JP3232205B2 - Magnesia-carbon refractories - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnesia-carbon amorphous refractory excellent in strength and workability.

[0002]

2. Description of the Related Art In recent years, refractories used in metallurgical furnaces and the like have been shifting from bricks to irregular refractories for the purpose of saving labor and energy. In the case of irregular refractories, it is easy to form a jointless structure by integral construction, so it has the characteristics of less erosion of metal and slag. This is because they have characteristics that they are excellent and have a long life.

[0003] A typical example of such an amorphous refractory is a castable refractory which is kneaded with water to give an appropriate fluidity and then applied by fluid filling or the like. It is customary to add a refractory fine powder to this castable refractory in addition to a refractory aggregate and the like as a skeleton component. This is because the refractory fine powder has various useful effects such as imparting self-hardening by deflocculation-agglomeration, closing fine pores, and imparting fluidity during construction. Is one of the most important refractory materials that are indispensable.

[0004] Magnesia is one of such refractory fine powders. While this magnesia has the feature of being excellent in corrosion resistance to basic slag, it has a drawback that slag is largely penetrated and structural spall is easily generated. In addition, as such a refractory fine powder, a carbon material such as scaly graphite is used. This carbon material is known as one of the substances that improve the durability of refractories due to its high thermal conductivity, the property of being hardly wetted by molten metal and slag, and the like.
There is a disadvantage that dispersibility is poor because of showing hydrophobicity.

[0005] Recently, magnesia-carbon bricks utilizing the characteristics of magnesia and carbon (graphite) have been used as lining materials for converters and slag lines of molten steel ladle.

[0006]

However, when magnesia or carbon (graphite) is used as a raw material for a skeleton component of an amorphous refractory, there are the following problems. When used in castable refractories, magnesia has digestion problems caused by hydration reactions. In other words, this magnesia has a problem that Mg ²⁺ ions are easily eluted by reaction with water, which causes rapid aggregation of castables, impairs fluidity, and lowers workability due to solidification. There was a point. Of course, methods for solving such problems, for example, use of various cation sequestering agents, have been tried, but the actual effect has not been sufficiently improved yet. Carbon materials such as graphite are generally poor in dispersibility in water due to their hydrophobicity, and therefore, when added in large amounts to cast refractory materials, cause agglomeration. There was a drawback that it was difficult to become. In this sense, it has been conventionally difficult to add a large amount of a carbon material to an amorphous refractory.

[0007] In general, it is an important issue for a castable refractory to ensure fluidity (workability) during construction. It is well known that in order to ensure this fluidity, it is necessary to add a fine powder material. For example, magnesia
In the case of carbon-based castable refractories, fine graphite raw materials cannot be used because they are disadvantageous not only in dispersibility but also in oxidation resistance. However, this can be a temporary solution if magnesia fine powder is added. However, on the other hand, it is obvious that magnesia has high reactivity with water as described above, and cannot be used as it is because it condenses in a short time. Therefore, an object of the present invention is to propose a measure for using magnesia and carbon (carbon) as raw materials for amorphous refractories while overcoming their disadvantages while maintaining their features. In particular, it is an object of the present invention to provide a magnesia-carbon amorphous refractory excellent in workability and strength by overcoming the digestibility of magnesia fine powder.

[0008]

Means for Solving the Problems As a result of continuing intensive studies to realize the above-mentioned object, the present inventors have conducted a surface treatment for preventing hydration reaction on magnesia fine powder, thereby improving workability. It has been found that a magnesia-carbon based refractory for casting excellent in magnesia-carbon can be obtained. That is, according to the present invention, (1) a refractory raw material is mainly magnesia, and graphite is also contained. In an amorphous refractory which is used by kneading with water, graphite is used in an amount of 3 to 20% by weight and magnesia refractory material is used in an amount of 80 to 80%. 97wt%
A magnesia refractory raw material containing a surface-treated magnesia fine powder having an average particle diameter of 9 μm or less, the surface of which is subjected to a passivation treatment.
It is a carbon-based amorphous refractory. (2) In the present invention, the surface-treated magnesia fine powder used is coated with a non-hydratable substance or finely pulverized in an inert gas atmosphere. (3) The non-hydratable substance is at least one selected from alumina, hydrophilic carbon black, silica flour, and titanium oxide. (4) The amorphous refractory of the present invention is characterized in that it contains 5 to 20% by weight of a surface-treated magnesia fine powder having an average particle diameter of 9 μm or less whose surface is inactivated.

[0009]

The feature of the present invention resides in the use of surface-treated magnesia fine powder as a part of the refractory raw material. The surface-treated magnesia fine powder is prepared by treating the surface of the magnesia fine powder with a hydration reaction preventing treatment, for example, by applying a mechanical external force such as a grinding force, an impact force, or a shearing force to the surface of the magnesia fine powder to form a fine powder of alumina or hydrophilic carbon. Non-hydratable substances such as black, etc. are inactivated by compounding them.Magnesia is finely pulverized in an inert gas atmosphere such as carbon dioxide gas to inactivate the magnesia fine powder surface. There are those that have been processed. Of course, other than the surface treatment of the magnesia fine powder, other known surface treatment methods such as a method of coupling the surface may be employed. As the non-hydratable substance related to the above treatment, hydrophilic alumina, silica flour, titanium oxide or hydrophilic carbon black is used. Particularly, carbon black having hydrophilicity is used. For example, carbon black having a hydrophilicity imparted by gas-phase oxidation of 0.01 to 0.1 μm by air or oxygen or wet oxidation of sulfuric acid, potassium permanganate, or the like is advantageously used.

The amorphous refractory according to the present invention has a skeleton component composed of magnesia coarse particles, medium particles, fine particles and fine powder. In particular, as the magnesia fine powder, the surface is coated with a non-hydratable substance,
A magnesia-containing amorphous refractory using a surface-treated magnesia fine powder, such as one that has been finely pulverized and inertized in an inert gas atmosphere.
%, And 3 to 20% by weight of graphite.
In the above composition, if the content of graphite in the amorphous refractory is less than 3% by weight, the effects of graphite such as high thermal conductivity and slag resistance cannot be sufficiently obtained.
If it exceeds wt%, a dense construction body cannot be obtained. In addition, the above-mentioned surface-treated magnesia fine powder having an average particle diameter of 9 μm or less is used. If the average particle diameter is larger than this, sufficient fluidity cannot be obtained at the time of casting.
As the refractory fine powder, in addition to the surface-treated magnesia fine powder, a very small amount of general magnesia fine powder or silica fine powder may be used in combination.

FIG. 1 is a diagram showing the effect of the amount of the surface-treated magnesia fine powder and the particle size on the fluidity. The tap flow value on the vertical axis shown in this figure indicates the limit value of fluidity during castable construction.
mm or more was considered a suitable example, but from the results shown in this figure,
It is understood that the content of the surface-treated magnesia is preferably 5 to 20% by weight based on the total amount of the amorphous refractories, and the particle size is preferably 9 μm or less.

In the amorphous refractory according to the present invention, alumina cement, silica sol or alumina sol generally used for refractories is used as an auxiliary agent, for example, as a curing agent (binder) if necessary. And, as an antioxidant, use B ₄ C, SiC, Si or Al, as a dispersant,
Sodium tripolyphosphate, Sodium hexametaphosphate, Sodium ultrapolyphosphate, Sodium acid hexametaphosphate,
Inorganic salts such as sodium borate and sodium carbonate, sodium citrate, tartrate, sodium polyacrylate, sodium sulfonate and sodium naphthalenesulfonate using one or more than one selected from the group consisting of: It is preferable to use oxalic acid, citric acid, or polyacrylic acid as a curing retarder.

[0013]

This example was conducted to confirm the effects of the present invention, and the results are summarized in Table 1. The surface treated magnesias A and B in the table are examples conforming to the present invention, each showing a different surface treatment method. That is, A
Denotes a silane coupling treatment, and B denotes an alumina coating treatment. C has been subjected to a hydrophilic carbon black treatment, and has a particle size outside the applicable range of the present invention. D is a fine magnesia powder that has not been subjected to any surface treatment. A is a mixture obtained by adding a silane coupling agent, mixing and heating at 300 to 400 ° C. B shows a case where fumed silica was added and the mixture was treated with a vibration ball mill for 30 minutes. And C is Nara Machine Hybridization System NH
This was processed using an S3 type at a peripheral speed of 60 m / s for 5 minutes. Comparative Example 1 is a conventional alumina-magnesia pouring material, and Comparative Examples 2 and 3 are those using magnesia fine powder which does not satisfy the conditions of the present invention. In addition, reference numeral 4 indicates that the added amount of graphite is out of the range of the present invention.

As is clear from the results shown in Table 1, the porosity of Inventive Example 1 is slightly increased and the strength is slightly decreased as compared with the conventional product of Comparative Example 1, but the effect of graphite addition and the refractory property The improvement of corrosion resistance is remarkable by containing the surface-treated magnesia A mainly with magnesia as the conductive aggregate. In this case, the corrosion resistance index is an index when the wear dimension of the standard sample (Comparative Example 1 in this case) is set to 100. The smaller the value, the smaller the wear and the better. In Comparative Example 2, since the particle size (15 μm) of the magnesia fine powder was not in the range suitable for the present invention, the fluidity was poor, and the refractory physical properties after pouring were poor.
In Comparative Example 3, since the magnesia fine powder not subjected to the surface treatment was used, agglomeration occurred immediately after kneading, and the fluid did not flow. In Comparative Example 4, the amount of the graphite raw material was out of the range of the present invention, so that the porosity was significantly increased, and both the strength and the corrosion resistance were reduced. In contrast, any of the cast amorphous refractories according to the present invention can have improved corrosion resistance, without sacrificing other refractory properties as much. The present invention is not limited to the above embodiment, and various applications and modifications can be made within the scope of the invention.

[0015]

[Table 1]

[0016]

As described above, according to the present invention, a magnesia-containing amorphous refractory having high strength and excellent fluidity can be obtained, so that the workability at the time of pouring can be improved.

[Brief description of the drawings]

FIG. 1 is a graph showing the effect of magnesia fine powder on fluidity.

Continued on the front page (72) Inventor Masato Takagi 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Inside the Steel Research Laboratory, Kawasaki Steel Corp. (72) Inventor Junichiro Mori 1576, Higashi-oki, Aki-shi, Hyogo Prefecture 2 Inside Kawasaki Furnace Materials Co., Ltd. 2 Kawasaki Reactor Co., Ltd. (56) References JP-A-2-69349 (JP, A) JP-A-7-82027 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C04B 35/66

Claims (4)

(57) [Claims] 1. The refractory raw material is mainly magnesia,
In addition to graphite, amorphous refractories used by kneading with water contain 3 to 20% by weight of graphite, 80 to 97% by weight of magnesia refractory raw material, and the surface of some of the magnesia refractory raw materials is not included. Activated average particle size 9 μm
A magnesia-carbon amorphous refractory comprising the following surface-treated magnesia fine powder. 2. The surface-treated magnesia fine powder whose surface has been deactivated by coating with a non-hydratable substance or finely pulverizing in an inert gas atmosphere. The irregular shaped refractory described. 3. The irregular refractory according to claim 2 , wherein the non-hydratable substance is at least one selected from alumina, hydrophilic carbon black, silica flour and titanium oxide. object. 4. An average particle diameter of 9 μm whose surface is inactivated.
The amorphous refractory according to any one of claims 1 to 3 , comprising 5 to 20 wt% of a surface-treated magnesia fine powder having a particle size of m or less.