JPS62158561A - Nozzle for low-temperature casting of molten steel - Google Patents

Abstract

PURPOSE:To obtain the effect of low-temp. casting by interposing silica refractories between the outside peripheral part and inside peripheral part of a nozzle for casting alumina carbon. CONSTITUTION:The nozzle for low-temp. casting consists of the outside peripheral part 1 and the inside peripheral part 2 as well as the silica refractories to be interposed therebetween. The outside peripheral part 1 and inside peripheral part 2 are formed by molding a material which contains about 30wt% flake graphite and the balance alumina and is added with a binder. The silica refractories 3 are formed by using fused silica, etc. as a chief material and subjecting the material to casting, etc. The clogging of the nozzle in low-temp. casting is made hard to generate and the resistance to spalling and erosion is provided to the nozzle by using such silica refractories. Various effects including the economization of energy and the production of the cast steel having decreased structure segregation are attained by the low-temp. casting.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a casting nozzle used for low-temperature casting of molten steel.

(Prior Art) In continuous steel casting, casting nozzles are used for the purpose of preventing oxidation and turbulence of molten steel.

The material of the casting nozzle is, for example, Japanese Patent Publication No. 48-28254.
As seen in Japanese Patent Publication No. 54-85175, alumina is made by combining alumina and carbon, and further adding silica, silicon carbide, metal powder, etc. as necessary.
Carbonaceous materials are mainly used.

In the casting process, the temperature of molten steel drops significantly, so the tapping temperature of the converter must be kept high. However, this increase in the temperature of molten steel not only shortens the life of the refractory linings of converters and degassing equipment, but is also unfavorable from the standpoint of energy conservation. Therefore, recently, attempts have been made to perform casting at a low temperature, so-called low-temperature casting.

Furthermore, this low-temperature casting has the effect of producing cast steel with less structural segregation.

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0 Problems to be Solved by the Invention) + 1 -"'However, when conventional casting nozzles are used for low-temperature casting, the nozzle holes can become clogged early due to solidification of molten steel, adhesion of alumina precipitated from molten steel, etc. do.

This seems to be because the material of the casting nozzle has high thermal conductivity, which lowers the temperature of the molten steel.

A method has also been proposed in which the blockages in the holes are dissolved and removed by spraying oxygen on them, but the high temperatures generated during this process tend to damage the refractory structure. In addition, it takes time to dissolve and remove the
There is a problem in that the operating rate of the casting process decreases.

Therefore, there is a strong demand for a casting nozzle made of a material that does not block the nozzle even when used in low-temperature casting.

(Means for Solving the Problems) The present invention provides a nozzle for casting alumina-carbonaceous material, characterized in that a molten siliceous refractory is interposed between an outer peripheral part and an inner peripheral part. This is a casting nozzle.

The figure shows a cross-sectional structure of an embodiment of the present invention, in which a siliceous refractory 3 is interposed between an outer peripheral part 1 and an inner peripheral part 2 of an alumina-carbonaceous cast nozzle.

The materials of the alumina-carbonaceous refractories constituting the outer peripheral part 1 and the inner peripheral part 2 are not particularly different from conventional ones. That is,
As the alumina, for example, a sintered crystal or an electric fusion product having a purity of 9QwL% or more is used. Carbon is, for example, one or more types selected from phosphorous graphite, globular graphite, electrode scrap, pitch coke, carbon black, and the like. The proportion of carbon is 5~
4Qwl,% is preferred. The proportion of alumina is the remainder.

In addition, appropriate amounts of silica, silicon carbide, silicon nitride, boron carbide, sialon, metal powder, fibers, etc. may be added as in the prior art.

Cool pitch,
A binder such as phenol resin or polyvinyl alcohol is added, and after kneading, it is molded using an isostatic press. Firing is performed in a reducing atmosphere at a temperature of around 1000°C.

On the other hand, the siliceous refractory 8 is, for example, fused silica.

It is preferable that the main material is silica, feldspar, etc., and each joint surface of 3 is joined by mortar or the like by casting or the like. The thickness of the fused siliceous refractory 3 is appropriately determined depending on the thickness of the casting nozzle, etc., and is, for example, 3 to 10 ff, although it is not limited in any way.

(Function) Siliceous refractories are materials with lower thermal conductivity than alumina-graphite refractories. However, it is inferior in spalling resistance and erosion resistance. In the present invention, a siliceous refractory is covered with an alumina-carbonaceous refractory, so that thermal shock of the siliceous refractory is alleviated and contact with molten steel is avoided. Therefore, the casting nozzle of the present invention has the spalling resistance and erosion resistance of an alumina-carbon refractory, and also has high thermal conductivity due to the presence of the fused siliceous refractory.

-1 If you simply want to increase the thermal conductivity, it is possible to use ceramic fibers instead of siliceous refractories, but ceramic fibers have cushioning properties that reduce the strength of the nozzle. . Additionally, when a crack occurs in the nozzle, the Cera E7 Kufai bar has the disadvantage that molten steel easily enters the nozzle.

(Example) Examples of the present invention and comparative examples thereof are shown below.

In addition, the dimensions of the casting nozzle on each side are all inner diameters of 70 mm.
It is φ x outer diameter 130MIRφ x length 800 mm.

Example 1 A large siliceous material mainly composed of fused silica was interposed in the alumina-carbonaceous material containing 3 Qwt% of phosphorous graphite as a carbon source at approximately the center in the thickness direction of the nozzle. The thickness of the silica-based large-sized material was 10 mm.

Example 2 A siliceous refractory having a thickness of 1511M was interposed in an alumina-carbonaceous body. Other conditions were the same as in Example 1.

Comparative Example 1 The entire structure was made of an alumina-carbonaceous refractory containing 3QwL% of phosphorous graphite as a carbon source.

Comparative Example 2 The outer periphery was made of siliceous refractory mainly composed of fused silica (20 m thick)
II), and phosphorous graphite 3QwL is used as the carbon source in the inner periphery.
% alumina-carbonaceous refractory.

The test results for each side are shown in the table below.

*1: After heating in an electric furnace at 1500'C for 20 minutes, cooling with water, repeating this process and measuring the number of times until the nozzle snaps. The higher the number of times, the more resistant the resident is to spalling.

*2: Measure the maximum erosion damage dimension after being immersed in molten steel for 4 hours.

*3: It was actually used as a casting nozzle to connect the tundish and the mold, and the number of charges until the nozzle became clogged was measured. Note that the time required for charging was approximately 30 minutes.

(Effects) As is clear from the results of the examples shown in the table, the casting nozzle of the present invention is less likely to cause nozzle clogging during low-temperature casting, and has both spalling resistance and erosion resistance.

Low-temperature casting has various effects such as extending the life of the furnace lining refractory, saving energy, and producing cast steel with less structural segregation due to the lowering of the molten steel temperature.

Therefore, although the immersion nozzle has been shown to be effective at performing low-temperature casting, it goes without saying that the present invention can also be applied to a long nozzle that connects the ladle and the tamp push.

[Brief explanation of drawings]

The figure shows a longitudinal sectional view of a nozzle according to an embodiment of the present invention. l...Outer peripheral part 2 made of alumina-carbonaceous refractory...
・Inner peripheral part 3 made of alumina-carbonaceous refractory...silica-based refractory

Claims (1)

[Claims] A nozzle for low-temperature casting of molten steel, characterized in that a siliceous refractory is interposed between an outer peripheral part and an inner peripheral part in the alumina-carbonaceous casting nozzle.