JPH06287050A - Carbon-containing refractory - Google Patents

Abstract

PURPOSE:To provide carbon-containing refractory having excellent oxidation resistance and high heat strength without damaging existing characteristics of carbon-containing refractory. CONSTITUTION:A refractory raw material comprising 3-40wt.% of a carbon raw material and the rest of refractory raw material such as oxide or carbide is mixed with 0.1-8wt.% of magnesium borate by outer percentage, Metal powder such as At, Mg or Si may be used besides the refractory material.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention is used as a lining material for a melting furnace, a pot, a gutter or the like which is in direct contact with molten metal, or for continuous casting equipment such as slide valve plates, dipping nozzles, air seal pipes, stopper nozzles and the like. The present invention relates to a refractory material containing carbon.

[0002]

2. Description of the Related Art Generally, carbon-containing refractory materials are widely used as refractory materials for refining molten metal and for continuous casting.
For example, Japanese Unexamined Patent Publication No. 4-139059 discloses an unfired refractory material obtained by adding a boron powder to a carbon material or an alumina refractory raw material. The characteristics of this carbon-containing refractory are that the carbon raw material has a property that it is difficult to wet the molten metal (hot metal, molten steel, etc.) and slag, and the addition of the carbon raw material makes it possible to use other refractory materials such as oxides Since it has an effect of preventing oversintering of the refractory raw material, it has excellent corrosion resistance and spall resistance as compared with the conventional oxide refractory.

A structural feature of the carbon-containing refractory material is that the refractory material is differently bonded in addition to the carbon raw material. In other words, conventional oxide-based refractories are ceramic bonds made by sintering refractory raw materials, whereas carbon-containing refractories, as mentioned above, prevent the sintering of oxides by the added carbon raw material. Therefore, it is not a ceramic bond obtained by sintering a refractory material but a carbon bond derived from an organic binder such as pitch, which is mainly used as a binder for carbon-containing refractories, or pitch. is there.

However, carbon generally has the property of being easily oxidized to oxygen in the atmosphere. In a carbon-containing refractory used at high temperature, the carbon raw material in the refractory and the carbon component forming the carbon bond are oxidized or decarburized by oxygen in the atmosphere or oxygen in the molten metal during use. Therefore, the disappearance of the carbon component of the carbon-containing refractory, particularly the oxidation, causes the loss of the above-mentioned characteristics, that is, the corrosion resistance and the spall resistance, and also causes the brittleness and the strength reduction of the refractory, which causes wear damage.

Therefore, it is very important to prevent or suppress the oxidation of the carbon-containing refractory and increase the strength thereof in order to obtain stable and high durability of the carbon-containing refractory. Therefore, in order to improve the oxidation resistance and increase the strength of the carbon-containing refractory material, for example, by adding metal powder or the like, metal powder such as Al, Mg, Si, or Al-M.
g, utilization of alloy powder such as Al-Si, the above and B ₄ C
It has been reported that the oxidation resistance and strength are improved by the combined use of, and their effects have been confirmed.

In addition, it has been reported that the oxidation resistance of unfired refractories is improved by adding boron powder.

[0007]

However, the boron powder is very expensive, and the effect of the boron powder is that the refractory material forms boron oxide on the surface of the refractory material and forms a melt generated by the reaction with the aggregate. Although the surface is coated to prevent oxidation of the carbon raw material, the viscosity of the melt to be generated may not be sufficient depending on the temperature range, and the strength and corrosion resistance are likely to be reduced. Therefore, at present, it is not possible to use boron powder as a refractory material in terms of price, and there is a problem in that its effect is not worth the price.

In addition, in the recent usage of carbon-containing refractory materials, there are cases in which they are exposed to an oxidizing atmosphere during use more than ever before in operation, or are subjected to an oxidizing action such as contact with a molten metal having a high oxygen concentration. It has increased. Under harsh use conditions subject to a lot of such oxidizing action, the carbon-containing refractory is carbon-containing because the carbon raw material in the carbon-containing refractory and the carbon forming the carbon bond are remarkably oxidized and the brick structure becomes brittle. Increased damage to refractories and reduced durability.

Therefore, it is considered necessary to further improve the oxidation resistance and the strength in the operating temperature range in order to obtain stable high durability even under severe operating conditions.

Therefore, an object of the present invention is to provide a carbon-containing refractory having excellent oxidation resistance and high hot strength without impairing the conventional properties of the carbon-containing refractory.

[0011]

That is, the carbon-containing refractory material according to the present invention contains a carbon raw material in an amount of 3 to 40% by weight, and the balance of the carbon-containing refractory material is made of a refractory raw material such as oxide or carbide. , Magnesium boride 0.1 to 8% by weight
It is characterized by adding and blending.

Further, the carbon-containing refractory material according to the present invention contains a carbon raw material in an amount of 3 to 40% by weight, with the balance being an oxide,
Magnesium boride is applied to the refractory material made of refractory raw material such as carbide in an amount of 0.1 to 8% by weight, and Al, Mg,
It is characterized in that 1 or 10 or more kinds selected from metal powders such as Si are added / blended by external coating.

[0013]

[Function] The carbon raw material used in the above is scaly graphite,
Known carbon raw materials such as artificial graphite, carbon black, coke powder, and pitch powder can be used. The amount of the carbon raw material added is preferably 3 to 40% by weight based on the total amount of the refractory material. The reason why the addition amount is limited to the above range is that the carbon raw material is 3
If less than wt%, carbon-containing refractory slag infiltration resistance,
This is because the spall resistance is lowered, and when the amount added exceeds 40% by weight, sufficient strength cannot be obtained and wear resistance is lowered, so that the characteristics of the carbon-containing refractory cannot be obtained.

Further, examples of the refractory raw material constituting the refractory material other than the carbon raw material include oxides such as alumina, magnesia, zirconia, and spinel, and carbides such as SiC. However, the selection of the raw material forming the carbon-containing refractory must be determined depending on the intended use of the carbon-containing refractory, and the raw material is not particularly limited.

Next, magnesium boride to be added to the carbon-containing refractory material of the present invention is a raw material composed of a compound of amorphous boron and magnesium boride (Mg ₂ B ₃ ), and its main component is boron. It is magnesium.

In the present invention, the addition of magnesium boride to the carbon-containing refractory is carried out at a temperature of 1200 ° C. when magnesium boride exhibits a greater oxygen affinity than the carbon raw material at high temperature and the refractory surface comes into contact with oxygen during use. Up to the vicinity, the boron component, which is one of the main components of magnesium boride, reacts with oxygen to form boron oxide, forming a melt generated by the reaction with the aggregate and coating the refractory surface to oxidize the carbon raw material. Prevent
In the temperature range over 1200 ° C., the magnesium component, which is the main component of magnesium boride, and the boron component react with oxygen to form a highly viscous Mg—B—O melt, coating the refractory surface and coating the carbon raw material. To prevent the oxidation of. Further, by heating or firing the refractory during use to react and sinter with the refractory raw material and the carbon raw material constituting the refractory, the brick structure is made dense and excellent hot strength is obtained.

In the magnesium boride to be added, it is desirable that the molar ratio (B / Mg) of the boron component and the magnesia component is in the range of 1.5 to 8.5. Because B /
When Mg is out of the above range, the amount of boron oxide or Mg—B—O-based highly viscous melt generated by reaction with oxygen is not sufficient, and the desired effect of improving oxidation resistance can be obtained. In addition, the effect of improving the hot strength cannot be exhibited.
Further, the particle size of magnesium boride is preferably 44 μm or less in consideration of the reactivity with the refractory raw material in the brick structure.

The amount of magnesium boride added is preferably 0.1 to 8% by weight on an external basis, and if it is less than 0.1% by weight, no sufficient effect is obtained on the oxidation resistance and a strength effect is obtained. I can't. When the addition amount exceeds 8% by weight, a sufficient effect can be obtained with respect to the oxidation resistance, but the corrosion resistance is deteriorated, which is not preferable.

When a metal powder such as Al, Si or Mg is used in combination, it reacts with the carbon raw material at a high temperature to form a refractory, which strongly strengthens the strength of the brick structure and when it comes into contact with oxygen during use. It becomes an oxide, and the structure is made dense by the volume expansion accompanying the oxide formation, and the effect of the metal powder for improving the corrosion resistance is further improved.

In addition, magnesium boride and Al
The combined use of metal powder has the effect of suppressing the problem of "dandruff" of aluminum carbide generated during heating, which was a problem in addition of Al metal powder due to the densification of the brick structure by the addition of magnesium boride.

The metal powder to be added is one kind or two or more kinds selected from metal powders such as Al, Mg and Si. The total amount of metal powder added is 1 to 10% by weight, and if the addition amount is less than 1% by weight, the addition effect is small, and if it exceeds 10% by weight, corrosion resistance and spall resistance are deteriorated.

[0022]

EXAMPLES Examples are provided to describe the present invention in more detail. The magnesium boride used here is: magnesium boride: B / Mg = 8.2 (−44 μm) magnesium boride: B / Mg = 1.6 (−44 μm) magnesium boride: B / Mg = 0 .6.

Example 1 Table 1 shows the addition amount and quality of magnesium boride in the case of alumina-carbon material. In the trial production of a sample, a phenol resin was used as a binder, kneaded, formed into a normal brick, dried, embedded in coke, and reduced and baked at 1000 ° C.

[0024]

[Table 1]

As is clear from Table 1 above, the product of the present invention is superior in strength and oxidation resistance to the comparative product. Regarding the relationship between the amount of magnesium boride added and the quality, as the amount of magnesium boride added increases, the strength and oxidation resistance improve, but the corrosion resistance tends to decrease.

Example 2 Table 2 shows the quality of a slide valve plate brick in the form of a mixture of metal powder of alumina-carbon material and magnesium boride. The sample fabrication is the same as in Example 1.

[0027]

[Table 2]

When magnesium boride and metal powder are used in combination, the product 5 of the present invention is superior to the product 2 of the comparative product in corrosion resistance and in strength and oxidation resistance. Further, as to the digestion resistance, as can be seen from the comparison between the comparative product 2 and the present invention product 5, the comparative example has many large cracks on the sample surface, whereas the inventive product has no cracks on the sample surface and shows a large Improvement effect is recognized.

FIG. 1 shows the strength characteristics of the comparative product 2 and the invention product 5 at high temperature. It can be said that the product of the present invention has higher strength than the comparative example and is excellent in hot strength.

Further, the comparative product 2 and the product 5 of the present invention were subjected to pitch impregnation treatment, and as a slide valve plate brick, a steel type having a high molten steel oxygen concentration (oxygen concentration 100 to 200 p
Practical tests were conducted at Steel Works A, which has a lot of operations in pm).
As a result, the product of the present invention has a durability of about 30 as compared with the comparative product.
% Improved.

Example 3 With respect to a magnesia-carbon material, magnesium boride having different B / Mg was used to investigate the relationship between B / Mg and quality. In the trial production of a sample, a phenol resin was used as a binder, and the mixture was kneaded, molded into a normal brick, and then dried at 200 ° C. Table 3 shows the quality after 1000 ° C. reduction firing, hot strength measurement results (1400 ° C. reducing atmosphere), and oxidation test results.

[0032]

[Table 3]

The products 6 and 7 of the present invention to which magnesium boride having B / Mg = 8.2 and B / Mg = 1.6 were added are superior in strength and oxidation resistance to the comparative product 3. But,
Comparative product 4 containing magnesium boride with B / Mg = 0.6 is inferior in quality to comparative product 3.

Example 4 Table 4 shows the quality when magnesium boride was added to bricks and castings made of materials other than alumina-carbon material and magnesia-carbon material.

[0035]

[Table 4]

The sample preparation is the same as in Example 1. However, the casting materials of Comparative Product 7 and Inventive Product 10 were kneaded using a phenol resin, and then the kneaded product was poured into a metal frame, then deframed and dried, and embedded in coke.
It was reduction baked at 00 ° C. It can be seen that each material is superior to the comparative product in strength characteristics and oxidation resistance.

[0037]

INDUSTRIAL APPLICABILITY The carbon-containing refractory of the present invention, by adding and blending magnesium boride, provides further excellent oxidation resistance and high hot strength without impairing the characteristics of conventional carbon-containing refractories. be able to.

[Brief description of drawings]

FIG. 1 is a graph showing strength characteristics of a comparative product 2 and an invention product 5 at high temperature.

Claims (2)

[Claims] 1. A refractory material comprising a carbon raw material in an amount of 3 to 40% by weight and the balance being a refractory raw material such as an oxide or a carbide, and 0.1 to 8% by weight of magnesium boride in an external coating.
Carbon-containing refractory characterized by being added and compounded. 2. A refractory material comprising a carbon raw material in an amount of 3 to 40% by weight, and the balance being a refractory raw material such as an oxide or a carbide, and 0.1 to 8% by weight of magnesium boride as an outer coating, and 1 selected from metal powders such as Al, Mg and Si
A carbon-containing refractory, characterized in that 1 to 10% by weight of one or more kinds is added and compounded externally.