JPH01308860A - Carbon-containing refractory - Google Patents

Abstract

PURPOSE:To improve oxidation resistance, spalling resistance, hot strength, wear resistance, corrosion resistance, etc., by blending a carbon-containing refractory material having a specific composition with Al, MgAl alloy and Si in a specific ratio. CONSTITUTION:100 pts.wt. mixture comprising (A) 3-50wt.% carbon material (preferably scaly graphite having low impurity content and <= about 3mm, preferably <= about 1mm particle size), (B) 0.5-15wt.% silicon carbide (preferably one having <=125mum particle size and (C) an amount (96.5-35wt.%) left after removal of the components A and B of a noncarbon-based refractory material (preferably one consisting essentially of magnesia, spinel, alumina, etc., having <=about 5mm particle size) is blended with <=15 pts.wt. total amounts of 0.5-10 pts.wt. Al, 0.5-10 pts.wt. Mg-Al alloy (30-70%wt.% Al and 0.5-1.5 weight ratio of Al/Mg) and 0.5-10 pts.wt. Si to give a carbon-containing refractory.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a novel carbon-containing refractory.

In addition, in this specification, "part" and "%" mean
"% by weight" and "parts by weight" respectively.

BACKGROUND OF THE INVENTION Refractories containing carbon materials are widely used as refractories for metallurgy, and exhibit extremely high resistance to chemical attack by hot metal, molten steel, slag, and the like. This is mainly due to the fact that carbon itself is particularly difficult to wet with slag, and therefore the intrusion of slag into the refractory is suppressed. Further, due to the presence of the carbon component, the refractory is not oversintered, so thermal spalling is less likely to occur, which also contributes to increasing the durability of the refractory.

However, the carbon component is oxidizing gas (0
2, CO2, etc.), so the excellent properties of carbon-containing refractories are gradually lost.

Therefore, in order to improve the durability of carbon-containing refractories over a long period of time, it is important to prevent oxidation of the carbon component as much as possible, but satisfactory results have not yet been obtained.

For the purpose of preventing oxidation of carbon-containing refractories, for example,
5-107749 discloses a carbon-containing refractory to which Mg powder, Aρ powder and Si powder are added, and JP-A-54-39422 discloses a carbon-containing refractory containing AΩ, Si, which has a greater affinity for oxygen than carbon. discloses a carbon-containing refractory to which at least one powder of metals consisting of Cr and Mg is added. However, these carbon-containing refractories have not yet fully satisfied both oxidation resistance and hot strength properties.

Furthermore, Japanese Patent Publication No. 61-52100 discloses that Aρ-Mg
discloses a carbon-containing refractory containing boron carbide and one or more alloy powders of AΩ-Mg-8i and AΩ-Mg-Cr. However, boron oxide, which is formed by oxidizing boron carbide according to the following formula (1), has a melting point of 5.
Since the temperature is as low as 77°C, there is a risk that a low melting point liquid phase will be generated within the refractory structure, significantly reducing the corrosion resistance of the refractory.

(1): B, C+402→2 B203 + C02 Furthermore, as is clear from Table 1 below, boron carbide is more easily oxidized than silicon carbide, and the weight increase rate due to oxidation at 1200°C (61, 8%) is significantly higher than that of silicon carbide (5.0%), which also causes a significant decrease in corrosion resistance.

Means for Solving the Problems As a result of repeated research in view of the current state of technology as described above, the present inventor has found that Al, MgA
It has been found that the problems of the prior art can be greatly alleviated if the I alloy and Si are blended in specific proportions.

That is, the present invention provides the following carbon-containing refractory: "A mixture consisting of 3 to 50% carbon material, 0.5 to 15% silicon carbide, and 96.5 to 35% non-carbon refractory material." 10
0 parts of AΩ, Mg-Aρ gold alloy, and Si are added to 0 parts, respectively.
A carbon-containing refractory compounded in a proportion of 5 to 10 parts and a total amount of 15 parts or less. ” In the research process leading to the completion of the present invention, the present inventor investigated the oxidation behavior of various metals, alloys, carbides, etc.

Among them, the oxidation behavior of the materials related to the present invention is shown in Table 1.

From the results shown in Table 1, the following points are clear.

Mg-Aρ gold alloy, starts to oxidize at 480℃, 1200℃
℃, a weight increase of 76.9% is observed. That is,
Mg-A! The Q alloy begins to combine with oxygen in the atmosphere at fairly low temperatures, reducing the oxygen concentration. and,
The generated oxide (M g O, A !2203) reacts with impurities in the refractory to form a glass phase and coat the carbon component, so it is effective in preventing oxidation of the carbon component, especially in low temperature ranges. do.

On the other hand, AQ, Si, and SiC have higher oxidation initiation temperatures than the Mg-Aρ gold alloy, and the weight increase at 1 200'C is 10.6%, 6.0%, and 5.0%, respectively.
Although it is quite low, it is still effective in preventing the oxidation of carbon components due to their own oxidation at relatively high temperatures.

Mg-Af;! The alloy, AQ, and Si exhibit the following effects in addition to the above-mentioned effect of preventing oxidation of the carbon component due to their own oxidation.

Mg-Aρ gold alloy from around 600℃, and AQ is 750
Aluminum carbide (Al4C3) is generated from around ℃ to fill the voids in the refractory structure and improve the strength of the refractory. In addition, in Ag2O3-8iC-C refractories, by adding Mg-Al alloy and AQ, A! As the 2203 content increases, corrosion resistance also improves. However, as shown in the following formula, aluminum carbide has the property of reacting with moisture in the air at room temperature and becoming hydrated.

(2): Al1 C3+12H20→4Al(OH) 3 +3
CHA ↑In other words, aluminum carbide reacts with moisture to generate methane gas, resulting in aluminum hydroxide + A!
Produces Q (OH) 31. The volumetric expansion caused by the formation of aluminum hydroxide is so large that it leads to the collapse of the refractory. Therefore, it is dangerous to use carbon-containing refractories containing only AQ as lining refractories for ladles, pig iron mixers, etc., which may be cooled to room temperature during use. However, by using Si in combination, the above-mentioned hydration reaction of AQ is inhibited, and the stability of the refractory is ensured.

Another role of Si is the following formula (3) and (
As shown in 4), gaseous SiO is generated, moves within the refractory structure, reacts with the carbon component, and the generated fibrous SiC fills the voids and strengthens the refractory structure. At the same time, it also contributes to improving strength and reducing air permeability.

(3): S i +CO→S i O+C (4): S i O+2C-8t C+CO As mentioned above, silicon carbide is the least likely to be oxidized as an additive used in the present invention, so it is It exhibits antioxidant ability and works synergistically with other additives to provide oxidation resistance over a wide temperature range.

The antioxidant mechanism by silicon carbide is expressed by the following formula (5)% Formula (5): In other words, silicon carbide reacts with -carbon oxide to produce silicon oxide and carbon, and this silicon oxide alone or reacts with impurities in the refractory to form a glass phase to prevent oxidative loss of carbon components.

Based on the above research results, the present invention has been developed by using AQ, Mg-Al alloy and Si in a specific proportion in a carbon-containing refractory material consisting of a carbon material, silicon carbide and a non-carbon refractory material. We succeeded in obtaining a carbon-containing refractory that has excellent oxidation resistance over a wide temperature range, and also has excellent hot strength and corrosion resistance.

As the carbon material used in the present invention, natural graphite such as scaly graphite and globular graphite; artificial graphite such as electrode scrap, petroleum coke, and carbon black are used. Among these,
Graphite scales with low impurity content are more preferred. The blending ratio of carbon material in the carbon-containing refractory material is 3 to 50%
degree. If the amount of carbon material is less than 3%, the effects of suppressing wetting of slag and molten steel and improving slag resistance will not be sufficiently exhibited, while if it exceeds 50%, the strength of the refractory will deteriorate. There is a tendency for the density of the tissue to decrease and the density of the tissue to become insufficient. The particle size of the carbon material is about 3 mm or less, preferably about 1 mm or less.

As the silicon carbide used in the present invention, those commercially available as refractory materials, abrasive materials, etc. can be used as they are. The particle size is 125% from the viewpoint of reactivity and uniform dispersibility.
It is preferable to set it to below micrometer. Regarding the particle size, it is preferable that the grain size is 125 μm or less for the Mg-Al alloy, Aρ, and St, which will be described later, for the same reason. The blending ratio of silicon carbide in the carbon-containing refractory material is 0.5 to 15%
degree. If the amount of silicon carbide is less than 0.5%,
The effect of addition is not sufficiently exhibited, and on the other hand, if it exceeds 15%, oxidation resistance is sufficient, but wear due to melting increases and durability decreases.

The non-carbon-based refractory materials used in the present invention include oxide-based materials such as magnesia, spinel, alumina, silica, zircon, and zirconia; and non-oxide-based materials such as silicon nitride and boron nitride. Among these, those containing magnesia, spinel, alumina, etc. as main components are more preferable. The blending ratio of the non-carbon refractory material in the carbon-containing refractory material is the remaining amount after removing the carbon material and silicon carbide, that is, about 96.5 to 35%. The particle size of the non-carbon refractory material is about 5 mm or less.

In order to achieve the desired effect, the M g -A I2 alloy used as an additive component to the above carbon-containing refractory material contains about 30 to 70% of 12 and has an Afl/Mg
It is preferable that the weight ratio is about 0.5 to 1.5. Mg-
The amount of the Al alloy added is approximately 0.5 to 10 parts per 100 parts of the carbon-containing refractory material. If the amount of the Mg-AQ alloy added is less than 0.5 part, the effect of the addition will not be sufficiently exhibited. On the other hand, M g −A I2
If the amount of alloy added exceeds 10 parts, the engraving rate may increase and the spalling resistance may decrease. Although it is related to the amount, it may reduce corrosion resistance.

The amount of Aρ and SL added is 100% of the carbon-containing refractory material.
0.5 to 10%, respectively. The basis for the quantitative specification is the same as in the case of Mg-Al2 alloy.

Further, in order not to reduce the spalling resistance and corrosion resistance of the refractory, the total amount of the Mg-Al alloy, Al2 and SL shall not exceed 15 parts.

The carbon-containing refractory of the present invention contains a carbon-containing refractory material, silicon carbide, Mg-Aj2 alloy, Al2, and St in a predetermined ratio, and contains tar, pitch, and phenol.

By adding a known binder such as a resin or a furan resin, cross-wire and mold according to a conventional method, and drying at about 200°C, a product in the form of an unfired refractory is obtained.

In addition, the same formulation as above was prepared in a reducing atmosphere with a concentration of 900 to 1
When firing at about 500°C, a fired refractory is obtained.

Furthermore, when one or more of water, alcohol, ethylene glycol, anthracene oil, machine oil, etc. are added to the same formulation as above, it can also be used as a monolithic refractory such as pouring material, castable material, ramming material, etc. It is possible.

Effects of the Invention The carbon-containing refractory according to the present invention has excellent properties such as oxidation resistance, spalling resistance, hot strength, abrasion resistance, and corrosion resistance.

EXAMPLES Examples will be shown below to further clarify the features of the present invention.

Examples 1 to 5 and Comparative Examples 1 to 6 4 parts of resol type phenolic resin was added to the raw material mixtures shown in Table 2 (the proportions indicate parts), and after kneading, 100
Molded into a cap shape brick shape with a molding pressure of 0 kgf/c♂,
It was dried at 200°C for 12 hours.

The properties of the obtained unfired carbon-containing refractory are also shown in Table 2.

From the results shown in Table 2, the product of the present invention has the following characteristics compared to the comparative product:
It is clear that it is excellent in all of oxidative wear resistance, hot bending strength, and water compatibility.

Note 1) Mg/AΩ = 50150 (weight ratio) Note 2> A cylindrical test furnace lined with alumina bricks and having an internal volume of 340 φ x 400 mm was rotated at 24 rpm and heated with an oxygen-propane burner to 900°. The amount of weight loss is displayed when 8 to 10 specimens processed into 30 mm cubes are kept at C1 or 1200°C and tested for 30 minutes. ! Note 3) Three-point bending test method.
j Pack coke pleat around the specimen to prevent oxidation of the specimen, and after heating at 1400°C for 30ml, apply a load of 1 load and measure. The specimen shape is 25X25X
It is 1150mm.

Note 4) A specimen of 25 x 25 x 150 mm was treated in coke pleat at 1400°C for 2 hours, and then kept at room temperature (5 to 20°C) for one week.

No change was observed in the O specimen.

△ Fine cracks were observed.

× Cracks were observed in the specimen.

Comparative Experimental Example 1 The refractory of the present invention obtained in Example 3 and the refractory used in Comparative Example 2 were used to line the inner lining of a 250-ton pig iron mixed car.

When the lining of the pig iron mixer car was observed after 251 charges, it was found that in the parts where the refractory of the present invention was used, the moving surfaces were smooth and there was no damage to the joints, and the damage relationship was 0.30 mm/
It was a charge.

On the other hand, in the part where the comparative refractory was used, there were irregularities on the operating surface and damage to the joints was observed, and the damage rate reached as high as 0.41 mm/charge.

(that's all)

Claims (1)

[Claims] (1) Add 0.5 to 0.5 to 100 parts of a mixture of 3 to 50% carbon material, 0.5 to 15% silicon carbide, and 96.5 to 35% non-carbon refractory material to 100 parts of Al, Mg-Al alloy, and Si, respectively. A carbon-containing refractory compounded in a proportion of 10 parts and a total amount of 15 parts or less.