JP2019127401A - Castable refractory - Google Patents

Abstract

To improve a corrosion resistance while ensuring the heat insulation in castable refractory.SOLUTION: A castable refractory of this invention contains: a sillimanite group material having a particle size of less than 1 mm; a boron compound; and at least one of a lightweight aggregate, an air entraining agent, and organic fibers. And each content of the castable refractory as a percentage of 100% by mass of raw materials excluding refractory raw materials with a particle size of 8 mm or more is as follows: the content of the sillimanite group raw material having a particle size of less than 1 mm is 5 mass% or more and 70 mass% or less; the boron compound content is 0.08 mass% or more and 2 mass% or less as the boron content; when the lightweight aggregate is contained, its content is 10 mass% or more and 50 mass% or less; when the air entraining agent is contained, its content is 0.02 mass% or more and 0.5 mass% or less; when the organic fiber is contained, its content is 0.5 mass% or more and 3 mass% or less.SELECTED DRAWING: None

Description

  The present invention relates to a monolithic refractory suitably used for the lining of a tundish receiving molten metal.

  Insulated refractories for tundish linings are required to have heat insulation in order to achieve an energy saving effect by reducing heat removal from the iron skin. On the other hand, high corrosion resistance is required on the working surface side in contact with the molten metal. That is, the characteristic which has both heat insulation and high corrosion resistance is requested | required. In addition, the characteristic provided with both heat insulation and high corrosion resistance is requested | required not only for the monolithic refractory for lining of a tundish but for the monolithic refractory for various uses.

Conventionally, there is known a technique for improving corrosion resistance by adding boron carbide (B ₄ C) (see, for example, Patent Document 1). However, Patent Document 1 does not describe specific contents for imparting heat insulation.
Further, as a technique for imparting heat insulation, a technique of adding a lightweight aggregate is known (see, for example, Patent Document 2). However, Patent Document 2 does not describe specific contents for ensuring corrosion resistance.

Japanese Patent Laid-Open No. 3-164479 JP 11-268963 A

  The problem to be solved by the present invention is to improve corrosion resistance while securing heat insulation in a monolithic refractory.

According to the present invention, the following amorphous refractories (1) to (4) are provided.
(1) A sillimanite group material having a particle size of less than 1 mm, a boron compound, and at least one of a lightweight aggregate, an air entrainer and an organic fiber,
In a proportion of 100% by mass of raw materials excluding refractory raw materials having a particle size of 8 mm or more,
The content of the sillimanite group raw material having a particle size of less than 1 mm is 5% by mass or more and 70% by mass or less, and the content of the boron compound is 0.08% by mass or more and 2% by mass or less as the amount of boron.
When the lightweight aggregate is contained, the content is 10% by mass to 50% by mass, when the air entraining agent is contained, the content is 0.02% by mass or more and 0.5% by mass or less, the organic fiber is contained The monolithic refractory whose content is 0.5 mass% or more and 3 mass% or less.
(2) The amorphous refractory according to (1), containing 5% by mass or more and 40% by mass or less of an alumina raw material having a particle size of less than 75 μm in a ratio of 100% by mass excluding the refractory raw material having a particle size of 8 mm or more. object.
(3) The light-weight aggregate is at least one of light-weight chamotte, hollow alumina, hollow spinel, vermiculite, pearlite, pumice, heat-insulated brick dust, and heat-insulating aggregate mainly composed of CaO · 6Al ₂ O _3. The monolithic refractory as described in (1) or (2).
(4) The monolithic refractory according to any one of (1) to (3), which is a monolithic refractory for tundish lining.

The amorphous refractory of the present invention can ensure heat insulation by containing at least one of a lightweight aggregate, an air entraining agent, and organic fibers. Further, by containing a sillimanite group raw material having a particle size of less than 1 mm and a boron compound, when mullite is generated from a sillimanite group raw material having a particle size of less than 1 mm, the boron compound becomes B ₂ O ₃ at a high temperature in the atmosphere, Mullite generation is promoted by improving the liquid phase ratio of the matrix portion. Due to this mullite generation promoting effect, it is possible to achieve dense and high corrosion resistance while being heat insulating.

The amorphous refractory of the present invention contains a sillimanite group raw material having a particle size of less than 1 mm, a boron compound, a light aggregate, an air entraining agent, and organic fibers.
The monolithic refractory of the present invention is a refractory material having a particle diameter of 8 mm or more, so-called large, for the purpose of preventing extension of cracks and reducing the occurrence of cracks or peeling, or enhancing corrosion resistance by dense and large aggregate. Coarse grains can also be contained. However, in the present invention, the content of each raw material other than the refractory raw material (large coarse particles) having a particle size of 8 mm or more is defined as a ratio to 100% by mass of the raw material excluding the refractory raw materials (large coarse particles) having a particle size of 8 mm or more. doing.

As the sillimanite group materials, there are three kinds of materials such as andalusite, kyanite and sillimanite, all of which are represented by a chemical formula of Al ₂ O ₃ .SiO ₂ . These sillimanite materials produce stable mullite when heated to high temperatures. Since mullite has high corrosion resistance (melting resistance), its own thermal expansion is small and it has excellent thermal shock resistance, the sillimanite group raw material is highly useful as a refractory raw material.

The production of mullite from the sillimanite group raw material is carried out by generating primary mullite by the reaction of the sillimanite group raw material represented by the following formula 1, and re-dissolving Al ₂ O ₃ in the SiO ₂ rich glass layer produced by the reaction of the formula 1. It occurs in two stages of secondary mullite formation in which mullite is generated during the precipitation process. Therefore, the present inventors have promoted the generation of mullite from the sillimanite group raw material, and in order to sufficiently exhibit the effect of improving the corrosion resistance (melting resistance) due to mullite, the secondary generated to fill the capillary through the liquid phase. We thought it important to control mullite production. Furthermore, the present inventors considered that it is necessary to increase the Al ₂ O ₃ diffusion rate in the SiO ₂ -rich glass layer generated by the primary mullite generation reaction in order to promote the generation of secondary mullite. It was found that the addition of a boron compound is effective. That is, the boron compound becomes B ₂ O ₃ at a high temperature in the atmosphere, and mullite generation is promoted by improving the liquid phase ratio of the matrix portion. By this mullite formation promoting effect, dense and high corrosion resistance can be realized. It is
3 (Al ₂ O ₃ · SiO ₂ ) = 3Al ₂ O ₃ · 2SiO ₂ + SiO ₂ Formula 1

Since such mullite formation reaction is considered to occur mainly in the matrix portion, the content of the sillimanite group material in the present invention is defined by the content of the sillimanite group material having a particle diameter of less than 1 mm constituting the matrix portion. That is, the monolithic refractory of the present invention contains 5% by mass or more and 70% by mass or less of the sillimanite group raw material having a particle size of less than 1 mm. If the content of the sillimanite group raw material having a particle diameter of less than 1 mm is less than 5% by mass, the amount of mullite produced from the sillimanite group raw material is insufficient in the first place, so that the corrosion resistance improvement effect cannot be obtained. On the other hand, when the content of the sillimanite group raw material having a particle size of less than 1 mm exceeds 70% by mass, SiO ₂ is excessively generated by the reaction of the above formula 1 and low melt is generated, so that the corrosion resistance is lowered. The preferred content of the sillimanite group material having a particle size of less than 1 mm is 20% by mass or more and 40% by mass or less.

  As described above, there are three types of raw materials of the sillimanite family, andalusite, kyanite and sillimanite, and it is preferable to use mainly andalusite in view of the thermal expansion characteristics as a refractory material. Specifically, the content of andalusite having a particle size of less than 1 mm is preferably 90% by mass or more based on 100% by mass of the total amount of the sillimanite group material having a particle size of less than 1 mm. However, since kayanite and sillimanite also produce mullite by the reaction of the above formula 1 as with andalusite, the use of kyanite and sillimanite is not excluded in the present invention.

  The amorphous refractory of the present invention can also contain a sillimanite group raw material having a particle size of 1 mm or more. Also in this case, it is preferable to use mainly andalusite. That is, it is preferable that the content of the andalusite is 90% by mass or more in the ratio of the total amount of the sillimanite group raw material to 100% by mass.

As described above, the boron compound promotes the generation of mullite from the sillimanite group raw material. Since the mullite formation promoting effect is based on the fact that the boron compound becomes B ₂ O ₃ at high temperature in the air atmosphere, the content of the boron compound in the present invention is defined by the amount of boron in the boron compound. That is, the monolithic refractory of the present invention contains the boron compound in an amount of 0.08% by mass to 2% by mass as boron. If the boron content is less than 0.08% by mass, a sufficient mullite production promoting effect cannot be obtained. On the other hand, when the amount of boron exceeds 2% by mass, B ₂ O ₃ is excessively formed to generate a low melt, so the corrosion resistance is lowered. A preferable content of the boron compound is 0.2% by mass or more and 1% by mass or less as the boron content.

Various boron compounds such as B ₄ C, ZrB ₂ , CaB ₆ , MgB ₂ , BN, etc., which become B ₂ O ₃ at high temperatures in the atmosphere (under the temperature environment of the working surface in contact with molten metals such as molten steel) Boron compounds of the following can be used, and oxides such as borosilicate glass and B ₂ O ₃ can also be used. However, since B ₂ O ₃ has a hardening delaying action, it is preferable to avoid the use when the monolithic refractory is a castable material (castable). Further, as the boron compound, the above-mentioned various boron compounds can be used in combination.

  The monolithic refractories according to the present invention contain at least one of a lightweight aggregate, an air entrainer and an organic fiber in order to ensure thermal insulation.

Examples of the lightweight aggregate include lightweight chamotte, hollow alumina, hollow spinel, vermiculite, pearlite, pumice, heat insulating brick dust, and heat insulating aggregate mainly composed of CaO · 6Al ₂ O ₃ , at least one of these Seeds can be used. When such a lightweight aggregate is contained, the content is 10% by mass or more and 50% by mass or less. The preferable content of the lightweight aggregate is 20% by mass or more and 30% by mass or less.

  The air entraining agent ensures thermal insulation by uniformly entraining a large number of independent air bubbles in the monolithic refractories when constructing the monolithic refractories, and specific examples thereof include anionic surfactant And synthetic surfactant-based foaming agents such as agents, cationic surfactants, amphoteric surfactants, nonionic surfactants, etc., resin soap-based foaming agents, hydrolyzed protein-based foaming agents and the like. When such an air entraining agent is contained, the content is set to 0.02% by mass or more and 0.5% by mass or less. A preferable content of the air entraining agent is 0.05% by mass or more and 0.1% by mass or less.

  Organic fibers ensure heat insulation by disappearing (burning down) under high temperature (under the temperature environment of the working surface in contact with molten metal such as molten steel). Specific examples include vinylon fiber, polyethylene fiber, polypropylene fiber And pulp fibers. When such an organic fiber is contained, the content is 0.5 mass% or more and 3 mass% or less. A preferable content of the organic fiber is 1% by mass or more and 2% by mass or less.

  When the contents of these lightweight aggregates, air entraining agents and organic fibers are below the lower limit values, sufficient heat insulation cannot be ensured. On the other hand, if the contents exceed the respective upper limits, the compactness of the structure is impaired and the corrosion resistance is lowered. The lightweight aggregate, the air entrainer and the organic fiber have a common action as a so-called heat insulating material, and they can be used alone or in combination. Each content is within the above-mentioned range.

  The amorphous refractory of the present invention preferably contains 5% by mass or more and 40% by mass or less of an alumina raw material having a particle size of less than 75 μm. By containing 5% by mass or more and 40% by mass or less of the alumina raw material having a particle size of less than 75 μm, the generation of the above-described secondary mullite is promoted.

In addition, the monolithic refractory of the present invention contains, as other refractory raw materials, clay raw materials, alumina-siliceous raw materials such as wax raw materials, alumina raw materials (particle diameter of 75 μm or more), silicon carbide raw materials, carbon raw materials, etc. Further, as described above, it is also possible to use a refractory material (large coarse particles) having a particle diameter of 8 mm or more. In addition, the usage-amount of a refractory raw material (large coarse grain) with a particle size of 8 mm or more shall be 40 mass% or less on the outside with respect to 100 mass% of raw materials except a refractory raw material (large coarse grain) with a particle size of 8 mm or more. Is preferred.
Furthermore, the amorphous refractory of the present invention can contain various auxiliary materials used in ordinary amorphous refractories such as various additives such as binders, dispersants, curing modifiers, and silica ultrafine powder. . In addition, the monolithic refractories referred to in the present invention are a combination of the above-mentioned various refractory materials and various auxiliary materials, and do not include water added at the time of construction.

  The monolithic refractories according to the present invention described above are suitably used as monolithic refractories for tundish linings, but the form of use thereof can be used as a cast material (castable), spray material, iron coating material, and It can also be used as a patching material.

Tables 1 and 2 show the raw material configurations and the evaluation results of the examples and comparative examples of the monolithic refractories according to the present invention. In addition, in Table 1 and Table 2, "others" are a clay raw material, a silica ultrafine powder, a dispersing agent, a hardening regulator, etc. Moreover, the refractory raw material (large coarse grain) 8 mm or more in particle size is not used for the monolithic refractory of each case.
The evaluation items and the evaluation method are as follows.

<Adiabaticity>
A predetermined amount of water was added to the monolithic refractory (raw material mixture) of each example and the mixture was kneaded and then poured into a 230 × 114 × 65 mm mold. Then, after curing at room temperature for 24 hours, drying at 110 ° C. for 24 hours, and further pre-baking at 300 ° C. for 24 hours, the thermal conductivity at a temperature of 600 ° C. was measured by a hot wire method. The temperature of 600 ° C. is representative of the temperature to which most of the area of the tundish lining except the working surface in contact with the molten steel is exposed.
In Tables 1 and 2, the thermal conductivity value of Comparative Example 1 is set to 100, and the relative value is evaluated as the thermal conductivity index. The case where the thermal conductivity index is 80 or less is ◎ (excellent), and the case is more than 80 and 90 or less. Was marked with ◯ (good) and over 90 and 100 or less with x (impossible). The smaller the heat transfer index, the better the heat insulation.

<Corrosion resistance>
A predetermined amount of water was added to the indeterminate refractory (raw material mixture) of each example, the mixture was kneaded, poured into a mold, aged and dried, and the test pieces obtained were evaluated by the rotational erosion method. The slag of the following composition was used as an eroding material. Specifically, erosion was performed for 30 minutes with 200 g of erodible material at 1600 ° C. in an air atmosphere, and then slag was taken out and 200 g of erodant was newly added to cause erosion. The slag was replaced five times every 30 minutes, and after erosion for a total of 3 hours, the maximum dissolution amount was evaluated by the dimensional change of the test pieces before and after the test. In Tables 1 and 2, the maximum erosion amount of Comparative Example 2 was set to 100, and the relative value was evaluated as the erosion index. When the erosion index was less than 90, ◎ (excellent), and 90 to less than 100. ((Good), 100 or more cases were described as x (impossible). The smaller the melting index, the better the corrosion resistance.
Slag composition CaO: 51% by mass, SiO ₂ : 15.2% by mass, FeO: 18.2% by mass,
MgO: 8.3 mass%, MnO ₂ : 5.65 mass%

<Overall evaluation>
In the evaluation of heat insulation and corrosion resistance, ◎ (excellent) when all were ◎, ◯ (good) when any one was ◯, and x (impossible) when any one was ×.

  Examples 1 to 18 shown in Table 1 are amorphous refractories within the scope of the present invention. In either case, the overall evaluation was ◎ (excellent) or ○ (good), and good results were obtained.

The comparative example 1 shown in Table 2 is an example which does not contain the material which provides what is called heat insulation, such as a lightweight aggregate, and the heat insulation was inadequate.
Comparative Example 2 is an example in which the lightweight aggregate is contained as a material for providing heat insulation, but the content is small. As in Comparative Example 1, the heat insulation was insufficient.
The comparative example 3 is an example with much content of the lightweight aggregate as a material which provides heat insulation. The compactness of the structure is impaired and the corrosion resistance is lowered.

Comparative Example 4 is an example in which the content of the sillimanite group raw material having a particle size of less than 1 mm is small. The effect of improving the corrosion resistance was not obtained because the amount of mullite formed from the sillimanite family materials is insufficient.
Comparative Example 5 is an example in which the content of the sillimanite group raw material having a particle diameter of less than 1 mm is large. Since the reaction of the above-mentioned formula 1 generated SiO ₂ in excess and a low melt was formed, the corrosion resistance was lowered.

Comparative Example 6 is an example containing no boron compound. The effect of promoting the formation of mullite by the boron compound was not obtained, and the corrosion resistance was insufficient. The comparative example 7 is an example with much content as a boron amount of a boron compound. Corrosion resistance decreased because B ₂ O ₃ was excessively formed to form a low melt.

Claims (4)

A sillimanite group material having a particle size of less than 1 mm, a boron compound, and at least one of a lightweight aggregate, an air entrainer and an organic fiber,
In a proportion of 100% by mass of raw materials excluding refractory raw materials having a particle size of 8 mm or more,
The content of the sillimanite group raw material having a particle size of less than 1 mm is 5% by mass or more and 70% by mass or less, and the content of the boron compound is 0.08% by mass or more and 2% by mass or less as the amount of boron.
When the lightweight aggregate is contained, the content is 10% by mass to 50% by mass, when the air entraining agent is contained, the content is 0.02% by mass or more and 0.5% by mass or less, the organic fiber is contained The monolithic refractory whose content is 0.5 mass% or more and 3 mass% or less.   The monolithic refractory according to claim 1, containing 5% by mass or more and 40% by mass or less of an alumina raw material having a particle size of less than 75 μm in a proportion of 100% by mass of the raw material excluding a refractory raw material having a particle size of 8 mm or more. The light-weight aggregate is at least one of heat-insulating aggregates mainly composed of light-weight chamotte, hollow alumina, hollow spinel, vermiculite, pearlite, pumice, heat-insulated brick dust, and CaO · 6Al ₂ O _3. The monolithic refractory as described in 1 or 2.   The amorphous refractory according to any one of claims 1 to 3, which is an irregular refractory for tundish lining.