JP2015189640A - Alumina-silicon carbide-carbonaceous brick - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new alumina-silicon carbide-carbonaceous brick high in durability.SOLUTION: A binder is added to a refractory raw material blend comprising: graphite in which the content of intermediate grain alumina with a grain size of 0.075 to below 1 mm is 35 to 55 mass%; coase grain alumina with a grain size of 1 to below 5 mm by 0.25 to 1.00 in a mass ratio to the intermediate grain alumina;fine grain alumina with a grain size below 0.075 mm by 0.05 to 0.30 in a mass ratio to the intermediate grain alumina; graphite in which the ratio of the intermediate grains with a grain size of 0.075 to below 1.0 mm is 50 mass% or higher by 3 to 20 mass%; silicon carbide in which the ratio of fine grains with a grain size below 0.075 mm is 50 mass% or higher by 1 to 10 mass%; a metal in which the ratio of fine grains with a grain size below 0.075 mm is 70 mass% or higher by 0.1 to 5 mass%, and in which the total content of the alumina is 60 to 95 mass%, to perform kneading, molding and heat treatment.

Description

  The present invention relates to an alumina-silicon carbide-carbonaceous brick that is suitably used for a lining material of a hot metal container used for transporting, storing, refining, etc. hot metal.

  In the iron making process, so-called hot metal pretreatment for removing Si, P, and S in the hot metal is widely performed while the hot metal is transported from the blast furnace to the converter. In addition, so-called kneading vehicle de-Si, which performs de-Si processing in a kneading vehicle as part of the hot metal pretreatment, is also widely performed.

  In recent years, particularly in Japan, it has been demanded that the content of Si, P, S, etc. in steel is extremely low with the trend toward higher grade steel. As a result, the hot metal pretreatment conditions become severe, and as a result, damage to the refractory used in the hot metal container tends to increase. Therefore, further enhancement of durability has been strongly demanded for alumina-silicon carbide-carbonaceous bricks generally used as lining materials for hot metal containers such as kneading vehicles.

  There are various causes of the damage of the alumina-silicon carbide-carbonaceous brick, or it is considered that wear due to slag is mainly considered in view of the recent severe hot metal pretreatment conditions.

  The reason for wear by slag is that the slag is penetrated into the brick structure and the alumina of the aggregate is melted. This melt damage causes the carbon bond in the structure to deteriorate due to oxidation and the structure becomes porous. It becomes more noticeable.

  Conventionally, as a technique for suppressing this melting loss, magnesia or magnesia-rich spinel is contained in the brick, and the spinel is formed by reacting with alumina during use to make the structure dense, and the penetration of slag. Techniques for preventing this are known. The use of magnesia or magnesia-rich spinel can prevent joint melting due to joint opening because the residual expansion of brick increases due to the generation of spinel. In addition, it is well known to be used for blending raw materials such as metals such as aluminum or glass powder for preventing oxidation.

For example, in Patent Document 1, as examples of using spinel and magnesia, an alumina material 30 to 90%, a carbonaceous material 3 to 30%, and an Al ₂ O ₃ —MgO-based spinel material 5 to 50% having a particle diameter of 1 mm or less. In addition, a carbon-containing refractory using a composition containing 0.1 to 5% of a vitreous material as an outer shell is disclosed. And as a result of spinel particle | grains of fine powder couple | bonding together by interposition of glassy material and a spinel bridge | crosslinking layer is comprised in the operation surface in use of a refractory material, it is supposed that corrosion resistance and oxidation resistance will improve.

  Patent Document 2 discloses an alumina carbon-based unfired brick using spinel ultrafine powder in an amount of 2% by mass to 20% by mass. It is said that the corrosion resistance and the hot strength are improved in order to re-oxidize on the surface of the surrounding alumina aggregate by the vapor phase Mg generated from the spinel ultrafine powder to produce a porous secondary spinel.

  On the other hand, as an example of densifying the structure, Patent Document 3 discloses silicon carbide / alumina brick containing 5 to 25% by weight of high-purity calcined alumina. By blending calcined alumina, formability is improved, and sintering is promoted by firing, so that alumina and silicon carbide can be closely bonded, and the porosity and breathability of the resulting brick are remarkably increased. It can be lowered.

Japanese Patent Laid-Open No. 9-25160 JP 2012-36064 A JP-A-5-105507

  However, the brick of Patent Document 1 has a wide particle size distribution range of raw material particles, for example, using a raw material of 1 mm or less in the composition, and fine particles cannot be controlled. As a result, there is a high possibility that the denseness of the tissue in use is insufficient. In addition, when there are many fine particles, the sintering proceeds excessively, so that there is a problem that the thermal shock resistance (spalling resistance) deteriorates. Furthermore, since the MgO component is contained in the brick under the de-Si processing condition in the above-described kneading vehicle, the corrosion resistance is lowered.

  Similarly, the brick of Patent Document 2 uses fused alumina having a particle size of 0.1 mm or less in the refractory raw material composition of the example, and the use of bricks is insufficient because the control of the fine particles in this raw material is insufficient. The apparent porosity after firing at 1400 ° C. for 3 hours assuming the inside is low, and the denseness of the tissue in use may be insufficient. Furthermore, since the MgO component is contained in the brick under the de-Si processing condition in the above-described kneading vehicle, the corrosion resistance is lowered.

  Further, as in Patent Document 3, when calcined alumina is used in alumina-silicon carbide-carbonaceous brick, there is a problem that the joint is easily opened because sintering progresses during use and the brick shrinks. Furthermore, since the sintering proceeds excessively, the thermal shock resistance also decreases.

  In other words, conventionally, a technique of improving oxidation resistance and corrosion resistance by adding various additives such as magnesia, spinel, or glass has been adopted, but in particular, the hot metal pretreatment has become severe in recent years. There was a limit in improving durability in cars.

  Accordingly, the problem to be solved by the present invention is to provide an alumina-silicon carbide-carbonaceous brick with high durability that has never been achieved, and more specifically, while maintaining thermal shock resistance, An object of the present invention is to provide an alumina-silicon carbide-carbonaceous brick having improved corrosion resistance and oxidation resistance as compared with the current situation and having suitable residual expansibility.

  If the present inventors can maintain the structure densely during the use of the brick, the penetration of oxygen and slag into the brick structure is suppressed, the corrosion resistance and oxidation resistance of the brick are improved, and the oxidation is also performed. It was thought that the addition of an inhibitor or the like could be minimized.

  Therefore, attention is paid to the particle size constitution of alumina that has the greatest influence on the densification of the structure hot, and alumina is coarse particles having a particle size of 1 mm or more and less than 5 mm, intermediate particles having a particle size of 0.075 mm or more and less than 1 mm, It was divided into three groups of fine particles of less than 075 mm, and the relationship among these blending ratios, apparent porosity, corrosion resistance and oxidation resistance was investigated.

  As a result, by making the blending ratio of the intermediate grains richer than the coarse grains, it becomes a dense brick that has never existed before, and it has excellent corrosion resistance and oxidation resistance, and further by controlling the blending amount of the fine grains Alumina-silicon carbide-carbonaceous brick was obtained in which the progress of excessive sintering was inhibited and the residual swelling property was adequate.

That is, according to the present invention, the following (1) to (3) alumina-silicon carbide-carbonaceous bricks are provided.
(1) Alumina-silicon carbide-carbonaceous brick formed by kneading, forming, and heat-treating by adding a binder to the refractory raw material composition,
The refractory raw material composition is
35% by mass or more and 55% by mass or less of intermediate alumina having a particle size of 0.075 mm or more and less than 1 mm,
Coarse-grained alumina having a particle size of 1 mm or more and less than 5 mm is 0.25 or more and 1.00 or less in a mass ratio with respect to the intermediate-grain alumina.
Fine alumina having a particle size of less than 0.075 mm is 0.05 to 0.30 in terms of mass ratio with respect to the intermediate alumina.
3% by mass or more and 20% by mass or less of graphite having 50% by mass or more of intermediate grains having a particle size of 0.075 mm or more and less than 1.0 mm,
1% by mass or more and 10% by mass or less of silicon carbide in which fine particles having a particle size of less than 0.075 mm are 50% by mass or more,
Containing 0.1% by mass or more and 5% by mass or less of a metal having 70% by mass or more of fine particles having a particle size of less than 0.075 mm;
And the alumina-silicon carbide-carbonaceous brick whose total amount of the alumina in the said refractory raw material mixture is 60 to 95 mass%.
(2) The alumina-silicon carbide-carbonaceous brick according to (1), wherein the refractory raw material composition further contains 5% by mass or less of glass having a particle size of 0.075 mm or less of 70% by mass or more. .
(3) (1) or (2), wherein the refractory raw material composition further contains 10% by mass or less of magnesia and / or spinel in which particles having a particle size of 0.075 mm or more and less than 5 mm are 70% by mass or more. The alumina-silicon carbide-carbonaceous brick described.

  Hereinafter, the present invention will be described in detail.

  Alumina is an important raw material that affects corrosion resistance in alumina-silicon carbide-carbonaceous brick, and is contained in an amount of 60% by mass or more and 95% by mass or less in the proportion of the refractory raw material mixture. If the alumina is less than 60% by mass, the corrosion resistance is insufficient, and if it exceeds 95% by mass, the graphite is insufficient, so that the thermal shock resistance is insufficient.

  At a use temperature in a kneading vehicle, which is a typical application of alumina-silicon carbide-carbon brick, the structure changes due to sintering of alumina or reaction with other raw materials. For this reason, control of the particle size composition of alumina is extremely important. Here, according to the experience of the present inventors in the analysis of the past used bricks and the like, alumina reacts with other alumina and other raw materials having a small particle size with high activity on the fine particle side with a particle size of 0.075 mm as a boundary. It is easy to change the organization. Therefore, in the present invention, the boundary value between the alumina intermediate grains and the fine grains is set to 0.075 mm. Similarly, from the experience of the present inventors, when alumina has a particle diameter of 1 mm or more, the reactivity tends to be clearly lower than that of alumina of less than 1 mm. Was 1 mm. That is, in the present invention, the particle size of less than 0.075 mm is defined as fine particles, the particle size of 0.075 mm or more and less than 1 mm is defined as intermediate particles, and the particle size of 1 mm or more and less than 5 mm is defined as coarse particles.

  The particle size constitution of alumina in the present invention will be described. First, the proportion of intermediate particles having a particle size of 0.075 mm or more and less than 1 mm is 35% by mass or more and 55% by mass or less as a proportion of the refractory raw material composition. If the intermediate grain is less than 35% by mass, the apparent porosity of the brick increases and the corrosion resistance decreases. If the intermediate grain exceeds 55% by mass, the filling property at the time of molding deteriorates, the apparent porosity increases, and the corrosion resistance decreases. The proportion of the intermediate grains of alumina is preferably 43% by mass or more and 55% by mass or less.

  Coarse particles having a particle diameter of 1 mm or more and less than 5 mm have a higher apparent porosity when they are larger than the intermediate particles, so that a small amount is contained with respect to the content ratio of the intermediate particles. Specifically, the mass ratio (coarse grains / intermediate grains) is 0.25 or more and 1.00 or less with respect to the intermediate grains. If it is less than 0.25, the filling property at the time of shaping | molding will worsen, and apparent porosity will rise.

  The fine particles having a particle size of less than 0.075 mm have a mass ratio (fine particles / intermediate particles) to 0.05 to 0.30 with respect to the intermediate particles. If it is less than 0.05, the corrosion resistance becomes insufficient, and if it exceeds 0.30, the apparent porosity becomes high, the corrosion resistance becomes insufficient, the residual expansion becomes negative or small, and the thermal shock resistance becomes worse.

  In this way, the grain size composition of alumina is divided into three groups of coarse grains, intermediate grains, and fine grains with a boundary value of 1 mm and 0.075 mm, and the grain size composition is always rich in intermediate grains, so that the structure is dense. At the same time, the residual expansibility and sufficient thermal shock resistance can be satisfied.

  Next, raw materials other than alumina used in the present invention will be described.

  Graphite is mainly used for imparting thermal shock resistance and corrosion resistance, and is used in an amount of 3% by mass to 20% by mass. As the particle size constitution, the larger the particle size, the smaller the residual expansion coefficient after the heat treatment and the apparent porosity after the heat treatment decreases, so that the particles containing 50% by mass or more of intermediate particles of 0.075 mm or more and less than 1.0 mm are contained. use.

Silicon carbide is used as an antioxidant and is used in an amount of 1 to 10% by mass. If it is less than 1% by mass, the oxidation resistance is insufficient, and if it exceeds 10% by mass, the corrosion resistance is lowered due to the influence of SiO ₂ produced on the brick in use. It is preferable that the usage-amount of silicon carbide is 3 mass% or more and 8 mass% or less. On the other hand, as the particle size constitution of silicon carbide, one containing 50% by mass or more of fine particles having a particle size of less than 0.075 mm is used in order to obtain sufficient oxidation resistance.

  Metal is also used as an antioxidant and is used in an amount of 0.1 to 5% by mass. Examples of the metal include aluminum (Al), silicon (Si), magnesium (Mg), and alloys thereof. One or a combination of two or more of these can be used, but from the viewpoint of corrosion resistance and oxidation resistance. Aluminum is most preferred. When the amount of the metal used exceeds 5% by mass, the secondary bond develops excessively, so that the thermal shock resistance decreases, and the generated metal oxide reduces the corrosion resistance. The amount of metal used is preferably 0.1% by mass or more and 3.0% by mass or less. As the particle size constitution of the metal, one containing 70% by mass or more of fine particles having a particle size of less than 0.075 mm is used in order to obtain sufficient oxidation resistance.

  Glass is used as necessary as an antioxidant. For example, borosilicate glass or phosphoric acid glass can be used. However, if the amount of glass used exceeds 5% by mass, the corrosion resistance is greatly reduced, so it is used at 5% by mass or less, preferably at 3% by mass or less. As the particle size constitution of the glass, one containing 70% by mass or more of fine particles having a particle size of less than 0.075 mm is used in order to obtain sufficient oxidation resistance.

  Magnesia and / or spinel can be used when it is desired to further increase the residual swellability and oxidation resistance. The amount used is preferably 10% by mass or less. If the amount exceeds 10% by mass, the corrosion resistance is remarkably lowered, and the residual expansion rate becomes too large, so that cracks due to the bricks are generated, and further, the bricks are peeled off due to the reduced thermal shock resistance. . As the particle size constitution of magnesia and / or spinel, if a large amount of coarse particles is used, the residual expansion rate can be increased. On the other hand, when a large amount of fine particles are used, the oxidation resistance can be remarkably improved by the reaction with the above-mentioned alumina, but at the same time, the corrosion resistance is lowered. The decrease is remarkable. For this reason, magnesia and / or spinel having a particle size of 70% by mass or more of intermediate particles and coarse particles having a particle size of 0.075 mm or more and less than 5 mm is used.

In the present invention, magnesia and / or spinel contributes to the improvement of oxidation resistance when used in combination with glass. The mechanism is considered as follows. In the alumina-silicon carbide-carbonaceous brick of the present invention, silicon carbide (SiC) reacts with oxygen at a high temperature to generate SiO and SiO _2, and at this time, in the presence of alumina (Al ₂ O ₃ ), the composite The compound mullite (3Al ₂ O ₃ · 2SiO ₂ ) is produced. Further, glass generates a silica-based liquid phase at a high temperature, and generates a 3Al ₂ O ₃ .2SiO ₂ liquid phase in the presence of Al ₂ O ₃ . Furthermore, when magnesia (MgO) and / or spinel (MgO.Al ₂ O ₃ ) coexist in the production stage of these composite compounds, the liquid phase becomes a ternary system of SiO ₂ —Al ₂ O ₃ —MgO, The melting point is lower than that of the conventional one-component or two-component system, and the viscosity decreases accordingly. This ternary liquid phase acts as a low-viscosity oxide film on the lower temperature side than one-component and two-component systems, so it suppresses the reduction in oxidation resistance of carbon-containing refractories or improves oxidation resistance Let

  Since the alumina-silicon carbide-carbonaceous brick of the present invention has a very dense structure even during use, the residual expandability and oxidation resistance are sufficient without using a large amount of magnesia or spinel as in the past. It is obtained and has excellent corrosion resistance. It also has excellent thermal shock resistance. Furthermore, residual expansibility and oxidation resistance can be further improved by using an appropriate amount of magnesia or spinel. For this reason, sufficient durability can be obtained even in a kneading vehicle having severe hot metal pretreatment conditions.

The alumina used in the present invention is a refractory raw material containing Al ₂ O ₃ in an amount of 80% by mass or more, preferably 90% by mass or more, and alumina materials generally used for refractories can be used. For example, one or more of electrofused alumina, sintered alumina, bauxite, and van earth shale can be used. Although calcined alumina can be used, calcined alumina having a particle size of less than 0.075 mm is preferably used at 3% by mass or less from the viewpoint of suppressing oversintering.

  As the graphite, ordinary scaly graphite can be used, but expanded graphite, artificial graphite, quiche graphite, or the like may be used instead of or in combination with this. Although the composition is not particularly limited, it is better to use graphite having high C purity in order to obtain higher corrosion resistance, and the C purity is preferably 85% or more, more preferably 98% or more.

  As the silicon carbide, silicon carbide raw materials used for ordinary refractories and having a SiC content of 80% by mass or more can be used.

  As the metal, one or more of aluminum, magnesium, silicon, and alloys thereof can be used.

  As the glass, borosilicate glass, phosphate glass, silicate glass, lead-containing glass, lithium-containing glass and the like can be used.

As magnesia, electrofused magnesia, sintered magnesia or the like can be used, and as spinel, a refractory material mainly composed of Al ₂ O ₃ and MgO, MgO content is 5 mass% or more, preferably MgO. A content of 20% by mass or more can be used.

  As raw materials other than the above, one or more of mullite, carbon black, anthracite, coke powder, pitch, silicon nitride, boron carbide and the like can be used if they are 5% by mass or less.

  The alumina-silicon carbide-carbonaceous brick of the present invention can be produced by a general production method in which a binder is added to a refractory raw material composition, kneaded, molded, and heat-treated at about 150 to 500 ° C. In addition, a phenol resin, a furan resin, etc. can be used as a binder.

  Raw materials were weighed at the ratios shown in Tables 1 and 2, phenol resin was added as a binder and kneaded. After pressure molding at 150 MPa or more, heat treatment was performed at 250 ° C. From this, a sample for measuring physical properties was cut out to measure the apparent porosity and residual expansion rate, and the corrosion resistance, oxidation resistance and thermal shock resistance were evaluated.

  In measuring the apparent porosity, a sample having a shape of 60 × 60 × 60 mm was used. The apparent porosity was measured after firing in a reducing atmosphere at 1400 ° C. for 3 hours in order to evaluate the denseness of the brick during use. The reason for setting the firing temperature at 1400 ° C. is that when the temperature is less than 1400 ° C., the reaction inside the alumina-silicon carbide-carbonaceous brick cannot be completed, and the heat load is not sufficient, so that it is not suitable for evaluation of denseness. Sintering proceeds at a temperature exceeding 1, and it becomes difficult to separate and evaluate the effect of sintering as an evaluation of denseness, and the load on the furnace for firing is large, making it unpreferable as a steady measurement method. It is. If the firing time is less than 3 hours, the reaction inside the alumina-silicon carbide-carbonaceous brick cannot be completed, which is not suitable. Furthermore, if firing is performed for a longer time, sintering proceeds and it is difficult to separate and evaluate the effect. In this example, the apparent porosity of a sample after firing in a reducing atmosphere at 1400 ° C. for 3 hours was measured according to the Archimedes method (JIS R 2205) using white kerosene as a liquid medium.

  In the measurement of the residual expansion coefficient, a 20 × 20 × 80 mm sample was used, and the residual expansion coefficient was calculated by measuring the dimensions of the sample before and after the heat treatment in a reducing atmosphere at 1400 ° C. for 3 hours.

Corrosion resistance was evaluated by a rotational erosion test. In the rotary erosion test, a test brick was lined on the inner surface of a drum having a horizontal rotation axis, slag was added, and the brick surface was eroded by heating. The heating source was an oxygen-propane burner, the test temperature was 1500 ° C., the slag composition was CaO / SiO ₂ = 1.0, FeO = 1.5 mass%, and slag discharge and charging were repeated 10 times every 30 minutes. . After the test was completed, the size of the maximum melted portion of each brick was measured to calculate the erosion amount, and the erosion amount of “Comparative Example 1” shown in Table 1 was expressed as a corrosion resistance index with 100 (corrosion resistance index = 100 × Erosion amount of Comparative Example 1 (cm ³ ) / Erosion amount of each example (cm ³ )). The higher the corrosion resistance index, the better the corrosion resistance.

  In the evaluation of oxidation resistance, the sample after drying was cut out to φ50 × 50 mm and fired in an electric furnace at 1400 ° C. for 15 hours in an air atmosphere. The center in the height direction of the sample after firing was cut, the thickness of the portion where the carbon component was decarburized and discolored was measured in four directions, and the average value of these values was taken as the decarburized layer thickness. And it displayed with the oxidation resistance index | exponent which makes the thickness of the decarburization layer of "Comparative example 1" of Table 1 100 (oxidation resistance index = 100x decarburization layer thickness (mm) of comparative example 1 / each example Decarburization layer thickness (mm)). The larger the numerical value of this oxidation resistance index, the better the oxidation resistance.

  In the evaluation of thermal shock resistance, a 40 × 40 × 190 mm sample was reduced and fired at 1400 ° C. for 3 hours, immersed in 1500 ° C. hot metal for 90 seconds, and then subjected to 30-second water-cooled thermal shock 10 times. And observed the state of cracks and peeling. In the table, ◎ indicates that there was no crack or peeling after the test, ○ indicates that a slight crack or peeling occurred, △ indicates that a moderate crack or peeling occurred, × indicates that a large crack or crack occurred. Is.

  Hereinafter, the evaluation results of each example will be described with reference to Table 1 and Table 2.

  Examples 1 to 3 have different proportions of alumina intermediate grains, but are within the scope of the present invention. Despite the fact that glass, magnesia, or spinel is not used, the structure is dense due to the low apparent porosity after firing, and is excellent in corrosion resistance and oxidation resistance. Moreover, it has sufficient residual expansibility.

  On the other hand, in Comparative Example 1, since the alumina intermediate grains are 30% by mass and less than the lower limit of 35% by mass of the present invention, the apparent porosity after firing becomes a rough structure, and the corrosion resistance and oxidation resistance are increased. Is insufficient. Moreover, since the intermediate grain of alumina exceeds 60 mass% and the upper limit of 55 mass% of the present invention in Comparative Example 2, the apparent porosity after firing is high, and the corrosion resistance and oxidation resistance are reduced. Furthermore, Comparative Example 20 is an example in which glass and magnesia were added, but the intermediate grain of alumina was 30% by mass and below the lower limit of the present invention, so that the corrosion resistance was considerably inferior compared with Examples 1-3. It has become.

  Examples 4 to 6 have different proportions of alumina fine particles, but are within the scope of the present invention, and since the apparent porosity after firing is low, the structure is dense, and corrosion resistance and oxidation resistance are improved. Are better. Moreover, it has sufficient residual expansibility.

  On the other hand, since the ratio of the fine particles of alumina (fine particles / intermediate particles) is 0.00, which is lower than the lower limit value 0.05 of the present invention, Comparative Example 3 has insufficient corrosion resistance. In Comparative Example 4, the fine powder / intermediate grain is 0.35, which exceeds the upper limit of 0.30 of the present invention, so that the apparent porosity after firing becomes high, the corrosion resistance and oxidation resistance become insufficient, and the residual expansion is reduced. It is getting smaller. Furthermore, the thermal shock resistance is also reduced.

  Examples 7 to 9 have different proportions of alumina coarse particles, but they are within the scope of the present invention, and the structure is dense due to the low apparent porosity after firing, corrosion resistance and oxidation resistance. Is excellent. Moreover, it has sufficient residual expansibility.

  On the other hand, since the ratio of coarse particles of alumina (coarse particles / intermediate particles) is 0.1, which is lower than the lower limit value 0.25 of the present invention, Comparative Example 5 has a high apparent porosity after firing. Corrosion resistance is reduced. In Comparative Example 6, since the coarse / intermediate grain is 1.25, which exceeds the upper limit of 1.00 of the present invention, the apparent porosity after firing becomes high, and the corrosion resistance and oxidation resistance are lowered.

  Examples 10 to 12 have different proportions of graphite, but within the scope of the present invention, the apparent porosity after firing is low, the structure is dense, and excellent in corrosion resistance and oxidation resistance. ing. Moreover, it has sufficient residual expansibility.

  On the other hand, in Comparative Example 7, the amount of graphite is 0% by mass, which is lower than the lower limit of 3% by mass of the present invention. Therefore, the apparent porosity after firing becomes high and the corrosion resistance is lowered. In Comparative Example 8, the amount of graphite is 23% by mass, which exceeds the upper limit of 20% of the present invention, so that the apparent porosity after firing becomes high and the corrosion resistance and oxidation resistance are lowered.

  In Example 13, 1% by mass of borosilicate glass was added, but the oxidation resistance was improved.

  Examples 14 to 19 are examples in which the addition amount of aluminum, silicon, borosilicate glass, phosphate glass, magnesia, and spinel was changed, but all are within the scope of the present invention, and the apparent porosity after firing is Since it is low, the structure is dense, and it has excellent corrosion resistance and oxidation resistance. Moreover, it has sufficient residual expansibility.

Claims (3)

Alumina-silicon carbide-carbonaceous brick formed by adding a binder to a refractory raw material composition and kneading, molding, and heat-treating,
The refractory raw material composition is
35% by mass or more and 55% by mass or less of intermediate alumina having a particle size of 0.075 mm or more and less than 1 mm,
Coarse-grained alumina having a particle size of 1 mm or more and less than 5 mm is 0.25 or more and 1.00 or less in a mass ratio with respect to the intermediate-grain alumina.
Fine alumina having a particle size of less than 0.075 mm is 0.05 to 0.30 in terms of mass ratio with respect to the intermediate alumina.
3% by mass or more and 20% by mass or less of graphite having 50% by mass or more of intermediate grains having a particle size of 0.075 mm or more and less than 1.0 mm,
1% by mass or more and 10% by mass or less of silicon carbide in which fine particles having a particle size of less than 0.075 mm are 50% by mass or more,
Containing 0.1% by mass or more and 5% by mass or less of a metal having 70% by mass or more of fine particles having a particle size of less than 0.075 mm;
And the alumina-silicon carbide-carbonaceous brick whose total amount of the alumina in the said refractory raw material mixture is 60 to 95 mass%.   The alumina-silicon carbide-carbonaceous brick according to claim 1, wherein the refractory raw material composition further contains 5% by mass or less of glass having a particle size of 0.075 mm or less of 70% by mass or more.   The alumina-carbonization according to claim 1 or 2, wherein the refractory raw material composition further contains 10% by mass or less of magnesia and / or spinel in which particles having a particle size of 0.075 mm or more and less than 5 mm are 70% by mass or more. Silicon-carbon brick.