JP2005231953A - Graphite-containing brick - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a graphite-containing brick exhibiting durability more than that of a conventional one even when used as brick for converter such as the furnace bottom or the tuyere peripheral part of a bottom blown converter and having excellent spalling resistance. <P>SOLUTION: The graphite-containing brick is structured by forming a kneaded material containing a refractory main raw material, 3-30 mass% graphite, a binder and 0.1-2.0 mass% carbon fiber assembly in which the bonding of the fiber chopped into 3-30 mm length in the axial direction partially remain and is partially released. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention contains graphite with excellent spall resistance, which can exhibit durability beyond conventional levels even when used as a brick for converters at the bottom of bottom blown converters and around tuyere of bottom blown converters. Regarding bricks.

  Graphite-containing bricks have excellent slag penetration resistance, low thermal conductivity, and low thermal expansion. Therefore, blast furnaces, kneading cars, hot metal ladles, converters, and RH degassing equipment are used in the steelmaking process for manufacturing steel. It is used for continuous casting nozzles. In particular, the bottom of the bottom-blowing converter and the area around the tuyere of the bottom-blowing converter are at high temperatures, have a large temperature gradient, and are subjected to severe thermal conditions that are frequently exposed to thermal shock. Under the conditions of use, a graphite-containing brick having excellent spall resistance is required.

  In order to improve the spall resistance of the graphite-containing brick, it is effective to increase the mechanical strength of the brick and lower the elastic modulus. Particularly for applications such as the bottom of a bottom-blown converter and the vicinity of the tuyere, graphite-containing bricks with a low elastic modulus while maintaining strength are considered preferable.

  For example, as a means of lowering the elastic modulus, it is known to add thin graphite that is thinner than scaly graphite instead of commonly used scaly graphite. There is a track record in which the graphite-containing bricks that have been used have been used as furnace bricks for bottom blown converters and as bricks for converters around the tuyere of bottom blown converters. However, even when using graphite-containing bricks with the addition of thin graphite, there is a limit to its durability improvement effect, and as a brick for converters at the bottom of bottom blown converters and around the tuyere of bottom blown converters Has insufficient durability.

On the other hand, as means for increasing the compressive strength, it is known (Patent Document 1) to add a predetermined amount of carbon fiber having an axial length of about 0.1 to 5 mm, and further coated in advance with an organic resin. It is also disclosed that carbon fibers having an axial length of 0.5 to 5 mm are used to strengthen the bond with the matrix of the main raw material (Patent Document 2). FIG. 5 is a sketch of a photomicrograph showing the carbon fibers 60 dispersed in the brick.
Japanese Patent Laid-Open No. 56-140080 Japanese Patent Laid-Open No. 2-141452

  However, the graphite-containing bricks described in Patent Documents 1 and 2 are in a state where a large number of short carbon fibers are uniformly dispersed in the matrix of the main raw material, and even if the compressive strength can be increased, the elastic modulus It was difficult to make bricks having a high compressive strength / elastic modulus by lowering the value. For this reason, when applying a graphite-containing brick in which a large number of short carbon fibers are uniformly dispersed in the matrix of the main raw material as a brick for a converter at the bottom of a bottom-blown converter or around the tuyere of a bottom-blown converter, The durability was insufficient.

  The present invention solves the above-mentioned problems of the prior art, and even when used as a brick for a converter at the bottom of a bottom blown converter or the tuyere of a bottom blown converter, it exhibits higher durability than before. An object of the present invention is to provide a graphite-containing brick having excellent spall resistance.

  In the present invention, the bond of the refractory main raw material, graphite: 3 to 30% by mass, the binder, and the chopped fiber carbon fiber having an axial length of 3 to 30 mm partially remains and is partially released. It is a graphite-containing brick formed by molding a kneaded product containing an aggregate of carbon fibers in a state of 0.1 to 2.0% by mass. In this case, it is preferable to form a kneaded product to which xylenol resin or cresol resin is added as the binder.

  Since the graphite-containing brick of the present invention is excellent in spall resistance, even when used as a converter brick in the bottom of a bottom-blown converter or in the vicinity of a tuyere, it can exhibit durability beyond conventional ones. .

  First, the aggregate | assembly of the carbon fiber contained in the graphite containing brick of this invention is demonstrated using figures.

  FIG. 1-1 is a schematic view of the chopped fiber carbon fiber 1, and FIG. 1-2 is a cross-sectional view illustrating a bonded state of the chopped fiber carbon fiber 1. In FIG. 1-1, L represents the axial length of the chopped fiber carbon fiber 1.

  The chopped fiber carbon fiber 1 is formed by bundling 1000 to tens of thousands of long carbon fibers having a diameter of 2 to 50 μm, and binding a long bundle of carbon fibers with a resin called a sizing agent 3 in the longitudinal direction. It was cut with Thus, the chopped fiber carbon fiber 1 is composed of a large number of short carbon fibers 2 and is bonded to each other by the sizing agent 3 over the length direction. In this invention, the axial direction length L of the chopped fiber carbon fiber 1 shall be 3-30 mm according to a use.

  Conventionally, when manufacturing a brick to which carbon fiber is added, the chopped fiber carbon fiber 1 having an axial length L of 5 mm or less is used, and the sizing agent 3 is washed and removed in advance, or is added to the refractory raw material. After adding the chopped fiber carbon fiber 1 to the refractory raw material as it is, a sufficient kneading time is taken to completely break the bonds of the chopped fiber carbon fiber 1 so that the short carbon fibers 2 are uniformly dispersed in the kneaded product. It was molded from.

  On the other hand, in this invention, the coupling | bonding of the chopped fiber carbon fiber 1 whose axial direction length is 3-30 mm remains partially, and the aggregate | assembly 4 of the carbon fiber of the state released | released partially is disperse | distributed uniformly. The kneaded product is molded into a graphite-containing brick. For example, when the graphite-containing brick of the present invention is observed in a cross section perpendicular to the pressing direction in the brick forming step, the aggregate 4 of carbon fibers 2 having a form as shown in FIGS. 2-1 to 2-3. Is observed. The aggregate 4 of the carbon fibers 2 in such a form can be obtained by stirring the chopped fiber carbon fiber 1 alone with a kneader equipped with a stirrer before mixing with the refractory material raw material. When kneading a kneaded material with a material raw material, it can also be obtained by stirring with a kneader equipped with a stirrer.

  When stirring in the kneader is performed for a long time, the coupling of the chopped fiber carbon fiber 1 is completely released, so the stirring time is adjusted. The appropriate stirring time varies depending on the type and amount of the sizing agent 3 of the chopped fiber carbon fiber 1 or the type of the kneading machine, so that the optimal stirring time for obtaining the carbon fiber aggregate 4 in a desired form can be obtained. Check in advance.

  The operation of the carbon fiber assembly 4 will be described.

  The graphite-containing brick is formed by molding a kneaded material including a main raw material, a binder for a refractory material such as graphite and a resin, and an aggregate 4 of carbon fibers, and then curing the resin (referred to as a curing process), or Furthermore, it is manufactured by firing at a higher temperature. At that time, the single carbon fiber 2 constituting the carbon fiber aggregate 4 is arranged in a plane perpendicular to the pressing direction 41 shown in FIG. 3 in the brick forming step. Therefore, when the brick is observed in a plane perpendicular to the pressing direction 41, the aggregate 4 of the carbon fibers 2 in a pine needle shape or fluffy shape as shown in FIGS. 2-1 to 2-3. Can be confirmed to be dispersed throughout the brick. A large number of carbon fibers 2 constituting this one aggregate 4 are spread about 1.1 L to 3 L with respect to the axial length L of the chopped fiber carbon fiber 1, so that it is firmly in the refractory material. The bite and low elastic modulus can be achieved, and the compression strength can be improved.

  In kneading, it is important for stabilizing the spall resistance to uniformly disperse the carbon fiber aggregate 4 in a state where the bonds of the chopped fiber carbon fiber 1 partially remain and are partially released. It is.

  In the present invention, the reason for limiting the axial length L of the chopped fiber carbon fiber 1 to 3 to 30 mm is as follows.

  When cutting the bundle of carbon fibers, if the axial cut length is less than 3 mm, the carbon fiber aggregate 4 as shown in FIGS. 2-1 to 2-3 cannot be obtained. For this reason, the axial length L of the chopped fiber carbon fiber 1 is limited to 3 mm. On the other hand, when the bundle of carbon fibers is cut, if the axial cut length exceeds 30 mm, the resulting carbon fiber aggregate 4 is too bulky. As a result, the spring back at the time of brick molding becomes large, and it becomes difficult to mold the brick into a predetermined shape. For this reason, the axial length L of the chopped fiber carbon fiber 1 is limited to 30 mm.

  Next, the reason for limiting the content of the carbon fiber aggregate 4 to 0.1 to 2.0 mass% will be described.

  The greater the content of the carbon fiber aggregate 4, the greater the effect of lowering the elastic modulus. However, when the content exceeds 2.0 mass%, the number of the carbon fiber aggregates 4 increases and the bulkiness increases. As a result, the spring back at the time of brick molding becomes large, and it becomes difficult to mold the brick into a predetermined shape. On the other hand, when the content of the carbon fiber aggregate 4 is less than 0.1% by mass, the effect of lowering the elastic modulus of the obtained graphite-containing brick becomes insufficient. For this reason, content of the aggregate 4 of carbon fiber is limited to 0.1-2.0 mass%.

  The content of the carbon fiber aggregate 4 having an axial length L of 3 to 30 mm is 0.1 to 2.0% by mass. It does not detract from the spirit of the invention. For example, a short carbon fiber whose axial length L is less than 3 mm or a chopped fiber carbon fiber 1 whose axial length L exceeds 30 mm remains partially bonded, and a carbon fiber aggregate in a partially broken state However, even if the carbon fiber contained in the graphite-containing refractory brick is contained in an amount of about 10% by mass or less, the effect of the present invention is not impaired.

  The reason for limiting the graphite content to 3 to 30% by mass is as follows.

  The spall resistance of bricks containing graphite is strongly governed by the amount of graphite. When the graphite content is less than 3% by mass, the effect of improving the spall resistance is not observed compared to bricks not containing graphite. When the content exceeds 30% by mass, not only the effect of improving the spall resistance is saturated, but also when the brick is used, the deterioration of the graphite-containing brick becomes remarkable due to oxidation of the graphite. For this reason, graphite content is limited to 3-30 mass%.

As the graphite, known graphite can be used as brick graphite such as scale-like graphite, thin-walled graphite, artificial graphite, and earth-like graphite. In addition, carbons such as carbon black (different from graphite) can be added as appropriate. In addition, the graphite-containing brick includes an antioxidant for preventing oxidation of graphite at the time of use depending on the application place, one or more metals selected from Al, Mg, Si, etc., or Al-Mg. Further, an alloy such as Al—Si or a carbide such as B ₄ C can be added to further increase the compressive strength.

  In the present invention, a binder can be added and kneaded and molded.

  In this case, the amount of binder added is preferably 2 to 8% by mass, and it is preferable to add xylenol resin or cresol resin as the binder. As a binder for graphite-containing bricks, phenol resin or tar pitch is usually used, but when xylenol resin or cresol resin is added compared to the case where these binders are added, compression of graphite-containing bricks is performed. The strength becomes higher, and as a result, a graphite-containing brick having a high compressive strength / elastic modulus value can be obtained.

  This is because when the xylenol resin or the cresol resin is used, the molecular structure is close to a straight chain and the wettability with the carbon fiber is good. However, as a binder for the graphite-containing brick, a xylenol resin or a cresol resin and a phenol resin can be used in combination.

  The main raw material having fire resistance may be one or more selected from oxides such as alumina, silica, magnesia, calcia, zirconia, and chromia, and may be selected from carbides such as silicon carbide. One kind or two or more kinds can also be used. Alternatively, a mixture of one or more selected from oxides and one or more selected from carbides can also be used. In addition, one or more selected from nitrides can be used as the main raw material for the graphite-containing brick. These raw materials include natural minerals, electrofused products, fired products, calcined products, and the like, and those having a particle diameter of 0.001 to 10 mm are suitably used as the main raw material for graphite-containing bricks.

  The graphite-containing brick of the present invention is, for example, added with the main raw material, graphite, and a binder, kneaded, added with chopped fiber carbon fiber 1 at a time before the completion of the kneading and further kneaded, and aggregate 4 of carbon fibers. And then molded into a predetermined shape, the resin can be cured (referred to as cure treatment), or fired at a higher temperature.

  MgO having a particle diameter of 3 mm or less having passed through a 3 mm sieve and graphite (scale-like graphite: thin-walled scale-like graphite = 1: 1) were weighed and then blended, and the resin of the type shown in Table 1 was used as a binder. Mass% was added and kneaded. The kneaded product was molded at a pressure of 147 MPa and then subjected to a curing process (called a curing process) in which the resin was cured at 180 ° C. for 3 hours. In addition, to the kneaded material, chopped fiber carbon fiber was added within the range of the present invention at the time 10 seconds before the end of kneading, and as shown in Table 1, graphite-containing bricks of Invention Examples 1 to 10 were obtained.

  In the case of Conventional Example 1, carbon fiber is not added, and other than that, graphite containing brick is made in the same manner as the invention example, and in the case of Comparative Examples 1 to 3, chopped fiber carbon fiber outside the scope of the present invention. 1 was added, and a graphite-containing brick was obtained in the same manner as in the inventive examples.

  A plurality of cubes each having a side length a of 40 mm are cut out from the obtained parallel brick 40 having the shape shown in FIG. 3 to obtain a test piece 50 after the curing treatment, and the room temperature of the test piece 50 after the curing treatment is obtained. The compressive strength and elastic modulus of each were examined, and the mechanical properties of the graphite-containing brick after 180 ° C. curing treatment were determined. At that time, the porosity of the graphite-containing brick after the 180 ° C. curing treatment was also examined. The porosity of the graphite-containing brick after the 180 ° C. curing treatment was in the range of 6 ± 1%.

  In addition, the graphite-containing bricks after the 180 ° C curing treatment were subjected to a firing treatment that was held in a coke breeze at 1500 ° C for 3 hours and cooled, and a plurality of cubes having a side length a of 40 mm were cut out from the parallel brick 40 obtained by cooling. Thus, the test piece 50 after firing at 1500 ° C. was examined for compressive strength and elastic modulus at room temperature, and the mechanical properties of the graphite-containing brick after firing at 1500 ° C. were determined.

  In addition, the test which investigates the compressive strength and elastic modulus in normal temperature respectively is based on JIS R 2206 and JIS R 1602, and it arrange | positions so that the compression direction 51 in the test piece 50 shown in FIG. I went there. However, the evaluation of the spall resistance of the graphite-containing brick can be made lower than that of the conventional example 1 and the compressive strength / elastic modulus is higher than that of the conventional example 1. Excellent). The parallel brick 40 has a thickness H = 65 mm, a width W = 114 mm, and a length S = 230 mm.

  From the results shown in Table 1, in the case of Invention Examples 1 to 10, both the mechanical properties of the graphite-containing brick after 180 ° C. curing treatment and the mechanical properties of the graphite-containing brick after firing at 1500 ° C. are compared with those of Conventional Example 1. It can be seen that the elastic modulus is low and the compressive strength / elastic modulus is high. As for the binder, in the case of Invention Example 3 using a cresol resin and Invention Example 6 using a xylenol resin, compared with Invention Example 5 using a phenol resin, the mechanical strength of the graphite-containing brick after 180 ° C. curing treatment The compressive strength is high in both the properties and the mechanical properties of the graphite-containing brick after firing at 1500 ° C.

  In the case of Comparative Example 1, the compressive strength is higher than that of Conventional Example 1, but the elastic modulus is high, and the value of compressive strength / elastic modulus is not as high as that of Invention Examples 1-10. When this brick was observed from the pressurizing direction at the time of molding, carbon fibers having an axial length of 1 mm or less were linearly bundled and dispersed. In addition, in the case of Comparative Examples 2 and 3 in which the chopped fiber carbon fiber 1 outside the scope of the present invention was added, the spring back after forming into a parallel shape was large, and consequently it could not be formed into a parallel shape. It was.

1 is a schematic view of chopped fiber carbon fiber 1. FIG. It is sectional drawing explaining the coupling | bonding state of the chopped fiber carbon fiber 1. FIG. 1 is a schematic cross-sectional view of an assembly 4 of carbon fibers. 1 is a schematic cross-sectional view of an assembly 4 of carbon fibers. 1 is a schematic cross-sectional view of an assembly 4 of carbon fibers. It is the schematic which shows the pressurization direction 41 at the time of shape | molding the parallel brick 40. FIG. FIG. 3 is a schematic view showing a compression direction 51 in a test piece 50. It is a sketch figure of the microscope picture for demonstrating the carbon fiber 60. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Chopped fiber carbon fiber 2 Carbon fiber L Axial length of chopped fiber carbon fiber 1 3 Sizing agent 4 Carbon fiber aggregate 40 Parallel brick 41 Pressing direction at the time of brick molding 50 Test piece 51 Compression direction 60 Carbon fiber

Claims (2)

  Bonding of refractory main raw material, graphite: 3 to 30% by mass, binder, and chopped fiber carbon fiber having an axial length of 3 to 30 mm partially remains and is partially released. A graphite-containing brick formed by molding a kneaded product containing carbon fiber aggregates: 0.1 to 2.0% by mass.   The graphite-containing brick according to claim 1, wherein a kneaded product to which a xylenol resin or a cresol resin is added as the binder is formed.

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