JP2003040684A - Castable refractory for molten iron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a castable refractory for molten iron improved in durability by improving molten iron resistance, and slag resistance. SOLUTION: The castable refractory for molten iron is obtained by electrically fusing mixture of alumina and silicon carbide, and moreover mixing electrically fused Al2 O3 -SiC as a refractory aggregate, the main chemical ingredient of which is 1-30 mass% SiC and the ballance Al2 O3 .

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an amorphous refractory material for hot metal which is excellent in corrosion resistance and oxidation resistance.

[0002]

2. Description of the Related Art Amorphous refractory for hot metal represented by, for example, a lining material for a blast furnace tappipe is conventionally made of alumina-silicon carbide, alumina-silicon carbide-carbon or alumina-spinel-silicon carbide. Irregular refractories have been proposed. For example, it is as described in Japanese Patent No. 2556416 and Japanese Patent Laid-Open No. 9-157043.

These amorphous refractory materials exhibit excellent durability by combining the effects of the hot metal resistance and volume stability of alumina and the slag resistance of silicon carbide.

[0004]

However, the amorphous refractory for hot metal is required to have further improved performance in order to further reduce the basic unit of refractory and improve the operating rate of the steelmaking equipment.

Conventional alumina-silicon carbide-carbon amorphous refractories have excellent hot metal resistance, but tend to have poor slag resistance. If the proportion of silicon carbide is increased, the slag resistance is improved, but the proportion of alumina is reduced accordingly, and the hot metal resistance is impaired.

On the other hand, the spinel-alumina-silicon carbide-carbon type amorphous refractory is superior in hot metal resistance to the above materials due to the blending of spinel. However, the spinel accounts for a small amount of silicon carbide, resulting in poor slag resistance. In addition, oxidation of silicon carbide (SiC + O ₂
→ SiO ₂ produced in the SiO ₂ + C) reacts with the spinel material, leading to deterioration of the refractory tissue strength by the formation of Al ₂ O ₃ -MgO-SiO ₂ system low Torubutsu eventually never even in solvent to molten iron of Not enough.

In order to solve the above problems, investigations have been made from the viewpoint of the material of the refractory aggregate used for it.
For example, in JP-A-10-245261 and JP-A-11-322451, a sintered Al ₂ O ₃ —SiC raw material obtained by adding a carbon raw material to an alumina-silica raw material and subjecting to heat treatment (firing) is disclosed. It has been proposed to use it as a refractory aggregate for irregularly shaped refractories.

In this sintered Al ₂ O ₃ -SiC raw material, the alumina component in the alumina-silica raw material is carbonized by the presence of the carbon raw material during the firing step in the production thereof to produce aluminum carbide. Aluminum carbide easily reacts with water. Since a large amount of construction water is added to the construction of the irregular refractory, the irregular refractory using this sintered Al ₂ O ₃ —SiC raw material is digested by the hydration reaction of the aluminum carbide during curing or drying. However, both the hot metal resistance and the slag resistance are insufficient due to the weakened structure strength.

Further, when the firing time is shortened in order to suppress the formation of the aluminum carbide, a considerable amount of unreacted SiO ₂ component remains, which also causes the deterioration of the hot metal resistance and the slag resistance. .

Sintered Al ₂ O ₃ -SiC raw material obtained by using alumina raw material instead of alumina-silica raw material and combining alumina raw material and silicon carbide raw material is inferior in compactness.
Therefore, it is necessary to add a sintering aid such as magnesia or silica, but the sintering aid causes a decrease in corrosion resistance.

Japanese Unexamined Patent Publication (Kokai) No. 62-212258 is not a refractory aggregate as an amorphous refractory, but it is an electrofused ZrO ₂ --Al ₂ O _3-
SiO ₂ -SiC raw material is shown. This electromelting raw material is effective for spalling resistance, which is a characteristic particularly required in the casting nozzle targeted by the invention of the same publication.

Further, this electromelting raw material contains 30 to 60% by mass of ZrO ₂ , so that Si based on zirconia mullite is formed.
It is an organization accompanied by C. However, zirconia
Mullite is easy to decompose into zirconia and mullite, and when used as an aggregate of an amorphous refractory for hot metal, it has poor corrosion resistance due to the decomposition of the zirconia-mullite.

Therefore, the present invention provides an amorphous refractory material for hot metal, which is excellent in both hot metal resistance and slag resistance, thereby improving the durability.

[0014]

The present invention is obtained by electromelting a mixture of an alumina raw material and a silicon carbide raw material, and
C: 1 to 30 wt%, a hot metal for monolithic refractories comprising blended as refractory aggregate the fused Al ₂ O ₃ -SiC raw material having a chemical composition of the balance Al ₂ O ₃ principal.

Since the Al ₂ O ₃ --SiC material used in the present invention is an electromelted product, it has a denser structure than the sintered product and, in addition, has both hot metal resistance and slag resistance. so,
The durability of the amorphous refractory for hot metal can be significantly improved.

[0016] In this Fused Al ₂ O ₃ -SiC raw material thereof Fused step, SiC component of silicon carbide raw material is decomposed into Si and C in the ultra-high temperature in the vicinity of the electrodes, C components and oxygen in the atmosphere It reacts quickly and becomes CO or CO ₂ and dissipates. On the other hand, the Si component is dispersed in the raw material. As a result, there is almost no formation of SiO ₂ found in the sintered product in the raw material composition.

In addition, the melt rapidly cools and solidifies in the portion other than the vicinity of the electrode, and the solidified phase blocks the atmosphere to prevent the oxidation of Si, and the raw material melted in this portion also contains SiO ₂ Almost no generation is seen.

The electro-fused Al ₂ O ₃ -SiC material used in the present invention contains both hot metal-resistant Al ₂ O ₃ and slag-resistant SiC components, and also produces SiO ₂ and decomposes zirconia mullite. Since there is no problem such as the above, it exhibits an excellent effect on the hot metal resistance and the slag resistance required for an indefinite refractory for hot metal.

This electrofused Al ₂ O ₃ --SiC raw material uses an alumina raw material and a silicon carbide raw material as starting materials in its production. Can contain specific amounts of Al and Si. For example, when the electrode voltage is increased, the oxidation operation starts and the amount of Al and Si produced decreases. Further, when the electrode voltage is lowered, the reduction operation is performed, and the production amounts of Al and Si increase. If the raw material feeding speed is further increased,
The amount of Al and Si produced increases.

When the electrofused Al ₂ O ₃ -SiC raw material contains Al and Si in a total amount of 0.05 to 5 mass%, the hot metal resistance and slag resistance of the amorphous refractory material are further improved.
This is because Al is Al ₂ O ₃ , Si at high temperature while using refractory.
Is changed to β-SiC, which acts as a densification of the refractory aggregate structure and acts as a bond to improve the hot strength.

Al and Si are metals, and in the free state, when they come into contact with construction water added in the construction of an irregular shaped refractory, H ₂ gas is generated and the refractory structure becomes porous. However, since Al and Si in the electrofused Al ₂ O ₃ —SiC raw material are confined in the raw material structure, they do not react with the working water that causes H ₂ gas generation.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Electrofused Al used in the present invention
_{The 2} O ₃ —SiC-based raw material is produced by using an alumina raw material and a silicon carbide raw material as a starting raw material, and producing a mixture thereof by an electrofusion method.

As the alumina raw material, synthetic or natural products such as sintered alumina, fused alumina, calcined alumina, bauxite, and shale shale are used. Impurities such as Fe ₂ O ₃ and SiO ₂ contained in the raw materials cause the melting point to be lowered, so that those with high purity of Al ₂ O ₃ are preferable. Among them, calcined alumina, which has high purity and is easily available as fine powder, is preferable.

As the silicon carbide raw material, for example, one having a SiC purity of 85 mass% or more is used. More preferably, the SiC purity is 90% by mass or more. If the purity is low, the C component contained as an impurity will generate CO gas due to the reaction with the atmosphere during the electrofusion, and the porosity of the electrofused Al ₂ O ₃ —SiC quality raw material will be high, and moreover, it is necessary for the slag resistance. The residual rate of SiC that becomes is also reduced.

The silicon carbide raw material is used as fine powder having a particle size of 0.3 mm or less, for example. Preferably 0.075 mm or less 3
The average particle size is 10 to 70 μm. If the particle size is too small, the oxidation of SiC will progress in the electrofusion process,
l ₂ O ₃ SiC amount of control -SiC matter in the raw material becomes difficult. When the particle size is large, the dispersion in the electrofused Al ₂ O ₃ —SiC raw material becomes poor, and the effect of the present invention is not sufficient particularly in the slag resistance.

The mixing ratio of the alumina raw material and the silicon carbide is, for example, 95: 5 to 50:50 in terms of mass ratio, and is arbitrarily determined within this range according to the purity of each raw material.

For the electric melting, a mixed powder of alumina raw material fine powder and silicon carbide fine powder is gradually charged into an arc electric melting furnace of a batch type or a tilting type while an arc current is flowing,
Dissolve well. After the melting, this is cooled to remove the incompletely melted portion at the outer edge portion, and then the particles are sized to a desired particle size in the crushing step.

In the chemical composition of the electrofused Al ₂ O ₃ -SiC raw material, if the proportion of SiC is less than 1% by mass, the slag resistance is poor, and if it exceeds 30% by mass, the proportion of Al ₂ O ₃ component becomes small. Poor hot metal resistance. More preferably 3 to 20% by mass
Is.

The proportion of the Al ₂ O ₃ component of the electrofused Al ₂ O ₃ -SiC raw material is the main component of the balance of the SiC proportion, for example 70
It is preferably from 99 to 99% by mass, more preferably from 80 to 97% by mass. If it is too small, the hot metal resistance will be poor, and if it is too large, the slag resistance will be insufficient.

The proportions of Al ₂ O ₃ and SiC can be adjusted by the mixing ratio of the alumina raw material and the silicon carbide raw material as the starting raw materials in the electrofusion step.

Electrofusion Al ₂ O ₃ --Si containing Al and Si
In the case of using a C material, if the total content of Al and Si is less than 0.05% by mass, the effect of improving the hot strength is poor. If it exceeds 5% by mass, Al is Al ₂ O ₃ and Si is β-S.
Probably because the stress at the time of change to iC causes strain in the material structure, no improvement in hot strength can be seen in this case either.

In the present invention, the amounts of Al and Si are defined by chemical analysis values, but these metal components also exist in the raw material in the state of alloy.

Electrofused Al₂O₃-SiC material is the above-mentioned component
Besides, unavoidable from alumina raw material and silicon carbide raw material
It may contain a specific ingredient. For example TiO₂, F
e₂O ₃, CaO, Na₂O₃, K₂O, MgO, ZrO₂etc
Is. From the viewpoint of corrosion resistance, these are 3% by mass or less in total.
Is preferred. More preferably, it is 1% by mass or less.

The proportion of the electrofused Al ₂ O ₃ -SiC raw material in the refractory aggregate is preferably 5 to 80% by mass. If it is less than 5% by mass, the effect of improving hot metal resistance and slag resistance is insufficient. If it exceeds 80% by mass, the proportion of the refractory ultrafine powder raw material for imparting fluidity during the construction of irregular refractory materials decreases, resulting in poor workability.

The refractory aggregates other than the electrofused Al ₂ O ₃ -SiC raw material are, for example, alumina, spinel, magnesia, silicon carbide, carbon and the like. Above all, it is preferable to use an alumina raw material and / or a spinel raw material, and silicon carbide and carbon as main materials.

Specific examples of the alumina raw material include electrofused alumina,
Examples include sintered alumina, bauxite, and shale.
Mullite, pyrophyllite, etc. can be used, but it is preferable to keep them in a small amount because of the low purity of Al ₂ O ₃ .

The spinel raw material is MgO.Al ₂ O ₃ type spinel and has the effect of hot metal resistance. Its chemical composition is
A common spinel having a MgO / Al ₂ O ₃ ratio close to the spinel theoretical composition value of about 28:72 is preferable, but the present invention is not limited to this.
May be, for example, 5 to 25% by mass of alumina rich spinel. It does not matter whether it is a sintered product or an electromelted product.

As a kind of spinel raw material, vanadium slag produced as a by-product in the process of producing an iron-vanadium alloy by the thermite method may be used. This vanadium slag usually contains 5 to 25 mass% of MgO.Al ₂ O ₃ based spinel.

The proportion of the alumina raw material and / or the spinel raw material in the refractory aggregate is preferably 90% by mass or less, more preferably 10 to 80% by mass.

The carbon raw material has the effect of slag resistance. Specific examples are clay graphite, scaly graphite, coke refined from artificial graphite and petroleum or coal, pitches, carbon black,
Such as anthracite. The addition amount thereof is preferably 0.5 to 5 mass% in terms of fixed carbon. If it is less than 0.5% by mass, the effect of slag resistance due to the difficulty of wetting with slag, which is a characteristic of carbon raw materials, cannot be exhibited. If it exceeds 5% by mass, the fluidity at the time of construction of an irregular shaped refractory decreases and the amount of construction water is increased, so the porosity of the construction body becomes high and the effect of slag resistance becomes insufficient.

Silicon carbide accounts for 5 to 7 in the ratio of the refractory aggregate.
0% by weight is preferred. If it is less than 5% by weight, the corrosion resistance tends to decrease, and if it exceeds 70% by weight, the spalling resistance is poor.

As the refractory aggregate, zircon, zirconia, chrome ore, volatile silica or the like may be combined. Among them, volatile silica, which is an ultrafine powder, is effective in imparting fluidity during the construction of irregular refractory materials.

In the amorphous refractory material of the present invention, the combination of the binder and the dispersant is the same as that of conventional materials. If necessary, an antioxidant, an explosion proof agent, a metal fiber, a thickener, a curing accelerator, a curing retarder, or coarse refractory particles may be used in combination.

The binder is alumina cement, magnesia cement, phosphate, silicate or the like. The addition ratio is preferably 1 to 15% by mass based on 100% by mass of the refractory aggregate. Further, a binder is not always necessary if a sufficient aggregation effect can be obtained by adding ultrafine powder such as volatile silica or calcined alumina or aluminum lactate.

The dispersant imparts fluidity during construction of the refractory. Specific examples are not limited at all, sodium tripolyphosphate, sodium hexametaphosphate, ultrapolyphosphate sodium, acidic sodium hexametaphosphate, sodium borate, sodium carbonate, inorganic salts such as polymetaphosphate, sodium citrate, tartaric acid. Examples thereof include soda, sodium polyacrylate, sodium sulfonate, polycarboxylic acid salts, β-naphthalene sulfonic acid salts, naphthalene sulfonic acid, and lignin sulfonic acid salts. About 0.01 to 1% by mass is added to 100% by mass of refractory aggregate.

The antioxidant is silicon, ferrosilicon, boron carbide (B ₄ C or the like), silicon nitride, boron nitride, magnesium boride, zirconium boride, calcium boride or the like. The addition amount is preferably 0.1 to 3% by mass based on 100% by mass of the refractory aggregate.

As the explosion-proof agent, organic fibers,
Organic foaming agents, basic aluminum lactate, metallic aluminum and the like. Specific examples of organic fibers include vinylon,
It is a polymer organic fiber such as PVA, rayon, polyester, nylon, polypropylene, or polyethylene, and its preferable addition amount is 0.0 with respect to 100% by mass of the refractory aggregate.
It is 5 to 2% by mass.

The thickener is clay, bentonite, CMC or the like, and the preferable addition amount is 2% with respect to 100% by mass of the refractory aggregate.
It is not more than mass%.

The refractory coarse particles have a role of preventing the development of cracks generated in the refractory structure. The particle size of the refractory aggregate is, for example, 5 to 8 mm at maximum, but the coarse refractory particles have a larger particle size than this refractory aggregate. The size of the particles protrudes in the refractory structure and is clearly distinguished from the refractory aggregate.

The particle size of the coarse refractory particles is in proportion to the particle size of the refractory aggregate, but is preferably 10 to 50 mm. As a specific material, an alumina raw material, a spinel raw material, a silicon carbide raw material, or a refractory waste material containing these as main materials can be used. The proportion is preferably 30% by mass or less with respect to 100% by mass of the refractory aggregate.

The amorphous refractory material of the present invention can be used not only for new construction but also for repair. The construction method is pouring or spraying, which is not particularly different from the conventional method. For example, in pouring construction, apply construction water outside and
About 0% by mass is added, mixed, and poured into using a formwork. At the time of construction, it is vibrated by a vibrator to improve the filling property. After construction, cure and dry.

[0052]

EXAMPLES Table 1 shows the fused or sintered Al ₂ used in each example.
O ₃ -SiC material and electrofused ZrO ₂ -Al ₂ O ₃ -Si
O is a ₂ -SiC raw material.

[0053]

[Table 1] The electromelted product was manufactured by melting the starting materials shown in Table 1 in a batch-type arc electric furnace. Sintered products were produced by mixing the starting materials shown in Table 1, compression molding, and firing at 1450 ° C.

In the present invention, electrofused Al₂O₃-SiC material
The particle size of the material can be used regardless of whether it is coarse, medium or fine.
Used here as coarse and medium particles, unified to 8 to 0.1 mm
did. Also, according to this, sintered Al₂O₃-SiC quality
Raw material, electrofused ZrO₂-Al₂O ₃-SiO_Two-SiC material
The material was also used as 8 to 0.1 mm.

Table 2 shows the composition of the irregular refractory material of each example,
The test results when used as a casting material are shown. The test method is as follows.

[0056]

[Table 2] For measurement of hot metal resistance, slag resistance and hot strength, test pieces obtained by kneading the compounding composition of each example, curing, and drying at 110 ° C. for 24 hours were used.

Hot metal resistance: A test piece was set in a high frequency test furnace, and an erosion test was carried out at 1550 ° C for 10 hours using an erosion agent having a weight ratio of pig iron and blast furnace slag of 40: 1. Since the hot metal wear action in an actual machine progresses at the slag / hot metal interface, slag and pig iron were used as erosion agents assuming this. The erosion size of Comparative Example 1 was shown as 100 and an index. The smaller the index, the smaller the melt loss size and the better the hot metal resistance.

Slag resistance: A horizontal rotary test furnace was used. Blast furnace slag was used as an erosion agent and tested at 1550 ° C for 10 hours. The value is shown as an index when the erosion size of Comparative Example 1 is 100. The smaller the index, the better the corrosion resistance.

Hot strength: Bending strength was measured during hot holding at 1450 ° C. for 1 hour in a nitrogen atmosphere. 40 mm x
A 40 mm × 160 mm test piece was subjected to a three-point bending method with a span of 100 mm.

Actual machine test: A part of each example was cast as a lining of a blast furnace tappipe and used. After passing through 35,000 t, the melting rate (mm / 1,000 t) was determined.

As shown by the test results, the examples of the present invention exhibit excellent effects on both melt damage resistance and slag resistance. In addition, Examples 3 to 3 using the fused Al ₂ O ₃ —SiC raw material containing Al and Si within the range specified in the present invention
In No. 10, the hot strength is further excellent, and the hot metal resistance and slag resistance are further improved.

Comparative Examples 1 and 2 are electrofused Al ₂ O ₃ —SiC.
It is a conventional general amorphous refractory for hot metal that does not use high quality raw material, and is inferior in hot metal resistance and slag resistance. Example 3 is a case where an electrofused Al ₂ O ₃ —SiC material having a composition outside the scope of the present invention is used, and since the porosity is large, the hot metal resistance and slag resistance are poor. Sintered Al ₂ O ₃ -SiC raw material or fused _{ZrO 2 -Al 2 O 3 -SiO 2} -Si
Comparative Examples 4 and 5 using the C-type raw material are inferior in hot metal resistance, slag resistance and hot strength.

Further, in Examples 1, 2, 5, 6, 7, 9 and Comparative Example 1, actual machine tests were conducted. From the results, the remarkable effect of the present invention can be confirmed.

The above-described actual machine test is an example of use as a blast furnace gutter material, but the present invention is not limited to this. -It can be used as an amorphous refractory for molten iron.

[0065]

The amorphous refractory material for hot metal according to the present invention is excellent in both hot metal resistance and slag resistance as compared with the conventional materials, as shown by the results of the above examples.

For example, conventionally, in the lining of a blast furnace tap gutter, a zone lining is used to vertically separate a hot metal material having excellent hot metal resistance and a slag material having excellent slag resistance. . Since the amorphous refractory material of the present invention is excellent in both hot metal resistance and slag resistance, this zone lining is not necessarily required, and it is possible to perform integral construction, and it is also effective for labor saving of the gutter lining construction.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoshinori Saikai             1-3-1 Niihama, Arai-cho, Takasago, Hyogo Prefecture             Kurosaki Harima Co., Ltd.             Shape factory (72) Inventor Hiroyoshi Tomino             Kitakyushu City Hachiman Nishi Ward Higashihama 1-1 1-1 Kurosaki Ban             Second Manufacturing Division, Ma Co., Ltd. Yawata Irregular Factory             Within F term (reference) 4G033 AA02 AA07 AA09 AA14 AA17                       AB02 AB10

Claims (4)

[Claims] 1. Obtained by electrofusing a mixture of an alumina raw material and a silicon carbide raw material, and SiC: 1 to 30 mass%, the balance A
An amorphous refractory for hot metal, which is prepared by blending, as a refractory aggregate, a fused Al ₂ O ₃ —SiC raw material having a chemical composition mainly composed of l ₂ O ₃ . 2. Obtained by electromelting a mixture of an alumina raw material and a silicon carbide raw material, and SiC: 1 to 30% by mass, Al and Si in a total amount of 0.05 to 5% by mass, and balance Al ₂ O ₃ An amorphous refractory for hot metal, which is obtained by blending a fused Al ₂ O ₃ —SiC raw material having the chemical composition of 1. as a refractory aggregate. _3. Electrofused Al ₂ O ₃ —SiC in refractory aggregate
The amorphous refractory material for hot metal according to claim 1 or 2, wherein the proportion of the quality raw material is 5 to 80% by mass. 4. The refractory aggregate other than the electro-fused Al ₂ O ₃ —SiC raw material is an alumina raw material and / or MgO—Al ₂ O ₃
4. The amorphous refractory for hot metal according to claim 1, 2 or 3, which comprises a spinel raw material, a silicon carbide raw material and a carbon raw material as main materials.