WO2021085325A1 - CaO-ZrO2組成物,CaO-ZrO2組成物の製造方法,CaO-ZrO2含有耐火物及び鋳造用ノズル - Google Patents
CaO-ZrO2組成物,CaO-ZrO2組成物の製造方法,CaO-ZrO2含有耐火物及び鋳造用ノズル Download PDFInfo
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Definitions
- the present invention CaO-ZrO 2 composition special composition and structure, and then the production side method of CaO-ZrO 2 composition, as well as suppressing the alumina deposition occurring molten steel particularly during continuous casting, such as aluminum-killed steel, adverse 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”).
- Alumina-based inclusions in molten steel have the property of depositing on the surface of refractories due to physical contact and chemical action with the molten steel, 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.
- alumina-based inclusions in molten steel are deposited in the inner holes of casting nozzles such as immersion nozzles and discharge holes that have a large effect on the flow of hot water in the mold, and their initial shape changes. When it comes, the molten steel does not flow evenly in the mold, and the so-called drifting may cause mold powder, air bubbles, etc.
- compositions 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.
- alumina is to be removed by flowing down and floating as a compound having a low melting point.
- Patent Document 1 discloses a refractory containing a dolomite composition as a CaO source.
- 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 (causing a so-called digestion phenomenon).
- Ca (OH) 2 calcium hydroxide
- 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).
- CaO (lime) has a large thermal expansion, refractories containing a large amount of CaO component are likely to be destroyed by thermal shock or static stress due to the large thermal expansion in addition to digestion.
- Patent Document 2 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.
- 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.
- a slag phase containing ZrO 2 as a low melting point phase is generated by the 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 adhesion performance cannot be ensured due to the influence of the steel type and operating conditions.
- An object of the present invention is to provide a ZrO 2 -CaO-C based refractory containing free CaO, with significant digestion resistant, to suppress self-fluxing, i.e. while providing corrosion resistance, high and to provide a ZrO 2 -CaO-C-based refractory material can be maintained over a long time-adhere. Further, ZrO 2 -CaO composition and its production method as refractory material for imparting the properties to the refractory, and to provide a casting nozzle disposed the refractory.
- the refractory of the present invention is premised on a function of suppressing the adhesion or deposition of oxides (so-called inclusions) derived from molten steel, mainly alumina, which is a deoxidized product of molten steel, on the surface of the refractory during casting. I have to.
- the content of CaO component, CaO amount of CaO ⁇ ZrO 2 is a compound which is not digested (31 wt% ),
- One of the features is to increase CaO to a content of 40% by mass or more.
- 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 CaO components.
- CaO book common / conventional by art method
- 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.
- the content of CaO component also tried to apply this technique with respect to only ZrO 2 -CaO-C refractories of enhanced due CaO clinker added simply applied even refractory to technical Patent Document 2
- the present inventors have also found that the digestibility of a substance cannot be improved.
- the present invention has decided 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-based raw material particles containing CaO (free CaO) exceeding the amount of solid solution in ZrO 2 as the mineral phase is refined and formed on the surface of the ZrO 2-CaO-based raw material particles. CaO portion or free CaO portions of the ZrO 2 -CaO system in raw material particles is exposed to the basic features to reduce the area of a section in contact with the outside. This makes it possible to improve the digestion resistant to prevent hydration of ZrO 2 -CaO-based raw material particles containing free CaO.
- the relative ZrO 2 -CaO-based raw material particles with basic characteristics further it is possible to form a carbonate or inorganic coating and the like, specific to the ZrO 2 -CaO-based precursor particles having the features 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 not existed in the past.
- the ZrO 2 -CaO-based raw material particles having these characteristics by applying the ZrO 2 -CaO-C refractories and nozzles or the like, resistance caused digestion resistant of the refractories and the nozzle, thermal shock resistance, the press-breaking Destructiveness and the like can be improved.
- the present invention describes 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.
- It contains 40% by mass or more and 60% by mass or less of the CaO component, has a mass ratio of the CaO / ZrO 2 component of 0.67 or more and 1.5 or less, contains a eutectic structure of CaO crystal and CaZrO 3 crystal, and contains.
- a CaO-ZrO 2 composition in which the width of CaO crystals that can be observed in the structure of the cross section is 50 ⁇ m or less. 2.
- 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 may be one or more selected from CaO-stabilized ZrO 2, CaO partially stabilized ZrO 2 or unstabilized ZrO 2, the size of said ZrO 2 raw material is 10mm or less , The method for producing a CaO-ZrO 2 composition according to 4 above. 6.
- 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.
- -ZrO 2 containing refractory. 9. Contains one or more components selected from B 2 O 3 , TiO 2 , P 2 O 5 , and V 2 O 5 in total of 0.1% by mass or more and 5.0% by mass or less. A compound of CaO and one or more components selected from the B 2 O 3 , TiO 2 , P 2 O 5 , and V 2 O 5 on the surface of at least the CaO crystal of the CaO-ZrO 2 composition.
- the CaO-ZrO 2- containing refractory according to any one of 6 to 8 above, wherein an inorganic film having a thickness of 0.1 ⁇ m or more and 15 ⁇ m or less is formed.
- CaCO 3 is present in a state of being in contact with at least a portion of said inorganic coating, and the content of CaCO 3 is less than or equal to about 2.5 wt% to 0.1 wt%, either from the 6 of the 9
- the refractory containing CaO-ZrO 2 according to item 1. 11.
- SiC further contain one or more selected from metallic Si, and B 4 C, For SiC, 10% by mass or less, Metal Si, B 4 2 mass% or less in total of either or both for C, CaO-ZrO 2 containing refractory according to any one of the 10 from the 6. 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 regions 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 surface in contact with the molten steel, and the back side thereof is a surface in contact with the molten steel.
- 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 carbon dioxide compounds in the refractory, and stabilizing the chemical components of the refractory by carbonizing the organic binder component. is there. From this point, the heating time is set to the period until the weight change due to heating disappears (the same applies hereinafter).
- the width of the CaO crystal in the CaO-ZrO 2 composition of the present invention is the CaO of the particle in the field of view 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 elongated and thin layers 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 a long and thin 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.
- 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 CaZrO 3 crystals is contained.
- the mass ratio of the CaO / ZrO 2 components it is 0.67 or more and 1.5 or less.
- 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 makes such a composition or the refractory using such a composition extremely low in digestibility.
- 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, an inorganic film or a film of carbon oxide CaCO 3 described later is formed on the surface of CaO crystals in order to improve digestibility and thermal shock resistance.
- the details of the mechanism are unknown, but due to the small width of the CaO crystals exposed on the outer surface of the particulate CaO-ZrO 2 composition, the CaZrO 3 crystals existing between the plurality of CaO crystals on the particle surface It is considered that the interval is also reduced, and the coating of the inorganic or carbon oxide near the boundary of a plurality of CaO crystals is likely to be crosslinked with the coating of the inorganic or carbon oxide near the adjacent CaO crystal boundary. Then, since the film of the inorganic or carbon oxide of the crosslinked structure forms a structure in which the coating of the inorganic or carbon oxide is bonded to the CaO crystal phase like a large number of spikes, it is considered that the stability is also enhanced.
- 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 CaO is easily crystallized as a fine structure and the amount of CaO is around 50%.
- the CaO content must be 40% by mass or more in order to obtain a remarkable adhesion-resistant effect as a refractory ( compared to a CaO-ZrO 2 composition containing no free CaO).
- 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.
- the digestibility of the composition tends to decrease, and since the composition has a high melting point, the meltability at the time of electrofusion decreases, which causes a problem in terms of production. Therefore, the CaO content needs to be 60% by mass or less.
- the width of the above-mentioned CaO crystal is about 20 ⁇ m or less in order to further enhance the effect of suppressing the hydration reaction and the stability of the inorganic or carbide film installed on the surface thereof.
- the thickness of the coating of CaCO 3 is preferably 0.1 ⁇ m or more and 5 ⁇ m or less. The portion where the coating of CaCO 3 is lost during transportation of the CaO-ZrO 2 composition or other handling or kneading with other refractory raw materials as a refractory raw material, regardless of whether it is less than 0.1 ⁇ m or more than 5 ⁇ m. This is because there is a high possibility that
- Refractory of the present invention containing the above-mentioned CaO-ZrO 2 composition uses only CaO-ZrO 2 composition described above as a main raw material, i.e. CaO-ZrO all CaO component and ZrO 2 ingredients 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 components is 0.67 or more and 1.5 or less, which is the same as the CaO-ZrO 2 composition of the present invention. ..
- the refractory of the present invention containing CaO-ZrO 2 composition described above even while using CaO-ZrO 2 composition described above as a main material, for example lime clinker, dolomite other CaO component-containing composition Or, other zirconia component-containing compositions such as unstabilized zirconia, partially stabilized zirconia, stabilized zirconia, and zirconia can also be contained.
- the mass ratio of the CaO / ZrO 2 component is 0.5 or more and 2.2 or less, excluding the components unavoidable in production.
- the total amount when 100% by mass, the total amount of CaO component and ZrO 2 component is 98 wt% or less than 65 wt%.
- 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, the mass ratio of CaO / ZrO 2 component in the refractory is more than 2.2, may CaO component is digested increases. Further, when the other ZrO 2 component is contained, there is a high possibility that the other ZrO 2 component reduces the poor adhesion.
- the amount of the other ZrO 2 component should be less than or equal to the extent that the difficult adhesion is not lowered. Because it is necessary to do. 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. ..
- the mass ratio of the CaO / ZrO 2 component and 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.
- 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 / ZrO 2 components in the refractory is 1.5.
- the refractory It is not particularly necessary to set an upper limit of the total amount of CaO and ZrO 2 in the refractory from the viewpoint of resistance to adhesion, but when the total amount of CaO and ZrO 2 exceeds 98% by mass, the refractory is bonded.
- the carbon component as a material is too small, the strength as a refractory is insufficient, and the thermal 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. it can.
- 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.
- a total of 0.1% by mass or more and 5.0% by mass or less contains 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 CaO-ZrO 2 composition, one selected from CaO and the B 2 O 3 , TiO 2 , P 2 O 5 , and V 2 O 5 or It is possible to form an inorganic film having a thickness of 0.1 ⁇ m or more and 15 ⁇ m or less composed of a compound containing two or more kinds of components. Since the above-mentioned inorganic film mainly has a function of protecting the exposed surface of the CaO component of the CaO-ZrO 2 composition from hydration, the digestibility can be further significantly improved.
- a void layer (hereinafter, also referred to as “microspace”) is formed mainly due to shrinkage of the inorganic film formed on the exposed surface of the CaO component of the CaO-ZrO 2 composition, 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.
- the coefficient of thermal expansion in a non-oxidizing atmosphere at 1000 ° C. is about 1/2 that of the conventional refractory having a similar chemical composition. It can be 0.5% or less.
- 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.
- 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 thermal shock resistance can be significantly improved.
- 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 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.
- a hydrate layer, a chloride layer, or a coal oxide layer is formed to a predetermined thickness by contact with an acid or alkaline solution or a gas.
- 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.
- the mechanism of formation of these inorganic films and the like will be described in detail. Since the oxygen partial pressure is low inside the refractory containing carbon, oxides with high vapor pressure are easily filled as gas components in the structure, and the gas component is selected on the particle surface containing the CaO component in the structure. To produce 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 points of the oxide used in the present invention are B 2 O 3 : about 480 ° C, TiO 2 : 1840 ° C, P 2 O 5 : 340 ° C, and 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.
- TiO 2 does not have a low melting point like B 2 O 3 and V 2 O 5 , and has a relatively low vapor pressure, so that it cannot be expected to react with CaO components in the form of gas or liquid contact.
- 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.
- the B 2 O 3 and V 2 O 5 has an effect to increase the rate of reaction with TiO 2, by a combination of TiO 2 and B 2 O 3 and V 2 O 5, a high coverage good It becomes possible to promote the formation of the inorganic compound layer.
- these oxides it is possible to use one or more of these oxides. Then, by incorporating these oxides in the refractory so as to be 0.1% by mass or more and 5% by mass in total, a good inorganic compound layer (coating) can be formed on the CaO surface. 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.
- 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.
- (A) The produced inorganic compound is stable to moisture, and (b) the surface of the particles containing the CaO component is uniformly coated with this stable inorganic compound, and (c) from this inorganic compound. It is an important factor that the coating film is not porous and is a defect-free coating without cracks or peeling.
- the inorganic compound produced in the present invention is stable because it does not hydrate thermodynamically.
- the latter method may be an extremely thin (0.05 to 4 ⁇ m) carbonated film or an oil-based film
- the refractory manufacturing process especially the refractory raw material kneading, heat treatment, and processing processes. Part or all of the coating was torn or disappeared, and sufficient digestibility was not exhibited.
- Examples of the inorganic film (compound) formed on the CaO surface in the present invention are as follows. 3CaO ⁇ B 2 O 3 (+ 32.0kJ / mol), 2CaO ⁇ B 2 O 3 (+ 44.1kJ / mol), CaO ⁇ B 2 O 3 (+ 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 2 O 5 (+ 88.2kJ / mol) 3CaO ⁇ P 2 O 5 (+ 236kJ / mol), 2CaO ⁇ P 2 O 5 (+ 280.7kJ / mol)
- the inorganic film formed by the reaction of these oxides with 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.
- the generated inorganic film is stable to water and (b) the surface of the particles containing CaO.
- the film is coated 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.
- At least the surface of the CaO crystal of the particles containing the CaO component can be uniformly coated by the method described above.
- the formed film thickness is important for the defects of the coating film (c).
- the thickness should be 0.1 ⁇ m or more and 15 ⁇ m 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 ⁇ m or more and 5 ⁇ m or less. If the thickness of the coating film is less than 0.1 ⁇ m, it becomes difficult to form a continuous coating layer, the coating becomes continuous, and digestibility deteriorates.
- the coating film is thicker than 15 ⁇ m, cracks and peeling of the coating film are likely to occur due to the difference in the coefficient of thermal expansion between the particles and the coating film, and the thickness of the void layer is reduced, resulting in a decrease in digestibility and heat. There is a possibility that the expansion will be large.
- the digestibility is greatly improved by setting the thickness of the coating film to 0.1 ⁇ m or more and 15 ⁇ m or less.
- the hydration reaction may gradually proceed due to minute defects existing in the coating film.
- it is also possible to improve the digestibility by further reacting with carbon dioxide gas to form a CaCO 3 film on the particle surface (hereinafter referred to as carbonation treatment).
- carbonation treatment 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 It is considered that this is because calcium carbonate is generated around the openings in the coating film by reacting with CO 2 to reduce or eliminate the coating film defects.
- 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 a boiling phenomenon in which the surface level fluctuates greatly and a splash at the initial stage of pouring.
- the formation of the void layer on the surface of the fireproof 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.
- 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 shock resistance of the refractory. It becomes.
- the method of calculating the void layer thickness ratio MS value (%) on the particle surface performed by the present inventors is shown below.
- 10 coarse particles are selected in descending order of particle size, and the largest circle that is in contact with the outline of each particle is drawn in the plane of each particle, and an arbitrary line passing through the center is drawn. .. Further, with reference to that line, three more lines with a pitch of 45 ° passing through the center of the circle are drawn, and a total of four lines are drawn for each particle.
- 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.
- 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 methods, and they are averaged to obtain the MS value of the refractory structure.
- the reasons for ordering the particle size 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.
- the thickness of the void layer on the particle surface which has a low expansion effect and is well-balanced in terms of strength, corrosion resistance, and wear resistance, is 0. It has been 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 observed in terms of physical properties.
- each particle can be reduced in expansion by having a larger coefficient of thermal expansion (expansion allowance). Furthermore, in order to produce such low expansion characteristics remarkably, 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.
- an MS value of 1.1% is sufficient, but in an actual refractory structure, the balance between strength and thermal expansion rate is up to a slightly larger MS value (3.0%).
- the present inventors have confirmed that it is an area in which the above can be taken.
- the MS value exceeds 3.0%, at the casting temperature level, the above-mentioned situation occurs everywhere in the microstructure, which lowers the macroscopic material strength and reduces corrosion resistance and abrasion resistance. Deteriorate physical properties.
- the MS value is less than 0.1%, the mechanical strength is good, but the low expansion effect cannot be obtained.
- one or more types are basically selected from B 2 O 3 , TiO 2 , P 2 O 5 , and V 2 O 5.
- the thickness of the inorganic film may be adjusted by adjusting the content of the component.
- a CaO-ZrO 2 composition containing free CaO refractory tissue By forming the gap layer around the refractory particles is CaO-ZrO 2 composition containing free CaO refractory tissue as described above, a CaO-ZrO 2 composition containing free CaO refractory Since it is possible to reduce the coefficient of thermal expansion of refractories containing refractory particles and overcome the weaknesses in thermal shock resistance due to the high expansion characteristics of the refractory particles, it is used in a number of applications including casting nozzles. Can be applied to.
- the thickness of the void layer around the refractory particles of the CaO-ZrO 2 composition containing free CaO is smaller in the operating temperature range (about 1500 ° C.) due to the expansion of the particles themselves, and these voids are made of steel. There is almost no risk of deterioration such as corrosion resistance and low strength of refractories during casting.
- 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 film and the film cannot be formed or maintained in a continuous and stable state without any defects.
- More refractory of the present invention are SiC, metals Si, and one or more selected from B 4 C may further contain. 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.
- each content is in chemical composition after heating in a non-oxidizing atmosphere at 1000 ° C., 10 wt% for SiC following metals Si, B 4 C for 2 mass% in total of either or both the Is preferable. Melting (chemical erosion) increases more than 10 wt% for SiC, metal Si, although B 4 total of either one or both the C is more than 2 wt%, the strength improvement effect can be obtained, The thermal shock resistance tends to decrease.
- 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 thermal shock resistance. From causing a CaO-ZrO 2 composition of the present invention contained in the refractory, that prior art to obtain a CaO-ZrO 2 refractory of high CaO content which can not be obtained by the CaO-ZrO 2 based refractory material it can. Especially in carbon-containing refractories, it has remarkable digestibility, high corrosion resistance by suppressing self-solubilization, and also has remarkable thermal shock resistance, and remarkable alumina-based inclusions in molten steel. It is possible to obtain a good adhesion prevention effect.
- the refractory of the present invention By arranging the refractory 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 are likely to be generated in the inner holes. it 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.
- An example in which the refractory of the present invention is mainly applied to the surface of the casting nozzle in contact with the molten steel is shown in a form of a dipping nozzle (casting nozzle) to which the refractory of the present invention is applied.
- a form of a lower nozzle (casting nozzle) to which the refractory of the present invention is applied is shown.
- a form of a long nozzle (casting nozzle) to which the refractory of the present invention is applied is shown.
- the outline of the rotation test method in molten steel is shown.
- a test piece for a rotation test in molten steel is shown, (a) is a front view, and (b) is a plan view.
- the outline of the method for measuring the adhesion / melting rate in the rotation test in molten steel is shown.
- (A) is a sample before the test, and (b) is a sample after the test (in the case of melting loss).
- the outline of the molten steel contamination (change in carbon content) test method for refractories is shown.
- the test piece for the molten steel contamination (change in carbon content) test of the refractory is shown, (a) is a front view, and (b) is a bottom view.
- 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 electrofusion method or the like. (2) A step of cooling from the molten state to the solidus temperature at a rate of 10 ° C./sec or more.
- the CaO raw material is a raw material composed of a Ca compound having CaO ⁇ 95% by mass or more after heat treatment under a condition of about 1000 ° C. or higher, and for example, excluding unavoidable impurities, the temperature at the time of melting (830 ° C. or higher).
- CaO compounds such as calcium carbonate or calcium hydroxide that become CaO at temperature), or quicklime can be used.
- 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.
- unstabilized zirconia baddeleyite
- partially stabilized zirconia since the target product is a CaO-ZrO 2 composition, a raw material using CaO as a stabilizer is preferable.
- Y 2 O 3 and or MgO which the stabilizing agent is also usable other than CaO component and the ZrO 2 component contained in the compositions of the present invention, these components (hereinafter contain inevitable impurities).
- the raw material composition is preferably set so that the amount of "impurities") is about 6% by mass or less, preferably about 3% by mass or less. If these impurities and the like increase in a large amount, the digestibility and the like of the CaO-ZrO 2 composition may be lowered.
- these ZrO 2 raw materials in addition to those that have been independently crushed and sized, commercially available sand-like materials can also be used.
- the size (particle size) of each starting material is preferably 10 mm or less, more preferably about 3 mm or less.
- 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 as small particles as possible from the viewpoint of avoiding a decrease in productivity and an increase in production cost, but the minimum particle size may be comprehensively determined 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, the CaO raw material is preferably as small as possible, for example, about 3 mm or less.
- the size (width) of the CaO crystal of the obtained CaO-ZrO 2 composition becomes large, the area exposed on the surface of the composition becomes large, and the resistance is increased.
- the size (width) of CaO crystals can be reduced to about 50 ⁇ m or less by cooling from the molten state to the solidus temperature at a rate of 10 ° C./sec or more, which causes a decrease in digestibility.
- 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 die provided with 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.
- a non-contact thermometer such as infrared thermography, an optical fiber thermometer, a thermocouple, etc.
- CAE analysis based on those data.
- 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 becomes fluid in the cooling container is lost.
- the cooling rate is regarded as the time when the temperature of the solidus line is reached, and the value obtained by subtracting the temperature of the solidus line from the temperature of the melt is divided by the time from the time of outflow to the time when the fluidity disappears. ..
- 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 high humidity. In addition, carbonation treatment can be performed if necessary.
- 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 hydrate layer, a chloride layer, and a carbonated layer generated by a chemical reaction with CaO.
- 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 or alkaline solution or gas.
- a physical layer or a carbon oxide layer is formed to a predetermined thickness.
- the refractory of the present invention wherein at containing CaO-ZrO 2 composition as the main raw material, small zirconia material of CaO content than CaO-ZrO 2 composition of the present invention as described above in the present invention, Alternatively, an unstabilized zirconia raw material or a CaO-based raw material such as dromite clinker may coexist.
- the refractory of the present invention can be produced by the same method as the general method for producing a refractory containing CaO, similar to the preparation of the sample of the examples described later.
- a binder is added to the CaO-ZrO 2 composition as a refractory raw material (refractory particles) to adjust the kneaded soil to a state suitable for molding.
- the soil is CIP (Cold Isostatic Pressing). After molding at a temperature of about 300 ° C. or lower and drying treatment 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.
- 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, respectively, or one or more selected from each hydrate, etc. can be used.
- diboron trioxide and borate ester can be used as suitable B 2 O 3 sources, and sodium tetraborate, potassium metaborate and the like can also be used.
- the TiO 2 source titanium oxide or the like, an organic titanium compound or the like can be used.
- P 2 O 5 source a commercially available general product can be used. Vanadium oxide can be used as the V 2 O 5 source.
- 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.).
- a carbon raw material having a bonding function (hereinafter, also simply referred to as “carbon raw material for bonding”) can be used.
- carbon raw material for bonding phenol resins, furan resins, pitches, tars and the like having a high proportion of carbon remaining as a connective tissue after firing in a non-oxidizing atmosphere are preferable.
- 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.
- solid carbon raw materials can be optionally used.
- a fibrous carbon material such as carbon fiber can be used in addition to particles such as graphite and carbon black.
- 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 refractory material at the product stage, that is, in the chemical composition after heating in a non-oxidizing atmosphere at 1000 ° C.
- the raw material which becomes 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, it is made into a 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.
- the CaO-ZrO 2 composition is obtained by the heat treatment.
- 0.1 ⁇ m composed of a compound of CaO and one or more oxides selected from the above B 2 O 3 , TIO 2 , P 2 O 5 and V 2 O 5 on the surface of at least the CaO crystal of the physical particles.
- An inorganic film having a thickness of 15 ⁇ m 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 can be controlled by a method such as varying the addition ratio of the raw materials to be B 2 O 3 , TIO 2 , P 2 O 5 and V 2 O 5.
- the upper limit of the heat treatment temperature is not particularly limited, but mainly for economic reasons, it is substantially set to about 1300 ° C, preferably about 1200 ° C or less and 800 ° C or higher.
- the heat treatment time at the maximum temperature is about 6 hours, which is appropriate from the viewpoint of the degree of reaction progress and economy.
- the digestibility of the CaO-ZrO 2 composition particles having the inorganic film formed above can be further enhanced by carbonation treatment.
- 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 water 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.
- the structure can be 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 particle and the carbonaceous matrix.
- 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.
- a method of contacting these particles with a gas containing water or water for a predetermined time, or a hydrate layer or chloride by contact with an acid or alkaline solution or gas, or contact with carbon dioxide It is also possible to form a layer or a carbon oxide layer with a predetermined thickness.
- 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. ..
- the predetermined thickness is not constant, and 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.
- the coating layer (hydrated layer, carbonic acid oxide layer, etc.) on the surface of such a 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 , TIO 2 , P 2 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.
- the thickness of the void layer is adjusted by changing the concentration, treatment temperature, treatment time, pressure, etc. of the gas used as a treatment agent for carbon dioxide gas, water vapor, etc. It can be carried out.
- 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.
- 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.
- 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.
- FIG. 5A shows a cylindrical example
- 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 casting nozzles of various shapes, such as flat, oval, and funnel-shaped (funnel-shaped with an enlarged upper part) used for casting thin slabs, without being limited by the shape of the nozzle. ..
- FIG. 5 (c) shows an example of the immersion nozzle having a function of blowing gas into the molten steel from a part of the inner hole portion (inner hole wall surface) of the immersion nozzle of FIG. 5 (a).
- 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 material for ventilation 22G can be a general alumina-graphite refractory material 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 into the molten steel not only from the immersion 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.
- Casting nozzles to which the refractory of the present invention can be applied or are suitable to be applied include a tundish nozzle (including an upper nozzle, an open nozzle, etc.), an intermediate nozzle, and a flow rate control nozzle (particularly), in addition to the immersion nozzle. Inner hole, etc.).
- a tundish nozzle including an upper nozzle, an open nozzle, etc.
- an intermediate nozzle including an intermediate nozzle, and a flow rate control nozzle (particularly), in addition to the immersion nozzle. Inner hole, etc.
- 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 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 also 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 G for lining a molten steel container.
- the target region 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 production method.
- the location and degree of adhesion of non-metallic inclusions such as alumina to the surface of refractories 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.
- 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 side thereof.
- a dipping nozzle casting nozzle
- a plurality of layers made 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.
- 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
- the composition may differ from that of refractories of more than one kind, or refractories similar to any of the refractories of the present invention, but which are arranged on a part or all of the surface in contact with 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.
- 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 refractory materials having the same composition as the refractory material 20 of the present invention. It doesn't matter.
- a refractory is placed in a target region in the CIP forming mold at a position having a predetermined thickness in the radial direction from the surface in contact with the molten steel.
- a gap for soil injection is partitioned, the inside (core rod side) is filled with the refractory clay of the present invention, and one or more of the above-mentioned Al 2 O 3 , SiO 2 , ZrO 2 or these are placed on the back side. It is sufficient to fill the refractory particles made of the above compound and one or more kinds of refractory clay made of carbon.
- a jig such as a plate used for this partition may be removed and pressure molding may be performed.
- 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.
- Example A of CaO-ZrO 2 composition In Example A of this CaO-ZrO 2 composition, the mass ratio of each raw material (starting raw material) of the CaO raw material and the ZrO 2 raw material is changed, and the molten state of the mixture, the presence or absence of free CaO, the width of the CaO crystal, etc. investigated.
- Example A The sample of Example A was obtained under the following conditions.
- the starting material wt%), as a CaO raw material (CaO source), using quicklime size configuration ⁇ 10 mm, as ZrO 2 source, unstabilized zirconia particle size configurations ⁇ 10 mm (approximately ⁇ 3 mm) a (vaterite) It was mainly used, and in some examples, almost completely stabilized zirconia with CaO and almost completely stabilized zirconia with MgO ZrO 2 were used.
- the particle size composition of these CaO-stabilized zirconia and MgO-stabilized zirconia is also ⁇ 10 mm.
- the mixture of the starting raw materials was melted by using an electric furnace, the melting amount was set to about 0.5 tons, the temperature was raised to about 2800 ° C., and the temperature was maintained until a predetermined time specified for convenience.
- the conditions such as temperature, time, and melting amount are the same as those in this example.
- the molten state of the mixture when the molten state is visually observed and a good molten state is obtained within the above-mentioned time, ⁇ (excellent) is obtained, and when the melted state exceeds the predetermined time, the desired molten state is obtained.
- the case where the melting result was acceptable was evaluated as ⁇ (good), and the case where the melting was incomplete was evaluated as ⁇ (impossible).
- the melt was rapidly cooled by a method of spreading the melt into a cooling iron plate having a thickness of about 20 mm so that the thickness of the melt was about 10 mm.
- the cooling rate can be measured up to a temperature of 3000 ° C. While monitoring the melt surface temperature with infrared thermography, the cooling rate is measured by measuring the time until the melt temperature falls below the solidus temperature (about 2260 ° C). Was calculated. The cooling rate in this case was ⁇ 10 ° C./sec (16 ° C./sec to 18 ° C./sec).
- the presence or absence of free CaO is determined by cooling the obtained CaO-ZrO 2 composition to room temperature, sizing it to a particle size of ⁇ 1 mm, and then observing the structure of the particle cross section with a microscope and freeing it in the field of view.
- the case where the CaO crystal was present was evaluated as ⁇
- the case where the free CaO crystal was not present was evaluated as ⁇ .
- the width of the free CaO crystal was evaluated by measuring the width of the free CaO crystal in the particle cross section in the field of view by observing the structure with the microscope.
- the content of free CaO in the composition was calculated from the blending ratio of the starting material.
- the CaO-ZrO 2 composition of the present invention has a lower limit content of the CaO component of 40% by mass and a lower limit mass ratio of the CaO / ZrO 2 component of 0.67, which is contained in the free CaO component. When converted to a quantity, it is 12% by mass. Therefore, the case where the content of free CaO obtained by calculating from the blending ratio of the starting material was ⁇ 12% by mass was evaluated as ⁇ , and the case where ⁇ 12% by mass was evaluated as ⁇ .
- the weight increase rate of the particles sized to ⁇ about 1 mm reached + 1.5% in a constant temperature and humidity (40 ° C., 90 RH%) environment.
- the number of days until this was measured was measured, and the case of ⁇ 1 day, which is the target value, was marked with ⁇ (possible), and the case of ⁇ 1 day was marked with ⁇ (not possible).
- the evaluation results were comprehensively evaluated as ⁇ (pass) when the requirements for the CaO-ZrO 2 composition of the present invention were satisfied, and ⁇ (fail) when any of the requirements was not satisfied. ..
- Table 1 shows the details of each example.
- FIG. 1 shows a micrograph of the CaO-ZrO 2 composition of Example 1. Include eutectic structure of CaO crystalline and CaZrO 3 crystal, and the width of CaO crystalline it can be seen that at 50 ⁇ m or less.
- FIG. 2 shows a micrograph of the CaO-ZrO 2 composition obtained by melting the same mixture of starting materials as in Example 1 and then slowly cooling (cooling rate: less than 10 ° C./sec). ..
- Example 1 contains a eutectic structure of CaO crystals and CaZrO 3 crystals, but it can be seen that the width of most CaO crystals is more than 50 ⁇ m.
- Example 1 in which the ratio of the CaO / ZrO 2 raw material was 60/40, it took a longer time than in other examples until it was sufficiently melted. This means that productivity is likely to decrease and segregation is likely to occur in terms of melting, yield, etc., and caution is required in manufacturing.
- Comparative Example 1 in which the ratio of the CaO / ZrO 2 raw material was 61/39 had a high melting point and could not be sufficiently melted. From these facts, it is considered that 60/40 is appropriate or preferable as the upper limit of the ratio of the CaO / ZrO 2 raw material in the production of the CaO-ZrO 2 composition of the present invention.
- the width of the free CaO crystals in the examples was ⁇ 50 ⁇ m although it was slightly larger in Example 1, and ⁇ 20 ⁇ m in all of the other examples.
- digestibility all of the comparative examples did not reach the target of ⁇ 1 day, whereas all of the examples were able to satisfy the target of ⁇ 1 day.
- Example 5 using CaO fully stabilized zirconia and Example 6 using MgO fully stabilized zirconia the same results as in the example using unstabilized zirconia could be obtained.
- Example B of CaO-ZrO 2 composition > Example B of the CaO-ZrO 2 composition, and Example 2 of Example A of the CaO-ZrO 2 composition to the base, the surface of the CaO-ZrO 2 composition, the CaCO 3 by carbonation process This is an example of investigating the relationship between the thickness of the CaCO 3 coating and the digestibility of the sample on which the coating was formed.
- the particles obtained by the same method as in Example A and sized to ⁇ 1 mm are chemically reacted in a furnace at a constant temperature equal to or lower than the decomposition temperature of calcium carbonate into which CO 2 gas is introduced to reach room temperature. It was a cooling method.
- the thickness of the carbon oxide (CaCO 3 ) coating on the surface of the particles of the CaO-ZrO 2 composition was adjusted by changing the time of residence in the CO 2 gas.
- Example 2 which is a CaO-ZrO 2 composition having no carbonated film but having the characteristics of the present invention, the result of 5 days was also obtained, and it can be used as a refractory material constituting a casting nozzle or the like. I understand. Further, in Examples 7 to 9 in which the carbonic acid oxide film is thick, it can be seen that the number of days until the weight increase rate reaches + 1.5% becomes longer as the thickness of the carbonic acid oxide film increases. Moreover, when the carbon oxide coatings of these examples were observed with a microscope, it was confirmed that the entire particles were continuously covered.
- Comparative Example 4 produced at a cooling rate lower than that of the method of the present invention, in which the cooling rate after melting was ⁇ 10 ° C./sec (8 ° C./sec), was subjected to the same carbonation treatment as in Example 8. Nevertheless, the width of most free CaO crystals exceeds 50 ⁇ m, does not have the structure of the CaO-ZrO 2 composition of the present invention, the formation of the carbon oxide film is non-uniform, and the film is present. There were many discontinuous portions (portions where free CaO crystals were exposed on the surface) even in the portions where the coating was carried out (see Example C of the CaO-ZrO 2 composition described later). The digestibility test results also reflected this, and the number of days was ⁇ 1.
- Example C of this CaO-ZrO 2 composition is based on Example 2 of Example A of the CaO-ZrO 2 composition, and changes the cooling rate after melting, and this cooling rate and CaO-ZrO This is an example of investigating the relationship between the width of CaO crystals of the two compositions and the relationship between them and digestibility.
- the cooling rate was adjusted by controlling the tilting rate and adjusting the thickness of the melt.
- all the samples were not subjected to carbonation treatment.
- the digestibility was determined by the same method as in Example B and the same evaluation criteria.
- Comparative Example 5 produced at a cooling rate of 8 ° C./sec, which is smaller than the method of the present invention, the width of most free CaO crystals exceeds 50 ⁇ m, and the CaO-ZrO 2 composition of the present invention is obtained. It does not have a structure as a product, and the digestibility test results reflect this, and the number of days was ⁇ 1.
- Example D of this CaO-ZrO 2 composition is an example in which the size of the CaO raw material as a starting material of the CaO-ZrO 2 composition is changed and the influence on the width and digestibility of CaO crystals is investigated. ..
- the starting material mass%
- quicklime having a particle size composition of approximately 3 mm or less ( ⁇ 3 mm), ⁇ 3 mm or more and 5 mm or less, 5 mm or more and 10 mm or less, and 10 mm or more (> 10 mm) is used as the CaO raw material (CaO source).
- Unstabilized zirconia (batelite) having a particle size composition of ⁇ 10 mm (approximately ⁇ 3 mm) was used as the two raw materials (ZrO 2 sources), and the mass ratio of CaO raw material / ZrO 2 was set to 50/50. Moreover, in this Example C, all the samples were not subjected to carbonation treatment. The digestibility was determined by the same method as in Examples B and C and the same evaluation criteria.
- Example A of this refractory is an example in which the influence of the CaO / ZrO 2 mass ratio among the chemical components of the refractory on the alumina adhesion and digestibility is investigated.
- Example A of this refractory the CaO-ZrO 2 composition of the present invention having different content ratios of CaO and ZrO 2 was mainly used.
- the width of the free CaO crystals in any of the compositions is ⁇ 50 ⁇ m.
- the amount of carbon in the refractory (total amount of graphite and carbon as a binder) was set to 11.8% by mass, and the CaO / ZrO 2 mass ratio was changed.
- the effect of the CaO / ZrO 2 mass ratio when other CaO-based raw materials and ZrO 2- based raw materials were used in combination with the CaO-ZrO 2 composition of the present invention was also investigated.
- Refractory samples other than Example 23 were subjected to carbonation treatment to form a carbon oxide film having a thickness of 0.5 ⁇ m to 2 ⁇ m on the CaO-ZrO 2 composition of the present invention and other CaO-based particles. did.
- a refractory sample is immersed and rotated in molten steel containing about 0.2% by mass of Al and having an oxygen dissolved oxygen amount [O] of ⁇ 50 ppm at 1540 ° C to 1580 ° C (hereinafter simply "" It is also called “rotation test in molten steel”), the amount of alumina adhering to the surface of the refractory, and the amount of melt damage on the surface of the refractory were evaluated.
- the adhesion rate in the molten steel rotation test was ⁇ 5 ⁇ m / min. ⁇ (excellent, target value), +5 to +10 ⁇ m / min. Or -5 to -10 ⁇ m / min.
- erosion in “corrosion resistance evaluation” means whether the mechanism that caused the damage is erosion due to a chemical reaction (corrosion due to low melting, etc.) or mechanical such as wear. It is used as a concept that comprehensively expresses the situation where the size of the sample after the test is reduced, regardless of whether it is wear due to erosion (so-called erosion / ablation).
- FIG. 10 shows an outline of a molten steel rotation test method
- FIG. 11 shows a test piece for a molten steel rotation test
- (a) is a front view (image)
- (b) is a bottom view.
- test piece 10a held in the lower part of the holder 11 is immersed in the molten steel 13 in the crucible 12.
- test pieces 10a There are four test pieces 10a in a rectangular parallelepiped, and they are fixed to each of the four lower surfaces of the holder 11 of a quadrangular prism.
- the test piece 10a is inserted into a recess provided in the holder 11 of the quadrangular prism via a mortar, and can be removed by pulling it out after the test is completed.
- the upper part of the holder 11 is connected to a rotating shaft (not shown), and the holder 11 is rotatably held with the longitudinal axis as the rotating shaft.
- the holder 11 has a square shape with a side of 40 mm in a horizontal cross section, a length in the longitudinal direction of 160 mm, and is made of a zirconia carbon refractory.
- the test piece 10a has an exposed portion from the holder 11 having a length of 20 mm, a width of 20 mm, and a protruding length of 25 mm. Further, the lower end surface of the test piece 10a is attached at a position 10 mm above the lower end surface of the holder.
- the crucible 12 is made of a cylindrical refractory having an inner diameter of 130 mm and a depth of 190 mm. The immersion depth of the holder 11 is 50 mm or more.
- the crucible 12 is housed in a high frequency induction furnace 14. Although not shown, the upper surface can be covered with a lid.
- the test piece 10a In the rotation test in molten steel, the test piece 10a is preheated by holding the test piece 10a on the molten steel 13 for 5 minutes, and then the test piece 10a is immersed in the molten steel 13 (low carbon aluminum killed steel) to immerse the test piece 10a on the outermost peripheral surface of the test piece 10a. Rotate at an average peripheral speed of 1 m / sec. During the test, aluminum is added to the molten steel 13 to keep the oxygen concentration in the range of 10 to 50 ppm and the temperature in the range of 1540 to 1580 ° C. After 2 hours, the test piece 10a is pulled up and the adhesion / melting rate ( ⁇ m / min) of the test piece 10a is measured.
- the molten steel 13 low carbon aluminum killed steel
- the test piece 10a after the test is removed from the holder and cut in a horizontal plane with respect to the rotation axis (FIG. 12 (b)). On the cut surface, the lengths of 6 points are measured and averaged at a pitch of 3 mm from the end face 10'in the direction of the rotation axis. As shown in FIG. 12A, the lengths of the test piece 10a before the test are measured and averaged in the same manner.
- the adhesion / melting rate (mm / min) is calculated by dividing the value obtained by subtracting the average value (mm) after the test from the average value (mm) before the test by the test time of 120 minutes.
- the digestibility was the same as in Example B, Example C, and Example D of the CaO-ZrO 2 composition, but the weight increase rate was +1 in consideration of storage or distribution as a refractory product.
- the target number of days to reach 5.5% was set to ⁇ 3 days, ⁇ 3 days was evaluated as ⁇ (pass), and ⁇ 3 days was evaluated as ⁇ (fail).
- Comparative Examples 7 and 8 in which the CaO / ZrO 2 mass ratio of the refractory is ⁇ 0.5, alumina adhesion is large and erosion resistance is satisfied, but high alumina resistance is not obtained. You can see that.
- Comparative Examples 9 and 10 in which the CaO / ZrO 2 mass ratio of the refractory is> 2.2, it can be seen that although the alumina adhesion is small, the melting loss is large. Further, in Comparative Example 9 containing quicklime as a CaO source, it can be seen that the refractory is inferior in digestibility even though the refractory is carbonated.
- Example B of this refractory is an example of investigating the influence of the ratio of the carbon component in the chemical components of the refractory on the alumina adhesion, digestibility, and thermal expansion. As the ratio of the carbon component increased or decreased, the effect of the range of the total amount of the CaO component and the ZrO 2 component was also investigated.
- the digestibility test and the alumina adhesion test were based on the same method and evaluation criteria as in Example A of the refractory.
- the coefficient of thermal expansion (%) was measured in a non-oxidizing atmosphere at 1000 ° C., and ⁇ 0.5% was evaluated as ⁇ (target value, good) and ⁇ 0.5% as ⁇ (bad). ..
- the casting nozzle which is the main and important application of the refractory of the present invention, is required to have high thermal shock resistance, and generally, alumina-graphite having a coefficient of thermal expansion at 1000 ° C. of 0.5% or less. Quality is used.
- the refractory material mainly containing the CaO-ZrO 2 composition of the present invention undergoes thermal expansion at the same level as those of the general materials.
- the present inventors have found that the coefficient of thermal expansion is more preferably ⁇ 0.5% in order to obtain a high degree of thermal shock resistance particularly in a casting nozzle, and based on that finding.
- the target value was set to ⁇ 0.5%.
- the case where the refractory that can solve the problem of the present invention is passed is ⁇ , and the unfavorable one can be used (a remarkable effect is not obtained, but a certain improvement effect is obtained).
- the case was marked with ⁇ , and the case of failure was marked with ⁇ .
- the carbon component of the refractory is in the range of 2 to 30 wt%, the total amount of CaO component and ZrO 2 component, ⁇ 65 wt% (64 wt%, Comparative Example 13 containing dolomite as CaO source) Then, it can be seen that the melting loss becomes large.
- the content of the carbon component needs to be 2 to 30% by mass, and 2 to 25 in order to obtain a suitable balance between the alumina resistance and the erosion resistance. It can be seen that the range of mass% is preferable, and the range of 4 to 15 mass% is more preferable. Further, the total amount of CaO component and ZrO 2 component is seen that there must be 65 to 98 mass%.
- the coefficient of thermal expansion (%) under a non-oxidizing atmosphere at 1000 ° C. is smaller than the substantially minimum value of 1.0% for alumina-graphite, which is a general conventional technique in all Examples and Comparative Examples.
- a more preferable target value of ⁇ 0.5% can be obtained when the amount of carbon component is ⁇ 4% by mass (Example 28). That is, it can be seen that the amount of carbon component is more preferably ⁇ 4% by mass from the viewpoint of the coefficient of thermal expansion.
- Example B in which the residual carbon component of graphite and phenol resin was used as the carbon component it can be seen that the larger the amount of carbon component as graphite, the smaller the coefficient of thermal expansion tends to be.
- Example C of this refractory oxides for forming an inorganic film on the surface of the CaO-ZrO 2 composition in the refractory of the present invention are contained, and these oxides have digestibility, alumina adhesion, and the like. This is an example of investigating the effect on thermal expansion.
- oxide diphosphorus pentoxide (P 2 O 5 ), vanadium oxide (V 2 O 5 ), titanium oxide (TIO 2 ), and boron oxide (B 2 O 3 ) were selected.
- the sample was produced in the same manner as in Examples A and B of the refractory, and evaluated by the same method.
- the digestibility was the same as in Examples A and B of the refractory, but in this example, the weight increase rate was increased to + 1.5% in consideration of the significant improvement in digestibility.
- the target (pass) of the number of days to reach is set to ⁇ 3 days, which is the same as in the above embodiment, ⁇ 31 days is ⁇ (excellent), ⁇ 30 days to ⁇ 15 days ⁇ (good), ⁇ 14 days to ⁇ 3. Days ⁇ (possible) and ⁇ 3 days were evaluated as ⁇ (impossible).
- the alumina adhesion test was carried out using the same method and evaluation criteria as in Examples A and B of the refractory.
- the thermal expansion test was carried out using the same method and evaluation criteria as in Example B of the refractory.
- the "x" in the thermal expansion evaluation of this example means that it is not preferable for the general casting conditions of aluminum killed steel and the like.
- Such an example of "x" unfavorable evaluation may be usable and suitable under the operating conditions of steel having an extremely large degree of adhesion of alumina.
- the case where the refractory that can solve the problem of the present invention is passed is ⁇ , and the unfavorable one can be used (a remarkable effect is not obtained, but a certain improvement effect is obtained).
- the case was marked with ⁇ , and the case of failure was marked with ⁇ .
- Example 41 in which the total of the oxide content of Example 35, P 2 O 5 , V 2 O 5 and TiO 2 exceeding 5% by mass alone exceeds 5% by mass, the corrosion resistance It can be seen that there is a tendency for Since these corrosion resistances decrease, that is, the tendency of self-solubilization increases, inclusions may occur depending on the steel type, but it can be used as a refractory when the steel quality is not strict with an emphasis on adhesion suppression. However, in the case of steel grades that dislike the inclusion of inclusions derived from refractories, it can be seen from the results in Table 7 that the content of these oxides is preferably 5% by mass or less, either alone or in total.
- the thermal expansion tends to increase.
- This thermal expansion becomes larger when the film of the compound of oxide and CaO becomes thicker and shrinks when these compounds are produced, that is, the thickness at which the film increases than the thickness of the microspace. This is because it grows larger. Therefore, the thickness of the compound of CaO and one or more oxides selected from the B 2 O 3 , TiO 2 , P 2 O 5 , and V 2 O 5 is 0.1 ⁇ m or more and 15 ⁇ m or less. It is preferable to have.
- the thermal shock resistance is excellent as compared with the conventional technique.
- the content of these oxides is preferably ⁇ 5% by mass. From the results in Table 7, when P 2 O 5 and V 2 O 5 coexist, the same result as when P 2 O 5 , V 2 O 5 and TiO 2 coexist can be obtained. It can be inferred that the content of these oxides is preferably ⁇ 5% by mass when any two of these oxides coexist.
- FIG. 4 shows a photomicrograph of a cross section of the CaO-ZrO 2 composition (same in FIG. 3) used for the refractory of Example 38.
- refractory of the example 38 has a continuous coating on the CaO-ZrO 2 composition surface and a CaO-ZrO 2 composition and the film, there is a gap layer between the carbonaceous matrix You can see that.
- this CaO-ZrO 2 composition contains a eutectic structure of CaO crystals and CaZrO 3 crystals, and the width of the CaO crystals is 50 ⁇ m or less.
- Example D of refractory In Example D of this refractory, the CaO-ZrO 2 composition in the refractory after the firing treatment of the present invention is further carbonated, and the CaCO 3 content in the composition is changed to change the resistance of the refractories. This is an example of investigating the effects on digestibility, alumina adhesion, and thermal expansion.
- the sample was produced in the same manner as in Examples A, B, and C of the refractory, and evaluated by the same method.
- the CaCO 3 content (which almost correlates with the thickness of the CaCO 3 coating) was controlled by changing the carbon dioxide concentration, the treatment temperature, the treatment time, the carbon dioxide pressure, and the like.
- Example D The digestibility, alumina adhesion test, and thermal expansion test were based on the same method and evaluation criteria as in Example C of the refractory. Further, in Example D, CaCO 3 coating state, i.e., whether CaCO 3 film is in contact with at least a portion of said inorganic compound coating, and CaCO 3 in the coating thickness of the ([mu] m) was observed with a microscope .. Further, a refractory sample was immersed in hot metal at 1600 ° C., and the boiling state of the hot metal was visually confirmed (hereinafter, also referred to as "immersion test in hot metal").
- Table 8 shows the content of the refractory compound and the evaluation results.
- Example 46 having a CaCO 3 content of 3.0 mass, the boiling of the hot metal was slightly increased in the immersion test in the hot metal. This is due to the decomposition gas of the carbonic acid component, but this phenomenon may reduce the quality of molten steel in the casting operation or increase the risk during the operation. Therefore, the CaCO 3 content is preferably 2.5 mass or less.
- the CaCO 3 coating was in contact with at least a part of the inorganic compound coating, but in Example 42 having a low CaCO 3 content, a discontinuous portion was partially observed. It was. On the other hand, in Examples 43 to 46, the CaCO 3 coating was in contact with at least a part of the inorganic compound coating in a substantially continuous state.
- the sample preparation method, the evaluation method for alumina adhesion (also serving as corrosion resistance), and the evaluation criteria are the same as in Example D of the refractory.
- the strength was expressed as an index in which the bending strength (2.5 MPa) of Comparative Example 16 was measured by measuring the bending strength of the sample after heat treatment in a non-oxidizing atmosphere at 1000 ° C.
- the case where the refractory that can solve the problem of the present invention is passed is ⁇ , and the unfavorable one can be used (a remarkable effect is not obtained, but a certain improvement effect is obtained).
- the case was marked with ⁇ , and the case of failure was marked with ⁇ .
- SiC it can be seen that the bending strength of any example containing one or more selected from B 4 C and Si metal is high.
- Example 49 having a SiC content of 10% by mass had a slight tendency toward erosion in the alumina adhesion test, and Example 50 having a SiC content of 10.5% by mass had a large erosion. The result was. From this result, it can be seen that the content of SiC is preferably 10% by mass or less in the continuous casting of general aluminum killed steel or the like.
- the content of SiC, the amount of B 4 C and metallic Si alone or combined, or the combined amount of these three exceeds the above-mentioned preferable content, it is not that it cannot be used as a refractory for casting, but that it is extremely adhered to alumina. It can be used in the casting conditions of large steels and by adjusting their content according to the degree, and may rather be suitable for such conditions.
- Example F of this refractory is an example in which the influence of the refractory of the present invention on the quality of molten steel (degree of contamination of molten steel) is evaluated by the change in carbon content in the molten steel in comparison with other materials of the prior art. is there.
- the carbon component in the refractory moves into the steel while immersed in the molten steel.
- the degree appears as a change in the content of carbon components in steel.
- the change in the carbon content in the molten steel was determined by the equipment and sample installation method of FIGS. 13 and 14 according to the same equipment and method of the alumina adhesion test as in Examples A to E of the refractory, and the steel before and after the test. It was obtained by measuring the carbon content in it. Then, the case where the change (increase) in the amount of carbon in the steel was ⁇ 50 ppm was evaluated as ⁇ (good), and the case where the change (increase) in the amount of carbon was ⁇ 50 ppm was evaluated as ⁇ (poor). Moreover, in this Example F, the alumina adhesion test was performed, and the degree of alumina adhesion or the degree of melting damage was also measured.
- Table 10 shows the content of the refractory compound and the evaluation results.
- Example 57 of the present invention it can be seen that the change in the carbon component in the steel is extremely small as compared with any of the materials of the prior art. In addition, this Example 57 is based on the said Example 16. On the other hand, in Comparative Examples 15 and 16 which are oriented toward difficult adhesion in the prior art, the change in the carbon component in the steel is extremely large, and the refractory melt damage in the alumina adhesion test tends to be large. Understand.
- Comparative Example 11 of a general refractory for casting which does not have a difficult-to-adhere function and in Comparative Examples 17 to 19 mainly oriented toward high corrosion resistance, in addition to the extremely large change in the carbon component in the steel, in the alumina adhesion test. It can be seen that the degree of alumina adhesion tends to be large.
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Abstract
Description
近年鋼の高品質化や鋳造用ノズルの高耐用化等の要求がますます高まっていることから,鋳造用ノズルの耐火物へのアルミナ付着を防止すると共に,ノズル構造での改善の他,耐火物損耗量と付着性を極少化させる材質面で種々の方策が試みられている。
フリーのCaOは空気中の水分や直接水分と接触することで,容易に水酸化カルシウム(Ca(OH)2)を生成する(いわゆる消化現象を生じる)。CaOを含む粒子が消化すると,Ca(OH)2が水和する際の体積膨張のため粒内破壊にとどまらず,耐火物組織をも破壊し,構造体としての形状維持が困難となる場合が少なくない。このように単純なフリーのCaOの増量は,製造上だけでなく,保管,輸送,使用時(鋼の鋳造に供した際)に重大な問題を惹き起こす原因となる。
またCaO(ライム)は熱膨張が大きいことから,多量にCaO成分を含有する耐火物では,消化以外にもその大きな熱膨張に起因する熱衝撃又は静的応力による破壊等が生じ易い。
この特許文献2の技術では消化や熱膨張に起因する破壊等に対しては大幅に改善することができるが,鋳造時間,鋼種等の操業条件によっては,依然,耐食性や強度に起因する問題が生じることがある。
例えば特許文献3には,CaO:5~40質量%,SiO2:2~30質量%,ZrO2:35~80質量%で,カーボン:5質量%未満(ゼロを含む)であるCレス材質の耐火物が開示されている。
しかし,この特許文献3のような耐火物は,消化しないことが前提となるため,例えばCaO-ZrO2系の場合にCaO含有量を最大にするためには,フリーのCaOを含有しないCaO・ZrO2化合物とせざるを得ず,CaO量は約31質量%程度以下に制限せざるを得ない。この約31質量%程度未満のCaO含有量では,アルミナを主体とする鋼中介在物と反応ないし流下させるのには十分でなく,依然,アルミナ付着ないしはノズル内孔の閉塞を生じることが多い。
さらには,耐火物の稼働面で鋼中介在物であるアルミナとの接触反応によって低融点相としてのZrO2を含むスラグ相が生成するが高粘性となり,溶鋼流速によってはアルミナ等の介在物が流下せず耐火物表面に付着する場合があり,鋼種や操業条件などの影響で安定した難付着性能が確保できなくなる問題がある。
またSiO2成分の添加は耐火物全体に含有されるために,溶鋼との接触面での自溶性にとどまらず,この耐火物構造体全体の軟化ないしは自溶性を促進してしまい,耐食性や強度が過度に低下する,等の問題もある。
さらに,その耐火物に上記特性を付与するための耐火物原料としてのZrO2-CaO組成物及びその製造方法,並びに前記耐火物を配置した鋳造用ノズルを提供することにある。
しかし,フリーのCaOを含まないZrO2-CaO-C系の耐火物の中に,例えば多量のCaO系組成物(例えばライムクリンカー)を単に含有させる,単にCaO成分の割合を増やすことでフリーのCaOを含むこととなった(一般的/従来技術の製法による)ZrO2-CaO系の組成物を原料として使用する等の方法では耐火物の,特に耐消化性を高めることができないことを本発明者らは知見した。
CaO成分の含有量をCaOクリンカー添加などにより単に高めたZrO2-CaO-C質の耐火物に対してもこの技術の適用を試みたが,この特許文献2の技術を単に適用しても耐火物の耐消化性を高めることができないことをも本発明者らは知見した。
すなわち,鉱物相としてZrO2への固溶量を超えるCaO(フリーのCaO)を含むZrO2-CaO系原料粒子内のフリーのCaOを微細化して,前記ZrO2-CaO系原料粒子の表面に露出するCaO部分すなわち前記ZrO2-CaO系原料粒子内のフリーのCaO部分が外部と接する一区画の面積を小さくすることを基本的な特徴とする。
これによりフリーのCaOを含むZrO2-CaO系原料粒子の水和を防止して耐消化性を改善することができる。
この基本的特徴を備えたZrO2-CaO系原料粒子に対し,さらに炭酸化物や無機質被膜等を形成することができ,この本発明の特徴を備えたZrO2-CaO系原料粒子に固有の,従来にはない前記ZrO2-CaO原料粒子表面全体を切れ目無く保護する構造を得ることができる。
1.
CaO成分を40質量%以上60質量%以下含み,CaO/ZrO2成分の質量比が0.67以上1.5以下であって,CaO結晶とCaZrO3結晶との共晶組織を含み,かつ,断面の組織中で観察できるCaO結晶の幅が50μm以下である,CaO-ZrO2組成物。
2.
CaO結晶の幅が20μm以下である,前記1に記載のCaO-ZrO2組成物。
3.
前記CaO-ZrO2組成物の表面には0.1μm以上5μm以下の厚さのCaCO3の被膜がCaO結晶及びCaZrO3結晶の表面に連続して存在する,前記1又は前記2に記載のCaO-ZrO2組成物。
4.
CaO原料とZrO2原料を,CaO成分とZrO2成分との組成上の液相線以上の溶融状態までに加熱する工程と,前記の溶融状態から固相線温度まで10℃/秒以上の速度で冷却する工程とを含む,前記1から前記3のいずれか1項に記載のCaO-ZrO2組成物の製造方法。
5.
前記のCaO原料は,不可避の不純物を除き,溶融時の温度でCaOとなるCaO化合物又は生石灰から選択する1種又は複数種であって,前記のCaO原料の大きさは10mm以下であり,
前記のZrO2原料は,CaO安定化ZrO2,CaO部分安定化ZrO2又は未安定化ZrO2から選択する1種又は複数種であって,前記のZrO2原料の大きさは10mm以下である,前記4に記載のCaO-ZrO2組成物の製造方法。
6.
前記1から前記3のいずれか1項に記載のCaO-ZrO2組成物を含む耐火物であって,
CaO/ZrO2成分の質量比が0.5以上2.2以下であって,製造上不可避の成分を除く総量を100質量%とするときに,CaO成分及びZrO2成分を合計で65質量%以上98質量%以下,及びフリーの炭素成分を2質量%以上30質量%以下含む,CaO-ZrO2含有耐火物。
7.
CaO/ZrO2成分の質量比が0.67以上1.5以下である,前記6に記載のCaO-ZrO2含有耐火物。
8.
前記のフリーの炭素成分の含有量が4質量%以上15質量%以下であり,非酸化雰囲気内1000℃での熱膨張率が0.5%以下である,前記6又は前記7に記載のCaO-ZrO2含有耐火物。
9.
B2O3,TiO2,P2O5,及びV2O5から選択する1種又は2種以上の成分を合計で0.1質量%以上5.0質量%以下含み,
前記CaO-ZrO2組成物の少なくともCaO結晶の表面に,CaOと前記B2O3,TiO2,P2O5,及びV2O5から選択する1種又は2種以上の成分との化合物からなる0.1μm以上15μm以下の厚さの無機質被膜が形成されている,前記6から前記8のいずれか1項に記載のCaO-ZrO2含有耐火物。
10.
CaCO3が前記無機質被膜の少なくとも一部と接する状態で存在しており,かつ,CaCO3の含有量が0.1質量%以上約2.5質量%以下である,前記6から前記9のいずれか1項に記載のCaO-ZrO2含有耐火物。
11.
SiC,金属Si,及びB4Cから選択する1種又は複数種をさらに含有し,
SiCについては10質量%以下,
金属Si,B4Cについてはいずれか一方又は両方の合計で2質量%以下である,前記6から前記10のいずれか1項に記載のCaO-ZrO2含有耐火物。
12.
前記6から前記11のいずれか1項に記載のCaO-ZrO2含有耐火物が,溶鋼と接触する部位の一部又は全部の領域に,溶鋼と接触する面から背面側に単層として配置されている鋳造用ノズル。
13.
前記6から前記11のいずれか1項に記載のCaO-ZrO2含有耐火物が溶鋼に接触する面の一部又は全部の領域に配置され,その背面側には前記の溶鋼に接触する面の一部又は全部に配置された耐火物とは異なる組成の耐火物からなる層が配置された複数の層をなしている鋳造用ノズル。
14.
内孔の一部にガス吹き込み用の耐火物からなる層を備えた,前記12又は前記13に記載の鋳造用ノズル。
すなわち,CaO結晶はCaO-ZrO2結晶組織内を分断するように,細長く薄い層状で連続的に存在することが多いので(図4参照),前記「幅」はこの細長い形状の短い方の長さを指す。なお,CaO結晶が細長く薄い層状で連続的に存在していたとしても,断面の切り方によっては,当該CaO結晶は粒子状,棒状,楕円形状,円形に表れることがある(図4参照)。この場合も,前記「幅」はCaO結晶の短い方の長さを指す。
このような組成物中のCaO結晶の幅は,従来の一般的技術では,フリーのCaO成分が存在する組成(CaOで約31質量%超え)においては,CaO含有量が多くなればなるほど,CaO結晶部分は集中し,かつその位置の連続構造の相は大形となる傾向がある。
このような大形のCaO結晶相が存在することで,このような組成物ないしはこのような組成物を使用した耐火物の耐消化性は極めて低くなる。
本発明者らは,CaO-ZrO2組成物中のCaO結晶の幅を概ね50μm以下にすることで,粒子状のCaO-ZrO2組成物の表面に後述の無機質又は炭酸化物被膜を設置しないでも,CaO結晶の水和を顕著に抑制することが可能となること,さらにはCaO結晶の表面に耐消化性や耐熱衝撃性を高めるために後述の無機質被膜又は炭酸化物CaCO3の被膜を形成する場合にもCaO結晶の幅を概ね50μm以下にすることで,CaO結晶及びCaZrO3結晶層の表面にこれら無機質被膜又はCaCO3の被膜を連続して存在させることができることを,上記従来技術の問題点と共に知見した。
そのメカニズムの詳細は不明であるが,粒子状のCaO-ZrO2組成物の外表面に露出したCaO結晶の幅が小さいことで,粒子表面の複数のCaO結晶の間に存在するCaZrO3結晶の間隔も小さくなり,複数のCaO結晶境界付近の無機質又は炭酸化物の被膜が,隣接するCaO結晶境界付近の無機質又は炭酸化物の被膜と架橋しやすくなるためと考えられる。そしてその架橋構造の無機質又は炭酸化物の被膜がCaO結晶相との間で多数のスパイクのように接合した構造を形成することから,その安定性も高まるものと考えられる。
耐火物としての難付着効果を顕著(フリーのCaOを含有しないCaO-ZrO2組成物に対する比較において)に得るためには,CaO含有量は40質量%以上が必要である。
本発明のCaO-ZrO2組成物においても,CaO成分の含有量が60質量%を超えると,CaO結晶部分は集中し易くなり,かつその一の連続構造の相は大形となる傾向があり,組成物の耐消化性が低下する傾向となり,さらに,組成物が高融点となるため電融時の溶融性が低下し,製造面での問題が生じる。それ故,CaOの含有量は60質量%以下とする必要がある。
またこの場合は,製造上不可避の成分を除く総量を100質量%とするときに,CaO及びZrO2を合計で65質量%以上98質量%以下,及びフリーの炭素成分を2質量%以上30質量%以下含むことになる。
このような他のCaO成分含有組成物又は他のジルコニア成分含有組成物をも含有させる場合は,CaO/ZrO2成分の質量比は0.5以上2.2以下,製造上不可避の成分を除く総量を100質量%とするときに,CaO成分とZrO2成分の合計量は65質量%以上98質量%以下である。
この理由は,前記他のCaO成分を含有する場合は,他のCaO成分が消化する可能性が高いので,他のCaO成分の量はその消化による耐火物組織を破壊させない程度以下にする必要があるからである。すなわち,当該耐火物中のCaO/ZrO2成分の質量比が2.2を超えると,CaO成分が消化する可能性が高くなる。
また,前記他のZrO2成分を含有する場合は,他のZrO2成分により難付着性が低下する可能性が高くなるので,他のZrO2成分の量は難付着性を低下させない程度以下にする必要があるからである。すなわち,当該耐火物中のCaO/ZrO2成分の質量比が0.5未満,且つCaO及びZrO2の合計量が65質量%未満であると,十分な難付着性の改善効果を得難くなる。
高い耐消化性を維持するため,又は過度な自溶性を抑制するためには,当該耐火物中のCaO成分が全て本発明のCaO-ZrO2組成物に由来していて,例えば生石灰やドロマイト(CaO-MgOクリンカー)に由来するフリーのCaOを含む原料は含まないことが好ましい。この好ましい場合の当該耐火物中のCaO/ZrO2成分の質量比の上限は1.5となる。
当該耐火物中のフリーの炭素成分は,したがって2質量%以上とするが,さらに結合材としての炭素を増加させる,又は,耐熱衝撃性等を向上させるために黒鉛等の炭素成分を加えることができる。
このフリーの炭素成分は,30質量%を超えると耐食性や耐摩耗性の低下,さらには鋼中への炭素成分の溶出,介在物発生等による鋼品質の低下等を生じる虞があるので,30質量%以下とする。さらなる耐食性や耐摩耗性の低下抑制,鋼中への炭素成分の溶出等抑制のためには,フリーの炭素成分量は15質量%以下であることが好ましい。
(1)B2O3,TiO2,P2O5,及びV2O5から選択する1種又は2種以上の成分を合計で0.1質量%以上5.0質量%以下含有させる,
(2)前記(1)により前記CaO-ZrO2組成物の少なくともCaO結晶の表面に,CaOと前記B2O3,TiO2,P2O5,及びV2O5から選択する1種又は2種以上の成分との化合物からなる0.1μm以上15μm以下の厚さの無機質被膜を形成させることができる。
前述の無機質被膜は,主としてCaO-ZrO2組成物のCaO成分の露出表面を水和しないように保護する機能をも有するので,これにより耐消化性をさらに顕著に向上させることができる。
特に,フリーの炭素成分が15質量%以下と含有割合が小さい場合は,従来技術では特に,一般的に耐熱衝撃性が低下する傾向となる。しかし,前記の無機質被膜を備えた本発明の耐火物では,1000℃非酸化雰囲気内での熱膨張率を同様な化学組成の従来技術の耐火物に比較して約1/2程度である,0.5%以下とすることができる。
なお,これを言い換えると,この無機質被膜は,原料としてのCaO-ZrO2組成物の+粒子の表面に炭酸化物の被膜が存在する場合にも存在しない場合にも前述の無機質被膜を形成させることができるということである。
炭素を含有する耐火物内部では酸素分圧が低い状態であるため,蒸気圧の高い酸化物は組織中でガス成分として充満しやすく,ガス成分が組織中のCaO成分を含有する粒子表面で選択的に反応して,比較的均一な被膜状の無機質化合物をつくる。あるいは液相状態又は固体状態でCaO成分と直接接触することで,同様の無機質化合物を生成する。本発明で使用する酸化物の融点は,B2O3:約480℃,TiO2:1840℃,P2O5:340℃,V2O5:690℃である。このうち,B2O3及びV2O5は特に融点が低く蒸気圧が高いため,本発明においてCaO表面に無機質化合物層を形成するには特に好適な酸化物である。
(イ)生成した無機質化合物が水分に対して安定であり,かつ
(ロ)CaO成分を含む粒子の表面がこの安定な無機質化合物で均一に被覆されていること,さらに
(ハ)この無機質化合物からなる被膜が多孔質でなく,亀裂や剥離のない無欠陥被膜であること
が重要な要素となる。
CaO+H2O=Ca(OH)2
この反応において標準生成自由エネルギーΔG゜は,-57.8kJ/mol(T=298K)である。
前述したように,CaOの水和を防止するには,主に,CaO成分を含む粒子中のCaOの活量を下げ,CaOを不活性化させる方法の追求,あるいは,CaOを含む粒子表面に,少なくとも最終製品段階で,緻密で安定な水成分不透過性の被膜形成の追求が行われてきた。前者の手法として,TiO2など酸化物との化合物化手法にて対応がとられてきたが,CaOを不活性化するためにそれらを過剰に添加し化合物化せねばならず,その結果,CaO自体の反応性に寄与する活性,いわゆるCaOの活量が著しく低下し,鋼中アルミナ介在物との反応性が著しく低下し閉塞防止効果の点で問題を生じる。さらに化合物化により低融点化を招きやすい。また,CaO成分を含む粒子の水和防止機能も十分とは言い難い。また,後者の手法は,極めて薄い(0.05~4μm)炭酸化被膜であったり,油分系の被膜であったりするので,耐火物の製造プロセス,特に耐火物原料の混練,熱処理,加工プロセスにて被膜の一部又は全部が破れたり消失したりして,十分な耐消化性が発揮できていない。
3CaO・B2O3(+32.0kJ/mol),2CaO・B2O3(+44.1kJ/mol),CaO・B2O3(+82.4kJ/mol)
3CaO・2TiO2(+12.4kJ/mol),4CaO・3TiO2(+16.8kJ/mol),CaO・TiO2(+24.4kJ/mol)
3CaO・V2O5(+52.9kJ/mol),2CaO・V2O5(+74.6kJ/mol),CaO・V2O5(+88.2kJ/mol)
3CaO・P2O5(+236kJ/mol),2CaO・P2O5(+280.7kJ/mol)
なお,( )内には各化合物の水和反応時の自由エネルギー変化(ΔG,at298K)を示した。これらの無機化合物は,いずれもΔGがプラスであるため水和反応は起こらないことを示している。
本発明で生成する各無機質化合物を使用して被膜厚さを検討した結果,耐消化性に優れかつ亀裂や剥離のない良好な被膜とするには,その厚さは0.1μm以上15μm以下であることが必要であり,好ましくは0.5μm以上5μm以下である。被膜の厚さが0.1μm未満では,連続的な被覆層の生成が困難となり,被覆に連続性がなくなり耐消化性が低下する。また,被膜が15μmより厚いと粒子と被膜間の熱膨張率の違いから被膜の亀裂や剥離が発生しやすくなり,また空隙層の厚さが小さくなって,結果として耐消化性の低下と熱膨張が大きくなる可能性が生じる。
しかし,さらに厳しい条件,例えば高温多湿で長期間放置されるような環境では,被膜に存在する微細な欠陥により水和反応が徐々に進行することがある。そのような場合は,さらに,炭酸ガスと反応させ,粒子表面にCaCO3被膜をつくること(以下,炭酸化処理)で,耐消化性を改善することも可能である。この場合,炭酸カルシウム(CaCO3)が分解する温度以下の温度内で熱処理する必要がある。耐消化性が改善する理由は,無機質被膜欠陥を通して侵入したCO2の一部がCaO含有粒子表面で炭酸カルシウムを生成して消化を防止する,また,被膜を構成しているCaOの一部がCO2と反応して被膜中の開口部などを中心に炭酸カルシウムを生成し被膜欠陥が減少又は消失させるためと考えられる。
CaCO3量が0.1質量%より少ないとその効果が現れ難くなり,2.5質量%を超えると,鋳造前の予熱条件によっては予熱時や鋳造時にCO2の発生によりモールド中の溶鋼湯面レベルが大きく変動するボイリング現象や,注湯初期のスプラッシュなど操業上の問題が発生することがあるため好ましくない。
MS=L/D×100(%)
耐火物の顕微鏡組織観察において,粒子径の大きい順に粗大粒子を10個選定し,個々の粒子の面中に,その輪郭に接して内包する最も大きい円を描き,その中心を通る任意線を引く。さらに,その線を基準として前記円の中心を通る45°ピッチの線をさらに3本引き,計4本の線を粒子1個につき引く。その後,粒子の前記各線上で粒子の両端の輪郭点間の長さをD1,D2,D3,D4として,さらに,各線上での両端部での粒子界面に存在する空隙層厚さの合計をそれぞれ,L1,L2,L3,L4として計測する。これら4つの線で得られた数値を用いて,上記式で算出したMS1,MS2,MS3,MS4をそれぞれ算出し,それらの数値の平均値を1つの粒子の空隙層厚さ率すなわちMS値として算出する。予め選んでおいた10個の粒子のMS値をそれぞれ上記の方法で算出し,それらを平均化して,当該耐火物組織のMS値とする。
耐火物組織中の原料粒子の熱膨張に伴う体積変化が耐熱衝撃性に及ぼす影響が大きい,すなわち粒子が大きい程その膨張による体積/長さ変化も大きいことになる。したがって,耐熱衝撃性を調整・評価するための指標としてのMS値は,耐火物組織中の大きい原料粒子について算出することが必要となる。
その結果,耐火物の1500℃までのマクロ的な熱膨張量は,カーボン質マトリックスの膨張量が支配的となり,従来の化学成分の加成則に依存しないことになり,顕著な低膨張特性を示すことが可能となる。従って,熱膨張量の視点から個々の粒子は,より多くの空隙層厚さ率(膨張代)を持つことで低膨張化が可能となる。さらに,このような低膨張特性を顕著に出すためには,炭素質マトリックスが3次元的に連続することが必要であり,適用する粒子も微粉を多く含まない粒度分布とすることが望ましい。
しかしこの手法による効果は,縦令同じCaO含有量の化学組成を有するものの,例えばライム組成物又は従来技術によるCaO結晶の幅が大きいCaO-ZrO2組成物のような,単なるフリーのCaOを含む従来技術(具体的にはほとんどのCaO結晶の幅が50μmを超える)のCaO-ZrO2含有組成物(原料)を使用しても実現することができない。すなわち本発明のCaO-ZrO2含有組成物(原料)を使用しなければ,得ることができないことを本発明者らは知見した。
その理由は,従来技術のフリーのCaOを含むCaO-ZrO2含有組成物(原料)ではCaO結晶の幅が大きいことから,主にそのフリーのCaO表面に形成する,またCaO結晶とCaZrO3結晶との間の無機質被膜を欠陥なく連続的かつ安定した状態で形成ないしは維持することができないからであると考えられる。
これらは炭素成分の酸素による酸化,酸化物との酸化・還元反応を抑制して炭素成分ないしは耐火物組織を保護することに寄与する。また強度を高める効果も得られる。
この場合,各含有量は,1000℃の非酸化雰囲気で加熱後の化学成分において,SiCについては10質量%以下,金属Si,B4Cについてはいずれか一方又は両方の合計で2質量%以下であることが好ましい。
SiCについては10質量%を超えると溶損(化学的溶損)が大きくなる,金属Si,B4Cについていずれか一方又は両方の合計が2質量%を超えると強度向上効果が得られるものの,耐熱衝撃性が低下する傾向となる。
本発明のCaO-ZrO2組成物を耐火物に含有させることより,従来技術によるCaO-ZrO2系の耐火物では得られなかった高いCaO含有量のCaO-ZrO2系耐火物を得ることができる。
特に炭素含有の耐火物において顕著な耐消化性を備え,自溶性を抑制することによる高い耐食性をも備え,さらには顕著な耐熱衝撃性をも有しつつ,溶鋼内のアルミナ系介在物の顕著な付着防止効果を得ることができる。
本発明の耐火物を鋳造用ノズル等に配置することで,特に内孔へのアルミナ等介在物が発生し易い鋼の連続鋳造において長時間に亘り安定した操業を行うことを可能にすることができる。
ひいては,鋼の品質の向上,安定化等へも貢献することができる。特に介在物量を顕著に低減することが要求される高級鋼などへの適用が好適である。
(1)CaO原料と,ZrO2原料を,混和して電融法等によりCaOとZrO2との組成上の液相線以上の溶融状態までに加熱する工程,
(2)前記の溶融状態から固相線温度まで10℃/秒以上の速度で冷却する工程。
これらのうち,原料コストの点からは,最も安価な未安定化ジルコニア(バデライト)が好ましい。
完全安定化ジルコニアや部分安定化ジルコニアを使用する場合は,目的物がCaO-ZrO2組成物であるので,安定化剤をCaOとする原料が好ましい。例えばY2O3やMgOを安定化剤とするものも使用可能であるが,本発明の組成物の中に含まれるCaO成分及びZrO2成分以外の,不可避の不純物を含む成分(以下これらを総称して「不純物」ともいう。)は,6質量%程度以下,好ましくは3質量%程度以下にするよう,原料構成を設定することが好ましい。これら不純物等が多くなると,CaO-ZrO2組成物の耐消化性等を低下させる虞がある。
これらZrO2原料は,独自に粉砕・整粒したものの他,市販されている砂状のものも使用することができる。
但し,電気炉等への投入時の流動性を高める等の目的から,3mm以下の微粉原料をより大きい二次粒子に成形して10mm以下のペレット状にしたものも使用することもできる。
原料粒度が10mmを超えると,溶融するために長時間が必要となり,消費電力量も増加する傾向となり,生産性の低下及び生産コストの上昇を来す。生産性の低下及び生産コストの上昇を避ける点から,できるだけ小さい粒子を用いることが好ましいが,最小粒子サイズは,消化,発塵等の他の要素をも考慮して総合的に決定すればよい。
CaO原料としては,溶融時間・温度との関係もあるが,CaO原料の大きさがCaO結晶の幅に影響を及ぼす傾向があり,CaO原料は小さい方がCaO結晶の幅を小さくし易い。したがって,CaO原料は,例えば3mm程度以下で,できるだけ小さいことが好ましい。
溶融状態から固相線温度まで10℃/秒以上の速度で冷却することで,CaO結晶の大きさ(幅)を概ね50μm以下にすることができる。但し,溶融設備の大きさや溶融単位(溶融浴の大きさ)によって,内部と外部又は冷却面とその内部との温度差すなわち冷却速度の違いが生じるので,溶融物全体の均一な冷却を行うためにはできるだけ前記の冷却速度は大きい方が好ましい。
なお,急冷の具体的な方法は特に制限はなく,例えば,溶融物を鉄板上に流し急冷する方法,間隙部を設けた冷却金型に鋳込む方法,アトマイザーを用いて溶融物を急冷する方法,溶融物を圧縮空気で吹き飛ばす方法等原料として必要な特性に応じて,設備構造,装置を任意に選択することができる。
冷却速度を知るための温度の測定方法は,適宜利用可能な測定方法であればよい。例えば,赤外線サーモグラフィー等の非接触温度計,光ファイバー温度計,熱電対等を併用して溶融状態から固化するまでの対象物の冷却速度を実測する方法,それらのデータを下にCAE解析により平均冷却速度を計算により推定することが可能である。
現場的には次のような簡便な方法も採用することができる。
例えば,冷却金型に鋳込む場合は,事前に溶融物温度を測定しておき,冷却用の金型容器に鋳込み,前記の冷却用の容器内での対象物の流動性が無くなった時点を固相線の温度に達した時点とみなして,溶融物の温度から固相線の温度を差し引いた値を,流出時から流動性が無くなった時点までの時間で除した値を冷却速度とみなす。
この整粒後のCaO-ZrO2組成物は水や高温高湿度に曝さないような状態で保管して使用する必要がある。また,必要に応じて炭酸化処理を行うこともできる。
例えば,耐火原料(耐火性粒子)としての前記CaO-ZrO2組成物に結合剤を添加し,混練後の坏土を成形に適した状態に調整する,前記坏土をCIP(Cold Isostatic Pressing)により成形し,約300℃以下の温度で乾燥処理を行った後,約800℃以上約1200℃以下程度の非酸化雰囲気中での熱処理を行う。また,必要に応じて炭酸化処理を行うこともできる。
例えば,好適なB2O3源として,三酸化二ホウ素,ホウ酸エステルを使用することができ,四ホウ酸ナトリウム,メタホウ酸カリウムなども使用することが可能である。
TiO2源としては酸化チタン等や,有機チタン化合物などを使用することが可能である。
P2O5源としては市販されている一般的な製品を使用することができる。
V2O5源としては酸化バナジウムを使用することができる。
これらの結合用炭素原料に加え,固体の炭素質原料を任意で使用することができる。これら固体の炭素質原料としては,黒鉛,カーボンブラック等の粒子状の他,カーボンファイバーなどの繊維状の炭素質原料を使用することができる。
ただし,これらの炭素質原料は,製品段階,すなわち1000℃非酸化雰囲気での加熱後の化学成分において,耐火物に占める割合で2質量%以上30質量%以下となるように,結合用炭素原料中の消失する成分の割合(すなわち残留する炭素の割合を除く部分の割合),固体の炭素原料の消失割合(不純物の加熱減量分等)等を耐火物としての所要炭素成分量に加算した量で,坏土に添加する必要がある。
本発明者らは,このような均一な被膜の形成は,本発明の幅の狭いCaO結晶を含有するCaO-ZrO2組成物に特有の事象であって,従来技術の幅の厚いCaO結晶を含有するCaO-ZrO2組成物では生じないことを知見した。
すなわち,このような被膜は,本発明の幅の狭いCaO結晶を含有するCaO-ZrO2組成物であれば,その粒子のCaO結晶表面だけに形成せず,CaO結晶との共晶組織中のCaO・ZrO2結晶の表面にも連続的に形成することを見いだした。これに対し従来技術の幅の厚いCaO結晶を含有するCaO-ZrO2組成物では,CaO結晶表面だけに,しかも不安定(断片的)に形成し,しかも脱落し易いので,従来技術の幅の厚いCaO結晶を含有するCaO-ZrO2組成物を原料とする耐火物ではその耐消化性を高めることができない。
このメカニズムは必ずしも明確ではないが,クリンカー製造時の冷却速度を速めることで,CaO・ZrO2結晶とCaO結晶とが,交互に微細に配置された共晶組織構造であることに加えて,CaO・ZrO2の内部では理論組成よりもCaO含有量がやや高めになっている,本発明者らの発見による事実を考え合わせると,高温融液が過冷却状態で凝固した結果,CaOリッチな組成になったと推定され,それ故,CaO・ZrO2結晶中に過剰なCaOが存在する結果として,結晶内のCaイオンの拡散が容易になり,CaO・ZrO2結晶層表面においても被膜が形成され,さらにCaO結晶層表面との被膜とも連続した被膜を形成すると考えられる。
また,図5(c)は,図5(a)の浸漬ノズルの内孔部(内孔壁面)の一部から溶鋼中にガスを吹き出す機能を備えた浸漬ノズルの例を示す。この例では内孔部の一部に通気性が高い耐火物22G(以下,単に「通気用耐火物」ともいう。)を配置している。この通気用耐火物22Gの材質は,一般的なアルミナ-黒鉛質の通気用耐火物とすることもできるほか,本発明の耐火物組成を維持しつつ気孔率や通気率等を高めた材質とすることもできる。なお,溶鋼中へのガスの供給は,前記図5(c)の例のような浸漬ノズルだけでなく,その上方に位置する上部ノズルやスライディングノズル等の溶鋼流通経路中の他の部位からも行うことができる。
例えば図6の左側は鋳造用容器内から溶鋼を排出する際の溶鋼流通経路としてのノズル部が,複数の鋳造用ノズルからなる構造体のうち,浸漬ノズルが外装式の例を示す。本発明の耐火物は,浸漬ノズルFだけでなく,このような複数の鋳造用ノズルからなる構造体の上部ノズルA,スライディングノズルプレートB,下部ノズルC,ロングノズルD等の諸々のノズルの溶鋼に接触する面の一部又は全部に配置して適用することができる。また,排出経路としてのノズル部が一体化された構造の,いわゆる内挿式浸漬ノズル(図6の右側),溶鋼中に浸漬されない,いわゆるオープンノズル等にも適用することができる。さらには,ノズル部の上方に位置して溶鋼流量又は開閉を行うストッパーEや溶鋼容器の内張り用耐火物Gとしても適用することができる。
アルミナ等の非金属介在物の耐火物表面への付着の場所や程度は,個別の操業条件に依存して変動する。したがって,このような溶鋼と接触する部位の「一部」又は「全部」の領域は,各個別の操業条件ごとに,最も付着を抑制したい部位を選択して決定するものであって,固定的なものではない。したがって,「一部」ないし「全部」の領域は任意に決定し得る事項である。
もちろん,図7のような溶鋼に接触する面の耐火物20の層と,その背面側に他の層として設置する耐火物は前記本発明の耐火物20と同じ組成の耐火物であってもかまわない。
このCaO-ZrO2組成物の実施例Aでは,CaO原料及びZrO2原料の各原料(出発原料)の質量割合を変化させて,混合物の溶融状態,フリーのCaOの存否,CaO結晶の幅等を調査した。
出発原料(質量%)は,CaO原料(CaO源)として,粒度構成が≦10mmの生石灰を使用,ZrO2源として,粒度構成が≦10mm(概ね≦3mm)の未安定化ジルコニア(バテライト)を主として使用し,一部の実施例ではCaOによるほぼ完全な安定化ジルコニア,MgOによるほぼ完全な安定化ジルコニアZrO2を使用した。これらCaO安定化ジルコニア,MgO安定化ジルコニアの粒度構成も≦10mmである。
前記出発原料の混合物の溶融は電気炉を用い,溶融量を約0.5tとして約2800℃まで昇温し,便宜的に定めた所定の時間までその温度を維持した。
後述する各実施例におけるCaO-ZrO2組成物試料の製造においても,温度,時間,溶融量等の条件は,本実施例と同様である。
フリーのCaO結晶の幅は,前記顕微鏡による組織観察にて,その視野内の粒子断面のフリーのCaO結晶の幅を測定して評価した。
例えば図1に実施例1のCaO-ZrO2組成物の顕微鏡写真を示している。CaO結晶とCaZrO3結晶との共晶組織を含み,かつCaO結晶の幅が50μm以下であることがわかる。一方,図2には,実施例1と同じ出発原料の混合物を溶融後,徐冷(冷却速度:10℃/秒未満)して得られたCaO-ZrO2組成物の顕微鏡写真を示している。CaO結晶とCaZrO3結晶との共晶組織を含むが,ほとんどのCaO結晶の幅が50μm超であることがわかる。
なお,CaO/ZrO2原料の割合が60/40の実施例1は,十分に溶融させるまでに他の実施例に比較して長時間を要した。このことは溶融,収率等における生産性の低下や偏析を生じ易いことを意味しており,製造において注意を要する。
CaO/ZrO2原料の割合が61/39の比較例1は融点が高く,十分に溶融できなかった。
これらのことから,本発明のCaO-ZrO2組成物の製造における,CaO/ZrO2原料の割合上限は60/40が妥当又は好ましいと考える。
また,CaO/ZrO2原料の割合が30/70の比較例3は,CaO-ZrO2組成物中にフリーのCaOが存在しなかった。
耐消化性について,比較例のいずれもが目標とする≧1日に至らなかったのに対し,いずれの実施例も目標とする≧1日を満たすことができた。
CaO完全安定化ジルコニアを使用した実施例5,MgO完全安定化ジルコニアを使用した実施例6でも未安定化ジルコニアを使用した例と同様の結果を得ることができた。
このCaO-ZrO2組成物の実施例Bは,前記CaO-ZrO2組成物の実施例Aの実施例2を基礎にして,CaO-ZrO2組成物の表面に,炭酸化処理によるCaCO3の被膜を形成させた試料につき,CaCO3の被膜の厚さと耐消化性との関係を調査した例である。
さらに炭酸化物被膜が厚い実施例7~9については,炭酸化物被膜の厚さが大きくなるに伴い重量増加割合が+1.5%に到達するまでの日数が長くなっていることがわかる。またこれら実施例の炭酸化物被膜について顕微鏡で観察したところ,粒子全体を連続的に覆っていることを確認した。
溶融後冷却速度が<10℃/秒(8℃/秒)である,本発明の方法よりも小さい冷却速度で製造した比較例4は,実施例8と同様な炭酸化処理を行ったにも拘わらず,ほとんどのフリーのCaO結晶の幅が50μmを超えていて,本発明のCaO-ZrO2組成物としての構造を備えておらず,炭酸化物被膜の形成が不均一で,しかも被膜が存在する部分でも非連続な部分(フリーのCaO結晶が表面に露出した部分)が多く存在した(後述のCaO-ZrO2組成物の実施例Cを参照)。耐消化性の試験結果もこれを反映して,前記日数が<1となった。
このCaO-ZrO2組成物の実施例Cは,前記CaO-ZrO2組成物の実施例Aの実施例2を基礎にして,溶融後の冷却速度を変化させて,この冷却速度とCaO-ZrO2組成物のCaO結晶の幅との関係,さらにはそれと耐消化性との関係を調査した例である。
なお,冷却速度の調整は傾注速度を制御し,溶融物の厚さを調整する方法により行った。
また,本実施例Cでは,全ての試料に炭酸化処理を行っていない。
耐消化性は,前記実施例Bと同様の方法,同様の評価基準とした。
また,この冷却速度が大きくなるのに伴い,耐消化性も高くなっていることがわかる。
このCaO-ZrO2組成物の実施例Dは,CaO-ZrO2組成物の出発原料としてのCaO原料の大きさを変化させ,CaO結晶の幅,耐消化性への影響を調査した例である。
出発原料(質量%)は,CaO原料(CaO源)として,粒度構成が概ね3mm以下(≦3mm),<3mm超5mm以下,5mm超10mm以下,10mm超(>10mm)の生石灰を使用,ZrO2原料(ZrO2源)として,粒度構成が≦10mm(概ね≦3mm)の未安定化ジルコニア(バテライト)を使用し,CaO原料/ZrO2の質量割合を50/50とした。
また,本実施例Cでは,全ての試料に炭酸化処理を行っていない。
耐消化性は,前記実施例B,実施例Cと同様の方法,同様の評価基準とした。
また,このCaO原料の粒度が小さくなるのに伴い,耐消化性も高くなっていることがわかる。
なお,CaO原料の粒度が>10mmの場合でも,電力等を大幅に供給する(温度を上げる),高温度での保持時間を大幅に長くする,等の方法を採れば,フリーのCaO結晶の幅を≦50μmにすることが可能と考えられるが,産業上合理的でなく,好ましくない。
この耐火物の実施例Aは,耐火物の化学成分のうちCaO/ZrO2質量比が,アルミナ付着性及び耐消化性に及ぼす影響を調査した例である。
CaO-ZrO2組成物を使用し,当該耐火物炭素量(黒鉛と結合剤としての炭素の合計量)を11.8%質量%とし,CaO/ZrO2質量比を変化させた。
さらに,本発明のCaO-ZrO2組成物に加えて,他のCaO系原料,ZrO2系原料を併用した場合のCaO/ZrO2質量比の影響も調査した。
なお,実施例23以外の耐火物試料には炭酸化処理を行って,本発明のCaO-ZrO2組成物及び他のCaO系粒子には0.5μm~2μmの厚さの炭酸化物被膜を形成した。
前記溶鋼中回転試験での付着速度が<±5μm/min.を○(優,目標値),+5~+10μm/min.又は-5~-10μm/min.を△(可),>±10μm/min.を×(不可)として評価した。
この溶鋼中回転試験の評価基準は,「+」がアルミナ付着を,「-」が溶損(減寸)を表しており,アルミナ付着性と共に耐食性を同時に評価している。
なお,本発明のCaO-ZrO2組成物以外のZrO2源を含有する実施例(実施例19,20,21)でも,耐火物のCaO/ZrO2質量比が≧0.5であれば,付着傾向となるものの,アルミナ難付着性と耐溶損性とを好適なバランスとすることができることがわかる。
また,本発明のCaO-ZrO2組成物以外のCaO成分を含有する実施例(実施例22,23)でも,耐火物のCaO/ZrO2質量比が≦2.20であれば,溶損傾向となることがあるものの,アルミナ難付着性と耐溶損性とを好適なバランスとすることができることがわかる。
耐火物のCaO/ZrO2質量比が>2.2である比較例(比較例9,10)では,アルミナ付着は小さいものの,溶損が大きいことがわかる。
さらに,CaO源として生石灰を含有する比較例9では,当該耐火物に対して炭酸化処理を施したにもかかわらず,耐消化性が劣ることがわかる。
この耐火物の実施例Bは,耐火物の化学成分のうち炭素成分の割合が,アルミナ付着性及び耐消化性,さらには熱膨張性に及ぼす影響を調査した例である。
なお,炭素成分の割合を増減に伴い,CaO成分とZrO2成分との合量の範囲の影響も併せて調査した。
熱膨張は,1000℃非酸化雰囲気下での熱膨張率(%)を測定して,≦0.5%を○(目標値,良),<0.5%を×(不良)として評価した。
本発明の耐火物の主要且つ重要な用途である鋳造用ノズルに関しては,高度な耐熱衝撃性が要求されており,一般的に1000℃での熱膨張率が0.5%以下のアルミナ-黒鉛質が使用されている。
本発明のCaO-ZrO2組成物を主として含有する耐火物では,それら一般的な材質に比較して同等レベルの熱膨張化することを確認した。
なお,特に鋳造用ノズルでの高度な耐熱衝撃性を得るためには熱膨張率が≦0.5%であることがより好ましいことを本発明者らは知見しており,その知見を基礎に目標値を≦0.5%とした。
総合評価としては,本発明の課題を解決することができる耐火物として合格の場合を○,好ましくないものの使用可能(顕著な効果は得られないが或る程度の改善効果は得られる)である場合を△,不合格の場合を×とした。
耐火物の炭素成分量が>30質量%(31質量%,比較例12),及び<2質量%(1質量%,比較例14)ではいずれも溶損大となることがわかる。前者は炭素成分自体の鋼中への溶解,磨耗等,後者は耐火物の強度不足による損耗が主となっている。
また,耐火物の炭素成分量が2~30質量%の範囲内でも,CaO成分とZrO2成分の合量が,<65質量%(64質量%,CaO源としてドロマイトを含有する比較例13)では,溶損大となることがわかる。
また,CaO成分とZrO2成分の合量は65~98質量%である必要があることがわかる。
しかし,より好ましい目標値≦0.5%は,炭素成分量が≧4質量%(実施例28)で得られることがわかる。すなわち,熱膨張率の観点からも炭素成分量は≧4質量%がより好ましいことがわかる。
なお,炭素成分として,黒鉛及びフェノールレジンの残炭素成分を使用した本実施例Bでは,黒鉛としての炭素成分量が多い程,熱膨張率は小さくなる傾向があることがわかる。
前記酸化物としては,五酸化二リン(P2O5),酸化バナジウム(V2O5)及び酸化チタニウム(TiO2),酸化ホウ素(B2O3)を選択した。
試料は,前記耐火物の実施例A,Bと同じ要領で製造し,同じ方法で評価を行った。
アルミナ付着性試験は,前記耐火物の実施例A,Bと同様の方法,評価基準とした。
熱膨張試験は,前記耐火物の実施例Bと同様の方法,評価基準とした。なお,本実施例の熱膨張評価での「×」は,-般的なアルミキルド鋼等の鋳造の条件には好ましくない,との趣旨である。このような「×」=好ましくない評価の例も,アルミナ付着程度が極めて大きい鋼の操業条件においては使用可能,かつ好適である場合がある。
総合評価としては,本発明の課題を解決することができる耐火物として合格の場合を○,好ましくないものの使用可能(顕著な効果は得られないが或る程度の改善効果は得られる)である場合を△,不合格の場合を×とした。
P2O5,V2O5を併存する実施例39,P2O5,V2O5,TiO2の3者が併存する実施例40,41の場合も,耐消化性,難付着性,耐溶損性に関して前記酸化物それぞれを単独で含有する場合と同様の顕著な効果が得られた。
しかし,前記酸化物含有量が単独で5質量%を超える実施例35,P2O5,V2O5,TiO2の3者の合計が5質量%を超える実施例41の場合は,耐食性が低下する傾向となることがわかる。これらの耐食性が低下する,すなわち自溶性傾向が強まるため,鋼種によっては介在物発生の虞があるが,付着抑制を重視し,鋼品質が厳格でない場合の耐火物としては使用可能である。しかし,耐火物由来の介在物の混入を嫌う鋼種の場合は,表7の結果等から,これら酸化物の含有量は単独又は合量で5質量%以下であることが好ましいことがわかる。
したがって,CaOと前記B2O3,TiO2,P2O5,及びV2O5から選択する1種又は2種以上の酸化物との化合物の厚さは,0.1μm以上15μm以下であることが好ましい。
但し,熱膨張が大きくなる場合も,より好ましい目標値≦0.5%は超えるものの,その最大値は従来の一般的な耐火物としてのアルミナ-黒鉛質耐火物の熱膨張よりも小さいので,前記従来技術と比較して耐熱衝撃性は優れる。
なお,この表7の結果から,P2O5,V2O5を併存する場合も,P2O5,V2O5,TiO2の3者が併存する場合と同様の結果が得られると推測でき,これら酸化物のいずれか2者が併存する場合のこれら酸化物の含有量も≦5質量%が好ましい。
図3より,実施例38の耐火物は,CaO-ZrO2組成物表面に連続被膜を有し,かつCaO-ZrO2組成物及び前記皮膜と,炭素質マトリックスとの間に空隙層が存在することがわかる。
また図4より,このCaO-ZrO2組成物はCaO結晶とCaZrO3結晶との共晶組織を含み,かつCaO結晶の幅が50μm以下であることがわかる。
この耐火物の実施例Dは,本発明の焼成処理後の耐火物中のCaO-ZrO2組成物にさらに炭酸化処理を行い,組成中のCaCO3含有量を変化させてそれら耐火物の耐消化性,アルミナ付着性,熱膨張性に及ぼす影響を調査した例である。
試料は,前記耐火物の実施例A,B,Cと同じ要領で製造し,同じ方法で評価を行った。
なお,このCaCO3の含有量(これはほぼCaCO3被膜の厚さに相関する)の制御は,炭酸ガス濃度,処理温度,処理時間,炭酸ガス圧力等を変動させることによって行った。
また,本実施例Dでは,CaCO3被膜の状態,すなわちCaCO3被膜が前記無機質化合物被膜の少なくとも一部と接しているか否か,及びCaCO3被膜の厚さ(μm)を顕微鏡にて観察した。
さらに,耐火物試料を1600℃の溶銑中に浸漬して,溶銑のボイリング状態を目視で確認した(以下,「溶銑中浸漬試験」ともいう。)。このボイリング試験では,ボイリングしない場合を◎,ボイリングが小さい場合を○,ボイリングがやや多い場合を△として評価した。
総合評価としては,本発明の課題を解決することができる耐火物として合格の場合を○,不合格の場合を×とした。
しかし,CaCO3含有量が3.0質量の実施例46では,溶銑中浸漬試験において,溶銑のボイリングがやや多くなった。これは炭酸成分の分解ガスによるものであるが,この現象は鋳造の操業において溶鋼へ品質への低下,又は操業時の危険性を増大することも考えられる。
したがって,CaCO3含有量は2.5質量以下であることが好ましい。
この耐火物の実施例EはSiC,B4C及び金属Siから選択する1又は複数種を含有する場合のアルミナ付着性,耐食性を調査した例である。
試料の作製方法,アルミナ付着性(耐食性を兼ねる)の評価方法,評価基準は前記耐火物の実施例Dと同じである。
強度は1000℃非酸化雰囲気中熱処理後の試料の曲げ強さを測定し,比較例16の曲げ強さ(2.5MPa)を100とする指数で表示した。
総合評価としては,本発明の課題を解決することができる耐火物として合格の場合を○,好ましくないものの使用可能(顕著な効果は得られないが或る程度の改善効果は得られる)である場合を△,不合格の場合を×とした。
SiCを単独で含有する実施例47~50のうち,SiC含有量が10質量%の実施例49はアルミナ付着試験においてやや溶損傾向となり,10.5質量%の実施例50は溶損が大きくなる結果となった。
この結果から,一般的なアルミキルド鋼等の連続鋳造では,SiCの含有量は10質量%以下が好ましいことがわかる。
この耐火物の実施例Fは本発明の耐火物の溶鋼品質への影響(溶鋼汚染程度)を,他の従来技術の材質との比較において,溶鋼中の炭素含有量の変化により評価した例である。
また,本実施例Fではアルミナ付着試験を行って,アルミナ付着程度又は溶損程度をも測定した。
これに対し,従来技術の難付着性を指向する比較例15,16では,鋼中炭素成分の変化が極めて大きく,またアルミナ付着試験での耐火物の溶損も大きい傾向となっていることがわかる。
10b 試験片
10’ 端面
11 ホルダー
12 坩堝
13 溶鋼
14 高周波誘導炉
20 本発明の耐火物
21 パウダーライン材質(背面側の耐火物)
22 本体材質(背面側の耐火物)
22G 本体材質(通気性の耐火物)
22S 空間(ガスの通過経路,蓄圧室)
A:上部ノズル
B:スライディングノズルプレート
C:下部ノズル
D:ロングノズル
E:ロングストッパー
F:浸漬ノズル
G:内張り用耐火物
Claims (14)
- CaO成分を40質量%以上60質量%以下含み,CaO/ZrO2成分の質量比が0.67以上1.5以下であって,CaO結晶とCaZrO3結晶との共晶組織を含み,かつ,断面の組織中で観察できるCaO結晶の幅が50μm以下である,CaO-ZrO2組成物。
- CaO結晶の幅が20μm以下である,請求項1に記載のCaO-ZrO2組成物。
- 前記CaO-ZrO2組成物の表面には0.1μm以上5μm以下の厚さのCaCO3の被膜がCaO結晶及びCaZrO3結晶の表面に連続して存在する,請求項1又は請求項2に記載のCaO-ZrO2組成物。
- CaO原料とZrO2原料を,CaO成分とZrO2成分との組成上の液相線以上の溶融状態までに加熱する工程と,前記の溶融状態から固相線温度まで10℃/秒以上の速度で冷却する工程とを含む,請求項1から請求項3のいずれか1項に記載のCaO-ZrO2組成物の製造方法。
- 前記のCaO原料は,不可避の不純物を除き,溶融時の温度でCaOとなるCaO化合物又は生石灰から選択する1種又は複数種であって,前記のCaO原料の大きさは10mm以下であり,
前記のZrO2原料は,CaO安定化ZrO2,CaO部分安定化ZrO2又は未安定化ZrO2から選択する1種又は複数種であって,前記のZrO2原料の大きさは10mm以下である,請求項4に記載のCaO-ZrO2組成物の製造方法。 - 請求項1から請求項3のいずれか1項に記載のCaO-ZrO2組成物を含む耐火物であって,
CaO/ZrO2成分の質量比が0.5以上2.2以下であって,製造上不可避の成分を除く総量を100質量%とするときに,CaO成分及びZrO2成分を合計で65質量%以上98質量%以下,及びフリーの炭素成分を2質量%以上30質量%以下含む,CaO-ZrO2含有耐火物。 - CaO/ZrO2成分の質量比が0.67以上1.5以下である,請求項6に記載のCaO-ZrO2含有耐火物。
- 前記のフリーの炭素成分の含有量が4質量%以上15質量%以下であり,非酸化雰囲気内1000℃での熱膨張率が0.5%以下である,請求項6又は請求項7に記載のCaO-ZrO2含有耐火物。
- B2O3,TiO2,P2O5,及びV2O5から選択する1種又は2種以上の成分を合計で0.1質量%以上5.0質量%以下含み,
前記CaO-ZrO2組成物の少なくともCaO結晶の表面に,CaOと前記B2O3,TiO2,P2O5,及びV2O5から選択する1種又は2種以上の成分との化合物からなる0.1μm以上15μm以下の厚さの無機質被膜が形成されている,請求項6から請求項8のいずれか1項に記載のCaO-ZrO2含有耐火物。 - CaCO3が前記無機質被膜の少なくとも一部と接する状態で存在しており,かつ,CaCO3の含有量が0.1質量%以上約2.5質量%以下である,請求項6から請求項9のいずれか1項に記載のCaO-ZrO2含有耐火物。
- SiC,金属Si,及びB4Cから選択する1種又は複数種をさらに含有し,
SiCについては10質量%以下,
金属Si,B4Cについてはいずれか一方又は両方の合計で2質量%以下である,請求項6から請求項10のいずれか1項に記載のCaO-ZrO2含有耐火物。 - 請求項6から請求項11のいずれか1項に記載のCaO-ZrO2含有耐火物が,溶鋼と接触する部位の一部又は全部の領域に,溶鋼と接触する面から背面側に単層として配置されている鋳造用ノズル。
- 請求項6から請求項11のいずれか1項に記載のCaO-ZrO2含有耐火物が溶鋼に接触する面の一部又は全部の領域に配置され,その背面側には前記の溶鋼に接触する面の一部又は全部に配置された耐火物とは異なる組成の耐火物からなる層が配置された複数の層をなしている鋳造用ノズル。
- 内孔の一部にガス吹き込み用の耐火物からなる層を備えた,請求項12又は請求項13に記載の鋳造用ノズル。
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US (1) | US20220388910A1 (ja) |
EP (1) | EP4053486A4 (ja) |
JP (1) | JP7068255B2 (ja) |
CN (1) | CN114514212B (ja) |
AU (1) | AU2020376577B2 (ja) |
CA (1) | CA3152426A1 (ja) |
TW (1) | TWI819248B (ja) |
WO (1) | WO2021085325A1 (ja) |
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JPH0656523A (ja) * | 1992-08-04 | 1994-03-01 | Kurosaki Refract Co Ltd | 耐火材 |
JPH1110321A (ja) * | 1997-06-26 | 1999-01-19 | Shinagawa Refract Co Ltd | 鋳造用ノズル |
JP2003040672A (ja) | 2001-05-21 | 2003-02-13 | Shinagawa Refract Co Ltd | 鋼の連続鋳造耐火部材用耐火物 |
JP2009243723A (ja) * | 2008-03-28 | 2009-10-22 | Mitsubishi Heavy Ind Ltd | 金属溶解用ルツボ及びその製造方法 |
JP2010167481A (ja) | 2009-01-26 | 2010-08-05 | Kurosaki Harima Corp | 連続鋳造用ノズル |
WO2013081113A1 (ja) | 2011-12-01 | 2013-06-06 | 黒崎播磨株式会社 | 耐火物及び鋳造用ノズル |
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JPH0723254B2 (ja) * | 1992-01-27 | 1995-03-15 | 東京窯業株式会社 | 耐火材料 |
US7172013B2 (en) * | 2002-04-02 | 2007-02-06 | Krosakiharima Corporation | Binding structure of refractory sleeve for inner hole of nozzle for continuous casting |
JP2009221031A (ja) * | 2008-03-13 | 2009-10-01 | Kurosaki Harima Corp | ジルコニア−炭素含有耐火物及びその製造方法 |
JP6148476B2 (ja) * | 2013-01-25 | 2017-06-14 | 新日鐵住金株式会社 | ジルコニア−炭素含有耐火物及び鋼の連続鋳造用浸漬ノズル、並びに、ジルコニア−炭素含有耐火物の製造方法及び鋼の連続鋳造用浸漬ノズルの製造方法 |
JP6213101B2 (ja) * | 2013-09-26 | 2017-10-18 | 新日鐵住金株式会社 | スカム堰、薄肉鋳片の製造方法及び薄肉鋳片の製造装置 |
CN104072167A (zh) * | 2014-06-30 | 2014-10-01 | 沈阳化工大学 | 一种CaO防水化的处理方法 |
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2019
- 2019-10-31 JP JP2019199208A patent/JP7068255B2/ja active Active
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2020
- 2020-10-23 CA CA3152426A patent/CA3152426A1/en active Pending
- 2020-10-23 CN CN202080070108.1A patent/CN114514212B/zh active Active
- 2020-10-23 AU AU2020376577A patent/AU2020376577B2/en active Active
- 2020-10-23 WO PCT/JP2020/039864 patent/WO2021085325A1/ja unknown
- 2020-10-23 EP EP20883539.7A patent/EP4053486A4/en active Pending
- 2020-10-23 US US17/770,387 patent/US20220388910A1/en active Pending
- 2020-10-28 TW TW109137395A patent/TWI819248B/zh active
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US5151201A (en) * | 1988-07-01 | 1992-09-29 | Vesuvius Crucible Company | Prevention of erosion and alumina build-up in casting elements |
JPH0656523A (ja) * | 1992-08-04 | 1994-03-01 | Kurosaki Refract Co Ltd | 耐火材 |
JPH1110321A (ja) * | 1997-06-26 | 1999-01-19 | Shinagawa Refract Co Ltd | 鋳造用ノズル |
JP2003040672A (ja) | 2001-05-21 | 2003-02-13 | Shinagawa Refract Co Ltd | 鋼の連続鋳造耐火部材用耐火物 |
JP2009243723A (ja) * | 2008-03-28 | 2009-10-22 | Mitsubishi Heavy Ind Ltd | 金属溶解用ルツボ及びその製造方法 |
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V. S. STUBICAN, S. P. RAY: "Phase Equilibria and Ordering in the System ZrO2- CaO", JOURNAL OF THE AMERICAN CERAMIC SOCIETY, vol. 60, no. 11-12, December 1977 (1977-12-01), pages 534 - 537, XP055822368 * |
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Publication number | Publication date |
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CN114514212B (zh) | 2023-02-28 |
TW202124329A (zh) | 2021-07-01 |
TWI819248B (zh) | 2023-10-21 |
AU2020376577A1 (en) | 2022-04-21 |
JP2021070048A (ja) | 2021-05-06 |
CN114514212A (zh) | 2022-05-17 |
EP4053486A4 (en) | 2023-05-10 |
EP4053486A1 (en) | 2022-09-07 |
US20220388910A1 (en) | 2022-12-08 |
JP7068255B2 (ja) | 2022-05-16 |
AU2020376577B2 (en) | 2023-07-06 |
CA3152426A1 (en) | 2021-05-06 |
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