JPH10279367A - Graphite-containing monolithic refractory material for blast furnace main trough metal line - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refractory material which is capable of exhibiting a sufficient lifetime in a section where the velocity of flow of molten iron is high by forming the monolithic refractory material which contains graphite and silicon at a specific weight % ratio and exhibits the characteristic of a specific value or above in hot three point bending strength at a specific temp. SOLUTION: This monolithic refractory material contains 3 to 20 wt.%. graphite, 0.8 to 6.0 wt.%. silicon powder of <=80 μm in grain size and 80 to 95 wt.% aggregate, such as Al2 O3 , ZrO2 , MgO, SiO2 , spinel and SiC, adjusted dividedly to coarse grains, middle grains and fine grains and exhibits the strength of >=10 kg/cm2 in the hot three point bending strength at 1,500 deg.C. Further, assistants including a hardener, such as silica sol, an antioxidant, such as B4 C, a dispersant, such as sodium tripolyphosphate, and a curing retarder, such as oxalic acid, are added at need to this material. The silicon powder reacts with the graphite to be combined and added in a high-temp. atmosphere to crystallize three-dimensional network reactive SiC in the matrix. The network of this SiC coats the aggregate particles and graphite particles, thereby developing high bonding strength.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amorphous refractory for use in a metal line of a main gutter of a blast furnace, which is a graphite-containing refractory having excellent corrosion resistance, particularly in a region near the surface of the gutter material where the flow velocity of hot metal is large. It relates to fixed refractory materials.

[0002]

2. Description of the Related Art In recent years, in a blast furnace, from the viewpoint of reducing the cost of producing pig iron, it has been aimed to reduce the basic unit of refractory materials by tapping for a long time. In particular, there is a strong demand for an improvement in a gutter material forming a gutter for transferring hot metal from a blast furnace to a transport vessel. Above all, in the main gutter (tapping gutter) for flowing hot metal and molten slag at the same time, corrosion resistance to both slag and metal must be taken into consideration, and it is the material that requires the most improvement.

As such a refractory for a main gutter, a high SiC refractory has conventionally been used near the slag-air interface (slag line), while Al ₂ O ₃ − has been used near the slag-metal interface (metal line). SiC refractory, Al ₂ O ₃ -spinel-
SiC refractories are used. In addition, as a material simply developed for the purpose of improving corrosion resistance, there is an amorphous refractory containing graphite as disclosed in JP-A-8-183666 and JP-A-8-183667.

[0004] These graphite-containing amorphous refractories disperse graphite having poor wettability with slag and metal in the refractory, so that the eluting components in the refractory are brought into contact with hot metal and slag in the above-mentioned portions. It is devised so as to reduce the chance of doing.

[0005]

Generally, local wear is observed in the main gutter of the blast furnace. In other words, at the interface such as the slag line and the metal line described above, Marangoni convection occurs in the slag. Is observed. Further, when the main gutter is viewed in the flow direction of the molten iron and slag, the vicinity of the tap hole where the slag discharged from the blast furnace flows into the inside of the main gutter becomes a maximum part of the wear. It is considered that this is because the hot metal and slag rapidly flow into the outlet for dropping the molten metal, which further promotes the Marangoni convection, and at the same time, increases the mechanical wear caused by the flow velocity of the hot metal, which is maximized.

[0006] In this respect, in the above graphite-containing amorphous refractories,
By utilizing the poor wettability between graphite and hot metal or slag, elution of refractory components is prevented, and the durability of the gutter material is improved. However, graphite-containing refractories have low mechanical strength, and thus cannot always be said to have sufficient durability in a portion where the molten metal velocity is high, such as a tapping hole. This is because graphite has no self-sintering property, and the presence of graphite itself inhibits sintering of other oxide components, so that the strength of the entire refractory decreases. In order to prevent this, it is usual to increase the self-sintering property by adding an oxide-based sintering aid utilizing general glass formation or adding an ultrafine powder oxide.

[0007] However, the glass bond can exhibit room temperature strength, but does not exhibit the strength in a high temperature region where a blast furnace main gutter is used. Will be lower. Therefore, an object of the present invention is to provide not only a room temperature strength but also a high temperature strength (hot strength at a temperature of about 1500 ° C., which is a use temperature condition in a blast furnace main gutter), and to sufficiently withstand hot metal flow rates. It is an object of the present invention to provide an amorphous refractory material for a blast furnace main gutter metal line that can exhibit heat resistance.

[0008]

Means for Solving the Problems The present inventors have developed a refractory material composition capable of expressing the hot strength of the refractory in the above-mentioned blast furnace main gutter operating temperature range, and a matrix structure of the refractory after firing. In the study, it was found that it is effective to improve the hot strength by forming needle-like β-SiC network to strengthen the refractory matrix. In order to sufficiently exhibit the properties of SiC, which has excellent hot strength, by adding Si to the amorphous refractory material (raw material) with an extremely fine particle size, a uniform and fine particle is formed in the refractory matrix. Reaction β-
It was also found that it was effective to form a SiC network. Furthermore, it was found that it is also effective to adjust the addition ratio of Si so that the corrosion resistance does not decrease due to SiO ₂ formed on the Si surface. The present invention has been developed based on such knowledge.

That is, the present invention relates to an amorphous refractory containing 3 to 20% by weight of graphite and 0.8 to 6.0% by weight of silicon, and having a hot three-point bending strength at 1500 ° C. of 10 kg. An object of the present invention is to provide a graphite-containing amorphous refractory material for a blast furnace main gutter metal line, which exhibits a characteristic of not less than / cm ² . In the present invention, the silicon is preferably a fine powder having a particle size of 80 μm or less. In the present invention, it is desirable that three-dimensional network-like reactive SiC be crystallized in the refractory matrix in the gutter material use temperature range. Also,
In the present invention, needle-like B-SiC
It is desirable to include

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the amorphous refractory material according to the present invention, various graphites are blended together with aggregates described later. The compounding amount of this graphite is irregular refractory material (aggregate: 80 ~
97 wt%) in the range of 3 to 20 wt%. The reason is that if the blending amount of the graphite is less than 3 wt%, the inherent effects of the graphite such as high thermal conductivity and slag resistance cannot be sufficiently obtained, while the blending amount of the graphite is 20 wt%
If the ratio exceeds 1, the oxidation resistance becomes a problem, and the fluidity is reduced, so that a dense molded refractory construction cannot be obtained. The preferred range of the graphite content is 5 to 15 wt%.
It is.

However, graphite-containing amorphous refractories generally have not so high mechanical strength in the operating temperature range of the gutter (high temperature range in contact with hot metal and slag). This is because graphite itself does not have sintering properties and the presence of graphite hinders the formation of ceramic bonds generated by sintering of fine powder materials. For this reason, simply adding graphite will
Sufficient strength to cover from room temperature to high temperature is not exhibited. Further, graphite has a disadvantage that it is easily oxidized in a high-temperature atmosphere.

In order to overcome these weaknesses of graphite, the present invention includes a predetermined amount of fine silicon. The reason for containing silicon is that the graphite-containing amorphous refractory material according to the present invention reacts with the graphite powder to be added compositely at the gutter material operating temperature to crystallize a three-dimensional network-like reaction SiC in the matrix, The SiC network will cover and connect the aggregate particles, fines, and graphite particles. That is, in the present invention, silicon is used to form a reaction β-SiC network in the matrix.

In a high-temperature atmosphere where graphite and Si coexist, Si +
C = SiC or Si + CO = SiC + 1/2 O ₂ reaction α
Crystallize β-SiC via -SiC. In particular, when Si having a fine particle size is used, the generated β-SiC is also in a form in which fine needles are entangled with each other, and a strong bonding force is developed. However, if the crystallized SiC becomes excessive, it becomes easy to dissolve in hot metal, and the oxide layer of SiOC on the surface of SiC
_The formation of ₂ causes a decrease in corrosion resistance with an increase in the amount of SiO ₂ .

In the present invention, the reason why the amount of silicon to be contained in the graphite-containing amorphous refractory material is limited to 0.8 to 6.0 wt% is that when the added amount of silicon is less than 0.8 wt%, the hot strength is insufficient. On the other hand, if the addition amount exceeds 6.0% by weight, the hot strength increases, but on the contrary, the corrosion resistance decreases.

In the present invention, the silicon (Si) preferably has a particle size of 80 μm or less. This is because, when using what size exceeds 80 [mu] m, in order to achieve the hot strength needed requires the addition of more than 7 wt%, suitability area for overlapping the corrosion resistance decrease area by SiO ₂ produced is very The reason for this is that the width is narrow, and it is not preferable in consideration of variations. In addition, the particle size adjustment of Si is common pulverization,
You can do it by classification. In addition, this Si is one of the amorphous refractory materials that handle water, and it is not particularly necessary to worry about reaction with water, and it is necessary to consider surface treatment for water resistance and additives for preventing hydration. There is no advantage.

The irregular refractory material according to the present invention is required to exhibit properties of a hot three-point bending strength at 1500 ° C. of 10 kg / cm ² or more. Normally, the temperature of hot metal and slag from tapping from a blast furnace is around 1500 ° C. Therefore, the characteristic that the amorphous refractory for a blast furnace main gutter targeted in the present invention should have is the hot strength at 1500 ° C. It is. In this regard, according to the study of the inventors, as is apparent from the examples described below,
Under the conditions used that the rate of tapping stream is large, the hot bending strength 10 kg / cm of less than ² at 1500 ° C., no effect in suppressing mechanical wear is large refractory erosion, which 10 kg / cm It was found that the effect of suppressing erosion was effective only when the ratio was ² or more.

The irregular refractory material according to the present invention comprises:
In addition to the above-mentioned graphite, metallic Si, etc., as a matter of course, as an aggregate constituting the skeleton component of the amorphous refractory, basic,
It is desirable to use one or more selected from neutral and acidic ones. For example, magnesia, spinel,
It contains about 80 to 95% by weight of alumina, zirconia, zircon, silica, silica, silica, silicon carbide, chamotte, and the like. The particle size of these aggregates is preferably adjusted separately for coarse particles, medium particles, fine particles, and fine particles so as to obtain a densely packed structure.

Further, in the amorphous refractory material according to the present invention, auxiliary agents to be selectively used as necessary, for example, as a curing agent (binder), alumina cement and silica sol generally used for refractories are used. Alternatively, use alumina sol, etc., use B ₄ C, SiC, Si, Al as an antioxidant, and use sodium tripolyphosphate, sodium hexametaphosphate, sodium ultrapolyphosphate, sodium acid hexametaphosphate, sodium borate as a dispersant. , Using one or more of inorganic salts such as sodium carbonate, sodium citrate, tartrate, sodium polyacrylate, sodium sulfonate and sodium naphthalene sulfonate, and curing As the retarder, it is preferable to use oxalic acid, citric acid, gluconic acid, boric acid and the like.

The irregular refractory material according to the present invention comprises:
Various fibers, fine metal powders and the like may be further added in addition to the above-mentioned blends as long as the effects of the present invention are not impaired.

[0020]

【Example】

Example 1 This example is used as an amorphous refractory material of the present invention and comparative examples, as an amorphous refractory of a blast furnace main gutter metal line.
Contains Al ₂ O ₃ , SiC and graphite as the main components and in the fine powder part
An irregular refractory based on a refractory raw material comprising Al ₂ O ₃ and graphite, with the remainder being cement, a setting retarder, a dispersant, and an antioxidant, was used. In addition, graphite has an average particle size of 20μ.
m artificial graphite, and the proportion of Al ₂ O ₃ is 72
wt%, SiC was 12 wt%, and graphite was 10 wt%. And, the above-mentioned irregular shaped refractory material contains Si at 200 μm, 100 μm, 80 μm,
0.1 to 10% by weight was added as an external number in each particle size of μm and 30 μm. This Si becomes almost 100% β-SiC. Kneading these irregular refractory materials in actual gutters, that is, for the main gutter metal line of the blast furnace, with a water mixture of 5.5 wt% of the refractory, was performed at the position near the hot metal outlet where the largest amount of wear occurred. A comparative evaluation was made based on the speed (iron throughput / tapped volume). The operating conditions used were a tapping temperature of 1502 to 1514 ° C and a slag ratio of 33.8 to 36.1%. As is clear from the results shown in FIGS. 1 and 2, the hot strength at 1500 ° C. must be 10 kg / cm ² or more.
It has been confirmed that the particle size of Si is preferably 80 μm or less, and the added amount is preferably 0.8 to 6.0 wt%.

Example 2 The gutter used in this example was Al ₂ O ₃ : 72 wt%, SiC: 12
wt%, the balance is refractory raw material consisting of cement, setting retarder, dispersant, antioxidant, average particle size with the balance being constant
It is an amorphous refractory material in which graphite of 20 μm is changed in the range of 0 to 30% by weight. In addition, this irregular refractory has a particle size of 30 μm.
A material in which 3% by weight of Si was added to generate a reaction β-SiC of 4% by weight or more was used. Operating conditions are the same as in the first embodiment. As is clear from FIG. 3 showing the results, it was confirmed that the graphite content was preferably 3 to 20% by weight.

[0022]

As described above, according to the amorphous refractory material of the present invention, in the region where the hot metal flow rate is low, the corrosion resistance is not impaired as in the case of the conventional graphite-containing amorphous refractory, and the mechanical strength in the area where the hot metal flow rate is high is not affected. Corrosion resistance can be significantly improved, and the gutter life in an actual gutter can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the amount of Si added and the hot strength when the average particle size of Si is changed.

FIG. 2 is a graph showing the relationship between the Si addition amount and the wear rate when the average particle size of Si is changed.

FIG. 3 is a graph showing the relationship between the graphite content and the wear rate in Example 2.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Masato Kumagai 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Inside the Technical Research Institute of Kawasaki Steel (72) Inventor Masato Takagi 1-1-1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki Inside the Technical Research Institute of Iron and Steel Corporation (72) Takashi Haraoka 1st Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Inside the Technical Research Center of Kawasaki Steel Corporation (72) Inventor Shinzo Kosaka 1576 Higashi-oki Address 2 Kawasaki Furnace Materials Co., Ltd.

Claims (4)

[Claims] (1) 3 to 20% by weight of graphite and 0.8 to 6.0% of silicon.
An amorphous refractory material containing less than 15 wt%
A graphite-containing amorphous refractory material for a blast furnace main gutter metal line, which has a characteristic of a hot three-point bending strength at 00 ° C. of 10 kg / cm ² or more. 2. The amorphous refractory material according to claim 1, wherein the silicon is a fine powder having a particle size of 80 μm or less. 3. The irregular-shaped refractory material according to claim 1, wherein a three-dimensional network-like reactive SiC is crystallized in the refractory matrix in a gutter material use temperature range. 4. The amorphous refractory material according to claim 3, wherein the matrix contains acicular β-SiC.