JP6354807B2 - Cast refractories for blast furnace main slag line - Google Patents

Description

  The present invention relates to a cast refractory material that can be used at a location in contact with slag, such as a refractory material for a blast furnace main slag line.

  The blast furnace main shaft is a route for carrying the hot metal and molten slag derived from the blast furnace outlet to the next process. The blast furnace iron also has a function of separating hot metal and molten slag by the difference in specific gravity. It is known that the wear of the blast furnace main body occurs locally at the interface between the air and the molten slag (slag line) and at the interface between the molten slag and the molten metal (metal line). Since the wear mechanism is different between the slag line and the metal line, a refractory material of a material corresponding to the wear mechanism is separately adopted for the slag line and the metal line.

Generally, an alumina-silicon carbide-carbonaceous cast refractory is used for the slag line. For example, Patent Document 1 uses a silicon carbide aggregate having a SiC content of 70 wt% or more, a porosity of 10% or less, a filling bulk specific gravity of 1.25 or more for coarse grains, and 1.60 or more for medium grains. , Dispersed in a composition containing 70 to 95 wt% silicon carbide, 1 to 7 wt% carbonaceous raw material, 3 to 20 wt% alumina fine powder, 0.5 to 5 wt% silica fine powder, and 0.8 to 5 wt% boron carbide as appropriate A blast furnace pouring refractory material characterized by adding an agent and a binder is disclosed. Further, a spinel-alumina-silicon carbide-carbonaceous cast refractory is adopted for the metal line. For example, Patent Document 2 includes 5 to 25% silicon carbide, 1 to 5% carbon, 5 to 15% alumina ultrafine powder having an average particle size of 5 μm or less, 0.5 to 7% alumina cement, and the balance. A casting material for blast furnace fired made of a composition mainly composed of MgO—Al ₂ O ₃ spinel is disclosed.

  Conventionally, cast refractory materials for blast furnace main slag lines have been required to have improved corrosion resistance against blast furnace slag. The composition of the blast furnace slag is designed to dissolve the oxide so that no oxide-based solids remain in the blast furnace, and the oxide-based refractory aggregate is easier than the slag composition in the slag. It will dissolve. Therefore, slag line cast refractories have been made of materials mainly composed of non-oxides such as silicon carbide and carbons, eliminating oxides as much as possible. However, non-oxides have the disadvantage of oxidizing at high temperatures, which leads to a reduction in corrosion resistance.

  In order to solve this oxidation problem, various improvements have been made to the cast refractory for the blast furnace main slag line. For example, Patent Document 3 discloses a compound containing 2 to 92% by weight of silicon carbide and 2 to 7% by weight of a carbon raw material, or 2 to 7% by weight of a carbon raw material, cobalt oxide, cobalt salt, and metallic cobalt. There is disclosed a corrosion-resistant and oxidation-resistant amorphous refractory characterized in that at least one powder is added in an amount of 0.01 to 0.5% by weight in terms of metallic cobalt. In addition, the paragraph [0011] of Patent Document 3 states that “as the carbonaceous raw material, petroleum pitch, coal pitch, mesophase carbon, coke, carbon black, earthy graphite powder, scaly graphite, artificial graphite, or two or more kinds of artificial graphite. In the examples, pitch, mesophase carbon and carbon black are used as refractories for the blast furnace main metal zone. According to Patent Document 3, by adding a very small amount of cobalt oxide, cobalt salt, and metal cobalt powder, it is possible to form a glass layer to prevent oxidation and improve corrosion resistance.

  On the other hand, the cast refractory for the blast furnace main slag line has a problem of explosion. The cast refractory constructed by adding a predetermined amount of water is used after being heated and dried by a gas burner or the like. Since the construction water becomes water vapor during this heat drying, the construction body may collapse due to the pressure of the water vapor. This phenomenon is called an explosion phenomenon. In particular, the blast furnace main refractory is a large construction body and the explosion phenomenon is likely to occur due to the short drying period, etc., and the explosion resistance is one of the important characteristics of the cast refractory for the blast furnace main slag line. One.

For example, in Patent Document 4, metal silicon powder 1 to 3 wt%, boron carbide powder 0.5 to 3.0 wt%, and high melting point pitch 1 to 3 wt% are added to a base material containing silicon carbide 70 to 90 wt%. A pouring material for pouring is characterized by being formed. According to Patent Document 4, boron carbide powder prevents oxidation of silicon carbide by oxidation prior to silicon carbide, and β-SiC whiskers are formed, thereby improving the corrosion resistance of the pouring material for pouring. .
Further, Patent Document 5 discloses a refractory composition containing a carbon black raw material having an ash content of 0.5% by weight or less and a pitch raw material having a fixed carbon content of 75 to 95% by weight, and the carbon black A water-based amorphous refractory is disclosed in which the weight ratio of the content of the raw material and the pitch raw material is 1: 0.1 to 1: 0.9. In addition, the example of Patent Document 5 discloses a material in which silicon carbide or alumina is used as a base material and a specific carbon black and pitch are blended in a specific quantity ratio, and the specific carbon black and pitch are specified. By using it in a quantitative ratio, it is said that it imparts denseness and thermal stress absorption and improves spalling resistance and corrosion resistance.
Further, Patent Document 6 contains 1 to 10% by weight of ultrafine silicon carbide having an average particle size of 1 μm or less, and the remainder is a refractory material; 1 to 10% by weight of ultrafine silicon carbide having an average particle size of 1 μm or less, 3 to 12% by weight of the total amount of silicon carbide of 10 μm or less, and the rest as an refractory raw material for blast furnace blast furnaces; As the remaining refractory material, 6-14% by weight of easily sintered alumina, 20-50% by weight of spinel, 40-85% by weight of silicon carbide, 1-4% by weight of carbon material, less than 4% by weight of silica fume, 0% of metallic silicon .5 to 3.0% by weight, alumina cement 0.5 to 3.0% by weight, and in addition, an irregular refractory for a blast furnace fired as a dispersant and a curing adjusting material is disclosed. According to Patent Document 6, the addition of ultrafine powder having an average particle size of 1 μm or less increases the silicon carbide content ratio in the fine powder portion, thereby improving the corrosion resistance.

Japanese Patent Laid-Open No. 3-164479 JP-A-5-339065 JP-A-9-278540 JP-A-5-70250 JP 2002-137970 A JP 2003-137664 A

  However, non-oxides such as silicon carbide and carbons used in blast furnace pouring refractories as described in Patent Document 1 have the disadvantage of oxidizing at high temperatures. This drawback leads to a decrease in corrosion resistance. In addition, in the corrosion resistance and oxidation resistance amorphous refractories of Patent Document 3, examples in which carbon black, pitch, and mesophase pitch are used in combination as refractories for metal zones are shown. Since slag corrosion resistance is largely lacking, it cannot be used for refractories for blast furnace main slag lines, and it cannot prevent oxidation for a long period of time as refractories from the blast furnace are actually used. From the viewpoint of corrosion resistance, the formation of the glass layer is not preferable. Further, Patent Documents 4, 5 and 6 disclose examples in which pitch and carbon black are used in combination, but these materials are inferior in explosion resistance.

  Therefore, the object of the present invention can exhibit an antioxidant effect over a longer period of time compared to the prior art, and can sufficiently exhibit the corrosion resistance function of non-oxides such as silicon carbide and carbon. An object of the present invention is to provide a cast refractory for a blast furnace main slag line that does not impair explosion resistance.

The present inventors diligently studied why the durability of the blast furnace main slag line refractory cannot always be improved by the above-mentioned patent documents. The blast furnace main slag line refractory is generally operated by adding the cast refractory, and the constructed material has been used for about one year. The blast furnace main slag line refractory mainly contains silicon carbide, alumina and carbon as described above. Such a refractory reacts with oxygen gas in the atmosphere during use, carbon is scattered and disappears as CO gas according to formula (1), and then silicon carbide is SiO ₂ and SiO ₂ according to formula (2). Become.
C + 1 / 2O ₂ → CO (1)
SiC + O ₂ → SiO ₂ + C (2)
Accordingly, the porosity of the blast furnace main slag line refractory increases the porosity due to decarburization, and the corrosion resistance of the formed SiO ₂ is inferior, so that the corrosion resistance after oxidation becomes inferior. For this reason, for example, Patent Document 3 and Patent Document 4 aim to suppress oxidation by air.
However, when a sample of the blast furnace main slag line refractory after use is observed in detail, the oxidation of SiC occurs even in the condition where the oxidation of C in the vicinity of the working surface shown in the equation (1) such as the inside of the working surface does not occur. I understand that is going on. The cause is considered as follows. That is, due to the oxidation of C in the vicinity of the working surface, the atmosphere in the pores of the blast furnace main slag line refractory becomes an atmosphere containing CO. Under this condition, C inside the working surface is not oxidized and lost. However, silicon carbide is oxidized as shown in Formula (3).
SiC + 2CO → SiO ₂ + 3C (3)
That is, it was found that SiC is oxidized not only in the atmosphere O ₂ but also in a CO gas atmosphere as in the reaction of the formula (2). That is, the oxidation of SiC occurs inside the blast furnace main slag line refractory, that is, the inside of the working surface, and SiO ₂ is generated, resulting in a decrease in durability. Here, with conventional antioxidants such as metallic silicon, metallic aluminum, cobalt, and boron carbide, a short-term antioxidant effect can be expected, but the actual period of use of the actual blast furnace slag line refractory Was not enough.

Based on the above considerations, the present inventors have intensively studied. As a result, in order to maintain the oxidation resistance of the blast furnace main slag line refractory for a long period of time, the pitch is used for the cast refractory for the blast furnace main slag line. It turns out to be essential. The mechanism which can suppress the oxidation of silicon carbide by CO gas by mix | blending a pitch with the cast refractory for a blast furnace main slag line can be estimated as follows. That is, when silicon carbide is oxidized by the formula (3), silicon carbide is damaged in a comb shape and carbon remains, and the Si component does not remain remarkably in the vicinity of the silicon carbide grains. This is thought to be because SiO (g: gas) that is easily diffused was generated and the Si component was diffused. Therefore, it is considered that by covering the periphery of the silicon carbide particles with a film having a low gas permeability, it is possible to prevent contact between CO and silicon carbide particles and to suppress volatilization of the generated SiO (g). .
However, for the addition of pitch to significantly inhibit the breathability of the blast furnace main trough slag line refractory, construction body problem resistant explosion is poor contact only that the drying step when applying a refractory pouring occurs did.
Therefore, as a result of investigating methods for improving deterioration of explosion resistance while maintaining oxidation resistance over a long period of time, if the mesophase pitch and pitch are used together, sufficient oxidation resistance is maintained without impairing explosion resistance. The knowledge that it was possible to impart sex was obtained.
The present invention is based on the above findings.

  That is, the present invention is a silicon carbide-alumina-carbon blast furnace main slag line cast refractory, in which silicon carbide raw material is 50 to 90 mass%, alumina raw material is 1-41 mass%, carbon black, pitch and The carbonaceous raw material composed of mesophase pitch is in the range of 0.9 to 21% by mass, carbon black is 0.3 to 9% by mass, pitch is 0.3 to 5% by mass, and mesophase pitch is 0.3 to It is a cast refractory for a blast furnace main slag line characterized by being in the range of 7% by mass.

  According to the present invention, oxidation of silicon carbide by CO gas during use of the blast furnace main can be prevented over a long period of time, and the corrosion resistance function of non-oxides such as silicon carbide and carbon can be sufficiently exhibited. The cast refractory for a blast furnace main slag line material that does not impair the explosion resistance in the drying process after the cast refractory is constructed can be provided.

  The cast refractory for the blast furnace main slag line of the present invention is a silicon carbide-alumina-carbon cast refractory, and the substrate is composed of a silicon carbide raw material, an alumina raw material, and a carbonaceous raw material. The compounding ratio of the silicon carbide raw material is 50 to 90% by mass, preferably 60 to 80% by mass. If the blending ratio of the silicon carbide raw material is less than 50% by mass, the corrosion resistance is poor, which is not preferable. Moreover, when the compounding ratio of a silicon carbide raw material exceeds 90 mass%, fluidity | liquidity is inferior, and when constructing | casting a cast refractory material, a lot of water | moisture contents are needed, and it is unpreferable since it is inferior to corrosion resistance. In addition, it is preferable that the SiC purity of a silicon carbide raw material is 85 mass% or more from a viewpoint of corrosion resistance, More preferably, it is 90 mass% or more.

  Next, the mixing ratio of the alumina raw material is in the range of 1 to 41% by mass, preferably 14 to 37% by mass. When the content of the alumina raw material is less than 1% by mass, the fluidity is inferior, and a large amount of water is required when constructing the cast refractory, which is not preferable because the corrosion resistance is inferior. Moreover, when the mixture ratio of an alumina raw material exceeds 41 mass%, since it is inferior to corrosion resistance, it is unpreferable. Here, as the alumina raw material, calcined alumina, electrofused alumina, sintered alumina, bauxite, porphyry shale, or the like can be used, and two or more of these alumina raw materials can be used in combination. In addition, it is preferable that the purity of an alumina raw material is 80 mass% or more from a corrosion-resistant viewpoint, More preferably, it is 90 mass% or more.

The blending ratio of the carbonaceous raw material is in the range of 0.9 to 21% by mass, preferably 1.5 to 16% by mass. In addition, the mixture ratio of a carbonaceous raw material is the total amount of each component mentioned later. Here, if the blending ratio of the carbonaceous raw material is less than 0.9% by mass, the corrosion resistance is inferior. Moreover, when the mixing ratio of the carbonaceous raw material exceeds 21% by mass, the fluidity is inferior, and a large amount of moisture is required when constructing the cast refractory, which is not preferable because the corrosion resistance is inferior.
Carbon black, pitch and mesophase pitch are used in combination as the carbonaceous raw material. Here, the blending ratio of carbon black is 0.3 to 9% by mass, preferably 0.5 to 7% by mass. If the blending ratio of carbon black is less than 0.3% by mass, the corrosion resistance is poor, which is not preferable. On the other hand, when the blending ratio of carbon black exceeds 9% by mass, the fluidity is inferior, and a large amount of water is required when constructing the cast refractory, which is not preferable because the corrosion resistance is inferior.

The carbon black that can be used is not particularly limited, and any carbon black produced by a pyrolysis method or an incomplete combustion method can be used. Also, but are not particle size or DBP (dibutyl phthalate) absorption amount of carbon black is also particularly limited, preferably, and a DBP absorption of the average particle diameter is 15nm or more is as follows 150 cm ^3/100 g.

  Next, the blending ratio of pitch is 0.3 to 5% by mass, preferably 0.5 to 4% by mass. If the blending ratio of the pitch is less than 0.3% by mass, the oxidation resistance is poor, which is not preferable. On the other hand, if the blending ratio of the pitch exceeds 5% by mass, the explosion resistance is poor.

  As the pitch, those having a softening point of 350 ° C. or lower can be used, and examples thereof include coal tar pitch and petroleum pitch. The particle size of the pitch is not particularly limited. Preferably, a coal tar pitch having a softening point of 200 ° C. or lower can be used.

  Furthermore, the blending ratio of mesophase pitch is 0.3 to 7% by mass, preferably 0.5 to 7% by mass. When the blending ratio of the mesophase pitch is less than 0.3% by mass, the explosion resistance is poor, which is not preferable. On the other hand, when the blending ratio of mesophase pitch exceeds 7% by mass, the fluidity is inferior, and a large amount of water is required when constructing the cast refractory, which is not preferable because of poor corrosion resistance.

  As the mesophase pitch, one having a softening point higher than 350 ° C. and a mesophase ratio of 60% by mass or more is used. From the viewpoint of corrosion resistance, the mesophase pitch fixed carbon ratio is preferably 80% by mass or more, and more preferably 85% by mass or more.

  Here, in the cast refractory for the blast furnace main slag line of the present invention, by using together carbon black, pitch and mesophase pitch as the carbonaceous raw material, the acid resistance of the construction body obtained from the cast refractory for the blast furnace main slag line The explosion resistance in the construction drying process can be improved while maintaining the chemical conversion property for a long period of time.

In the cast refractory for the blast furnace main slag line of the present invention, a curing material, a dispersing agent, a curing time adjusting agent, an explosion preventing agent, an antioxidant and the like can be used as additives. The mixing ratio of the additive is 1 to 6% by mass, preferably 2 to 5% by mass, based on 100% by mass of the base material composed of the silicon carbide raw material, the alumina raw material and the carbonaceous raw material. .
As the curing material, for example, a normal temperature curing material such as alumina cement or a clay raw material, or a known thermosetting binder such as silicate or phosphate can be used.
Dispersants include, for example, materials commonly used for amorphous refractories such as alkali metal phosphates, alkali metal carboxylates, alkali metal humates, naphthalene sulfonic acid formalin condensate salts, sodium polycarboxylates, etc. Alternatively, a substance that can obtain the same effect as these can be used. A plurality of types of dispersants can be used in combination.
The curing time adjusting agent includes a curing accelerator and a curing retarder. For example, slaked lime, calcium chloride, sodium aluminate, lithium carbonate, or the like can be used as the hardening accelerator, and a plurality of kinds of hardening accelerators can be used in combination. For example, boric acid, oxalic acid, citric acid, gluconic acid, sodium carbonate, sugar or the like can be used as the curing retarder, and a plurality of curing retarders can be used in combination.
As the explosion preventing agent, for example, metallic aluminum, aluminum lactate, organic fiber, or the like can be used, and a plurality of types of explosion preventing agents can be used in combination. Further, for example, boron carbide can be used as the antioxidant.

The mixing method of the raw materials as described above is not particularly limited, and any known mixing method can be employed. For example, as an apparatus for mixing, for example, an omni mixer or the like can be used. Further, when mixing, additives such as a curing agent, a dispersing agent, a curing time adjusting agent, an anti-explosion agent, and an antioxidant can be made into a separate bag without being mixed into the base material.
The kneading method of the raw material is not particularly limited, and any known kneading method can be adopted. For example, a vortex mixer, a mortar mixer, or the like can be used as an apparatus for kneading. The kneading water is not particularly limited. Household water, industrial water, etc. can be used. Further, it may be a liquid containing a binder such as silica sol.

The cast refractories for blast furnace main slag lines of the present invention and comparative products will be described with the blending ratios described in Tables 1 to 4 below, but it is understood that the present invention is not limited to the following examples. I want to be.
In Tables 1-4, the characteristics of the cast refractories prepared by blending and kneading the raw materials at the blending ratios shown in the tables were evaluated. The kneading was carried out with a mixer with the amount of kneading water adjusted so that the tap flow value by a test method according to JIS R 2521 was 135 to 145.
The purity of silicon carbide was 97% by mass. The purity of alumina was 99% by mass. Carbon black has been prepared pyrogenically, average particle size 80 nm, DBP absorption amount is of 29cm ³ / 100g. The pitch A is a coal tar pitch having a softening point of 110 ° C. and a fixed carbon ratio of 60% by mass. The pitch B is a coal tar pitch having a softening point of 300 ° C. and a fixed carbon ratio of 83% by mass. A mesophase pitch having a softening point of 350 ° C. and a fixed carbon ratio of 85% by mass was used. Metal cobalt having a purity of 95% by mass was used.
Further, as various additives, alumina cement as a hardener, sodium phosphate as a dispersant and sodium salt of naphthalenesulfonic acid formalin condensate, and boron carbide as an antioxidant were added. Here, the proportion of alumina cement in various additives is 2 mass%, the proportion of sodium phosphate is 0.05 mass%, the proportion of sodium salt of formalin naphthalene sulfonate formalin is 0.05 mass%, the proportion of boron carbide is The content was 0.9% by mass.

The flow-through, corrosion resistance, explosion resistance, and oxidation resistance of the cast refractories of the present invention and comparative products obtained are evaluated and listed in Tables 1-4. The evaluation method is as follows.
(1) Evaluation of fluidity Judgment was made based on the required water ratio when adjusting the tap flow value by a test method according to JIS R 2521 to be 135 to 145. That is, the smaller the required moisture ratio, the better the flowability of the poured refractory. In a material with poor fluidity, a large amount of moisture is required to obtain a construction body, and pores increase after drying, resulting in poor corrosion resistance. Cast refractories with a required moisture ratio of less than 5.9% by weight are evaluated as ◎, cast refractories with 5.9 to 6.5% by weight are evaluated as ◯, and cast refractories with more than 6.5% by weight are evaluated as ×. did.

(2) Evaluation of corrosion resistance Each cast refractory of the present invention product and comparative product was cast and molded, and cured for 24 hours at 30 ° C to obtain a 40 mm x 40 mm x 160 mm specimen, and a slag erosion test was conducted by the rotating drum method. did. A test was conducted at 1600 ° C. for 5 hours using 1 kg of blast furnace slag of C / S (CaO / SiO ₂ mass ratio) ≈1.2 as an erodant. Blast furnace slag was discharged every hour and replaced with new blast furnace slag. The heating method was arc heating. After completion of the test, the melt depth of the test specimen was measured, and the melt depth of the comparative product 11 shown in Table 3 was taken as 100 and displayed as an index. That is, the corrosion resistance index indicates that the smaller the numerical value, the smaller the amount of erosion loss and the better the corrosion resistance. A cast refractory having a melting index of less than 100 was evaluated as ◎, a cast refractory with 100 to 115 was evaluated as ◯, and a cast refractory greater than 115 was evaluated as ×.

(3) Evaluation of explosion resistance Each cast refractory of the product of the present invention and the comparative product was poured into a cylindrical mold having a diameter of 80 mm and a height of 80 mm, and cured at 30 ° C. for 24 hours to prepare a specimen. . The obtained specimen is put in an electric furnace maintained at a predetermined temperature, held for 20 minutes, and visually checked for explosion. The maximum temperature at which no explosion occurred was defined as the explosion limit temperature. That is, the higher the explosion limit temperature, the better the explosion resistance. The test was conducted every 100 ° C. with an upper limit of 800 ° C. A cast refractory having an explosion limit temperature higher than 700 ° C. was evaluated as “◎”, a cast refractory higher than 600 ° C. and lower than 700 ° C. was evaluated as “◯”, and a cast refractory lower than 600 ° C. was evaluated as “x”.

(4) Oxidation resistance Each cast refractory of the product of the present invention and the comparative product is poured into a 40 mm × 40 mm × 160 mm mold, cured at 30 ° C. for 24 hours, deframed, and dried at 110 ° C. for 24 hours. I got a specimen. The obtained specimen was heated and naturally cooled once in a coke breeze at 1500 ° C. for 3 hours, and the mass was measured. Then, the mass of the test body after repeating heating and natural cooling 4 times additionally was measured. The oxidation resistance was evaluated based on the mass increase rate after the first heating and after the fifth heating. That is, C is not oxidized because it is heated in the coke breeze, but SiC is oxidized by the reaction with CO gas according to the formula (3), resulting in an increase in mass. Therefore, the smaller the mass increase rate, the more the SiC is not oxidized and the better the oxidation resistance. The cast refractory having a mass increase rate of less than 0.6 was evaluated as ◎, the cast refractory having 0.6 to 0.7 was evaluated as ◯, and the cast refractory greater than 0.7 was evaluated as ×.

Comprehensive evaluation Comprehensive evaluation was made with the worst evaluation among the evaluation items. ◎ is optimal, ○ is acceptable, and x is inappropriate.

As can be understood from Tables 1 to 4, the products 11 to 21 of the present invention are superior in fluidity, corrosion resistance, explosion resistance and oxidation resistance as compared with the comparative products 1 to 11.
Hereinafter, the cast refractories shown in Tables 1 to 4 will be briefly described.
The comparative product 1 is a blend in which the blending ratio of silicon carbide is 40% by mass. Invention products 1 to 5 are blends in which the blending ratio of silicon carbide is within the range of 50 to 90% by mass. Comparative product 2 is a mixture in which the mixing ratio of silicon carbide is 95 mass% and the mixing ratio of alumina is 0.5 mass%. In the comparative product 1, since the compounding ratio of silicon carbide is less than 50% by mass, the corrosion resistance is inferior. Moreover, in the comparative product 2, since the compounding ratio of silicon carbide is more than 90% by mass and the compounding ratio of alumina is less than 1% by mass, the fluidity is inferior.
Comparative product 3 is a blend in which the blending ratio of alumina is 48 mass%. In Comparative Example 3, since the compounding ratio of alumina is more than 41% by mass, the corrosion resistance is inferior.
The comparative product 4 is a blend in which the blending ratio of carbon black is 0.1% by mass. The comparative product 5 is a blend in which the blending ratio of carbon black is 10% by mass. In Comparative product 4, the carbon black content is less than 0.3% by mass, so that the corrosion resistance is poor. Moreover, in the comparative product 5, since there are more compounding ratios of carbon black than 9 mass%, it is inferior to fluidity | liquidity.
Comparative product 6 is a blend with a pitch blending ratio of 0.1 mass%. Comparative product 7 is a blend with a blending ratio of 6% by mass. In comparative product 6, since the blending ratio of pitch is less than 0.3% by mass, the oxidation resistance is inferior. Moreover, in the comparative product 7, since the blending ratio of the pitch is more than 5% by mass, the explosion resistance is inferior.
The comparative product 8 is a blend in which the blending ratio of the mesophase pitch is 0.1% by mass. Comparative product 9 has a mesophase pitch blending ratio of 8% by mass. In Comparative Product 8, the blending ratio of mesophase pitch is less than 0.3% by mass, so that the explosion resistance is poor. Moreover, in the comparative product 9, since the blending ratio of mesophase pitch is more than 7% by mass, the fluidity is inferior.
The comparative product 10 is a blend in which the blending ratio of silicon carbide is 15% by mass. In comparative product 10, since the compounding ratio of silicon carbide is less than 50% by mass, the corrosion resistance is inferior.
Comparative product 11 is a blend using only carbon black and pitch as carbonaceous raw materials. Comparative product 11 is inferior in explosion resistance because no mesophase pitch raw material is added.
Invention product 22 is obtained by replacing pitch A with pitch B in the formulation of product 1 of the invention. In the product 22 of the present invention, since the softening point of the pitch B is as high as 300 ° C., the oxidation resistance is slightly inferior.
The comparative product 12 is a blend using metal cobalt disclosed in Patent Document 3 as an antioxidant. The comparative product 12 is inferior in corrosion resistance because it contains metallic cobalt. Here, in Patent Document 3, it is said that the addition of metallic cobalt is effective for preventing oxidation at a short time and at a low temperature (1000 ° C.-3 hours). The oxidation resistance was evaluated at a high temperature and for a long time in a CO gas atmosphere approximated to the usage situation of the main pole, and the oxidation resistance was deteriorated by the addition of metallic cobalt. This is considered to be due to the following reasons. That is, metallic cobalt is oxidized to produce cobalt oxide, and this cobalt oxide reacts with SiO gas to produce cobalt silicate. For this reason, the SiO partial pressure in the specimen decreases, and further SiO gas is generated from SiC. As a result, it is presumed that the oxidation of SiC is further promoted.
Comparative product 13 is a blend using only carbon black as a carbonaceous raw material. Comparative product 13 is inferior in oxidation resistance and explosion resistance because pitch and mesophase pitch are not used together.
The comparative product 14 is a blend using only pitch as a carbonaceous raw material. Comparative product 14 is inferior in corrosion resistance and explosion resistance because carbon black and mesophase pitch are not used together.
Comparative product 15 is a blend using only meso-fez pitch as a carbonaceous raw material. Comparative product 15 is inferior in corrosion resistance and oxidation resistance because carbon black and pitch are not used together.
Comparative product 16 is a blend using carbon black and pitch as the carbonaceous raw material. Comparative product 16 is inferior in explosion resistance because it does not use mesophase pitch.
Comparative product 17 is a blend using carbon black and mesophase pitch as carbonaceous raw materials. The comparative product 17 is inferior in oxidation resistance because no pitch is used in combination.
The comparative product 18 is a blend using pitch and mesophase pitch as the carbonaceous raw material. Since the comparative product 18 does not use carbon black in combination, it is inferior in corrosion resistance.
As described above, the superiority of the product of the present invention is clear.

Claims (1)

  Silicon carbide-alumina-carbon blast furnace main slag line cast refractory, carbonaceous material comprising 50 to 90 mass% silicon carbide raw material, 1 to 41 mass% alumina raw material, and carbon black, pitch and mesophase pitch The raw material is in the range of 0.9 to 21% by mass, the carbon black is in the range of 0.3 to 9% by mass, the pitch is in the range of 0.3 to 5% by mass, and the mesophase pitch is in the range of 0.3 to 7% by mass. Cast refractories for blast furnace main slag lines.