear resistance may be deteriorated, and further, the steel quality may be deteriorated due to the elution of the carbon component into the steel, the generation of inclusions, etc. It shall be mass% or less. The amount of free carbon component is preferably 15% by mass or less in order to further suppress deterioration of corrosion resistance and wear resistance, elution of carbon component into steel, and the like.
[0030]
　Further, in the refractory material of the present invention, one or more components selected from
(1) B 2 O 3 , TIO 2 , P 2 O 5 and V 2 O 5 are contained in a total of 0.1% by mass. The content is 5.0% by mass or less.
(2) According to the above (1) , CaO and the B 2 O 3 , TIO 2 , P 2 O 5 and It is possible to form an inorganic film having a thickness of 0.1 μm or more and 15 μm or less, which is composed of a compound of one kind or two or more kinds of components selected from V 2 O 5 . 　The above-mentioned inorganic film is mainly CaO-ZrO 2
Since it also has a function of protecting the exposed surface of the CaO component of the composition from hydration, the digestibility can be further significantly improved.
[0031]
　Further, during the formation of the inorganic film, the inorganic film formed mainly on the exposed surface of the CaO component of the CaO-ZrO 2 composition shrinks to form a void layer (hereinafter, also referred to as "microspace"), and the voids are formed. The layer functions as a layer that buffers the thermal expansion of the CaO-ZrO 2 composition and other raw material particles.
　In particular, when the content of the free carbon component is as small as 15% by mass or less, the thermal impact resistance generally tends to decrease in the prior art. However, in the refractory of the present invention provided with the above-mentioned inorganic film, the coefficient of thermal expansion in a non-oxidizing atmosphere at 1000 ° C. is about half that of the conventional refractory having a similar chemical composition. It can be 0.5% or less.
[0032]
　When the refractory is subject to temperature changes during preheating, steel receiving, or cooling, voids corresponding to the expansion allowance when the highly expanded particles in the structure expand are formed around the particles in advance by forming the inorganic film. By forming the particles, the expansion of the particles up to a predetermined temperature can be absorbed by the void layer around the particles inside the refractory, and the amount of thermal expansion as the refractory can be reduced. As a result, the heat impact resistance can be significantly improved.
[0033]
　In order to form a void layer on the surface of the particles of the CaO-ZrO 2 composition, a method of contacting the surface with a gas containing water or water for a predetermined time at the raw material stage or the heat treatment stage of the manufacturing process. Or, a hydrate layer, a chloride layer, or a carbon oxide layer is formed to a predetermined thickness by contact with an acid, an alkaline solution, or a gas.
　In other words, this inorganic film forms the above-mentioned inorganic film regardless of whether a carbon oxide film is present or not on the surface of the + particles of the CaO-ZrO 2 composition as a raw material. Is possible.
[0034]
　Next, the mechanism of formation of these inorganic films will be described in detail.
　Since the oxygen partial pressure is low inside the carbon-containing refractory material, oxides with high vapor pressure are easily filled as gas components in the structure, and the gas component is selected on the surface of particles containing the CaO component in the structure. To form a relatively uniform film-like inorganic compound. Alternatively, a similar inorganic compound is produced by direct contact with the CaO component in a liquid phase state or a solid state. The melting point of the oxide used in the present invention is B 2 O 3 : about 480 ° C, TiO 2 : 1840 ° C, P 2 O 5 : 340 ° C, V 2 O 5 : 690 ° C. Of these, B 2 O 3 and V 2 O 5 are particularly suitable oxides for forming an inorganic compound layer on the surface of CaO in the present invention because they have a particularly low melting point and a high vapor pressure.
[0035]
　On the other hand, TiO 2 does not have a low melting point like B 2 O 3 and V 2 O 5 , and its vapor pressure is relatively low, so that it cannot be expected to react with CaO components in the form of gas or liquid contact. However, the method of directly contacting the surface of the particles containing the CaO component makes it possible to form an inorganic compound layer that is difficult to hydrate. Furthermore, since B 2 O 3 and V 2 O 5 have the effect of increasing the reaction rate with TiO 2, by using TiO 2 in combination with B 2 O 3 and V 2 O 5 , the covering property is high and good. It becomes possible to promote the formation of the inorganic compound layer.
[0036]
　It is possible to use one kind or two or more kinds of these oxides. By containing these oxides in the refractory in a total amount of 0.1% by mass or more and 5% by mass, a good inorganic compound layer (coating) can be formed on the surface of CaO. If the content is less than 0.1% by mass, the film cannot be formed, and if it is more than 5% by mass, the film becomes too thick and film defects are likely to occur.
[0037]
　In the inorganic compound layer (coating) formed by the reaction of these oxides with the CaO component, these products are thermodynamically stable and do not undergo a hydration reaction. Therefore, even if it comes into contact with moisture, it does not change itself. In order to prevent the hydration reaction of the active CaO component existing inside the film composed of the inorganic compound,
(a) the produced inorganic compound is stable to water and
(b) the particles containing the CaO component. It is important that the surface of the compound is uniformly coated with this stable inorganic compound, and
(c) the film made of this inorganic compound is not porous and is a defect-free film without cracks or peeling.
..
[0038]
　Regarding (a) above, as described above, the inorganic compound produced by the present invention is stable because it does not hydrate thermodynamically.
[0039]
　As is well known, the hydration reaction of CaO easily proceeds by the following reaction.
　CaO + H 2 O = Ca (OH) 2
　The standard free energy ΔG ° in this reaction is −57.8 kJ / mol (T = 298K).
　As described above, in order to prevent the hydration of CaO, mainly, the pursuit of a method of reducing the activity of CaO in the particles containing the CaO component and inactivating the CaO, or on the surface of the particles containing CaO. At least at the final product stage, the pursuit of dense and stable water component impermeable film formation has been pursued. As the former method, a method of compounding with an oxide such as TiO 2 has been taken, but in order to inactivate CaO, they must be added in excess to form a compound, and as a result, CaO must be compounded. The activity that contributes to the reactivity of itself, the so-called CaO activity, is significantly reduced, and the reactivity with the alumina inclusions in the steel is significantly reduced, which causes a problem in terms of the clogging prevention effect. Furthermore, compounding tends to lead to a lower melting point. Moreover, it cannot be said that the hydration prevention function of the particles containing the CaO component is sufficient. In addition, the latter method may be an extremely thin (0.05-4 μm) carbonated film or an oil-based film, so it is a refractory manufacturing process, especially the kneading, heat treatment, and processing processes of refractory raw materials. Part or all of the coating was torn or disappeared, and sufficient digestibility could not be exhibited.
[0040]
　Examples of the inorganic film (compound) formed on the surface of CaO in the present invention are as follows. 3CaO
・ 　B 2O 3 (+ 32.0kJ / mol), 2CaO ・ B2O3 ( + 44.1kJ / mol), CaO ・ B2O3 ( +82.4kJ / mol) 　3CaO ・ 2TiO 2 (+12.4kJ / ) mol), 4CaO ・ 3TiO 2 (+ 16.8kJ / mol), CaO ・ TiO 2 (+ 24.4kJ / mol) 3CaO 　・ V 2 O 5 (+ 52.9kJ / mol), 2CaO ・ V 2 O 5 (+ 74.6kJ) / Mol), CaO ・ V 2O 5 (+88.2kJ / mol) 3CaO ・ 　P 2

O 5 (+236 kJ / mol), 2CaO · P 2 O 5 (+ 280.7 kJ / mol) In　
　addition, the free energy change (ΔG, at298K) during the hydration reaction of each compound is shown in (). It is shown that the hydration reaction does not occur in all of these inorganic compounds because ΔG is positive.
[0041]
　As described above, the inorganic film formed by the reaction between these oxides and CaO is basically thermodynamically stable and does not cause a hydration reaction. Therefore, even if it comes into contact with moisture, it does not change and is stable. In order to prevent the hydration reaction of the active CaO existing inside the inorganic film, as described above, (a) the generated inorganic film is stable to moisture and (b) the surface of the particles containing CaO. However, it is an important factor that the film is covered with this stable inorganic film, and (c) the film composed of this inorganic film is not porous and is a defect-free film without cracks or peeling.
[0042]
　With respect to the above (b), at least the surface of the CaO crystal of the particles containing the CaO component can be uniformly coated by the method described above.
[0043]
　The film thickness to be generated is important for the defects of the coating film (c).
　As a result of examining the film thickness using each inorganic compound produced in the present invention, the thickness should be 0.1 μm or more and 15 μm or less in order to obtain a good film having excellent digestibility and no cracks or peeling. It is necessary to have, preferably 0.5 μm or more and 5 μm or less. If the thickness of the coating film is less than 0.1 μm, it becomes difficult to form a continuous coating layer, the coating becomes continuous, and digestibility deteriorates. In addition, if the coating is thicker than 15 μm, cracks and peeling of the coating are likely to occur due to the difference in the coefficient of thermal expansion between the particles and the coating, and the thickness of the void layer becomes smaller, resulting in a decrease in digestibility and heat. There is a possibility that the swelling will be large.
[0044]
　Regarding the defect-free formation of the coating film (c), as described above, the digestibility is greatly improved by setting the thickness of the coating film to 0.1 μm or more and 15 μm or less.
　However, in more severe conditions, for example, in an environment where the film is left in a hot and humid environment for a long period of time, the hydration reaction may gradually proceed due to minute defects existing in the coating film. In such a case, it is also possible to improve the digestibility by reacting with carbon dioxide gas to form a CaCO 3 film on the particle surface (hereinafter referred to as carbonation treatment). In this case, it is necessary to heat-treat within the temperature below the temperature at which calcium carbonate (CaCO 3 ) decomposes. The reason for the improvement in digestibility is that part of the CO 2 that has penetrated through the inorganic film defect produces calcium carbonate on the surface of the CaO-containing particles to prevent digestion, and part of the CaO that constitutes the film is part of it. It is considered that this is because calcium carbonate is generated around the openings in the coating by reacting with CO 2 to reduce or eliminate the coating defects.
[0045]
As a result, the weight ratio of such a CaCO 3 coating 　present in the refractory needs to be about 0.1% by mass or more and about 2.5% by mass or less.
　If the amount of CaCO 3 is less than 0.1% by mass, the effect is less likely to appear, and if it exceeds 2.5% by mass , the molten steel in the mold due to the generation of CO 2 during preheating or casting depending on the preheating conditions before casting. It is not preferable because it may cause operational problems such as boiling phenomenon in which the surface level fluctuates greatly and splash in the initial stage of pouring.
[0046]
　From the viewpoint of reducing the amount of thermal expansion, the thicker the void layer around the fire-resistant raw material particles, the better, and it is preferable to form the void layer on the surface of all the fire-resistant raw material particles having a larger thermal expansion than carbon. .. However, since the formation of the void layer on the surface of the fire-resistant raw material particles causes the material strength to decrease, it is necessary to adjust the thickness of the void layer while balancing the amount of thermal expansion with the strength and damage.
[0047]
　The ratio of the void layer thickness to the particle size (void layer thickness ratio per particle: MS value (microspace value)) is smaller for larger particles and larger for smaller particles. Therefore, knowing the MS value of the coarse particles means knowing the lower limit of the void layer thickness ratio per particle in the refractory structure, and it is possible to evaluate the thermal impact resistance of the refractory. It becomes.
[0048]
　The MS value referred to here is the ratio of the void layer thickness L between the particles and the carbonaceous matrix to the coarse particle diameter D (the total void layer thickness on both sides of the particles is L), and is described below. Obtained from the formula of.
　MS = L / D x 100 (%)
[0049]
　The method of calculating the void layer thickness ratio MS value (%) on the particle surface performed by the present inventors is shown below.
　In microscopic microstructure observation of refractories, 10 coarse particles are selected in descending order of particle size, and the largest circle that touches the contour of each particle and is included is drawn in the plane of each particle, and an arbitrary line passing through the center is drawn. .. Further, using that line as a reference, three more lines having a 45 ° pitch passing through the center of the circle are drawn, and a total of four lines are drawn for each particle. After that, the length between the contour points at both ends of the particle on each line of the particle is set to D1, D2, D3, D4, and the total thickness of the void layer existing at the particle interface at both ends on each line is set. Measure as L1, L2, L3, L4, respectively. Using the numerical values ​​obtained from these four lines, MS1, MS2, MS3, and MS4 calculated by the above formula are calculated respectively, and the average value of these numerical values ​​is used as the void layer thickness ratio of one particle, that is, the MS value. calculate. The MS values ​​of the 10 particles selected in advance are calculated by the above method, and they are averaged to obtain the MS value of the refractory structure.
[0050]
　The reasons for ordering the particles in descending order are as follows.
　The volume change due to thermal expansion of the raw material particles in the refractory structure has a large effect on the thermal shock resistance, that is, the larger the particles, the larger the volume / length change due to the expansion. Therefore, it is necessary to calculate the MS value as an index for adjusting and evaluating the thermostable impact resistance for large raw material particles in the refractory structure.
[0051]
　The thickness of the void layer on the particle surface, which has the effect of reducing expansion and is well-balanced in terms of strength, corrosion resistance, and wear resistance, is 0. The thickness of the void layer on the surface of the maximum particle size is 0. It is confirmed that it is 05% or more and 1.5% or less. Since there are two void layers on both sides on the particle surface, the MS value, which is the ratio of the void layer thickness on both sides to the maximum particle diameter shown above, is 0.1% or more and 3.0% or less. Occasionally, an improvement effect is recognized in terms of physical properties.
[0052]
For example, the coefficient of thermal expansion of the raw material particles (aggregate particles) of 　the CaO-ZrO 2 composition is maximum at CaO = 60% by mass and 1.5% at 1500 ° C. If the coefficient of thermal expansion of the carbonaceous matrix portion surrounding the particles at 1500 ° C. is estimated to be 0.4%, the difference is 1.1%. Since the casting temperature in continuous steel casting is around 1500 ° C, in order for the expansion allowance of the particles to fill the voids and not disappear at 1500 ° C, 1500 if the voids are 1.1% or more of the particle size. Highly expanded aggregates up to ° C will not come into contact with the carbonaceous matrix.
　As a result, the macroscopic thermal expansion of the refractory up to 1500 ° C is dominated by the expansion of the carbonaceous matrix and does not depend on the conventional addition rule of chemical components, resulting in remarkable low expansion characteristics. It becomes possible to show. Therefore, from the viewpoint of the amount of thermal expansion, each particle can be reduced in expansion by having a larger coefficient of thermal expansion (expansion allowance). Furthermore, in order to achieve such low expansion characteristics, it is necessary for the carbonaceous matrix to be three-dimensionally continuous, and it is desirable that the particles to be applied have a particle size distribution that does not contain a large amount of fine powder.
[0053]
　In the calculation, an MS value of 1.1% is sufficient as described above, but in an actual refractory structure, the balance between strength and coefficient of thermal expansion is up to a slightly larger MS value (3.0%). The present inventors have confirmed that it is an area where the above can be taken. When the MS value exceeds 3.0%, the above-mentioned situation occurs everywhere in the microstructure at the casting temperature level, which lowers the macroscopic material strength and deteriorates corrosion resistance and wear resistance. Deteriorate physical properties. When the MS value is less than 0.1%, the mechanical strength is good, but the low expansion effect cannot be obtained.
[0054]
　In order to control such an MS value, as described in (c) above, basically one or more of B 2 O 3 , TIO 2 , P 2 O 5 , and V 2 O 5 are selected. The thickness of the inorganic film may be adjusted by adjusting the content of the components.
[0055]
　As described above, by forming a void layer around the fire-resistant particles which are the CaO-ZrO 2 composition containing free CaO in the refractory structure, the fire resistance which is the CaO-ZrO 2 composition containing free CaO is formed. Since it is possible to reduce the coefficient of thermal expansion of refractories containing refractory particles and overcome the weaknesses in heat impact resistance due to the high expansion characteristics of the refractory particles, it can be used in a number of applications including casting nozzles. Can be applied to.
[0056]
The thickness of the void layer around the refractory particles of the CaO-ZrO 2 composition 　containing free CaO is small in the operating temperature range (about 1500 ° C.) due to the expansion of the particles themselves, and the voids are made of steel. There is almost no risk of deterioration of the corrosion resistance and strength reduction of refractories during casting.
[0057]
　These inorganic film forming methods of the present invention are based on the same mechanism as the method shown in Patent Document 2 described above. However, the effect of this approach involves merely free CaO, such as a lime composition or a CaO-ZrO 2 composition with a
　large width of CaO crystals according to the prior art, although having a chemical composition with the same CaO content in the vertical direction. It cannot be realized even by using a CaO-ZrO 2 -containing composition (raw material) of the prior art (specifically, the width of most CaO crystals exceeds 50 μm) . That is, the present inventors have found that it cannot be obtained without using the CaO-ZrO 2 containing composition (raw material) of the present invention. 　The reason is that in the CaO-ZrO 2 containing composition (raw material) containing free CaO of the prior art, the width of the CaO crystal is large, so that it is mainly formed on the surface of the free CaO, and the CaO crystal and the CaZrO 3 crystal . It is considered that this is because the inorganic film between the two cannot be formed or maintained in a continuous and stable state without defects.
[0058]
　Further, the refractory material of the present invention may further contain one or more selected from SiC, metallic Si, and B4C .
　These contribute to the protection of the carbon component or refractory structure by suppressing the oxidation of the carbon component by oxygen and the oxidation / reduction reaction with the oxide. It also has the effect of increasing strength.
　In this case, each content is 10% by mass or less for SiC and 2% by mass or less in total for either one or both of the metal Si and B4C in the chemical composition after heating in a non - oxidizing atmosphere at 1000 ° C. Is preferable.
　For SiC, melting loss (chemical melting loss) increases when it exceeds 10% by mass. For metallic Si and B4C, when the total of either one or both exceeds 2% by mass, the strength improving effect can be obtained. The thermal shock resistance tends to decrease.
The invention's effect
[0059]
The CaO-ZrO 2 composition of 　the present invention can provide a CaO-ZrO 2 composition as a refractory raw material, which is remarkably excellent in digestibility and heat impact resistance . By incorporating the CaO-ZrO 2 composition of
　the present invention into the refractory, it is possible to obtain a CaO-ZrO 2 refractory having a high CaO content, which cannot be obtained with the CaO-ZrO 2 refractory according to the prior art. can. 　In particular, carbon-containing refractories have remarkable digestibility, high corrosion resistance by suppressing self-solubilization, and remarkable thermal impact resistance, while remarkable alumina-based inclusions in molten steel. It is possible to obtain a good adhesion prevention effect. 　By arranging the refractory material of the present invention in a casting nozzle or the like, it is possible to perform stable operation for a long period of time especially in continuous casting of steel in which inclusions such as alumina in the inner holes are likely to occur. can. 　As a result, it can contribute to the improvement and stabilization of steel quality. In particular, it is preferably applied to high-grade steel or the like, which is required to significantly reduce the amount of inclusions.

A brief description of the drawing
[0060]
FIG. 1 is a photomicrograph showing an example of the CaO-ZrO 2 composition of the present invention (CaO = 60% by mass). FIG. 2 is a photomicrograph showing an example of a
conventional CaO-ZrO 2 composition (CaO = 60% by mass).
FIG. 3 is an example of a microstructure photograph obtained by microscopic observation after heat treatment of the refractory of the present invention.
FIG. 4 is an enlarged photograph of a part of the CaO-ZrO 2 composition in FIG.
FIG. 5 shows an example in which the refractory material of the present invention is applied to a casting nozzle body in one form of a dipping nozzle (casting nozzle) to which the refractory material of the present invention is applied.
[Fig. 6] An example of a continuous steel casting facility, showing an installation example of a casting nozzle, etc.
FIG. 7 shows an example in which the refractory material of the present invention is mainly applied to the surface of the casting nozzle in contact with the molten steel in one form of a dipping nozzle (casting nozzle) to which the refractory material of the present invention is applied.
FIG. 8 shows a form of a lower nozzle (casting nozzle) to which the refractory material of the present invention is applied.
FIG. 9 shows a form of a long nozzle (nozzle for casting) to which the refractory material of the present invention is applied.
[Fig. 10] The outline of the rotation test method in molten steel is shown.
[Fig. 11] Shows a test piece for a molten steel medium rotation test, (a) is a front view, and (b) is a plan view.
[Fig. 12] An outline of the method for measuring the adhesion / melting rate in the molten steel rotation test is shown. (A) is a sample before the test, and (b) is a sample after the test (in the case of melting loss).
[Fig. 13] An outline of a molten steel contaminant (change in carbon content) test method for refractories is shown.
[Fig. 14] Shows a test piece for a molten steel contamination (change in carbon content) test of a refractory, (a) is a front view, and (b) is a bottom view.
Embodiment for carrying out the invention
[0061]
　The CaO-ZrO 2 composition of the present invention can be produced by a method including the following steps.
(1) A step of mixing the CaO raw material and the ZrO 2 raw material and heating them to a molten state above the liquidus line in the composition of CaO and ZrO 2
by an electric melting method or the like, (2) From the above-mentioned molten state. A process of cooling to a solid phase temperature at a rate of 10 ° C./sec or higher.
[0062]
　The above-mentioned CaO raw material is a raw material composed of a Ca compound having CaO ≧ 95% by mass or more after heat treatment under the condition of about 1000 ° C. or higher, and for example, excluding unavoidable impurities, the temperature at the time of melting (830 ° C. or higher). One or more selected from CaO compounds such as calcium carbonate or calcium hydroxide that become CaO at temperature), or quicklime can be used.
[0063]
　As the ZrO 2 raw material, one or more selected from unstabilized zirconia (baddeleyite), fully stabilized zirconia, and partially stabilized zirconia can be used.
　Of these, the cheapest unstabilized zirconia (baddeleyite) is preferable from the viewpoint of raw material cost.
　When fully stabilized zirconia or partially stabilized zirconia is used, since the target product is a CaO-ZrO 2 composition, a raw material using CaO as a stabilizer is preferable. For example , those using Y2O3 or MgO as a stabilizer can also be used, but components containing unavoidable impurities other than the CaO component and the ZrO2 component contained in the composition of the present invention (hereinafter, these are used ) . It is preferable to set the raw material composition so that the amount of (generally referred to as “impurity”) is about 6% by mass or less, preferably about 3% by mass or less. If these impurities and the like increase, the digestibility and the like of the CaO-ZrO 2 composition may decrease. 　As these ZrO 2 raw materials, in addition to those that have been crushed and sized independently, commercially available sandy ones can also be used.
[0064]
　The size (particle size) of each starting material is preferably 10 mm or less, more preferably about 3 mm or less.
　However, for the purpose of increasing the fluidity at the time of charging into an electric furnace or the like, it is also possible to use a fine powder raw material having a size of 3 mm or less formed into larger secondary particles into pellets having a size of 10 mm or less.
　If the grain size of the raw material exceeds 10 mm, it takes a long time to melt and the power consumption tends to increase, resulting in a decrease in productivity and an increase in production cost. It is preferable to use particles as small as possible from the viewpoint of avoiding a decrease in productivity and an increase in production cost, but the minimum particle size may be determined comprehensively in consideration of other factors such as digestion and dust generation. ..
　The CaO raw material has a relationship with the melting time and temperature, but the size of the CaO raw material tends to affect the width of the CaO crystal, and the smaller the CaO raw material, the easier it is to reduce the width of the CaO crystal. Therefore, it is preferable that the CaO raw material is, for example, about 3 mm or less and as small as possible.
[0065]
　When the cooling rate from the molten state to the solidus temperature is small, the size (width) of the CaO crystals of the obtained CaO-ZrO 2 composition becomes large, and the area exposed on the surface of the composition becomes large, so that the resistance to resistance is large. The size (width) of CaO crystals can be reduced to about 50 μm or less by cooling from the molten state, which causes deterioration of digestibility, to the
　solidus phase temperature at a rate of 10 ° C./sec or more. However, the temperature difference between the inside and the outside or the cooling surface and the inside, that is, the difference in the cooling rate, occurs depending on the size of the melting equipment and the melting unit (size of the melting bath). It is preferable that the cooling rate is as high as possible.
　The specific method of quenching is not particularly limited. For example, a method of pouring the melt on an iron plate and quenching, a method of casting into a cooling mold having a gap, and a method of quenching the melt using an atomizer. , The equipment structure and equipment can be arbitrarily selected according to the characteristics required as a raw material, such as the method of blowing off the melt with compressed air.
　The temperature measuring method for knowing the cooling rate may be any measuring method that can be appropriately used. For example, a method of measuring the cooling rate of an object from the molten state to solidification by using a non-contact thermometer such as infrared thermography, an optical fiber thermometer, a thermoelectric pair, etc., and the average cooling rate by CAE analysis based on those data. Can be estimated by calculation.
　In the field, the following simple method can also be adopted.
　For example, when casting in a cooling mold, the temperature of the melt is measured in advance, cast in a cooling mold container, and the time when the object is no longer fluid in the cooling container is determined. It is regarded as the time when the temperature of the solid phase line is reached, and the value obtained by subtracting the temperature of the solid phase line from the temperature of the melt is divided by the time from the time of outflow to the time when the fluidity disappears, and the value is regarded as the cooling rate. ..
[0066]
　The obtained CaO-ZrO 2 composition is pulverized and sized to a predetermined particle size composition.
　The CaO-ZrO 2 composition after sizing must be stored and used in a state where it is not exposed to water or high temperature and humidity. In addition, carbonation treatment can be performed if necessary.
[0067]
　As described above, in order to reduce the coefficient of thermal expansion of the refractory of the present invention and reduce the risk of thermal shock fracture during preheating and casting and fracture due to crushing, a void layer can be formed around the particles. The formation of the void layer can be promoted by subjecting the CaO-ZrO 2 particles to a surface treatment in advance. The coating layer on the particle surface preferably has a coating layer having a predetermined thickness such as a hydrated layer, a chloride layer, and a carbonated layer generated by a chemical reaction with CaO. Specifically, the hydrate layer or chloride can be obtained by contacting the surface of CaO-ZrO 2 with a gas containing water or water for a predetermined time, or by contacting the surface with an acid, an alkaline solution or a gas. A material layer or a carbon oxide layer is formed to a predetermined thickness.
[0068]
　The refractory material of the present invention contains the CaO-ZrO 2 composition of the present invention as a main raw material, but as described above, the zirconia-based raw material having a smaller CaO content than the CaO-ZrO 2 composition of the present invention. Alternatively, an unstabilized zirconia raw material or a CaO-based raw material such as dolomite clinker may coexist.
[0069]
　The refractory of the present invention can be produced by the same method as the general method for producing a refractory containing CaO, as in the preparation of the sample of the examples described later. For example, a binder is added to the CaO-ZrO 2
composition 　as a refractory raw material (refractory particles) to adjust the kneaded clay to a state suitable for molding. The clay is CIP (Cold Isostatic Pressing). After molding at a temperature of about 300 ° C. or lower and drying at a temperature of about 300 ° C. or lower, heat treatment is performed in a non-oxidizing atmosphere of about 800 ° C. or higher and about 1200 ° C. or lower. In addition, carbonation treatment can be performed if necessary.
[0070]
　Further, the refractory of the present invention can contain one or more oxides selected from B 2 O 3 , TiO 2 , P 2 O 5 and V 2 O 5 , but the raw material thereof is B. , Ti, P, V respective oxides, or each hydrate, etc., one or more selected from each of them can be used. For example, diboron trioxide and borate ester can be used as
　a suitable B2O3 source , and sodium tetraborate, potassium metaborate and the like can also be used.
　As the TiO 2 source, titanium oxide or the like, an organic titanium compound or the like can be used.
　As the P 2 O 5 source, a commercially available general product can be used.
　V 2 O 5Vanadium oxide can be used as the source.
[0071]
One or more oxides selected from 　these B 2 O 3 , TiO 2 , P 2 O 5 and V 2 O 5 need to be uniformly dispersed around the particles containing CaO without segregation. .. As a method, it is preferable to use these raw materials in a fine powder or liquid state (including emulsion, suspension, etc.).
[0072]
　As a carbon source, a carbon raw material having a bonding function (hereinafter, also simply referred to as “carbon raw material for bonding”) can be used. As the carbon raw material for bonding, a phenol resin, a furan resin, a pitch resin, a tar-based resin, or the like, which has a high proportion of carbon remaining as a connective tissue after firing in a non-oxidizing atmosphere, is preferable. As a raw material, a raw material that is liquid at room temperature or solid at room temperature that softens or liquefies as the temperature rises can be used.
　In addition to these carbon raw materials for bonding, solid carbonaceous raw materials can be optionally used. As these solid carbonaceous raw materials, fibrous carbonaceous raw materials such as carbon fiber can be used in addition to particles such as graphite and carbon black.
　However, these carbonaceous raw materials are carbon raw materials for bonding so as to be 2% by mass or more and 30% by mass or less in proportion to the fire resistant material at the product stage, that is, in the chemical composition after heating in a non-oxidizing atmosphere at 1000 ° C. Amount obtained by adding the ratio of disappearing components (that is, the ratio of the portion excluding the ratio of residual carbon), the disappearing ratio of solid carbon raw materials (heat reduction of impurities, etc.) to the required amount of carbon components as a refractory material. Therefore, it is necessary to add it to the clay.
[0073]
In order to uniformly disperse the raw materials that become B 2 O 3 , TIO 2 , P 2 O 5 or V 2 O 5 　in the kneading of clay around the CaO-ZrO 2 composition particles, they are made into liquid or fine particles. It is preferable to add and knead the raw materials to be B 2 O 3 , TIO 2 , P 2 O 5 or V 2 O 5 so as to be in direct contact with the CaO-ZrO 2 composition particles.
[0074]
　When the refractory of the present invention contains one or more oxides selected from B 2 O 3 , TiO 2 , P 2 O 5 and V 2 O 5 , the CaO-ZrO 2 composition is obtained by the heat treatment. 0.1 μm consisting of a compound of CaO and one or more oxides selected from the B 2 O 3 , P 2 O 5 and V 2 O 5 on the surface of at least the CaO crystal of the object particles. An inorganic film having a thickness of 15 μm or less is formed. The thickness of this inorganic film can be measured by microscopic tissue observation, an X-ray microanalyzer, or the like. The thickness of the inorganic film is B 2 O 3 , TIO 2 , P. It can be controlled by a method such as varying the addition ratio of the raw materials to be 2 O 5 and V 2 O 5 .
[0075]
　The upper limit of the heat treatment temperature is not particularly limited, but it is substantially set to about 1300 ° C., preferably about 1200 ° C. or lower and 800 ° C. or higher, mainly for economic reasons. The maximum heat treatment time of about 6 hours is appropriate from the viewpoint of reaction progress and economy.
[0076]
The digestibility of the CaO-ZrO 2 composition particles having 　the inorganic film formed above can be further enhanced by carbonation treatment.
[0077]
CaCO 3 　produced as a result of this carbonation treatment is carried out so as to be 0.1% by mass or more and about 2.5% by mass or less. If the content of CaCO 3 exceeds 2.5% by mass, a large fluctuation in the molten metal level in the mold due to the decomposition gas of CaCO 3 at the initial stage of casting , that is, a so-called boiling phenomenon becomes severe, which is not preferable. On the other hand, if it is less than 0.1% by mass, the digestibility may decrease.
[0078]
　In order to reduce the coefficient of thermal expansion of the refractory of the present invention and reduce the risk of thermal shock fracture during preheating and casting and fracture due to crushing, the CaO-ZrO 2 composition containing a free CaO component is described above. It is possible to form a structure in which a void layer having an MS value (%) of 0.1% or more and 3.0% or less is formed between the object particles and the carbonaceous matrix.
[0079]
In order to form a void layer on the surface of the CaO-ZrO 2 composition 　containing a free CaO component, the thickness of the pretreatment layer on the surface of the CaO-ZrO 2 composition is adjusted, that is, the raw material stage or production is performed on the surface . At the heat treatment stage of the process, a method of contacting these particles with a gas containing water or water for a predetermined time, or contact with an acid or alkaline solution or gas, or contact with carbon dioxide gas causes a hydrate layer or chloride. It is also possible to form a layer or a carbon oxide layer with a predetermined thickness. Alternatively, the same effect can be exhibited by a method in which a hydroxide or a carbonic acid compound is mixed in advance in the refractory structure and a compound layer is formed on the CaO surface in a heat treatment process such as a manufacturing stage or an operation stage. ..
[0080] [0080]
　The predetermined thickness is not constant, and is a component for forming the coating layer in order to appropriately adjust the thickness of the voids with respect to the size of the particles forming the coating layer on the surface so as to have the MS value. Set individually according to specific design conditions, taking into consideration the degree of expansion / contraction characteristics associated with different reactions.
[0081]
The coating layer (hydrate layer, carbonic acid oxide layer, etc.) on the surface of the 　CaO-ZrO 2 composition is decomposed during the heat treatment, and the portion where this layer was present is formed as a porous layer. Become. Furthermore, since the decomposed portion of these coating layers is porous and active, it is highly reactive with components such as B 2 O 3 , P2 O 5 , and V 2 O 5 , depending on the compound with these components. Form a film. These coatings become densified during the reaction or formation stage, and as a result of the densification, the volume of the portion shrinks. At the stage where the heat treatment is completed in this way, a certain range of voids is formed between the coating film formed on the surface of the CaO-ZrO 2 composition particles having high thermal expansion characteristics and the matrix structure mainly composed of carbonaceous components. It will be formed. 　The present inventors peculiar to the CaO-ZrO 2 composition containing the narrow CaO crystal of the present invention, and the formation of such a uniform film is a phenomenon peculiar to the CaO-2 composition having a wide width of the prior art. It was found that it did not occur in the CaO-ZrO 2 composition contained.

That is, in the case of the CaO-ZrO 2 composition 　containing the narrow CaO crystal of the present invention, such a film is not formed only on the surface of the CaO crystal of the particles, but is formed in the eutectic structure with the CaO crystal. It was found that it is continuously formed on the surface of CaO / ZrO2 crystals. On the other hand, in the CaO-ZrO 2 composition containing CaO crystals having a wide width in the prior art, the CaO-ZrO 2 composition is formed only on the surface of the CaO crystal in an unstable manner (fragmented) and easily falls off. A refractory made from a CaO-ZrO 2 composition containing thick CaO crystals cannot enhance its digestibility.
　Although this mechanism is not always clear, by increasing the cooling rate during the production of clinker, CaO / ZrO2 crystals and CaO crystals are arranged in an alternating finely symbiotic structure, and CaO is formed. -Considering the fact that the CaO content inside ZrO 2 is slightly higher than the theoretical composition, which was discovered by the present inventors, the high-temperature melt solidified in an overcooled state, resulting in a CaO-rich composition. Therefore, as a result of the presence of excess CaO in the CaO / ZrO 2 crystal, the diffusion of Ca ions in the crystal is facilitated, and a film is formed on the surface of the CaO / ZrO 2 crystal layer as well. Further, it is considered that a continuous film is formed with the film on the surface of the CaO crystal layer.
[0082]
　The thickness of the void layer, that is, the thickness of the coating layer formed on the initial particle surface, is adjusted by changing the concentration, treatment temperature, treatment time, pressure, etc. of the gas used as a treatment agent such as carbon dioxide gas and water vapor. It can be carried out.
[0083]
　Further, the refractory material in which voids are formed on the surface of the particles containing the CaO component and then a film is formed with the oxide of B 2 O 3 , TIO 2 , P 2 O 5 or V 2 O 5 is also formed. ， Can be carbonated. As a result, it is possible to provide voids around the particles containing the CaO component and also to provide a strong CaO-based protective film, which is not only extremely excellent in heat impact resistance and cracking resistance, but also in digestibility. A refractory material containing extremely excellent CaO can be obtained.
[0084]
　By arranging the refractory of the present invention obtained as described above in a part or all of the region in contact with the molten steel, the adhesion of non-metal inclusions such as alumina derived from the molten steel to the surface of the refractory is suppressed. Therefore, it can be suitably applied to casting nozzles.
[0085]
　In FIG. 5A, the refractory material 20 of the present invention according to any one of 6 to 11 is arranged as a single layer on the back surface side from the surface in contact with the molten steel in a part of the region of the portion in contact with the molten steel. An example of a dipping nozzle (casting nozzle) is shown. In FIG. 5A, if the refractory material 20 of the present invention is also arranged in the powder line material 21 portion, the refractory material of the present invention is applied to the entire region of the portion in contact with the molten steel from the surface in contact with the molten steel to the back surface. It is a dipping nozzle (casting nozzle) arranged as a single layer on the side. Although FIG. 5A shows an example of a cylindrical shape, the casting nozzle to which the refractory of the present invention is applied is not limited to such a cylindrical shape, and is mainly as shown in FIG. 5B, for example. It can be applied to various shapes of casting nozzles, such as flat, elliptical, funnel-shaped (funnel-shaped with an expanded upper part) used for casting thin slabs, without being limited by the shape of the nozzle. ..
　Further, FIG. 5 (c) shows an example of a dipping nozzle having a function of blowing gas into molten steel from a part of the inner hole portion (inner hole wall surface) of the dipping nozzle of FIG. 5 (a). In this example, a highly breathable refractory 22G (hereinafter, also simply referred to as “breathable refractory”) is arranged in a part of the inner hole. The material of the refractory refractory for ventilation 22G can be a general alumina-graphite refractory for ventilation, and a material having improved porosity, air permeability, etc. while maintaining the refractory composition of the present invention. You can also do it. The gas is supplied to the molten steel not only from the dipping nozzle as in the example of FIG. 5C, but also from other parts in the molten steel distribution path such as the upper nozzle and the sliding nozzle located above the immersion nozzle. It can be carried out.
[0086]
　Casting nozzles to which the refractory of the present invention can be applied or are suitable to be applied include tundish nozzles (including upper nozzles, open nozzles, etc.), intermediate nozzles, and flow control nozzles (particularly), in addition to immersion nozzles. Inner hole, etc.).
　For example, the left side of FIG. 6 shows an example in which the nozzle portion as a molten steel distribution path when discharging molten steel from the casting container is an exterior type in a structure composed of a plurality of casting nozzles, and the immersion nozzle is an exterior type. The refractory material of the present invention includes not only the immersion nozzle F but also molten steel of various nozzles such as the upper nozzle A, the sliding nozzle plate B, the lower nozzle C, and the long nozzle D of the structure composed of a plurality of casting nozzles. It can be applied by arranging it on a part or all of the surface in contact with the surface. It can also be applied to a so-called interpolated immersion nozzle (right side in FIG. 6) having a structure in which a nozzle portion as a discharge path is integrated, a so-called open nozzle that is not immersed in molten steel, and the like. Further, it can be applied as a stopper E that is located above the nozzle portion and performs a flow rate of molten steel or opens and closes, and a refractory material G for lining a molten steel container.
[0087]
　In the case of a nozzle having a single-layer structure, the risk of cracking can be reduced, and a simple manufacturing method can be adopted. In the manufacture of such a single-layer casting nozzle, the target area in the CIP molding mold may be filled with the refractory clay of the present invention as a single layer, based on the above-mentioned manufacturing method.
　The location and degree of adhesion of non-metal inclusions such as alumina to the surface of refractory varies depending on individual operating conditions. Therefore, the "partial" or "whole" region of the part that comes into contact with the molten steel is determined by selecting the part that most wants to suppress adhesion for each individual operating condition, and is fixed. It's not something like that. Therefore, the "partial" or "whole" area is a matter that can be arbitrarily determined.
[0088]
　FIG. 7 shows that the refractory material 20 of the present invention is arranged on a part or all of the surface in contact with the molten steel, and the refractory material (powder line material 21 and the main body) having a composition different from that of the refractory material 20 of the present invention is on the back surface side thereof. An example of a dipping nozzle (casting nozzle) in which a plurality of layers composed of the material 22) are arranged and the plurality of layers are in direct contact with each other and have an integral structure is shown.
[0089]
　As a specific example of the refractory material (powder line material 21 and main body material 22) on the back side, one or more of Al 2 O 3 , SiO 2 , and ZrO 2 or a refractory particle made of a compound thereof and carbon 1 are used. The composition may differ from that of a refractory of more than one species, or a refractory similar to any of the refractories of the present invention, but which is arranged on a part or all of the surface in contact with the molten steel. Examples of the latter include different mass ratios of CaO / ZrO 2 components, different carbon contents, presence or absence of components such as SiO 2 , SiC, and metallic Si, or different amounts, and the particle size composition of the fireproof raw material. There are different things. A casting nozzle having such a structure is particularly effective when high corrosion resistance to powder in a mold is required. In other words, improvements are also made to determinants such as life other than the adhesion of non-metal inclusions.
　Of course, even if the layer of the refractory material 20 on the surface in contact with the molten steel as shown in FIG. 7 and the refractory material installed as another layer on the back surface side thereof are the refractory materials having the same composition as the refractory material 20 of the present invention. It doesn't matter.
[0090]
　In the manufacture of such a multi-layer casting nozzle, based on the above-mentioned manufacturing method, a refractory is placed in a target area in the CIP forming mold at a position of a predetermined thickness in the radial direction from the surface in contact with the molten steel. A void for soil injection is partitioned, the inside (core rod side) is filled with the refractory earth, and the back side is one or more of the above-mentioned Al 2 O 3 , SiO 2 , ZrO 2 or these. It may be filled with refractory particles made of the above compound and one or more kinds of refractory clay made of carbon. After that, before molding, the jig such as a plate used for this partition may be removed and pressure molding may be performed.
[0091]
　8 and 9, respectively, are arranged on a part or all of the surface where the refractory material 20 of the present invention comes into contact with the molten steel, as in FIG. 7, and the refractory material having a composition different from that of the refractory material 20 is on the back surface side thereof. An example of a lower nozzle and a long nozzle, which are formed into a plurality of layers in which a layer made of (main body material 22) is arranged and have an integral structure in a state where the plurality of layers are in direct contact with each other, is shown.

The scope of the claims
[Claim 1]
　The CaO component is contained in an amount of 40% by mass or more and 60% by mass or less, the mass ratio of the CaO / ZrO2 component is 0.67 or more and 1.5 or less, and the eutectic structure of the CaO crystal and the CaZrO3 crystal is contained . A CaO-ZrO 2 composition in which the width of CaO crystals observable in the structure of the cross section is 50 μm or less .
[Claim 2]
The CaO - ZrO2 composition according 　to claim 1, wherein the width of the CaO crystal is 20 μm or less .
[Claim 3]
The first or second claim, wherein a coating of CaCO 3 having a thickness of 0.1 μm or more and 5 μm or less is continuously present on the surfaces of the CaO crystal and the CaZrO 3 crystal on the surface of the 　CaO-ZrO 2 composition. CaO-ZrO 2 composition.
[Claim 4]
　A step of heating the CaO raw material and the ZrO 2 raw material to a molten state above the liquidus line in the composition of the CaO component and the ZrO 2 component, and a rate of 10 ° C./sec or more from the melted state to the solidus temperature. The method for producing a CaO-ZrO 2 composition according to any one of claims 1 to 3, which comprises a step of cooling with .
[Claim 5]
　The CaO raw material is one or more selected from CaO compounds or quicklime that becomes CaO at the temperature at the time of melting, excluding unavoidable impurities, and the size of the CaO raw material is 10 mm or less
　. The ZrO 2 raw material is one or more selected from CaO-stabilized ZrO 2 , CaO partially stabilized ZrO 2 or unstabilized ZrO 2 , and the size of the ZrO 2 raw material is 10 mm or less. The method for producing a CaO-ZrO 2 composition according to claim 4 .
[Claim 6]
A refractory product containing the CaO-ZrO 2 composition according 　to any one of claims 1 to 3, wherein the mass ratio of the
　CaO / ZrO 2 component is 0.5 or more and 2.2 or less. When the total amount excluding the unavoidable components in production is 100% by mass, the total amount of CaO component and ZrO2 component is 65% by mass or more and 98% by mass or less, and the free carbon component is 2% by mass or more and 30% by mass or less. , CaO-ZrO 2 containing refractory.
[Claim 7]
The CaO-ZrO 2 - containing refractory according to claim 6, wherein the mass ratio of the 　CaO / ZrO 2 component is 0.67 or more and 1.5 or less.
[Claim 8]
　The sixth or seventh aspect of the present invention, wherein the content of the free carbon component is 4% by mass or more and 15% by mass or less, and the coefficient of thermal expansion at 1000 ° C. in a non-oxidizing atmosphere is 0.5% or less. CaO-ZrO 2 containing refractory.
[Claim 9]
　The CaO-ZrO contains 0.1% by mass or more and 5.0% by mass or less in total of one or more components selected from 　B 2 O 3 , TiO 2 , P 2 O 5 , and V 2 O 5 . 2. On the surface of at least the CaO crystal of the composition , a compound consisting of CaO and one or more components selected from the above B 2 O 3 , TIO 2 , P 2 O 5 and V 2 O 5 is composed of 0. The CaO-ZrO 2 - containing fireproof material according to any one of claims 6 to 8, wherein an inorganic film having a thickness of 1 μm or more and 15 μm or less is formed .
[Claim 10]
　Claims 6 to 9 in which CaCO 3 exists in contact with at least a part of the inorganic film, and the content of CaCO 3 is 0.1% by mass or more and about 2.5% by mass or less. The Refractory containing CaO-ZrO 2 according to any one of the above items.
[Claim 11]
It further contains one or more selected from 　SiC, metallic Si, and B 4
C 　, 10% by mass or less for SiC, and 2% by mass or less in total for either one or both of
　metallic Si and B 4 C. The CaO-ZrO 2 -containing refractory according to any one of claims 6 to 10 .
[Claim 12]
The CaO-ZrO 2 -containing refractory according 　to any one of claims 6 to 11 forms a single layer on the back surface side from the surface in contact with the molten steel in a part or all of the region in contact with the molten steel. Placed casting nozzle.
[Claim 13]
The CaO-ZrO 2 - containing refractory according 　to any one of claims 6 to 11 is arranged in a part or all of the surface of the surface in contact with the molten steel, and the back side thereof contacts the molten steel. A casting nozzle having a plurality of layers in which a layer made of a refractory having a composition different from that of the refractory arranged on a part or all of the surface is arranged.
[Claim 14]
　The casting nozzle according to claim 12 or 13, wherein a part of the inner hole is provided with a layer made of a refractory material for blowing gas.