JP2003226570A - Magnesia-spinel brick - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the corrosion resistance of magnesia-spinel brick with rare earth oxide as refractories freed of chromium added when it is applied to the lining of a kiln for metal refining such as a steel secondary refining furnace. <P>SOLUTION: In the magnesia-spinel brick with rare earth oxide added, Al<SB>2</SB>O<SB>3</SB>is not contained in a matrix, or the content thereof is prescribed to ≤2 mass%. The magnesia-spinel brick with rare earth oxide added has a raw material composition consisting of a magnesia clinker, a rare earth oxide raw material, and a spinel clinker, and, as for the grain size composition of the spinel clinker used as the raw material, the ratio of the ones with a grain size of ≥1 mm is 3 to 30 mass%, and the ratio of the ones with a grain size of <1 mm is <3 mass%. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a magnesia-spinel brick to which a rare earth oxide has been added, which is used for lining a kiln for refining metals such as steel.

[0002]

2. Description of the Related Art In steel manufacturing processes, secondary refining processes such as AOD, RH, and ladle refining have become more and more important as steel products have become higher quality and stricter quality.

As a refractory lining for a secondary refining kiln,
Magnesia-Chrome brick (hereinafter referred to as magcro brick)
Are often used. But this brick
Cr _TwoO_ThreeThe content of the brick after use is 6
A small amount of chromium will be included and will be disposed of.
I have a problem.

Therefore, in recent years, so-called chromium-free bricks that replace magcro bricks have been studied. For example, magnesia-spinel bricks (hereinafter referred to as “magspinel bricks”) have a chromium-free composition by using a common spinel (MgAl ₂ O ₄ ) as the secondary spinel of magcro bricks, and have excellent durability similar to that of magcro bricks. It is a material aiming at the effect of the toughness, and is considered to be the mainstream of dechromized bricks in the future.

However, common spinels are particularly low-C.
Since the corrosion resistance to / S slag is inferior, the durability of the mag spinel bricks is often insufficient due to the preceding erosion of the matrix. Therefore, it has been considered to strengthen the brick matrix with a substance other than common spinel in an aggregate mainly composed of magnesia. For example, JP 2000
Japanese Patent Publication No. 128624 discloses a magnesia brick in which a rare earth oxide is added to a matrix portion of magnesia, and it is said that the magnesia brick has excellent corrosion resistance in a RH furnace as compared with conventional magcro bricks. It is presumed that this is because the rare earth oxide is mainly present in the matrix of the brick, and the corrosion resistance of the brick is improved by suppressing the penetration of slag.
However, this brick has a problem of large expansion and a little inferior spalling resistance.

As an example of using this rare earth oxide,
More resistant to spalling than magnesia for ment kilns
Excellent magnesia spinel (mag spinel) brick
An example of using a rare earth oxide in the matrix part of JP
It is disclosed in Japanese Laid-Open Patent Publication No. -116014. This is Al
_TwoO_ThreeContaining 30 to 90 mass% of MgO-Al_TwoO _Three
System spinel raw material 5 to 90 mass% and magnesia raw material 95 to
Refractory raw material consisting of 10% by mass, one or more kinds of
Rare earth oxides were added on the outside at 0.1 to 10 mass%
Therefore, the adhesiveness of cement coating is greatly improved,
As a result, the durability of the brick can be significantly increased.
It is said that.

However, this mag spinel brick is
It was found that sufficient corrosion resistance cannot be obtained when applied to a steel secondary refining furnace such as an H furnace.

[0008]

The problem to be solved by the present invention is to line a mag spinel brick containing a rare earth oxide as a dechromized refractory material in a kiln for metal refining such as a secondary refining furnace for steel. It is to improve the corrosion resistance when applied to.

[0009]

[Means for Solving the Problems] In the above cement kiln, the reason why the durability is inferior when a magspinel brick containing a rare earth oxide having excellent corrosion resistance is used in a secondary refining furnace for steel is estimated as follows, The present invention has been completed based on this.

That is, the present inventor has found that MgO and Al ₂
And O _3, a mixed powder of _Y 2 _{O 3} were prepared as representative of the rare earth oxide, when heated at 1700 ° C., melilite (melilite) was found experimentally to be detected a small amount as a mineral phase. The melting point of this melilite phase is 14
Since the temperature is around 00 ° C., it melts at a high temperature, which causes a significant decrease in corrosion resistance.

From this, Japanese Patent Laid-Open No. 6-116 mentioned above.
In the brick for cement kiln described in Japanese Patent No. 014, it was speculated that the spinel clinker and the rare earth oxide react with the heat received from the operating surface during firing or during use, and a melilite phase is formed around the spinel clinker. In the rotary kiln for cement, the brick is protected by the slag coating, and the formation of this melilite phase does not have a great influence, but when it is applied to the secondary refining furnace for steel, slag and molten steel are not applied to the surface of the brick. Because of the direct attack, it was considered that the formation of melilite phase in the matrix part had a great influence on the durability of the brick.

Therefore, as a result of various studies focusing on suppressing the formation of the melilite phase, when the matrix portion of the magspinel brick containing a rare earth oxide contains a very small amount of Al ₂ O ₃ component, the corrosion resistance is remarkably excellent. I understood it. The term "matrix part" here means a particle size of 1 m.
It is a structure composed of refractories of m or less.

Here, it can be seen that the corrosion resistance is highest when the matrix portion does not contain Al ₂ O ₃ . However,
Depending on the particle size and the amount of the spinel raw material used, Al ₂ O ₃ may be contained in the matrix portion as an inevitable component. Further, it may be necessary to add an Al ₂ O ₃ component in order to impart spalling resistance to the refractory material. Therefore, from a practical point of view, the allowable amount of Al ₂ O ₃ contained in the matrix part was examined.

[0014] When we performed the permissible amount of experiments of the _Al 2 _{O 3,} the amount of _Al 2 _{O 3} contained in the matrix section, 2
It was found that the corrosion resistance of bricks did not decrease significantly up to the mass%. Therefore, Al ₂ O ₃ in the matrix
However, it has been found that up to 2% by mass is acceptable.

In order to reduce the amount of Al ₂ O ₃ contained in the matrix portion to 2% by mass or less, there is a slight difference depending on the composition of the spinel clinker used, but the mixing ratio of the spinel clinker of less than 1 mm is 3% by mass. It must be less than.

On the other hand, it was also found that when the particle size of the spinel clinker is 1 mm or more, the refractory material has excellent corrosion resistance. This is because the distribution of the melilite phase exists locally around the spinel clinker, and the existence itself has little influence on the corrosion resistance. Rather, it is considered that the presence of this melilite phase has a positive effect of absorbing thermal stress due to melting of the melilite phase and suppressing the propagation of cracks, and as a result, improving the heat-resistant spalling property. . However, the spinel clinker having a particle size of less than 1 mm forms a matrix of bricks having a melilite phase, which further lowers the corrosion resistance of the matrix portion, which has relatively lower corrosion resistance than the coarse grain portion,
Brick will have a negative effect on the overall corrosion resistance.

The blending ratio of spinel clinker having a diameter of 1 mm or more in the brick is preferably in the range of 3 to 30% by mass. Because, if it is less than 3% by mass, the effect of improving the spalling resistance due to the formation of the melilite phase around the spinel clinker cannot be obtained, and if it exceeds 30% by mass, the contact with the rare earth oxide is increased. The melilite phase is excessively produced, and an excessive liquid phase is produced at a high temperature. This is because the corrosion resistance is lowered.

That is, according to the present invention, in a mag spinel brick to which a rare earth oxide is added, A in the matrix is
It is characterized in that it does not contain l ₂ O ₃ or the content is specified to be 2% by mass or less.

[0019] The rare earth oxide-added mag spinel brick has a raw material composition of a magnesia clinker, a rare earth oxide raw material, and a spinel clinker, and the spinel clinker used as the raw material has a particle size composition of 1 mm or more. 3 to 30% by mass, and a particle size of less than 1 mm is less than 3% by mass.

As the magnesia clinker, a raw material produced by either a sintering method or an electrofusion method can be used. From the viewpoint of corrosion resistance against slag, MgO is 90% by mass or more, preferably 95% by mass or more.

As the spinel clinker, a raw material produced by either a sintering method or an electrofusion method can be used. The amount ratio of MgO and Al ₂ O ₃ , which are raw materials commercially available as spinel clinker, is spinel composition, that is, MgO is about 28% by mass and Al ₂ O ₃ is about 72% by mass. There is also a clinker that is biased toward the MgO side or the Al ₂ O ₃ side. The present invention can use any of these clinker. However, from the viewpoint of corrosion resistance to slag, as in the case of magnesia clinker, Mg
The total amount of O and Al ₂ O ₃ is 90 mass% or more, preferably 9
5 mass% or more is required.

Raw materials for rare earth oxides include Y ₂ O ₃ and C
Fine powders such as eO ₂ and La ₂ O ₃ are used. A high-purity raw material containing 99% by mass or more of one kind of rare earth oxide alone is, of course, suitable, but monazite
And bustnasite,
A mixture of rare earth oxides obtained by processing and firing ores such as xenotime (monazite and bastnasite as starting materials are commonly known as “rare oxides”).
It is also possible to use a raw material in which various rare earth oxides are mixed. It is also possible to use a raw material in which a rare earth element is dispersed in another component by a method of mixing these rare earth oxide raw materials with a magnesia clinker and melting them in an electric furnace.

The compounding ratio of the rare earth oxide is 0.2% by mass.
If the amount is less than 20% by mass, the effect of adding the rare earth oxide cannot be expected, and since the rare earth oxide is generally expensive as compared with the magnesia raw material, if it exceeds 20% by mass, the effect commensurate with the raw material price is obtained. Cannot be expected, so 0.
A range of 2 to 20% by mass is suitable.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below based on Examples.

Seawater magnesia clinker having a purity of about 99% by mass as a starting material, and a commercially available Y ₂ O ₃ reagent having a purity of 99.9% by mass or more as a rare earth oxide material, CeO ₂
Reagent, La ₂ O ₃ reagent, and two kinds of sintered spinel clinker having a purity of about 99% by mass (spinel clinker A: MgO).
About 28 mass%, spinel clinker B: MgO about 50 mass%). Further, as the binder, a commercially available phenol resin for fired brick and an aqueous magnesium chloride solution for unfired brick were used.

The raw materials were blended in the ratios shown in Table 1 and kneaded. Further, it was molded into a parallel shape (230 × 114 × 65 mm) with a molding pressure of 1500 kg / cm ^{3 by} a hydraulic press, and
Sample invention products AE were prepared by firing at 00 ° C for 12 hours.

As a comparative example, mag spinel brick O and
Maguro brick P and Japanese Unexamined Patent Publication No. 6-116014
Rare earth oxide-containing mag spinel bricks prepared in accordance with
QS was prototyped. As these starting materials,
In addition, chromium ore (Cr_TwoO _ThreeUse about 50%)
did.

The effect of the application of rare earth oxides on the magspinel bricks in each sample on the properties and the effect of the particle size and chemical composition of the spinel clinker on the properties was investigated.

The prototype bricks were evaluated for general physical properties, hot bending strength, and corrosion resistance. General physical properties, namely bulk specific gravity, apparent specific gravity, apparent porosity, and hot bending strength are JI
It measured according to the method of S description.

In Table 1, "Matrix Al ₂ O
“ ₃ amount” is a value obtained by analyzing the prototype brick and the used raw material by a fluorescent X-ray method and measuring the content of each Al ₂ O ₃ and the proportion of the spinel clinker blended as particles of 1 mm or more. Al ₂ O ₃ amount)-(particle size 1 mm
Al ₂ O contained in the above spinel clinker
₃ amount) ”.

The corrosion resistance was evaluated by the slag dipping method. CaO
50 mass%, SiO ₂ 20 mass% and Al ₂ O ₃ 3
The slag composition obtained by adding 0% by mass of B ₂ O ₃ to the composition containing 0% by mass was charged and melted in a graphite crucible set in a high-frequency induction furnace, and the temperature was maintained at 1700 ° C. A sample processed to 180 × 20 × 20 mm was immersed in this molten slag for 40 minutes to a depth of 90 mm. The volume of the sample after immersion was measured by the Archimedes method after cooling, and the rate of decrease in volume before and after immersion was taken as the corrosion rate. In the table, the ratio of the magro-brick P of the comparative example with P as 100 is shown as an erosion rate index. The smaller this value is, the better the corrosion resistance is. Also, for some samples, most of the dip was lost during the test so that it was torn off. This is seen when the corrosion resistance to slag is extremely weak. In such a case, in the table, for example, "10 minutes burn through" and the time when this phenomenon was confirmed are shown.

The heat resistant spalling property was evaluated by a hot metal dipping method. The pig iron was melted by a high frequency induction furnace and kept at 1500 ° C. Then, the sample processed to 180 × 40 × 40 mm was dipped to a depth of 90 mm for 3 minutes and immediately taken out. Immediately thereafter, the same part of the sample is immersed in running water for 1 minute. This process is repeated until the sample peels off due to thermal shock. It is shown that the sample having a larger number of repetitions has a better heat-resistant spalling property. Comparative Example Q shown in the table, which is a general mag spinel brick, has extremely poor corrosion resistance, so the sample burned out during the corrosion resistance test. On the other hand, the invention products A to E containing the rare earth oxides do not have this phenomenon and show corrosion resistance almost equal to or higher than that of magcro bricks. However, even in the case of a brick containing a rare earth oxide as well, Comparative Example R in which 10% by mass of a spinel clinker of less than 1 mm and Comparative Example S in which 4% by mass of the same are mixed have corrosion resistance higher than that of the invention product. Remarkably inferior. When this result is compared with Invention D in which 2% by mass of the spinel clinker of less than 1 mm is mixed, it is shown that there is a threshold value at which the corrosion resistance remarkably changes when the content of the spinel clinker of less than 1 mm is around 3% by mass. From this, 1m
It can be said that a spinel clinker content of less than 3 m is less than 3% by mass in terms of corrosion resistance.

Further, even when compared with the mag spinel brick (Comparative Example Q), which is generally considered to have good spalling resistance, the product of the present invention has remarkably high heat spalling resistance. This strongly suggests that the ordinary mag spinel brick and the product of the present invention have different mechanisms for improving the heat-resistant spalling resistance.

Sample E using spinel clinker B exhibits almost the same characteristics as sample B using spinel clinker A. From this, M of spinel clinker
The composition ratio of gO: Al ₂ O ₃ is considered to have almost no effect on the characteristics of the brick.

Next, Table 2 shows an example in which the influence of the amount of rare earth added on the quality of the invention product was investigated.

Inventive products F to M, which are examples of the present invention, were prepared by mixing various raw materials in the ratios shown in Table 2. The preparation conditions and evaluation method for each sample are the same as those in Table 1.

Each of the invention products F to M showed almost the same corrosion resistance as the MgO brick (containing no spinel clinker) mixed with the same amount of the rare earth oxide. Moreover, the heat-resistant spalling property is extremely high. The heat-resistant spalling property tends to be improved according to the amount of the rare earth oxide added.

Next, the influence of the amount and type of rare earth oxide added on the quality of the invention was investigated. Various raw materials were blended in the ratios shown in Table 2. Manufacturing conditions and evaluation methods are the same as those in the example of Table 1. The “amount of Al ₂ O _{3 in the} matrix” shown in Table 1 was 0.3% by mass,
The description is omitted. Comparing the invention products F, G, B and H,
Corrosion resistance is improved even with the addition of rare earth oxide of 0.3%, and magcro brick shows the same value. The corrosion resistance reaches its maximum near 5% of the rare earth oxide, and tends to decrease slightly above that. The spalling resistance tends to increase as the added amount increases. Further, the invention product B, in I through _M, and _{Y 2 O 3, CeO 2,} La 2 O 3, 3 in the type of result of comparison a typical rare earth _oxide, the ratio of Y 2 _{O 3} is high invention The higher the quality, the higher the corrosion resistance. The same tendency is observed in the heat-resistant spalling property, although there is a slight difference.

Table 3 below shows an example in which the same investigation was carried out when the present invention was applied to unfired bricks. Table 3
The raw materials blended in the ratio shown in N were kneaded. Further, it was formed into a parallel shape by a hydraulic press with a forming pressure of 1500 kg / cm ³ , and dried at 150 ° C.

As comparative examples, magnesia unfired bricks T, magcro unfired bricks U, magspinel unfired bricks V, and rare earth oxide-containing magspinel bricks W according to the description of JP-A-6-116014 were prepared. did.

Each sample was evaluated in the same manner as the example in Table 1. Comparative Example V, which is a general mag spinel brick, had extremely poor corrosion resistance, so the sample burned out during the corrosion resistance test. On the other hand, the invention product N of the example of the present invention containing the rare earth oxide does not have this phenomenon, and the maguro unfired brick shows the same or higher corrosion resistance. However, even in the case of a brick containing a rare earth oxide as well, in Comparative Example W containing 10% by mass of a spinel clinker of less than 1 mm, a phenomenon was observed in which the sample burned out during the corrosion resistance test. From this, it can be seen that the spinel clinker content of less than 1 mm is required to be less than 3% by mass as in the case of the baked bricks shown in Tables 1 and 2 from the viewpoint of corrosion resistance. In addition,
It can be seen that the invention products of the examples of the present invention have remarkably high heat-resistant spalling resistance even when compared with Comparative Example V, which is generally good in spalling resistance. This strongly suggests that the magspinel brick and the invention product have different mechanisms for improving the heat-resistant spalling resistance, as in the case of the fired brick.

The invention products shown in Table 1 were partially used for a ladle slag line in a steelmaking factory, and the situation was investigated after the use. Adjacent to the invention, 4% less than 1 mm spinel clinker
The contained mag spinel brick (Comparative Example S in Table 1) was applied and compared.

In the case of the present invention, the wear rate estimated from the residual size was about 50% lower than that of the comparative example, and the effectiveness of the present invention was confirmed. In addition, when bricks were collected and investigated, it was found that the slag infiltration depth was about half that of magro bricks, no cracks were observed, and the durability was more than doubled in an actual furnace.

As is clear from these examples, as a lining in a furnace for metal refining such as secondary refining of steel, the corrosion resistance can be remarkably improved, and a rare earth oxide for a furnace for metal refining can be significantly improved. It is now possible to use it as a contained mag spinel brick.

Table 1 Table 2 Table 3

[0046]

Effect of the Invention Since it does not contain any chromium raw material that may be converted to hexavalent chromium after use, the cost of special treatment of used brick is unnecessary. Moreover, the influence of environmental pollution is almost eliminated.

2. A refractory material having remarkably excellent spalling resistance can be obtained as compared with conventional mag spinel bricks containing no rare earth oxide.

3. As the lining of a kiln for metal refining such as secondary refining of steel, the durability is extremely excellent, which greatly contributes to the reduction of the refractory unit consumption of the furnace.

Continued front page    F-term (reference) 4G030 AA07 AA12 AA13 AA14 AA36                       BA25 CA01 GA11 GA14 GA22                       GA27 HA12                 4K051 AA02 AA05 AA06 AB03 AB05                       BE03

Claims (3)

[Claims] 1. A magnesia-spinel brick containing a rare earth oxide, wherein the matrix of the brick does not contain an Al ₂ O ₃ component. 2. A magnesia-spinel brick in which a rare earth oxide-added magnesia-spinel brick has an Al ₂ O ₃ component content in a matrix of the brick of 2% by mass or less. 3. A raw material composition comprising a magnesia clinker, a rare earth oxide raw material, and a spinel clinker, wherein the particle size composition of the spinel clinker used as the raw material is
3 to 30% by mass for particle size of 1 mm or more, 3 for particle size of less than 1 mm
Magnesia-spinel brick that is less than wt%.