JPH0323275A - Monolithic refractory for casting - Google Patents

Abstract

PURPOSE:To obtain the title refractory having superior resistance to corrosion, permeation of slag and spalling by adding a specified hardening agent to a mixture consisting of prescribed amts. of high purity aluminous starting material, spinel clinker, magnesia clinker and amorphous silica. CONSTITUTION:A mixture consisting of >=57wt.% high purity aluminous starting material such as mixture of sintered alumina clinker with calcined alumina, 10-30wt.% spinel clinker such as sintered spinel, 1-10wt.% magnesia clinker of <0.21mm grain size such as sintered magnesia and 0.2-3wt.% amorphous silica is prepd. and alumina cement as a hardening agent is added to the mixture by 0.5-<3wt.% of the amt. of the mixture. Activated magnesia may be added as the hardening agent by 0.2-5wt.%.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is a refractory material suitable for pouring monolithic refractories, particularly tin linings, dip pipes for DH and RH, base materials for tundishes, etc. relating to things.

[Conventional technology]

Conventionally, castable monolithic refractories have been made of silica, rosite, chamotte, and high alumina. Magnesia quality. Raw stone, zircon, etc. have been used.

In recent years, vacuum degassing and continuous casting have been introduced. With improvements in tin refining technology, high-grade steels are now being refined, and processing conditions are becoming increasingly harsh due to increases in molten steel temperature and longer residence times. However, it is no longer possible to meet the requirements in terms of corrosion resistance, spalling resistance, volume stability, etc.

For this reason, as a refractory that can be adapted to such severe processing conditions, Subinel monolithic refractories using Subinel Klinriki have been proposed in JP-A-60-60985 and JP-A-64- It is disclosed in JP-A No. 87577 and the like.

This Subinel monolithic refractory effectively utilizes the characteristics of spinel clinker, such as its low coefficient of thermal expansion and high resistance to slag immersion, and has excellent corrosion resistance, spalling resistance, and volume stability. , as well as cracks caused by thermal spalling and slag penetration. It is also excellent in suppressing peeling.

In particular, the one described in Japanese Patent Application Laid-Open No. 60-60985,
The expansibility that should be imparted to the refractory material is not due to Subinel expansion caused by the reaction of Kg○-^l,03, as seen in conventional basic materials, but is due to the expansion of the fine powder portion.
Refractories are made by utilizing the form of Ca0.6^R20s or the accompanying expansion caused by the reaction between alumina containing O~35% by weight and CaO in alumina cement containing 3~10% by weight at high temperatures. This is due to the fact that it has been given expandability.

However, there is a drawback that the amount of erosion becomes extremely large when operating conditions are severe.

Moreover, the one described in Japanese Patent Application Laid-Open No. 64-87577 is
Magnesia was added to achieve volumetric stability, but the infiltration of slag was large and the spalling resistance was poor, resulting in peeling. The drawback was that the metal holder was large.

[Problem to be solved by the invention]

In this way, the lining refractories described in the above publications have better corrosion resistance than conventional monolithic materials. Although improvements in spalling resistance and volumetric stability have made it possible to achieve high durability, there is a drawback that structural spalling due to slag infiltration is likely to occur, making it difficult to maintain performance during the middle of operation. Peeling and wear occur in the final stages, and improvements in stability are desired.

The problem to be solved in the present invention is to eliminate the drawbacks of such conventional refractory materials, and to combine the effects of improving corrosion resistance by using MgO Clin Power and Subinel Clin Power in combination with slag infiltration resistance and slag resistance. The objective is to improve polling performance without deteriorating it.

[Means to solve the problem]

The castable monolithic refractory of the present invention contains at least 57% by weight of high-purity alumina raw material and 1% by weight of subaru clinker.
0 to 30% by weight, 1 to 10% by weight of magnesia clinker with a particle size of less than 0.21 mm, and 0.2% of amorphous trade silica.
-3% by weight of alumina cement as a hardening agent, or 0.5% to less than 10% by weight, or 0.2 to 5% by weight of activated magnesia.

Further, in the above invention, one of the high purity alumina raw materials
It is also possible to replace ~20% by weight with magnesia clinker with a particle size of 0.21 mm or more.

The high purity alumina raw material used in the present invention specifically refers to sintered alumina, fused alumina or calcined alumina, and examples of the high purity alumina raw material include sintered spinel,
As the electrofused subinel and magnesia cleaner, those with less impurities such as sintered magnesia and electrofused magnesia can be used.

In the compound composition of the present invention, the usage ratio of alumina spinel-magnesia is determined by the corrosion resistance, slag infiltration resistance,
Determined from volumetric stability.

[Function j] The magnesia blended in the present invention has the function of imparting expandability through a subinelization reaction with alumina, improving corrosion resistance to iron oxide-containing slag, and suppressing slag infiltration. However, a range less than 1% by weight is not sufficient to impart expandability to the material, and a range greater than 10% by weight causes excessive expansion, resulting in tissue deterioration during use.

The particle size of the magnesia curing powder blended in an amount of 1 to 101% by weight needs to be less than 0.21+n in order to achieve corrosion resistance and to cause a uniform subinelization reaction.

The usage ratio of the spinel raw material is regulated by the corrosion resistance depending on the amount of amorphous silica blended. Conversely, if the amount of Subinel used exceeds 30% by weight, MgO-^l20
is+02 This shows a tendency for corrosion resistance to deteriorate due to an increase in the amount of low-melting substances produced. From this, the blending amount of Subinel is 10~
Although it is regulated to 30% by weight, there is no particular regulation regarding particle size.

The addition of mata/amorphous silica accelerates hardening and imparts strength development during the initial stage of drying from curing, further maintains the air permeability of the material at a low level, and can suppress the penetration of slag. .

If the amorphous silica is less than 0.2% by weight, strength development is poor;
Moreover, at 3% by weight or more, MgO-^1 2 0 3 S
The tendency for oversintering due to the formation of I02-based low melting substances increases,
Unfavorable because of poor spalling properties. Furthermore, the particle size of the amorphous silica is preferably one with a specific surface area of 20 to 500 m'/g.

The high-purity alumina raw material of the present invention is the above-mentioned magnesia. It is determined by regulating the usage ratio of Subinel and amorphous silica, which is at least 57% by weight.

Furthermore, corrosion resistance can be improved by replacing a part of the high-purity alumina raw material used in the present invention with magnesia clinker having a particle size of 0.21+m or more. However, if more than 20% by weight of magnesia clinker is used, the expansion will be too large and the spalling resistance will also deteriorate.

Therefore, its amount is defined in the range of 1 to 20% by weight.

The hardening agent blended in the present invention is alumina cement or activated magnesia. If the amount added is large, CaO-^R20y-Mg〇-SiO. Since this results in an increase in raw sxm of the low-melting system and a decrease in corrosion resistance, the outer weight of cement is less than 3% by weight, preferably 0.75% by weight or less as Cavil, or the outer weight of activated magnesia is 5% by weight. % or less.

In particular, in the case of activated magnesia, if the amount added is large^12
The amount of 0s-MgO is also limited because it induces tissue deterioration due to its high expandability due to the spinel formation reaction.

On the other hand, if the amount of cement is less than 0.5% by weight or the amount of activated magnesia is less than 0.2% by weight, it will take a long time to cure until the frame is removed after construction, and the strength will be poor, which is undesirable.

In addition, alkali condensed phosphate is used to improve the workability of refractories.
It is also possible to add a dispersant such as sodium polycarboxylate, a small amount of clay within a range that does not affect the material properties, and a small amount of metal to improve explosion resistance against short-term drying.

〔Example〕

Table 1 shows the results when the mixing ratio of high-purity alumina raw material and magnesia clinker fine powder in the refractory mixture in the present invention was changed, and when a part of the high-purity alumina material was 0.21%
The characteristics of aggregate when replaced with magnesia with a curing force of 1 mm or more are shown.

Remaining after heating a sample made by mixing fine powder of seawater magnesia clinker of less than 0.21 mm with a high-purity alumina raw material consisting of a mixture of sintered alumina talinker and calcined alumina whose particle size has been adjusted This figure shows the relationship between the expansion coefficient and apparent porosity, or the amount of erosion by the rotary erosion method and the amount of slag infiltration.

From the same table, the erosion amount and slag infiltration of high-purity alumina raw materials are approximately 1 to 10% for magnesia clinker less than 0.21 u.
It can be seen that good results are shown in the case of weight %.

Table 2 shows the relationship between the high purity alumina raw material whose particle size has been adjusted based on the results in Table 1 and magnesia of 0.21+em or more and the clinking force of -15% and the sintered spinel clinker amount ratio of less than 0.21n. Using a sample obtained by adding a specified amount of water to 5% by weight of fine seawater magnesia clinker powder, 1% by weight of amorphous silica, and 2% by weight of alumina cement as a hardening agent and curing at 20°C for 24 hours, rotation was performed. This figure shows the relationship between the amount of erosion and slag immersion ailt using the erosion method.

From Table 2, it can be seen that good erosion resistance is exhibited when the amount of spinel clinker blended in the refractory material mixture is within the range of 10 to 30% by weight.

Table 3 shows an investigation into the relationship between amorphous silica matrix, strength, and erosion resistance. 60% by weight of high-purity alumina raw material with adjusted particle size, 0.21+m or more magnesia cleaning power - 10%, Subinel cleaning strength - 25% by weight. 0.2
The results are shown when an amount of amorphous phosphor was added to a mixture of 5% seawater magnesia clinker fine powder of less than 1 u and 2% q% of alumina cent as a hardening agent.

A predetermined amount of water was added and cured at 20° C. for 24 hours to obtain a cured sample. The strength of this cured sample after drying at 110°C, the compressive strength after firing at 1500°C for 3 hours, and the relationship between the amount of erosion and the amount of slag infiltration were investigated using a rotary erosion method.

Test samples Nα21 to Nα24, which are examples of the present invention, have sufficient strength, do not have a tendency to oversinter after high-temperature sintering, and show good results in terms of the amount of erosion, amount of slag infiltration, and cracking. show.

Table 4 shows 74% by weight of high-purity alumina raw material whose particle size has been adjusted and 20% by weight of sintered Subinel clinker. A mixture in which 5% by weight of seawater magnesia clinker, 1% by weight of amorphous silica, and a part of the high-purity alumina raw material is replaced with magnesia clinker of 0.21a+m or more, using alumina cement or activated magnesia as a hardening agent, and other The relationship between the amount of application and the hardening time of the cast body after curing at 20°C, the strength after drying at 110°C, the rate of change in strength line after firing at 1500°C, the amount of slag erosion by rotary erosion test, the amount of slag infiltration, and the degree of cracking due to spalling. shows.

In addition, the cast body is made of 40×40 after adding the specified amount of water.
It was cast into a shape of x 15 Qmm, cured at 20°C for 48 hours, dried at 110°C for 24 hours, and burned at 1500°C for 3 hours, and then the quality was measured.

From the same table, test sample Nll shown as an example of the present invention
L29-34 are comparative examples of test samples $4Nc27.
It can be seen that, in comparison with No. 28 and Nα35-38, it has excellent properties in terms of workability, compressive strength after drying, and erosion resistance.

(See below in the margins of this page) [Effects of the Invention] The cast monolithic refractories of the present invention can provide the following effects.

(1) When using lJgo clinker and spinel clinker together, the use of amorphous silica curing agent was restricted, and spalling resistance was improved by preventing oversintering.

(2) While the conventional addition of MgO to alumina-based aggregate was effective in improving corrosion resistance, there were problems of structural deterioration and thick slag infiltration due to excessive Svinel expansion. Refractories are less susceptible to the above disadvantages by limiting the amount of alumina cement mixed and specifying the amount of magnesia clinker particles.

(3) Corrosion resistance due to the addition of Mg○ is significantly improved by the above (1) and (2).

(4) Shows appropriate hardening and strength during construction.

Claims (2)

[Claims] 1. At least 57% by weight of high-purity alumina raw material, 10-30% by weight of spinel clinker, and a particle size of 0.21%
1 to 10% by weight of magnesia clinker less than mm,
A mixture consisting of 0.2 to 3% by weight of amorphous silica,
External coating of alumina cement as a hardening agent of 0.5% to less than 3% by weight, or external coating of activated magnesia of 0.2 to 3%
A monolithic refractory for pouring containing 5% by weight. 2. At least 37% by weight of high-purity alumina raw material, 10-30% by weight of spinel clinker, and a particle size of 0.21%
1 to 20% by weight of magnesia clinker of mm or more,
1 to 1 magnesia clinker with a particle size of less than 0.21 mm
Alumina cement is applied as a hardening agent to a mixture consisting of 0% by weight of amorphous silica and 0.2 to 3% by weight of amorphous silica.
．． A castable monolithic refractory containing 5% by weight or more and less than 3% by weight, or 0.2 to 5% by weight of activated magnesia.