JP2010235342A - Monolithic refractory for blast furnace iron spout - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a monolithic refractory for a blast furnace iron spout having both of heat spalling resistance and erosion resistance. <P>SOLUTION: The monolithic refractory for blast furnace iron spout includes fire resistant powders comprising coarse grains where the content of electrofused alumina having a TiO<SB>2</SB>content of 1.5 mass% or more is 60 mass% or more and which have a grain diameter of 1 mm or more, middle grains where the content of a silicon carbide raw material is 90 mass% or more and which have a grain diameter of 75 μm or more and less than 1 mm and fine grains where the total content of three materials, which are an alumina-based raw material, a boron carbide raw material having a content of 5-40 mass% expressed in terms of outer percentage to the alumina-based raw material and metallic silicon having a content of 5-60 mass% expressed in terms of outer percentage to the alumina-based raw material, is 20 mass% or more and where the balance is mainly the silicon carbide raw material having a grain diameter of less than 75 μm and an additive containing a binding agent. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an irregular refractory for blast furnace tapping which constitutes the lining of the blast furnace tapping.

  Blast furnace tapping is a facility that separates the hot metal and slag discharged from the blast furnace and serves as a runway that guides the hot metal to the kneading car. In the operation of the blast furnace, since the tapping is performed intermittently, the blast furnace tapping is subjected to a thermal shock caused by repetition of tapping and its suspension. Therefore, heat resistant spalling properties are required for the lining of the blast furnace feed.

  Conventionally, in order to impart heat resistant spalling properties to the lining of the blast furnace tuna, an approach by increasing its volume stability has been taken. This approach is based on the technical idea of increasing the volume stability of the lining and suppressing the occurrence of thermal distortion that causes thermal spalling.

  Patent Documents 1 and 2 disclose an amorphous refractory for blast furnace tapping that employs such a technical idea, in which all coarse grains having a particle diameter of 1 mm or more are made of a silicon carbide raw material. Since the silicon carbide raw material has a small coefficient of thermal expansion, it has been considered that the volume stability of the lining can be increased by using this for coarse particles, and heat resistant spalling properties are imparted.

  Patent Document 1 describes that electrofused alumina has a large coefficient of thermal expansion and is not preferable from the viewpoint of heat-resistant spalling properties (Patent Document 1, page 2, left column, lines 9 to 15).

Japanese Patent Publication No. 6-8223 JP-A-5-70250 Japanese Patent No. 2617086 Japanese Patent Publication No. 1-332187 JP-A-61-14175

  A configuration excellent in volume stability can suppress thermal strain, but has almost no effect of absorbing generated thermal strain. For this reason, a limit has arisen in improving heat-resistant spalling property only by improving volume stability.

  According to the research of the present inventor, in contrast to the conventional technical idea that enhances volume stability, it is possible to improve heat-resistant spalling properties by using fused alumina with a large thermal expansion coefficient for coarse particles. It was found. This is mainly due to the fact that the coarse fused alumina contracts more than the medium and fine particles during the period when the brewing is suspended, so that fine voids can be formed around them and thermal strain can be absorbed by the fine voids. by.

Patent Document 3 also recommends the use of fused alumina, but the estimation of the mechanism that leads to the prevention of thermal spalling is different from the above consideration of the present inventor. That is, Patent Document 3 explains that a fused structure containing TiO ₂ has a loose crystal structure and can absorb thermal strain by itself (see paragraph 0035 of Patent Document 3). ).

  However, the use of fused alumina prevented thermal spalling, rather than absorption of thermal strain by fused alumina itself, rather than the formation of fine voids around fused alumina as described above. It depends.

  According to the above consideration by the inventors of the present application, in order to efficiently form fine voids, it is desired that most of the coarse particles are composed of fused alumina, and the medium and fine particles are excellent in volume stability. However, Patent Document 3 does not disclose the above mechanism, and does not disclose a configuration capable of efficiently forming fine voids, leaving room for improvement in terms of improving heat-resistant spalling properties.

  For example, Invention Example 1 in Table 4 of Patent Document 3 does not clearly disclose the proportion of fused alumina in the coarse particles, and the medium particles and fine particles have a configuration that can exhibit sufficient volume stability. Absent. Inventive Examples 2 to 8 in Table 4 are understood that most of the coarse particles are composed of a silicon carbide raw material.

  Patent Documents 4 and 5 disclose an example in which all of the coarse particles are fused alumina, but it is not specifically disclosed what fused alumina is used. Depending on the electrofused alumina used, fine voids cannot be formed sufficiently even if it is used in coarse particles. Further, Patent Documents 4 and 5 are not preferable in terms of erosion resistance because they contain a large amount of fused alumina in the medium and fine particles.

  An object of the present invention is to provide an amorphous refractory for blast furnace discharge having both heat-resistant spalling properties and erosion resistance.

According to one aspect of the present invention, the fused alumina having a TiO ₂ content of 1.5% by mass or more comprises coarse particles having a particle size of 1 mm or more occupying 60% by mass or more, and the silicon carbide material is 90% by mass or more. Medium grains having a particle size of 75 μm or more and less than 1 mm, an alumina material, a boron carbide material in an amount of 5 to 40% by mass with respect to the alumina material, and 5 to 60% by mass with respect to the alumina material The total amount of metal silicon accounts for 20% by mass or more, and the balance consists of a refractory powder composed of fine particles having a particle size of less than 75 μm mainly composed of a silicon carbide raw material, and an additive containing a binder. An unshaped refractory for blast furnace output is provided.

  During the brewing process (hereinafter referred to as the brewing period), the coarse particles and the medium particles are thermally expanded by receiving heat from the molten metal, and the above three parties interact with each other in the fine particles. A solid solution containing mullite precipitates in the matrix portion surrounding the grains.

During the brewing pause (hereinafter referred to as the brewing pause period), the coarse-grained fused alumina contracts more than the medium grains and fine grains (matrix part), and the fine grains around the coarse-grained fused alumina are fine. A void is formed. By using a fused TiO ₂ having a particularly large thermal expansion coefficient of TiO ₂ content of 1.5% by mass or more, fine voids can be efficiently formed. Moreover, precipitation of the said solid solution to a matrix part suppresses shrinkage | contraction by glass production | generation, and contributes to formation of a fine space | gap.

  At the same time that the blast furnace tuna begins to cool, thermal strain tends to occur in the lining. However, since the thermal strain is absorbed by the fine voids, thermal spalling is prevented. Although it is difficult to say that fused alumina is excellent in erosion resistance, the use of this as coarse particles can prevent its erosion, and the solid silicon carbide material and the above solid solution in the matrix portion have excellent erosion resistance. Therefore, it can also have erosion resistance.

  In this specification, the amorphous refractory refers to a powder composition in which a construction liquid (typically water) is not added.

  The irregular shaped refractory for blast furnace leaving consists of a refractory powder and an additive containing a binder.

  The refractory powder consists of coarse particles having a particle size of 1 mm or more, medium particles having a particle size of 75 μm or more and less than 1 mm, and fine particles having a particle size of less than 75 μm.

  In the present specification, the particle diameter of D or more means that the particles remain on a standard sieve having an opening D defined in JIS-Z8801, and the particle diameter of less than D means that the particles Means passing through the same standard sieve with mesh opening D.

  The refractory powder is preferably composed of coarse particles: 40 to 60% by mass, fine particles: 20 to 40% by mass, and medium particles: 5 to 40% by mass.

  Coarse grains comprise 60 mass% or more of fused alumina. Electrofused alumina shrinks during the resting period and forms fine voids with the surrounding tissue. Since thermal stress generated in the lining is absorbed by the fine voids, thermal spalling can be prevented.

  The larger the proportion of fused alumina in the coarse particles, the better. Specifically, the proportion of the fused alumina in the coarse particles is preferably 70% by mass or more, more preferably 80% by mass or more, and most preferably 100% by mass.

As the electrofused alumina, one containing 1.5% by mass or more of TiO ₂ is used. When the TiO ₂ content is less than 1.5% by mass, it is not possible to form a fine void sufficiently. As the fused alumina having a higher TiO ₂ content has a larger coefficient of thermal expansion, the ability to form fine voids is higher. The TiO ₂ content of the fused alumina is preferably 2% by mass or more, and more preferably 3% by mass or more.

  The middle grains are composed of 90% by mass or more, preferably 95% by mass or more, more preferably all of silicon carbide raw material. Since the silicon carbide-based material has excellent erosion resistance against molten metal, particularly slag, and hardly wets the slag, it has the effect of increasing the erosion resistance of the lining. Moreover, since it is excellent also in volume stability at the time of receiving a temperature change, it acts effectively on formation of the said fine space | gap.

  The fine particles comprise 20% by mass or more of three materials: an alumina material, a boron carbide material, and metal silicon. The above three parties interact in a temperature range of about 800 ° C. or more during the brewing period to form a solid solution in the matrix portion.

Specifically, Al ₂ O ₃ derived from an alumina raw material, B ₂ O ₃ generated from a boron carbide raw material, and SiO ₂ generated from metallic silicon interact with each other, and mullite (3Al ₂ O _3. 2SiO ₂₎ a solid solution was _{9A1 2 O 3 · 2B 2 O} 3 of columnar crystals (hereinafter, simply referred to as solid solutions.) is deposited so entangled in the matrix portion.

  In the following description, the terms “alumina raw material”, “boron carbide raw material”, and “metal silicon” refer to those constituting fine particles unless otherwise specified.

As the alumina material, for example, one or more selected from calcined alumina, electrofused alumina, sintered alumina, bauxite, and shale shale can be used. Among them, those having an Al ₂ O ₃ content of 99% by mass or more are preferable.

  The alumina raw material itself is not excellent in erosion resistance as compared with the silicon carbide raw material, but if used as a raw material for forming a solid solution, other silica and calcia present in the matrix It can suppress vitrification by intervening.

  The blending ratio of the boron carbide raw material is 5 to 40% by mass on the basis of the alumina raw material. If it is less than 5% by mass, a solid solution is not sufficiently formed. When it exceeds 40% by mass, there is an excessive boron carbide raw material that does not contribute to the formation of a solid solution, and the excessive boron carbide raw material is vitrified, which causes a reduction in heat-resistant spalling properties.

  The ratio of the metallic silicon is 5 to 60% by mass based on the alumina material. If it is less than 5% by mass, a solid solution is not sufficiently formed. When it exceeds 60% by mass, there is surplus metal silicon that does not contribute to the formation of the solid solution, and the surplus metal silicon is vitrified, which causes a decrease in heat-resistant spalling property.

  By forming the solid solution by the above three parties, the porosity of the lining is reduced, the strength is improved, and the erosion resistance against hot metal and slag is improved. Moreover, since the solid solution is excellent in volume stability when subjected to a temperature change, it effectively acts on the formation of the fine voids.

  When the total amount of the above three occupying the fine particles is less than 20% by mass, the formation of the solid solution becomes insufficient. The total amount of the above three occupying the fine particles is preferably 60% by mass or less. Thereby, it can prevent that the lining structure | tissue becomes high elasticity too much and the improvement effect of the heat resistant spalling property by the said fused alumina is attenuated.

  The remainder other than the above three in the fine particles is mainly composed of silicon carbide raw material. Since the silicon carbide-based raw material hardly interacts with the above three parties, it is difficult to inhibit formation of a solid solution. The fine silicon carbide raw material contributes to the improvement of the erosion resistance and the volume stability of the matrix portion as in the case of the solid solution.

  The remainder other than the above three in the fine particles may be composed of only the silicon carbide-based raw material, or composed of the silicon carbide-based raw material and a small amount, preferably other raw material of 15% by mass or less in proportion to the fine particles. May be.

  The other raw materials are selected from, for example, siliceous raw materials such as silica flour and clay, carbonaceous raw materials such as pitch, graphite, resin and carbon black, silicon nitride raw materials such as silicon iron nitride, and titania raw materials. One or more. If at least these raw materials are in a small amount, it is difficult to inhibit the formation of the solid solution, so that the effect due to the formation of the solid solution is hardly impaired.

However, it is preferable not to contain a siliceous raw material. The siliceous raw material contains SiO ₂ which is a constituent molecule of the solid solution, but metal silicon reacts preferentially over the siliceous raw material when forming the solid solution. For this reason, the siliceous raw material hardly participates in the formation of the solid solution, and can remain as it is to be vitrified to cause a decrease in heat resistant spalling property.

  As the binder, for example, one or more selected from alumina cement, colloidal silica, hydraulic transition alumina, phosphate, and silicate can be used. The addition amount is preferably 1 to 10% by mass as an outer coating with respect to the refractory powder.

  As the additive, only a binder may be used, but one or more selected from, for example, a dispersant, a curing time adjusting agent, and an explosion preventing agent may be used in combination.

  Examples of the dispersant include alkali metal phosphates such as sodium tripolyphosphate, sodium hexametaphosphate, sodium ultrapolyphosphate, and sodium acid hexametaphosphate, polycarboxylates such as sodium polycarboxylate, alkylsulfonates, and aromatics. One or more selected from sulfonates, sodium polyacrylate, sodium sulfonate, and the like can be used. The addition amount is preferably 0.01 to 1% by mass as an outer coating with respect to the refractory powder.

  The curing time adjusting agent includes a curing accelerator and a curing retarder. As the curing accelerator, for example, one or more selected from slaked lime, calcium chloride, sodium aluminate, lithium carbonate, and the like can be used. As the curing retarder, for example, one or more selected from boric acid, oxalic acid, citric acid, gluconic acid, sodium carbonate, sugar and the like can be used.

  Examples of the explosion preventing agent include metal aluminum, aluminum lactate, and organic fiber (eg, vinylon fiber, polyethylene fiber, polypropylene fiber, etc.). The addition amount is preferably 0.02 to 3% by mass as an outer coating with respect to the refractory powder. Metal fibers can also be used as an anti-peeling agent.

  Examples of the construction method of the amorphous refractory include casting, pumping, wet spraying, dry spraying, and troweling. In any case, a construction liquid (typically water) is added to the amorphous refractory material during construction. The addition amount is preferably 4 to 15% by mass on the outside of the amorphous refractory.

  When using the wet or dry spraying method, one or more quick setting selected from, for example, silicate, aluminate, carbonate, sulfate, etc. is used to prevent dripping from the work surface. It is preferable to use an agent as the additive. The addition amount is preferably 0.01 to 2% by mass on the outside of the amorphous refractory.

  The construction site is not particularly limited as long as it is a blast furnace lining. Due to the difference in specific gravity between slag and pig iron, hot metal flows below the blast furnace discharge and slag flows above. Of the blast furnace lining, the interface between the slag and the atmosphere is called a slag line, and the interface between the slag and the hot metal is called a metal line.

  This amorphous refractory is particularly suitable for slag lines for the following reasons.

  In the slag line, in general, the erosion resistance tends to improve as the content of the silicon carbide raw material increases. In this regard, the amorphous refractory is easy to adopt a configuration excellent in slag resistance because the silicon carbide raw material is blended in the middle and fine grains.

  The hot water level rises during the tapping period, and the hot water level drops during the tapping period. For this reason, the hot water surface, that is, the slag line located at the interface between the slag and the atmosphere is more susceptible to thermal shock than the metal line. In this respect, the amorphous refractory is excellent in heat-resistant spalling properties, and therefore is not easily peeled off or cracked even when subjected to thermal shock.

Tables 1 to 5 show examples, comparative examples, and evaluation results. In Tables 1 to 4, the TiO ₂ contents of the fused aluminas A, B, and C are 3% by mass, 1.5% by mass, and 0.8% by mass, respectively. In each example, alumina cement was used as the binder, and sodium hexametaphosphate was used as the dispersant.

  The evaluation was performed on a test piece obtained by adding 6% by mass of industrial water to the amorphous refractory of each example, pouring it into a predetermined formwork, curing and drying.

  The number of times of durability was obtained in the following manner. The test piece is heated at 1400 ° C. for 30 minutes and then air-cooled for 30 minutes to give a thermal shock. This series of operations is defined as one cycle, and the cycle is repeated until the test piece collapses. The number of cycles required for the collapse of the test piece is the number of durability. However, the upper limit of the number of cycles was 20 times. The greater the durability, the better the heat resistant spalling properties.

  The erosion index was determined as follows. The test piece is eroded by the rotational erosion method. Blast furnace slag is used as the erodant, and the erosion test is conducted at 1500-1600 ° C. for 10 hours. After the erosion test, the size of the test piece is measured. A value obtained by dividing the erosion dimension of the test piece of each example by the erosion dimension of the test piece of Example 1 and multiplying by 100 is the erosion index. The smaller the erosion index, the better the erosion resistance.

  Examples 1 to 6 all satisfy the provisions of the present invention, and have both heat-resistant spalling properties and erosion resistance.

In Example 2, fused alumina B was used for the coarse particles. From the comparison with Example 1, the TiO ₂ content of the fused alumina used for the coarse particles is higher in terms of heat resistance and spalling properties. Is preferable.

  In Example 3, the proportion of fused alumina in the coarse particles was reduced to 90% by mass by blending a small amount of silicon carbide raw material into the coarse particles. From the comparison with Example 1, it can be said that it is preferable that all of the coarse particles are composed of fused alumina in terms of heat-resistant spalling properties. That is, the higher the proportion of fused alumina in the coarse particles, the higher the ability to form fine voids.

  In Example 4, a small amount of fused alumina was blended in the middle grain. From the comparison with Example 1, it is preferable that the whole grain is composed of a silicon carbide raw material in terms of erosion resistance. It can be seen that the heat-resistant spalling properties are difficult to improve even if electrofused alumina is blended in the middle grains. Since the fused alumina blended in the middle grains has a small grain size, it not only has a small ability to form fine voids, but also causes a decrease in erosion resistance.

  In Example 5, the silicon nitride raw material and the titania raw material are blended into the fine particles, and it can be seen from the comparison with Example 1 that even if these are blended into the fine particles, the heat resistant spalling property is hardly affected. . However, in terms of erosion resistance, the remainder of the fine particles except for the alumina material (calcined alumina in this case), boron carbide material, and metal silicon is composed only of silicon carbide material and carbonaceous material. Is preferable.

  In Example 6, a siliceous raw material (here, silica flour) was blended into fine particles, and the heat-resistant spalling property was in an acceptable range but was inferior. From the comparison with Example 1, it is preferable not to mix | blend a siliceous raw material with a fine particle from the point of heat resistant spalling property. The siliceous raw material is vitrified and causes a reduction in heat-resistant spalling properties.

  In Examples 7 to 10, the proportion of coarse particles in the refractory powder was changed in the range of 40 to 60% by mass, and both had heat-resistant spalling properties and erosion resistance. Although not shown in the table, if the proportion of coarse particles in the refractory powder exceeds 60% by mass, the formation of fine voids becomes excessive and the strength of the refractory structure itself becomes small, or heat resistant spalling. There was a tendency to saturate the effect of improving sex. From Table 2, it can be said that the proportion of coarse particles in the refractory powder is preferably 45 to 55% by mass in terms of the balance between the heat resistant spalling property and the erosion resistance.

  In Examples 11 to 18, the ratios of the boron carbide raw material and metal silicon to the alumina raw material (here, calcined alumina) were changed within the scope of the present invention. Combined with erosion.

  In Examples 19 to 22, the proportion of the three members in the fine particles was changed in the range of 20 to 60% by mass, and both had heat-resistant spalling properties and erosion resistance. From Table 4, when the heat resistant spalling property is regarded as important, it is considered that the proportion of the three members in the fine particles is preferably 50% by mass or less.

  In Comparative Example 1, all of the coarse particles are made of a silicon carbide raw material, and the fine voids can hardly be formed. Therefore, the heat resistant spalling property is inferior.

  In Comparative Example 2, the proportion of the fused alumina in the coarse particles is about 50% by mass, which is less than the lower limit (60% by mass) stipulated by the present invention. Poor polling performance.

  In Comparative Example 3, all of the medium grains are composed of electrofused alumina, and the invasion of the erodant into the inside of the structure is facilitated due to the melt damage of the medium grains, so that the erosion resistance is poor.

  Comparative Example 4 is inferior in heat-resistant spalling properties because the coarse particles are made of a silicon carbide raw material, and inferior in corrosion resistance because the medium particles are made of fused alumina.

Comparative Example 5 uses fused alumina C having a TiO ₂ content of 0.5% by mass and smaller than the lower limit (1.5% by mass) defined in the present invention as coarse particles. The thermal expansion coefficient is small, and the ability to form fine voids is poor, so that the heat-resistant spalling property is insufficient.

  In Comparative Example 6, the boron carbide raw material is not blended in the fine particles, and a solid solution cannot be formed in the matrix portion, so that the corrosion resistance is inferior.

  In Comparative Example 7, metal silicon is not blended in the fine particles, and a solid solution cannot be formed in the matrix portion, so that the erosion resistance is poor.

  In Comparative Example 8, the proportion of the three occupying the fine particles is 14.8% by mass, which is lower than the lower limit (20% by mass) defined in the present invention, so that a solid solution cannot be sufficiently formed in the matrix portion and the erosion resistance is poor.

  In Comparative Example 9, the ratio of the boron carbide raw material to the alumina raw material (calcined alumina) exceeds 50% by mass and exceeds the upper limit (40% by mass) defined in the present invention. It is inferior in heat-resistant spalling properties, probably because an excessive boron carbide raw material that does not contribute to the formation of a solid solution is vitrified.

  In Comparative Example 10, the ratio of metal silicon to the alumina raw material (calcined alumina) exceeds 71% by mass and exceeds the upper limit (60% by mass) defined in the present invention. The surplus metal silicon that does not contribute to the formation of the solid solution is vitrified, or is inferior in heat-resistant spalling property.

  As mentioned above, although the preferable example of this invention was demonstrated, this invention is not limited to this. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

Claims (4)

Fused alumina having a TiO ₂ content of 1.5% by mass or more is a coarse particle having a particle size of 1 mm or more occupying 60% by mass or more, and a particle size of 75 μm or more and less than 1 mm in which a silicon carbide material occupies 90% by mass or more. A total of three grains, an alumina raw material, a boron carbide raw material in an amount of 5 to 40% by mass with respect to the alumina raw material, and metal silicon in an amount of 5 to 60% by mass with respect to the alumina raw material And the balance is an amorphous refractory for blast furnace discharge consisting of a refractory powder composed mainly of silicon carbide material and having a particle size of less than 75 μm and an additive containing a binder. object.   The amorphous refractory for blast furnace discharge according to claim 1, wherein the proportion of the coarse particles in 100% by mass of the refractory powder is 40 to 60% by mass.   Claims wherein the fine particles are composed of the above three and silicon carbide raw materials, or are composed of at least one selected from the above three and silicon carbide raw materials, carbonaceous raw materials, silicon nitride raw materials, and titania raw materials. Item 3. An unshaped refractory for blast furnace discharge according to item 1 or 2.   The refractory refractory for blast furnace discharge according to any one of claims 1 to 3, which is used for a slag line.