JP2000095576A - Magnesia-alumina-silica monolithic refractory for execution by slip casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a monolithic refractory capable of being executed by slip casting method, which is suitable as a refractory for a molten steel vessel such as a molten steel ladle a tundish and a vacuum degassing apparatus or an apparatus for treating the molten steel. SOLUTION: The objective refractory is a magnesia-alumina-silica slip casting material and has a composition, wherein a refractory filler comprises 70-98 wt.% magnesia raw material 1-28 wt.% alumina raw material and 0.5-7 wt.% volatile silica. At least 15 wt.% based on 100 wt.% of the refractory filler, of the magnesia raw material is composed of a magnesia raw material containing 0.8-8 wt.% Al2O3 and 1-7 wt.% SiO2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an irregular-shaped refractory for pouring work suitable as a refractory for use in a molten steel vessel or a molten steel processing apparatus.

[0002]

2. Description of the Related Art Refractories used in molten steel containers such as ladle ladles, tundishes, vacuum degassing equipment, or molten steel processing equipment are cast from conventional fixed refractories for the purpose of labor-saving construction, etc. Attempts have been made to use refractories (hereinafter referred to as pouring materials).

[0003] As a material of the casting material, for example,
JP-A-97526 and JP-A-8-2975 propose alumina-magnesia pouring materials.
This material, in addition to the corrosion resistance of each of the alumina raw material and the magnesia raw material, is obtained by reacting the alumina raw material and the magnesia raw material at a high temperature during use.
Slag permeation resistance is imparted by gO.Al ₂ O ₃ spinel (hereinafter simply referred to as spinel).

[0004]

In recent years, operating conditions of a molten steel container and a molten steel apparatus have become severe due to an increase in molten steel temperature, a prolonged residence time, and gas blowing agitation. For this reason, the pouring material used therein is not sufficient, even if it is made of alumina-magnesia, and a material having excellent durability is strongly desired.

[0005]

SUMMARY OF THE INVENTION The present invention is a magnesia-alumina-silica casting material, which is characterized in that the refractory aggregate is composed of 70-98 wt% of a magnesia raw material, 1-28 wt% of an alumina raw material and Volatile silica 0.5 ~ 7wt%
And at least 15 wt% of the magnesia-based raw material is Al in a proportion of 100 wt% of the refractory aggregate.
A magnesia raw material containing 0.3 to ₃ wt% of ₂ O _{3 and 1 to} 7 wt% of SiO ₂ is used.

[0006] The other composition of the present invention is:
Refractory aggregate is magnesia feedstock 30~98wt%, alumina-based material _{1~28wt%, MgO · Al 2 O} 3 spinel material 40
wt.% or less and 0.5 to 5 wt.% of volatile silica, and at least 15 wt.% of the magnesia-based material is Al ₂ O ₃ : 0.3 to ₃ wt.
% And SiO ₂ : 1 to 7 wt%, and the total amount of the magnesia material and the MgO · Al ₂ O ₃ spinel material in the refractory aggregate is 70 to 98 w.
t%.

[0007] In the conventional alumina-magnesia pouring material, the ratio of the magnesia raw material is smaller than the ratio of the alumina raw material. For example, in Japanese Patent Application Laid-Open No. Hei 5-97526, the amount of magnesia-based material is 3 to 10% by weight, and in Japanese Patent Application Laid-Open No. 8-2975, the amount of magnesia is 2 to 20% by weight. On the other hand, in the present invention, the ratio of the magnesia raw material in the refractory aggregate is as large as 70 to 98 wt%.

Although the magnesia raw material has a high melting point, it is inferior in spoiling resistance and slag resistance, so that when the mixing ratio is excessive, the durability of the cast material is reduced. This reduces the proportion of the magnesia raw material in the conventional material.

[0009] The casting material of the present invention increases the proportion of the magnesia raw material and at the same time suppresses the deterioration of the spoiling resistance and the slag permeation resistance due to the increase of the magnesia raw material. Therefore, as a result of fully exhibiting the corrosion resistance effect of the magnesia-based raw material, it was possible to obtain more excellent durability than the conventional material.

[0010] magnesia raw material used in the present invention by containing SiO ₂ of a specific amount, the SiO ₂ based low melting point material such as 2MgO · SiO _2, MgO · SiO ₂ at a high temperature at the time of refractory used The generated magnesia-based raw material relaxes the thermal expansion stress of the magnesia raw material itself, which acts to suppress a decrease in spalling resistance.

Since the magnesia raw material used in the present invention further contains a specific amount of Al ₂ O ₃ , this Al ₂ O ₃ is a main component of the magnesia raw material at a high temperature when a refractory is used. Reacts with MgO to produce spinel. Then, as a result of the spinel being formed, the refractory structure is given residual expansion, and as a result, the cast material has a dense refractory structure and has slag penetration resistance.

The refractory in the slag line of the molten steel pot or the dip tube of the vacuum degassing device is used in contact with the slag line, and is repeatedly subjected to heat shock by the vertical movement of the molten steel surface. The effect of the cast material of the present invention becomes more remarkable in the use of a molten steel ladle slag line or a dip tube for a vacuum degassing device due to its excellent spoiling resistance and slag penetration resistance.

FIG. 1 is a longitudinal sectional view showing a use state of a dip tube for a vacuum degassing apparatus. The immersion tube (1) is configured by covering the inner and outer circumferences of a cored bar (2) with a refractory (3). During the use of the immersion pipe (1), the structure of the refractory (3) is decompressed by the flow of the molten steel (4) in the immersion pipe (1), so that slag penetration is likely to occur. Further, when air enters under the reduced pressure, there arises a problem of so-called nitrogen pickup in which nitrogen of air components is contaminated by molten steel.

The casting material of the present invention, when used as a refractory for a dip tube for a vacuum degassing device, prevents the problems of slag permeation and nitrogen pickup due to the reduced pressure, due to its spalling resistance and dense structure. be able to.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The magnesia raw material used in the present invention is a sintered or electrofused product of a synthetic raw material or a natural raw material. If the ratio of the magnesia raw material to the refractory aggregate is less than 70 wt%, the corrosion resistance is poor. If it exceeds 98 wt%, the amount of spinel produced by the reaction with the alumina-based raw material will be small, and the slag penetration resistance will be poor.

According to the present invention, at least 15 wt% of the magnesia raw material is contained in 100 wt% of the refractory aggregate.
%, Al ₂ O ₃ : 0.3 to ₃ wt% and SiO ₂ : 1 to 7 w
It is a magnesia raw material containing t%. If the Al ₂ O ₃ content of the magnesia material is less than 0.3 wt%, the effect of slag penetration resistance cannot be obtained, and if it exceeds 3 wt%, the slag penetration resistance is inferior, possibly due to excessive residual expansion. on the other hand,
If the content of SiO ₂ is less than 1 wt%, the spalling resistance is poor, and if it exceeds 7 wt%, the corrosion resistance is lowered, possibly due to the formation of a low melting point substance.

The proportion of the magnesia-based raw material having specified contents of Al ₂ O ₃ and SiO ₂ is 100 wt% of the refractory aggregate.
At least 15 wt%, more preferably at least 30 wt%, of the whole magnesia raw material. If it is less than 15 wt%, the effects of spalling resistance and denseness described above cannot be obtained.

The alumina raw material reacts with the magnesia raw material to form spinel, and this spinel forms Fe in the slag.
Components such as O and MnO are dissolved. Further, the refractory structure is densified by the volume expansion accompanying the spinel formation. And the effect of slag penetration resistance is given by this solid solution and densification.

The alumina raw material is a sintered product or an electrofused product made of a synthetic raw material or a natural raw material. Further, the fine powder portion may be a calcined product which is a kind of a sintered product. The proportion of the alumina raw material in the refractory aggregate is inferior to the effect of slag penetration resistance if it is less than 1 wt%, and it is inferior if it exceeds 28 wt%.
The effect of the corrosion resistance of the present invention cannot be obtained because the proportion of the magnesia raw material is small.

Volatile silica is an amorphous silica powder obtained as a by-product in the production of silicon or a silicon alloy, for example, and is commercially available under a trade name such as silica flour or microsilica. The specific surface area is, for example, 10 to 50 m ² /
g of ultrafine particles. It has the effect of preventing hydration of magnesia and imparting fluidity during casting. If the proportion in the refractory aggregate is less than 0.5 wt%, the effect of preventing hydration and imparting fluidity is poor, and if it exceeds 7 wt%, the corrosion resistance is reduced due to the formation of a silica-based low melting point substance.

The refractory aggregate used in the present invention may be combined with other refractory raw materials as long as the effects of the present invention are not impaired. For example, part of the magnesia raw material is A
It may be replaced with l ₂ O ₃ .MgO-based spinel material (hereinafter referred to as spinel material).

The spinel material has spinel as a main component,
Has the effect of slag penetration resistance. Either a sintered product or an electrofused product may be used. The ratio in the refractory aggregate is 40 wt% or less. If it exceeds 40% by weight, the proportion of magnesia decreases and the corrosion resistance is poor.

When the spinel material is used, the lower limit of the proportion of the magnesia material can be reduced to 30 wt% because of the slag penetration resistance of the spinel material. When a spinel material is used, the total amount of the magnesia material and the spinel material is set to 70 to 98 wt% in order to obtain the effect of corrosion resistance in the present invention.

In the present invention, organic fibers, binders, deflocculants, refractory coarse particles and the like may be added, if necessary, as in the case of the conventional casting material. For example, organic fibers are vinylon (PVA)
), Rayon, polyester, nylon, polypropylene, polyethylene, etc., and the addition amount thereof is preferably 0.01 to 1% by weight based on 100% by weight of the refractory aggregate.

The binder is, for example, alumina cement, magnesia cement, Portland cement, phosphate, silicate and the like. The ratio is preferably 1 to 10% by weight based on 100% by weight of the refractory aggregate. In the present invention, when a part of the magnesia raw material used for the refractory aggregate has a sufficient role as a magnesia cement, it is not always necessary to add a binder.

The addition of a deflocculant has the effect of imparting fluidity during construction of the cast material. Specific examples include inorganic salts such as sodium tripolyphosphate, sodium hexametaphosphate, sodium ultrapolyphosphate, sodium acid hexametaphosphate, sodium borate, and sodium carbonate, sodium citrate, sodium tartrate, sodium polyacrylate, and sodium sulfonate. and so on. The addition amount is preferably 0.01 to 0.5% by weight on the basis of 100% by weight of the refractory aggregate.

The refractory coarse particles have a role of preventing the cracks generated in the structure of the cast material from developing.
The material is not limited, but for example, an alumina raw material, a spinel raw material, a magnesia raw material made of a sintered product or an electrofused product, or a refractory waste material mainly composed of these materials can be used. The ratio with respect to the refractory aggregate of 100 wt% is 40 wt% or less, preferably 10 to 20 wt% in outer case.

The maximum particle size of the refractory aggregate is generally 8 mm or less, whereas the particle size of the refractory coarse particles is about 10 to 50 mm. Therefore, the refractory aggregate and the refractory coarse particles are distinguished. Further, a clay, a curing modifier, a metal fiber (for example, stainless steel fiber), a ceramic fiber, a glass powder, a basic aluminum lactate, a carbon powder, a pitch powder, a metal powder, a foaming agent, and the like may be added.

The method for applying the cast material according to the present invention is not different from the conventional cast material. That is, about 4 to 8 wt% of construction water is externally added to and mixed with the casting material composition,
It will be poured. Further, it may be used as a precast product which has been pre-constructed.

[0030]

EXAMPLES Tables 1 and 2 show the chemical analysis values of the refractory aggregate used in each example. Table 3 shows the results of the spalling resistance test for each test example. FIG. 2 is a graph showing the results of a slag penetration resistance test for each test example. Tables 4 and 5 show examples of the present invention and comparative examples.

Table 4 shows examples and comparative examples centering on a cast material mainly composed of a magnesia-based material and an alumina-based material as a refractory aggregate. On the other hand, each example in Table 5 is an example and a comparative example centered on a casting material mainly composed of a magnesia-based material, an alumina-based material and a spinel material. The magnesia raw material used in the present invention is a sintered product or an electrofused product made of a synthetic raw material or a natural raw material. The proportion of magnesia raw material in refractory aggregate is 70%
If it is less than wt%, the corrosion resistance is poor. If it exceeds 98 wt%, the amount of spinel produced by the reaction with the alumina-based raw material will be small, and the slag penetration resistance will be poor.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

[Table 3]

[0035]

[Table 4]

[0036]

[Table 5]

In each of the examples, the compounds shown in Tables 4 and 5 were kneaded at an external moisture content of 6 wt%, poured into a mold, cured, and cured.
A sample dried at 24 ° C. for 24 hours was used as a test piece. The test method is as follows.

Corrosion resistance; Steel slag by weight ratio: converter slag (Fe
(O content; 20 wt%) = 70:30
A rotary erosion test at 650 ° C. × 5 hours was performed to measure the erosion size.

Slag permeation resistance: After performing a rotational erosion test under the above conditions, the slag permeation dimension was measured.

The erosion dimensions in the corrosion resistance and the slag penetration dimensions in the slag penetration resistance are shown in Table 4 in Examples 2 and 5.
In each of the examples 1 is shown by an index of 100,
The smaller the numerical value, the smaller the erosion or penetration size.

Spalling resistance: After heating at 1600 ° C. × 5 minutes,
Air-cooling was repeated 5 times, and the state of crack generation was observed. From the results, the degree of crack generation was evaluated on a four-point scale (1 with the least crack generation, 4 with the most crack generation). ).

Actual machine test: Each example shown in Table 4 was 180 t
Of the immersion pipe of the RH type vacuum degassing apparatus was used as a refractory at the outer periphery and the lower end. The dimensions of the construction body are 700m in height
m, outer peripheral thickness 60 mm, lower end thickness 130 mm (total of outer peripheral thickness and inner peripheral thickness). Pouring using a formwork,
After heating and drying at about 500 ° C., it was used. The service charge of the immersion tube was determined, and the superiority was determined.

Each of the examples shown in Table 5 was used as a refractory at the outer periphery and at the lower end of a dip tube of a 200 t RH vacuum degassing apparatus. The dimensions of the construction body are a height of 750 mm, an outer peripheral thickness of 65 mm, and a lower end thickness of 140 mm (total of the outer peripheral thickness and the inner peripheral thickness). Thereafter, the superiority was determined in the same manner as in the case of the RH type vacuum degassing device of 180 t.

Table 3 shows that in the cast material of Example 1 shown in Table 4, only the sintered magnesia having a particle size of 5 to 1 mm was changed to the materials A to H shown in Table 1, and the Sm in the magnesia raw material was changed.
It shows the relationship between the ratio of the iO ₂ component and the sporin resistance of the casting material. From the results of this graph, it is confirmed that the ratio of SiO ₂ contained in the magnesia raw material is excellent in sporin resistance within the range of the present invention.

The graph of FIG. 2 shows that, for the cast material of Example 2 shown in Table 3, only the sintered magnesia having a particle size of 5 to 1 mm was changed to the materials A to H shown in Table 1, and ₂ shows the relationship between the ratio of the Al ₂ O ₃ component and the slag penetration resistance. From the results of this graph, it is confirmed that the slag penetration resistance is good when the proportion of Al ₂ O ₃ contained in the magnesia-based material is within the range of the present invention.

From the test results of the examples in Tables 3 and 4, all of the examples of the present invention have slag penetration resistance, spalling resistance and corrosion resistance. Further, the durability in actual machine tests is much better than those of Comparative Examples 1 and 7 corresponding to conventional materials.

Although not shown in the test results here, the material of the present invention is excellent in spalling resistance and has a high density of the structure. It was effective in preventing slag penetration and preventing nitrogen pickup, which causes contamination of molten steel.

On the other hand, in Comparative Example 2, the amount of the magnesia raw material was small, and the corrosion resistance was poor. In Comparative Example 8, the combined amount of the magnesia-based material and the spinel-based material was small, and the corrosion resistance was poor. In Comparative Examples 3 and 9, the proportion of the magnesia-based raw material in which the proportions of Al ₂ O ₃ and SiO ₂ were specified was small, and the spalling resistance was poor. Comparative Example 4 and Comparative Example 10 did not contain an alumina raw material and were inferior in slag penetration resistance and spalling resistance.

In Comparative Examples 5 and 11, the proportion of volatile silica was large and the corrosion resistance was poor. Comparative Example 6 did not contain a magnesia-based raw material having a specified ratio of Al ₂ O ₃ and SiO ₂ , and was inferior in both spalling resistance and slag penetration resistance. In Comparative Example 12, the spinel-based raw material was large, and the magnesia-based raw material was reduced accordingly, resulting in poor corrosion resistance.

[0050]

As is clear from the test results of the above examples, the cast material according to the present invention has excellent spalling resistance and slag penetration resistance as compared with conventional alumina-magnesia cast material, for example. From its durability, it greatly contributes to improving the operation rate of molten steel containers or molten steel processing equipment.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a use state of a refractory for an immersion pipe for a vacuum degassing apparatus.

[Fig. 2] In a casting material, A in a magnesia raw material
It shows the relationship between the ratio of the l ₂ O ₃ component and the slag penetration resistance.

[Explanation of symbols]

 1 dip tube 2 core 3 inner and outer refractories 4 molten steel

Claims (2)

[Claims] The refractory aggregate is a magnesia-based raw material of 70 to 98 wt.
%, Alumina raw material 1 ~ 28wt% and volatile silica 0.5 ~
Comprises 7 wt%, a proportion of the refractory aggregate 100 wt%, at least 15 wt% Al ₂ O of the magnesia raw material _{3: 0.3~3wt%} and SiO _2: and the magnesia raw material containing 1～7Wt% Magnesia-alumina-silica-based refractory for casting. 2. The refractory aggregate is composed of a magnesia raw material of 30 to 98 wt.
%, Alumina raw material 1-28 wt%, MgO.Al ₂ O ₃ based spinel raw material 40 wt% or less and volatile silica 0.5-5 wt
% Comprises, as a proportion of the refractory aggregate 100 wt%, at least 15 wt% of the magnesia feedstock Al ₂
A magnesia raw material containing 0.3 to ₃ wt% of O _{3 and 1 to} 7 wt% of SiO _2, and the total amount of the magnesia raw material and the MgO · Al ₂ O ₃ spinel raw material in the refractory aggregate is 70 to 70%. An amorphous refractory for magnesia-alumina-silica pouring work with 98 wt%.