JP5573535B2 - MgO-C refractories - Google Patents

Description

  The present invention relates to an MgO-C refractory, and particularly to an MgO-C refractory used in a refining furnace or the like in a steelmaking process.

  Conventionally, in an RH (Ruhrstahl-Hausen) vacuum degassing apparatus in a container for containing various molten metals and a secondary refining facility in a steelmaking process, the occurrence of erosion and wear in a high-temperature vacuum atmosphere is reduced. As a refractory lining capable of obtaining durability, MgO-C refractories (magnesia carbon bricks) are used. Here, the RH vacuum degassing apparatus is an apparatus that performs vacuum degassing treatment of molten steel, and is an apparatus suitable for a wide range of treatment including vacuum decarburization and deoxidation of molten steel. This equipment is suitable for vacuum processing of molten steel in a large amount. The MgO-C refractory is subjected to vacuum degassing treatment by passing molten steel through the RH vacuum degassing apparatus to a high temperature atmosphere and exposing the molten steel surface to a vacuum atmosphere. Used for lower tanks.

On the other hand, with the rapid progress of steelmaking technology, especially steel cleaning technology, the operating temperature of RH vacuum degassing equipment becomes high in response to special treatment (degassing, introduction of alloy), and the use conditions are severe. It is becoming. For this reason, in the MgO-C type refractory used conventionally, the problem that sufficient durability cannot be obtained in points, such as heat resistance, has become remarkable. That is, MgO and C cause a reaction of the following formula {MgO + C → Mg + CO} under high temperature and reduced pressure, and Mg gas and CO gas on the right side of the previous formula flow out from the refractory. For this reason, a large amount of Mg and C is consumed from the refractory, and the structure deteriorates, and there is a big problem that drop damage or peeling damage occurs. In addition, when performing degassing under high temperature and reduced pressure, slag (oxide) such as CaO, SiO ₂ , MgO, Al ₂ O ₃ , FeO is generated on the upper layer (supernatant) side of the molten steel in the reduced pressure direction, There is a problem that the refractory material is eroded by the contact of the slag.

As a technique for suppressing wear due to the MgO-C reaction under high-temperature operation as described above, various proposals have been made from various directions. For example, the technique includes an MgO raw material and a C raw material of less than 1 to 5% by weight. 100% by weight of refractory raw material, pitch and / or binder containing pitch: 0.1 to 5% by weight, and content of oxidizable additive such as metal is 0.1%. There has been proposed a refractory that employs a composition of ˜1.5% by weight and a boride content of 0.5% by weight or less on an external basis (see, for example, Patent Document 1). According to Patent Document 1, it is described that oxidative damage is prevented from occurring in a refractory, and that excellent wear resistance and slag erosion resistance are obtained.
However, in the technique described in Patent Document 1, the above reaction due to contact between MgO and C is unavoidable, and there still remains a problem that refractory dropout damage, peeling damage, slag erosion, etc. occur under high temperature and reduced pressure. .

As another means for suppressing wear due to the MgO—C reaction, a refractory having a structure in which CaO is added to an MgO-based raw material has been proposed. CaO generates a reaction such as the following formula {CaO + 3C → CaC ₂ + CO} in a high-temperature vacuum atmosphere, thereby generating CaC ₂ having an action of suppressing tissue deterioration by maintaining a skeleton as a refractory. . The formation contained inevitably during MgO clinker, and SiO ₂ having an effect of promoting the MgO-C reaction, that is the CaO _reacts, the 2CaO · SiO 2, 3CaO · SiO ₂ such as high-melting compound of It is considered that the wear can be reduced.
However, while CaO has excellent thermal and chemical properties at high temperatures, it is so-called that it causes pulverization and collapse near normal temperature due to a reaction of the following formula {CaO + H ₂ O → Ca (OH) ₂ }. The disadvantage is that digestion occurs. For this reason, when a CaO-containing raw material comes into contact with H ₂ O during the process of manufacturing a refractory such as a brick or the like, a crack or an expansion pulverization phenomenon occurs. May lead to an increase.

  In order to solve the problem when adding CaO to MgO as described above, in a MgO-CaO-based refractory raw material containing 98 wt% or more of CaO and MgO in total, and containing 5 to 70 wt% of CaO component, A refractory having a structure using MgO—CaO-based clinker in which CaO on the surface of raw material particles is covered with a coating of calcium carbonate having a thickness of 0.1 to 5 μm and the loss on ignition value is 1.5% or less is proposed. (For example, refer to Patent Document 2). According to Patent Document 1, it is said that a refractory with significantly superior digestion resistance can be provided by using a raw material whose moisture does not act on CaO.

  However, the technique described in Patent Document 2 can suppress the digestion phenomenon associated with the reaction between CaO and moisture, but cannot prevent tissue deterioration caused by the reaction between MgO and C under high temperature and reduced pressure. Similarly, there were major problems such as dropout damage, peeling damage, and slag erosion.

Japanese Patent No. 3766137 JP 05-24911 A

  The present invention has been made in view of the above problems, and suppresses deterioration of the structure due to the reaction of MgO and C even in a high-temperature and reduced-pressure atmosphere, resulting in dropout damage, peeling damage, slag erosion, and the like. The object of the present invention is to provide a MgO-C refractory that has high durability and is excellent in corrosion resistance and digestion resistance.

The inventors of the present invention have intensively studied to solve the above problems, and in the refractory fine powder contained in the matrix constituting the MgO-C refractory, the aggregate made of MgO is covered with a coating film. It has been found that by adopting a configuration in which CaO fine powder is adhered while covering, it is possible to effectively prevent a reaction between a carbon component such as graphite and MgO contained in the matrix. As a result, it was found that the structure does not deteriorate even when used in a high-temperature and reduced-pressure atmosphere, and it is possible to prevent the occurrence of dropout damage, peeling damage, slag erosion, etc., and the present invention has been completed. .
That is, the gist of the present invention is as follows.

[1] An MgO-C refractory comprising at least a refractory material fine powder, a graphite (C), a matrix containing a binder composed of a carbon-based material, and a refractory coarse powder, refractory fines are contained in the aggregate made of MgO, provided on the surface of the bone material, it includes a coating film made of a methacrylic resin, and a CaO fines laminated on the coating film Furthermore, the aggregate provided in the refractory fine powder has a particle size in the range of 1 to 40 μm, the coating film provided in the refractory fine powder has a film thickness in the range of 1 to 2 μm, and provided in the refractory fine powder. The CaO fine powder has a maximum particle size of 1 μm or less, the refractory coarse powder is made of an aggregate made of MgO, a coating film made of a methacrylic resin provided on the surface of the aggregate, and the coating CaO fine powder laminated on the film Furthermore, the size of the aggregate provided in the refractory material coarse powder is larger than that of the aggregate provided in the refractory material fine powder, and the particle size is 5000 μm or less. The film thickness of the coating film is in the range of 1 to 2 μm, the size of the CaO fine powder provided in the refractory material coarse powder is larger than the CaO fine powder provided in the refractory material fine powder, and the particle size is 1 to 2 μm. wherein the range der Rukoto of, MgO-C based refractory.
[2] The refractory material fine powder is further provided in the gap of the CaO fine powder with a coating film made of a carbon-based material covering the peritoneum exposed from the gap and covering the CaO fine powder. The MgO-C refractory according to [1] above, characterized by
[3] The MgO—C refractory according to [2], wherein the coating film is made of tar or pitch.
[4] Any of the above [1] to [3], wherein the refractory fine powder has a maximum particle size of 40 μm or less and a maximum particle size of the CaO fine powder of 1 μm or less. The MgO-C refractory according to claim 1.

[5] The MgO—C system according to any one of [1] to [4] above, wherein the binder contained in the matrix and made of a carbon-based material is tar or pitch. Refractory.
[6] The MgO—C refractory according to any one of [1] to [5] above, wherein the maximum particle size of graphite (C) contained in the matrix is 200 μm or less. .
[ 7 ] The refractory material coarse powder is further provided with a coating film made of a carbon-based material so as to cover the peritoneum exposed from the gap in the gap of the CaO fine powder. The MgO-C refractory according to [ 6 ] above.
[ 8 ] The MgO-C refractory according to [ 7 ], wherein the coating film is made of tar or pitch.

According to MgO-C based refractory of the present invention, the good UNA configuration described above, in the matrix, can and aggregate consisting of MgO, and a carbon component such as graphite and a binder to restrict the contact, The occurrence of the MgO—C reaction is suppressed. As a result, even when used in a high-temperature and reduced-pressure atmosphere, the structure does not deteriorate, it is possible to prevent the occurrence of dropout damage, peeling damage, slag erosion, etc., high durability, and corrosion resistance and digestion resistance. An excellent MgO-C refractory can be realized. Therefore, for example, by applying the present invention to various molten metal containers, secondary refining equipment for steelmaking processes, etc., the durability, corrosion resistance and digestion resistance are improved, and impurities are mixed into the molten steel. The benefits of prevention can be fully enjoyed, and its social contribution is immeasurable.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which illustrates typically one Embodiment of the MgO-C type refractory which concerns on this invention, and is the schematic which shows the structure of the MgO-C type refractory made into square brick shape. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which illustrates typically one Embodiment of the MgO-C type refractory material which concerns on this invention, and is the schematic which shows the structure of the refractory material fine powder contained in a matrix, or a refractory material coarse powder. It is a figure which illustrates the Example of the MgO-C type refractory which concerns on this invention typically, and is a graph which shows the weight change rate which is a parameter | index of MgO-C reactivity evaluation. It is a figure which illustrates the Example of the MgO-C type refractory which concerns on this invention typically, and is a graph which shows the erosion index which is a parameter | index of corrosion resistance evaluation. It is a figure which illustrates the Example of the MgO-C type refractory which concerns on this invention typically, and is a graph which shows the weight change rate which is a parameter | index of digestion resistance evaluation.

  Hereinafter, embodiments of the MgO-C refractory of the present invention (hereinafter sometimes simply referred to as refractory) will be described with reference to FIGS. 1 and 2 as appropriate (if necessary, (See also FIGS. 3-5). In addition, since this embodiment is described in detail for better understanding of the gist of the invention, the present invention is not limited unless otherwise specified.

  As described above, the present inventors have repeatedly conducted intensive research to improve the durability and digestion resistance of refractories used in a high-temperature and reduced-pressure atmosphere such as an RH vacuum degasser in a steelmaking process. It was. As a result, regarding the refractory fine powder contained in the matrix, by adopting a configuration in which the CaO fine powder is adhered while covering the aggregate made of MgO with the coating film, the carbon component such as graphite contained in the matrix and It has been newly found that reaction with MgO can be effectively prevented. By adopting such a configuration, the structure does not deteriorate even when the refractory is used in a high-temperature reduced-pressure atmosphere, and it is possible to prevent the occurrence of dropout damage or peeling damage. I found it.

That is, as shown in FIGS. 1 and 2, the refractory 1 according to the present invention includes a matrix 2 containing at least a refractory material fine powder 10, graphite (C), and a binder made of a carbon-based material, and a refractory. A refractory material fine powder 10 composed of a coarse material powder 5 and contained in the matrix 2 is provided on the surface of an aggregate 11 made of MgO, and a coating film 12 made of a methacrylic resin, and on the coating film 12 And CaO fine powder 13 laminated on.
In the example shown in FIG. 2, the refractory material fine powder 10 constituting the refractory 1 further covers the gap between the CaO fine powder 13 and the peritoneum 12 exposed from the gap, and covers the CaO fine powder 13. As described above, the coating film 14 made of a carbon-based material is provided.

  As described above, the refractory structure to which the refractory 1 according to the present invention is applied includes, for example, a container for accommodating various molten metals, and an RH vacuum degassing apparatus in a secondary refining facility in a steelmaking process. Of the lower tank. The RH vacuum degassing device is provided for the purpose of removing gas components such as hydrogen and nitrogen during the production of high-grade steel until the molten steel produced from the converter is cast. By introducing molten steel into the steel, the equilibrium partial pressure is lowered and the gas components in the molten steel are removed.

  The RH vacuum degassing apparatus to which the refractory 1 according to the present invention is applicable is not shown in the figure, but normally one of the two dip tubes immersed in the molten steel in the ladle is a suction tube. By blowing argon gas into the suction pipe, the molten steel can be raised into the vacuum chamber by the action of an air lift pump. This vacuum tank is composed of a lower tank into which molten steel is introduced, and an upper tank in which a vacuum suction pipe and a gas exhaust pipe are provided, and the inside of the vacuum tank has an atmosphere reduced to, for example, about 10 torr. And the molten steel introduced into the lower tank of the vacuum tank is exposed to the high temperature vacuum atmosphere of the molten metal surface, so that hydrogen, nitrogen, etc. contained in the molten steel are taken out into the vacuum atmosphere of the upper tank. Degassing treatment is performed. Then, the molten steel that has been degassed in the vacuum chamber is refluxed into the ladle through a discharge pipe that is one remaining dip pipe. The RH vacuum degassing apparatus in which such degassing processing is performed is suitable for quickly degassing a large amount of molten steel because the reflux rate of molten steel is higher than that of other apparatuses and methods. . In addition to the above degassing treatment, various treatment functions such as decarburization and temperature rise by blowing pure oxygen gas into the vacuum chamber, and introducing flux and various additive elements into the molten steel should be provided. Is also a possible device.

  As described above, the matrix 2 contained in the refractory 1 contains the refractory material fine powder 10, graphite (C), and a binder made of a carbon-based material. By including the matrix 2 having such a configuration, the refractory 1 has an effect of improving the bonding property and formability of the refractory coarse powder 5 described later. Here, for example, when the refractory is composed only of the refractory coarse powder described later, when it is press-formed into a shape such as a square brick shape, the bonding force is too weak and the shape as a solid material can be maintained. It becomes brittle.

  As described above, the refractory material fine powder 10 contained in the matrix 2 is provided with the coating film 12 made of methacrylic resin on the surface of the aggregate 11 made of MgO, and the CaO fine powder 13 is laminated on the coating film 12. Being done.

The aggregate 11 is made of, for example, magnesia (magnesium oxide: MgO) having a purity of 99% or more, and functions as a highly fire-resistant base material (aggregate) in the refractory fine powder 10.
Although it does not specifically limit as a raw material of MgO which makes the aggregate 11, For example, natural magnesite, seawater magnesia, sweet water magnesia, etc. can be used.
As for the size of the aggregate 11, it is more preferable that the maximum particle size is 40 μm or less. When the size of the aggregate 11 exceeds 40 μm, the filling between the coarse grains becomes insufficient, and the closed pores and open pores in the brick increase, which may cause a problem that the corrosion resistance and strength are lowered. The minimum particle size of the aggregate 11 is more preferably set to 1 μm or more in consideration of industrial production and function maintenance.

The coating film 12 is a film that adheres a CaO fine powder 13 described later while covering the entire surface of the aggregate 11 and is made of a methacrylic resin. As the methacrylic resin forming the aggregate 11, for example, PMMA can be used.
In the present invention, by adhering CaO fine powder 13 while covering the aggregate 11 with the coating film 12, MgO as a component of the aggregate 11, and carbon components such as graphite and binder contained in the matrix 2 Can be effectively prevented. As a result, it is possible to prevent the MgO—C reaction from occurring, and the structure of the refractory 1 is not deteriorated. Therefore, dropout damage, peeling damage, slag erosion, etc. occur even in a severe use atmosphere under high temperature and reduced pressure. Can be prevented, and the durability, corrosion resistance and digestion resistance can be improved.

  Moreover, in this invention, the effect | action which the adhesiveness of the CaO fine powder 13 with respect to the aggregate 11 and the coating film 12 improves by using a methacrylic resin for the coating film 12 which covers the aggregate 11 is acquired. Thereby, the adhesive strength of the CaO fine powder 13 with respect to the bone core material 11 which is a base material becomes high, and the effect by this invention mentioned above becomes more remarkable.

As the coating film 12, in order to improve the adhesive strength of the CaO fine powder 13, it is preferable to use a methacrylic resin material having a tensile shear strength of 1.0 MPa or more at a temperature of 0 ° C. or higher.
The film thickness of the coating film 12 is not particularly limited, but it is more preferably in the range of 1 to 2 μm in consideration of the barrier property for suppressing the MgO—C reaction and the adhesiveness of the CaO fine powder 13.

The CaO fine powder 13 is a fine powder having an action of suppressing the MgO—C reaction, and is adhered to the aggregate 11 by the coating film 12.
As the size of such CaO fine powder 13, the maximum particle size is preferably 1 μm or less. When the size of the CaO fine powder exceeds 1 μm, a CaO particle interface exists on the surface of the refractory material fine powder, and it may be difficult to obtain an effect of improving digestion resistance. On the other hand, too small the size of the CaO fines, only the thickness of the coating film formed by CaO fine powders thin, Ru if there be difficult to obtain the effect of the digestion-improving.

  The refractory 1 according to the present invention has a structure in which an exhausted membrane 12 and a CaO fine powder 13 are laminated on an aggregate 11 to suppress the MgO—C reaction as described above, thereby improving durability, corrosion resistance, and resistance to resistance. A sufficient effect to improve digestibility can be obtained.

Further, in the present invention, as illustrated in FIG. 2, the gap between the CaO fine powders 13 is made of a carbon-based material so as to cover the peritoneum 12 exposed from the gap and to cover the CaO fine powder 13. A configuration in which the coating film 14 is provided is more preferable from the viewpoint of significantly improving the digestion resistance. The carbon-based material forming the coating film 14 is not particularly limited, and for example, tar, pitch, or the like can be appropriately employed.
In the present invention, even if the coating film 14 having a carbon-based component is provided on the outermost surface of the refractory material fine powder 10, the aggregate 11 made of MgO is covered with the coating film 12. Therefore, the MgO—C reaction does not occur.

The matrix 2 contains carbon components such as graphite (C) and a binder in addition to the refractory material fine powder 10 having the above-described configuration.
The graphite contained in the matrix 2 is not particularly limited as long as it is made of a graphite material capable of supplying carbon at a high concentration in the refractory 1. As such a graphite material, various materials such as natural scale graphite, earthy graphite, artificial graphite, and treated graphite can be appropriately employed.
The graphite contained in the matrix 2 preferably has a maximum particle size of 200 μm or less. When the maximum particle size of graphite exceeds 200 μm, the filling between coarse particles becomes insufficient, and the closed pores and open pores in the brick increase, which may cause a problem that the corrosion resistance and strength are lowered.

  Moreover, the binder contained in the matrix 2 is composed of a carbon-based material, and among these, tar or pitch is preferably used. As such tars and pitches, those conventionally known in this field can be employed without any limitation. For example, coal tar, petroleum pitch, charcoal pitch, synthetic pitch, etc. can be appropriately employed.

  In the present invention, as described above, since the aggregate 11 made of MgO is covered with the coating film 12 and the CaO fine powder 13 is adhered, the carbon component contained in a large amount in the matrix 2 and the MgO constituting the aggregate 11 And no contact with MgO-C reaction. Therefore, it is possible to prevent the occurrence of dropout damage, peeling damage, slag erosion, etc. even in a use atmosphere under high temperature and reduced pressure, and excellent durability, corrosion resistance and digestion resistance can be obtained.

In the present invention, the other components contained in the matrix 2 are not particularly limited. However, in a refractory such as a brick, usually, SiO ₂ , Al ₂ O ₃ , Fe ₂ O _3, etc. These components are inevitably contained. However, these components form a low melting point substance by combining with CaO at a relatively low temperature and remarkably reduce the effect of improving digestion resistance by CaO fine powder, so the content should be reduced as much as possible. Is preferred.

The refractory material coarse powder 5 contained in the refractory 1 is an aggregate contained in the refractory 1 together with the matrix 2, and the effect of ensuring high fire resistance of the refractory 1 is obtained.
In the present invention, in addition to the refractory material fine powder 10 contained in the matrix 2, the refractory material coarse powder 5 is further provided with a coating film 52 made of methacrylic resin on the surface of the aggregate 51 made of MgO. It is good also as a structure which laminated | stacked the CaO fine powder 53 on the coating film 52 (refer FIG. 2). Thus, the refractory material coarse powder 5 is contained in the matrix 2 and the aggregate 51 which is the base material of the refractory material coarse powder 5 by having the same configuration as the refractory material fine powder 10 contained in the matrix 2. Since the carbon component does not come into contact, the MgO—C reaction can be prevented from occurring. As a result, it is possible to prevent the occurrence of dropout damage, peeling damage, slag erosion, etc. even in a use atmosphere under high temperature and reduced pressure, and excellent durability, corrosion resistance and digestion resistance can be obtained. .
When the refractory coarse powder 5 has the above-described configuration, the same material as the refractory fine powder 10 can be used as the material of the aggregate 51, the coating film 52, and the CaO fine powder 53.

The size of the aggregate 51 constituting the refractory coarse powder 5 is larger than that of the aggregate 11 of the refractory fine powder 10, and for example, it is more preferable that the maximum particle size is 5000 μm or less and the minimum particle size is 1 μm or more. .
Also, the film thickness of the coating film 52 is preferably in the range of 1 to 2 μm in consideration of the barrier property for suppressing the MgO—C reaction and the adhesiveness of the CaO fine powder 53.
The size of the CaO fine powder 53 is larger than the CaO fine powder 13 of the refractory fine powder 10 in consideration of the size of the aggregate 51, for example, the maximum particle size is 2 μm or less and the minimum particle size is 1 μm or more. It is more preferable.

  Similarly to the refractory material fine powder 10, in the refractory material coarse powder 5, a coating film 54 made of a carbon-based material is further provided in the gap of the CaO fine powder 53 so as to cover the abdominal membrane 52 exposed from this gap. It is more preferable from the point that digestion resistance improves remarkably. Further, tar and pitch can also be used as the carbon-based material forming the coating film 54 as described above.

In addition, in making the refractory material fine powder and the refractory material coarse powder into the above-described configuration, for example, the CaO fine powder is carbonized or the surface of the CaO fine powder is made of FeO and CaO instead of the coating film made of the carbon-based material. Even when the composite oxide is formed, the effect of improving digestion resistance can be obtained as described above. However, from the viewpoint of preventing the reaction between CaO and external moisture (H ₂ O) in the case of providing a carbonation treatment of CaO fine powder and providing a composite oxide of FeO and CaO, a carbon-based material Most preferably, the coating film is provided with a coating film.

As a method for producing the refractory 1 having the above configuration, a conventionally known method can be employed without any limitation.
Here, when manufacturing the refractory material fine powder 10 having a laminated structure having the above-described structure, for example, first, an aggregate 11 made of MgO is put in a mill, and further, PMMA resin is added and stirred and mixed. A coating film 12 made of PMMA is formed on the surface of the aggregate 11.
Next, CaO fine powder 13 is put into the mill and stirred. At this time, in the mill, the aggregate 11 on which the coating film 12 is formed and the CaO fine powder 13 collide with each other, so that heat energy is generated between them. The adhesive action of the coating film 12 is activated by this thermal energy, and the coating film 12 and the CaO fine powder 13 are sequentially laminated on the surface of the aggregate 11.
Next, if necessary, a coating film 14 is formed so as to cover the coating film 12 in the gaps between the CaO fine powders 13 by putting a carbon material such as pitch or tar into the mill and stirring the mixture. The material fine powder 10 is obtained.

Next, the refractory material fine powder 10 obtained by the above procedure is kneaded at a predetermined ratio with graphite and a binder made of a carbon material such as pitch or tar to form a matrix 2.
Moreover, the refractory material coarse powder 5 is also manufactured in the same procedure as the refractory material fine powder 10.
And after knead | mixing these matrix 2 and the refractory material coarse powder 5, it shape | molds, for example in the shape of a square brick, Furthermore, the refractory 1 is obtained by performing a heat-firing process.

  As described above, according to the MgO-C refractory of the present invention, the refractory fine powder 10 contained in the matrix 2 is provided on the surface of the aggregate 11 made of MgO as described above. A configuration including a coating film 12 made of a resin and CaO fine powder 13 laminated on the coating film 12 is employed. With such a configuration, it is possible to regulate the contact between the aggregate 11 made of MgO and the carbon component such as graphite or binder in the matrix 2, and the occurrence of the MgO—C reaction is suppressed. As a result, even when used in a high-temperature and reduced-pressure atmosphere, the structure does not deteriorate, and it is possible to prevent the occurrence of drop damage, peeling damage, slag erosion, etc., high durability, and corrosion resistance and digestion resistance. An excellent MgO-C refractory 1 can be realized. Therefore, for example, by applying the present invention to various molten metal containers, secondary refining equipment for steelmaking processes, etc., the durability, corrosion resistance and digestion resistance are improved, and impurities are mixed into the molten steel. The benefits of prevention can be fully enjoyed, and its social contribution is immeasurable.

  Examples of the MgO-C refractory according to the present invention will be described below to explain the present invention more specifically. The present invention is not limited to the following examples, and can be implemented with appropriate modifications within a range that can be adapted to the purpose described above and below. It is included in the technical scope.

In this example, first, a refractory having a laminated structure and chemical components as shown in Table 1 below was manufactured according to the following procedures and conditions.
Here, (A) to (G) shown in the laminated configuration of Table 1 below are the configurations as shown below, and among these, (A ) and ( D ) are examples of the present invention, and (B) , (E), (G) is Ri Comparative example der, (C), (F) is Ru reference example der.
(A) The refractory material fine powder and the refractory material coarse powder were used as aggregate + coating film + CaO fine powder + coating film.
(B) Only refractory material coarse powder was used as aggregate + coating film + CaO fine powder + coating film.
(C) Only refractory material fine powder was used as aggregate + coating film + CaO fine powder + coating film.
(D) The refractory material fine powder and the refractory material coarse powder were aggregated + coating film + CaO fine powder.
(E) Only coarse refractory powder was used as aggregate + coating film + CaO fine powder.
(F) Only refractory material fine powder was used as aggregate + coating film + CaO fine powder.
(G) Neither the refractory material fine powder nor the refractory material coarse powder adopted the laminated structure of the present invention.

In (A) of the present invention example shown in Table 1, first, an aggregate made of MgO and having a maximum particle size of 40 μm is put in a mill, and further, PMMA resin is added and stirred and mixed. A coating film was formed on the surface of the aggregate. At this time, the input amount of PMMA resin and the stirring time were adjusted so that the film thickness of the coating film was about 1 μm.
Next, the CaO fine powder having a maximum particle size of 1 μm is put into the mill, and further stirred to adhere the CaO fine powder to the aggregate by the adhesive action of the coating film. It was set as the structure where the coating and CaO fine powder were laminated | stacked one by one.
Next, a pitch composed of a carbon material was introduced into the mill and stirred to form a coating film so as to cover the coating film in the gap of the CaO fine powder, and a refractory fine powder as illustrated in FIG. 2 was obtained. .

Moreover, about the refractory material coarse powder, it manufactured in the procedure similar to the said refractory material fine powder, and obtained the refractory material coarse powder illustrated in FIG. At this time, an aggregate having a maximum particle size of 5000 μm was used. The film thickness of the coating film was about 1 μm, and the CaO fine powder having a maximum particle size of 2 μm or less and a minimum particle size of 1 μm or more was used.

Next, the refractory material fine powder obtained by the above procedure was kneaded with a binder composed of graphite and carbon pitch to obtain a matrix. The mixing ratio at this time was, in mass%, refractory material fine powder: 50%, graphite: 35%, and binder: about 15%.
And after knead | mixing these matrix and refractory material coarse powder, it shape | molds in the shape of a square brick as shown in FIG. 1, and also heat-fires by the conditions of 200 degreeC x 24Hr, and this invention example ( A) refractory was obtained.

In addition, except for the point that the laminated structure of the refractory material fine powder and the refractory material coarse powder was changed to the specifications described in Table 1 and (B) to (G) above, the present invention example ( (D)), the ratio Comparative examples ((B), (E) , (G)), as well as reference examples ((C), to obtain a refractory (F)). In addition, what is not described in the laminated structure shown in Table 1 indicates a conventional structure in which the laminated structure defined in the present invention is not adopted and MgO that is not covered is used as it is.

And the evaluation test which is demonstrated below was done about the refractory material of (A)-(G) obtained by the said procedure.
First, the weight change rate was investigated as an evaluation of MgO—C reactivity. In this weight change rate test, a reduction firing furnace was used, and the refractory was subjected to reduction firing under the condition of 1400 ° C. × 10 Hr where the MgO—C reaction easily occurs, and the weight change at that time was measured. And the MgO-C reactivity was evaluated by this weight change rate, and the results are shown in the following Table 3 and the graph of FIG.

  For evaluation of corrosion resistance, a refractory was reduced and fired at 1700 ° C. × 20 min for 24 cycles using a rotary erosion furnace, and then an erosion test was performed using the erodants of the components shown in Table 2 below. . And the corrosion index was calculated | required in this case, the corrosion resistance was evaluated, and the result was shown to the graph of following Table 3 and FIG.

  For evaluation of digestion resistance, the refractory was held in a constant temperature and humidity furnace maintained at a temperature of 50 ° C. and a humidity of 90% for 360 hours. And digestion resistance was evaluated by measuring the weight change in this case, and the result was shown in the following Table 3 and the graph of FIG.

As shown in the results of Table 3 and FIGS. 3 to 5, the present invention example (A), the reference example (C), the present invention example (D), and the reference example (F) having the laminated structure defined in the present invention. These refractories have a weight change rate after reduction firing of 1.16% or less, and are clearly excellent in MgO—C resistance. In addition, the refractories of the present invention example and the reference example all have an erosion index of 85 or less when subjected to an erosion test after reduction firing using a rotary erosion furnace, and are clearly excellent in corrosion resistance. In addition, the refractories of the present invention example and the reference example have a weight change rate in the range of 0.17 to 0.90% after being held in a constant temperature and humidity environment in a constant temperature and humidity furnace, and there is no practical problem. It was revealed to have a range of digestion resistance.

  On the other hand, since the refractory materials of Comparative Examples (B), (E), and (G) do not have the laminated structure defined in the present invention, the refractory fine powder contained in the matrix is not resistant to MgO-C reaction. As a result, at least one of the property, the corrosion resistance, and the digestion resistance is inferior.

Here, the refractory of the present invention example (A) has a coating film and a CaO fine powder in which both a refractory fine powder and a refractory coarse powder are laminated on an aggregate made of MgO, and further made of a carbon material. Therefore, it can be seen that all of MgO—C reactivity, corrosion resistance, and digestion resistance are remarkably excellent.
In addition, the refractory of Reference Example (C) is an example in which only the refractory material fine powder has a laminated structure defined in the present invention, but has excellent MgO-C reactivity and corrosion resistance, and further is resistant to digestion. It turns out that the property is very excellent.

In addition, the refractory of the present invention example (D), except that a coating film made of a carbon material is not provided, both the refractory fine powder and the refractory coarse powder are coated on the aggregate made of MgO and This is an example in which a laminated structure defined by the present invention in which CaO fine powder is laminated is adopted. As shown in Table 3 and the results of FIGS. 3 to 5, the refractory of the present invention example (D) is very excellent in MgO—C reactivity and corrosion resistance, and the digestion resistance is in a practical range. It turns out that it is in.
Further, the refractory of Reference Example (F) is the present invention in which the coating film and CaO fine powder are laminated only on the refractory material fine powder and the aggregate made of MgO except that the coating film made of the carbon material is not provided. This is an example in which the laminated structure specified in the above is adopted. As shown in Table 3 and the results of FIGS. 3 to 5, the refractory material of Reference Example (F) has very excellent MgO—C reactivity and corrosion resistance, and the digestion resistance is within the practical range. It turns out that it is.

  In addition, the refractory of the comparative example (B) is an example in which only the refractory material coarse powder has a structure in which the coating film and the CaO fine powder are laminated on the aggregate made of MgO as described above. In Comparative Example (B), since the refractory coarse powder is coated with carbon, the digestion resistance is relatively good, but the weight change rate after reduction firing is large, and the dissolution resistance is high. Since the loss index was also large, the results were inferior in MgO—C reactivity and corrosion resistance.

  In addition, the refractory of Comparative Example (E) has a structure in which only the refractory material coarse powder, the coating film and the CaO fine powder are laminated on the aggregate made of MgO as described above, and the carbon coating is not provided. It is. In Comparative Example (E), although the digestion resistance is within the practical range, the weight change rate after reduction firing is large, and the melt loss index is large, so that the MgO-C reactivity and the corrosion resistance are inferior. As a result.

  In addition, the refractory of Comparative Example (G) has a conventional structure in which neither the refractory material fine powder nor the refractory material coarse powder adopts the laminated structure defined in the present invention. In Comparative Example (G), although the digestion resistance is a good result, the weight change rate after reduction firing is very large and the erosion index is also very large. The result was inferior in corrosion resistance.

  From the results of the examples described above, the MgO-C refractory of the present invention does not deteriorate even when used in a high-temperature and reduced-pressure atmosphere, and dropout damage, peeling damage, slag erosion, etc. occur. It is clear that it can be prevented, has high durability, and is excellent in corrosion resistance and digestion resistance.

  According to the present invention, even when used in a high-temperature and reduced-pressure atmosphere, the structure does not deteriorate, and the occurrence of dropout damage, peeling damage, slag erosion, and the like is suppressed. Therefore, for example, by applying the present invention to various molten metal containers, secondary refining equipment for steelmaking processes, etc., the durability, corrosion resistance and digestion resistance are improved, and impurities are mixed into the molten steel. The benefits of prevention can be fully enjoyed, and its social contribution is immeasurable.

1 ... MgO-C refractory (refractory),
2 ... Matrix
10 ... refractory material fine powder,
11 ... aggregates,
12 ... coating film,
13 ... CaO fine powder,
14 ... coating film,
5 ... Coarse refractory powder 51 ... Aggregate,
52. Coating film,
53 ... CaO fine powder,
54 ... coating film,

Claims (8)

At least a refractory material fine powder, graphite (C), and a MgO-C refractory comprising a refractory material coarse powder containing a matrix containing a binder made of a carbon-based material,
The refractory fine powder contained in the matrix includes an aggregate made of MgO , a coating film made of methacrylic resin provided on the surface of the aggregate , and a CaO fine powder laminated on the coating film. Furthermore, the particle size of the aggregate provided in the refractory material fine powder is in the range of 1 to 40 μm, the thickness of the coating film provided in the refractory material fine powder is in the range of 1 to 2 μm, and the fire resistance The maximum particle size of the CaO fine powder provided in the material fine powder is 1 μm or less,
The refractory coarse powder comprises an aggregate made of MgO, a coating film provided on the surface of the aggregate and made of a methacrylic resin, and CaO fine powder laminated on the coating film, Further, the size of the aggregate provided in the refractory coarse powder is larger than that of the aggregate provided in the refractory fine powder and the particle size is 5000 μm or less, and the coating film provided in the refractory coarse powder. The size of the CaO fine powder provided in the refractory material coarse powder is larger than the CaO fine powder provided in the refractory material fine powder and the particle size is in the range of 1 to 2 μm. A MgO-C refractory characterized by the above.   The refractory fine powder is further provided with a coating film made of a carbon-based material covering the peritoneum exposed from the gap and covering the CaO fine powder in the gap of the CaO fine powder. The MgO-C refractory according to claim 1.   The MgO-C refractory according to claim 2, wherein the coating film is made of tar or pitch.   4. The refractory fine powder according to claim 1, wherein the aggregate has a maximum particle size of 40 μm or less, and the CaO fine powder has a maximum particle size of 1 μm or less. 5. The MgO-C refractories described.   The MgO-C refractory according to any one of claims 1 to 4, wherein the binder contained in the matrix and made of a carbon-based material is tar or pitch. The MgO-C refractory according to any one of claims 1 to 5, wherein the maximum particle size of graphite (C) contained in the matrix is 200 µm or less . The refractory material coarse powder, further, the gap between the CaO fine, so as to cover the object to be peritoneal exposed from the gap, wherein the coating film made of a carbon-based material is provided, according to claim 6 The MgO-C refractory according to 1. The MgO-C refractory according to claim 7 , wherein the coating film is made of tar or pitch.

Images