JP5341135B2 - Alumina-magnesia casting material and method for producing the same - Google Patents

Description

  The present invention relates to a casting material mainly composed of alumina and magnesia and a method for producing the same.

  Conventionally, in alumina / magnesia casting material used as lining material for molten steel containers such as ladle, tundish, etc., aggregates with a grain size of 8 mm or more are called coarse particles for the purpose of suppressing cracking and peeling due to heating and cooling. (For example, refer to Patent Documents 1 and 2, etc.). The coarse particles have a function of breaking cracks generated in the construction structure (matrix) and preventing the progress of cracks.

  For example, Patent Document 1 discloses a technique of adding 5 to 30% by weight of sintered alumina coarse particles in an alumina / magnesia casting material or an alumina / spinel / magnesia casting material. Patent Document 2 discloses a technique for adding a coarse aggregate of fused alumina and sintered spinel to a casting material mainly composed of alumina and spinel.

  On the other hand, in recent years, recycling of post-use refractories has been demanded from the viewpoint of the global environment, and most of them have been discarded, but the alumina and magnesia refractories used for the lining material of molten steel containers have been recycled. Use is also being attempted.

  For example, Patent Document 3 discloses an amorphous refractory for wet spraying to which an alumina-magnesia spent refractory smaller than 8 mm containing spinel produced during use is added. According to this technology, it is possible to add used alumina / magnesia refractories without reducing the corrosion resistance.

Japanese Patent Laid-Open No. 11-79855 JP 2000-128650 A Japanese Patent No. 2005-179130

  When dense sintered alumina or electrofused alumina having an apparent porosity smaller than 5% as used in Patent Documents 1 and 2 is used as the coarse aggregate, the familiarity between the coarse aggregate and the matrix is deteriorated. During heating, voids are formed at the boundary between the coarse aggregate and the matrix. Therefore, a sufficient anchor effect cannot be obtained, and the effect of preventing the progress of cracks cannot be obtained as much as expected. Moreover, since the metal is inserted into the gap between the coarse aggregate and the matrix, there is a problem that the durability of the refractory is lowered. Furthermore, since the density of dense sintered alumina and electrofused alumina is higher than that of the casting material used as the matrix, the coarse aggregate settles and separates when it is applied to a molten steel container under normal vibration conditions. Resulting in. As a result, not only the properties of the construction body are impaired, but in some cases, the service life may be significantly reduced.

  In addition, when an alumina / magnesia spent refractory having a particle size smaller than 8 mm as used in Patent Document 3 is added, the anchor effect is not exhibited due to the particle size being too small. The improvement effect cannot be obtained sufficiently. In addition, the used alumina / magnesia refractories to be added are required to generate spinel by heating in order to avoid the occurrence of cracks due to expansion. That is, an alumina / magnesia-based spent refractory with a low heating temperature during use and in which unreacted magnesia remains cannot be used. In order to satisfy this condition, it is necessary to separate and remove only the back surface and take out only the heated portion when disassembling the construction body made of the alumina / magnesia casting material after use. However, such separation is not easy and is not realistic because of high costs.

  In the present invention, it has been proposed in view of the above-described conventional circumstances, and firstly, when the coarse particles in which magnesia remains can be used while the crack suppression effect by the addition of coarse particles can be maximized. However, an object of the present invention is to provide an alumina magnesia cast material capable of obtaining a crack suppressing effect and a method for producing the same. A second object of the present invention is to provide an alumina-magnesia casting material and a method for producing the same, which can effectively use used alumina-magnesia refractories.

  The inventors of the present application are familiar with the matrix, do not generate voids between the coarse aggregate and the matrix, and do not generate a metal bar, and further have a sufficient anchoring effect. In addition, intensive research was conducted on the properties of coarse aggregates that can suppress crack growth. As a result, it was found that the use of a fired body having the same composition as that of the matrix as the coarse aggregate is effective in improving the durability of the alumina-magnesia casting material, and the present invention has been achieved.

That is, in the method for producing an alumina / magnesia casting material according to the present invention, first, a first raw material containing alumina, magnesia, silica, alumina cement and a dispersant is blended. Next, the blended first raw material is kneaded. Then, the kneaded first raw material is formed, and the formed first raw material is fired. Subsequently, the calcined first raw material is pulverized to produce alumina-magnesia coarse particles having a particle size of 8 to 50 mm and an apparent porosity of 10 to 30% . Then, MgO component, Al ₂ O ₃ component, SiO ₂ component includes CaO component, MgO component is 2 to 15 wt%, Al ₂ O ₃ component is 75 to 97.3 wt%, SiO ₂ component is 0.2 Addition of 5 to 40% by weight of the above-mentioned alumina / magnesia coarse particles to the second raw material having ~ 3.0% by weight and CaO component of 0.5 to 4.0% by weight Alumina-magnesia casting material is produced. Incidentally, alumina magnesia coarse grains, finite value of the SiO ₂ component is less than 5 wt%, MgO component is 2 to 15 wt%, Al ₂ O ₃ component is 70 to 97.3 wt%, the CaO component 0. It is preferably 5 to 4.0% by weight. In the present specification, the apparent porosity is a value measured according to JIS R2205.

  In this method for producing an alumina / magnesia casting material, coarsely formed alumina / magnesia coarse particles once molded and fired are blended. Since this alumina-magnesia coarse particle is once fired, it has higher strength and higher elastic modulus than the matrix portion, and exhibits an effect of suppressing crack propagation and an anchor effect. As a result, the alumina-magnesia cast material obtained by adding the coarse particles exhibits excellent spalling resistance.

  Further, the alumina / magnesia refractory obtained by kneading the first raw material is used as an alumina / magnesia casting material, and the above-described molding and firing are carried out by the use. A magnesia refractory can also be input into the above-mentioned crushing process.

  The alumina and magnesia refractories used as the alumina and magnesia casting material are kneaded and molded in the process of use, and are heated at the time of use. . Therefore, familiarity with the matrix is good, and voids are not generated between the coarse particles and the matrix. For this reason, the metal is not inserted into the gap, and the characteristics are stable as coarse particles, such as a sufficient anchor effect and crack growth inhibiting effect. Further, since kneading, molding, and firing are performed by actual use, no special cost is required for the process before pulverization. In addition, it is possible to effectively use the used alumina-magnesia casting material.

On the other hand, in another aspect, the present invention can also provide an alumina-magnesia casting material. That is, the alumina magnesia casting material according to the present invention was produced by firing, kneading, molding, and pulverizing the first raw material containing alumina, magnesia, silica, alumina cement, and a dispersant, Alumina magnesia coarse particles having a particle size of 8 to 50 mm and an apparent porosity of 10 to 30% contain MgO component, Al ₂ O ₃ component, SiO ₂ component and CaO component, and MgO component is 2 to 15% by weight. , With respect to the second raw material in which the Al ₂ O ₃ component is 75 to 97.3% by weight, the SiO ₂ component is 0.2 to 3.0% by weight, and the CaO component is 0.5 to 4.0% by weight. And 5 to 40% by weight as an outer shell.

  According to the present invention, there are provided an alumina / magnesia casting material and a method for producing the same, which are well-familiar with the matrix, do not generate voids at the boundary between the coarse particles and the matrix, and do not generate a metal ingot during use. Can do. Moreover, since this alumina / magnesia casting material has a high anchor effect and can also suppress the linear change rate of the construction body, it is also effective in suppressing cracks caused by heating and cooling. As a result, the spalling resistance can be improved without lowering the corrosion resistance and the infiltration resistance as compared with the conventional alumina / magnesia casting material to which coarse sintered alumina particles are added. Furthermore, it is possible to effectively use the used alumina / magnesia casting material.

The alumina-magnesia casting material in the present invention is produced by kneading, molding, firing and then pulverizing a first raw material containing predetermined alumina, magnesia, silica, alumina cement and a dispersant. Alumina / magnesia coarse particles having a diameter of 8 to 50 mm, containing MgO component, Al ₂ O ₃ component, SiO ₂ component and CaO component, MgO component is 2 to 15 wt%, Al ₂ O ₃ component is 75 to 97. 3% by weight, SiO ₂ component is 0.2 to 3.0% by weight, and CaO component is 0.5 to 4.0% by weight. It is characterized by that. The alumina / magnesia refractory obtained by kneading the first raw material has characteristics that can be used as an alumina / magnesia pouring material as it is, for example, as a lining material for a molten steel ladle.

  The alumina-magnesia casting material is mixed with the once-molded and fired alumina-magnesia coarse particles. Since this coarse particle is once fired, it has higher strength and higher elastic modulus than the matrix portion, and exhibits an anchor effect and a crack growth inhibiting effect. Therefore, the casting material containing the alumina / magnesia coarse particles has excellent spalling resistance. In addition, since the composition of the alumina / magnesia coarse particles is close to that of the matrix (second raw material) serving as a matrix, the difference in thermal expansion between the coarse particles and the matrix is small. The formation of voids between them is suppressed. Furthermore, since it has an appropriate porosity and the bulk density is close to that of the base material, it is well-familiar with the base material and is not easily separated during construction.

  In order to obtain coarse particles of alumina / magnesia, the first raw material is kneaded after adjusting the amount of water and other water added so as to obtain a desired tap flow value, and then molded. The molded body made of the first raw material is fired, and the fired first raw material is pulverized to produce coarse alumina / magnesia particles.

  The particle size (particle size) of the alumina / magnesia coarse particles is desirably 8 to 50 mm (8 mm or more and 50 mm or less). If the particle size is less than 8 mm, a sufficient anchor effect cannot be obtained, and a sufficient crack growth inhibiting effect cannot be obtained. Further, when the particle size is larger than 50 mm, there may be a problem in construction. This is because the construction thickness may be about 100 mm in a place where the use of an alumina / magnesia casting material is assumed, and if the particle size exceeds 50 mm, the strength of the structure is reduced.

The alumina / magnesia coarse particles include a SiO ₂ component, a MgO component, an Al ₂ O ₃ component, and a CaO component. The content of each component desirably satisfies the following conditions.

First, the SiO ₂ component is desirably a finite value of less than 5% by weight. When the SiO ₂ component is 5% by weight or more, even when it is added to the second raw material as coarse particles having a particle size of 8 to 50 mm, it is not desirable because the corrosion resistance of the construction body is lowered.

  The MgO component is desirably 2 to 15% by weight (2% by weight or more and 15% by weight or less). When the MgO component is less than 2% by weight, even when it is added to the second raw material as coarse particles having a particle size of 8 to 50 mm, it is not desirable because the corrosion resistance of the construction body is lowered. On the other hand, if the MgO component is more than 15% by weight, the slag infiltration of the construction body becomes large and induces structural spalling, which is not desirable. In this respect, the content of the MgO component is more preferably 5 to 10% by weight.

The Al ₂ O ₃ component is desirably 70 to 97.3% by weight (70% by weight or more and 97.3% by weight or less). When the Al ₂ O ₃ component is less than 70% by weight, even when it is added to the second raw material as coarse particles having a particle size of 8 to 50 mm, as a result of the increase in impurities, the corrosion resistance is reduced, or the sintering is excessive. It is not desirable because it progresses. From the viewpoint of maintaining corrosion resistance and suppressing sintering, the content of the Al ₂ O ₃ component is more preferably 80% by weight or more.

  The CaO component is desirably 0.5 to 4.0% by weight (0.5% by weight or more and 4.0% by weight or less). If the CaO component is less than 0.5% by weight, the amount of alumina cement is too small to obtain sufficient strength, and even when coarse particles are formed and fired, a sufficient anchor effect cannot be obtained due to insufficient strength. End up. Further, when the CaO component is more than 4.0% by mass, even when added to the second raw material as coarse particles having a particle size of 8 to 50 mm, slag infiltration is increased to induce structural spalling and corrosion resistance is also lowered. I will let you.

  The apparent porosity of the alumina / magnesia coarse particles is desirably 5 to 30% (5% or more and 30% or less). When the apparent porosity is less than 5%, the familiarity with the matrix is poor, and a sufficient crack growth inhibiting effect cannot be obtained. On the other hand, when the apparent porosity exceeds 30%, workability becomes a problem because a large amount of moisture is absorbed. More desirably, it is 10 to 25%. It is known that the apparent porosity can be adjusted by changing the particle size blend of the raw material used. Also in the present invention, the apparent porosity can be adjusted by applying the known technique.

  For firing the first raw material to obtain coarse alumina / magnesia particles, a temperature of about 800 to 1650 ° C. and a treatment for 1 hour or more can be used. When the temperature is higher than 1650 ° C., it is inconvenient because the sintering is promoted too much and the elastic modulus becomes too high. Moreover, if it is less than 800 degreeC or less than 1 hour, sintering does not progress and the effect | action as a coarse aggregate does not work. More desirably, it is 900-1500 degreeC and 3 hours or more. The fired first raw material is then pulverized by a pulverizer, adjusted to a predetermined particle size, and becomes the above-mentioned alumina-magnesia coarse particles.

The alumina / magnesia coarse particles are used by adding to the second raw material to be a matrix. The second raw material includes an MgO component, an Al ₂ O ₃ component, an SiO ₂ component, and a CaO component. The content of each component desirably satisfies the following conditions.

  First, the MgO component is desirably 2 to 15% by weight (2% by weight or more and 15% by weight or less). If the MgO component is less than 2% by weight, sufficient durability cannot be obtained because the corrosion resistance of the construction in use is insufficient. On the other hand, if it exceeds 15% by weight, slag infiltration increases during use, induces structural spalling and increases peeling damage, resulting in a decrease in durability. From the balance between corrosion resistance and infiltration resistance, the content of the MgO component is more preferably 5 to 10% by weight.

The Al ₂ O ₃ component is desirably 75 to 97.3% by weight (75% by weight or more and 97.3% by weight or less). If the Al ₂ O ₃ component is less than 75% by weight, the amount of impurities increases, resulting in insufficient corrosion resistance. The content of the Al ₂ O ₃ component is more desirably 85% by weight or more, and better corrosion resistance can be obtained.

The SiO ₂ component is preferably 0.2 to 3.0% by weight (0.2% to 3.0% by weight). When the SiO ₂ component is less than 0.2% by weight, hot deformability cannot be obtained, and cracks may occur between the coarse particles and the matrix, possibly reducing the durability. On the other hand, when the SiO ₂ component is larger than 3.0% by weight, the corrosion resistance is greatly lowered, which is not desirable. More desirably, the content of the SiO ₂ component is 0.5 to 1.5% by weight.

  The CaO component is preferably 0.5 to 4.0% by weight (0.5% to 4.0% by weight). If the CaO component is less than 0.5% by weight, sufficient strength cannot be obtained and peeling damage is induced. On the other hand, if the CaO component exceeds 4.0% by weight, the infiltration resistance is lowered and the corrosion resistance is insufficient, so that sufficient durability cannot be obtained.

  The addition amount of the alumina / magnesia coarse particles relative to the second raw material is preferably 5 to 40% by weight as an outer shell. If the amount of the alumina / magnesia coarse particles added is less than 5% by weight of the outer shell, a sufficient crack growth inhibiting effect cannot be obtained. Further, if the amount added exceeds 40% by weight, the influence on the fluidity of the casting material is large, and as a result of adding a large amount of water to lower the fluidity, the properties of the casting material are deteriorated. More preferably, the addition amount of the alumina / magnesia coarse particles is 15 to 30% by weight as an outer shell.

  By the way, a used alumina / magnesia casting material (hereinafter simply referred to as a used casting material) can be used as the alumina / magnesia coarse particles. Hereinafter, an example of a procedure for generating coarse alumina / magnesia grains from the used casting material will be described.

  When the used ladle is dismantled, first, only the MgO-C brick used in the SL (slag line) part is disassembled and received in a bucket and collected. Thereafter, the ML (metal line) surface of the remaining alumina / magnesia casting material is crushed with a dismantling machine or the like to roughly peel off the bare metal, slag deposits, and infiltrating layer. After this cleaning operation, only the alumina / magnesia casting material, which is the lining, is dismantled and collected so that rholite and high alumina perm bricks will not fall off. At this time, it is desirable that the alumina / magnesia casting material is crushed by a dismantling machine to a size of a human head. The used casting material collected in this way is separated into a portion with much infiltration and a portion with little infiltration, and the used casting material with less infiltration is used as coarse alumina / magnesia particles. The used cast material with little infiltration is pulverized with a crusher, and ironed, dried and classified to be collected as recycled material.

  As described above, the alumina / magnesia coarse particles obtained from the used casting material are kneaded and molded in the process of use, and since they are heated at the time of use, the sintering proceeds appropriately. Yes. Therefore, it becomes high strength and high elastic modulus as compared with the matrix portion. Moreover, the familiarity with a matrix is good and a space | gap is not produced | generated between a coarse grain and a matrix. For this reason, there is no formation of metal in the gap, and the characteristics are stable as coarse particles, such as having a sufficient anchor effect and suppressing crack propagation. Therefore, by using the coarse alumina / magnesia particles obtained from the used casting material, it is possible to produce an alumina / magnesia casting material having excellent durability at low cost.

  In addition, generally used dispersing agents can be used for the casting material composed of the first raw material and the second raw material. For example, organic dispersants such as polycarboxylates and polycarboxylic acid ethers, and inorganic dispersants such as phosphates can be used. In addition, when these casting materials are kneaded, water is usually added to obtain a desired tap flow value. However, water-based binders such as colloidal silica and colloidal alumina can be used in place of water (in this embodiment, “moisture” is used as a general term for these binders added during kneading). ing). Furthermore, general methods can be used for the kneading method, the kneading equipment, the molding method or the construction method.

  In addition to the above, a thickener, a curing regulator, organic fibers, metallic aluminum, and the like can be added for the purpose of improving fluidity and the like within a range not impairing the effects of the present invention.

Examples and comparative examples are presented below to describe the alumina-magnesia casting material of the present invention. In this example, the pulverized used casting material (used casting materials A to C) and the casting material calcined product (firing temperature 1000 ° C., unused product: casting material calcined product D) as alumina / magnesia coarse particles. ) Is used. Table 1 below shows chemical components, mineral compositions, and other physical properties of the used casting materials A to C and the fired product D of the casting material. The used casting material C shown in Table 1 has a SiO ₂ component content of 10% by weight and an apparent porosity of 4.2%, so that the used casting material in which the effects of the present invention cannot be obtained. It corresponds to.

  In Table 1, “-” means not present. In the mineral composition, “++” means that the content is high, and “+” means that the content is high next to “++”. In the particle diameter, “XY” means that the particle diameter includes only particles included in the range of Ymm or more and Xmm or less.

The above-mentioned used casting materials A to C, casting material fired product D, conventional sintered alumina (particle size 30-10 mm, apparent porosity 3%) are used as coarse particles, and the mixing ratios shown in Tables 2 and 3 Create a compound by blending, adjust the amount of water added so that the tap flow value according to the JIS R2521 flow test is 180 mm, knead, and then cast into a metal frame of a predetermined shape (casting) Thus, a sample (specimen) of the alumina / magnesia casting material was produced. In this example, sintered alumina aggregate (particle size: 7-1 mm, less than 1 mm), calcined alumina, magnesia fine powder, silica fine powder, and high alumina cement are used as the second raw material to be a matrix, and the blending weight is 100 weight. % And the dispersant and organic fiber are added as outer shells. The chemical composition of the high alumina cement is Al ₂ O ₃ : 74.0% by weight, CaO: 24.6% by weight, and contains a small amount (1.4% by weight) of other impurities.

  In Examples 1 to 6 and Comparative Examples 1 and 3 shown in Table 2, the blending amounts of sintered alumina aggregate, calcined alumina, magnesia fine powder, silica fine powder, high alumina cement, dispersant and organic fiber are fixed, In Comparative Example 2, the amount of silica fine powder is decreased in accordance with the increase in the amount of calcined alumina. In Examples 7 to 11 and Comparative Examples 4 to 7 shown in Table 3, the amounts of sintered alumina aggregate, high alumina cement, dispersant and organic fiber are fixed, calcined alumina, magnesia fine powder, silica The mixing ratio of fine powder is changed.

  For each of Examples 1 to 11 and Comparative Examples 1 to 7, tests of spalling resistance (thermal shock resistance), erosion depth (corrosion resistance), infiltration depth (infiltration resistance), and post-heating linear change rate were performed. Tables 2 and 3 show the evaluation results for each item.

  In the spalling test, a sample having a shape of 230 mm × 65 mm × 115 mm is heated and cooled from above with the surface of 65 mm × 115 mm facing upward, and the sample after the test is cut and evaluated. Heating and cooling conditions are 1500 ° C.-45 minutes heating and air cooling 15 minutes cooling alternately repeated 6 times. The symbol in the table indicates that “◯” indicates no crack, “Δ” indicates that a practically acceptable microcrack of less than 0.5 mm has occurred, and “×” indicates 0.5 mm or more. This shows that a thick crack occurred.

  The erosion depth and infiltration depth were evaluated by a rotating drum erosion test. The test was conducted at arc-heated 1650 ° C. for 3 hours with the erodant changed every hour. Slag with basicity (C / S) = 3 was used as the erodant. After the test, the sample was cut to measure the erosion depth and the infiltration depth. When the erosion depth of Example 1 was set to 100, and when the infiltration depth of Example 1 was set to 100, The infiltration depth is indexed and evaluated. It shows that it is high corrosion resistance and high infiltration resistance, so that an index | exponent is small.

  The post-heating linear change rate is a measurement result after heating under conditions of 1500 ° C. for 3 hours in accordance with JIS R2554.

  As can be understood from Tables 2 and 3, in Examples 1 to 11, the spalling resistance improvement effect is clearly obtained as compared with Comparative Examples 1 to 7. That is, it can be said that each Example 1-11 which concerns on this invention is excellent comprehensively about each characteristic of spalling resistance, corrosion resistance, infiltration resistance, and form stability.

  In Table 2, Examples 1 to 5 and Comparative Examples 1 to 3 show the results when the above-mentioned used casting materials A to C and conventional sintered alumina are added as coarse particles.

  In particular, for example, from Examples 2 and 3, the used cast material B (7-3 mm), which has been used in the past, has been used as a dense cast alumina with coarse particles and small particle size. It can be understood that the effect of improving the spalling resistance can be obtained even when added in combination with the used casting material B (45-15 mm) having a large particle size. Moreover, it is understood from Examples 1, 4, and 5 that even when only the used casting material A and the used casting material B (45-15 mm) having a large particle size are added, the effect of improving the spalling resistance can be obtained. it can.

  On the other hand, as can be understood from Comparative Example 1, the spalling resistance is not improved even when only the used casting material B (7-3 mm) having a small particle diameter is added. Further, as can be understood from Comparative Example 2, even when the used casting material B (45-15 mm) having a large particle size is used, the silica fine powder amount of the alumina / magnesia casting material is as low as 0.1% by weight. The spalling resistance decreases. This is because the hot creep property (deformability) of the casting material is not sufficient, and cracks are generated in the construction body due to the expansion caused by the spinel formation reaction caused by the periclase staying in the used casting material B. Furthermore, as can be understood from Comparative Example 3, when the spent cast material C having a high silica component and a low apparent porosity of 4.2% is used, the spalling resistance is lowered and the erosion depth is greatly increased. (Corrosion resistance is reduced). This is because, like the used casting material C, when the silica component is high and the apparent porosity is low, the familiarity with the matrix is deteriorated.

  Moreover, in Example 6, not the used casting material, but the alumina magnesia coarse particles prepared by pulverizing the fired product D of the casting material are added. Similar to the used casting materials A and B, the spalling resistance improving effect is obtained without reducing the corrosion resistance and the infiltration resistance.

  On the other hand, in Table 3, in Examples 7-11 and Comparative Examples 5-7, about the case where the above-mentioned used casting material B (45-15mm) with a large particle size is added as a coarse particle, the composition ratio of a 2nd raw material The result when changing is shown. Moreover, in the comparative example 4, the result about the case where the conventional sintered alumina is added as a coarse grain is shown.

  Specifically, for example, from Examples 7 to 9 and Example 5 in Table 2, when the blending ratio of calcined alumina and silica fine powder is changed, the infiltration depth and heating are increased as the silica fine powder content increases. Although it can be confirmed that the rate of change in the back line decreases and the depth of erosion increases, it can be understood that good characteristics can be obtained for each of the spalling resistance, corrosion resistance, infiltration resistance, and shape stability characteristics. Further, from Examples 10 and 11 and Example 5, when the blending ratio of calcined alumina and magnesia fine powder is changed, with the increase in the magnesia fine powder content, the infiltration depth and the linear change rate after heating increase. Although the tendency for the erosion depth to decrease can be confirmed, it can be understood that good characteristics can be obtained for each of the spalling resistance, corrosion resistance, infiltration resistance, and shape stability characteristics.

  On the other hand, as can be understood from Comparative Example 4, when the amount of magnesia fine powder is as low as 1.5% by weight, the amount of magnesia added is too small, and thus the corrosion resistance is lowered. In addition, since only dense sintered alumina that has been conventionally used is added as coarse particles, voids are formed around the coarse particles, and cracks cannot be stopped, and cracks having a large width are generated. Further, as can be understood from Comparative Example 5, even when the used casting material B (45-15 mm) having a large particle size is used, when the amount of fine magnesia powder is as high as 18% by weight, the amount of magnesia added is too large. Therefore, the infiltration resistance is extremely lowered. In addition, the amount of expansion after heating is large, and the spalling resistance is also lower than in each example. Furthermore, as can be understood from Comparative Example 6, even when the used casting material B (45-15 mm) having a large particle size is used, when the amount of fine silica powder is as high as 4% by weight, the amount of silica added is too large. For this reason, the construction body itself contracts, reducing the spalling resistance. In addition, the corrosion resistance was lower than in each example. In addition, the comparative example 7 is a comparative example to which coarse particles are not added, and it can be understood that each example has improved spalling resistance.

  As described above, according to each embodiment of the present invention, an alumina-magnesia casting material having comprehensively excellent characteristics can be obtained.

  The present invention can provide an alumina / magnesia casting material with improved spalling resistance without reducing corrosion resistance and infiltration resistance as compared with the prior art. It is useful as a production method.

Claims (6)

A step (a) of blending a first raw material containing alumina, magnesia, silica, alumina cement and a dispersant;
A step (b) of kneading the first raw material blended in the step (a);
A step (c) of forming the first raw material kneaded in the step (b);
A step (d) of firing the first raw material formed in the step (c);
Crushing the first raw material fired in the step (d) to produce coarse alumina / magnesia particles having a particle size of 8 to 50 mm and an apparent porosity of 10 to 30% ;
Including MgO component, Al ₂ O ₃ component, SiO ₂ component, CaO component, MgO component is 2-15 wt%, Al ₂ O ₃ component is 75-97.3 wt%, SiO ₂ component is 0.2-3 0.02% by weight and the second raw material having a CaO component of 0.5 to 4.0% by weight, the alumina / magnesia coarse particles produced in the step (e) are 5 to 40% by weight. Step (f) of adding%,
A method for producing an alumina magnesia casting material, comprising: The alumina / magnesia coarse particles have an SiO ₂ component of less than 5% by weight, an MgO component of 2 to 15% by weight, an Al ₂ O ₃ component of 70 to 97.3% by weight, and a CaO component of 0.5 to 4. The method for producing an alumina magnesia cast material according to claim 1, which is 0% by weight.   The alumina / magnesia refractory produced in the steps (a) and (b) is used as an alumina / magnesia casting material, and the used alumina / magnesia refractory material that has undergone the steps (c) and (d) by the use The method for producing an alumina / magnesia casting material according to claim 1 or 2, wherein the magnesia refractory is added to the step (e). A first raw material containing alumina, magnesia, silica, alumina cement, and a dispersant is kneaded, molded, fired, and then pulverized to produce a particle size of 8 to 50 mm and an apparent porosity of 10 to 30 % Of alumina / magnesia coarse particles containing MgO component, Al ₂ O ₃ component, SiO ₂ component, CaO component, MgO component is 2 to 15% by weight, Al ₂ O ₃ component is 75 to 97.3% by weight The second raw material having a SiO ₂ component of 0.2 to 3.0% by weight and a CaO component of 0.5 to 4.0% by weight contains 5 to 40% by weight of alumina, Magnesia casting material. The alumina / magnesia coarse particles have an SiO ₂ component of less than 5% by weight, an MgO component of 2 to 15% by weight, an Al ₂ O ₃ component of 70 to 97.3% by weight, and a CaO component of 0.5 to 4. The alumina magnesia cast material according to claim 4, which is 0% by weight.   The alumina-magnesia casting material according to claim 4 or 5, wherein the alumina-magnesia coarse particles are pulverized used alumina-magnesia casting material.