JPH0421575A - Monolithic refractory for hot metal - Google Patents

Abstract

PURPOSE:To improve spalling resistance, by blending an aggregate having a specific amount of Al2O3 with MgO fine powder and a carbon raw material. CONSTITUTION:One or plural raw materials such as corundum, mullite, chamotte, cyanite or andalusite consisting essentially of Al2O3 and SiO2 ranging from a raw material having about 98wt.% Al2O3 content to a raw material having about 50wt.% Al2O3 are used alone or mixed and used and prepared into an aggregate having 50-90wt.% Al2O3 content based on total amounts of aggregate. The aggregate is blended with 0.5-15wt.% based on total amounts of aggregate of MgO fine powder having <=0.15mm particle diameter and <=5wt.% based on total amounts of aggregate of a carbon raw material such as graphite or pitch to give a monolithic refractory for hot metal having improved spalling resistance.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a monolithic refractory for hot metal, and more specifically to a monolithic refractory for hot metal containing fine powder and aggregate mainly composed of alumina and silica. Regarding.

[Prior Art] For example, monolithic refractories for hot metal, such as those used to protect gas blowing lances in ironmaking, must first have high slag resistance and no structural deterioration due to heating and cooling. is required. The slag resistance almost depends on the alumina content of the monolithic refractory, and the higher the alumina content, the better the slag resistance. Therefore, conventionally,
For example, a monolithic refractory for hot metal with a high alumina content of 45 to 90% has been used as the above-mentioned monolithic refractory for hot metal for lance protection. However, on the other hand, the problem is that structural deterioration due to heating and cooling progresses more easily as the alumina content increases.
With increasing alumina content, expansion due to temperature change,
This is thought to be due to the expansion of cracks due to increased shrinkage and the increased shear stress caused by the softening of materials with high alumina content at high temperatures. When used in products, various improvements have been made to prevent tissue deterioration.

For example, from the viewpoint of improving the joint morphology of the Mar-IJ socks, efforts have been made to add ultrafine silica powder to make the cement bond a cohesive bond, or to add metal fibers to delay tissue destruction.

In addition, in order to suppress shrinkage due to baking during heating,
Kyanite and anglesite, which are high alumina raw materials that exhibit residual expandability after heating, are added to the raw material in advance to reduce cracking during use of the refractory material.

In particular, for monolithic refractories for hot metal used to protect lances,
There is also the problem of kudzu, which causes structural spalls due to slag penetrating into the refractory. Therefore, spinel raw materials are added to suppress slag penetration and prevent structural spalls. Furthermore, by blending silicon carbide, graphite, pitch, etc., which have non-wetting properties and high thermal conductivity, in addition to preventing structural spalls due to slag penetration, we have improved heat-resistant spalling properties. is also used.

[Problems to be Solved by the Invention] In the present invention, for example, in a monolithic refractory for hot metal, structure deterioration due to heating and cooling is improved while maintaining good slag resistance. It also prevents structural spalling due to slag penetration into the refractory, and further improves thermal spalling properties.

[Means to solve the problem]

In the monolithic refractory for hot metal according to the present invention, Al 20. Corundum has a mineral structure of
Alto3 SiO□-based minerals such as mullite, chamotte, kyanite, and anglesite are used. Furthermore, Mg0A/220. Minerals such as spinel can also be used. These raw materials may be used alone or in combination to form an aggregate mainly composed of alumina and silica, or alumina, perilla, and magnesia. The amount of alumina in the entire aggregate is 50~
The blending ratio is selected to be within the range of 90 wt%.

By using such a high alumina content, the refractory has good slag resistance. In addition, in order to solve the problem of structural deterioration due to heating and cooling, which is a drawback of high alumina refractories, we added magnesia powder with a particle size of 0.15 mm or less to the fine powder, making it possible to reduce the total .5-15
It was decided to mix wt%. This fine powder of magnesia is reacted with aggregate components mainly containing alumina and silica to generate a structure with a composition similar to spinel or coplite, imparting softening properties and preventing structure deterioration. .

Furthermore, in order to increase the effect of preventing slag penetration, carbon raw material was added to the refractory in an amount of 5 wt % or less, if necessary. That is, the present invention is a monolithic refractory for hot metal having fine powder and aggregate mainly composed of alumina and silica, wherein the amount of alumina contained in the aggregate is 50 to 90 wt% of the total aggregate. Within the range, 0 for fine powder
．． It is characterized by a structure in which magnesia powder having a particle size of 15 mm or less is blended in an amount of 0.5 to 15 wt% of the entire refractory.

Further, another configuration of the present invention is characterized in that a carbon raw material is further blended in 5 wt % or less of the entire refractory to the fine powder of the amorphous refractory for hot metal as described above.

[For production]

When the magnesia powder blended into the fine powder in this invention is used in a hot metal treatment (desiliconization) lance, it reacts with alumina and silica, which are the main components of aggregate, at the temperature under that condition, resulting in spinel and cope. A structure having a light-like composition (hereinafter simply referred to as spinel and coplite) is produced. This coplite has a relatively low melting point and has the effect of imparting softening properties to refractories. As a result, distortion caused by expansion and contraction due to heating and cooling during use is absorbed, and tissue deterioration can be prevented. Also, the next reaction that produces spinel ■ MgO + AAzO3 → M g O-A l z Oy-
In case (2), since volume expansion is involved, shrinkage of the structure due to firing is suppressed, resulting in a refractory with a stable firing line change rate. Therefore, a refractory is formed that prevents cracks from occurring due to shrinkage and has excellent spalling resistance.

In addition, in the present invention, the matrix and aggregate are firmly bonded through the appropriate amount of spinel and coplite due to the reaction between magnesia powder and aggregate, which prevents slag penetration. Increased durability. In addition, the presence of magnesia in the matrix allows Ca
The resistance to slag mainly composed of O, F e 203 increases.

The magnesia powder used in the present invention exhibits remarkable effects when the particle size is 0.15 mm or less. If magnesia powder has a particle size coarser than this, the reactivity with alumina or silica in the aggregate will be significantly reduced. If a large amount of unreacted magnesia exists, the spall resistance will be adversely affected because magnesia is highly expansible. Also, the blending ratio is 0.0% of the total refractory raw materials.
5 to 15 wt% is suitable. If it is less than 0.5 wt%, the desired effect cannot be expected, and if it exceeds 15 wt%, residual magnesia will increase and the spall resistance will also decrease. At the same time, a large amount of coplite, which is a substance with a lower melting point than alumina or silica, is produced, which is undesirable. It is more preferable that the content of this magnesia powder is 1 to 10 wt%.

The aggregate component of the monolithic refractory according to the present invention includes mineral compositions such as alumina, alumina-silica, alumina-magnesia, and alumina-silica-magnesia, such as corundum, mullite, Raw materials with an alumina content of 198 wt% such as chamotte and spinel and raw materials with an alumina content of 50 wt% are used. These aggregate raw materials are selected depending on the required corrosion resistance, and are used alone or in combination. In the present invention, the amount of alumina contained in the aggregate is 50 to 90 wt% of the total aggregate. If the alumina content is less than 50 wt%, slag resistance deteriorates, and low melting point substances such as coplite are likely to be produced, resulting in decreased durability. On the other hand, when the alumina content exceeds 90 wt% of the total aggregate, structural spalls caused by the high expansibility of alumina cannot be suppressed even by adding magnesia powder, and spall resistance is not improved.

Furthermore, when spinel is used as an aggregate raw material for the monolithic refractory for hot metal of the present invention, it is preferable that spinel accounts for 20 wt% or less of the total aggregate. Since spinel has a magnesia component in its mineral composition, a large amount of spinel will result in the same negative effect as adding a large amount of magnesia powder, i.e., the formation of low melting point products such as coplite.
This results in an amount exceeding that desired to provide good softening properties.

In the monolithic refractory for hot metal of the present invention, the addition of carbon raw materials further improves the spall resistance and further improves the thermal spall resistance. This is because the carbon raw material has a non-wetting property that prevents slag penetration and high thermal conductivity. On the other hand, the addition of carbon raw materials has conventionally been a cause of deteriorating slag resistance. However, in the present invention, the slag resistance is improved by blending magnesia powder, so it is possible to eliminate the negative influence of the carbon raw material on the slag resistance. Moreover, it has a more remarkable effect in preventing slag penetration than before. That is, the magnesia powder used in the present invention and carbon undergo a reaction according to the following formula (2) to generate CO gas.

MgO+C→Mg+CO■ Since this CO gas is present on the working surface, it is highly effective in preventing slag penetration. As this carbon raw material, silicon carbide, graphite, pinch, etc. can all be used. In this invention, the amount of carbon raw material added is 5 wt% or less of the total refractory. Even when it exceeds 5 wt%, the effect of preventing slag penetration is sometimes large.

However, the structure deteriorates significantly due to oxidation of carbon, and is not effective in extending the overall life. Therefore, for example, as a refractory material for protecting a hot metal processing lance, it is appropriate that the amount of carbon raw material added is 5 wt% or less.

C Example 1] Alumina, mullite, chamotte and spinel were used as aggregate raw materials, and magnesia fine powder (particle size: 0.
15 mm or less), ultrafine alumina powder, ultrafine silica powder, alumina cement as a binder, and a dispersant to obtain a monolithic refractory. The blending ratios of these refractory raw materials are shown in Table 1 together with conventional products and comparative products.

In addition, the quality of each refractory, 1400°
The line change, spall resistance, and slag penetration after C firing were investigated, and these characteristic values are also listed in Table 1. The spall resistance was tested by repeating 10 times the process of rapidly heating the refractory at 1400°C and then rapidly cooling it in the atmosphere. As a result, those in which no cracks were formed were marked with ◎, those with minute cracks were marked with ○, those with small cracks were marked with △, and those with large cracks were marked with ×.

In addition, Fig. 1 shows the relationship between the amount of magnesia powder added and the residual linear change rate after firing at 1400°C, and Fig. 2 shows the relationship between the amount of magnesia powder added and slag permeability. .

Table 2 shows each characteristic value when the particle size of magnesia powder is changed with the same raw material composition, and the content of MgO and spinel after immersing the refractory in hot metal at 1400°C for 30 minutes by X-ray diffraction. It is expressed as an index of peak height. This second
From the table, it can be seen that in the product U of the present invention, MgO is reduced by reaction with the aggregate and more spinel is produced than in the comparative product using magnesia powder with a large particle size.

From the above results, it can be seen that the monolithic refractory according to the present invention has excellent spall resistance and slag resistance, and does not shrink after firing.

[Example 2] The characteristics of refractories obtained by adding a carbon raw material to each of a refractory raw material containing magnesia powder and a refractory raw material containing no magnesia powder were shown. The raw material composition and characteristic values are shown in Table 3. The results show that the product of the present invention containing carbon raw material is superior in both spall resistance and slag resistance.

〔Effect of the invention〕

The present invention provides a monolithic refractory for hot metal that is excellent for protecting hot metal processing lances, for example. The monolithic refractory for hot metal of the present invention contains magnesia fine powder, so when it is used as a protective material for a hot metal processing lance, it is heated and alumina and silica in the aggregate react with magnesia, forming a cope. Produces a refractory structure with a structure similar to that of light or spinel. The effects are as follows: Copelite has a relatively low melting point, so it imparts softening properties to the refractory, absorbs distortion caused by expansion and contraction due to heating and cooling, and prevents structural deterioration. Since the reaction involves volume expansion,
Shrinkage of the structure due to calcination is suppressed, improving spall resistance. iii) The bond between the matrix and aggregate becomes stronger, preventing slag penetration.

It is. In addition, the slag resistance is improved due to the blending effect of magnesia powder itself.The effect of adding carbon to the monolithic refractory for hot metal of the present invention is as follows:2. Due to the non-wetting property and high thermal conductivity of carbon, Slag penetration prevention and spalling resistance, especially thermal spalling prevention, are improved. In this case, the negative effects of carbon on slag resistance are eliminated in the present invention because magnesia imparts great slag resistance. It becomes possible, ho. CO gas is produced by the reaction between magnesia and carbon. This gas is present on the operating surface, further enhancing the slag prevention effect.

Table 2 Mixing raw materials for refractories (weight%) and characteristic values Table 3 Mixing raw materials for refractories (weight%) and characteristic values

[Brief explanation of the drawing]

Figures 1 and 2 are graphs for explaining the monolithic refractory for hot metal according to the present invention, and Figure 1 shows the relationship between the amount of magnesia powder added to the refractory and the rate of change in the residual line after firing. 2nd M is a graph showing the relationship between the amount of magnesia powder added to the refractory and the slag permeability. Applicant Harima Ceramic Co., Ltd.

Claims (2)

[Claims] 1. A monolithic refractory for hot metal containing fine powder and aggregate mainly composed of alumina and silica, wherein the amount of alumina contained in the aggregate is within the range of 50 to 90 wt% of the total aggregate, and fine powder A monolithic refractory for hot metal, characterized in that magnesia powder having a particle size of 0.15 mm or less is blended in an amount of 0.5 to 15 wt% of the total refractory. 2. A monolithic refractory for hot metal containing fine powder and aggregate mainly composed of alumina and silica, wherein the alumina contained in the aggregate is within the range of 50 to 90 wt% of the total amount of aggregate, and the fine powder Magnesia powder having a particle size of 0.15 mm or less is blended with 0.5 to 15 wt% of the total refractory, and carbon raw material is added to the above fine powder with a particle size of 5 wt% of the total refractory.
% or less of monolithic refractories for hot metal.