JPH07126063A - Carbon-containing basic refractory - Google Patents

Abstract

PURPOSE:To improve oxidation resistance and corrosion resistance of carbon- containing basic refractory used as containers for various molten metals. CONSTITUTION:A refractory material containing 5-30wt.% of a carbonaceous raw material and 70-95wt.% of a magnesia raw material is mixed with 0.05-5wt.% of an aluminum. magnesium.silicon alloy foil by the outer ratio to give carbon-containing basic refractory. In carbon-containing basic refractory, oxidation resistance and corrosion resistance can be improved by adding a small amount of an aluminum.magnesium.silicon alloy foil.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a basic refractory material containing carbon in the field of refractory materials.

[0002]

2. Description of the Related Art Carbon-containing refractory materials have an excellent scope of application and are rapidly expanding in recent years because they have excellent spooling properties and corrosion resistance to slag and molten metal. Among them, unfired refractories using tar pitch or phenolic resin as a binder meet the demand for energy saving, so carbon-containing refractories combined with various refractory raw materials are melted in various ways. It is used for metal containers and peripheral equipment.

Of these carbon-containing refractories, for example, a carbonaceous raw material such as scaly graphite is added to magnesia (Mg) such as a sintered magnesia clinker or an electrofused magnesia clinker.
MgO-C refractory compounded with O) quality raw material is often used for furnace walls such as converters and electric furnaces, and the life of the furnace is dramatically extended.

However, such MgO-C refractory has a low hot strength because the bond in the structure essentially depends on a carbon bond which has no bond with the oxide. It is also well known that it has a drawback that it is rapidly oxidized in a strong oxidizing atmosphere to significantly increase the dissolution rate.

[0005]

In order to improve the oxidation resistance and hot strength characteristics, which are the drawbacks of this MgO--C refractory, powders of easily oxidizable metals such as Al, Si and Mg and alloys thereof are used. or added, B ₄ C, or by adding a carbide such as SiC, or by adding a hexaboride silicon _{SiB 6, B 2 O 3 -SiO} 2 based glass phase during operation of the refractories, and B ₂ A method of coating a carbonaceous raw material with a coating of a highly viscous melt produced by the reaction of O ₃ and the refractory aggregate at a high temperature during operation has been proposed.

However, the effect of preventing the oxidation of the carbonaceous raw material by the method of adding the above-mentioned oxidizable metal or carbide is
Although there is some improvement, it is not completely satisfactory. In addition, in the method of adding silicon hexaboride, it takes time to form a stable coating with the high-viscosity melt, and depending on operating conditions, the surface of the refractory may be damaged due to melting loss or wear. Many.

Furthermore, in the addition of the metal powder, relatively coarse particles (for example, Al powder is 75
μm or less, and Al / Mg alloy powder is 250 μm or less), and as a result, a large amount of addition is necessary to obtain a good film. However, the addition of a large amount has a problem that the coefficient of expansion of the refractory material in use increases, and it has been necessary to develop a material that forms a good film with a small amount of addition.

Further, regarding the effects of Al.Mg alloy powder, Al alloy powder, and Mg alloy powder, Japanese Patent Publication No. 5234
As described in Japanese Patent Publication No. 9 and Japanese Patent Publication No. 61-303, the former is similar to the above, for example, alloy powder having a grain size of 0.5 mm or less is required.

[0009]

The present invention has been made in view of the above points, and in order to solve the above-mentioned problems, 5 to 30% by weight of a carbonaceous raw material and 70 to 9 magnesia refractory raw materials are used.
Another object of the present invention is to provide a carbon-containing basic refractory, which is obtained by adding aluminum-magnesium-silicon alloy foil in an amount of 0.05 to 5% by weight to a refractory material containing 5% by weight.

[0010]

According to the present invention, the carbonaceous raw material is 5 to 30% by weight,
A magnesia refractory raw material containing 70 to 95% by weight of aluminum, magnesium, and silicon alloy foil is added outside in a small amount of 0.05 to 5% by weight. It has an oxygen affinity higher than that of carbon and can form oxides of alumina, magnesia, silica, etc. to reinforce the inner and outer surfaces of the refractory, and improve the sparkling resistance, strength, and oxidation resistance.

[0011]

EXAMPLES The present invention will be described below based on examples. The carbon-containing basic refractory of the present invention is a carbonaceous raw material 5 to
It is characterized in that aluminum-magnesium-silicon alloy foil is externally added to 0.05 to 5% by weight to a refractory material containing 30% by weight and 70 to 95% by weight of magnesia refractory raw material.

Examples of the above carbonaceous raw materials include scaly graphite, earthy graphite, petroleum coke, coal pitch, coke,
Known materials such as foundry coke and carbon black can be used. Of these, scaly graphite is most preferred. The particle size of the carbonaceous raw material is not particularly limited and can be appropriately selected, but it is usually preferable to use a particle size of about 1 mm or less.

As the magnesia refractory material, usual clinker such as sintered magnesia clinker, electrofused magnesia and natural magnesia clinker can be used, and 70 to 9 can be used.
The blending amount is 5% by weight.

The blending amount of the carbonaceous raw material varies depending on the application target of the refractory material, but is 5 to 3 with respect to the total amount of the refractory material.
0% by weight is preferred. For example, when scaly graphite is added as a carbonaceous raw material and the scaly graphite is less than 5% by weight,
The advantages of carbon-containing refractory, such as deterioration in sponging resistance, cannot be fully exerted. Further, if the blending amount exceeds 30% by weight, the corrosion resistance decreases, which is not preferable.

Aluminum-magnesium-silicon (Al-Mg-Si) added to the above refractory material
Alloy foils show greater oxygen affinity than carbon at high temperatures,
Al ₂ O ₃ (alumina), MgO (magnesia), SiO ₂ (silica) are oxidized near the refractory surface.
As a result, it is possible to improve the sparkling resistance, strength, and oxidation resistance.

The Al / Mg / Si alloy foil has a low temperature (450
It begins to melt at around (° C.) and covers the blended carbonaceous raw material to prevent oxidation of the carbonaceous raw material.

Further, due to the expansion of the volume associated with the formation of alumina, magnesia and silica, the particle gaps near the surface formed during the molding of the refractory are almost completely closed and densified, and the mechanical strength of the refractory is increased. At the same time, the oxidation resistance can be improved. Further, SiO ₂ reacts with MgO 2MgO · SiO ₂ (forsterite), MgO reacts with _{Al 2 O 3 Al 2 O 3} · MgO ( spinel)
And other reaction products are produced to contribute to the improvement of strength.

The Al.Mg.Si alloy foil may be obtained by any manufacturing method, for example, by the atomizing method.
It can be obtained by rolling an Al.Mg.Si alloy powder having a diameter of 0.15 mm or less in an inert atmosphere.

The characteristics of the Al / Mg / Si alloy foil are as follows.
Compared with these alloy powders, the amount used can be reduced, uniform dispersion can be achieved, and the water surface coating area (specific surface area) is 1000 to 10
000 cm ² / gr is preferable, and when it is 1000 cm ² / gr or less, the characteristics as a foil cannot be obtained, and when it exceeds 10000 cm ² / gr, problems in workability, deterioration and safety occur, which is not preferable.

The amount of Al / Mg / Si alloy foil added is based on the refractory materials containing carbonaceous raw materials and magnesia refractory raw materials.
The outer weight is set to 0.05 to 5% by weight. The above addition amount is 0.
If it is less than 05% by weight, the desired effect cannot be obtained. On the other hand, if it exceeds 5% by weight, there is no problem in terms of oxidation resistance, but corrosion resistance decreases, which is not preferable. Further, the composition ratio of Si is preferably 20% or less in view of corrosion resistance.

The carbon-containing refractory material is blended with a hinder such as tar pitch or phenol resin, which has a large amount of residual carbon, that is, a high carbon yield and is excellent in workability during molding. However, the use of phenolic resin is preferable in terms of workability and cost.

[0022]

Comparative Example Next, the features of the present invention will be further clarified by comparing the examples of the present invention with the comparative examples. As shown in Table 1, the respective samples shown in Examples 1 to 6 and Comparative Examples 7 to 10 of the present invention are 60% by weight of sintered magnesia, 20% by weight of electrofused magnesia, 20% by weight of scaly graphite, and external coating of phenol resin. A refractory material containing 3% by weight and 2% by weight on the outer pitch is mixed with Al.Mg.Si in the examples as shown in the above column.
In the comparative example, the alloy foil is made of Al / Mg / Si alloy powder or Al.
A predetermined amount of each Mg alloy was added.

After kneading each for about 50 minutes at room temperature, 40 × 40 × 160 at a pressure of 1000 Kgf / cm ^2.
It is obtained by performing pressure molding into a shape of mm and heat-treating at 180 ° C. for 18 hours. The lower column of Table 1 shows the characteristics of each of the above test pieces.

As can be seen from Table 1, the numerical values such as the weight loss rate after the oxidation and calcination at 1500 ° C. for 2 hours and the thickness of the decarburized layer are relatively high in the examples of the present invention, and the oxidation resistance is high. It shows that the sex is improving.

Table 1 Comparison table of examples of the present invention and comparative examples

[Table 1]

Next, the obtained refractory material was treated with a basicity, that is, a slag having a CaO / SiO ₂ weight ratio of 2.0 to obtain 16
Subjected to a rotary slag test at 50 ° C. for 2 hours, the erosion amount of each sample was measured with the erosion amount of Comparative Example 8 being 100,
The melt loss index was calculated in the lower column of Table 1. As a result, all of the examples of the present invention showed a low melt loss index, and it can be said that the corrosion resistance to slag is extremely excellent.

As described above, in the present invention, the oxidation resistance and the corrosion resistance can be improved with a small amount as compared with the alloy powder added.

The present invention is not limited to the above-mentioned embodiments, and CaB ₆ , B may be used without departing from the spirit of the present invention.
Various modifications such as blending ₄ C or adding other additives are possible.

[0029]

As described above, according to the present invention, Al.
Since the Mg / Si alloy foil is added, the addition of a small amount of Al / Mg / Si alloy improves the strength and improves the oxidation resistance in addition to the excellent spooling resistance, which is the characteristic of conventional products. A carbon-containing basic refractory having improved durability can be obtained and can contribute to further extension of the life of the refractory wall of a furnace or the like.

Claims (1)

[Claims] 1. An aluminum / magnesium / silicon alloy foil is added 0.05 to 5% by weight to a refractory material containing 5 to 30% by weight of a carbonaceous raw material and 70 to 95% by weight of a magnesia refractory raw material. A carbon-containing basic refractory characterized by the above.