JPH0725668A - Refractory for casting work - Google Patents

Abstract

PURPOSE:To obtain a refractory for casting work having a longer life than a conventional material. CONSTITUTION:This refractory for casting work comprises a main aggregate consisting of 2-15wt.% of sintered and/or electromelted magnesia, 1-15wt.% of alumina cement and the remaining part of alumina, wherein 2-10wt.% out of the 2-15wt.% of magnesia is superfine powdery magnesia having a maximum powder diameter of <=10mum and an average particle diameter of 0.1-3mum. Further, <=2wt.% of metallic aluminum powder and/or aluminum alloy powder is compounded before using.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refractory for casting, which is used for lining molten metal containers or for heat-resistant coating of thermal equipment in the steel industry.

[0002]

The lining of molten metal containers used in the steel industry is shifting from conventional brick laying to amorphous refractory. In addition, because of the ease of construction, castable refractories are the most prevalent among irregular refractories.

Examples of materials for casting refractories include alumina-spinel material disclosed in JP-A-64-87577, alumina-magnesia material disclosed in JP-A-5-97526, and alumina-spinel disclosed in JP-A-3-23275. -Magnesia quality has been proposed. They exhibit excellent durability due to the volume stability of alumina and the corrosion resistance of magnesia or spinel.

[0004]

Recently, the vacuum degassing method,
With the adoption of continuous casting, ladle refining, etc., the operating conditions of the molten metal container have become extremely severe, such as rising molten steel temperature, extending the staying time of molten metal, and stirring with gas blowing. As a result, conventional cast-in refractories are no longer adequate.

An object of the present invention is to obtain a refractory for casting which has a life longer than that of conventional materials.

[0006]

The present invention is a method of sintering and / or
Alternatively, electro-melting magnesia: 2 to 15% by weight, alumina cement: 1 to 15% by weight, and the balance mainly composed of alumina, and 2 to 15% by weight of the magnesia: 2 to 15% by weight.
10% by weight has a maximum particle size of 10 μm or less, an average particle size of 0.1
It is a refractory for pouring construction made of 3 μm magnesia ultrafine powder. Further, it is a refractory for casting, which is obtained by adding metal aluminum powder and / or aluminum alloy powder: 2% by weight or less to the outside of the casting.

In the present invention, ultrafine magnesia powder is used.
The ultrafine magnesia powder reacts with alumina at a high temperature during use to form MgO.Al ₂ O ₃ spinel. This spinel dissolves components such as FeO and MgO in the slag, has a function of preventing slag from penetrating into the refractory structure, and is effective in improving corrosion resistance.

The use of magnesia fines, and the reaction of the magnesia fines with alumina to form spinels, is known in the aforementioned prior publications. However, conventionally, the fine powder of magnesia used there is 1 m.
The particle size is m or less, 0.1 mm or less, and less than 0.21 mm. It is not an ultrafine powder having a maximum particle size of 10 μm or less and an average particle size of 0.1 to 3 μm used in the present invention.

A large amount of construction water is added to the refractory for pouring construction at the time of use. Magnesia causes the following hydration reaction with this construction water, and the volume of the magnesia expands. Further, the volume expansion also occurs due to spinel formation due to the reaction with alumina.

The reaction of hydration and spinel formation becomes more remarkable as magnesia becomes finer. The volume expansion causes weakening of the refractory structure, which in turn lowers the corrosion resistance of the refractory. For these reasons, in the alumina-magnesia type refractory for pouring construction, conventionally, 0.0
Magnesia finer than 75 mm or less (200 mesh) has never been used.

On the other hand, in order to prevent the hydration reaction, it is effective to add ultrafine silica powder called silka flour or micro silica. However, since ultrafine silica powder forms a low melting point substance that causes a decrease in corrosion resistance, the amount of addition is naturally limited. This is because adding an amount sufficient to prevent the hydration reaction of magnesia ultrafine powder causes a decrease in corrosion resistance.

On the other hand, in the present invention, in the alumina-magnesia type refractory for casting, magnesia fine powder is further finely divided and used as ultrafine powder having a maximum particle size of 10 μm or less and an average particle size of 0.1 to 3 μm. As a result, the effect of volume expansion due to hydration and spinel formation is reduced, and as a result, it was found that the effect of slag permeation resistance due to spinel formation of alumina-magnesia reaction is exerted at all, and the present invention was completed. It is a thing.

The reason is considered to be as follows. That is, magnesia used in the present invention, in the refractory structure for ultrafine powder, coarse particles constituting the refractory,
It is located in the space between medium and fine aggregate particles. And
The volume expansion of magnesia due to hydration and spinel formation is because magnesia, which is ultrafine powder, is formed within the space between the aggregate particles and does not significantly affect the volume expansion of the refractory structure as a whole. Moreover, since the magnesia ultrafine powder, which is finer than the magnesia fine powder, has a large specific surface area, spinel formation due to the reaction with alumina is more significantly performed. Therefore, the material of the present invention not only suppresses the influence of the hydration reaction of magnesia [MgO + H ₂ O → Mg (OH) ₂ ], but it also produces more remarkable spinel due to the use of ultrafine magnesia powder, and thus the slag penetration resistance is improved. Is further improved, and the durability is far superior to that of conventional materials.

In the conventional material, for example, 0.07
If it is less than 5 mm (200 mesh), 200
Meaning under a standard sieve such as a mesh, and although there is no ultrafine powder, the amount is extremely small. According to the particle size distribution, about 50% of the particle size is equal to or larger than half the maximum particle size.
The following particles are at most 10% by weight. And this,
Even if particles of 0.075 mm or less are blended in an amount of 15% by weight, particles of 10 μm or less account for at most 1.5% by weight, which is outside the scope of the present invention.

The present invention relates to the use of magnesia ultrafine powder.
To a certain amount of aluminum metal powder, hydration
The influence is further reduced and the strength characteristics are further improved.
You can This is a metal aluminum powder,
The following reaction occurs with Nesia ultrafine powder and construction water.
The produced magnesium aluminum hydrate is M described above.
g (OH)₂Unlike the fact that there is no volume expansion
It is thought to be. In addition, metallic aluminum powder has a low melting point.
Quality, but effective in small amounts of less than 2% by weight
Since it does not require a large amount to be added, the problem of reduced corrosion resistance
Nor. Mg²⁺+ Al³⁺+ H₂O → Mg₂Al (OH)₇, MgA
l₂(OH)₈  It has not been possible to add metallic aluminum powder to amorphous refractories.
Known to. However, conventionally, oxidation of carbon-containing refractories
Prevention, or H₂Due to the formation of vent holes due to gas generation
The purpose of this is to prevent dry explosion, etc.
Combination of luminium powder and magnesia ultrafine powder and it
The effect of the present invention according to is not known.

1 to 3 are all based on a refractory for pouring construction having the composition of Example 2 as a base, and magnesia fine powder (corresponding to magnesia fine powder B in Table 1 below) or magnesia ultrafine powder (Table 1 below). (Corresponding to the magnesia ultrafine powder D) of the above) is changed to graph the relationship with various physical properties of the construction body. The proportion of sintered alumina 0.074 mm was changed as the magnesia source was increased or decreased.

FIG. 1 shows the relationship with the volume expansion of the construction body due to drying. FIG. 2 shows the relationship with the volume expansion of the construction body due to high temperature heating. FIG. 3 shows the relationship with the slag penetration resistance. As shown in FIG. 1 and FIG. 2, it is confirmed that the volume expansion of the magnesia ultrafine powder within the scope of the present invention decreases in both drying and high temperature heating in both drying and high temperature heating. . Further, from FIG. 3, it is recognized that the combination of magnesia ultrafine powder has an effect on the slag penetration resistance.

FIGS. 4 and 5 are based on the refractory for pouring construction of the composition of Example 6 and varied only the proportion of metallic aluminum. FIG. 4 shows the relationship with the volume expansion of the construction body due to drying, and FIG. 5 shows the strength characteristic relationship. From these, it can be seen that the addition of metallic aluminum further reduces the volume expansion of the construction body due to drying and further improves the strength characteristics. This tendency is the same even when aluminum alloy powder is used instead of metallic aluminum.

In FIGS. 1 to 5, the tests of volume expansion and strength characteristics were the same as those shown in the section of Examples described later.

The proportion of magnesia in the present invention is 2 to
15% by weight. Of these 2 to 15% by weight, 2 to 10% by weight have a maximum particle size of 10 μm or less and an average particle size of 0.1 to 3 μm.
And magnesia ultrafine powder. The total amount of magnesia is 2
Within the range of 15% by weight, it may be used in combination with magnesia having a particle size larger than that of ultrafine magnesia powder.

The ultrafine magnesia powder used in the present invention is a sintered product and / or an electromelted product. If there are many components such as SiO ₂ and CaO, a low-melt material is generated, which causes deterioration of corrosion resistance and structural spalling. Therefore, the MgO purity is preferably 90% by weight or more.

Other than this, light burned magnesia is known as ultrafine magnesia powder, but light burned magnesia is obtained by heat-treating magnesium hydroxide at a low temperature of 1000 ° C. or lower and is not sintered. Therefore, light burned magnesia is extremely active, and in the cast material it destroys the connective structure of the alumina cement by the hydration reaction,
Weaken the refractory structure. Also, the corrosion resistance is inferior due to the texture property of the light burned magnesia itself which is not sintered. Therefore, even if the light burned magnesia is an ultrafine powder, the effect of the present invention cannot be obtained. In addition, even when light burned magnesia is added together, the amount must be suppressed as much as possible.

In the magnesia ultrafine powder of the present invention, if the ratio is smaller than the range of the present invention or if the particle size is large, the effect of slag penetration resistance cannot be obtained because spinel formation is insufficient. If the proportion of the ultrafine powder of magnesia exceeds 10% by weight, the amount of the ultrafine powder becomes excessive and the refractory structure becomes excessively densified, resulting in poor spalling resistance. Although it is preferable that the chemical composition has a high MgO purity, a sintering agent may be added to which a minute amount of Al ₂ O ₃ , Cr ₂ O ₃ or the like is added. The average particle size of magnesia ultrafine powder is 0.1 μm.
When the amount is less than the above, the hydration reaction tends to destroy the connective structure due to the hydrated alumina cement as seen when using light burned magnesia and weaken the refractory structure.

Although ultrafine magnesia powder is used in the present invention, it is not effective as a binder because it is a sintered product or an electromelted product and has a small hydration reaction unlike light burned magnesia. Therefore, the present invention uses alumina cement as a binder. If the proportion is less than 1% by weight, the strength of the construction body is poor, and if it exceeds 15% by weight, the corrosion resistance is lowered.
Alumina is a refractory material having corrosion resistance and volume stability, and has a role as a main aggregate in the material of the present invention.
Coarse grains, medium grains, and fine grains are adjusted in the same manner as conventional materials so that a densely packed structure can be obtained. It is an electromelted product and / or a sintered product. A calcined product may be used for the fine particles. Further, if necessary, coarse particles having a particle diameter of 10 to 20 mm may be partially used.

Generally, a high purity alumina is preferable,
It may contain about ₁ to 8 wt% of TiO ₂ . Even when a low-purity product such as shale shale, sillimanite, or mullite is used, it is preferable to use a high-purity product in the fine powder portion.

The effect of the metallic aluminum powder is the same for the aluminum alloy powder. Examples of the aluminum alloy powder include Al-Si, Al-Mg, and Al-Si-M.
g, etc. However, since the aluminum metal powder and / or the aluminum alloy powder is a low melting point substance, if the content of the outer aluminum exceeds 2% by weight, the corrosion resistance of the refractory material is deteriorated. Further, in order to sufficiently bring out the effect of this addition, the lower limit ratio is 0.1% by weight on the outside.

In order to adjust workability and pot life at the time of construction, 0.01% of peptizer and hardening control agent, etc.
The addition of about 0.5 wt% is similar to the conventional material. Specific examples of the deflocculating agent include, for example, sodium tripolyphosphate, sodium hexametaphosphate, sodium ultrapolyphosphate, acidic sodium hexametaphosphate, sodium borate, sodium carbonate, etc., inorganic salts, sodium citrate, sodium tartrate, sodium polyacrylate. , Sodium sulfonate, etc. Examples of the curing modifier are boric acid, ammonium borate, ultrapolyphosphate sodium carbonate, lithium carbonate and the like.

If necessary, glass powder, carbon powder, pitch powder, zircon, zirconia, ultrafine silica powder, metal fiber,
Organic fibers, ceramic fibers, foaming agents, etc. may be added.

The construction is carried out in the usual manner by adding and mixing approximately 4 to 8% by weight of construction water to the above-mentioned composition, and pouring using a formwork. In order to improve the filling property at the time of construction, generally, a vibrator is attached to the form or a rod-shaped vibrator is inserted into the refractory.

[0030]

EXAMPLES Examples of the present invention and comparative examples are shown below.

Table 1 shows the quality of the raw materials used in each example. Tables 2 and 3 show the compounding composition of each example and the test results of the construction body.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

[Table 3]

In each example, 5% by weight of construction water and 0.1% by weight of a dispersant (sodium hexametaphosphate) were externally added, kneaded, and then poured into a form with vibration applied thereto, and after curing, It was dried at 110 ° C. for 24 hours. The test method is as follows.

Expansion line change rate: The change rate due to heating and drying is
After the pouring construction, heating was performed at 110 ° C. for 3 hours, and the linear change rate was obtained. The rate of change due to high temperature heating is 150
High temperature heating at 0 ° C for 3 hours was performed to determine the linear change rate. Spooling resistance: One-sided heating spool test (1400
The number of times until it came off was measured.

Bending strength; test piece dried at 110 ° C. or 1
What was heated at 500 ° C. was measured at room temperature to compare the strength of the construction bodies.

Corrosion resistance: Steel piece by weight ratio: converter slag (Fe
O content; 20% by weight) = 50: 50 as an erosion agent, 1
A rotary erosion test was performed at 650 ° C. for 3 hours, and the erosion size was measured.

Slag permeation resistance: The slag permeation dimension was measured after the rotary erosion test was conducted under the above-mentioned conditions.

Actual machine test: Used as a side wall lining of a 250 ton molten steel ladle, and after 150 charges were used, its wear size was determined.

In the embodiment of the present invention, the rate of change of the expansion line is small,
Good results are shown in both tests of corrosion resistance and slag penetration resistance. Moreover, the effect becomes more remarkable in Table 3 when the metal aluminum powder or the aluminum alloy powder is added. On the other hand, Comparative Examples 1 and 2 which do not use ultrafine magnesia powder and Comparative Example 3 in which the amount of ultrafine magnesia powder is less than the range of the present invention are inferior in corrosion resistance and slag penetration resistance, probably because spinel formation is insufficient. Comparative Example 4 uses ultrafine magnesia powder,
Since the blending amount is too large, it becomes over-sintered and inferior in spalling resistance. Even if the amount of ultrafine magnesia powder is within the range of the present invention, Comparative Example 5 in which the total amount of magnesia is too large is inferior in spalling resistance. Comparative Example 6 using lightly burned magnesia has a large volume expansion after drying due to a hydration reaction and is inferior in strength characteristics. Comparative Example 7 is particularly inferior in corrosion resistance because the amount of metallic aluminum powder added is too large. Comparative Example 8 does not use alumina cement and is inferior in strength and corrosion resistance. In Comparative Example 9, the strength is excellent but the corrosion resistance is poor because the amount of alumina cement is too large.

In the above examples, an actual machine test was conducted on a ladle, but the castable amorphous refractory material of the present invention is not limited to this, and a tundish, a converter, an electric furnace, a vacuum degassing furnace, a hot metal wheel, a hot metal furnace. It can be used as a heat-resistant coating for linings, dipping tubes for vacuum degassing furnaces, ladle refining freeboards, gas blowing lances, etc.

[0043]

As described above, the refractory for pouring construction according to the present invention is combined with the suppression of the volume expansion associated with the hydration reaction and the spinel formation reaction, and the conspicuous formation of spinel with alumina contained in the magnesia ultrafine powder. Its durability is significantly improved compared to conventional materials. In recent years, the conditions of use of molten metal containers have become extremely severe, and the high quality of refractory materials is strongly demanded accordingly, so the value of the present invention is great.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between a change in a mixing ratio of magnesia having different particle diameters and a volume expansion of a construction body due to drying.

FIG. 2 is a graph showing a relationship between a change in a mixing ratio of magnesia having different particle diameters and a volume expansion of a construction body due to high temperature heating.

FIG. 3 shows the relationship between the change in the mixing ratio of magnesia having different particle sizes and the slag penetration resistance.

FIG. 4 is a diagram showing the relationship between the amount of metallic aluminum added and the volume expansion of a construction body due to drying.

FIG. 5 shows the amount of metallic aluminum added and
It shows the relationship with the bending strength after drying at ℃.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Sakamoto 12 Nakamachi, Muroran City Shin Nippon Steel Co., Ltd. Muroran Works (72) Inventor Shumi Matsumoto 1-3-1, Niihama, Arai-cho, Takasago, Hyogo Prefecture Harima Ceramics Co., Ltd. (72) Inventor Toshihiro Isobe 1-3-1 Niihama, Arai-cho, Takasago, Hyogo Prefecture Harima Ceramics Co., Ltd. (72) Akekei Maekawa 1-3-1 Niihama, Arai-cho, Takasago, Hyogo Harima Ceramics Within the corporation

Claims (2)

[Claims] 1. Sintered and / or electrofused magnesia:
2-15% by weight, alumina cement: 1-15% by weight,
The balance is mainly made of alumina, and the magnesia:
2 to 10% by weight of 2 to 15% by weight has a maximum particle size of 10 μ
Refractory for pouring construction made of magnesia ultra-fine powder having an average particle diameter of 0.1 to 3 μm. 2. Sintered and / or electrofused magnesia:
2-15% by weight, alumina cement: 1-15% by weight,
The balance is a mixture containing alumina as the main aggregate, and external aluminum metal powder and / or aluminum alloy powder: 2
The magnesia: 2-1 is added by weight% or less.
A refractory for casting, wherein 2 to 10% by weight of 5% by weight is magnesia ultrafine powder having a maximum particle size of 10 μm or less and an average particle size of 0.1 to 3 μm.