JPH0725669A - Castable refractory for lining of sintered-metal container - Google Patents

Abstract

PURPOSE:To obtain a castable refractory for lining a sintered-metal container having excellent durability and capable of mildly controlling the volume expansion associated with a secondary spinel formation by the heat reaction of a compounded raw material, preventing a pore formation in a texture and a strength loss, improving structural spalling resistance and abrasion resistance and enhancing high corrosion resistance which is characteristic of a magnesia raw material. CONSTITUTION:This is a refractory raw material consisting of 4-25wt.% of magnesia material which is finer than 150 mesh, 0.5-5wt.% of silica material having <=5mum of particle diameter and the remaining part of alumina material, alumina cement and an optional refractory material for imparting required properties. 100wt.% of the refractory raw material contains 3-25wt.% of MgO and 0.5-6wt.% of SiO3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amorphous refractory for lining a molten metal container, which is excellent in durability and has improved volume stability and strength in an intermediate temperature range (for example, around 1000 ° C.). It is intended to provide an amorphous refractory for lining a molten metal container.

[0002]

2. Description of the Related Art As an amorphous refractory for forming the lining of a molten metal container for containing ladle or other molten steel, vacuum degassing in recent years has been used in place of conventional waxy stone, silica stone, and zircon. With the spread of technologies such as continuous casting and ladle refining, amorphous refractory materials such as alumina and spinel have been adopted in order to quickly respond to the severe processing conditions.

That is, as a technique recently announced as such a technique, there is JP-A-5-97526, in which a magnesia-based raw material having a particle diameter of 0.1 mm or less is 3 to 10 wt% and an alumina cement is 3-1.
It has been proposed that the MgO content be in the range of 3 to 10 wt% with 0 wt% and the remainder being 100 wt% of a refractory raw material composed of an alumina-based raw material.

[0004]

It can be said that the corrosion resistance and the slag permeation resistance are improved by the method disclosed in Japanese Patent Laid-Open No. 5-97526 as compared with the conventional method as described above. Volume expansion due to the formation of secondary spinel due to the reaction of the system raw material is unavoidable, and the structure expands due to the porous structure and the decrease in strength due to this volume expansion, and stable improvement in durability cannot be demanded.

Further, in such a refractory raw material, the fluidity in a kneading state with water and the behavior during heating and baking after lining change in various ways, and strength characteristics, corrosion resistance and corrosion resistance are appropriately utilized by utilizing such characteristics. It is not easy to effectively satisfy any of the slag properties. That is, the lining lining layer formed integrally on the entire inner surface of the container is more susceptible to these effects than the case of being formed as individual blocks, so that it is possible to obtain reasonably preferable results for individual characteristics. However, it is not always possible to obtain a practically preferable lining.

[0006]

The present invention has been studied to solve the above-mentioned problems in the prior art, and the combination of materials for obtaining a refractory lining for molten metal containers as described above and Corrosion resistance and slag permeation resistance are improved by appropriately selecting the particle size and blending amount to improve durability and fluidity in the kneaded material for forming the lining, and when firing the lining formed integrally in the container. It has succeeded in obtaining an amorphous refractory material which is excellent in terms of workability and strength by appropriately controlling the behavior in the above, and is as follows.

(1) 4 to 25 wt% magnesia-based raw material of 150 mesh or less and silica-based raw material of particle size 5 μm or less.
5 to 5 wt% and the balance is an alumina-based raw material, a refractory raw material composed of alumina cement and a refractory material for imparting properties as required, and the MgO content is 3 to 25 wt% in 100 wt% of the refractory raw material. And the SiO ₂ content is 0.
An amorphous refractory for lining a molten metal container, characterized by being 5 to 6 wt%.

(2) The amorphous refractory for lining a molten metal container according to the item (1), wherein the ratio of the MgO content to the SiO ₂ content is 3 to 12.

[0009]

[Action]

Magnesia raw material: 150 mesh or less. The magnesia raw material tends to generate a secondary spinel due to its small particle size, and when it exceeds 150 mesh, the secondary spinel becomes difficult to generate as the particle size increases, and it becomes difficult to stabilize the volume by expansion. . Also, due to the difference in expansion / contraction amount due to heating and cooling of the magnesia-based raw material and the alumina raw material, voids are likely to be created in the grain boundaries, and on the contrary, the structure becomes porous and the strength decreases, and the structure spalling resistance and wear resistance are increased. Resistance and corrosion resistance are reduced. Effectively solving these relationships by setting the mesh size to 150 mesh or less.

The addition amount of the magnesia raw material as described above is 4
If the addition amount is less than 4 wt%, the effect of high corrosion resistance, which is a characteristic of the magnesia-based raw material, cannot be sufficiently exerted, and if it exceeds 25 wt%, the expansion relaxation method described later is used. However, it is not preferable because it is difficult to alleviate and adjust the volume expansion associated with the formation of the secondary spinel, and conversely the heat resistance and corrosion resistance are reduced.

[0011] Further, the amorphous refractory has a characteristic that its fluidity is also important because it is added and kneaded with water and poured into it, and the particle size composition is such that the addition amount of particles having a particle size of 150 µ or less is 25 to 35 wt%. If the content is less than 25 wt%, good fluidity cannot be obtained, and if it exceeds 35 wt%, the fluidity is good but the kneading water amount increases and the strength decreases. Under these conditions, if the added amount of magnesia raw material with a particle size of 150 mesh or less exceeds 25 wt%, it is necessary to adjust the alumina-based raw material with a particle size of 150 μ or less, alumina cement, and secondary spinel formation necessary for secondary spinel production. It becomes difficult to adjust the required addition of the silica-based raw material of 5 μm or less. That is, these adjustment relationships are made appropriate by setting it to 25 wt% or less.

Silica-based raw material: 5 μm or less. As the silica-based raw material, it is preferable to employ the vaporizable silica described later in the present invention. Since this material has a small particle size and has a spherical shape, it promotes fluidization and improves filling property in this type of amorphous refractory. It is effective for curing or improving the dry strength, and those having a thickness of 5 μm or less are effective for such characteristics.

The amount of the silica-based material added is 0.5 to 5% by weight.
However, if it is less than 0.5 wt%, it is insufficient to make up for the drawbacks of secondary spinel formation. On the other hand, if it exceeds 5 wt%, the heat resistance is inferior because it has a large effect on the heat resistance of refractory materials. Sex decreases. For these reasons, the amount of the silica-based raw material having a particle size of 5 μm or less is set in the range of 0.5 to 5 wt%.

In the case of refractory materials such as amorphous refractory materials, the silica-based raw material having a particle size of 5 μm or less is inferior in heat resistance, has a large shrinkage property due to heating, and easily self-sinters, so that the refractory structure is In order to achieve the above-mentioned fluidization promoting purpose, etc., it is generally sufficient to use 1 wt% or less because it promotes oversintering of the silica raw material. In order to effectively utilize the property that the shrinkage property is large, the grain size of 5μ or less against the tissue porous formation and the strength decrease at the time of the secondary spinel formation accompanying the heating of the magnesia-based raw material and the alumina-based raw material having the particle size of 150 mesh or less. The self-sintering property and shrinkage property of the silica-based raw material are used. That is, the expandability at the time of forming the secondary spinel is compensated by the shrinkage of the silica-based raw material, and the structure porosity and the decrease in strength are compensated by the self-sintering property.

The remaining composition other than the above is composed of an alumina raw material, an alumina cement as a coagulant, and a refractory material for imparting properties as required. The alumina raw material has a particle size of 40 mm or less, preferably 8 mm. The following may be appropriately adopted, and silicon carbide, chromium oxide, and other materials are appropriately adopted as the refractory material for imparting the required characteristics. As the alumina cement as a coagulant, sodium silicate, colloidal silica, amine silicate, alumina sol, sodium phosphate, aluminum phosphate and the like can be appropriately used in combination.

The magnesia-based raw materials used in the present invention are seawater magnesia clinker, electrofused magnesia clinker, magnesium hydroxide, magnesium carbonate and naturally-occurring magnesite. The magnesite produced in the above is inferior in the digestion resistance due to the hydration reaction and is not always preferable.

Further, as the silica-based raw material used in the present invention, dust collecting powder obtained by collecting dust generated during production of metallic silicon or ferrosilicon is preferable, and generally silica fume or vaporizable silica is used. It has a small particle size and a spherical shape.

In the refractory raw material of 100 wt% adjusted as described above, the MgO content of the present invention is 3 to 25 wt%, and the SiO ₂ content is 0.5 to 6 wt%. If the MgO content is less than 3%, it is observed that either the wear depth or the erosion depth tends to be large during practical use, while if the MgO content exceeds 25 wt%, the linear change rate after high temperature firing There may be an unfavorable tendency such as a decrease in If the SiO ₂ content is less than 0.5 wt%, the bending strength and the like deteriorate, while if it exceeds 6 wt%, the linear change rate during high temperature firing may decrease.

In the present invention, the value of the ratio of MgO content to SiO ₂ content is set to 3 to 12 to obtain a particle size of 150.
This is preferable because the magnesia-based raw material having a mesh size or less and the silica-based raw material having a particle size of 5 μm or less can be sufficiently exhibited. That is, when the MgO content / SiO ₂ content ratio in the refractory raw material of 100 wt% is less than 3, the drawbacks such as low heat resistance and shrinkage of the silica-based raw material having a particle size of 5 μ or less tend to be greater. And if it exceeds 12, the particle size is 15
Expansivity due to secondary spinel formation due to heating reaction of 0 mesh or less magnesia raw material and alumina raw material
It becomes difficult to suppress tissue porosity and strength reduction. More preferable range of MgO content / SiO ₂ content is 4 to
Eleven.

[0020]

EXAMPLES Specific examples of the present invention will be described. First, the chemical composition of the refractory raw material adopted by the present inventors is as shown in Table 1 below.

[0021]

[Table 1]

However, the examples according to the present invention using the refractory raw materials and other raw materials according to the above Table 1 are shown in the following Tables 2 to 5.
Further, comparative examples for the examples of the present invention are as shown in Tables 6 and 7 described later.

[0023]

[Table 2]

[0024]

[Table 3]

[0025]

[Table 4]

[0026]

[Table 5]

[0027]

[Table 6]

[0028]

[Table 7]

In Table 2 to Table 7 as described above, 1
As a test method for firing at 000 ° C. or 1500 ° C., the refractory raw materials are mixed in the same amount of water, vibration-cast into a mold, and dried at 110 ° C. for 24 hours. At 1000 ° x 3 hours each, 15
Each property was measured after firing at 00 ° C. for 3 hours. Bending strength: According to JIS-R2553 Line change rate: According to JIS-R2554

As a method for evaluating the corrosion resistance, molten steel ladle slag and iron were used and eroded in a high frequency induction furnace at 1700 ° C. for 3 hours, and then the erosion depth was measured.

As a method of evaluating wear resistance, the wear depth of the sample was measured by the sandblast method under the following conditions. -The sample is 160 x 140 baked at 1000 ° C for 3 hours.
A 40 mm shape was used.・ Original valve pressure: 3.6kg / cm ²・ Distance: 185mm ・ Radiation angle: 90 ° ・ Injection material: Particle size 28
Korangum of mesh ・ Loose diameter: φ5mm ・ Injection time: 30 seconds

[0032]

According to the present invention as described above, the volume expansion associated with the secondary spinel formation due to the heating reaction of the compounded raw materials is appropriately relaxed and controlled, and the porous structure and strength reduction are effectively prevented, and By improving the structural spalling property and wear resistance, the high corrosion resistance characteristic of magnesia-based raw materials can be fully exerted, and an amorphous refractory for lining a molten metal container with excellent durability can be accurately provided. Therefore, the invention is industrially effective.

Claims (2)

[Claims] 1. A magnesia-based raw material having a size of 150 mesh or less 4 to 25 wt% and a silica-based raw material having a particle size of 5 μm or less 0.5 to 5
wt% and the balance is a refractory raw material consisting of an alumina-based raw material, an alumina cement and a refractory material for imparting properties as required, and M at 100 wt% of the refractory raw material
gO content is 3-25 wt%, SiO ₂ content is 0.5-6
An amorphous refractory for lining a molten metal container, characterized by being wt%. 2. The amorphous refractory for lining a molten metal container according to claim 1, wherein the value of the ratio of the MgO content to the SiO ₂ content is 3 to 12.