JP2019042770A - Aggregate for refractory, refractory, and plate for sliding nozzle - Google Patents

Abstract

To provide an aggregate for a refractory excellent in corrosion resistance, wear resistance and thermal spalling resistance, a refractory, and a plate for a sliding nozzle.SOLUTION: Provided is an aggregate for a refractory incorporated into a refractory, in which, provided that the mass of the whole is defined as 100 mass%, a chromium component of 10 mass% or lower, and the balance alumina component are comprised so as to be formed, and also, porosity is 10 to 20%. Also provided is a refractory comprising: an aggregate for the refractory; and a base material dispersing the aggregate for the refractory, in which, provided that the mass of the whole of the refractory is defined as 100 mass%, the aggregate for the refractory is comprised by 20 to 70 mass%. Also provided is a plate for a sliding nozzle using the aggregate for the refractory.SELECTED DRAWING: None

Description

  The present invention relates to a refractory aggregate, a refractory using the same, and a sliding nozzle plate.

  A sliding nozzle having a sliding nozzle plate is used for flow control when discharging the molten steel from the container via the nozzle. In the sliding nozzle, the sliding nozzle plate is made to relatively slide, thereby adjusting the opening degree of the inner hole which is the molten steel flow path, and performing flow control of the molten steel. The sliding nozzle plate is formed of a refractory.

  Refractories forming the sliding nozzle plate include alumina refractories having alumina as a main component. Alumina-based refractories are manufactured from powder based on alumina. Specifically, it is sintered or electrofused to form a massive body. Then, after the lump is crushed, it is classified into coarse particles (for example, particle size: 3 mm or more), middle particles (for example, particle size: 3 to 1 mm), and fine particles (for example, particle size: 1 to 0.1 mm). Alumina-based refractories are manufactured using the obtained coarse-fine to fine-grained particles (also referred to as aggregate) as a raw material.

  Among the alumina-based refractories, the aggregate is preferably compact and high in strength. For this reason, particles having a porosity of 5% or less are used in the aggregate. 70 to 50 mass% of coarse to medium particle powders and 30 to 50 mass% of fine particles are mixed, water, resin and fine particles are added and kneaded to form a mixed clay (press or cast molding), a formed body Is fired (or unfired) to give strength for commercialization.

  Alumina, which is the main component of the alumina refractory, has a high melting point and is excellent in corrosion resistance. On the other hand, alumina is inferior in heat resistance spalling resistance because it has a high coefficient of thermal expansion. For this reason, the alumina refractory has a problem that a crack and exfoliation occur.

In order to solve this problem, in the case of an alumina refractory, heat resistance spalling is provided by providing pores inside. However, since the particles of the aggregate are dense, the pores contained in the alumina refractory are concentrated in the base material (matrix portion). When pores are concentrated on the base material, the amount of slag permeating the pores of the base material increases when the alumina refractory is used for molten steel (hot metal) application (plate for sliding nozzle), and The decrease in strength occurs due to the concentration on the surface, and the wear resistance of the alumina refractory is reduced. That is, damage to the refractory is preceded by erosion of the substrate in which the pores are present, and damage to the refractory proceeds.
In addition, in order to improve the corrosion resistance and the wear resistance (that is, the strength) of the refractory, it is necessary to make the porosity of the substrate as small as possible. However, when the porosity of the substrate was reduced, the heat resistance spalling resistance was reduced.
For such a problem, Patent Document 1 discloses a refractory (a plate for a sliding nozzle) using an alumina aggregate having a porosity of 10 to 20%.

Unexamined-Japanese-Patent No. 2016-175799

However, even in a refractory using a porous alumina aggregate, there is a problem that the corrosion resistance is not sufficient.
The present invention was made in view of the above situation, and it is an object of the present invention to provide a refractory aggregate excellent in corrosion resistance, wear resistance and heat resistance spalling resistance, a refractory using the same and a sliding nozzle plate. Do.

The aggregate for refractories according to the present invention for solving the above-mentioned problems is an aggregate for refractories contained in the refractory in a state of being dispersed in a base material, and the aggregate for refractories has a total mass of 100 mass% It is characterized in that it is formed by containing 10 mass% or less of the chromium component and the remaining alumina component, and the porosity is 10 to 20%.
The aggregate for refractories according to the present invention is made of an alumina-chromium material. In particular, by containing a chromium component, the corrosion resistance of the refractory aggregate is improved as compared to the conventional alumina aggregate for refractory.
Moreover, the aggregate for refractories of this invention has a porosity of 10 to 20%. The heat-resistant spalling resistance is improved because the aggregate for refractories has pores.
As mentioned above, the aggregate for refractories of this invention exhibits the effect which can obtain the refractories excellent in corrosion resistance, abrasion resistance, and heat-resistant spalling resistance.

  It is preferable that the aggregate for refractories of this invention contains a silica component by 20 mass% or less. By further containing silica, the aggregate for refractories of the present invention is made of an alumina-silica-chromium material, and the strength of the aggregate for refractories is further improved.

  In the aggregate for a refractory according to the present invention, it is preferable that chromium oxide as a chromium component, alumina as an alumina component, and silica as a silica component are mixed in an atomic state or a molecular state. By being comprised in the state in which each component was mixed, the heat resistance and corrosion resistance improve the aggregate for refractories of this invention.

Further, the refractory of the present invention for solving the above problems comprises the aggregate for refractory of the present invention (the aggregate for refractory according to claims 1 to 3) and a base material for dispersing the aggregate for refractory And the aggregate for the refractory is contained at 20 to 70 mass% when the mass of the whole refractory is 100 mass%.
The refractory of the present invention is a refractory comprising the aggregate for a refractory of the present invention, and exhibits the effect of becoming a refractory excellent in corrosion resistance, wear resistance and heat resistance spalling resistance.
In the refractory of the present invention, the base material is preferably composed mainly of alumina. With this configuration, the refractory of the present invention is formed mainly of alumina, and the above-described effects can be more reliably exhibited.

Moreover, the plate for sliding nozzles of this invention which solves the said subject is formed by containing the chromium component of 10 mass% or less, and the alumina component of remainder, when the mass of the whole aggregate for refractories is 100 mass%. Plate for a sliding nozzle having a refractory aggregate having a porosity of 10 to 20% and a base material mainly composed of alumina for dispersing the refractory aggregate and having a porosity of 10 to 20% That is, when the mass of the whole plate for sliding nozzles is 100 mass%, it is characterized by containing the aggregate for fireproofs by 20-70 mass%.
Since the sliding nozzle plate of the present invention is made of the refractory of the present invention, it exhibits the effect of becoming a sliding nozzle plate excellent in corrosion resistance, wear resistance and heat resistance spalling resistance.
In the sliding nozzle plate of the present invention, the refractory aggregate preferably has a particle size of 0.1 to 5 mm. When the particle diameter of the aggregate for refractory is in this range, the above-mentioned effect can be more reliably exhibited.

  In the sliding nozzle plate of the present invention, carbon is preferably introduced into the pores of the refractory aggregate and the pores of the base material. By this configuration, the wettability with the molten slag passing through the sliding nozzle is reduced. As a result, the sliding nozzle plate has improved corrosion resistance to molten slag.

It is a SEM photograph of the cross section after pitch impregnation and heat processing of the refractory of sample A. It is a SEM photograph of the cross section after pitch impregnation and heat processing of the refractory of sample B. It is a SEM photograph of the cross section after pitch impregnation and heat treatment of the refractory of sample C. It is a SEM photograph of the cross section after pitch impregnation and heat treatment of the refractory of sample D. It is a graph which shows the relationship between the porosity of the aggregate for refractories, and the porosity of a refractory. It is a graph which shows the relationship between the porosity of aggregate for refractories, and the bulk specific gravity of refractories. It is a graph which shows the relationship between the porosity of the aggregate for refractory materials, and the bending strength of a refractory material. It is a graph which shows the relationship between the porosity of the aggregate for refractories, and the compressive strength of a refractor. It is a graph which shows the degradation rate change of the elastic modulus in a heat-resistant spalling test. It is a figure which shows the cross section after the oxygen washing | cleaning test of a refractory. It is a graph which shows the test result of the oxidation-proof abrasion test of a refractory.

  Hereinafter, the aggregate for refractories of the present invention and refractories using the same according to the embodiment will be specifically described. Note that the embodiment shows one form for specifically explaining the present invention, and the present invention is not limited to the embodiment.

[Aggregate for refractory]
The aggregate for a refractory according to the present embodiment is an aggregate for a refractory contained in the refractory in a state of being dispersed in a base material, and the aggregate for a refractory is 10 mass when the entire mass is 100 mass%. % Or less of chromium component and the remainder alumina component.

The aggregate for refractories is formed by containing 10 mass% or less of the chromium component and the balance of the alumina component. The aggregate for refractories is formed by containing a chromium component and an alumina component. Here, what is formed by containing the chromium component and the alumina component indicates that it is formed (or manufactured) from the raw material corresponding to the chromium component and the raw material corresponding to the alumina component. And the aggregate for refractories of this form is manufactured through the process of fuse | melting or sintering a raw material like the manufacturing method mentioned later. Therefore, it has a configuration in which chromium of the chromium component is diffused (or dispersed) in the atomic state (or molecular state) in the alumina component.
The aggregate for a refractory according to the present embodiment contains the chromium component in an amount of 10 mass% or less, when the total mass is 100 mass%.

The chromium component indicates a component containing a chromium atom. The chromium component indicates a component in which the most component of the contained metal element is chromium. That is, a compound or a complex (solid solution) may be formed with another element (metallic element). The chromium component is preferably a component (compound) in which the metal element excluding the inevitable impurities is only chromium. The chromium component is preferably chromium oxide (Cr ₂ O ₃ ).

  In the aggregate for refractories of the present embodiment, the inclusion of the chromium component makes the aggregate for refractories have chromium atoms, and the corrosion resistance (particularly, the oxidation resistance) of the aggregate for refractories is improved. When the content of chromium exceeds 10% by mass, the content of chromium is excessive, and the heat resistance spalling resistance is lowered. The content of the chromium component is preferably 0.5 to 5 mass%, and more preferably 1 to 3 mass%.

  The remaining portion of the aggregate for a refractory of the present embodiment is formed of an alumina component. The remainder indicates that the alumina component is used as a component excluding the chromium component (and the other additive components) in the material forming the aggregate for refractories. That is, the aggregate for a refractory according to the present embodiment is formed mainly of alumina.

An alumina component shows the component which contains an alumina as a main component (component with most content rate). Furthermore, a compound or a complex (solid solution) may be formed with another element (metal element). The alumina component is preferably a component (compound) consisting of only alumina except for unavoidable impurities. The higher the content of alumina (Al ₂ O ₃ ) is, the more preferable the alumina component is, and the most preferable is pure alumina. By using an alumina component, since expensive raw materials such as alumina-zirconia and zirconia-mullite are not used, an increase in manufacturing cost can be suppressed. Moreover, the corrosion resistance of the aggregate for refractory improves, so that the alumina component has a large content rate of alumina.

The aggregate for a refractory according to the present embodiment preferably further contains a silica component at 20% by mass or less. The silica component indicates a component containing silicon in the state of an oxide (silica, for example, SiO ₂ ) as a main component (component with the highest content ratio). It is preferable that a silica component is a component (compound) which consists only of silica except an unavoidable impurity. The silica of the silica component may form a compound with alumina. That is, an aluminosilicate such as mullite may be formed.
In the refractory aggregate of the present embodiment, the strength of the refractory aggregate itself is further increased by containing the silica component. On the other hand, when the content of the silica component exceeds 20 mass%, the silica component becomes excessive, and the corrosion resistance of the aggregate for refractories decreases.

  The aggregate for a refractory according to the present embodiment preferably contains other elements at 5 mass% or less, based on 100 mass% of the total mass. Here, the other elements indicate elements that form a compound with alumina, a chromium component or a silica component, and unavoidable impurities.

  In the aggregate for a refractory according to the present embodiment, the content ratio of each component can be determined from the ratio of the raw material used. That is, in the case of manufacturing by the manufacturing method described later, when using the raw material corresponding to each component, the content ratio of each component can be determined from the mixing ratio of the raw material to be used. Qualitative analysis may be performed on the aggregate for refractory of the present embodiment to determine the content ratio.

  The aggregate for a refractory according to the present embodiment has a porosity of 10 to 20%. By having a porosity of 10 to 20%, the refractory aggregate has a porous configuration with pores. When the aggregate for refractories has pores, even when the aggregate for refractories and refractories generate stress due to thermal shock when used for a refractor, the generated stress can be effectively absorbed. As a result, even if a crack occurs in the refractory containing the aggregate for refractory, the aggregate for refractory can suppress the development of the crack.

  More specifically, a refractory material using the aggregate for a refractory of the present embodiment (a refractory material of the present embodiment described later) includes an aggregate for a refractory and a base material for dispersing the aggregate for a refractory. It has the composition which it has. When thermal shock is applied to the refractory, stress is generated in the refractory. In this embodiment, since the aggregate for refractories itself has pores, the strength is lower than in the case of the compact, and the stress generated in the refractory can be absorbed not only to the base material but also to the aggregate for refractories. . Then, even if a crack caused by this stress occurs in the refractory material (base material), when the developed crack reaches the refractory aggregate, the stress for the crack to propagate in the refractory aggregate Absorbed As a result, the further development of the crack can be suppressed.

  When the porosity is less than 10%, the effect of suppressing the growth of cracks is reduced. When the porosity is increased to more than 20%, the strength of the refractory aggregate is reduced. In this case, the refractory aggregate may be cracked or worn away due to thermal shock or abrasion when used as a refractory. The porosity is more preferably 15% to 19%. In the present embodiment, the porosity indicates an apparent porosity calculated according to JIS R2205.

  The diameter of the pores formed in the refractory aggregate of the present embodiment is not limited. It can determine suitably by the use application of the refractory formed using an aggregate for refractories. For example, the pore diameter (average pore diameter, D50) is preferably 0.1 to 10 μm, and more preferably 0.5 to 5 μm. Moreover, it is preferable that the space | interval of D10 and D90 is 0.05-25 micrometers also about a hole diameter distribution.

  In the aggregate for a refractory of the present embodiment, the pores are preferably uniformly distributed. The uniform distribution of pores in the aggregate for refractories makes it possible to relieve (absorb) stress throughout the aggregate for refractories, and suppress the development of cracks in the refractories (and the aggregate for refractories). can do. If the pores are unevenly distributed in the refractory aggregate, it may be insufficient to relieve (absorb) the stress applied to the refractory aggregate, and it is insufficient to suppress the growth of the crack. There is a possibility of Here, the distribution of pores can be directly observed using a SEM photograph or the like.

[Refractory]
The refractory of the present embodiment is a refractory having the aggregate for a refractory of the present embodiment and a base material for dispersing the aggregate for a refractory. And when the mass of the whole refractory is 100 mass%, 20 to 70 mass% contains the aggregate for refractory.

  The aggregate for refractory contained in the refractory of the present embodiment is the aggregate for refractory of the present embodiment described above. When the mass of the whole refractory is 100 mass%, the aggregate for refractory is contained by 20-70 mass%. By containing the aggregate for refractory at 20 to 70 mass%, the refractory becomes excellent in corrosion resistance, wear resistance and heat resistance spalling resistance.

  If the aggregate for refractory is less than 20 mass%, the effect of suppressing the growth of the crack generated in the refractory is not sufficiently exhibited. Moreover, when the aggregate for refractories increases by more than 70 mass%, the possibility that the quantity of the base material which disperses the aggregate for refractories may run short in refractories becomes high. That is, the strength of the refractory may be reduced. It is more preferable to contain by 30-65 mass%.

  In the refractory of this embodiment, the particle diameter of the aggregate for refractory is not limited. The particle diameter of the aggregate for refractory is preferably 0.1 mm to 5 mm. When the particle size of the refractory aggregate falls within this range, the productivity (formability) of the refractory is improved. If the particle size is larger than 5 mm, the cohesiveness of the soil may be deteriorated, lumps may not be formed, segregation may occur, and formability may be deteriorated. That is, the formability at the time of manufacture of a refractory falls. On the other hand, when the particle size is smaller than 0.1 mm, the tenacity of the soil becomes large, the workability is lowered, and the corrosion resistance and the strength of the refractory may be lowered.

  Moreover, as for the particle size of the aggregate for refractories, it is preferable to use combining the particle | grains (aggregate aggregate particles for refractories) from which a magnitude | size differs in this preferable range. For example, coarse particles of less than 5 mm and 3 mm or more, medium particles of less than 3 mm and 1 mm or more, and fine particles of less than 1 mm and 0.1 mm or more are divided into different particle sizes and classified, and these are appropriately combined and used be able to. In addition, a particle size means the value measured according to JISR2552.

  The base material which comprises the refractory of this form disperse | distributes the aggregate for refractory. The specific configuration is not limited, and can be formed in the same manner as a conventional refractory. The substrate is preferably formed of a binder and alumina fine powder. By forming the base material to contain alumina fine powder, the main component of the base material is formed of alumina.

Moreover, the base material which comprises the refractory of this form may be either the structure which has a pore, or even if it is a dense structure with few pores. In order to ensure heat resistance spalling resistance, it is more preferable that it is the structure which has a pore.
When the substrate has pores, the specific pore characteristics (porosity, pore diameter distribution of pores, average pore diameter, etc.) are not limited. It is preferable to have the same pore characteristics as conventional refractories using a refractory aggregate.

  As the alumina fine powder, it is preferable to use alumina fine powder conventionally used in powder compositions for refractories. Alumina fine powder is strong in its own cohesion and exhibits an action of promoting hardening when the powder composition for a refractory is used as a refractory. From the viewpoint of promoting hardening of the refractory by aggregation of alumina fine powder, those having an average particle diameter (D50) of less than 10 μm can be used, and it is preferable that the alumina fine powder is less than 5 μm.

  Silica fine powder can also be added to the alumina fine powder. As the silica fine powder, it is preferable to use the silica fine powder conventionally used in powder compositions for refractories. By using alumina fine powder and silica fine powder in combination, the curing of the powder composition can be further promoted. The fine silica powder preferably has an average particle size (D50) of less than 10 μm, and more preferably less than 1 μm. Furthermore, when adding a silica fine powder, the content rate is not limited. The amount is preferably smaller than that of the alumina fine powder, and more preferably the same as the content ratio of the silica component of the aggregate for refractory.

Furthermore, carbon can be used in combination with alumina fine powder, or magnesia fine powder can be used in combination with alumina fine powder. Furthermore, when using carbon and magnesia fine powder together, the content rate is not limited. As in the prior art, the amount is preferably smaller than that of alumina fine powder.
Furthermore, in addition to the above components, antioxidants, metals for improving functional strength, and the like can be used as appropriate, as long as the effects of the present invention are not impaired.

Examples of the antioxidant include carbides such as ZrC, TiC, SiC and B ₄ C, borides such as TiB ₂ , ZrB ₂ and AlB _2, and nitrides such as AlN and Si ₃ N ₄ . As a metal which improves functional strength, Al, Si, Ni, an Al-Mg alloy, an Al-Si alloy etc. can be mentioned.

  It is preferable to use the binder conventionally used for the powder composition for refractories as a binder. The binder is not particularly limited, but it is desirable to use a thermosetting resin such as tar, phenol resin, epoxy resin, silicone resin, or furan resin.

  The refractory of this embodiment is excellent in corrosion resistance, wear resistance and heat resistance spalling resistance, and the use application thereof is not limited. For example, a sliding nozzle plate and heat-resistant brick can be mentioned. More preferably, the refractory of the present embodiment is a sliding nozzle plate.

[Plate for sliding nozzle]
The sliding nozzle plate of the present embodiment is formed by containing 10 mass% or less of the chromium component and the balance of the alumina component when the mass of the entire aggregate for refractory is 100 mass%, and the porosity is 10 It is a plate for sliding nozzles which has an aggregate for refractories which is -20%, and a base material which makes an alumina the main ingredients which distribute an aggregate for refractories. And when the mass of the whole plate for sliding nozzles is 100 mass%, the aggregate for refractories contains at 20-70 mass%.

  That is, the sliding nozzle plate of the present embodiment is a sliding nozzle plate formed of the above-described refractory material of the present embodiment. That is, the sliding nozzle plate of this embodiment exhibits the effect of becoming a sliding nozzle plate excellent in corrosion resistance, wear resistance and heat resistance spalling resistance.

  In the sliding nozzle plate of the present embodiment, the refractory aggregate preferably has a particle diameter of 0.1 to 5 mm. When the particle size of the refractory aggregate falls within this range, the productivity (formability) of the sliding nozzle plate is improved.

  Moreover, as for the particle size of the aggregate for refractories, it is preferable to use combining the particle | grains (aggregate aggregate particles for refractories) from which a magnitude | size differs in this preferable range. For example, coarse particles of less than 5 mm and 3 mm or more, medium particles of less than 3 mm and 1 mm or more, and fine particles of less than 1 mm and 0.1 mm or more are divided into different particle sizes and classified, and these are appropriately combined and used be able to.

  In the sliding nozzle plate of the present embodiment, it is preferable that the base material has pores, and carbon is introduced into the pores of the refractory aggregate and the pores of the base material. By introducing carbon into the pores of the refractory aggregate and the base material, carbon is introduced into the whole pores of the sliding nozzle plate. Then, the wettability between the sliding nozzle plate and the molten slag is reduced, and the molten slag does not infiltrate into the pores of the sliding nozzle plate. As a result, corrosion by molten slag is suppressed. That is, it leads to the improvement of corrosion resistance. In this embodiment, carbon is introduced into both the pores of the aggregate for refractory and the pores of the base material, and the corrosion resistance of the aggregate for refractory and the base material is improved.

When carbon is introduced into the pores, the inner surface of the pores of the sliding nozzle plate is coated with carbon. The carbon introduced into the pores is more preferably filled in the pores of the pores. When carbon fills the pores, the porosity of the entire sliding nozzle plate (refractory) decreases. Therefore, the strength of the sliding nozzle plate (refractory) is improved.
In the sliding nozzle plate of the present embodiment, the method of introducing carbon into the pores is not limited, and pitch impregnation described later can be used.

[Production method]
The method for producing the aggregate for refractory and the refractory (plate for sliding nozzle) of the present embodiment is not limited. For example, it can be manufactured by the following method.
As a method of producing the aggregate for refractories, a method of obtaining by crushing from a lump of sintered clinker or electrofusion clinker, a raw material prepared to have a predetermined content is dissolved in an electric arc furnace etc. Examples of such a method include a method of fine-graining with air or the like (hereinafter referred to as a melting method), and a method of atomizing and sintering the adjusted raw material.

More specifically, chromium oxide (Cr ₂ O ₃ ) powder as a chromium component, alumina (Al ₂ O ₃ ) powder as an alumina component, and silica (SiO ₂ ) powder as a silica component are prepared and mixed. At this time, the pore forming agent and optional additives may be combined and mixed. The mixed powder is compacted and heated and then sintered to produce a sintered clinker.
The mass of sintered clinker is then broken up. The crushed body can be classified to adjust the particle size. By the above, the aggregate for refractories of this form is manufactured.

In addition, as a method of manufacturing a refractory (plate for sliding nozzle), the above-mentioned respective raw materials (aggregate for refractory, fine powder of alumina and binder, further fine powder of silica, etc.) are adjusted at a predetermined ratio and then kneaded. It can be manufactured by placing it in a mold having a predetermined cavity, molding it into a predetermined shape, drying it, and heat treating it. Here, the drying temperature is desirably in the range of 100 ° C. to 300 ° C. Further, the heat treatment temperature may be non-baking at 1000 ° C. or less or baking at a temperature higher than 1000 ° C.
Furthermore, it is desirable to carry out pitch impregnation in order to introduce carbon into the pores of the refractory (plate for sliding nozzle) after heat treatment.

Hereinafter, the present invention will be more specifically described using examples.
[Examples and Comparative Examples]
Powders of high purity alumina, chromium oxide (Cr ₂ O ₃ ) and silica (SiO ₂ ) are weighed at a ratio shown in Table 1 as an aggregate for refractory, sufficiently kneaded at room temperature, and then uniaxially pressed. A block-shaped aggregate for fireproofing is obtained by baking at a temperature of 1000 ° C. or higher (sintered) after being dried at 150 ° C. for 24 hours and then sintered at a temperature of 1000 ° C. or higher. ad) got.

The porosity of the aggregate (block-like) for refractories for samples a to d was measured and is shown in Table 1. As shown in Table 1, Sample a is an alumina-chromium porous body having a porosity of 18.2%. Sample b is an alumina porous body having a porosity of 6.6%. Sample c is an alumina-chromium porous body having a porosity of 4.9%. Sample d is an alumina-chromium porous body having a porosity of 25.1%.
Moreover, the surface (cut surface) of the aggregate (block shape) for refractory materials of the sample a and the sample d was observed. According to this, it was confirmed that in the aggregate for a refractory of Sample a, fine pores were dispersed almost uniformly. On the other hand, it was confirmed that the aggregate for refractories for sample d had more pores than sample a.
Next, the manufactured block-like aggregate for refractories (samples a to d) is crushed, and coarse particles of 3 mm or more, medium particles of less than 3 mm, 1 mm or more, fine particles of less than 1 mm, 0.1 mm or more , And classified into different particle sizes of different sizes.

  Aggregates for refractory for classified samples a to d (medium particles and fine particles), alumina fine powder, and phenol resin as a binder as shown in Table 2 and compounded at normal temperature, and then 340 using a uniaxial press What was formed into a plate shape of × 190 × 40 mm was dried at 150 ° C. for about 60 minutes and then heat-treated at a temperature of 250 ° C. to 1500 ° C. to obtain a plate-like refractory. In addition, in Table 2, the alumina fine powder and the binder were shown collectively as another component.

  And pitch impregnation was performed to the obtained plate-like refractory. Specifically, after inserting a plate-like refractory into the impregnation tank, the inside of the impregnation tank is put into a vacuum state, and the heated pitch is filled into the impregnation tank. Thereafter, the inside of the impregnation tank is pressurized and held for a predetermined time, and then the inside of the impregnation tank is gradually cooled in a state where the pitch in the impregnation tank is discharged, the plate-like refractory is taken out, and the refractories of samples A to D It was created.

  The SEM photographs of the refractories of the samples A to D were taken and shown in FIGS. The sample A is shown in FIG. 1, the sample B in FIG. 2, the sample C in FIG. 3, and the sample D in FIG. FIGS. 1 to 4 are photographs of the refractories of the samples A to D subjected to the pitch impregnation process after being subjected to heat treatment and allowed to cool.

  As shown in FIGS. 1 and 3, in Samples A to D, it can be confirmed that the pitch is impregnated to the inside of the aggregate for a refractory. In particular, in the samples A (FIG. 1) and D (FIG. 4) with large porosity of the aggregate for refractories, since the contrast of the color of the aggregate for refractories and the substrate is small, for refractories It can be confirmed that the pitch is impregnated to the inside of the aggregate.

  Further, the porosity, bulk specific gravity, flexural strength and compressive strength before and after pitch impregnation of the refractories of Samples A to D were measured, and are shown in Table 3. Bulk specific gravity was calculated from apparent volume and mass, bending strength was measured based on JIS R2213, and compressive strength was measured based on JIS R2206.

  Further, FIG. 5 illustrates the relationship between the porosity of the refractory aggregate and the porosity of the refractory. FIG. 6 illustrates the relationship between the porosity of the refractory aggregate and the bulk specific gravity of the refractory. FIG. 7 illustrates the relationship between the porosity of the refractory aggregate and the bending strength of the refractory. FIG. 8 illustrates the relationship between the porosity of the refractory aggregate and the compressive strength of the refractory.

  As shown in Table 3 and FIGS. 5 to 8 (in particular, FIGS. 7 to 8), the refractories of Samples A to D are stronger in all by impregnating the pitch, compared with those not impregnated. It can confirm that it is improving. Moreover, it can be confirmed that the strength (bending strength and compressive strength) of the refractory is further improved by the porosity of the aggregate for refractory being in a predetermined range.

(Heat resistant spalling test)
Next, the heat resistant spalling test was applied to the refractories of Samples A to D. In the heat resistant spalling test, the refractories of samples A to D are formed into a block of 40 × 40 × 230 mm, inserted into a 1450 ° C. electric furnace for 20 minutes, and then air cooling cycles to room temperature are repeated, and in each cycle The Young's modulus after air cooling was measured. From the measured Young's modulus and the Young's modulus before the first heating, the rate of decrease of the Young's modulus (elastic deterioration rate) was calculated, and the measurement result in the case of repeating three cycles is shown in FIG.
As shown in FIG. 9, it can be confirmed that the heat-resistant spalling resistance is more excellent as the porosity of the aggregate for refractory is larger.

(Corrosion resistance test)
And the corrosion resistance test was done with respect to the refractory material of sample AD. The corrosion resistance test is an oxygen cleaning test on the assumption that the refractory of each sample is melted away by FeO at the time of oxygen cleaning of the sliding nozzle plate.

  In the oxygen cleaning test, first, the refractories of the samples A to D are mounted on a rotating drum. Specifically, the test pieces of the refractory of each sample are formed in a columnar shape having a trapezoidal cross section in a plane perpendicular to the axial direction. The test piece of trapezoidal cross section is fixed to the inner peripheral surface of the rotating drum over the entire circumference such that the upper base of the trapezoidal shape is located on the inner diameter side and the lower base is located on the outer diameter side. The inner circumferential surface of is coated all around. In this embodiment, the refractories of each sample are fixed to one rotating drum while changing the circumferential position.

  Then, the rotary drum was heated to a high temperature of 1750 ° C. or higher by burner heating, rotated at 10 rpm, and the inside of the rotary drum (the inner surface of the rotary drum, the upper bottom of the test piece of the refractory of the samples A to D Oxygen gas of 160 NL / min was blown into the surface at an oxygen pressure of 0.9 Mpa. Oxygen gas was blown through the iron pipe, and as soon as the iron pipe melted and shortened, it was replaced with another iron pipe and continued without interruption. The oxygen gas was blown for a total of about 8 minutes using four iron pipes. Thereafter, the corrosion resistance was evaluated. In addition, the iron pipe used the thing of 1000 mm length.

FIG. 10: is the photograph which observed the cut surface after the oxygen washing test of the refractory material of sample AD. The numerical value described in FIG. 10 is the magnitude by which each refractory was corroded in the oxygen cleaning test, comparing each refractory before the test and each refractory after the test. The smaller the value, the better the corrosion resistance.
As shown in FIG. 10, it can be confirmed that the corrosion resistance is lowered as the porosity of the refractory aggregate is increased.

  Moreover, as a result of observing the cut surface after the oxygen washing | cleaning test of the refractory material of sample AD, it can confirm that corrosion resistance is falling, so that the porosity of the aggregate for refractory materials becomes large. In particular, in sample A and sample D in which the porosity of the aggregate for refractories is large, the pitch impregnated in the pores of the aggregate for refractory is volatilized by the oxygen washing, and it becomes a state of high porosity before the impregnation treatment It is considered that the dissolution in the oxygen cleaning test has increased.

(Antioxidative wear test)
Furthermore, the oxidation resistance wear test was applied to the refractories of Samples A to D. In the oxidation resistance wear test, the refractories of the samples A to D are formed in a plate shape of 50 × 50 × 40 mm, and heated in an air atmosphere at 1000 ° C. for 2 hours using an electric furnace. It takes out from an electric furnace, and # 20 SiC particle is sprayed for 30 seconds on the surface (oxidized surface) of a plate-like refractory with a shot blasting apparatus. Before and after spraying, the worn volume (mass / bulk specific gravity) is calculated and used as the wear index. The measurement results are shown in FIG.

  As shown in FIG. 11, as the porosity of the aggregate for refractories increases, the oxidation resistance and the wear resistance are improved. This indicates that the impregnation of the pitch into the pores of the refractory aggregate is promoted and the strength is improved. However, for sample D, it is considered that there are many pores in the aggregate for refractory, and the pitch impregnated in the pores is volatilized.

As described above, a refractory using a refractory aggregate having a predetermined composition and a predetermined porosity provides a refractory excellent in corrosion resistance, wear resistance and heat resistance spalling resistance. It could be confirmed that the
This refractory has a good balance of heat resistance spalling resistance and corrosion resistance. Therefore, it is preferable to use in the steel industry such as a plate for sliding nozzles.

Claims (8)

An aggregate for a refractory, which is contained in the refractory in a state of being dispersed in a substrate,
The aggregate for a refractory is formed by containing 10 mass% or less of a chromium component and the balance of an alumina component when the total mass is 100 mass%, and the porosity is 10 to 20. Refractory aggregate characterized in%.   The aggregate for refractory according to claim 1, wherein the aggregate for refractory further contains a silica component at 20 mass% or less.   The aggregate for refractory according to claim 2, wherein the chromium oxide as the chromium component, the alumina as the alumina component, and the silica as the silica component are mixed in an atomic state or a molecular state. A refractory comprising the aggregate for a refractory according to any one of claims 1 to 3 and a base material for dispersing the aggregate for a refractory,
The refractory according to claim 1, wherein the aggregate for refractory is contained at 20 to 70 mass% when the mass of the entire refractory is 100 mass%.   The refractory according to claim 4, wherein the base material is composed mainly of alumina. A bone for a refractory comprising 10 mass% or less of a chromium component and the balance of an alumina component and having a porosity of 10 to 20% when the mass of the aggregate for the refractory is 100 mass%. Materials,
A base material formed of alumina as a main component, which disperses the refractory aggregate;
A sliding nozzle plate having
When the mass of the whole plate for sliding nozzles is 100 mass%, the aggregate for refractories contains at 20-70 mass%, The plate for sliding nozzles characterized by the above-mentioned.   The plate for a sliding nozzle according to claim 6, wherein the refractory aggregate has a particle size of 0.1 to 5 mm.   The sliding nozzle according to any one of claims 6 to 7, wherein the base material has pores, and carbon is introduced into the pores of the aggregate for refractory and the pores of the base material. Plate.