JPH06345550A - Castable refractory - Google Patents

Abstract

PURPOSE:To obtain a castable refractory excellent in slag infiltration resistance, thermal shock resistance, durability, etc., by mixing a specific composition of spinel raw material, magnesia, alumina and a binder in a specified weight ratio. CONSTITUTION:(A) 10-40wt.% of spinel raw material, (B) 5-20wt.% of magnesia and (C) the balance the alumina and the binder are mixed to produce the castable refractory. In the A component, electrofused spinel is essentially used in the particle range from 0.05 to 2mm and also an additional quantity of the electrofused spinel is >=50wt.% for the total spinel additional quantity. Also the particle diameter range of the magnesia is <=5mm and a portion of alumina is composed of 2-8wt.% of superfine powder incorporated with >=50wt.% of particles diameter with <=3mum size. Besides 2-10wt.% of alumina cement is used as the binder and also the silica contained in the castable refractory is controlled to preferably be <=0.3wt.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a castable refractory used for lining a ladle for steelmaking.

[0002]

2. Description of the Related Art As a refractory material for lining a ladle for steel making, wax stone bricks, high-alumina refractory materials, zircon-based refractory materials, etc. are generally used. However, in recent years, alumina / spinel castable refractories have come to be used due to demands such as improvement of useful life (JP-A-64).
-83575 publication).

[0003]

However, the above-mentioned conventional alumina-spinel castable refractories have the following problems, and therefore have stable service lives when used as lining refractory materials for steel ladle. Can't get (1) Since the sintered spinel is used, infiltration with slag is large. This is because spinel is a very excellent material with respect to slag resistance, but in the sintered spinel particles, the crystal itself does not react with the slag, but the slag component easily enters the crystal grain boundaries. . Therefore, in the vicinity of the working surface of the refractory material, the sintered spinel particles are finely dispersed in the slag and flow out together with the slag by the molten steel flow. Therefore, infiltration of slag into the matrix portion becomes large, which causes structural spalling. (2) Cracks and peeling due to thermal shock are likely to occur. Therefore, an object of the present invention is to provide a castable refractory which can improve the slag infiltration resistance and the thermal shock resistance to further improve the service life.

[0004]

In order to solve the above-mentioned problems, the castable refractory material of the present invention is a spinel raw material 10
.About.40 wt%, magnesia 5 to 20 wt%, the balance consisting of alumina and binder, and the particle size range of 0.05 to 2 mm of the spinel raw material mainly uses the electrofusion spinel, and The addition amount is 50 wt% or more of the total spinel addition amount, the particle size range of magnesia is 5 mm or less, and the remaining alumina is 2 to 8 wt% of ultrafine powder containing 50 wt% or more of particles having a part of 3 μm or less. In addition, 2 to 10% by weight of alumina cement is used as a binder. Silica contained in the castable refractory is preferably 0.3% by weight or less.

Here, the spinel raw material means particles of magnesium aluminate (MgO.Al ₂ O ₃ ), and
The electrofused spinel is an electrofused product composed of 70 to 80% by weight of alumina and 20 to 30% by weight of magnesia.

[0006]

In the above means, the electrofused spinel particles are dense and have few crystal grain boundaries, and silica (S
Since low-melting point minerals containing iO ₂ ), calcia (CaO), etc. exist independently, no intrusion of slag into the crystal grain boundaries is observed. Magnesia (MgO) reacts with alumina (Al ₂ O ₃ ) in the matrix in the vicinity of the operating surface to generate a secondary spinel. The volume around the magnesia particles is densified due to the volume expansion during spinelization. On the other hand, in the low temperature range of the refractory in which the formation of secondary spinel does not occur, magnesia and the surrounding matrix have different thermal expansion coefficients, so that microcracks occur in the matrix around the magnesia particles. The addition of ultrafine alumina powder enables the matrix portion to form a dense structure. Also, the ultrafine alumina powder in the matrix reacts with alumina cement and magnesia when heated, and Ca0.6Al ₂
A needle-like crystal of O _{3 and} a secondary spinel are formed. This Ca0
・ 6Al ₂ O ₃ and the structure of the matrix portion are further densified due to volume expansion during the formation of the secondary spinel.
Alumina cement, as described above, when heated,
Reacts with alumina in the matrix, Ca0.6Al ₂
It produces needle crystals of O ₃ . Then, the structure of the matrix portion is densified by the volume expansion at the time of generation. On the other hand, if the amount of silica contained in the castable refractory is 0.
When the content is 3% by weight or less, the amount of low-melting point minerals such as grenite and anorthite produced in the reaction phase with slag is reduced, and oversintering when spinel and silica coexist is prevented. .

When the addition amount of spinel raw material exceeds 40% by weight, alumina is insufficient in the reaction phase with slag and calcia becomes excessive, and low melting point minerals are easily generated, which is a cause of structural spalling. Become. On the other hand, if the addition amount is less than 10% by weight, the effect of suppressing slag infiltration is small. Particles larger than 2 mm in the electro-melting spinel have a small effect of suppressing lubrication due to a small contact area with the slag. Therefore, the electro-melting spinel and the sintering spinel used are preferably 2 mm or less. Regarding the electrofused spinel, it is preferable that the grain size is 0.05 mm or more in order to make the best use of the size of the crystal, and in order to obtain a clear addition effect, the addition amount of 50% by weight or more of the total spinel addition amount. Is preferred.

When the addition amount of magnesia exceeds 20% by weight, the alumina component becomes insufficient in the slag infiltrated layer to form a low melting point mineral, which causes structural spalling. On the other hand, if the addition amount is less than 5% by weight, the effect of alleviating thermal shock is small. When the added particle size of magnesia exceeds 5 mm, large cracks occur around the magnesia particles.

If the amount of alumina ultrafine powder added exceeds 8% by weight, densification progresses, so that explosion tends to occur. On the other hand, if the addition amount is less than 2% by weight, the matrix portion becomes porous and the slag infiltration suppressing effect becomes small.

When the amount of alumina cement added exceeds 10% by weight, low-melting minerals such as grenite and anorthite tend to be produced in the reaction phase with slag, which causes structural spalling. On the other hand, if the addition amount is less than 2% by weight, the strength during construction becomes low.

[0011]

EXAMPLES Examples of the present invention will be described below. Examples 1 to 6 and Comparative Examples 1 to 6 The addition grain size of the electrofused spinel is set to 0.05 to 2 mm, the addition grain size of magnesia is set to 1 mm or less, and these and the sintered spinel, alumina and alumina cement are respectively shown in the table. 1, mixed with 5 to 6% by weight of water and cast into a curved plate having a fan-shaped end face as shown in FIG. 1, dried at 110 ° C. for 24 hours, and subjected to various tests. I got piece 1.

The test piece 1 was set in the induction furnace 2 as shown in FIGS. 2 and 3, and an erosion test was conducted. As the erosion agent 3, SS41, 60 kg, and 500 g of steelmaking furnace slag were used, kept at a temperature of 1600 to 1620 ° C. for 3 hours, and after cooling, the amounts of erosion loss and infiltration thickness were compared. Further, a columnar test piece of 40 × 40 × 160 mm was prepared from the above material, and a repeated heating test was repeated 5 times at a temperature of 1400 ° C. to measure the dynamic elastic modulus. The infiltration thickness and the spalling resistance index after the erosion test using the induction furnace are shown in Table 1, respectively. Here, the spalling resistance index means the ratio of the dynamic elastic modulus after five repeated heating tests, where the dynamic elastic modulus before heating is 100.

[0013]

[Table 1]

From Table 1, 10 to 40% by weight of spinel raw material, 5 to 20% by weight of magnesia, the balance alumina and alumina cement, and 0.
By making the particle size range of 05 to 2 mm the electrofused spinel and making the addition amount of the electrofused spinel 5 to 25% by weight of the total, it is possible to enhance the slag infiltration resistance by making the infiltration thickness 8 to 14 mm. On the other hand, the spalling resistance index is 4
It can be seen that the thermal shock resistance can be enhanced by setting it to 2 to 51%, and cracks and peeling do not occur.

Examples 7 to 8 and Comparative Example 7 The addition particle size of the electrofused spinel is 0.05 to 2 mm, and the addition amount is 15
% By weight, the addition amount of sintered spinel was 10% by weight, the addition amount of magnesia was 10% by weight, and the addition particle size was changed as shown in Table 2, and the addition amount of alumina and alumina cement was 65% by weight. And mixed to obtain each test piece as described above. The thickness of the infiltrated layer after the erosion test using the induction furnace of each test piece and the spalling resistance index after the repeated heating test are shown in Example 4.
The results are shown in Table 2 which also shows the results.

[0016]

[Table 2]

It can be seen from Table 2 that when the added particle size of magnesia is less than 5 mm, cracking or peeling does not occur.

Examples 9 to 12 and Comparative Examples 8 to 11 The addition particle size of the electrofused spinel was 0.05 to 0.2 mm, the addition amount was 15% by weight, and the addition amount of the sintered spinel was 10% by weight. Addition particle size of magnesia 1mm or less, addition amount 1
On the other hand, the addition amount of the alumina ultrafine powder and alumina cement containing 50% by weight or more of particles of 3 μm or less constituting the balance of alumina together with the alumina aggregate was changed as shown in Table 3 as described above. Obtained each test piece. The thickness of the infiltrated layer after the erosion test using the induction furnace of each test piece and the spalling resistance index after the repeated heating test were as shown in Table 3 together with the results of Example 4.

[0019]

[Table 3]

From Table 3, 2 to 8% by weight of ultrafine alumina powder, which constitutes a part of the remaining alumina, and 2-1 to alumina cement are used.
It can be seen that when the content is 0% by weight, a refractory material having excellent slag infiltration resistance and thermal shock resistance can be obtained. It can be seen that when the addition amount of the alumina ultrafine powder is less than 2% by weight, the thickness of the infiltration layer becomes large, and when the addition amount exceeds 8% by weight, it tends to explode during drying. When the amount of alumina cement added is less than 2% by weight, cracking occurs during demolding due to insufficient strength, and when the amount added exceeds 10% by weight, thermal shock resistance decreases and cracks and peeling occur. It can be seen that occurs.

Example 13 and Comparative Example 12 The addition particle size of electrofused spinel is 0.05 to 2 mm, and the addition amount is 1
5% by weight, the addition particle size of sintered spinel is 10% by weight, the addition particle size of magnesia is 1 mm or less, and the addition amount of ultrafine alumina powder is 5% by weight and the addition amount of alumina cement is 5% by weight. Meanwhile, the type of alumina aggregate was changed as shown in Table 4, and each test piece was obtained as described above. The thickness of the infiltrated layer after the erosion test using the induction furnace of each test piece and the spalling resistance index after the repeated heating test are shown in Table 4 together with the results of Example 4.
It came to be shown in.

[0022]

[Table 4]

From Table 4, when the content of silica in the castable refractory is 0.3% by weight or less, slag infiltration resistance,
It can be seen that a refractory having excellent thermal shock resistance can be obtained.

[0024]

As described above, according to the castable refractory of the present invention, the electromelting spinel particles are dense and have a small number of crystal grain boundaries, and also have a low melting point containing silica, calcia or the like in the crystal grain boundaries. Since the minerals exist independently, no penetration of the slag into the crystal grain boundaries is observed, so no collapse of the spinel crystal particles is observed, the initial shape is retained, and infiltration by the slag can be suppressed. . In addition, magnesia reacts with alumina in the matrix in the vicinity of the operating surface to generate a secondary spinel, and when this spinelization occurs, there is volume expansion, so the matrix around the magnesia particles becomes dense, so the slag While the infiltration can be suppressed, in the low temperature range of refractories where secondary spinel formation does not occur, the thermal expansion coefficient of magnesia and the surrounding matrix are different, so that microcracks occur in the matrix around the magnesia particles. Therefore, thermal shock can be mitigated, large cracks and peeling can be prevented from occurring, and the service life can be further improved. Furthermore, by adding ultrafine powder of alumina, the matrix portion forms a dense structure and reacts with the alumina cement during heating, so that Ca0.6Al ₂
Needle-like crystals of O ₃ and secondary spinel are formed,
6Al ₂ O ₃ , the volume expansion during the formation of the secondary spinel makes it more dense, so that the slag infiltration suppressing effect can be enhanced. Therefore, the castable refractory of the present invention is remarkably excellent in slag infiltration resistance and thermal shock resistance as compared with the conventional one, and has a durability of 1.5 times or more. On the other hand, by setting the amount of silica contained in the castable refractory to 0.3% by weight or less, the amount of low-melting minerals such as grenite and anorthite produced in the reaction phase with slag is reduced, and Since oversintering when spinel and silica coexist is prevented, structural spalling, cracking, and peeling can be suppressed.

[Brief description of drawings]

FIG. 1 is a perspective view of a curved plate-shaped test piece whose end face is fan-shaped cast using a castable refractory material according to an embodiment of the present invention.

FIG. 2 is a sectional view of an induction furnace used for an erosion test of the test piece of FIG.

FIG. 3 is a plan view of an induction furnace used for an erosion test of the test piece of FIG.

[Explanation of symbols]

 1 Test piece 2 Induction furnace 3 Erosion agent

Front page continuation (72) Inventor Noboru Nakamura No. 1 Minamitou, Ogakie-cho, Kariya city, Aichi Toshiba Ceramics Co., Ltd. Kariya factory (72) Inventor Keisuke Yamazaki No. 1 Minamitou, Ogakie-cho, Kariya city, Aichi Toshiba Ceramics Co., Ltd. Company Kariya Plant (72) Inventor Keisuke Sumitomo 3-2-1 Asano, Kokurakita-ku, Kitakyushu City, Fukuoka Prefecture Waki Fireproof Industry Co., Ltd. (72) Inventor Masaki Tange 3-Asano, Kokurakita-ku, Kitakyushu City, Fukuoka Prefecture No. 2 No. 1 in Wake Fireproof Industry Co., Ltd. (72) Inventor Hiroshi Shiroguchi, 3rd, Hikari, Kashima-machi, Kashima-gun, Kashima-gun, Ibaraki Sumitomo Metal Industries, Ltd. Kashima Works (72) Inventor, Koichi Ura Kashima-gun, Kashima-gun, Kashima-gun 3 in Hikari-machi, Kashima Steel Works, Sumitomo Metal Industries, Ltd. (72) Inventor, Kiyoe Hirayama, in Kashima-machi, Kashima-gun, Ibaraki Prefecture, Sumitomo Metal Industries, Ltd. Kashima Steel Works, Ltd.

Claims (2)

[Claims] 1. A spinel raw material containing 10 to 40% by weight and magnesia 5 to 20% by weight, and the balance consisting of alumina and a binder, and the particle size range of 0.05 to 2 mm of the spinel raw material is mainly composed of an electrofused spinel. Used and the amount of electrofused spinel added is 50% by weight or more of the total amount of spinel added, the particle size range of magnesia is 5 mm or less, and the remaining alumina partly contains 50% by weight or more of particles of 3 μm or less. A castable refractory material which comprises 2 to 8% by weight of ultrafine powder and 2 to 10% by weight of alumina cement as a binder. 2. The castable refractory material according to claim 1, wherein the content of silica in the castable refractory material is 0.3% by weight or less.