JPH06170504A - Nozzle for continuous casting - Google Patents

Abstract

PURPOSE:To provide a nozzle for continuous casting having high corrosion resistance and high heat resistance. CONSTITUTION:At least the upper part from a meniscus in the nozzle for continuous casting is composed of 20-60wt.% hollow alumina aggregate having 1.0-0.1mm grain size and 10-50mum shell thickness, 10-30wt.% easy-to-sintering alumina and 20-35wt.% graphite and the balance refractory composed of electromelted alumina and/or sintered alumina. As the other way, at least the upper part from the miniscus in the nozzle for continuous casting is composed of 20-60wt.% hollow alumina aggregate having 1.0-0.1mm grain size and 10-50mum shell thickness and 15-35wt.% graphite and the balnce refractory composed of electromelted zirconia and/or baddeleyite.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a refractory material containing graphite and hollow aggregates as essential components and having excellent high corrosion resistance and heat insulation property at least above a meniscus such as a long nozzle or a dipping nozzle. The present invention relates to an established continuous casting nozzle.

[0002]

2. Description of the Related Art Generally, in a continuous casting method, a long nozzle is attached between a ladle and a tundish to circulate molten steel to prevent oxidation during casting. An immersion nozzle is installed between the tundish and the mold to prevent oxidation and control the flow rate of molten steel in the same manner.Since these long nozzles or immersion nozzles place importance on spall resistance and corrosion resistance, graphite is used. Alumina-graphitic refractory containing 20-35% by weight is used.

Since the above alumina-graphite nozzle contains a large amount of graphite, it is excellent in spall resistance, but
Since the thermal conductivity is high, the heat loss of the molten steel passing through the inside is large, and nozzle clogging may occur due to solidification of the molten steel or adhesion of alumina present in the molten steel. As a countermeasure against this, a method of installing a heat insulating slit inside the nozzle has been proposed, but it has drawbacks such as high manufacturing cost and a small effective layer of the nozzle. On the other hand, it has been proposed to use a porous raw material for the nozzle aggregate, but the aggregate having open pores has a drawback that the corrosion resistance is lowered.

An object of the present invention is to provide a continuous casting nozzle having high corrosion resistance and high heat insulation.

[0005]

That is, according to the present invention, a hollow alumina aggregate 20-60 having a grain size of 1.0-0.1 mm and a shell thickness of 10-50 μm is provided at least above the meniscus of a continuous casting nozzle. % By weight, easily sinterable alumina 10 to 3
It is to provide a nozzle for continuous casting, characterized in that a refractory made of 0% by weight, 20 to 35% by weight of graphite, and the balance of fused alumina and / or sintered alumina is arranged (hereinafter, referred to as the first Invention).

Further, according to the present invention, a particle size of 1.0 to 0.1 mm, at least above the meniscus of the nozzle for continuous casting,
Hollow zirconia aggregate 20 to 6 having a shell thickness of 10 to 50 μm
It is to provide a nozzle for continuous casting, characterized in that a refractory made of 0% by weight, 15 to 35% by weight of graphite, and the balance of fused zirconia and / or baddelite is disposed (hereinafter referred to as a second invention). ).

[0007]

In the continuous casting nozzle of the present invention, a refractory containing graphite and hollow aggregates as essential components is disposed at a portion of the continuous casting nozzle that is subject to heat change, that is, at least above the meniscus, and thus continuous casting is performed. It imparts high corrosion resistance and heat resistance to the application nozzle.

The refractory material used in the first invention of the present invention is 20 to 60% by weight of hollow alumina aggregate having a grain size of 1.0 to 0.1 mm and a shell thickness of 10 to 50 μm, and easily sinterable alumina 10 to 10.
30% by weight and 20-35% by weight graphite,
The balance consists of fused alumina and / or sintered alumina.

The hollow alumina aggregate used for this refractory material is
An electromelted product or a sintered product having a dense shell is preferable. The shell thickness of the hollow alumina aggregate is preferably in the range of 10 to 50 μm, and when a large amount of the hollow alumina aggregate having a shell thickness of less than 10 μm is included, the strength of the aggregate is low and the hollow alumina aggregate during molding is hollow. Aggregate is damaged, heat insulation is not obtained, and corrosion resistance is reduced. On the other hand, if a large amount of hollow alumina aggregate having a shell thickness of more than 50 μm is contained, the hollow portion becomes small, and heat insulation is not obtained, which is not realistic. The particle size of the hollow alumina aggregate is preferably 1.0 to 0.1 mm. The amount of hollow alumina aggregate added is 20 to 60% by weight.

The reason why the addition amount of the hollow alumina aggregate is limited to the range of 20 to 60% by weight will be explained by taking the case of using 30% by weight of graphite as an example. FIG. 1 is a graph showing the relationship between the blending amount of hollow alumina aggregate and the thermal conductivity in an alumina-graphite refractory containing 30% by weight of graphite, and the addition amount of hollow alumina aggregate was 20% by weight. If it is less than the above range, the thermal conductivity of the nozzle for continuous casting is large and the heat insulating property cannot be obtained. Further, if the amount of the hollow alumina aggregate added exceeds 60% by weight, the corrosion resistance decreases, which is not preferable. The hollow alumina aggregate has a particle size of 150 to 500 μm and a shell thickness of 3
The thing of 0 micrometer was used.

As the easily sinterable alumina, the grain size is 1
It is preferably 0 μm or less, more preferably 1 μm or less.
The reason for using the easily sinterable alumina is that the hollow alumina aggregate alone has poor sinterability and cannot be dense in terms of structure. Note that calcined alumina, σ-alumina, or the like can be used as the easily sinterable alumina. The amount of easily sinterable alumina added is 10 to 30% by weight. Note that, for the balance, it is possible to use fused alumina and / or sintered alumina which has been generally used conventionally.

Further, as graphite, natural graphite, coke, electrode scrap, carbon black, artificial graphite or the like can be used. The amount of graphite added must be within the range of 20 to 35% by weight. If the amount of graphite added is less than 20% by weight, sufficient spalling resistance cannot be obtained.
If it exceeds, corrosion resistance and wear resistance decrease, which is not preferable.

This refractory material includes carbides such as SiC and B ₄ C, which are usually used for continuous casting nozzles, Si and A.
It is also possible to add metals such as 1 and Fe-Si. The addition amount of these components is 10% by weight or less.

The refractory used in the second invention of the present invention comprises 20 to 60% by weight of hollow zirconia aggregate having a grain size of 1.0 to 0.1 mm and a shell thickness of 10 to 50 μm and 15 to 35% by weight of graphite. It is contained, and the balance consists of fused zirconia and / or baddelite.

Here, the particle size range and shell thickness of the hollow zirconia aggregate are the same as those of the above-mentioned hollow alumina aggregate. The amount of the hollow zirconia aggregate added is in the range of 20 to 60% by weight. If the amount of the hollow aggregate added is less than 20% by weight, the heat insulating effect is poor, and if it exceeds 60% by weight, the corrosion resistance decreases, which is not preferable.

Further, as the refractory used in the second invention, it is possible to use an electrofused zirconia, baddelite or the like which has been generally used conventionally.

Further, as graphite, natural graphite, coke, electrode scrap, carbon black, artificial graphite or the like can be used. The amount of graphite added must be within the range of 15 to 35% by weight. If the amount of graphite added is less than 15% by weight, sufficient spalling resistance cannot be obtained.
If it exceeds, corrosion resistance and wear resistance decrease, which is not preferable.

This refractory material includes carbides such as SiC and B ₄ C, which are usually used in continuous casting nozzles, Si and A.
It is also possible to add metals such as 1 and Fe-Si. The addition amount of these components is 10% by weight or less.

The refractory used in the nozzle for continuous casting according to the present invention contains 5 to 20% by weight of the above-mentioned refractory material compounded with an organic binder such as phenol resin and pitch.
It can be obtained by kneading with a certain degree of use, molding into a required shape, and then firing in a non-oxidizing atmosphere.

The continuous casting nozzle of the present invention can be obtained by disposing the refractory material having the composition as described above at least above the meniscus of the continuous casting nozzle. For example, a refractory material having the above-described composition may be arranged in the configuration shown in FIGS. 2B and 2C. Note that FIG.
(A) is a sectional view showing an example of a conventional continuous casting nozzle.

[0021]

EXAMPLES The continuous casting nozzle of the present invention will be further described below with reference to examples. Example A predetermined amount of phenol resin was added to each of the formulations shown in Table 1, mixed and kneaded, and then 1.5 with a rubber press.
It was pressure molded at ton / cm ² . Next, the obtained molded body is heated to 1000 ° C. in a non-oxidizing atmosphere in coke breeze.
Then, it was calcined and subjected to a caulking treatment. Table 1 also shows a comparison of various properties, erosion resistance and thermal conductivity of the obtained fired bodies.

[0022]

[Table 1]

When the product 1 of the present invention in Table 1 was used as the material of the main body of the immersion nozzle of Company A, the comparison product 4 was found to be uncastable due to the metal and alumina adhering to the inner pipe at 4 cc. In the product 2, the clogging of the inner pipe was small even after 5 cc casting, and moreover, it was in a state where multiple casting was possible.

[0024]

EFFECTS OF THE INVENTION In the conventional material, heat loss from the wall surface of the nozzle for continuous casting causes a large amount of metal and alumina to adhere to the inner tube of the nozzle, which hinders continuous casting. A corrosion-resistant, highly heat-insulating continuous casting nozzle can be obtained, and by disposing the continuous casting nozzle of the present invention at least on the upper part of the meniscus, heat loss from the continuous casting nozzle is reduced, enabling multiple casting. It was This effect can be applied not only to the nozzle for continuous casting but also to other uses for the purpose of reducing heat loss.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between a blending amount of a hollow alumina raw material and a thermal conductivity in an alumina-graphite refractory material containing 30% by weight of graphite.

FIG. 2 is a sectional view showing a structure of a refractory material in a continuous casting nozzle of a conventional product and a product of the present invention.

Claims (2)

[Claims] 1. A continuous casting nozzle having a grain size of 1.0 to 0.1 mm and a shell thickness of 10 to at least above a meniscus.
20-60 wt% of 50 μm hollow alumina aggregate, 10-30 wt% of easily sinterable alumina and 20-35 wt% of graphite
A nozzle for continuous casting, characterized in that a refractory material containing Al, and the remainder being composed of fused alumina and / or sintered alumina is disposed. 2. A particle size of 1.0 to 0.1 mm and a shell thickness of 10 at least above the meniscus of the continuous casting nozzle.
Nozzle for continuous casting characterized by containing a refractory material containing 20 to 60% by weight of a hollow zirconia aggregate of 50 μm and 15 to 35% by weight of graphite, and the rest of which is made of fused zirconia and / or badderite. .