JPH06285598A - Refractories for continuous casting nozzle - Google Patents

Abstract

PURPOSE:To provide the refractories for a continuous casting nozzle having excellent thermal impact resistance. CONSTITUTION:(1) The refractories are formed by adding 1 to 30wt.% spherical carbon powder to 100 compd. essentially consisting of refractory raw materials and graphite and mixing, molding and calcining the mixture. (2) The refractories are formed by adding 1 to 30wt.% spherical carbon powder to 100 compd. which consists essentially of the refractory raw materials and graphite and is added with powder of Al or Si, and mixing, molding and calcining the mixture. As a result, the thermal impact resistance of the refractories for the continuous casting nozzle is improved and the reduction of working costs, such as reduction of the cost of the nozzle for continuous casting and relaxation of preheating condition, re attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refractory for a continuous casting nozzle used in the steel industry.

[0002]

2. Description of the Related Art A continuous casting nozzle is an important member used for pouring molten metal from a ladle into a tundish, casting from a tundish into a mold, etc. in a continuous steel casting process. This mainly prevents oxidation of the molten metal, inclusion of non-metallic inclusions, turbulent flow splash, and the like. Since such continuous casting nozzles are used under extremely severe conditions, they are required to have particularly excellent thermal shock resistance, corrosion resistance and mechanical strength. Conventionally, siliceous materials have been used for refractory materials for continuous casting nozzles, but recently, mainly alumina-graphitic (AG) materials having carbon bonds, zirconia-graphite (Z
(G quality) material or the like is used. (For example, JP-A-57-
No. 3258), a nozzle for continuous casting using this AG material and ZG material has high strength because it has a carbon bond inside its structure, and has excellent thermal conductivity and thermal shock resistance, and corrosion resistance. Is also excellent.

[0003]

However, there is a drawback that carbon forming a carbon bond is oxidized or decarburized in an oxidizing atmosphere at a high temperature, resulting in a marked decrease in strength. Moreover, the thermal shock resistance is not sufficient under severe operating conditions such as rapid heating and rapid cooling. That is, a large number of cracks are generated on the inner surface or the surface of the nozzle that is rapidly heated by contacting with high-temperature molten steel, the cracks that develop and expand, and the refractory that constitutes the nozzle often peels off. To be As a result, the entrainment of oxygen causes inconveniences such as deterioration of quality of the obtained steel, which is a serious problem. It is an object of the present invention to provide a refractory for a continuous casting nozzle, which has excellent thermal shock resistance and does not crack even under severe use conditions such as rapid heating and rapid cooling.

[0004]

The refractory material for a continuous casting nozzle according to the present invention has the following properties to improve thermal shock resistance:
(1) 1 to 30% by weight of spherical carbon powder is added to a mixture 100 containing a refractory raw material and graphite as a main component, mixed, molded and fired, and (2) a refractory raw material It is characterized in that 1 to 30% by weight of spherical carbon powder is added to a compound 100 containing graphite as a main component and powder of Al or Si added, and mixed, molded and fired.

[0005]

The refractory for a continuous casting nozzle of the present invention comprises a slab continuous casting machine, a plume continuous casting machine, a billet continuous casting machine,
A refractory for long nozzles and immersion nozzles used in twin roll continuous casting machines, twin belt continuous casting machines, single belt continuous casting machines, single roll continuous casting machines and the like.

In the refractory for a continuous casting nozzle of the present invention, the carbon source includes natural, artificial graphite, mesophase carbon, coke, carbon black, etc., and has a purity of 90% or more in order to prevent deterioration of corrosion resistance due to impurities. Things are desirable.

The refractory raw material is a neutral or acidic refractory raw material which has excellent corrosion resistance and is difficult to react with carbon, such as fused alumina, sintered alumina, fused zirconia, sintered zirconia, fused calcium zirconate. Can be used, 90% to prevent deterioration of corrosion resistance due to impurities
It is preferable that the purity is not less than the above.

The amount of spherical carbon powder added is set to 1 to 30% by weight in order to improve the thermal shock resistance. If it is less than 1% by weight, the thermal shock resistance improving effect cannot be obtained, and if it exceeds 30% by weight, the structure is This is because it causes deterioration.

The spherical carbon powder refers to spherical particles made of graphite, mesophase carbon, coke, carbon black or the like, and preferably has a purity of 90% or more in order to prevent deterioration of corrosion resistance due to impurities. The spherical carbon powder in the present invention does not necessarily have to be spherical, and refers to a powder having a curved surface, and preferably has a particle size of 500 microns or less.

The spherical carbon powder in the present invention improves the thermal shock resistance by the following mechanism. The crack generated by the thermal shock propagates through the grain boundaries of the carbon and the refractory raw material particles forming the refractory structure. If spherical carbon powder is present at the destination of this crack, the progress of the crack stops at the surface of the spherical particle, or the crack has to bypass the spherical carbon particle and propagate, and the crack progresses until it breaks. The length becomes longer.

Further, the thermal expansion behavior of the added spherical carbon particles is different from that of the compounded carbon and isotropic, so that microcracks are formed inside the refractory structure. The microcracks thus generated disperse the progress of the cracks generated by thermal shock and absorb the propagation energy of the cracks, thereby suppressing the progress of the cracks. The thermal shock resistance can be improved by the above two effects.

In order to improve the strength of the refractory for a continuous casting nozzle of the present invention, it is possible to use Al or Si powder which forms a carbide, a nitride or an oxide by a reaction inside the refractory during use. .

According to the results of the experiments conducted by the present inventors using fused alumina and scaly graphite, as shown in FIG. 1, the strength of Al or Si metal powder increases with the addition amount up to 10% by weight. Although it is increased, the strength is lowered when the addition amount exceeds 10% by weight, and the addition amount of metal Al or Si is preferably 10% by weight or less.

Also in the refractory for a continuous casting nozzle of the present invention to which Al or Si powder is added, the effect of the spherical carbon powder acts in the same manner as described above, and the thermal shock resistance can be improved.

[0015]

EXAMPLES The present invention will be described below based on examples. An example of manufacturing and using the refractory for a continuous casting nozzle of the present invention will be shown. 3 to 5 wt% of a phenolic binder is added to 100 wt% of the raw material composition shown in Table 1,
Kneading, rubber press molding, drying (90 ° C x 24 hours),
Reduction firing (900 ° C. × 3 hours) was carried out to manufacture the refractory for a continuous casting nozzle of the present invention.

The refractory raw materials used were fused alumina, sintered alumina, fused zirconia, sintered zirconia, fused calcium zirconate, carbon was 99% pure scaly graphite, and metal powder was Al or Si. .

The thermal shock resistance of the refractory material for continuous casting nozzles of the present invention was evaluated by repeatedly immersing a sample of a certain shape in molten steel at 1600 ° C. for 90 seconds, water cooling for 15 seconds, and air cooling for 60 seconds up to 20 times. The evaluation of the test was evaluated as ◯ when the number of times of peeling by this test was 20 or more, and as x when peeled less than 20 times.

[0018]

[Table 1]

Table 2 shows a comparative example. The phenolic binder is added in an amount of 3 to 5 to 100% by weight of the raw material composition shown in Table 2.
Add wt%, knead, rubber press mold, dry (90
C. × 24 hours) and reduction firing (900 ° C. × 3 hours) were carried out to manufacture a refractory for a continuous casting nozzle of a comparative example.

The refractory raw materials used were fused alumina, sintered alumina, fused zirconia, sintered zirconia, fused calcium zirconate, carbon was 99% pure scaly graphite, and metal powder was Al or Si. .

To evaluate the thermal shock resistance of the refractory material for continuous casting nozzles of Comparative Example, a sample of a certain shape was immersed in molten steel at 1600 ° C. for 90 seconds, water-cooled for 15 seconds, and air-cooled for 60 seconds, up to 20 times. The evaluation of the test was evaluated as ◯ when the number of times of peeling by this test was 20 or more, and as x when peeled less than 20 times.

[0022]

[Table 2]

As is clear from Table 1, all the continuous casting nozzles of the present invention show excellent thermal shock resistance. In contrast, the comparative examples shown in Table 2 are inferior in thermal shock resistance.

[0024]

According to the present invention, the following effects can be obtained. It is possible to improve thermal shock resistance, which was technically facing the wall for conventional refractory for continuous casting nozzle,
It is possible to reduce the cost of the continuous casting nozzle and to reduce the work cost such as relaxing the preheating condition.

[Brief description of drawings]

FIG. 1 A is used as a refractory raw material using fused alumina and scaly graphite.
It is a figure which shows the relationship between the intensity | strength when adding 1 or Si metal powder, and the addition amount.

[Procedure amendment]

[Submission date] July 9, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

[0005]

The refractory for a continuous casting nozzle of the present invention is a slab continuous casting machine, a bloom continuous casting machine, a billet continuous casting machine,
A refractory for long nozzles and immersion nozzles used in twin roll continuous casting machines, twin belt continuous casting machines, single belt continuous casting machines, single roll continuous casting machines and the like.

Claims (2)

[Claims] 1. A blend 1 comprising a refractory raw material and graphite as main components.
1 to 30% by weight of spherical carbon powder,
A refractory for a continuous casting nozzle, which is obtained by mixing, molding and firing. 2. A spherical carbon powder is added in an amount of 1 to 30% by weight to a compound 100 containing a refractory raw material and graphite as main components and an Al or Si powder added, and mixed, molded and fired. Refractory for continuous casting nozzle, characterized by