JPH09124360A - Basic refractory excellent in endurance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a basic refractory capable of preventing a so-called structural spalling generating on the contact of a magnesia brick with a slag. SOLUTION: This basic refractory is a magnesia-zirconia-based burnt basic refractory, of which characteristic is that the coarse grain part (aggregates) is an electrically fused magnesia, and the matrix part consists of a magnesia and a zirconia. The content of the zirconia in the matrix is desirably 3-10wt.% based on the total amount. The method for producing the refractory is to blend 30-80wt.% electrically fused magnesia having 1-5mm particle diameter as aggregates and the rest of a material obtained by blending the electrically fused magnesia having <1mm particle size and 3-10wt.% zirconia having <=10μm particle diameter based on the total amount as a matrix material, mixing both of them, form and sinter.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to, for example, a vacuum degassing device for molten steel, a ladle, a converter, a hot metal pretreatment device, a hot metal ladle,
The present invention relates to a basic refractory used as an lining refractory for these molten metal containers which are in contact with a basic slag containing FeO and / or a low basicity slag at a high temperature in an iron smelting reduction furnace or the like.

[0002]

2. Description of the Related Art In recent years, magnesia (Mg) has been used as a refractory lining for molten metal containers used in steel manufacturing processes.
Basic refractory materials such as O) have come to be used in many cases, the life for them has been extended, and the cost of steel production has been greatly reduced.

In the early days when many basic refractories were used, magnesia bricks were often used, but various improvements were made to improve their durability. For example, the durability of the basic refractory was further improved by using high-purity seawater magnesia as the raw material for magnesia or using highly crystallized high-purity electrofused magnesia as the raw material.

Furthermore, a refractory made of magnesia and zirconia and a small amount of forsterite produced by melting magnesia and zircon has been developed (see, for example, Japanese Patent Laid-Open No. Hei 3).
No. 232761). This refractory suppresses melting loss by making the liquid phase generated by the reaction of slag and magnesia infiltrated into the refractory highly viscous with zirconia.

In addition to this refractory material, Cr produces a small amount of liquid phase when it reacts with slag and has a high viscosity in the liquid phase.
Maguro bricks containing ₂ O ₃ have been developed and have made remarkable progress in corrosion resistance. However, the magro brick has a problem of hexavalent Cr when it is discarded, and its use may be limited.

[0006]

However, magnesia bricks are easily dissolved when they come into contact with slag having a low basicity or a large amount of FeO, and further, the slag infiltrates the grain boundaries of the magnesia bricks in the vicinity of the operating surface, and the continuous There is a phenomenon of so-called structural spalling, in which cracks are generated when the temperature changes due to the difference in the physical properties of the slag infiltration layer and the base material brick, resulting in peeling and wear.

A refractory material composed of magnesia, zirconia and a small amount of forsterite is presumed to be effective in improving structural spalling property, but forsterite having a relatively low melting point forms a liquid phase when mixed with slag. It is easy and the corrosion resistance is not sufficient.

Also, by melting magnesia and zirconia,
When cooled, zirconia precipitates at the grain boundaries of magnesia and reduces the primary crystals of magnesia, so magnesia particles are easily dissolved in slag. FIG. 1 shows that when magnesia and zirconia are mixed, melted, and cooled, the particle size of the original magnesia becomes smaller. Therefore, the effect of adding zirconia is not sufficiently exerted. Furthermore, if zirconia is added too much, the liquid phase increases and the durability decreases.

In order to solve the above problems and develop a basic refractory having high durability, as a raw material that can be industrially used, magnesia having a high melting point and excellent corrosion resistance is used as a main raw material, and corrosion resistance to slag is reduced. Instead, it is necessary to suppress structural spalling, which is a problem of magnesia bricks.

Structural spalling is a change in structure due to slag infiltration, specifically, densification of the structure, a liquid phase formed by the reaction between slag and magnesia, or fine particles of magnesia accompanying liquid phase formation. The cause is continuous void formation due to grain growth due to coalescence.

Therefore, the problems to be solved are to suppress the infiltration of slag into magnesia bricks, reduce the amount of liquid phase generated by the reaction of magnesia and slag in the slag infiltration part, and increase the viscosity. The purpose is to suppress the generation of continuous voids. At the same time, it is necessary to crystallize the magnesia itself in order to improve its corrosion resistance to slag.

[0012]

[Means for Solving the Problems] The inventors of the present invention have made extensive studies in order to solve the above-mentioned problems, and have made the following inventions. (1) The first invention provides a magnesia-zirconia-based fired basic refractory, characterized in that the coarse-grain portion (aggregate) is electro-melted magnesia, and the matrix portion is composed of magnesia and zirconia. .

(2) As a second invention, in the first invention, the content of zirconia in the matrix portion is 3 to 10 wt% with respect to the total amount, and a magnesia-zirconia-based calcined basic refractory material is provided. I will provide a. .

(3) In a third aspect based on the first aspect, the coarse grain portion is 30 to 80 wt%, the matrix portion is the rest, and the content of zirconia in the matrix portion is based on the total amount. A magnesia-zirconia-based calcined basic refractory is provided in an amount of 3 to 10 wt%.

(4) In the fourth invention, 30-80 wt% of electro-melting magnesia having a particle diameter of 1-5 mm is mixed as an aggregate, and the balance is electro-melting magnesia having a particle diameter of less than 1 mm and a particle diameter of 10 μm.
A method for producing a magnesia-zirconia-based fired basic refractory, characterized in that a mixture of 3 to 10 wt% of zirconia of m or less is used as a matrix material, and both are mixed, molded, and sintered to produce. is there.

That is, according to the present invention, magnesia produced by mixing high-purity electro-melted magnesia as a coarse grain part (aggregate) and high-purity magnesia and high-purity zirconia as a matrix, mixing, molding and firing. A zirconia-based fired basic refractory. The amount of zirconia added is 3 to 10 wt.
% Is desirable.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, high-purity electro-melted magnesia having a particle size of 1 mm or more as a coarse grain part (aggregate) and high-purity magnesia having a particle size of less than 1 mm and high-purity zirconia as a matrix material are mixed and blended. It is a magnesia-zirconia-based fired refractory produced by mixing, molding, and firing the above.

The refractory material produced by this above process is
The structure is such that a magnesia-particulate aggregate part is surrounded by a magnesia-zirconia matrix part. Therefore,
When it comes into contact with slag, zirconia that increases the viscosity of the liquid phase generated by the reaction of the matrix portion, which is the infiltration route, with the slag is added, so slag infiltration can be suppressed. Further, the diffusion rate of magnesium ions in the liquid phase is also slowed down, so that melting loss is reduced.

If zirconia is added too much, the amount of liquid phase increases and the melting loss becomes remarkable. However, the amount of zirconia added in the whole brick can be reduced by localizing it in the matrix which becomes the slag infiltration route. Furthermore, by making the aggregate (coarse-grained portion) into fused-grain magnesia with large-sized primary crystals, it becomes difficult to dissolve in slag, the liquid phase generation rate during reaction with slag is reduced, and grain growth is also suppressed. it can.

Electrofused magnesia which is an aggregate (coarse-grained portion) having a particle size of 1 mm or more and 5 mm or less is 30 wt% or more and 80 wt% or less.
Therefore, the balance is preferably a mixture of magnesia and zirconia having a particle size of less than 1 mm. This is because if the magnesia of the coarse-grained portion is less than 30 wt%, the corrosion resistance is poor, and if it exceeds 80 wt%, the matrix portion is reduced and the slag is easily infiltrated. The reason why coarse particles having a particle size of 1 mm or more and 5 mm or less are blended is to densify the brick so that the open pores serving as the infiltration route of the slag fall within a certain range.

When zirconia is localized in the matrix portion, the proper range of the added amount of zirconia is 3 to 10 wt.
%. Within this range, structural spalling does not occur and corrosion resistance against slag is good. If it is less than 3 wt%, the viscosity of the liquid phase is low and slag infiltration cannot be suppressed. Also, 10 wt
If it exceeds%, the amount of liquid phase increases and melting loss becomes remarkable, so the above range is made.

[0022]

[Examples] Electrofused magnesia having a particle size of 1 to 3 mm is used as an aggregate, and a mixture of electrofused magnesia having a particle size of less than 1 mm and zirconia having a particle size of 1 μm or less is used as a matrix material. To produce a magnesia-zirconia refractory. 40 of fused magnesia as a coarse grain part
60 wt% of a matrix material composed of electro-melted magnesia and zirconia was blended.

The amount of zirconia added is 3, 5 with respect to the whole,
What was made into 10 wt% was made into Examples 1-3, and 0, 1, 2
What was made into wt% was made into Comparative Examples 2-4, and each was mixed,
After forming, it was baked in a tunnel kiln at 1800 ° C. for 20 hours (oxidizing atmosphere).

Further, as Comparative Examples 5 to 10, raw materials produced by electromelting seawater magnesia and zirconia were crushed to obtain 40% by weight of coarse particles (1 to 3 mm) and fine particles (1 mm or less).
60 wt% was compounded, mixed, molded, and fired under the above conditions to produce a refractory material. The amount of zirconia added is 1, 2,
It was set to 3, 5, 10, 50 wt%.

Furthermore, a commercially available magnesia brick made from seawater magnesia was used as Comparative Example 1. With respect to the above Examples and Comparative Examples, the corrosion resistance and the structure spalling resistance were evaluated by the rotating drum test. The evaluation conditions are shown below,
An accelerated test was conducted under conditions severer than expected operations.

Evaluation conditions Method: Rotating drum test Shape of sample: Trapezoidal cross section having a base of 63.4 mm, an upper side of 40 mm, and a height of 40 mm, a length of 160 mm, and several samples were arranged on the inner wall of the rotating drum. Temperature: 1850 ° C. ( propane heated by gas) time: 5-9 hours (slag replaced every 30 minutes, 1 kg / dose) slag _{composition: CaO / SiO 2 = 1.2,} FeO = 9.0wt% attrition rate: infiltration layer boundary or working surface Evaluated by the wear rate from the position where continuous holes (or cracks) were formed parallel to

The above composition and evaluation results are shown in Table 1 and FIG. Comparative Examples 1 to 4 cannot be put to practical use because structural spalling occurs. Particularly, in Comparative Example 1 (magnesia brick made from seawater magnesia), slag infiltration was remarkable, a considerably thick porous reaction layer was formed on the operating surface, and continuous pores were formed near the brick side boundary part. Such continuous holes are shown in FIG.

In Comparative Examples 5 to 10, no remarkable continuous pores due to slag infiltration were generated, but a porous reaction layer having a certain thickness was formed in the vicinity of the working surface, so that there was a large amount of erosion loss. Inferior. Such holes are shown in FIG. In such a case, melting loss is large.

[0029]

[Table 1]

[0030]

As described above, the basic refractory material of the present invention is
High-purity electro-fused magnesia is blended as a coarse grain part (aggregate),
It is a magnesia-zirconia-based fired basic refractory produced by mixing high-purity magnesia and high-purity zirconia as a matrix, mixing, molding and firing. This basic refractory is a basic refractory having improved structure spalling resistance of magnesia and improved corrosion resistance as compared with conventional magnesia refractories. Therefore, for example, in a vacuum degassing device for molten steel, a ladle, a converter, a hot metal pretreatment device, a hot metal ladle, an iron smelting reduction furnace, etc., contact with basic slag and / or low basicity slag containing FeO at high temperature It can be used as a refractory lining for these molten metal containers.

[Brief description of the drawings]

FIG. 1 is a drawing-substituting photograph showing a change (smaller diameter) of magnesia crystal grains when magnesia and zirconia are mixed and melted.

FIG. 2 is a diagram comparing the effects of adding zirconia on the wear rate in a rotating drum test for Examples and Comparative Examples of a magnesia-zirconia system.

FIG. 3 is a drawing-substituting photograph showing a slag infiltration layer of Comparative Example 1 (magnesia brick made from seawater MgO) and a brick structure, and showing grain growth of magnesia by slag infiltration.

FIG. 4 is a comparative example 1, 2, 8, 1 in a rotary drum test.
It is a drawing substitute photograph which shows the melting damage state of the brick of 0 and this invention example (Example 2).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Eiji Kawamoto 19-1 Asahoshi-cho, Seto City, Aichi Prefecture Rainbow Shin Seto (72) Inventor Kuni Torii ▲ 1 ▼ 1-17 Hachimandai, Seto City, Aichi Prefecture

Claims (4)

[Claims] 1. A magnesia-zirconia-based calcined basic refractory material, wherein the coarse-grain portion (aggregate) is electro-melted magnesia, and the matrix portion is composed of magnesia and zirconia. 2. A magnesia-zirconia-based calcined basic refractory material, wherein the content of zirconia in the matrix portion is 3 to 10 wt% with respect to the total amount. 3. The coarse particle portion is 30 to 80 wt%,
A magnesia-zirconia-based calcined basic refractory, characterized in that the matrix portion is the balance and the content of zirconia in the matrix portion is 3 to 10 wt% with respect to the total amount. 4. An electrofused magnesia having a particle size of 1 to 5 mm is mixed as an aggregate in an amount of 30 to 80% by weight, and the rest is a particle size of 1 mm.
Less than less than 3 to 10 wt% of electro-melted magnesia and zirconia having a particle size of 10 μm as a matrix material are mixed, molded and sintered to produce a magnesia-zirconia-based firing material. Basic refractory manufacturing method.