JP2023122433A - Alumina-silica castable refractory - Google Patents

Abstract

To provide an alumina-silica castable refractory excellent in durability, with the thermal expansion thereof under restraint suppressed and the peel-off wear reduced.SOLUTION: The alumina-silica castable refractory comprising an alumina refractory raw material, an alumina-silica refractory raw material, ultrafine silica powder, alumina cement and mullite, with the alumina refractory raw material of a particle diameter of smaller than 75 μm among the alumina refractory raw material, the ultrafine silica powder, and the acicular mullite of length of shorter than 75 μm constituting granules, is characterized in that the particle diameter of the granule is not smaller than 0.3 mm and not larger than 1.0 mm.SELECTED DRAWING: None

Description

The present invention relates to alumina-siliceous castable refractories.

Alumina-silica castable refractory used for lining furnace material of tundish has the problem of exfoliation wear due to cracks generated during use. Crack initiation is related to the construction of the castable refractory installation lined in the tundish. When the castable refractory material is used to line a tundish, the upper end portion of the tundish is restrained with metal fittings. This is to prevent the castable refractories applied to the side walls of the tundish from coming off during use. When the alumina-silica castable refractory is used with its upper end restrained in this way, buckling occurs due to thermal expansion of the refractory, and cracks occur.

Two methods have been investigated to prevent buckling of alumina-siliceous castable refractories during use. The first point is a method of reducing the stress generated by the thermal expansion by controlling the thermal expansion. The second point is to impart creep to the alumina-silica castable refractory in order to relax the stress generated by thermal expansion.

Patent Literature 1 discloses a castable refractory in which a mixture of andalusite and mullite is blended as an aggregate in a specified amount in order to control thermal expansion. Patent Literature 2 discloses an alumina-silica castable refractory having a specified creep amount when held at 1500° C. for 5 hours under a load of 0.2 MPa.

JP-A-5-17241 JP-A-2005-152908

However, it is difficult to say that the castable refractories described in Patent Documents 1 and 2 are sufficiently inhibited from peeling wear originating from cracks that occur during use. In the prior art, there is room for improvement in controlling thermal expansion under constraint in alumina-siliceous castable refractories.

An object of the present invention is to provide an alumina-silica castable refractory having controlled thermal expansion under restraint.

As a result of investigating the wear mechanism of the alumina-silica castable refractory used for the lining furnace material of the tundish, the present inventor found that cracks that occur in the refractory during use, which causes peeling wear, It was found that the coefficient of thermal expansion of the refractory is the cause. As a result of intensive studies by the present inventors, it was found that whether or not cracks that cause peeling loss due to buckling occur during use of alumina-silica castable refractory is determined by heating at 1500 ° C. under restraint of the refractory. The inventors have found that a refractory with a controlled coefficient of thermal expansion under restraint, which correlates with the coefficient of expansion, can reduce exfoliation wear, leading to the development of the alumina-silica castable refractory of the present invention.

That is, the gist of the present invention is as follows.
(1) Alumina refractory raw material, alumina-silica refractory raw material, ultrafine silica powder, alumina cement, and alumina-silica castable refractory containing mullite, wherein the particle size of the alumina refractory raw material is less than 75 μm , the silica ultrafine powder, and the needle-shaped mullite having a length of less than 75 μm constitute granules,
characterized in that the particle size of the granules is 0.3 mm or more and 1.0 mm or less,
Alumina-siliceous castable refractories.
(2) In the test method for the load softening point of refractory bricks in accordance with JIS R2209, the measured value of the coefficient of thermal expansion at the time of reaching 1500 ° C from room temperature is 0.5% or more and 1.0% or less. An alumina-siliceous castable refractory according to (1), characterized in that:
(3) A tundish comprising the alumina-silica castable refractory according to (1) or (2) as a lining furnace material.

The alumina-silica castable refractory of the present invention has controlled thermal expansion under restraint, exhibits less peeling loss due to cracks when used under restraint, and is extremely excellent in durability.

Fig. 4 schematically shows the configuration of the refractory lining in the cross-section of the tundish;

1. Alumina-Siliceous Castable Refractory An alumina-siliceous castable refractory according to one embodiment comprises an alumina-siliceous refractory raw material, an alumina-siliceous refractory raw material, silica ultrafine powder, alumina cement, and mullite. Here, the alumina refractory raw material having a particle size of less than 75 μm, the silica ultrafine powder, and the needle-like acicular mullite having a length of less than 75 μm constitute granules, and the granules has a particle size of 0.3 mm or more and 1.0 mm or less.

1.1 Component 1.1.1 Alumina refractory raw material As the alumina refractory raw material, for example, at least one refractory selected from the group consisting of electrofused alumina, sintered alumina, bauxite, alumina ultrafine powder, and alumina sol. Raw materials can be used. Among them, at least one refractory raw material selected from the group consisting of electrofused alumina, sintered alumina, bauxite and alumina ultrafine powder is preferred. The term "alumina ultrafine powder" as used in the present application means a particle size of 10 μm or less (at least one of the area circle equivalent diameter specified from an SEM image and the like, and the particle size determined by sieve classification). Alumina powder with The shape and size of the alumina refractory raw material are not particularly limited. However, as will be described later, the alumina-silica castable refractory essentially contains an alumina refractory raw material having a particle size of less than 75 μm as a component constituting the granules. In addition, the alumina-based refractory raw material having a particle size of less than 75 μm contained in the alumina-silica castable refractory may all constitute granules described later, or a part thereof may constitute granules. It may exist in a free state or the like. For example, 90% by mass or more of the alumina-based refractory raw material having a particle size of less than 75 μm contained in the alumina-silica castable refractory may constitute the granules described later. In addition, the alumina-silica castable refractory may contain an alumina refractory raw material having a particle size of 75 μm or more as an aggregate. The content of the alumina refractory raw material is not particularly limited. The alumina-silica castable refractory may contain an alumina refractory raw material, for example, 10% by mass or more, 15% by mass or more, 20% by mass or more, or 25% by mass or more, and 45% by mass or less, 40% by mass. or less or 35% by mass or less. 40 mass % or less is especially preferable.

1.1.2 Alumina-siliceous refractory raw material As the alumina-siliceous refractory raw material, for example, at least one of andalusite and chamotte can be used. In particular, andalusite can be used more preferably. The shape and size of the alumina-siliceous refractory raw material are not particularly limited. Also, the content of the alumina-siliceous refractory raw material is not particularly limited. The alumina-siliceous castable refractory may contain an alumina-siliceous refractory raw material, for example, 20% by mass or more, 24% by mass or more, 25% by mass or more, or 28% by mass or more, 60% by mass or less, 58 % or less or 56% by mass or less. 25 mass % or more is especially preferable.

1.1.3 Silica ultrafine powder Silica ultrafine powder includes silica flour and silica fume, which are by-produced during the production of silicon and silicon alloys, aerosol-like substances produced by the vapor phase method, and amorphous substances synthesized by the wet method. At least one silica powder selected from pure hydrous silica and its dried form can be used. The term “silica ultrafine powder” as used in the present application means a particle size of 1 μm or less (at least one of the area circle equivalent diameter specified from an SEM image, etc., and the particle size determined by sieve classification). It refers to silica powder that has Silica ultrafine powder can also function as a siliceous refractory raw material, which will be described later. The content of the ultrafine silica powder is not particularly limited. Alumina-silica castable refractory may contain silica ultrafine powder, for example, 1% by mass or more, 2% by mass or more, or 3% by mass or more, and 10% by mass or less, 7% by mass or less, or 5% by mass or less. may contain. Among them, 1% by mass or more and 5% by mass or less is preferable. In addition, the silica ultrafine powder contained in the alumina-silica castable refractory may all constitute granules described later, or a part thereof may be in a state of being isolated without constituting granules. and so on. For example, 90% by mass or more of the ultrafine silica powder contained in the alumina-siliceous castable refractory may constitute the granules described later.

1.1.4 Alumina Cement As the alumina cement, for example, an alumina cement containing CaO.Al ₂ O ₃ can be used. In addition to CaO.Al ₂ O ₃ , it is also possible to use alumina cement containing alumina or spinel. The content of alumina cement is not particularly limited. Alumina-siliceous castable refractories may contain alumina cement, for example, 1% by mass or more, 2% by mass or more, or 4% by mass or more, and 10% by mass or less, 8% by mass or less, or 6% by mass or less. You can stay. Above all, 4% by mass or more is preferable.

1.1.5 Mullite As mullite, for example, pulverized mullite fibers can be used. As will be described later, the alumina-silica castable refractory essentially contains acicular mullite having a predetermined shape as a component constituting the granules. Specifically, the acicular mullite constituting the granules has a length of less than 75 μm. "Acicular" means having a length greater than the diameter. Although the lower limit of the length is not particularly limited, it may be, for example, 25 μm or more. The diameter is also not particularly limited, but may be, for example, 5 μm or more and 7 μm or less. The length and diameter of acicular mullite can be specified by, for example, SEM observation and elemental analysis. That is, the “length” may be the maximum length in the longitudinal direction of one acicular mullite observed by SEM or the like, and the “diameter” is the maximum length of one acicular mullite observed by SEM or the like. and at least one of the maximum length in the short side direction (width direction) and the maximum value of the area circle equivalent diameter in the cross section in the short side direction. Alternatively, instead of image analysis such as SEM, the length and diameter of acicular mullite may be specified by mechanical operation such as sieving. The content of acicular mullite is not particularly limited. The alumina-siliceous castable refractory may contain, for example, 5% by mass or more, 7% by mass or more, or 10% by mass or more, and 40% by mass or less, 35% by mass or less, of acicular mullite having a length of less than 75 μm. Alternatively, it may contain 30% by mass or less. Among them, 10% by mass or more and 30% by mass or less is preferable. The acicular mullite having a length of less than 75 μm contained in the alumina-silica castable refractory may entirely constitute the granules described later, or a part thereof may constitute the granules. It may exist in a free state or the like. For example, 90% by mass or more of acicular mullite having a length of less than 75 μm contained in the alumina-silica castable refractory may constitute granules described later.

1.1.6 Other Components The alumina-siliceous castable refractory may contain components other than those described above. For example, the alumina-siliceous castable refractory may contain a siliceous refractory raw material other than the ultrafine silica powder described above. Examples of siliceous refractory raw materials other than ultrafine silica powder include quartz, fused silica, crushed particles of unused or used silica bricks, and the like. The alumina-siliceous castable refractory may contain, for example, 10% by mass or less of a siliceous refractory raw material other than ultrafine silica powder.

In addition to acicular mullite having a length of less than 75 μm, the alumina-silica castable refractory may contain other mullite (other mullite) as long as the desired effect is exhibited. The desired effect is achieved whether or not other mullite is present. In the alumina-siliceous castable refractory, the content of other mullite may be, for example, 10% by mass or less, 5% by mass or less, or 1% by mass or less.

The alumina-siliceous castable refractories may also contain components derived from various additives such as dispersants and explosion inhibitors.

Commonly used dispersants may be used. For example, sodium tripolyphosphate, sodium hexametaphosphate, acidic sodium hexametaphosphate, sodium polyacrylate, sodium polycarboxylate, sodium sulfonate, sodium naphthalenesulfonate, sodium lignosulfonate, sodium ultrapolyphosphate, sodium carbonate, sodium borate, Sodium citrate or the like can be used.

As the explosion prevention agent, one commonly used may be used. For example, vinylon fiber, aluminum lactate, metallic aluminum as a foaming agent, azodicarbonamide, and the like can be used.

1.2 Thermal expansion coefficient The alumina-silica castable refractory according to the present embodiment is tested in a test method for the softening point under load of a refractory brick in accordance with JIS R2209. The measured value of the thermal expansion coefficient of can be 0.5% or more and 1.0% or less. This makes the crack resistance even more excellent.

1.2.1 Chemical reaction affecting thermal expansion coefficient In the process of heating alumina-silica castable refractories to 1500°C while applying a pressure of 0.2 MPa, for example, the following reactions occur. Become.
Andalusite → Mullite + Liquid phase (1) Formula Alumina + Silica → Mullite (2) Formula

In equation (1), the alumina-silica castable refractory shrinks due to the capillary force of the generated liquid phase, and in equation (2), the refractory expands due to volumetric expansion that accompanies mullite formation. Therefore, the thermal expansion coefficient at the time of reaching 1500 ° C. from room temperature in the test method for the load softening point of refractory bricks in accordance with JIS R2209 for alumina-silica castable refractories is the refractory raw material itself that constitutes the refractory. In addition to the thermal expansion, it represents the result of superimposing the contraction by the above formula (1) and the expansion by the formula (2).

If the measured value of the coefficient of thermal expansion is less than 0.5%, it is determined that the amount of liquid phase generated has increased due to the reaction of formula (1) above. Cracks do not occur when molten metal such as molten steel is present in the tundish, ie when the alumina-siliceous castable refractory is heated. However, when there is no molten metal such as molten steel in the tundish, that is, when the alumina-silica castable refractory is cooled, the refractory shrinks excessively due to volumetric shrinkage during solidification of the liquid phase. , cracks will occur.

If the measured value of the coefficient of thermal expansion exceeds 1.0%, it is judged that the reaction of the above formula (2) has been accelerated. That is, due to the reaction of formula (2) above, the thermal expansion of the alumina-silica castable refractory increases, and cracking occurs due to buckling.

In other words, in order to define the coefficient of thermal expansion under restraint in alumina-silica castable refractories composed of alumina refractory raw material, alumina-silica refractory raw material, siliceous refractory raw material, and alumina cement, alumina-silica Since the reaction of andalusite, which is a type of refractory raw material, is unavoidable in the above formula (1), it is important to control the formation of mullite by the reaction of alumina and silica in the above formula (2).

1.2.2 Form for controlling the coefficient of thermal expansion resulting from the reaction of the above formula (2) Fine powder and acicular mullite having a length of less than 75 μm (preferably less than 75 μm in length and a diameter of 5 μm or more and 7 μm or less) constitute the granules, so that the reaction between alumina and silica in the above formula (2) can control the formation of mullite by

The reason why the maximum particle size of the alumina refractory raw material used for granulation is less than 75 μm is to control the reaction with silica in the above formula (2). If the maximum particle size of the alumina refractory raw material is less than 75 μm, the reaction with silica in the above formula (2) is likely to be promoted. By granulating such a highly reactive alumina refractory raw material together with ultrafine silica powder, the reaction of the above formula (2) proceeds appropriately, and the measured value of the coefficient of thermal expansion under restraint is 0.00. It becomes easy to control to 5% or more and 1.0% or less. Although the lower limit of the particle size of the alumina refractory raw material constituting the granules is not particularly limited, it is preferably 25 μm or more. On the other hand, if the maximum particle size of the alumina refractory raw material is too large, the reaction with silica in the above formula (2) does not proceed, and as a result, the expansion accompanying the reaction does not occur, resulting from the reaction of the above formula (1). Due to the unavoidable only shrinkage occurring, the measured value of the coefficient of thermal expansion under restraint is likely to be less than 0.5%.

At the time of granulation, acicular mullite with a length of less than 75 μm (preferably less than 75 μm in length and a diameter of 5 μm or more and 7 μm or less) is used in combination with an alumina refractory raw material having a maximum particle size of less than 75 μm and silica. This is because the formation of mullite due to the reaction with the fine powder is promoted, and the expansion is effectively developed. Alumina and silica react at a high temperature to precipitate mullite crystals from the resulting liquid phase, but since a large amount of energy is required to generate mullite crystal nuclei, mullite precipitation does not occur easily. . If acicular mullite having a length of less than 75 μm (preferably less than 75 μm in length and a diameter of 5 μm or more and 7 μm or less) exists in the vicinity of the reaction point between alumina and silica, mullite is formed by the reaction between alumina and silica. Precipitation as well as mullite growth occurs readily. As a result, the reaction of formula (2) proceeds appropriately, and the measured value of the thermal expansion coefficient under restraint is easily controlled to 0.5% or more and 1.0% or less. In the case of granular mullite having a particle size of 5 μm or more and 7 μm or less, mullite is not generated or grown to the extent that expansion is effectively exhibited. In this regard, rather than "granular" mullite, it is necessary to use "acicular" mullite having a certain length as described above. On the other hand, if the acicular mullite is too long, it becomes a steric hindrance and tends to hinder the formation of mullite through the reaction between the alumina refractory raw material having a maximum particle size of less than 75 μm and the ultrafine silica powder. As a result, the reaction of the above formula (2) does not proceed sufficiently, and only the reaction of the above formula (1) inevitably occurs, causing shrinkage, and the measured value of the thermal expansion coefficient under restraint is 0.0. It tends to be less than 5%.

1.2.3 Granulation method An alumina refractory raw material with a particle size of less than 75 μm, ultrafine silica powder, and acicular mullite with a length of less than 75 μm (preferably, a length of less than 75 μm and a diameter of 5 μm or more and 7 μm or less) are As a granulation method, a dry high-speed mixing method or a wet mixing method can be used.

In the wet mixing method, an alumina refractory raw material with a particle size of less than 75 μm, ultrafine silica powder, and acicular mullite with a length of less than 75 μm (preferably, a length of less than 75 μm and a diameter of 5 μm or more and 7 μm or less) are For example, a mixer is charged and mixed, and a resin material such as an epoxy resin, a furan resin, or a phenolic resin diluted with an organic solvent is added during stirring to form granules by chemical bonding force. You can create things.

1.2.4 Size of granules Alumina refractory raw material with a particle size of less than 75 μm, ultrafine silica powder, and needles with a length of less than 75 μm (preferably, a length of less than 75 μm and a diameter of 5 μm or more and 7 μm or less) The granules composed of shaped mullite have a particle size of 0.3 mm or more and 1.0 mm or less. Having such a particle size helps control the volume expansion that accompanies the formation of mullite. If the particle size of the granules is too small, too little volume expansion will accompany the formation of mullite. On the other hand, if the particle size of the granules is too large, the accompanying volume expansion during mullite formation will be excessive. In addition, in this application, the particle size of the granules can be measured, for example, as follows. That is, the alumina-silica castable refractory is observed with an SEM or the like to observe the shape of particles contained in the refractory, and the granules contained in the observed image are specified by elemental analysis such as EDX. The area of the identified granules is converted into a circle, and the particle size of the granules is identified as the "area circle equivalent diameter". Alternatively, the particle size may be selected by sieve classification at the raw material stage.

1.3 Supplement The reason why the coefficient of thermal expansion under restraint of the alumina-silica castable refractory is measured by the test method for softening point under load of refractory bricks in accordance with JIS R2209 is as follows.

The test method for the load softening point of refractory bricks described in JIS R2209 is to heat the refractory bricks from room temperature to a predetermined temperature while applying a pressure of 0.2 MPa, and heat at that temperature for a predetermined time. It is a method of measuring the thermal expansion of This is because the pressure of 0.2 MPa applied to the alumina-silica castable refractory is appropriate as a representative value of the constraint conditions for the alumina-silica castable refractory in use. If the applied pressure is too small, the restraint conditions are weak, and the coefficient of thermal expansion of the refractory is overmeasured. The coefficient of thermal expansion is undermeasured, and the crack resistance of the refractory cannot be evaluated accurately.

The measurement temperature of the coefficient of thermal expansion of the alumina-silica castable refractory under a pressure of 0.2 MPa is 1500 ° C., because it is appropriate as a representative value of the temperature to which the refractory is exposed during use. is. If the measurement temperature is too low or too high, the coefficient of thermal expansion of the refractory in use cannot be accurately measured, and the crack resistance of the refractory cannot be evaluated accurately.

2. Method for producing alumina-siliceous castable refractory The alumina-siliceous castable refractory can be produced, for example, by the following production method. That is, the method for producing an alumina-siliceous castable refractory according to one embodiment includes:
First step: granulating an alumina refractory raw material with a particle size of less than 75 μm, ultrafine silica powder, and acicular bright with a length of less than 75 μm (preferably, a length of less than 75 μm and a diameter of 5 μm or more and 7 μm or less). to obtain granules, and
Second step: mixing an alumina refractory raw material, an alumina siliceous refractory raw material, alumina cement, and the granules;
may include.

The first step is as described above. About the 2nd process, what is necessary is just to mix by a general method. A specific mixing method may be appropriately selected according to the conditions at the time of construction. For example, 5 to 8% by mass of water is added to 100% by mass of the castable refractory that satisfies the above composition, kneaded with a mixer and poured into a mold to produce refractories molded into various shapes. You may Vibration may be applied to the mold into which the kneaded material is poured in order to improve the filling property during production.

3. Application Example The alumina-silica castable refractory according to the present embodiment has controlled thermal expansion under restraint, and when used under restraint, has little peeling loss due to cracks and is extremely excellent in durability. There are various applications in which such characteristics can be utilized, and lining furnace materials for tundishes are particularly suitable. That is, the technology of the present disclosure also has an aspect as a tundish having the alumina-silica castable refractory as a lining furnace material. FIG. 1 schematically illustrates the configuration of the refractory lining in cross section of a tundish 10 according to one embodiment. As shown in FIG. 1, the tundish 10 includes a hardware 1 as an outer frame, a permanent refractory 2 covering at least part of the inner wall of the hardware 1, and a lining covering at least part of the surface of the permanent refractory 2. It may comprise a furnace material 3 and a coating material 4 covering at least part of the surface of the lining furnace material 3 . Here, as shown in FIG. 1, the lining furnace material 3 can be restrained by the hardware 1 at its upper end portion. When the lining furnace material 3 is made of the above alumina-silica castable refractory, the thermal expansion under restraint is controlled, and peeling loss caused by cracks is easily suppressed. As for the hardware 1, the perm refractory 2 and the coating material 4, conventionally known ones may be adopted, and the shape of each may be appropriately determined according to the shape of the tundish 10 and the like.

EXAMPLES The present invention will be further described below with reference to examples, but the present invention is not limited to the following examples.

Table 1 shows raw material blends and evaluation results of alumina-silica castable refractories. Water is added to 100% by mass of the castable refractory produced with the formulation in Table 1 in the range of 5 to 8% by mass, and kneaded for 3 minutes using a twin-screw mixer to form a kneaded product of a predetermined size. It was poured into the metal frame while giving it vibration. Then, after aging at room temperature for 24 hours, it was dried at 110° C. for 24 hours to prepare an evaluation sample. Comparative Example 1 is an example produced by simulating the alumina-silica castable refractory disclosed in Patent Document 1 (JP-A-5-17241), and Comparative Example 2 is Patent Document 2 (JP-A-2005-152908 This is an example produced by simulating the alumina-silica castable refractory disclosed in JP-A-2003-120000.

Acicular mullite with a length of less than 75 μm is obtained by pulverizing Mitsubishi Chemical Corp. mullite fiber (5 μm or more and 7 μm or less in diameter) and passing through a sieve with an opening of 75 μm (length less than 75 μm) or not passing through. (75 μm or more in length) were used. In this example, it was confirmed that acicular mullite having a length of 75 μm or more did not substantially pass through a sieve with an opening of 75 μm.

The granulation of the alumina refractory raw material with a particle size of less than 75 μm, ultrafine silica powder, and acicular mullite with a length of less than 75 μm was performed using a wet mixing method. Specifically, an alumina refractory raw material having a particle size of less than 75 μm, ultrafine silica powder, and acicular mullite having a length of less than 75 μm and a diameter of 5 μm or more and 7 μm or less are mixed and stirred using a proshare mixer. Granulation was carried out by adding a phenolic resin diluted 1/1000 with an ethylene glycol solution. The obtained granules are sieved to separate granules having a particle size of less than 0.3 mm, granules having a particle size of 0.3 mm or more and 1.0 mm or less, and particles having a particle size of more than 1.0 mm. of granules were obtained.

The coefficient of thermal expansion at 1500° C. under restraint of the alumina-silica castable refractory was measured according to the method for testing the softening point under load of refractory bricks specified in JIS R2209.

The amount of creep at 1500° C. of the alumina-silica castable refractories was measured according to the test method for softening point under load of refractory bricks specified in JIS R2209. The creep amount was calculated by subtracting the coefficient of thermal expansion after 5 hours at 1500°C from the coefficient of thermal expansion when reaching 1500°C.

The unrestrained thermal expansion coefficient of the alumina-silica castable refractories was measured according to the test method for thermal expansion of refractories specified in JIS-R2207.

On the other hand, to confirm the presence or absence of peeling wear caused by cracks in the alumina-silica castable refractory during actual use, the alumina-silica castable refractory having the blending ratio of each example in Table 1 is 100% by mass, Add water in the range of 5 to 8% by mass in an outer hook, knead for 3 minutes using a twin-screw mixer, construct the kneaded product as a lining furnace material for a tundish with a capacity of 70 tons, and rotate this tundish 400 times ( ch) After repeated use, the surface of the refractory applied to the side wall of the tundish was visually observed.

As shown in Table 1, the castable refractories of Examples 1 to 5 were granulated with an alumina refractory raw material with a particle size of less than 75 μm, silica ultrafine powder, and acicular mullite with a length of less than 75 μm, and Since the particle size of the granules is 0.3 mm or more and 1.0 mm or less, the volume expansion associated with the formation of mullite can be controlled. As a result, the thermal expansion coefficient at 1500 ° C. It was in the range of 1.0%, and it was demonstrated that peeling loss caused by cracks did not occur even when used in an actual machine.

In Comparative Examples 1 and 2, acicular mullite having a length of less than 75 μm was not blended, nor was it granulated. was

In Comparative Example 3, since the length of the acicular mullite used was 75 μm or more, the coefficient of thermal expansion at 1500° C. under restraint was less than 0.5%. Delamination wear had occurred.

In Comparative Example 4, since the grain size of the granules was less than 0.3 mm, the volume expansion accompanying the formation of mullite was too small, and the thermal expansion coefficient at 1500°C under restraint was less than 0.5%. As a result, when actually used in an actual machine, peeling wear caused by cracks occurred.

In Comparative Example 5, since the particle size of the granules was more than 1 mm, the volume expansion accompanying the generation of mullite was excessive, and the coefficient of thermal expansion at 1500°C under restraint was more than 1.0%. As a result, when actually used in an actual machine, peeling wear caused by cracks occurred.

According to the present invention, it is possible to manufacture an alumina-silica castable refractory with extremely excellent durability and an actual machine (for example, a tundish) using the castable refractory.

1 hardware 2 permanent refractory 3 lining furnace material 4 coating material 10 tundish

Claims (3)

An alumina-siliceous castable refractory comprising an alumina-siliceous refractory raw material, an alumina-siliceous refractory raw material, silica ultrafine powder, alumina cement, and mullite,
Granules are composed of the alumina refractory raw material having a particle size of less than 75 μm, the silica ultrafine powder, and the needle-shaped mullite having a length of less than 75 μm,
characterized in that the particle size of the granules is 0.3 mm or more and 1.0 mm or less,
Alumina-siliceous castable refractories. In a method for testing the softening point under load of refractory bricks according to JIS R2209, the measured value of the coefficient of thermal expansion at the time of reaching 1500 ° C. from room temperature is 0.5% or more and 1.0% or less. ,
The alumina-siliceous castable refractory according to claim 1. Equipped with the alumina-silica castable refractory according to claim 1 or 2 as a lining furnace material,
tundish.

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