JP5880883B2 - Plate brick for slide plate device and manufacturing method thereof - Google Patents

Description

  The present invention relates to a plate brick used for a slide plate device that controls flow rate in casting of molten metal and a method for manufacturing the same.

  In continuous casting of molten metal such as molten steel, a slide plate device is widely used for flow control of molten metal. The slide plate device is a plate brick under the condition that two or three refractory plate bricks with circular apertures are stacked and mechanically pressed from the outside so as not to create a gap between the surfaces. To adjust the aperture area of the aperture and control the flow rate.

  In addition to the strength to withstand mechanical crimping force, these plate bricks have resistance to spalling to prevent damage from thermal shock caused by the passage of hot molten metal, and resistance to seizure and peeling due to reaction with molten metal. Surface damage (molten steel reactivity) is required.

Various refractory materials are used for plate bricks. The most widely used is Al ₂ O ₃ —ZrO ₂ —C based material. When this Al ₂ O ₃ —ZrO ₂ —C material is used for controlling the flow rate of molten steel, the molten steel penetrates into the pores of the refractory, and the so-called seizure prevents the plate brick from sliding. Can be prevented by the presence. In addition, the main component is Al ₂ O _3, which has a low coefficient of thermal expansion and low reactivity with molten steel among refractory raw materials, and therefore suppresses spall damage of plate bricks and surface damage due to reaction with molten steel. be able to. Furthermore, since unstabilized ZrO ₂ is added, microcracks or microspaces due to the phase transition of ZrO ₂ at high temperatures occur in the refractory structure, and the spalling resistance of the plate brick is improved by lowering the elastic modulus. Can be made.

  The manufacturing method of the plate brick is usually as follows. First, a carbon raw material and a metal additive are blended with an oxide raw material such as alumina or alumina-zirconia, and an organic binder such as a phenol resin is added and kneaded with a mixer. The kneaded raw material is press-molded into a plate shape and then dried at 200 to 300 ° C. Non-fired plate bricks that are commercialized in the stage after drying are also used in part. However, most products are fired in a non-oxidizing atmosphere called coke-packing reduction firing in a temperature range of 700 to 1500 ° C. In this firing step, the metal additive reacts with the atmospheric gas and the carbon raw material to change to carbide, nitride, oxynitride, oxide, and the like, thereby imparting strength necessary for the plate brick. The plate brick after firing can be used as it is, but usually, a treatment for impregnating the pores of the plate brick with pitch or tar is performed in order to improve the durability. After impregnation, low-temperature heat treatment (coking treatment) at 700 ° C. or lower is performed to prevent smoke generation during use, and the product is used in a state where volatile components in pitch and tar are reduced.

  When the plate bricks fired and impregnated in this way are used in a slide plate apparatus for continuous casting of molten steel, the following changes occur. Since the pitch and tar impregnated in the pores in the plate brick remain in the initial stage of use, the molten steel brick is prevented from entering the pores. Further, since the remaining pitch and tar react with oxygen in the atmosphere in preference to the carbon mixed in the plate brick material, damage due to oxidation is also prevented. When pitch or tar disappears due to oxidation or the like with use, carbon mixed in the plate brick itself is lost due to oxidation or reaction with molten steel, and a so-called decarburized layer is formed on the working surface. Since the decarburized layer is structurally brittle, it is easily damaged by wear, and when the molten steel infiltrates and seizes, it delaminates during sliding. If surface damage such as wear or delamination occurs, the plate brick can no longer be used.

  Therefore, in order to produce a plate brick with excellent durability, it is necessary to obtain the necessary material strength by firing so that the blended carbon does not oxidize. In addition, control to form pores that are easily impregnated with pitch and tar, and excellent resistance to molten steel that makes it difficult to react with molten steel even after pitch and tar are lost by taking advantage of changes during firing of metal additives Obtaining an organization is also important.

  In order to fire the carbon in the carbon-containing refractory such as plate bricks in the temperature range of 700 to 1500 ° C. without oxidizing, it is essential to lower the oxygen partial pressure in the atmosphere. The coke-packing reduction firing method can reduce the oxygen partial pressure relatively easily and is widely used as a reduction firing method for carbon-containing refractories.

  In this coke-packing reduction firing method, plate bricks are packed together with coke breeze in a refractory container called Saya, and the whole Saya is fired in an oxidizing atmosphere in a tunnel kiln or a shuttle kiln. The coke breeze oxidizes the plate brick earlier during firing to produce CO gas, and consumes oxygen in the sheath to prevent the plate brick from being oxidized. The firing time takes about 3 to 10 days. This is because the plate brick is surrounded by a refractory sheath and heated together with the coke breeze, so that the thermal efficiency is low.

  On the other hand, there has also been proposed a reduction firing method in which a carbon-containing refractory is directly heated using a non-oxidizing atmosphere in the furnace itself without carrying out the filling with coke. This type of reduction firing method has an advantage that the firing time is within one day to about two days.

  For example, in Patent Document 1 described later, a refractory material containing 1 to 10% by mass of a carbon raw material and an organic binder are mixed, and after molding and drying, the oxygen partial pressure is 10 to 10,000 ppm (0.001 to 1% by volume). ) And a plate brick for a sliding nozzle device impregnated with tar and weakly oxidized and fired within 6 to 48 hours. Further, as methods for obtaining this oxygen partial pressure, firing in a weakly oxidizing atmosphere using a burner and blowing of a non-oxidizing gas for incomplete combustion are disclosed.

  In Patent Document 2 described later, a refractory material containing 1 to 10% by mass of a carbon raw material and an organic binder are mixed, and after molding and drying, the oxygen concentration is 0.001 to 0.5% and the carbon dioxide concentration is 0.00. Disclosed is a plate brick for a sliding nozzle device, which is impregnated with tar by weak oxidation firing within 6 to 48 hours in an atmosphere of 1 to 6% and a water vapor concentration of 0.1 to 6%. Moreover, as a method for obtaining this atmosphere, the concentration adjustment of incomplete combustion gas in the burner and dilution by blowing a non-oxidizing gas are disclosed.

In addition, in atmosphere firing without coking with coke breeze, the amount of aluminum nitride generated is increased by utilizing Al-based metal additives in plate bricks and controlling the N ₂ gas concentration in the atmosphere, and the connective structure itself is reduced. A material has also been proposed in which surface damage is less likely to occur even when the effect of pitch and tar components impregnated by strengthening is lost.

For example, in Patent Document 3 described later, an organic binder is added and kneaded to a refractory raw material composition containing aluminum and / or an aluminum alloy, and after molding, fired at 1000 ° C. to 1400 ° C. in a nitrogen gas atmosphere. In the plate brick manufacturing method, the N ₂ gas atmosphere is used when the furnace atmosphere temperature is 300 ° C. or more, and the oxygen gas concentration in the atmosphere is 100 volume ppm or less (0.01 volume%) when the furnace atmosphere temperature is 1000 ° C. or more. And a method for producing a plate brick that keeps the total concentration of carbon monoxide and carbon dioxide gas at 1% by volume or less.

JP 2003-171187 A JP 2003-277129 A International Publication No. 2010/071196

  According to the techniques disclosed in Patent Literature 1 and Patent Literature 2, the firing time can be shortened and productivity can be improved as compared with conventional coke-packing reduction firing. Further, the durability of the plate brick can be improved by improving the tar impregnation property. However, in these techniques, the improvement of the durability is not due to the improvement of the connective structure of the plate brick but to the large amount of impregnation of tar. Therefore, when the volatilization of the gas component from tar progresses during use, a structure similar to that of a conventional coke-packed reduction fired product is obtained. Therefore, although the portion corresponding to the extension of the duration of the tar effect corresponding to the increase in the amount of impregnated tar can improve the durability, surface damage of the plate brick occurs thereafter as in the conventional product. In other words, there was a limit to improving the durability.

  On the other hand, as disclosed in Patent Document 3, when firing in a nitrogen gas atmosphere, the product generated due to the metal additive during firing has more nitride than carbide. In general, carbides have good wettability with molten steel and high solubility. In contrast, nitride is excellent in corrosion resistance to molten steel. For this reason, plate bricks that have increased the amount of nitride produced by firing in a nitrogen gas atmosphere are more likely to cause volatilization of gas components from tar during use than conventional plate bricks that have been coke-packed and reduced-fired. Even if the effect of impregnated pitch and tar components disappears, the formation of a decarburized layer due to reaction with molten steel is delayed. Therefore, the durability is often improved.

  However, plate bricks fired in such a nitrogen gas atmosphere have a problem that the pitch and tar impregnation properties after firing are poor. Therefore, even if the molten steel reactivity can be improved by the formation of nitride, the amount of tar and pitch that can be impregnated is small, so the effects of the tar and pitch components disappear early. As a result, the durability of the plate brick may be reduced.

  As described above, methods for increasing the durability of plate bricks have been proposed, but none of these methods is a technology that can provide a sufficiently satisfactory durability. The current situation is that it has not been established.

  The present invention has been proposed in view of the above-described conventional circumstances, and an object thereof is to provide a plate brick and a method for producing the same that can shorten the firing time and can significantly increase the durability compared to the conventional one. And

  In order to find a firing atmosphere for maximizing the durability of plate bricks, the inventors of the present application produced a test furnace composed of a gas generator and an electric furnace, and used non-oxidizing gases having different compositions as electric The plate brick was fired into the furnace and fired. As a result, it has been found that the strength characteristics and molten steel reactivity of plate bricks are improved by firing while blowing non-oxidizing gas with a high nitrogen gas concentration into the furnace, rather than baking with coke breeze. It was. Further, in the firing under the condition of blowing pure nitrogen gas, the nitride is excessively generated and the impregnation property is rapidly lowered, and further, nitriding is performed by blowing a gas containing a certain amount of carbon monoxide gas (and carbon dioxide gas). It has been found that excessive production of products can be prevented. The inventors of the present application have arrived at the present invention based on the new findings obtained as described above.

  That is, in the method for producing a plate brick for a slide plate device according to the present invention, first, a molded body containing 1 to 10% by mass of a carbon raw material and 1 to 8% by mass of a metal additive is formed. Next, the molded body had a nitrogen gas concentration of 70 to 99% by volume, a carbon monoxide gas concentration of 1% by volume or more, and a total of the carbon monoxide gas concentration and the carbon dioxide gas concentration of 20% by volume or less. Further, a non-oxidizing gas having an oxygen gas concentration of 0.1% by volume or less and a water vapor concentration of 2% by volume or less is blown into the furnace, and is fired in a state of being in direct contact with the non-oxidizing gas in the furnace. . The total of the hydrogen gas concentration and the hydrocarbon gas concentration contained in the non-oxidizing gas is preferably 10% by volume or less. Moreover, the plate brick after baking may be impregnated with tar or pitch. In addition, 1-4 mass% of aluminum or an aluminum containing alloy can be contained as a metal additive.

  On the other hand, in another aspect, the present invention can also provide a plate brick for a slide plate device. That is, the plate brick for the slide plate device according to the present invention is a molded body containing 1 to 10% by mass of a carbon raw material and 1 to 8% by mass of a metal additive, with a nitrogen gas concentration of 70 to 99% by volume. The carbon monoxide gas concentration is 1% by volume or more, the sum of the carbon monoxide gas concentration and the carbon dioxide gas concentration is 20% by volume or less, the oxygen gas concentration is 0.1% by volume or less, and the water vapor concentration is 2% by volume. % Non-oxidizing gas is blown into the furnace, baked in direct contact with the non-oxidizing gas in the furnace, impregnated with tar or pitch, and subjected to coking treatment plate brick for slide plate device is there.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to produce | generate suitable quantity of the nitride which is hard to react with molten steel from a metal additive, the impregnation property of tar or pitch can fully be ensured. As a result, a plate brick for a slide plate device having excellent durability can be realized.

  The plate brick in this invention contains a carbon raw material and a metal additive as a raw material.

  As the carbon raw material, for example, amorphous graphite called carbon black, fine graphite, finely divided solid pitch, coke powder, and the like can be used.

  It is preferable that content of a carbon raw material is 1-10 mass% (1 mass% or more and 10 mass% or less). More preferably, it is 2-5 mass% (2 mass% or more and 5 mass% or less). When the carbon raw material is less than 1% by mass, when the plate brick comes into contact with the molten steel, it is decarburized in a short time and seizure is likely to occur. As a result, the durability deteriorates, which is not preferable. Moreover, when there are more carbon raw materials than 10 mass%, the decarburization layer produced by reaction with molten steel becomes very porous. As a result, it is not preferred because it is easily worn by the passing molten steel.

  In addition to the carbon compounded as a raw material, the plate brick contains, as a carbon component, residual carbon produced from an organic binder described later that is blended during kneading, and pitch or tar impregnated after firing. Here, the carbon raw material means carbon to be blended as a raw material, and does not include residual carbon generated from an organic binder and carbon components resulting from pitch or tar impregnated after firing. Therefore, the carbon amount of the plate brick subjected to the caulking treatment after impregnation is about 2 to 3% by mass more than the added amount of the carbon raw material.

  Examples of the metal additive include silicon (hereinafter referred to as Si), aluminum (hereinafter referred to as Al), aluminum-silicon alloy (hereinafter referred to as Al-Si alloy), and aluminum-magnesium alloy (which are generally used). Al-Mg alloy) can be used. Further, the present invention is not limited to these, and any other metal species can be used as long as it is a metal species that generates carbide or nitride during firing. In addition, a plurality of types of metal additives can be used in combination.

  It is preferable that content of a metal additive is 1-8 mass% (1 mass% or more and 8 mass% or less). More preferably, it is 2-6 mass% (2 mass% or more and 6 mass% or less). When the total amount of the metal additive is less than 1% by mass, it is not preferable because sufficient strength cannot be imparted to the plate brick. Further, when the total amount of the metal additives is more than 8% by mass, the plate brick has an excessive elastic modulus, which is not preferable because the spalling resistance is lowered.

  In the present invention, the formation of nitride from a metal additive blended as a raw material plays an important role. In this respect, it is preferable to use Al or an Al alloy (Al—Si alloy, Al—Mg alloy, etc.) rather than Si. When Al or an Al-based alloy is used as the metal additive, it is particularly preferably 1 to 4% by mass (1 to 4% by mass) from the viewpoint of strength characteristics.

In addition to metal additives, carbides such as SiC and B ₄ C, and nitrides such as Si ₃ N ₄ and AlN can also be added. However, since these carbides and nitrides have different effects from the fact that metal additives produce carbides and nitrides by reaction with molten steel, these carbides and nitrides are not included in the above metal additives. Absent.

  In addition to the above, the same refractory raw materials, organic binders, additives, and the like to be mixed can be used as in the conventional coke-packing reduction firing method. As the refractory raw material, for example, an aggregate such as alumina, alumina-zirconia, magnesia or the like can be used. As the organic binder, for example, a thermosetting resol type or a thermoplastic novolac type phenol resin can be used. In addition, in this invention, since the addition amount of a binder is prescribed | regulated with an external coating with respect to the other raw materials except a binder as mentioned later, a binder shall not be included in a raw material for convenience.

  The manufacturing method of the plate brick using the above raw materials is the same as that of the conventional coke-packing reduction baking method except for the baking step. That is, a carbon raw material and a metal additive are blended with a refractory raw material such as alumina or alumina-zirconia, an organic binder such as a phenol resin is added, and the mixture is kneaded with a mixer. The kneaded raw material is press-molded into a plate shape and then dried in a temperature atmosphere of 200 to 300 ° C. Firing is performed after this drying. After calcination, the pores of the plate brick are impregnated with pitch or tar. After impregnation, a coking process is performed.

  No special equipment is required in the mixer for kneading, the press for molding, the impregnation apparatus for tar or pitch used in these manufacturing processes, and the conventional equipment can be used. However, in the firing step of the present invention, the rate of temperature rise tends to be abruptly higher than that of the coke-packing reduction firing method, and thus it is necessary to sufficiently remove volatile components from the organic binder in the drying step.

  Hereinafter, the firing step will be described in detail. In the firing step of the present invention, the plate brick employs a reduction firing method in which the atmosphere in the furnace itself is directly heated as a non-oxidizing atmosphere without being packed with coke breeze.

In this firing step, the nitrogen gas concentration (hereinafter referred to as N ₂ concentration) is 70 to 99% by volume (70% to 99% by volume) and the carbon monoxide gas concentration (hereinafter referred to as CO concentration) is 1 volume. % And the sum of the carbon monoxide gas concentration and the carbon dioxide gas concentration (hereinafter, CO + CO ₂ concentration) is 20% by volume or less, and the oxygen gas concentration (hereinafter, O ₂ concentration) is 0.1% by volume or less, A non-oxidizing gas having a composition having a water vapor concentration (hereinafter, H ₂ O concentration) of 2% by volume or less is blown (introduced) into the furnace.

When the N ₂ concentration is less than 70% by volume, a sufficient amount of nitride is not generated in the plate brick, and therefore, it is not preferable because only characteristics equivalent to those of the conventional coke-packing reduction firing method can be obtained. In order to increase the amount of nitride formed from the metal additive and increase the resistance to molten steel, a N ₂ concentration of 70% by volume or more is required, more preferably 80% by volume or more, and still more preferably 90% by volume or more. It is. On the other hand, when the N ₂ gas concentration exceeds 99% by volume, nitrides are excessively generated and the pore diameter in the plate brick is rapidly reduced. As a result, the impregnation property of tar and pitch is lowered, which is not preferable.

Further, in order to prevent the impregnation of tar and pitch from being reduced due to excessive nitride formation, it is necessary to secure a certain CO partial pressure in a high temperature furnace to prevent excessive nitride formation. Under a high temperature environment, an equilibrium relationship between CO and CO ₂ occurs as described later. Therefore, the atmospheric gas to be blown requires a CO + CO ₂ concentration of 1% by volume or more. More preferably, it is 2% by volume or more. On the other hand, if the CO partial pressure becomes too high in a high-temperature furnace, the formation of nitrides is suppressed, so the CO + CO ₂ concentration needs to be 20% by volume or less. More preferably, it is 10 volume% or less. Further, in order to suppress the excessive formation of nitride, CO needs to be contained at least 1% by volume.

According to the inventors' investigation (see Table 1 described later), even when the O ₂ concentration in the non-oxidizing gas blown into the furnace is 0.1 to 1% by volume, the O ₂ in the high-temperature furnace. The concentration is about 0.001 to 0.01% by volume, and oxidation of the plate brick does not occur. Such in-furnace O ₂ concentration is a region called weak oxidation firing in Patent Documents 1 and 2 described above, and plate bricks having excellent tar or pitch impregnation properties can be obtained. However, if the O ₂ concentration becomes too high, oxynitride is generated more than the nitride from the metal additive, so that sufficient characteristics cannot be obtained in terms of molten steel reactivity. Therefore, the O ₂ concentration of the non-oxidizing gas used in the present invention needs to be 0.1% by volume or less in order to secure the amount of nitride produced. The O ₂ concentration may be zero.

Moreover, when the H ₂ O concentration in the non-oxidizing gas is high, the formation of nitride from the metal additive is suppressed even if the N ₂ concentration is high. Therefore, the H ₂ O concentration needs to be 2% by volume or less. Further, the H ₂ O concentration may be zero.

The method for producing the non-oxidizing gas as described above is not particularly limited. For example, NX gas, DX gas, or a gas supplemented with necessary gas species based on these gases can be used. Here, the DX gas is a gas obtained by incompletely burning a hydrocarbon gas such as propane or butane in the air and removing most of H ₂ O from the gas. Further, NX gas is obtained by removing a small amount of remaining H ₂ O and CO ₂ .

There is a slight difference between the composition of the non-oxidizing gas introduced into the furnace and the atmospheric gas composition in the high-temperature electric furnace. In a non-oxidizing gas containing CO, CO ₂ , O ₂ , and H ₂ O, equilibrium reactions shown in the following formulas (1) and (2) occur between these in a high-temperature electric furnace.

Therefore, the atmospheric gas in the furnace has a lower oxygen concentration than the blown gas composition. For example, in the case of NX gas having a CO concentration of 1.5 vol%, a CO ₂ concentration of 0.05 vol%, and an H ₂ O concentration of <0.1 vol%, the equilibrium oxygen partial pressure is calculated to be 3. At 6 × 10 ⁻²⁴ atm and 1800K, the value is as extremely low as 1.4 × 10 ⁻¹⁰ atm.

On the other hand, gas such as H ₂ O, CO ₂ , CO, CH _{4 and the} like is generated from the organic binder of the plate brick to be fired during the temperature rising process. The atmosphere gas composition changes temporarily. In the plate brick fired depending on the concentration of these generated gases, the amount of AlN produced may change. Therefore, in order to quickly discharge these generated gases to the outside of the furnace, a non-oxidizing gas having the above composition is continuously introduced.

On the other hand, in hydrocarbon gases such as propane and butane and non-oxidizing gases such as DX gas and NX gas that use air as raw materials, some of the raw material hydrocarbon gas remains unreacted and the pyrolysis process The H ₂ gas generated in step 1 and the hydrocarbon gas different from the raw material generated in the combustion process are generated. The amount of these gases, that is, the hydrogen gas concentration and the hydrocarbon gas concentration (hereinafter referred to as H ₂ + hydrocarbon gas concentration) is preferably 10% by volume or less. The presence and concentration of these gases has no significant effect on the properties of the plate brick. However, there is no economic rationality when the volume is 10% by volume or more. Moreover, when producing | generating the above-mentioned non-oxidizing gas without using hydrocarbon gas as a raw material, the H ₂ + hydrocarbon gas concentration may be zero.

  Next, the firing furnace used for the above firing will be described. In the field of industrial heating, furnaces are classified into combustion heating and electric heating depending on the heat source used.

  In the firing method that has been put to practical use with carbon-containing refractories, in the case of combustion heating, as a direct heating method in which the combustion gas directly transfers heat to the material to be heated, the combustion gas is incompletely combusted without being filled with sheath. There is a method of oxidizing and firing. The indirect heating method, in which the combustion gas does not transfer heat directly to the material to be heated, is a method of transferring heat from the combustion gas through a heat resistant steel radiant tube into a non-oxidizing furnace, or a refractory sheath ( Alternatively, there is a method of firing a material to be heated in which coke breeze is packed together in a heat-resistant steel muffle) with a combustion gas in an oxidizing atmosphere. Further, in the case of electric heating, a direct heating method in which an object to be heated is directly energized and heated has not been put into practical use for a carbon-containing refractory. In addition, in the indirect heating method, there are a method of baking the material to be heated (packed with muffle) as in the case of combustion heating, and a method of electric heating while circulating a non-oxidizing gas in the furnace.

  In the present invention, the plate brick is fired in a state where the plate brick is disposed in the above-mentioned non-oxidizing gas atmosphere without being fired with coke breeze. Therefore, a method of using a radiant tube furnace or an electric heating furnace and blowing the above-mentioned non-oxidizing gas into the furnace is suitable for firing. Radiant tube furnaces are more advantageous than electric heating furnaces in terms of fuel costs. However, the firing temperature is limited to about 1000 ° C. at the maximum in terms of the durability of the tube material. Therefore, a hybrid structure in which the low temperature zone is radiant tube heating and the high temperature range is electric heating may be employed.

  A calcination temperature can be 700-1500 degreeC which is the temperature range similar to the conventional coke packing reduction baking method. From the viewpoint of the firing cost and the design of the firing furnace, it is preferably 1300 ° C. or lower. More preferably, it is 1050 degreeC-1250 degreeC.

  The firing time can be shortened because the heat transfer effect is higher than that of the coke-packing reduction firing method, and the firing time only needs to be maintained at the maximum temperature for 2 hours or more. Further, when the temperature is lowered, taking advantage of the fact that oxidation is not performed even in the air at 600 ° C. or less, it is more excellent in terms of productivity to take out the furnace and accelerate cooling. Therefore, it takes about 4 to 12 hours for the plate brick to be inserted into the furnace, fired in a state where the atmosphere is controlled, and taken out of the furnace.

  In addition, since the effect of this invention is acquired by the composition of atmospheric gas, the system of a furnace is not limited. For example, even when nitrogen gas or ammonia gas is blown and adjusted to a predetermined atmospheric gas composition in non-oxidative firing with incomplete combustion gas, the same effect can be obtained. As for the structure of the furnace, there are a continuous type and a batch type in terms of the operation method, and in the case of the continuous type, there are a pusher type, a cart type, a roller hearth type, etc. as a material conveying method. Can be obtained without depending on the structure.

The present invention is also applicable to carbon-containing plate brick materials other than Al ₂ O ₃ —ZrO ₂ —C materials (for example, MgO—C materials and Spinel-C materials for special steel). In addition, in the present invention, the blending and firing conditions were determined with emphasis on impregnation, but plate bricks after firing are also effective in improving the resistance to molten steel due to the formation of nitrides. Therefore, it can be applied to unimpregnated plate bricks.

  Examples and comparative examples are presented below to explain the plate brick of the present invention. In Table 1, plate bricks are produced by changing the composition of the non-oxidizing gas blown during firing in an electric furnace, and the characteristics are evaluated. In Table 2, plate bricks are produced by changing the composition of the plate bricks, and the characteristics are evaluated.

  In Table 1, the composition of the plate bricks shown in Examples 1 to 6 and Comparative Examples 1 to 5 is the same, and the composition is as shown in Example 1 of Table 2. That is, as a refractory raw material, 25% by mass of alumina having a particle size of more than 1 mm and 3 mm or less (indicated in the table as 3-1 mm; the same applies hereinafter), and zirconia mullite having a particle size of more than 1 mm and 3 mm or less. 15% by mass, 15% by mass of alumina zirconia having a particle size of 1 mm or less, and 37% by mass of alumina having a particle size of 1 mm or less are blended. Further, 3% by mass of carbon black having a particle size of 1 μm or less is blended as a carbon raw material. Further, as a metal additive, 1% by mass of Si having a particle size of 200 μm or less and 4% by mass of Al having a particle size of 200 μm or less are blended. In addition, as an organic binder, a phenol resin is blended in an amount of 4% by mass.

In Table 2, the composition of the non-oxidizing gas blown during firing in the electric furnace is the same, and the composition shown in Example 1 of Table 1 is obtained. That is, N ₂ gas is 96.4% by volume, CO ₂ gas is 0.05% by volume, CO gas is 2.0% by volume, O ₂ gas is less than 0.1% by volume, water vapor (hereinafter referred to as H ₂ O gas). ) Is less than 0.1% by volume. When this non-oxidizing gas is introduced into the electric furnace, the oxygen concentration in the furnace is less than 0.001% by volume. In Tables 1 and 2, “-” means that the component is not included.

  The furnace temperature during firing is a maximum of 1300 ° C., and the temperature rise is 500 ° C./hr. The plate brick is taken out of the furnace when the maximum temperature is maintained for 2 hours and the temperature is lowered to 600 ° C. by natural cooling.

  For each of Examples 1 to 13 and Comparative Examples 1 to 10, each of bending strength, kinematic modulus, pitch impregnation weight increase, and molten steel reactivity was evaluated, and the evaluation results for each item are shown in Table 1 and Table 2. Shown in.

  The bending strength was evaluated according to a three-point bending test defined in JIS R 2213 by processing a sample without impregnating the pitch. From the past results, the plate brick after firing can be used if the bending strength is 15 MPa or more, and the bending strength is more preferably 24 to 32 MPa.

  The dynamic modulus of elasticity W. Evaluation was performed by a grindsonic method using a grindsonic MK-5i manufactured by LEMMENS. From the past results, when the dynamic elastic modulus of the plate brick after firing exceeds 90 GPa, the spalling resistance is lowered, so that it can be used if it is 90 GPa or less. Moreover, it is a more preferable quality that a dynamic elastic modulus is 40-65 GPa.

The increase in pitch impregnation weight was evaluated by impregnating the low viscosity pitch in an actual production line at 200 ° C. for 2 hours under pressure (pressure 15 kg / cm ² ), and evaluating the impregnation rate from the change in weight before and after the impregnation. From the past results, it is satisfactory if the increase in pitch impregnation weight of the plate brick after firing is 3% or more.

  The resistance to molten steel was evaluated by a reaction test with molten steel using a Tamman furnace. In the reaction test, a plate brick is processed into a 6 mm × 6 mm × 70 mm sample piece, and about 20 mm at the tip is immersed in molten steel at 1560 ° C. for 1 hour in a Tamman furnace, and then pulled up and cooled. And the sample piece after a test was cut | disconnected in parallel with the long side direction, and the thickness of the decarburization layer and the molten steel infiltration layer was measured by microscope observation. Since the reaction with molten steel occurs after the effects of impregnated pitch and tar disappear, sample pieces were prepared from unimpregnated plate bricks. “X” indicates decarburization that is practically unacceptable because the thickness of the decarburized layer is 150 μm or more. “Δ” indicates that the thickness of the decarburized layer is 110 μm or more and less than 150 μm, which is practically acceptable decarburization. “◯” indicates that the thickness of the decarburized layer is 80 μm or more and less than 110 μm, and it has better molten steel reactivity than “Δ”. “◎” indicates that the thickness of the decarburized layer is less than 80 μm, and has better molten steel reactivity than “◯”.

As shown in Table 1, in Examples 1 to 6 and Comparative Examples 1 to 5, NX gas, DX gas, nitrogen gas, and LPG incomplete combustion gas are used as the non-oxidizing gas. DX gas is a gas obtained by removing most of H ₂ O gas from LPG incomplete combustion gas. The NX gas is a gas obtained by further removing a small amount of H ₂ O gas and CO ₂ gas remaining from the DX gas. In Examples 1 to 6 and Comparative Examples 1 to 3, firing in a non-oxidizing atmosphere is performed by blowing a non-oxidizing gas manufactured using a gas generator into an electric furnace. In these cases, the composition of the non-oxidizing gas is the gas composition at the time of blowing (before introduction into the furnace). In Comparative Examples 4 and 5, the LPG gas is incompletely burned and the inside of the furnace is fired in a non-oxidizing atmosphere.

Examples 1, 2, and 6 are non-oxidizing gases based on NX gas, and have different CO concentrations. Further, the N ₂ concentration differs depending on the change in the CO concentration. Examples 3 to 5 and Comparative Examples 2 and 3 are non-oxidizing gases based on DX gas, and differ in CO concentration and CO ₂ concentration. Further, the N ₂ concentration or the H ₂ O concentration differs depending on the change in the CO concentration and the CO ₂ concentration. Comparative Examples 4 and 5 are non-oxidizing gases based on LPG incomplete combustion gas, and the O ₂ concentration is mainly different by changing the ratio of the fuel gas and the combustion support gas. Further, the H ₂ O concentration differs depending on the change in the O ₂ concentration. Comparative Example 1 is a non-oxidizing gas based on pure nitrogen gas.

Regarding the O ₂ concentration in the furnace, an oxygen sensor was provided in the furnace to monitor the oxygen concentration during the firing process. In the case of the LPG incomplete combustion gas of Comparative Example 4, the O ₂ concentration was temporarily 0.012% by volume, but the O ₂ concentrations of Examples 1 to 6 and Comparative Examples 1 to 3 and 5 were 0.00. It was less than 001 volume%. In terms of appearance, no oxidation was observed, and it was good.

As can be understood from Table 1, each of Examples 1 to 6 and Comparative Examples 1 to 5 has a bending strength sufficient to withstand mechanical restraint force. When the fracture surface after the bending test was observed with EPMA (Electron Probe Micro Analyzer), a large amount of whiskers could be confirmed particularly in Comparative Example 1 in which N ₂ gas was blown and fired. As disclosed in Patent Document 3, it is considered that when the N ₂ concentration in the atmospheric gas is increased, the formation of AlN whiskers is promoted and the structure is strengthened.

  Moreover, as can be understood from Table 1, each of Examples 1 to 6 and Comparative Examples 1 to 5 has a dynamic elastic modulus that causes no problem in actual use.

Regarding the pitch impregnation property, in Comparative Example 4, a sufficient impregnation rate was obtained even under a lower pressure condition of 5 kg / cm ² , and the impregnation property was very good. In Comparative Example 4, the in-furnace oxygen concentration temporarily increased to 0.012% by volume at the time of firing, and disclosed in Patent Document 1 and Patent Document 2, "impregnation improves when fired in a weakly oxidizing atmosphere". It is thought that the action effect appeared. In Examples 1 to 6 and Comparative Examples 2, 3, and 5, a sufficient impregnation rate is obtained when high pressure impregnation of 15 kg / cm ² is performed. In Comparative Example 1 using N ₂ gas, the impregnation rate is about 70 to 80% of other samples even under high temperature impregnation conditions, and the weight increase rate before and after the impregnation is 3% or less. This is thought to be because the pore size is reduced by the generation of a large amount of whiskers and impregnation is inhibited.

Solvent steel reactivity, Comparative Example As can be seen from Table 2, Comparative Example 1, _{N 2} concentration also CO + CO ₂ concentration was 70 vol% or more _{N 2} concentration exceeding 99% by volume of more than 20 vol% 2, Comparative Example 3 in which N ₂ concentration is less than 70% by volume, Comparative Examples 4 and 5 in which H ₂ O concentration exceeds 2% by volume (particularly, in Comparative Example 4, O ₂ concentration exceeds 0.1% by volume) ), The thickness of the decarburized layer is thick or the molten steel is infiltrated, which is not suitable for practical use. In Examples 1 to 6, all good results are obtained. In Example 1-6, the tendency of decarburized layer thickness decreases can be confirmed that occurs in the reaction with the molten steel as N ₂ gas concentration at the time of firing increases.

  On the other hand, as shown in Table 2, in Examples 1, 7 to 12 and Comparative Examples 6 to 10, the refractory raw material is alumina having a particle size of more than 1 mm and 3 mm or less, and zirconia having a particle size of more than 1 mm and 3 mm or less. The blending amounts of mullite, alumina zirconia having a particle size of 1 mm or less, and the organic binder are all the same. In Examples 7 and 8, and Comparative Examples 6 and 7, the amount of carbon black is different from that in Example 1. Further, the amount of alumina having a particle size of 1 mm or less varies depending on the change in the amount of carbon black. In Examples 9 to 12 and Comparative Examples 8 to 10, the type and amount of the metal additive are different from those in Example 1. Moreover, the compounding quantity of the alumina whose particle size is 1 mm or less changes according to the change of the compounding quantity of a metal additive. In Example 13, magnesia having a particle size exceeding 1 mm and 3 mm or less and magnesia having a particle size of 1 mm or less are used as the refractory raw material.

  In any of the firings of Examples 7 to 13 and Comparative Examples 6 to 10, the oxygen concentration in the furnace was less than 0.001% by volume. there were.

  As can be understood from Table 2, in Comparative Example 6 in which the carbon raw material was used in an amount of 0.5% by mass, infiltration of molten steel occurred due to insufficient carbon in the evaluation items of the molten steel reactivity. Moreover, in the comparative example 7 which uses 12 mass% of carbon raw materials, the decarburized layer is very porous and is as thick as 170 μm. On the other hand, in Example 7 using 1.5% by mass of the carbon raw material, the thickness of the decarburized layer was 90 μm, and in Example 8 using 7% by mass of the carbon raw material, the thickness of the decarburized layer was 120 μm, Good results have been obtained.

  Moreover, in the comparative example 8 which mix | blended 0.5 mass% of Al, bending strength is inadequate. In Comparative Example 9 in which 6% by mass of Al was blended and in Comparative Example 10 in which a total of 10% by mass of Al was added and 4% by mass of Al and 6% by mass of Si, the kinematic elastic modulus after firing was too high. Inadequate spalling resistance. In addition, since the formation of nitride is excessive, the impregnation property is poor. In Example 9 in which metal additives of a total of 1.5% by mass of 1% by mass of Al and 0.5% by mass of Si were blended, the bending strength was lower than that of Example 1, and 3% by mass of Al, In Example 10 in which 7% by mass of metal additives including 4% by mass of metal Si were blended, the elastic modulus was higher than that in Example 1, but it was at a level causing no practical problems. In Example 11 using an Al—Si alloy instead of Al, and in Example 12 using Al—Si alloy in addition to Al and Si, the total amount of which was 6% by mass, all had bending strength, It was good in terms of impregnation and molten steel reactivity. Also in Example 13, good bending strength, impregnation properties, and molten steel reactivity were obtained.

  In addition, the plate brick manufactured on condition of the above-mentioned Example 1, 3, 7, 9 and the comparative example 1 was used for real machine use. Specifically, it was used as a 300 ton ladle SV (Slide Valve) plate, and the average life after using 15 sets was determined. As a result, the average life of the plate brick according to Comparative Example 1 was 6.2 times, whereas the average life of the plate brick according to Example 1 was 9.1 times, and the plate brick according to Example 3 was 8.5 times. The plate brick according to 8.3 was 8.3 times, and the plate brick according to Example 9 was 7.9 times.

  As described above, according to each embodiment of the present invention, it is possible to generate an appropriate amount of nitride that does not easily react with molten steel from a metal additive, and it is possible to sufficiently ensure impregnation of tar or pitch. It is possible to obtain plate bricks having excellent durability.

  INDUSTRIAL APPLICABILITY The present invention has a short firing time and can significantly improve the durability compared to the prior art, and is useful as a plate brick for a slide plate device and a method for manufacturing the same.

Claims (3)

Forming a molded body containing 1 to 10% by mass of a carbon raw material and 1 to 8% by mass of a metal additive;
The molded body has a nitrogen gas concentration of 70 to 99% by volume, a carbon monoxide gas concentration of 1% by volume or more, and a total of the carbon monoxide gas concentration and the carbon dioxide gas concentration of 20% by volume or less, A step of blowing a non-oxidizing gas having an oxygen gas concentration of 0.1% by volume or less and a water vapor concentration of 2% by volume or less into the furnace, and firing in a state of being in direct contact with the non-oxidizing gas in the furnace; ,
Impregnation into tar or pitch after firing,
A method for manufacturing a plate brick for a slide plate device.   The manufacturing method of the plate brick for slide plate apparatuses of Claim 1 whose sum total of hydrogen gas concentration and hydrocarbon gas concentration contained in the said non-oxidizing gas is 10 volume% or less.   The manufacturing method of the plate brick for slide plate apparatuses of Claim 1 or Claim 2 which contains 1-4 mass% of aluminum or an aluminum containing alloy as said metal additive.