Method of producing plate brick

Abstract

To provide a method of producing a plate brick, capable of further improving the digestion resistance of a plate brick obtained from a refractory material compound containing Al, Si and C.SOLUTION: In a method of producing a plate brick, an organic binder is added to a refractory raw material mixture including 1 mass% or more and 4 mass% or less of raw material carbon, an aluminum-silicon alloy of a Si content of 8 mass% or more and 40 mass% or less, and the balance mainly consisting of a refractory aggregate, thereafter the mixture is kneaded, molded, and then heat-treated at a temperature of 800°C or higher and 1350°C or lower in a non-oxidizing atmosphere, in which the ratio RSi / (RSi+RAl) of an Si content RSi relative to an Al content RAl in the refractory raw material mixture is 0.5 or more and 0.8 or less, RAl is 0.5 or more and 5 or less, 85% or more of RAl is derived from the aluminum-silicon alloy, a total carbon value TC is 2 or more and 5 or less, and TC / (RSi+TC) is 0.3 or more and 0.67 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing plate bricks for use in sliding nozzle devices for controlling the flow rate of molten metal. [Background technology]

[0002] In steel production, sliding nozzle devices are used to control the flow rate of molten steel discharged from molten metal vessels such as ladles and tundishes. These sliding nozzle devices use two or three refractory plate bricks with nozzle holes. These plate bricks are stacked and slid together under pressure, and the flow rate of molten steel is adjusted by adjusting the opening of the nozzle holes.

[0003] These plate bricks contain aluminum or aluminum alloys containing Al to impart corrosion resistance and oxidation resistance. Al has a melting point of 660°C, which is lower than that of silicon (1410°C), and thus reacts at a lower temperature to exert its effects. Aluminum-added plate bricks are classified into unfired or light-fired types, which are heated at temperatures below the melting point of Al, and high-temperature-fired types, in which Al is reactively sintered at temperatures above the melting point. Unfired and light-fired plate bricks derive their strength primarily from the hardening of phenolic resin. However, during casting, Al in the structure, particularly near the working surface, is subjected to high temperatures, which cause reactive sintering with C in the refractory and the atmosphere in the pores, producing Al4C3, Al2O3, and other substances. The formation of these substances densifies the structure, resulting in improved hot strength and corrosion resistance, as shown in Non-Patent Document 1 and Patent Document 1.

[0004] Furthermore, with regard to corrosion resistance, particularly corrosion resistance against FeO, Non-Patent Document 2 and Patent Document 2 show that during actual use, Al and Al4C3 inside the structure become gaseous, such as Al gas, at high temperatures and migrate to the working surface, where they react with O in the molten steel to form a dense Al2O3 layer at the interface, which functions as a protective layer and exhibits excellent durability. Al4C3 is easily produced in the presence of Al and C at temperatures above 800°C, but it is also easily hydrated by moisture in the air. Therefore, if Al4C3 is present in the structure of a refractory, when stored under high-humidity conditions, the Al4C3 expands in volume due to hydration, and gas is generated as a result of the hydration, causing cracks in the refractory and the structure to collapse, a phenomenon known as slaked refractory. While unfired and lightly fired materials do not produce Al4C3 during manufacturing, they do produce Al4C3 when exposed to heat during actual use. Therefore, under conditions of reuse or recovery and processing of used products, cracks or powdering due to slaked refractory material make it unusable.

[0005] On the other hand, materials fired at high temperatures above the melting point of aluminum can produce easily slaked Al4C3 in the refractory structure depending on the firing temperature and conditions, making them susceptible to slaked refractory structures due to the storage conditions at the user and, especially when shipped overseas, the long storage periods caused by the use of sea freight. For this reason, materials fired at high temperatures with added aluminum are impregnated with pitch or tar after firing to prevent contact with moisture in the air and suppress slaked refractory structures. However, even pitch impregnation cannot completely prevent slaked refractory structures.

[0006] In contrast, Patent Document 3 discloses a method for producing plate bricks by adding an organic binder to a refractory raw material mixture containing aluminum and / or an aluminum alloy and 0.5% to 5% by mass of silicon, kneading the mixture, molding it, and then firing it in a nitrogen gas atmosphere at 1000°C to 1400°C. Specifically, firing in a nitrogen atmosphere facilitates the reaction between Al and N, promoting the formation of AlN and suppressing the formation of Al4C3, which is a cause of slake. Furthermore, adding silicon also produces SiC, which suppresses the formation of Al4C3 and makes slake less likely. However, Patent Document 3 requires firing in a nitrogen atmosphere, which increases costs due to the use of nitrogen gas as the firing atmosphere gas. Furthermore, even if silicon is added, Al4C3 is formed in regions of the brick structure where Al is present alone, which can cause slake. This creates a risk of slake under more severe conditions.

[0007] Patent Document 4 discloses a method for producing plate bricks by adding an organic binder to a refractory raw material blend containing 75 to 97 mass% alumina raw material, 0.5 to 20 mass% aluminum and / or aluminum alloy, and 0.1 to 15 mass% of one or more of silicon, clay, silicon carbide, and boron carbide. The blend is then kneaded, molded, and heat-treated at 400 to 800°C. In Patent Document 4, the heat treatment is performed at temperatures of 400 to 800°C, so the amount of Al4C3 produced by firing is small. However, during actual use, the inner bore and working surfaces are exposed to high temperatures of 1000°C or higher for long periods of time, which generates Al4C3 during use. Therefore, recycling used bricks poses a risk of fire.

[0008] Patent Document 5 discloses an alumina-carbon slide gate plate that contains 1-15% by mass of an aluminum-silicon alloy on a refractory raw material composed of an alumina refractory aggregate and a carbon-containing raw material with a carbon content of 1-10% by mass, and is heat-treated at temperatures exceeding 1000°C and up to 1500°C. Patent Document 5 also claims that the combined use of Al and Si forms a thin SiO2 layer around silicon or aluminum particles, preventing aluminum slaking. On the other hand, it claims that using Al and Si as an aluminum-silicon alloy, rather than using them individually, results in the formation of Al4SiC4 and AlN, with less Al4C3 formation, resulting in excellent slaking resistance.

[0009] On the other hand, Non-Patent Document 3 reports that Al4SiC4, like Al4C3, is easily hydrated and becomes a cause of slaked steel. This report shows that when aluminum and silicon are added together, a eutectic occurs at the contact points between the aluminum particles and the silicon particles during firing, and when it reacts with the surrounding C, SiC is produced preferentially over Al4C3 in terms of energy. It is reported that C is consumed in the production of SiC, and the suppression of the production of Al4C3 has the effect of improving slaked resistance.

[0010] Therefore, although Patent Document 5 discloses an aluminum silicon alloy with a Si content of 5 to 50 mass%, if an aluminum silicon alloy with a low Si content is used and the amount of C is greater than the amount of Si that produces SiC, Al4C3 and Al4SiC4 are produced, and this can be easily understood when evaluated under stricter conditions. Furthermore, the higher the Si content of an aluminum silicon alloy, the higher the melting point and the more difficult it is to produce, and the aluminum silicon alloy with a Si content of 50 mass% shown in Patent Document 5 is an extremely expensive raw material and is therefore not practical.

[0011] Furthermore, Patent Document 6 discloses plate bricks made using 2-23% by mass of Al4SiC4 and 2-10% by mass of carbon material, fired at 150-1400°C. Patent Document 6 also shows that the occurrence of cracks in the plate due to hydrogen sulfide gas can be suppressed by keeping the S content in Al4SiC4 at 100 ppm or less. However, since Al4SiC4 itself hydrates, it can cause slaking problems under more severe hydration conditions. Furthermore, Al4SiC4 is a very expensive raw material, making it impractical.

[0012] Patent Document 7 also discloses a carbon-containing brick characterized by having an apparent porosity of 13% or less after heating at 1000°C for 3 hours in a reducing atmosphere, with an outer percentage of 0.1 to 10% by mass of Al and / or an Al-containing alloy relative to 100% by mass of refractory aggregate and carbonaceous raw materials. The brick also contains 0.03 to 5% by mass of an alkali metal compound, calculated as alkali metal oxide, based on the alkali metal compound. Patent Document 7 claims that the addition of alkalis, glycols, or water-soluble alkali metal compounds promotes the oxidation of Al to form Al2O3 through the "oxidizing or catalytic action" that occurs when the alkali evaporates and gasifies at high temperatures, resulting in the formation of Al4C3 and AlN, without any intermediate products remaining. This results in a carbon-containing brick that does not present problems with practical use. However, the addition of alkali metal compounds is undesirable because it reduces the heat resistance and corrosion resistance of the plate brick. Furthermore, when the added alkali metals volatilize, the volatilized residue becomes voids, resulting in a high porosity in the brick structure, which is a factor in deteriorating the properties of the plate brick, such as its corrosion resistance.

[0013] Numerous proposals have been made to prevent firefighting for aluminum-added plate bricks. However, in recent years, environmental improvements have been required, and with the goal of sustainable improvement, interest in recycling refractories has grown. Plate bricks are often recovered after use and reprocessed for reuse as recycled plates. When plate bricks are recycled, they are recovered after being subjected to thermal stress. In the recycling process, the sliding surfaces of plate bricks that develop cracks during use are wet polished and then dried by heating. After use, the bricks are recovered, reprocessed, and stored again in front of the furnace before being reused. Depending on the conditions, this can result in long-term storage, which creates even more severe firefighting conditions. For these reasons, previous proposals are insufficient to ensure trouble-free use under even more severe firefighting conditions, and further improvements are needed. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] WO 15 / 129745 [Patent Document 2] WO 18 / 155030 [Patent Document 3] International Publication No. 10 / 071196 [Patent Document 4] International Publication No. 09 / 119683 [Patent Document 5] Japanese Patent Application Laid-Open No. 2012-192430 [Patent Document 6] Patent No. 6646779 [Patent Document 7] Japanese Patent Application Laid-Open No. 2004-149330 [Non-patent literature]

[0015] [Non-Patent Document 1] Hiroshi Shikano, Tsutomu Harada, Kenji Otsuka, Toshiaki Kaneko: Refractories 39

[11] 638-640(1987) [Non-patent document 2] Yasushi Sato, Akira Yamaguchi, Riki Harada: Refractories 39

[12] 709-712 (1987) [Non-patent document 3] Toshihiko Okamoto, Keiichiro Akamine, Koichi Shimizu, Kiyoshi Goto: Proceedings of the 11th Iron and Steel Refractories Research Meeting, 140-153 (2023) Summary of the Invention [Problem to be solved by the invention]

[0016] The problem to be solved by the present invention is to provide a method for producing plate bricks which can further improve the slaking resistance of plate bricks obtained from a refractory raw material blend containing Al, Si and C. [Means for solving the problem]

[0017] In order to solve the above problems, the present inventors have repeatedly conducted tests and studies on plate bricks obtained from refractory raw material compositions containing Al, Si, and C, focusing on the respective contents and ratios of Al, Si, and C, the state of Al and Si in the refractory raw material composition, and the heat treatment temperature and atmosphere, in order to determine the conditions necessary for maintaining excellent properties such as corrosion resistance, oxidation resistance, and strength, while also achieving excellent slaking resistance. As a result, they have found conditions under which slaking is not affected even under more severe conditions.

[0018] That is, according to one aspect of the present invention, there is provided the following method for manufacturing a plate brick. A method for producing plate bricks, comprising adding an organic binder to a refractory raw material mixture containing 1% by mass or more and 4% by mass or less of a carbon raw material, an aluminum silicon alloy having a Si content of 8% by mass or more and 40% by mass or less, and the remainder being mainly refractory aggregate, kneading the mixture, forming the mixture, and then heat treating the mixture at 800°C or more and 1350°C or less in a non-oxidizing atmosphere, The Si content in the refractory raw material blend is R Si (mass%), Al content R Al(mass%), R Si / (R Si +R Al ) is between 0.5 and 0.8, R Al is between 0.5 and 5, and R Al 85% or more of the aluminum silicon alloy is derived from the aluminum silicon alloy, Furthermore, the C content in the refractory raw material mixture is R C (mass%), the addition rate of the organic binder to the refractory raw material mixture is A (mass%), and the residual carbon rate of the organic binder is B (%), R C + (A×B / 100) total carbon value T C is between 2 and 5, and T C / (R Si +T C ) is 0.3 or more and 0.67 or less. [Effects of the Invention]

[0019] According to the present invention, the slaking resistance of plate bricks obtained from a refractory raw material blend containing Al, Si and C can be further improved. DETAILED DESCRIPTION OF THE INVENTION

[0020] Under non-oxidizing atmosphere and high temperature conditions of 800℃ or higher, Al and C easily form Al4C3, which is easily hydrated according to the following reaction formula: Al4C3(s)+12H2O(l,g)=4Al(OH)3+3CH4(g)…(1) The hydration reaction of Al4C3 to Al(OH)3 causes volume expansion. Furthermore, volume contraction occurs due to the generation of methane gas, etc., and these volume expansions and contractions destroy the brick structure, causing cracks and pulverization, which leads to slaking. Thus, plate bricks containing Al and C can easily generate Al4C3 within their structure, depending on the heat treatment and usage conditions, causing slaking and becoming a cause of trouble.

[0021] Therefore, in this study, we investigated and considered the conditions that make slaking difficult in the manufacturing method of plate bricks containing Al, Si, and C and heat-treated at high temperatures. First, referring to Non-Patent Document 3, samples containing different Al / Si content ratios were embedded in coke and heat-treated at 1200°C in a carbon monoxide atmosphere. The slaking resistance was evaluated in an autoclave test to determine the Al / Si ratio that makes slaking difficult. We also investigated and considered the mechanism by which the inclusion of Si along with Al improves slaking resistance. As a result, as shown in Non-Patent Document 3, it was found that increasing the Si content relative to the Al content suppresses the formation of Al4C3 and Al4SiC4, which are factors that cause slaking, and promotes the formation of SiC, which is resistant to slaking. Furthermore, as brick properties, increasing the Si content and decreasing the Al content tended to significantly decrease strength and elastic modulus, and increase apparent porosity. The slaking resistance of these samples was evaluated in an autoclave test. Samples with high Si content, in which no or only trace amounts of Al4C3 were formed, did not slaking. Specifically, samples containing only Al and samples with a Si to Al ratio of 0:1 to 1:1 were digested, but samples containing only Si and samples with a Si to Al ratio of 1:0 to 3:2 were not digested. In other words, samples with no or little production of Al4C3 and Al4SiC4 were not digested.

[0022] Observation of the microstructures of these samples revealed that in the sample containing only Al, spherical aluminum particles melted, and the molten Al dissolved out of the particles, generating a reaction product thought to be primarily composed of Al4C3. Furthermore, voids were formed inside the particles due to the dissolution of Al to the outside of the particles. The reaction product, thought to be Al4C3, was formed by connecting the reaction traces of the aluminum particles, including voids, and this strong connective tissue was thought to provide high strength and a dense structure. However, this connective tissue easily disintegrated upon hydration, which is thought to be the cause of the slaking phenomenon that results in cracks and disintegration of the brick structure. In the sample containing only Si, a large amount of residual silicon (unreacted Si) was observed in the crushed particles, indicating that the reaction had progressed from the surface of some silicon particles to generate reaction products. In contrast, in the sample that used both aluminum and silicon, where the aluminum particles and silicon particles came into contact, the molten Al absorbed the silicon particles, and both the Al and Si were melted (eutectic), generating a reaction product.The results of the investigation using EPMA indicated that the reaction product of the molten silicon was thought to be SiC. This shows that compared to when silicon is contained alone, when both aluminum and silicon are contained, Si, which has a high melting point, melts at the points where the aluminum particles and silicon particles come into contact, generating a large amount of SiC, accelerating the reaction.

[0023] The reaction between the eutectic structure of Al and Si and C is shown below. 4 / 3Al(l)+C(s)=4 / 3Al4C3(s)…(2) Si(l) + C(s) = SiC(s)…(3) From the results of observations using a microscope and EPMA, it was thought that reaction (3) proceeded more preferentially than reaction (2). Therefore, in order to consider the thermodynamics, the free energy change associated with each reaction was calculated. As a result, it was found that within the temperature range of the heat treatment used in this invention, reaction (3) had a lower free energy change ΔG associated with the reaction than reaction (2), and SiC was more stable and was produced preferentially than Al4C3.

[0024] From the above, it was found that suppressing the formation of Al4C3, which is the cause of slaking, is effective in significantly improving the slaking resistance of plate bricks obtained from refractory raw material mixtures containing Al, Si, and C. Furthermore, to suppress the formation of Al4C3, it is desirable for Al and Si to be in a eutectic state under high-temperature conditions during heat treatment or in actual use, and even if C reacts with the eutectic structure of Al and Si, C reacts preferentially with Si and is consumed to form SiC, resulting in the suppression of the formation of Al4C3 due to the reaction of C with Al.

[0025] Furthermore, as a result of repeated testing and investigations, the present inventors have found that in order to reliably form a eutectic structure of Al and Si under high temperature conditions, it is effective to ensure that the ratio of the Al content to the Si content in the refractory raw material blend is within a specific range, and that the ratio of the Si content to the total carbon value is within a specific range, and further that an aluminum-silicon alloy is used as the Al source.

[0026] The present invention has been conceived based on the above findings and considerations, and the gist of the present invention is as follows. A method for producing plate bricks, comprising adding an organic binder to a refractory raw material mixture containing 1% by mass or more and 4% by mass or less of a carbon raw material, an aluminum silicon alloy having a Si content of 8% by mass or more and 40% by mass or less, and the remainder being mainly refractory aggregate, kneading the mixture, forming the mixture, and then heat treating the mixture at 800°C or more and 1350°C or less in a non-oxidizing atmosphere, The Si content in the refractory raw material blend is R Si (mass%), Al content R Al (mass%), R Si / (R Si +R Al ) is between 0.5 and 0.8, R Al is between 0.5 and 5, and R Al 85% or more of the aluminum silicon alloy is derived from the aluminum silicon alloy, Furthermore, the C content in the refractory raw material mixture is R C(mass%), the addition rate of the organic binder to the refractory raw material mixture is A (mass%), and the residual carbon rate of the organic binder is B (%), R C + (A×B / 100) total carbon value T C is between 2 and 5, and T C / (R Si +T C ) is 0.3 or more and 0.67 or less.

[0027] As described above, the method for producing plate bricks of the present invention basically comprises adding an organic binder to a refractory raw material mixture containing a carbon raw material and an aluminum-silicon alloy, with the remainder being mainly refractory aggregate, kneading and molding the mixture, and then heat treating the mixture in a non-oxidizing atmosphere at a temperature of 800°C to 1350°C.

[0028] In the present invention, the refractory aggregate primarily contained in the remainder of the refractory raw material blend can be one or more selected from alumina raw materials, alumina-zirconia raw materials, zirconia-mullite raw materials, magnesia raw materials, spinel raw materials, and silicon carbide raw materials, which are commonly used as raw materials for refractories. For example, an electrofused raw material produced by arc melting, or a sintered raw material produced in a shaft kiln or rotary kiln can be used. The electrofused raw materials include fused alumina, fused magnesia, fused spinel, fused mullite, fused alumina-zirconia, fused zirconia-mullite, and fused zirconia. The sintered raw materials include sintered alumina, sintered magnesia, sintered mullite, and sintered spinel. In the present invention, the remainder of the refractory raw material blend is primarily composed of the above-mentioned refractory aggregate, but may also contain calcined alumina and carbides, borides, and nitrides such as boron carbide, silicon nitride, and aluminum nitride, as appropriate.

[0029] In the present invention, the refractory raw material composition contains, in addition to the refractory aggregate, a carbon raw material and an aluminum-silicon alloy. The carbon raw material can be an amorphous or crystalline carbon powder commonly used as a refractory raw material, such as pitch, coke, calcined anthracite, flake graphite, artificial graphite, or carbon black. Also, aluminum-silicon alloys commonly used as refractory raw materials can be used, but in the present invention, those with a Si content of 8% by mass or more and 40% by mass or less are used. In the following description, aluminum-silicon alloys with a Si content of 8% by mass or more and 40% by mass or less are also referred to as "specific aluminum-silicon alloys."

[0030] In the present invention, an organic binder is added to the above-mentioned refractory raw material blend, kneaded, molded, and then heat-treated at 800°C to 1350°C in a non-oxidizing atmosphere. Organic binders commonly used in refractories for imparting strength during molding, forming carbon bonds, etc. can be used, but phenolic resins are most preferred. Phenolic resins can be any of novolac, resol, powder, and solvent-based liquid types.

[0031] In the present invention, the heat treatment is carried out in a non-oxidizing atmosphere. For example, the heat treatment in a non-oxidizing atmosphere can be carried out by placing the molded body and coke powder in a refractory container, or by a known method of controlling the atmospheric gas. In the present invention, the heat treatment is carried out at a temperature of 800°C or higher and 1350°C or lower. If the heat treatment temperature is lower than 800°C, sintering due to the reaction between Al and Si is insufficient, and sufficient strength cannot be obtained. On the other hand, if the heat treatment temperature exceeds 1350°C, excessive sintering occurs, resulting in significantly high strength and high elastic modulus, and reduced spalling resistance. This can also be a factor in the generation of cracks during heat treatment.

[0032] In the above basic structure, the present invention is characterized in that the Si content in the refractory raw material mixture is R Si (mass%), Al content R Al (mass%), R Si / (RSi +R Al ) is between 0.5 and 0.8, R Al is between 0.5 and 5, and R Al The primary technical feature is that 85% or more of the product is derived from a specific aluminum-silicon alloy. That is, to ensure the formation of a eutectic structure of Al and Si during heat treatment, R Si / (R Si +R Al ) must be between 0.5 and 0.8. Si / (R Si +R Al If R is less than 0.5, sufficient slake resistance cannot be obtained due to the formation of Al4C3. Si / (R Si +R Al ) exceeds 0.8, the slaking resistance is good, but the Al content is low, so that sufficient strength and corrosion resistance against iron oxide (FeO) for plate bricks cannot be obtained.

[0033] In the present invention, the Al content (R Al ) is 0.5% by mass or more and 5% by mass or less. If the Al content is less than 0.5% by mass, properties such as strength and corrosion resistance become insufficient. On the other hand, if the Al content exceeds 5% by mass, excessive sintering occurs, making the structure stronger and significantly reducing spalling resistance. In addition, the Al content (R Al ) is derived from a specific aluminum silicon alloy. Al ) from sources other than specific aluminum-silicon alloys, it may be digested by forming Al4C3. As described above, the present invention uses a specific aluminum silicon alloy, i.e., an aluminum silicon alloy with a Si content of 8% to 40% by mass, as the main Al source. If an aluminum silicon alloy with a Si content of less than 8% by mass is used as the main Al source, the amount of Si in the eutectic mixture of Al and Si is small, and there is a possibility that Al4C3 will be generated and consumed in the part where the aluminum silicon alloy exists as a simple substance. Furthermore, an aluminum silicon alloy with a Si content of more than 40% by mass has a high melting point, making the production of such an aluminum silicon alloy difficult and unsuitable for industrial use.

[0034] In addition to the first technical feature described above, the present invention further comprises: C (mass%), the addition rate of organic binder to the refractory raw material mixture is A (mass%), and the residual carbon rate of the organic binder is B (%). C + (A×B / 100) total carbon value T C is between 2 and 5, and T C / (R Si +T C ) is between 0.3 and 0.67 inclusive, which is the second technical feature.

[0035] C content in the refractory raw material mixture (R C ) is derived from the carbon raw material. In the present invention, the refractory raw material blend contains the carbon raw material in a content of 1% by mass or more and 4% by mass or less. The carbon raw material has effects such as suppressing excessive sintering of the refractory material, reducing the elastic modulus, increasing thermal conductivity, and imparting slag resistance. However, if the carbon raw material content in the refractory raw material blend is less than 0.5% by mass, these effects cannot be fully obtained. On the other hand, if the carbon raw material content exceeds 4% by mass, Al4C3, which is a cause of slaked refractory, is more likely to be produced and oxidation resistance is reduced.

[0036] In the present invention, the total carbon value T C As mentioned above, is the C content (R C) and the carbon residue of the organic binder (A × B / 100). In the present invention, this total carbon value T C is in the range of 2 to 5. Both the C derived from the carbon raw materials in the refractory raw material blend and the C derived from the residual carbon in the organic binder have the effect of reducing the elastic modulus of the refractory and improving its slag resistance, and the C derived from the residual carbon in the organic binder also has the effect of forming carbon bonds. On the other hand, it can react with the eutectic of Al and Si and become a C source for SiC and Al4C3. That is, the total carbon value T C If the total carbon value T is less than 2, the effect of reducing the elastic modulus and imparting slag resistance cannot be fully obtained. C If the value exceeds 5, not only SiC but also Al4C3 is generated, which causes a decrease in slaking resistance.

[0037] Therefore, the present inventors have determined that the total carbon value T C and Si content R Si After repeated testing and investigations focusing on the relationship between C / (R Si +T C It was found that it is effective to set T between 0.3 and 0.67. C / (R Si +T C If T is less than 0.3, the amount of SiC generated is small, and sufficient strength cannot be obtained. In addition, the amount of C is small, and the modulus of elasticity increases, resulting in a decrease in spalling resistance. C / (R Si +T C ) exceeds 0.67, the amount of C becomes excessive relative to the amount of SiC produced, resulting in the production of Al4C3 and a decrease in slaking resistance.

[0038] As described above, the present invention provides the first and second technical features, thereby enabling plate bricks obtained from a refractory raw material blend containing Al, Si, and C to further improve slaking resistance while maintaining excellent properties such as corrosion resistance, oxidation resistance, and strength. Specifically, plate bricks can be obtained that do not crack or pulverize due to slaking even when heated for 6 hours at 158°C in an autoclave test. The inventors investigated whether it would be possible to reproduce the slaking phenomenon using various evaluation methods for actual plate bricks that had slaking problems while stored at a customer's site. As a result, the plate bricks that had slaking problems exhibited slaking due to structural breakdown, such as cracking and pulverization of the brick structure, when heated for 6 hours at 158°C in an autoclave test. Furthermore, plate bricks with no prior slaking problems did not slaking when evaluated using this evaluation method. In other words, whether or not slaking occurs when heated for 6 hours at 158°C in an autoclave test is an indicator of whether or not a slaking problem will actually occur.

[0039] The present invention may further include a step of impregnating the material with coal tar or pitch after the heat treatment in order to densify the structure and impart strength and corrosion resistance, and may also include a step of heat treatment after the impregnation in order to remove harmful substances contained in the coal tar or pitch. [Example]

[0040] Tables 1 and 2 show examples of the present invention and comparative examples, respectively.

[0041] [Table 1]

[0042] [Table 2]

[0043] A phenolic resin with a residual carbon content of 30% was added as an organic binder at the addition rate shown in Tables 1 and 2 to 100% by mass of the refractory raw material compound with the blending ratios shown in Tables 1 and 2. The mixture was kneaded and then formed in an oil press into a shape 230 mm long, 100 mm wide, and 45 mm thick. After drying, the formed body was heat-treated at the temperature also shown in Tables 1 and 2 to obtain a brick sample. The heat treatment was performed in a non-oxidizing atmosphere by embedding the formed body together with coke powder in a silicon carbide brick container, raising the temperature at a rate of 100°C / h, and holding the maximum temperature for 3 hours. The resulting brick samples were evaluated for their properties of bending strength, oxidation wear resistance, corrosion resistance, spalling resistance, and slaking resistance, as described below.

[0044] <Bending strength> The bending strength was measured at room temperature in accordance with JIS R 2213. <Oxidation wear resistance> A sample of a predetermined shape was oxidized in an electric furnace under atmospheric conditions at a temperature of 800°C for 5 hours, and then the oxidized surface was shot blasted with brown alumina abrasive grains. The wear weight after the test was measured and the wear amount was indexed. Specifically, the wear amount of Example 2 was set to a wear index of 100, and the wear index of each sample was calculated. The smaller this wear index, the higher the oxidation wear resistance. <Corrosion resistance> An erosion test was carried out using a high-frequency induction furnace by the lining method. The erosion test was carried out for 3 hours at a temperature of 1600°C using SS400 as the metal and iron oxide as the erosion material. After the test, the lining was disassembled and the cross section of the sample was measured to determine the amount of corrosion damage, which was then indexed. Specifically, the amount of corrosion damage in Example 2 was set to a corrosion index of 100, and the corrosion index for each sample was calculated. The smaller the corrosion index, the higher the corrosion resistance. <Spalling resistance> Spalling tests were conducted using the hot metal immersion method in a high-frequency induction furnace. In the spalling test, samples cut into a rectangular column shape measuring 40 mm x 40 mm x 180 mm were immersed in 1600°C hot metal for 3 minutes and then air-cooled, a process repeated three times, and the degree of cracking was evaluated by visual inspection. In Tables 1 and 2, small cracks are indicated by ○, medium cracks by △, and large cracks by ×, with ○ or △ representing a pass. <Digestion resistance> Samples processed into a 40 mm x 40 mm x 40 mm shape were placed in an autoclave and heated at 158°C for 6 hours, after which the appearance of the sample was evaluated. In Tables 1 and 2, a good appearance is indicated by ○, and powdering, disintegration, or cracking is indicated by ×. ○ indicates that the sample was not digested in the autoclave test, and × indicates that the sample was digested in the autoclave test.

[0045] Examples 1 to 4 are examples in which the Si content of the aluminum silicon alloy blended in the refractory raw material blend is different, but all are within the range of the present invention, and good properties including slaking resistance were obtained. In contrast, Comparative Example 1 is an example in which an aluminum silicon alloy is not used, but silicon is used. Since Si has a high melting point and is less likely to develop strength through heat treatment than Al, in Comparative Example 1, the Si content (R Si ) was set at 5 mass %, ensuring room temperature bending strength. However, since it did not contain Al, which is effective in improving corrosion resistance, corrosion resistance was significantly reduced. Comparative Examples 2 and 3 are examples in which aluminum was used as the Al source, and both were digested in an autoclave test. Comparative Example 4 is an example in which the Si content (R Si ) is an example using an aluminum silicon alloy with 3 mass % and was also digested in an autoclave test.

[0046] Examples 5 and 6 show the relationship between the Al content (R Al ) are different and R Si / (R Si +R Al Although these are examples in which the composition is different, all are within the scope of the present invention and good properties including slake resistance were obtained. In contrast, in Comparative Example 5, the Al content (R Al ) exceeds the upper limit of the present invention, and excessive sintering occurs during the heat treatment process, resulting in a significant decrease in spalling resistance. Al ) is below the lower limit of the present invention, and the oxidation wear resistance and corrosion resistance were significantly reduced. Comparative Example 7 is R Si / (R Si +R Al ) exceeds the upper limit of the present invention, and the relative Al content (R Al ) was low, the corrosion resistance was significantly reduced. Si / (R Si +R Al ) is below the lower limit of the present invention, and the relative Al content (R Al ) was high, so it was digested in an autoclave test.

[0047] In Examples 7 to 9, the C content (R C ), total carbon value T C , and T C / (R Si +T C Although these are examples in which the composition is different, all are within the scope of the present invention and good properties including slake resistance were obtained. In contrast, in Comparative Example 9, the C content (R C ), total carbon value T C , and T C / (R Si +T C ) exceeds the upper limit of the present invention, and the high C content significantly reduces the oxidation wear resistance and corrosion resistance. In addition, the excessive C content results in the formation of a large amount of Al4C3, which was digested in the autoclave test. On the other hand, Comparative Example 10 is an example in which the C content (R C ), total carbon value T C , and T C / (R Si +T C ) is below the lower limit of the present invention, and spalling resistance was significantly reduced due to the low C content. In addition, the porosity was high and corrosion resistance was also reduced.

[0048] Example 10 is R Al In this example, 85% of the total is derived from the aluminum silicon alloy and the remaining 15% is derived from aluminum, which is within the scope of the present invention and provides good properties including slaking resistance. In contrast, Comparative Example 11 is R Al In this example, 80% of the sample was derived from aluminum-silicon alloy, and the remaining 20% ​​was derived from aluminum. In the area where Al was present alone, Al4C3 was easily formed, and this was digested in the autoclave test.

[0049] Table 3 shows other examples of the present invention and comparative examples.

[0050] [Table 3]

[0051] Examples 11 and 12 are examples in which the composition is the same as Example 2 shown in Table 1 but the only difference is the heat treatment temperature, but they are within the scope of the present invention and good properties including slaking resistance were obtained. In contrast, Comparative Example 12 is an example in which the heat treatment temperature was below the lower limit of the present invention, and both bending strength and oxidation wear resistance were reduced.On the other hand, Comparative Example 13 is an example in which the heat treatment temperature was above the upper limit of the present invention, and spalling resistance was significantly reduced due to excessive sintering. Examples 13 and 14 are examples in which different refractory aggregates were used, but were within the scope of the present invention, and good properties including slake resistance were obtained.

Claims

1. A method for producing a plate brick, comprising adding an organic binder to a refractory raw material mixture containing 1% by mass or more and 4% by mass or less of a carbon raw material, an aluminum silicon alloy having a Si content of 8% by mass or more and 40% by mass or less, and the remainder being mainly a refractory aggregate, kneading the mixture, forming the mixture, and then heat treating the mixture at 800°C or more and 1350°C or less in a non-oxidizing atmosphere, The Si content in the refractory raw material blend is R Ｓｉ (mass%), Al content R Ａｌ (mass%), R Ｓｉ / (R Ｓｉ +R Ａｌ ) is 0.5 or more and 0.8 or less, R Ａｌ is 0.5 or more and 5 or less, and R Ａｌ 85% or more of the aluminum silicon alloy is derived from the aluminum silicon alloy, Furthermore, the C content in the refractory raw material blend is R Ｃ (mass%), the addition rate of the organic binder to the refractory raw material mixture is A (mass%), and the residual carbon rate of the organic binder is B (%). Ｃ + (A × B / 100) Ｃ is 2 or more and 5 or less, and T Ｃ / (R Ｓｉ +T Ｃ ) is 0.3 or more and 0.67 or less.

2. 2. The method for producing a plate brick according to claim 1, wherein the refractory aggregate is one or more selected from the group consisting of an alumina raw material, an alumina-zirconia raw material, a zirconia-mullite raw material, a magnesia raw material, a spinel raw material, and a silicon carbide raw material.

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