JPH05117044A - Thermal spalling-resistant castable refractory - Google Patents

Abstract

PURPOSE:To improve the durability in use in a steel bath part by improving the thermal spalling and corrosion resistance. CONSTITUTION:An alumina.spinel-based castable refractory prepared by blending an alumina clinker with a spinel clinker is blended with an alumina.zirconia clinker in an amount so as to provide 5-20wt.% content thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to castable refractories, and more particularly to an alumina-spinel castable refractory having excellent heat spalling resistance.

[0002]

2. Description of the Related Art In recent years, when refractory linings have been applied to various kilns, the use of irregular refractory materials has led to the rapid progress of so-called irregularization, and lining of molten metal containers such as ladle and tundish. The zircon castable refractory using the zircon raw material as an aggregate has been used for the above, which has advantages of relatively low cost and less generation of thermal spalling and structural spalling in terms of performance.

However, as the production amount of high-grade steel increases and refining in a ladle becomes more severe, the conditions for processing molten steel become more severe, and the durability required for refractory linings becomes higher. Corrosion resistance of high quality castable refractories is not always sufficient, and castable refractories with excellent corrosion resistance are required, and in order to reduce non-metallic inclusions in steel, non-metallic substances in molten steel are required. There is a strong demand for neutral or basic castable refractories with low elution.

Therefore, instead of the zircon castable refractory, an alumina-spinel castable refractory prepared by mixing an alumina raw material and a spinel raw material has come to be used. And in order to further improve its performance, for example, spinel clinker 10-8
5 parts by weight, 5 to 30 parts by weight of alumina, and 10 to 25 parts by weight of high-alumina cement, and an alumina-spinel castable refractory (Japanese Patent Laid-Open No. 55-2300), at least 60 parts by weight of spinel clinker and alumina. Alumina spinel castable refractory composed of 10 to 35 parts by weight of clinker and 3 to 10 parts by weight of alumina cement (JP-A-60-60985),
Further, an alumina-spinel refractory material composed of 50 to 90 parts by weight of alumina clinker, 5 to 40 parts by weight of spinel clinker having a particle diameter of 1 mm or less, and 3 to 25 parts by weight of alumina cement (Japanese Patent Laid-Open No. 1-87577). Various refractories have been proposed.

[0005]

However, when the above-mentioned conventional alumina-spinel castable refractory material is used in an actual furnace, cracks are generated in parallel with the operating surface due to repeated heating and cooling, and therefore peeling occurs. There is a problem that so-called heat spalling occurs. And
In order to solve this problem, attempts have been made to add a coarse aggregate with a diameter of about 30 mm to disperse thermal stress, but castable refractories having sufficient heat resistant spalling resistance have not yet been obtained. The reality is that it is not.

The present invention solves the above problems, and an object of the present invention is to provide an alumina-spinel castable refractory having sufficient corrosion resistance and excellent heat spalling resistance.

[0007]

In order to achieve the above object, the heat-resistant spalling castable refractory of the present invention is an alumina-spinel castable refractory obtained by blending alumina clinker and spinel clinker,
Alumina at a rate such that the content rate is 5 to 20% by weight.
It is characterized by containing zirconia clinker.

In the heat-resistant spalling castable refractory of the present invention, the alumina-zirconia clinker is blended with the alumina-spinel castable refractory, and the alumina-zirconia clinker is contained in the castable refractory composition. It exhibits a coefficient of linear thermal expansion different from that of the raw material and the spinel raw material. As a result, in the structure of the castable refractory, a portion having a coefficient of linear thermal expansion lower than that of the alumina / spinel raw material by about 0.2 to 0.5% is formed, and the alumina / spinel castable refractory and the alumina are formed in the matrix. -Microcracks occur between zirconia clinker. And
This microcrack absorbs thermal stress, suppresses the generation of cracks that cause peeling of the castable refractory structure, and prevents the peeling.

The alumina-zirconia clinker used in the heat resistant spalling castable refractory of the present invention is preferably produced by melting alumina and zirconia. Further, the content ratio of zirconia in the alumina-zirconia clinker is 10 to 3
It is preferably 0% by weight. This is because when the content of zirconia is less than 10% by weight, it becomes close to that of alumina alone and its characteristics are too strong, so that the coefficient of hot linear expansion does not change much from the coefficient of hot expansion of alumina alone. The significance of adding zirconia clinker is lost,
Further, when the content of zirconia exceeds 30% by weight, abnormal expansion due to zirconia becomes prominent and volume stability is impaired, which is not preferable.

Alumina / zirconia clinker produced by melting alumina and zirconia has an apparent porosity of 5 to 8%, but the alumina / zirconia used in the heat resistant spalling castable refractory of the present invention. The apparent porosity of the clinker is preferably 10% or less.

Further, the compounding ratio of the alumina-zirconia clinker is 5 to 5 of the total castable refractory after compounding.
It is preferably in the range of 20% by weight. That is, 5
This is because if it is less than 10% by weight, the desired effect cannot be obtained with respect to the heat-resistant spalling property, and if it exceeds 20% by weight, the abundance ratio of the alumina-spinel main raw material decreases and the characteristics deteriorate.

The composition of the alumina / spinel castable refractory as the base material is not particularly limited, but 70 to 75 parts by weight of the alumina raw material and the spinel clinker 20 are used.
Good results could be obtained by using a castable refractory composed of .about.25 parts by weight and 5-8 parts by weight of alumina cement.

In the heat-resistant spalling castable refractory of the present invention, silica flour, a dispersant (water reducing agent), a curing accelerator, a curing retarder, etc. can be added as required.

[0014]

EXAMPLES Hereinafter, the features of the present invention will be described in more detail by showing examples of the present invention together with comparative examples. In this example, the components were blended at the blending ratios shown in Table 1, and the alumina of Examples 1, 2, 3 and Comparative Examples 1, 2 were mixed.
A spinel castable refractory material was prepared, and the physical properties shown in Table 1 were measured using this as a sample. In addition, Comparative Example 1
It is an alumina-spinel refractory that does not contain an alumina-zirconia clinker, and Comparative Example 2 is an alumina containing an alumina-zirconia clinker in a ratio (3% by weight) smaller than the range (5 to 20% by weight) of the present invention. -It is a spinel refractory.

[0015]

[Table 1]

The alumina / zirconia clinker blended in Examples 1, 2, 3 and Comparative Example 2 shown in Table 1 is an electromelted product containing 71% by weight of alumina and 28% by weight of ZrO ₂ . Its apparent porosity is 5.3%, which is almost the same as that of fused alumina. In addition, this alumina-zirconia clinker has a characteristic tendency of hot linear expansion as compared with alumina. That is, as shown in FIG. 1, the alumina-zirconia clinker has a coefficient of linear thermal expansion that is lower than that of alumina by about 0.2% from around 1100 ° C., and the difference in coefficient of thermal expansion is in the matrix as described above. It causes microcracks and becomes a factor to absorb thermal stress. In this example, the above-mentioned alumina / zirconia clinker was crushed to adjust the particle size to 1 mm or more and added to the alumina / spinel castable refractory.

Further, in Table 1, the spalling test was carried out by heating at 1300 ° C. for 15 minutes and then air cooling for 15 minutes.
The result of the test by the 1300 degreeC air cooling method which repeats this is shown.

Further, in Table 1, the slag test shows test results by the rotary method (1650 ° C. × 6 hours, ordinary steel: converter slag = 1: 1).

As shown in Table 1, Examples 1, 2, and 3 in which alumina / zirconia clinker was blended at a predetermined ratio.
It can be seen that the sample No. 1 has a lower elastic modulus after firing at 1500 ° C. than the samples of Comparative Examples 1 and 2, and the number of times until the spalling test comes off is significantly increased as compared with the comparative example. Therefore, even when actually used, peeling is reduced,
It is judged that the durability is considerably improved.

Further, from the melting loss ratio and the penetration ratio in the slag test, the refractory materials of Examples 1, 2 and 3 have the melting resistance and the slag penetration resistance equal to or better than those of Comparative Examples 1 and 2. As a whole, it can be seen that the corrosion resistance is improved.

Further, regarding bending strength and compressive strength,
The samples of Examples 1, 2 and 3 have substantially the same characteristics as the samples of Comparative Examples 1 and 2, and it can be seen that the samples have practically sufficient strength.

From the above test results, it should be judged that the castable refractories of the present invention represented by Examples 1, 2 and 3 have preferable characteristics as an amorphous refractory for lining a molten steel container. You can

Further, the alumina-spinel refractory material of Example 2 and Comparative Example 1 was used to construct a steel bath portion of a ladle,
It was actually used, and the usage situation and the state after use were observed and compared.

When the refractory material of Comparative Example 1 is used and the number of times it is used exceeds 50 times, it is 30 to 50 mm below the slag line.
Peeling of the thickness occurred, and after 100 times, almost the entire surface was peeled off, and the final durability was 180 times.

On the other hand, when the refractory material of Example 2 was used, no peeling was observed until the number of times of use passed 80 times, and partial peeling was observed even after continued use. However, the peeling did not spread over the entire surface.
As a result, it was found that when the refractory material of Example 2 was used, the final lifespan reached 230 times, and the durability (lifetime) was significantly improved compared to Comparative Example 1.

The present invention is not limited to the above-mentioned embodiment, and the composition of the alumina / spinel castable refractory which is a refractory aggregate, the composition ratio of the alumina / zirconia clinker, etc. may be changed appropriately. Alternatively, it is possible to add various components such as a binder component, a dispersant (water reducing agent), a curing accelerator, and a curing retarder, if necessary, within the scope of the present invention. Is.

[0027]

As described above, the heat-resistant spalling castable refractory of the present invention comprises alumina-spinel castable refractory containing alumina-zirconia clinker in a proportion such that the content is 5 to 20% by weight. Since it is blended, the heat-resistant spalling property is greatly improved and the corrosion resistance is also improved, and it is impossible to obtain sufficient durability when using conventional alumina-spinel castable refractories. Excellent durability can be realized when used in the steel bath section of the container.

As a result, it becomes possible to extend the life of the refractory work body, improve the operating efficiency, and reduce the refractory unit consumption and labor.

[Brief description of drawings]

FIG. 1 is a diagram showing hot linear expansion curves of alumina and alumina-zirconia clinker.

Claims (2)

[Claims] 1. An alumina / zirconia clinker is added to an alumina / spinel castable refractory obtained by mixing an alumina clinker and a spinel clinker at a ratio of 5 to 20% by weight. Heat resistant spalling castable refractories. 2. The heat-resistant spalling castable refractory according to claim 1, wherein as the alumina-zirconia clinker, an alumina-zirconia clinker having a zirconia content in the range of 10 to 30% by weight is used.