JPS58120569A - Nozzle for casting - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a casting nozzle such as a submerged nozzle used for continuous casting of molten metal.

Conventionally, the immersion nozzle used to continuously pour molten metal into a mold mainly uses molten stone.

It is made of a material such as alumina-graphite.

However, the immersion nozzle made of molten stone is easily corroded by molten metal and damaged by melting, so if silica captured in steel becomes non-metallic inclusions, it will not affect the quality of the steel and will have a large negative impact, as well as quantitative It is difficult to perform casting operations continuously.

On the other hand, when an alumina-graphite immersion nozzle is used for casting aluminum-killed steel, the casting operation must be carried out continuously because Al2 etc. tend to precipitate and adhere to the nozzle and clog the nozzle. It is difficult to do so. As a countermeasure to this problem, a method has been used to prevent alumina from adhering by blowing alpune gas or the like into the immersion nozzle, but it cannot be said that sufficient results have been achieved.

The present invention was made in view of the above circumstances, and it is an object of the present invention to provide a casting nozzle that prevents nozzle clogging and eliminates gaps caused by non-metallic inclusions caused by melting loss.

In other words, the casting nozzle of the present invention is based on the weight ratio! Tanesia 35~F01 Graphite 5~40T and neutral refractory material 25~
55%.

As described above, the casting nozzle of the present invention is made by adding a neutral refractory material as a third component to magnesia graphite. When compared with conventional aluminized graphite casting nozzles, it has the following advantages.

(1) Compared to alumina, magnesia has slightly lower corrosion resistance against steel, so it is gradually eroded during casting, and it is difficult for aluminum buildup to adhere to it.

(2) Even if magnesia were to melt and become trapped in the steel and become non-metallic inclusions, the negative effect on the quality of the steel would be much less.

(3) At temperatures around 1,500℃, magnesia sinters when precipitates in steel form, making it difficult for the nozzle to close due to alumina adhesion.・Change the main aggregate of casting nozzles from alumina to magnesia. If you replace it, you will have the advantages mentioned above, but
Magnesia-graphite alone has a large coefficient of thermal expansion and poor spalling resistance, so it is not used in immersion nozzles that are subject to severe thermal shock9. The present invention improves spalling resistance and controls corrosion resistance by adding a neutral refractory material as a third component to magnesia-graphite. In the present invention, the mixing ratio of magnesia is 35 to 70%. If the temperature is less than 35 inches, magnesia will be added and the effect will be small and it will be difficult to prevent the nozzle from freezing.
If it exceeds 0%, the thermal expansion coefficient of the entire nozzle increases,
This is because the spalling resistance decreases.

9. The reason why the mixing ratio of graphite is set to 5 to 40 is that if it is less than 5, the spalling resistance is poor and it becomes easy to wet the steel, resulting in an altered layer. Corrosion resistance is extremely low.

It is a downward rounding.

The neutral refractory material improves the spalling resistance of the magnetic graphite and controls the corrosion resistance, and a material with a small coefficient of thermal expansion and high corrosion resistance is selected. However, since magnesia is basic, acidic refractory materials such as fused silica are not suitable, even if the coefficient of thermal expansion is small. In the present invention, alumina, chromium oxide, mullite, sillimanite,
One or two of oxide refractory materials such as spinel or non-oxide refractory materials such as silicon carbide, silicon nitride, boron nitride, etc.
◇The mixing ratio varies depending on the substances to be mixed, but it must be between 25 and 55%.

This is because if it is less than 25%, the effect of improving spalling resistance is small, and if it exceeds 55%, the advantages of magnesia-graphite are lost.

In the present invention, an organic binder (phenol resin, tarbi, chi, etc.) is used for molding the above three components. This is because when an inorganic binder (clay, water, etc.) is used during firing after forming, the coefficient of thermal expansion of the entire refractory depends on the compound produced by sintering the binder and aggregate particles. This is because refractories containing magnesia as a main component usually have a large coefficient of thermal expansion, so spalling resistance becomes a problem.

The present invention will be explained in detail below.

Mixing was carried out by adding phenol resin or tar pitch to the three types of raw material powders at the mixing ratios shown in the table below, respectively, at the addition rates shown in the table below. Next, a molding pressure of 1.0 to 1.5 t
It was molded into a nozzle shape by a rubber press method under the conditions of /a112, dried and fired at 1100 to 1200°C to obtain an immersion nozzle for continuous casting. It has a two-layer structure with refractory material.

The physical properties of the above three continuous casting immersion nozzles were investigated and the results shown in the table below were obtained. The sling test in the table below was performed by repeatedly heating the immersion nozzle to 1400 tons and then cooling it with water twice, and the erosion rate was determined by steel type 8841.
These are the results of the erosion test using the nine immersion method.

In addition, Comparative Example 1 in the table below is a conventional alumina-graphite immersion nozzle for continuous cementing, and Comparative Example 2 has a low mixing ratio of Fi neutral refractory material, so it has a large coefficient of thermal expansion and good spalling resistance. Comparative Example 3 contains silica as the third component, and has a high coefficient of thermal expansion, making it difficult to resist spalling. It is of inferior quality.

As is clear from the above table, all Examples 1 to 3 have better spalling resistance than Comparative Examples 2 and 3.

In addition, in continuous casting of aluminum killed steel, the alumina-graphite immersion nozzle of Comparative Example 1 caused a nozzle gap to occur in about 2 hours and became unusable, whereas Examples
All of the immersion nozzles were able to be used for a long time. In particular, the immersion nozzle of Example 2 could be used for about 4 hours. Furthermore, the quality of the steel obtained by continuous casting using the immersion nozzles of Examples 1 to 3 was better than the quality of the steel obtained using the conventional immersion nozzle.

Note that the casting nozzle of the present invention is not limited to the one in which the outer line part is made of other materials such as Zilfair graphite and has a two-layer structure as in the above embodiment, but it can also be used with only the three components of the present invention. Alternatively, the main body may be made of a material with good corrosion resistance, and the inner peripheral surface may be made of the three components of the present invention.As detailed above, according to the present invention, nozzle clogging is prevented. Furthermore, it is possible to provide a casting nozzle that eliminates the problem of nonmetallic inclusions caused by melting damage.

Claims (2)

[Claims] (1) In terms of weight ratio! Gnesia 35-701, graphite 5-4
A casting nozzle made of 〇- and neutral refractory material 25-55-. (2) Neutral fire-resistant materials are alumina and chromium oxide. Mullite, sillimanite, spinel, silicon carbide. The casting nozzle according to claim 1, characterized in that the material is one or more of silicon nitride and boron nitride.