JP2000178074A - Castable refractory for blast furnace tapping spout - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refractory which is suitable for a lining of a blast furnace and excellent in service life by containing respectively specified quantities of carbon, MgO.Al2O3 calcined spinel super-fine powder, silicon carbide and alumina. SOLUTION: A refractory contains, by weight, 1-20% carbon, 1-20% MgO.Al2 O3 calcined spinel super-fine powder, 0-20% silicon carbide, and 20-95% alumina. Alternatively, the refractory contains 1-20% carbon, 1-70% MgO.Al2O3 spinel, 0-20% silicon carbide, 20-95% alumina, and the MgO.Al2O3 calcined spinel super-fine powder occupies 1-20% of MgO.Al2O3 spinel with reference to 100% refractory aggregate. The MgO.Al2O3 calcined spinel super-fine powder is preferably <=5 μm in average grain size. The super-fine powder is preferably <=1600 deg.C in burning temperature, and the component ratio of MgO to Al2O3 in the chemical composition is preferably 10-35% MgO, and the balance mainly Al2O3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a castable refractory used as a lining of a blast furnace gutter.

[0002]

2. Description of the Related Art A blast furnace gutter has a role as a passage for hot metal discharged from a blast furnace to reach a ladle, a mixed iron wheel and the like. The lining is
In recent years, castable refractories have been used from the viewpoint of workability. The material is alumina-silicon carbide-carbon (Japanese
3-164479), alumina-spinel-silicon carbide-carbonaceous (JP-A-5-339065) and the like are the mainstream.

[0003]

However, conventional castable refractories for gutters have never had a sufficient service life due to the severer blast furnace operation in recent years, and the efficiency of tapping work has been improved. From the viewpoint of reducing the basic unit of refractory, etc., there is a strong demand for a material having a longer life.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a castable refractory for a blast furnace gutter which meets the above-mentioned demand. The feature is that the refractory aggregate composition is
Carbon _{1~20wt%, MgO · Al 2 O} 3 based calcined spinel micronized 1 to 20 wt%, silicon carbide 0 to 20 wt% and alumina
It is a castable refractory for blast furnace gutters containing 20-95 wt%. The composition of the refractory aggregate is 1-20% by weight of carbon, MgO
· _Al 2 _{O 3} spinel 1~70wt%, silicon carbide 0~20w
t%, 20-95 wt% alumina, and refractory aggregate 100
wt%, 1-20 wt% of the spinel
% Is a castable refractory for blast furnace gutters in which MgO.Al ₂ O ₃ based calcined spinel is ultrafine powder.

[0005] In the blast furnace gutter, slag flows along with hot metal. Since silicon carbide is excellent in slag erosion resistance in conventional materials, it is indispensable to use silicon carbide in at least the material of the slag line portion of the gutter lining. However, in the case of the lining of the metal line portion located below the slag line portion, when silicon carbide is used, silicon carbide is decomposed at a high temperature during use, and the Si component is dissolved in the hot metal, which causes a reduction in corrosion resistance. .

The interface between the metal line portion and the slag line portion moves up and down with a certain width depending on the state of hot metal passing. Silicon carbide is inherently undesirable in the lining of the metal line portion, but the metal line portion is also subject to slag wear near the interface with the slag line portion,
In conventional materials, silicon carbide is also used for the metal line portion for the purpose of imparting slag resistance.

FIG. 1 is a cross section perpendicular to the length direction of the blast furnace gutter, and schematically shows the state of wear of the lining. In the figure, (1) is slag and (2) hot metal. The lining corresponds to this, (3) is the slag line, and (4) is the metal line (4). In addition, a permanent brick (6) is usually interposed between the steel skin (5) and the lining.
Dotted line A is the lining inner surface position before wear.

[0008] The castable refractory for gutters of the present invention exhibits excellent slag resistance even when silicon carbide is not used or reduced by using an appropriate amount of ultra-fine calcined spinel powder. As a result, especially in the lining of the metal line portion, the service life thereof is significantly improved.

The blast furnace slag is a CaO.SiO ₂ slag. The calcined spinel ultrafine powder reacts with the slag component to increase the melting point of the slag, thereby increasing the viscosity of the slag. Then, the slag having increased viscosity becomes difficult to penetrate into the refractory structure, which is considered to improve the slag resistance.

However, on the other hand, the slag resistance of the calcined spinel ultrafine powder is reduced in the presence of silicon carbide. This is because the MgO component in the spinel component promotes the oxidation of silicon carbide, and the Si
This is considered to be because O ₂ reacts with the refractory aggregate constituting the material and generates a SiO ₂ -based low melt which causes a reduction in corrosion resistance. Therefore, in the present invention, the use of silicon carbide is not preferred, and even if it is used, the proportion of silicon carbide in the refractory aggregate is high.
It is necessary to keep it at 20 wt% or less. More preferably, it is at most 10 wt%.

The slag resistance effect of the present invention described above cannot be obtained with ordinary sintered spinel. It is first exhibited by using ultra-fine calcined spinel powder. This is presumably because the calcined spinel ultrafine powder was fired in a relatively low temperature range and had a high specific surface area, and thus had high reactivity with slag.

Sintered spinel, which is generally used as a refractory raw material, is fired at a high temperature of 1700 ° C. or more, like other basic refractory raw materials or neutral refractory raw materials, in order to obtain high corrosion resistance, high fire resistance, and the like. Reactivity with slag is lower than that of calcined spinel ultrafine powder.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS MgO.Al ₂ used in the present invention
The method for producing the O ₃ -based calcined spinel ultrafine powder is not particularly limited. For example, an alumina source such as calcined alumina or aluminum hydroxide and a magnesia source such as lightly-baked magnesia or magnesium hydroxide are mixed at an arbitrary ratio, fired in a low temperature range, and then finely pulverized. The firing temperature is preferably 1600 ° C. or lower. If the temperature exceeds 1600 ° C., the activity decreases, and the effect of increasing the melting point by reacting with blast furnace slag is poor. The lower limit of the firing temperature is
1100 ° C. is preferable in order to cause spinel bonding by the mutual reaction between alumina and magnesia. The most preferred firing temperature is 1100-1500C.

In the chemical composition of the ultra-fine calcined spinel powder,
MgO component and Al₂O₃Ingredient ratio is the theoretical value of spinel
Not limited to MgO, for example, MgO: 10 to 35 wt%, the balance being
Al ₂O₃The main one can be used. Too much MgO
And there is a problem of hydration of MgO at the time of construction, which is not preferable.

The average particle size of the calcined spinel ultrafine powder is preferably 5 μm or less. If the average particle size exceeds 5 μm, the reactivity with slag is poor, and the effect of improving slag resistance in the present invention is insufficient. Further preferred average particle size is 0.2 to 3μ
m. Although the effect of the present invention can be obtained even if the average particle size is 0.2 μm or less, it is not preferable in terms of productivity due to the labor required for pulverization. The average particle size can be specified by, for example, a laser type particle size distribution analyzer.

When the proportion of the calcined spinel ultrafine powder in the refractory aggregate is less than 1 wt%, the effect of the slag resistance is inferior, and 20 w
If the content exceeds t%, the refractory structure causes a decrease in spalling resistance due to oversintering.

As the spinel, a normal sintered spinel, an electrofused spinel, or the like can be used in combination with the above-mentioned calcined spinel ultrafine powder. However, in this case, the ratio of the entire spinel including the ultrafine powder is set to 1 to 70 wt%. If it exceeds 70% by weight, spalling resistance is undesirably reduced.

Even when ordinary sintered spinel, electrofused spinel and the like are used in combination as described above, the ratio of the calcined spinel ultrafine powder is required to obtain the effect of the present invention.
It is necessary that the content be 1 to 20% by weight based on the entire refractory aggregate.

Carbon has an effect of imparting spalling resistance. It also has the effect of preventing slag penetration and hot metal penetration. Specific materials include pitch, carbon black, artificial graphite, phosphorous graphite, earthy graphite, coke, and the like. If the proportion in the refractory aggregate is less than 1 wt%, the effect of carbon cannot be obtained, and if it exceeds 20 wt%, the corrosion resistance is reduced due to oxidation.

Silicon carbide has a slag permeation resistance effect.
However, in the present invention, since the calcined spinel ultrafine powder has its role, it is not always necessary to use this silicon carbide. Also, when silicon carbide is used together with ultra-fine calcined spinel powder, silicon carbide is easily oxidized, and
Since O ₂ lowers the corrosion resistance of the material, the ratio is set to 15 wt% or less even when used. More preferably,
10 wt% or less. In addition, among silicon carbides, those having a small particle diameter have high reactivity, and therefore, it is necessary to particularly reduce them.

Alumina occupying the balance has effects such as volume stability and corrosion resistance. Specific examples include sintered alumina, fused alumina, shale, bauxite, and the like. Among them, synthetic products such as sintered alumina and electrofused alumina having stable quality are preferable. Further, calcined alumina may be used for the fine powder portion.

When the proportion of alumina in the refractory aggregate is in proportion to the proportion of other refractory aggregates, if the proportion is less than 20 wt%, the volume stability is poor, and cracks and peeling are likely to occur. 95w
If it exceeds t%, the corrosion resistance is poor. As long as the refractory aggregate does not impair the effects of the present invention, magnesia, magnesia-calcia, zircon, zirconia, chromium ore, silicon nitride,
A small amount of silica, silica flour, silica-alumina, mullite, chromium oxide or the like may be used in combination.

[0023] The composition other than the refractory aggregate includes a binder,
Dispersants, drying accelerators, metal fibers, antioxidants, thickeners, refractory coarse particles and the like. The binder is alumina cement, magnesia cement, or the like, and the addition ratio thereof is preferably 1 to 15% by weight based on 100% by weight of the refractory aggregate.

The dispersant imparts fluidity during construction of the refractory. Specific examples include sodium tripolyphosphate, sodium hexametaphosphate, sodium ultrapolyphosphate, sodium acid hexametaphosphate, sodium borate, sodium carbonate, inorganic salts such as polymetaphosphate, sodium citrate, sodium tartrate, sodium polyacrylate, Sodium sulfonate, polycarboxylate, β-naphthalene sulfonate, naphthalenesulfonic acid and the like. About 0.01 to 1 wt% of the outer shell is added to 100 wt% of the refractory aggregate.

As the drying accelerator, organic fibers,
Foaming agents, basic aluminum lactate, metallic aluminum and the like. Specific examples of the organic fibers are polymer organic fibers such as vinylon (including polyvinyl alcohol), rayon, polyester, nylon, polypropylene, and polyethylene. Antioxidants include metal powders such as silicon and magnesium, borides, glass powders, and the like. The thickener is clay, bentonite, CMC or the like.

The refractory coarse particles have a role of preventing the growth of cracks generated in the refractory structure. The particle size of the refractory aggregate is 5 to 8 mm at maximum, and is adjusted to coarse, medium, and fine particles within the range of the particle size or less so as to obtain a tightly packed refractory structure. The refractory coarse particles have a larger particle size than this refractory aggregate, and in the size of the particle size, protrude in the refractory structure and are clearly distinguished from the refractory aggregate.

The particle size of the refractory coarse particles has a balance with the particle size of the refractory aggregate, but is preferably 10 to 50 mm. As the material, alumina, spinel, silicon carbide, or refractory waste material containing these as main materials can be used. The ratio is 40 wt% or less, preferably 10 to 30 wt%.

In the construction of the castable refractory for gutters of the present invention, as in the case of the conventional material, the construction water is externally added, and about 4 to 8 wt% is added and mixed, and poured between the gutter outer shell and the core. At the time of construction, it is preferable to vibrate with a vibrator in order to enhance the filling property. Since the material of the present invention is particularly preferable as the material of the metal line portion among the linings of the gutters, it is used only for the lining of the metal line portion, and the slag line portion may be made of another material. In addition, it can be used for both new lining of gutters and rehabilitation after gutter use.

[0029]

EXAMPLES Table 1 shows the chemical components of the refractory aggregate used in Examples of the present invention and Comparative Examples. The average particle size of the ultrafine powder and the firing temperature of the spinel are also shown.
Tables 2 and 3 show the composition and test results of the inventive examples and comparative examples. The test method is as follows.

Corrosion resistance: 5 to 6% by weight of construction water was added to each composition shown in Tables 2 and 3, and after kneading, the mixture was poured into a vibrating mold and molded. Next, curing and drying were performed to obtain a test sample. Each sample is lined in a high-frequency furnace,
Pig iron: blast furnace slag (CaO: 43.
An erosion agent consisting of 4 wt% and SiO ₂ : 33.5 wt%) = 30: 1 was dissolved at 1600 ° C., and the size of the maximum erosion site day was measured.

Spalling resistance: After heating to 1500 ° C. in a non-oxidizing atmosphere with nitrogen gas, air-cooling was repeated, and the crack generation was repeated in three stages (亀: excellent; Δ: poor; ×: large) Inferior.)

Practical machine test: Poured into the metal line section of the blast furnace gutter with a thickness of 300 mm, and after passing about 30,000 tons of iron, the wear size at the maximum wear site was measured to determine the wear rate.

[0033]

【table 1】

[0034]

[Table 2]

[0035]

[Table 3]

FIG. 2 is a graph showing the relationship between the proportion of the ultrafine calcined spinel powder and the corrosion resistance of the refractory. This test was carried out based on the composition of Example 2 while changing the ratio of the calcined spinel ultrafine powder. The erosion size is 100 when the proportion of calcined spinel ultrafine powder is 0 wt%.
The smaller the value, the better the corrosion resistance.

As shown in the test results in Table 2, the embodiment of the present invention has both the corrosion resistance and the spalling resistance required for the lining of the blast furnace gutter. As a result, the durability of the actual machine is significantly improved as compared with conventional materials. Further, among them, silicon carbide is not used, or the ratio of silicon carbide is 10%.
Those having less than wt% are more excellent in corrosion resistance.

On the other hand, in Comparative Example 1 shown in Table 3, spinel was used, but since it was not a calcined spinel ultrafine powder, the corrosion resistance was poor. Comparative Example 2 in which no spinel was used, including the calcined spinel ultrafine powder, was also inferior in corrosion resistance. Comparative Example 3, in which the proportion of the calcined spinel ultrafine powder was large, was inferior in spalling resistance and is not shown in the table.

In Comparative Example 4, the proportion of silicon carbide was large, and the corrosion resistance was poor. Comparative Example 5 does not contain carbon, and has significantly poor spalling resistance. Also in Comparative Example 6 in which the proportion of the entire spinel including the calcined spinel ultrafine powder was large, the spalling resistance was inferior, and as in Comparative Example 3, there was a concern about stable use due to the metal ingot.

Further, from the graph of FIG. 2, it is confirmed that the calcined spinel ultrafine powder has excellent corrosion resistance within the range limited within the scope of the present invention. If the proportion of the calcined spinel ultrafine powder exceeds the upper limit of the present invention, the corrosion resistance is not dark, but the spalling resistance is reduced and the service life is ultimately inferior.

[0041]

The castable refractory for blast furnace gutters of the present invention has an excellent service life as shown by the test results of the above embodiments. As a result, it contributes to the efficiency of tapping work, the reduction of refractory basic unit, and the like, and its industrial value is extremely high.

[Brief description of the drawings]

FIG. 1 is a cross section perpendicular to the length direction of a blast furnace gutter and schematically shows the state of wear of a lining.

FIG. 2 is a graph showing the relationship between the amount of ultra-fine calcined spinel powder used and the corrosion resistance of a refractory (indicated by a erosion index).

[Explanation of symbols]

 1 Slag 2 Hot metal 3 Slag line section 4 Metal line section 5 Steel 6 Perm brick

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[Procedure amendment]

[Submission date] February 2, 1999 (1999.2.2)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0032

[Correction method] Change

[Correction contents]

Actual machine test: Thickness of 30 in metal line part of blast furnace gutter
The casting was carried out at 0 mm, and after passing about 30,000 tons of iron, the wear dimension at the maximum wear site was measured to determine the wear rate. Ten
00 × wear size / iron throughput = wear rate (mm / 100t). What
If the test result column is blank, the test was not performed.
Is shown.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0034

[Correction method] Change

[Correction contents]

[0034]

[Table 2]

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0035

[Correction method] Change

[Correction contents]

[0035]

[Table 3]

Claims (5)

[Claims] The composition of the refractory aggregate is 1 to 20 wt% carbon, M
gO · _Al 2 _{O 3} based calcined spinel micronized 1 to 20 wt%,
Castable refractory for blast furnace gutters containing 0 to 20 wt% of silicon carbide and 20 to 95 wt% of alumina. 2. The composition of a refractory aggregate having a carbon content of 1 to 20 wt%, M
gO · _Al 2 _{O 3} spinel 1~70wt%, silicon carbide 0
Contains 20wt%, 20-95wt% alumina and refractory aggregate
1 to 20 w of the spinel in proportion to 100 wt%
A castable refractory for blast furnace gutters in which t% is MgO.Al ₂ O ₃ -based calcined spinel ultrafine powder. 3. The castable refractory for a blast furnace gutter according to claim 1, wherein the MgO.Al ₂ O ₃ based calcined spinel ultrafine powder has an average particle size of 5 μm or less. 4. The castable refractory for a blast furnace gutter according to claim 1, wherein the calcination temperature of the MgO.Al ₂ O ₃ -based calcined spinel ultrafine powder is 1600 ° C. or lower. 5. The castable refractory for a blast furnace gutter according to any one of claims 1 to 4, wherein the castable refractory for a blast furnace gutter is for a blast furnace gutter metal line.