JP2002362969A - Plate brick - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plate brick which can be used for casting of molten steel of aluminum killed steel, silicon killed steel, high-oxygen steel, stainless steel, steel for electromagnetic steel sheet, calcium-treated steel, high-manganese steel, free-cutting steel, boron steel, steel cords, case-hardened steel, high-titanium steel or the like without being damaged and with sufficient durability, and which prevents the contamination of the molten steel and carbon pick-up by a refractory material and allows the stable flow rate control of the molten steel. SOLUTION: The plate brick has a composition comprising, by mass, 40 to 80% alumina, 20 to 60% magnesia and 0 to 0.8% inevitable impurity components, is composed of magnesia-alumina-based spinel free from carbon and has dynamic modulus of elasticity of >=40 GPa.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bottom plate (upper plate), a slide plate (middle plate) used for controlling a flow rate of molten steel discharged from a container such as a ladle and a tundish used in a steel making process, The present invention relates to a plate brick used in combination with three seal plates (lower plates) or two slide plates and a bottom plate.

[0002]

2. Description of the Related Art In a steelmaking process, when molten steel is injected from a ladle into an air seal pipe or a long nozzle, and / or
Alternatively, when pouring molten steel from the tundish into the immersion nozzle, a plate brick having molten steel passage holes is used for the purpose of adjusting the flow rate. Plate bricks are used by combining a plurality of pieces and sliding each other.

At present, alumina-carbon-based plate bricks mainly used in the steelmaking process receive steel grades such as high-oxygen steel, free-cutting steel, high-manganese steel, stainless steel, electrical steel sheet, and Ca-treated steel. In such a case, there is a problem that the molten steel passage hole and the sliding surface are greatly damaged, and the plate brick is short-lived.

The following patents have been disclosed in relation to such a problem. For example, JP-A-57-88073, MgO15~75 wt% as chemical components (wt%), Al ₂ O ₃ 25 to 85 wt% (mass%), balance 5% by weight (wt%) from the following Magnesia-alumina raw material 60 to 96 parts by weight (parts by mass), carbonaceous raw material 4 to 4
0 parts by weight (parts by mass), as appropriate, one or two of metal powders of silicon, aluminum, magnesium, etc., and their alloy powders
Not less than 10 parts by weight (parts by mass)
A method for producing a refractory for a sliding nozzle, comprising kneading, molding, drying and reducing and firing 15 parts by weight (parts by weight) is disclosed. According to the publication, it is described that a refractory for a sliding nozzle can be provided in which edge parts are less damaged by spalling and erosion.

Japanese Patent Application Laid-Open No. Hei 2-175068 discloses that a nozzle hole is formed of a ring made of high-purity alumina or spinel-magnesia having a ring shape, and a base material in which the ring is fitted is a ring material. There is disclosed a sliding nozzle plate formed of a material having a higher coefficient of thermal expansion. According to the publication, it is described that a highly durable sliding nozzle nozzle plate can be obtained by enhancing corrosion resistance and spalling resistance.

[0006] Further, Japanese Patent Application Laid-Open No. Hei 4-21558 discloses that
For a sliding nozzle brick, a mixture of silicon nitride and a thermosetting resin such as a phenol resin as a binder is kneaded with 2 to 10 parts by weight (parts by mass) of silicon nitride mixed with an aggregate of a refractory inorganic material. Molded body of
A sliding nozzle plate brick characterized by firing the formed body in a non-oxidizing atmosphere is disclosed. According to the publication, even when the plate brick is used under severe conditions under high heat, corrosion resistance and spalling resistance are not deteriorated, oxidation resistance and abrasion resistance are good, and melting of a sliding nozzle is performed. It is described that it can be used stably and with good durability for controlling the flow rate of metal.

[0007] Japanese Patent Publication No. 5-9385 discloses A
l ₂ O ₃ 40 to 75% by weight (mass%), MgO 25 to 60
Alumina-magnesia spinel raw material 1 having a composition of not more than 10% by weight (% by weight) and a balance of not more than 10% by weight (% by weight), and containing coarse particles having a particle size of 3 to 1 mm and fine powder having a particle size of 1 mm or less.
0-30 parts by weight (parts by weight) and MgO90 wt% (mass%) or more of magnesia feedstock 90-70 parts by weight consists of (parts by weight), Al ₂ O ₃ 10 to 25 wt% (mass%),
A refractory for a slide gate containing 90 to 75% by weight (% by mass) of MgO is disclosed. According to the publication, the peeling resistance of the slide gate refractory is improved,
It is described that it has excellent corrosion resistance and that the effect of improving the life can be obtained.

Further, Japanese Patent Application Laid-Open No. 7-308759 discloses a slide gate plate brick made of 30 to 90% by weight (% by mass) of an alumina refractory material.
l ₂ O ₃ 35 to 75% by weight (mass%), MgO 25 to 65
A slide gate plate brick using 10 to 70% by weight (% by mass) of an alumina-magnesia spinel material having a chemical composition of 1% by weight (% by mass) is disclosed. According to the publication, it is described that the spalling resistance was maintained, the corrosion resistance was significantly improved, and the product could be used more stably.

Japanese Patent Application Laid-Open No. 8-208313 discloses a sliding nozzle made of an oxide material and AlN, wherein the particle size of the AlN is 0.3 mm or less. Is disclosed. According to the publication, the refractory for a sliding nozzle plate improves the thermal shock resistance, which is a disadvantage of the conventional ceramic bond type refractory for a sliding nozzle plate, and at the same time, is higher for steel types having a high oxygen level in steel. It is described to show durability.

[0010] Further, Japanese Patent Application Laid-Open No. 9-57428 discloses that
In a sliding gate plate in which a replacement ring provided with a molten steel outflow hole is fitted into a notch formed by drilling a part of the plate body and fixed with mortar, the outer periphery of the replacement ring or a notch in the plate body Disclosed is a sliding gate plate for controlling the flow rate of molten steel, characterized in that concave portions are provided in one or both of the insides thereof and these are firmly fixed. According to the publication, the joint member filled in the concave portion formed in the exchange ring acts as an engagement member, the adhesion between the exchange ring and the plate body is securely strengthened, and despite the heavy use of the sliding gate, It is described that the occurrence of a drabble such as displacement or dropping of an exchange ring can be sufficiently prevented.

Japanese Patent Application Laid-Open No. 10-258352 discloses that a calcia-zirconia solid solution (CaO 2) is formed in a matrix portion of a basic slide nozzle whose main refractory material is magnesia-carbon or magnesia-spinel-carbon.
· ZrO ₂₎ is basic sliding nozzle, characterized by the addition of 3 to 30 wt% (wt%) are disclosed.
According to the publication, excellent corrosion resistance to high oxygen steel and high manganese steel, and also excellent heat spalling,
It is described that the occurrence of cracks in the nozzle plate is reduced and the service life is improved.

[0012]

Despite the above disclosure, the service life of the sliding nozzle has not been improved. For example, Japanese Patent Application Laid-Open No. 57-8807
The sliding nozzle obtained by the manufacturing method disclosed in Japanese Patent Publication No. 3 is one of the objects for obtaining spalling resistance, and therefore, the compounding amount of carbon is less than 4 parts by weight (parts by mass). , The effect of spalling resistance cannot be obtained. However, in the study of the present inventors, it has been found that the carbon concentration in the molten steel is extremely low, so that the carbon is rapidly dissolved in the molten steel before the refractory material reacts with the molten steel. That is, it was found that carbon in the vicinity of the operating surface of the sliding nozzle was rapidly dissolved, and the refractory structure mainly composed of spinel remaining afterwards became a structure having many pores. as a result,
The refractory material was swept away by the molten steel flow, and the damage easily proceeded from the operating surface, and it was found that the refractory for a sliding nozzle described in the publication did not provide sufficient durability.

The sliding nozzle plate described in Japanese Patent Application Laid-Open No. 2-175068 is composed of a ring and a matrix having a high coefficient of thermal expansion in which the ring is fitted.
Although the thermal stress due to the temperature gradient is reduced, the working surfaces in the ring that contact the molten steel are still damaged. This is because the material of the ring is spinel-magnesia. According to another study by the present inventors, it has been found that magnesia is damaged by a large amount of FeO or MnO generated from a dissolved element in steel or FeO or MnO as an inclusion penetrates into magnesia. . In addition, it was found that even if the spinel was plain, the spinel was similarly damaged when the amount of magnesia was increased in composition. That is, it was found that even the sliding nozzle plate described in the publication could not provide sufficient durability.

Further, JP-A-4-21558 discloses that
It is described that silicon nitride and a silicon resin are blended. However, since silicon nitride and silicon resin contain silicon and silica components, during casting of steel, it reacts with inclusions in steel and slag entrained with steel, and easily produces a low melt. Therefore, it was found that the sliding brick nozzle plate promotes erosion and abrasion of the plate, resulting in reduced service life.

[0015] The refractory for a slide gate described in Japanese Patent Publication No. 5-9385 includes 90 magnesia-based raw materials.
７０70 parts by weight (parts by mass) are used. According to the study of the present inventors, it has been found that the spalling resistance of the refractory for a slide gate is considerably inferior because a large amount of magnesia raw material having a large coefficient of thermal expansion is used. Further, during use, a composition shift occurred between a part of the magnesia raw material and the spinel raw material, and the wear resistance was significantly reduced due to deterioration of the brick structure. That is, according to this publication, the durability of the refractory for a slide gate could not be improved.

Furthermore, the plate brick for slide gate described in Japanese Patent Application Laid-Open No. 7-308759 uses 30 to 90% by weight (% by mass) of an alumina refractory material. According to the study of the present inventors, it was found that this alumina portion was preliminarily damaged by contact with molten steel. Further, during use, a composition shift occurred between a part of the alumina and the spinel, and the wear resistance was significantly reduced due to deterioration of the brick structure. That is, according to this publication, the durability improvement of the slide gate plate brick was not obtained.

JP-A-8-208313 discloses a ceramic-bonded type sliding nozzle plate refractory comprising an oxide and AlN having a particle size of 0.3 mm or less. It has been found that AlN is difficult to form a bonding structure with an oxide, so that damage is caused by an impact due to a violent molten steel flow during casting and abrasion at the time of a sliding operation, thereby lowering the service life of the sliding nozzle plate refractory.

Furthermore, the contents described in Japanese Patent Application Laid-Open No. 9-57428 are intended to prevent the displacement and the trouble of falling off of the exchange ring, and the effect is different from that of the present invention.
Further, it was found that the material applied was magnesia-spinel, so that a sufficient effect on damage was not obtained.

Japanese Patent Application Laid-Open No. Hei 10-258352 is characterized in that a calcia-zirconia solid solution is used. However, zirconia is destabilized during use, and sufficient durability is obtained due to embrittlement of the refractory structure. It turned out that it could not be obtained.

In each of the above patents, a spinel raw material is used as a part of the raw material. In general, a spinel raw material includes a raw material having a large magnesia composition and a raw material having a large alumina composition, with respect to a spinel raw material having a theoretical composition.
Depending on each raw material, there is a raw material that strongly exhibits magnesia characteristics and a raw material that strongly exhibits alumina characteristics. A raw material exhibiting a strong magnesia characteristic has a problem that the heat resistance spalling property is inferior due to the high thermal expansion coefficient of magnesia, and a raw material exhibiting a strong alumina characteristic has a problem that the corrosion resistance of the alumina is inferior. Therefore, the composition of the spinel raw material needs to be appropriately controlled. However, Japanese Patent Laid-Open No. 2-1
JP-A-75068, JP-A-4-21558, JP-A-8-208313, JP-A-9-57428, and JP-A-10-258352 do not carry out such management, No satisfactory improvements in spalling and corrosion resistance have been obtained.

As described above, no improvement in the service life of any of the plate bricks has been obtained. Generally, the sliding surface of the slide plate and the upper plate and / or the lower plate is press-bonded to prevent steel leakage from the sliding surface of the plate brick. The slide plate is slid in a direction perpendicular to the crimping force in the crimped state. Further, the plate brick is provided with a molten steel passage hole having a diameter of about several tens mm across the sliding surface, and the slide plate is slid as the molten steel passes. Actually, an operation of frequently changing the opening degree of the molten steel passage hole is performed. That is, a large static load and dynamic load are applied to the plate brick under high temperature,
In addition, the hole surface and a part of the sliding surface in contact with the molten steel are in contact with the molten steel and are in a state of being eroded. Since a high precision flow control is required for a plate brick used in such a harsh environment, a sufficient function cannot be achieved even with a slight damage. Further, since the composition of the molten steel passing therethrough is advanced and the steel is close to the final product, it is forbidden for the damaged refractory material to enter the molten steel. All of the plate bricks disclosed in the above patent publications aim at improving the service life, but the relationship between the damaged refractory material and the molten steel contamination is not clarified.
According to another study, the inventors found that damage to refractory materials was pp
It has been found that steel compositions controlled on the order of m are adversely affected. In particular, it has been found that even a small amount of refractory material in clean steel casting causes contamination of steel. In addition, it has been found that a plate brick using carbon also causes a problem of carbon pickup.

The inventors of the present invention have proposed in Japanese Patent Application No. 2000-2.
No. 08221, with respect to a composition prepared by adjusting the spinel raw material whose main component is magnesia alumina to more than 96% by mass and less than 100% by mass and the carbon raw material to less than 4% by mass (not including zero), A molded product obtained by adding a binder in a range of 1 to 15% by mass on the outer side, kneading, molding and drying, and then firing or firing without firing in a non-oxidizing atmosphere,
The sliding nozzle is characterized in that the residual carbon ratio of the molded product is in the range of 0.01% by mass to less than 4% by mass, and 100% by weight of the spinel raw material whose main component is magnesia alumina, A molded product obtained by adding a binder in a range of 1 to 15% by mass, kneading, molding and drying, and then firing or not firing in a non-oxidizing atmosphere,
A sliding nozzle characterized in that the residual carbon ratio in the compact is in the range of 0.01% by mass to less than 4% by mass has already been proposed.

However, the sliding nozzle described in Japanese Patent Application No. 2000-208221 is a brick having a brick structure formed by carbon bonding. Here, the carbon bond, as is well known to those skilled in the art, is a carbon that is produced by firing a binder interposed between the raw material particles in a non-oxidizing atmosphere to link the raw materials. The strength of the brick structure can be ensured by the carbon bond. Note that, in addition to carbon derived from the binder, carbon, graphite, and the like added as raw materials serve to suppress direct bonding (ceramic bonding) between raw materials.

Further, as described above, Japanese Patent Application No. 2000-208
The sliding nozzle described in No. 221 contains carbon, and has problems of oxidation of carbon and dissolution of carbon in molten steel. In actual equipment, in order to prevent cracking due to spalling of the sliding nozzle before use,
The temperature is raised to about 1200 ° C. to preheat. Since this preheating is performed in the atmosphere, the carbon in the sliding nozzle is oxidized during the temperature rise, and oxidation of the surface of the sliding nozzle in particular proceeds. Furthermore, if it comes into contact with molten steel during use,
Carbon dissolves in the molten steel. Japanese Patent Application 2000-208221
The sliding nozzle described in (1) suppresses the oxidation and dissolution of carbon by forming a dense layer of spinel, but it cannot completely suppress the carbon, and in the subsequent study of the present inventors, the sliding nozzle It was found that oxidation and dissolution of carbon still occurred in the vicinity of the surface. Once the carbon disappears, the carbon bond does not function, causing a problem that damage near the operating surface extremely progresses. Also, depending on the casting conditions of the actual machine, the reaction product of spinel and carbon may inhibit the formation of a dense layer of spinel on the operating surface of the sliding nozzle, escape to the outside of the sliding nozzle, and rather promote the damage of the sliding nozzle. It turned out that there is.

The present invention has been proposed in view of the above circumstances, and includes aluminum-killed steel, silicon-killed steel, high oxygen steel, stainless steel, steel for electrical steel sheets, calcium-treated steel,
When casting molten steel such as high manganese steel, free-cutting steel, boron steel, steel cord, case hardened steel, high titanium steel, etc., it is fully durable without damage, and prevents molten steel contamination and carbon pick-up due to refractory materials, and stable molten steel An object of the present invention is to provide a plate brick capable of controlling a flow rate.

[0026]

That is, the plate brick of the present invention comprises 40 to 80% by mass of alumina and 20% by mass of magnesia.
It has a composition of about 60% by mass and 8.0% by mass or less of unavoidable impurity components, is composed of magnesia-alumina spinel without carbon, and has a dynamic elastic modulus of 40 GPa or more.

Further, the plate brick of the present invention comprises at least one component selected from the group consisting of boron carbide, boron nitride, boron oxide, titanium oxide, cerium oxide, magnesium boride, and zirconium boride. It is characterized in that it is contained in an amount of 10% by mass or less (not including zero).

Further, the plate brick of the present invention is characterized in that it has been subjected to pitch or tar impregnation.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION The plate brick of the present invention adopts the following policy in order to improve the service life of the plate brick and to prevent the contamination of the molten steel: Make carbon in brick absent. In addition, a material having high erosion resistance is used for various types of molten steel. Further, a brick structure capable of suppressing wear damage due to static load and dynamic load under high temperature during use is realized. Accordingly, the reactivity of molten steel with plate bricks prepared by using various oxides, non-oxide raw materials, and carbon raw materials singly or in combination was examined. As a result, it was found that the plate brick made of magnesia-alumina spinel had the highest corrosion resistance to molten steel. It was also found that even with the same magnesia-alumina spinel, the corrosion resistance varied depending on the composition ratio of magnesia and alumina, and that a plate brick made of spinel having a specific composition ratio exhibited good corrosion resistance.

Further, in the case of a plate brick in which magnesia and / or alumina are mixed in the spinel, the composition of the plate brick is deteriorated due to the movement of the composition during use, and it is found that the combination thereof is not preferable. Plated bricks have been found to be more effective.

When the plate brick is used, at least the portion of the plate brick in contact with the molten steel needs to be ceramic-bonded. If the connection is insufficient, premature damage from the site is caused. . Further, in the carbon bonding, carbon is rapidly dissolved in the molten steel, so that the plate brick structure after carbon disappearance becomes coarse, which promotes damage to the plate brick. The present inventors have found that it is necessary to adjust the amount of fine powder of the raw material in order to obtain an appropriate ceramic bond.

Hereinafter, the plate brick of the present invention will be described in detail. The plate brick of the present invention has a composition ratio of 40 to 80% by mass of alumina, 60 to 20% by mass of magnesia, 8.0% by mass or less of unavoidable impurity components, and is composed of a magnesia-alumina spinel having no carbon. It is composed. Here, of the spinel composition ratio, the alumina composition ratio is preferably 65 to 75% by mass, and the magnesia composition ratio is preferably 25 to 75% by mass.
35 mass%, the composition ratio of the inevitable impurity component is preferably 3.0 mass% or less. The composition ratio of alumina is 40
Less than 60% by mass, that is, the composition ratio of magnesia is 60% by mass.
When the ratio exceeds, the permeation amount of FeO or MnO increases, and the plate brick is undesirably damaged. On the other hand, if the composition ratio of alumina exceeds 80% by mass, that is, the composition ratio of magnesia is less than 20% by mass, it is not preferable because damage by steel components and inclusions in steel proceeds. Furthermore,
If the ratio of the unavoidable impurity component exceeds 8.0% by mass, damage by steel components and inclusions in the steel proceeds, which is not preferable. The predicate “inevitable impurity component” described in the present specification is, for example, SiO ₂ , Fe ₂ O ₃ , CaO, Na ₂ O,
K ₂ O, ZrO _{2 and the} like are included.

The plate brick of the present invention is characterized in that substantially all of the plate brick is made of spinel. Here, the method of measuring the proportion of spinel in the plate brick is
Basically, (a) chemical analysis, (b) X-ray diffraction, (c)
(A) In chemical analysis, MgO, Al ₂ O ₃ , unavoidable impurity components, etc. can be detected and quantified, but the proportion of spinel cannot be measured; (b) X In line diffraction, mineral phases can be identified and quantified. For example, alumina present alone is corundum,
As β-Al ₂ O ₃ , magnesia can be identified as periclase and spinel separately.
X-ray peaks of corundum and periclase do not appear in the theoretical composition type spinel, but peaks of corundum and periclase also appear in the spinel with excess alumina and magnesia. In the present invention, those in which only spinel peaks appear in X-ray diffraction are defined as theoretical composition type spinels. In addition, by comparing the intensity of X-rays, the mineral phase ratio can be quantitatively examined, and by checking the quantitative results of the chemical analysis, it can be confirmed whether the spinel has a predetermined composition. (C) In EPMA analysis, elemental analysis of magnesium, aluminum, oxygen and the like can be performed. In the surface analysis by the EPMA analysis, it is possible to confirm whether or not these elements exist in the measurement region. For example, when the starting element is magnesia and alumina, and finally spinel is formed, if spinel is formed, magnesium, aluminum, and oxygen overlap and there is a region identified by EPMA. By performing the quantitative analysis by using this method, the composition ratio of MgO and Al ₂ O ₃ can be measured. By comparing the result obtained by the EPMA analysis with the quantitative result of the chemical analysis, it is possible to confirm whether the spinel has a predetermined composition. On the other hand, when no spinel is generated, the region identified by overlapping Mg and O is a periclase region, and the region identified by overlapping Al and O is a corundum or β-Al ₂ O ₃ region. It turns out that it is. In a state where spinel is partially generated and alumina and magnesia are partially present alone, those regions can be confirmed by EPMA surface analysis. For example, a portion known as a spinel region is picked up by EPMA surface analysis, the existing area of the spinel with respect to the entire area is calculated, and the spinel amount can be estimated from the bulk specific gravity of the specimen and the bulk specific gravity of the spinel.

The plate brick of the present invention is characterized in that the dynamic elastic modulus is 40 GPa or more, preferably 60 GPa or more, and optimally 80 GPa or more. Here, the predicate "dynamic elastic modulus" described in this specification
Is a method for testing the modulus of elasticity of fine ceramics (Ceramic Industry Association Editorial Committee, Lecture Subcommittee, “Mechanical Properties of Ceramics”, published by Gihodo, January 15, 1986, 5th edition, 1
90-201) and ASTM C885-78, "Method of Measuring Young's Modulus of Refractories by Sound Resonance" (Refractory Handbook (1981), published by The Refractory Technology Association of Japan), 1981
The measurement was carried out in accordance with the first printing, Jan. 31, pp. 660 to 663). The dynamic elastic modulus specified for the plate brick of the present invention is a measured value obtained at room temperature. In the case of the elastic modulus test method of fine ceramics, when the flexural resonance method is used, the test piece is cut out from a plate brick, and then the surface is ground to a length of 40 m by surface grinding.
m or more, 5 mm or more in width, 1.0 mm or more in thickness, and the length / thickness ratio of the test piece was 20 or more.
A rectangular parallelepiped test piece having a length of 40 mm or more and a length of 20 mm or more is used. Also, ASTM C
In the case of 885-78, a rectangular parallelepiped specimen having a length-to-thickness ratio of at least 3/1 is used by cutting out from a plate brick and performing surface grinding.

According to the study of the present inventors, it was found that the higher the dynamic elastic modulus, the stronger the bond between the raw material grains in the plate brick. Note that the dynamic elastic modulus is 40 G
When it is less than Pa, the bonding between grains is weak, and particularly, the abrasion resistance and the edge damage resistance are large, and it has been found that the particles cannot withstand actual use.

The plate brick of the present invention contains 10% by mass of at least one component selected from the group consisting of boron carbide, boron nitride, boron oxide, titanium oxide, cerium oxide, magnesium boride, and zirconium boride. %, Preferably 0.5 to 4% by mass. Here, if the content of these components exceeds 10% by mass, the effect of the corrosion resistance of the spinel is undesirably reduced.

The plate brick of the present invention may be subjected to pitch and tar impregnation. By impregnating pitch and tar, the thermal shock due to molten steel in the early stage of using the plate brick can be reduced.

Next, a specific example of the method for producing a plate brick of the present invention will be described. First, magnesia coexistence type spinel raw material, alumina excess type spinel raw material, theoretical composition type spinel raw material alone or in combination with a predetermined amount by combining a plurality, or mixed with alumina raw material and magnesia raw material in a predetermined amount, or If necessary, a predetermined amount of an additive is added to a raw material mixture obtained by combining a predetermined amount of the spinel raw material and the alumina raw material and / or the magnesia raw material, and then, these are added to a mixer. In addition, the said raw material may be an electrofusion raw material or a sintering raw material. The additives include aluminum, magnesium and their alloys, boron carbide, boron nitride, boron oxide, titanium oxide,
One or more selected from the group consisting of cerium oxide, magnesium boride, and zirconium boride are 10% by mass or less, preferably 0.5 to 4% by mass of the raw material mixture.
It can be used in an amount of% by weight. Additives not only increase the structural strength of the plate brick, but also as a sintering aid for spinel, as an antidigestion agent, or as a heat-resistant metal, by forming reaction products by heating during the firing of the plate brick during production. Plays an effective role in improving polling. The mixer used for kneading may be a commonly used universal mixer, Erich mixer, planetary mixer, kneader mixer, high speed mixer, omni mixer, or the like. After kneading the above components in a mixer, a predetermined amount of a binder is charged into the mixer and kneading is performed. The binder is
One or two of commonly used phenolic resins, epoxy resins, furan resins, acrylic resins, silicone resins, polyvinyl alcohol, tar, pitch, bitter, molasses, etc.
More than one species can be used in combination. The amount of the binder to be added is in the range of 0.5 to 10% by mass, preferably 1 to 5% by mass, based on 100% by mass of the composition. The kneaded product obtained as described above is then formed into a predetermined shape using a commonly used press such as an oil press or a friction press. The obtained molded body is dried at a temperature of 100 to 300 ° C. to cure the binder and / or to remove volatile components in the binder.
C., preferably at a temperature in the range of 1400 to 1700.degree. C. to remove volatile components and form a ceramic bond to obtain a plate brick.

The molded body after firing (plate brick)
If necessary, a tar or pitch impregnation treatment can be performed. The impregnation treatment can be performed by putting the fired plate brick into a tar or pitch melting tank set at a predetermined temperature in the range of 100 to 400 ° C. in advance. The impregnation treatment may be performed after the deaeration treatment for removing air. Also,
The impregnation step and the re-sintering step may be repeated a plurality of times.

It should be noted that the plate brick of the present invention is
To load the plate brick
Used in Also, the plate brick of the present invention
Into ring structure with molten steel passage hole and molten steel contact sliding surface
In addition, the ring can be used by fitting it into a base material brick.
Wear. At this time, the base material brick is made of Al which is usually used.
_TwoO_Three-C quality plate bricks and any other
Materials can be used, and the plate
Can also be used. Further, the plate brick of the present invention
Upper and lower nozzles are set above and below
However, these nozzles are made of the same material as the plate brick of the present invention.
Can also be manufactured.

[0041]

EXAMPLES Examples The raw material mixture (additive when an additive is blended) and a molasses binder (3 to 3 in the outer shell) so that the spinel finally has the chemical composition and amount shown in Tables 1 and 2. (In a range of 15% by mass) into a kneader mixer and kneaded. next,
The obtained kneaded material was molded into a predetermined shape using an oil press machine, and the obtained molded product was heated at a temperature of 200 ° C. for 24 hours.
After drying for a predetermined time, the resultant was fired at a predetermined temperature and a predetermined time in an air atmosphere (a comparative product 16 was a non-oxidizing atmosphere) for a predetermined time to obtain plate bricks of the present invention and the comparative product. The obtained inventive and comparative plate bricks were free of carbon. For the plate bricks of the present invention and the comparative product obtained as described above, those subjected to tar or pitch impregnation were further impregnated under the conditions shown in Table 1. The properties of the obtained plate brick are also shown in Tables 1 and 2.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3]

[0045]

[Table 4]

[0046]

[Table 5]

[0047]

[Table 6]

[0048]

[Table 7]

[0049]

[Table 8]

In Table 1, it was confirmed by chemical analysis, X-ray diffraction and EPMA analysis that the product of the present invention was composed of only spinel. The amount of spinel in the comparative plate brick was determined by chemical analysis, X-ray diffraction and E
It is a value estimated by the above method based on PMA analysis.

In Table 1, the dynamic elastic modulus is ASTM.
30mm x 30mm x 120m according to C885-78
It is a result measured at room temperature using a specimen having a dimension of m.
The erosion resistance index was obtained by measuring the amount of erosion when the specimen was immersed in molten steel for 30 minutes using the same steel type as the actual machine, and the erosion amount of a comparative product using the same steel type was assumed to be 100. It is shown as an index when doing. The larger the index, the more difficult it is to melt. The heat-resistant spalling property is 80
A specimen with dimensions of 80 mm x 40 mm x 1750 ° C
The acetylene torch rapidly heated and observed the state of crack occurrence, indexing the crack length, width and number of cracks, it was a problem when there was no problem in the evaluation with another actual machine It was divided into cases. An index of 80 or more indicates a case where no problem occurred, and a value of less than 80 indicates
Each case is shown below. In addition, the wear resistance and the edge damage resistance are such that three plate bricks of the actual machine shape are overlapped so that the holes penetrate, and each is stored in an iron case. The upper nozzle is joined to the lower plate, the lower nozzle is joined to the lower plate in the same way, the lower surface of the lower plate is fixed, and a load is applied downward from the upper surface of the upper plate. An experiment of controlling the burner thermal power so that the through-hole is opened and closed, the burner flame is blown from the lower part of the lower nozzle, and the temperature of the upper part of the upper nozzle is 1600 ° C. is performed for one hour while sliding in ten cycles. After the experiment, the index of damage on the sliding surface of the plate brick and edge damage around the hole are shown. An index of 100 indicates a situation without any damage, and an index of 0 indicates a case where the damage was large and the experiment was interrupted halfway. Here, in the evaluation with the actual machine, as a result of associating the wear resistance and the degree of edge damage of the plate brick at the time of casting a steel type with a small erosion, an index of 80 was obtained.
Although there is no problem in the wear resistance and the edge damage resistance in the actual machine, it was found that when the index is less than 80, the wear resistance and the edge damage resistance in the actual machine were inferior, and the bricks were discarded. The evaluation on the actual machine was carried out by simultaneously using the plate bricks of the present invention and the comparative product when actually casting the corresponding steel types shown in Table 1 at the steel mill site. That is, the product of the present invention was mounted on one strand of the tundish, and the comparative product was mounted on the other strand, and simultaneously cast and evaluated. Brick durability was evaluated as と し た when the number of charges used by the sliding nozzle was increased or could be expected to increase, Δ when the current condition was maintained, and X when decreased. In addition, the flow controllability of molten steel is indicated by ○ when stable flow control can be achieved over the entire period of the predetermined period of use of the sliding nozzle, Δ when the flow control becomes difficult, and △ when the flow can be managed. , The flow control became impossible and the use was interrupted. Further, the steel quality improvement rate indicates the degree of improvement in the defect rate of steel caused by the refractory material in percentage. In addition, the slab yield improvement rate indicates the yield improvement rate in percentage.

As can be seen from Table 1, the product of the present invention has a higher erosion resistance index, higher spalling resistance and better abrasion resistance than the comparative product, and the amount of damage to the plate brick and the brick in the actual machine. Durability, flow control of molten steel, steel quality improvement rate,
Both of the slab yield improvement rates are excellent.

[0053]

As described above, the plate brick of the present invention is free from damage, erosion and oxidation, can greatly improve the service life, and has the effect of stably controlling the flow rate of molten steel. is there. Also, because carbon is absent,
This makes it possible to cast ultra-clean steel without carbon pickup into steel and at the same time has the effect of improving the yield of slabs.

Continuing from the front page (72) Inventor Hayashi ▲ Wei ▼ 4-7-1, Kudankita, Chiyoda-ku, Tokyo Shinagawa White Brick Co., Ltd. No. 7 Inside Kawashiro Brick Co., Ltd. (72) Inventor Kasumaku 4-7, Shinagawa White Brick Co., Ltd. 4-7, Kudankita 4-chome, Chiyoda-ku, Tokyo 4G031 AA03 AA07 AA11 AA28 AA29 AA36 AA37 AA38 AA40 BA25 CA01 GA18

Claims (3)

[Claims] 1. A magnesia-alumina spinel having a composition of 40 to 80% by mass of alumina, 20 to 60% by mass of magnesia and 8.0% by mass of unavoidable impurity components, free of carbon, and dynamic. A plate brick having an elastic modulus of 40 GPa or more. 2. The method according to claim 1, further comprising boron carbide, boron nitride, boron oxide,
The plate according to claim 1, wherein the plate contains at least one component selected from the group consisting of titanium oxide, cerium oxide, magnesium boride, and zirconium boride in an amount of 10% by mass or less (excluding zero). Brick. 3. The plate brick according to claim 1, which has been subjected to pitch or tar impregnation.