JPS59107978A - High solubility resistance casting nozzle for horizontal continuous 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 for horizontal continuous casting that has excellent erosion resistance.

In recent years, instead of the vertical continuous casting method in which slabs are pulled downward from the bottom of a mold placed directly below the tundish, the method has been replaced by a method in which slabs are pulled horizontally from a mold placed horizontally at the bottom of the side wall of the tundish. The horizontal continuous casting method is being put into practical use because the equipment cost is lower than that of the vertical continuous casting method.

The structure of the connecting portion between the tundish and the mold of a horizontal continuous casting machine for carrying out the horizontal continuous casting method described above will be explained with reference to FIG.

In Fig. 1, 1 is a tongue tissue 7 unit, 2 is a front nozzle horizontally attached to the lower side wall of the tongue tissue l, 3 is a mold horizontally attached to the front nozzle 2 via a casting nozzle to be described later, and 4 is a casting nozzle.

The casting nozzle 4 includes a feed nozzle 5 horizontally attached to the tip of the front nozzle 2, and a break ring 6 interposed between the feed nozzle 5 and the mold 3.

The molten steel contained in the tundish I is cast into a water-cooled mold 3 through a front nozzle 2 and a casting nozzle 4, where it is cooled and becomes an unsolidified slab. The unsolidified slab is intermittently pulled out from the mold 3 in the water direction.

The casting nozzle 4 receives a large thermal shock because it comes into direct contact with molten steel. To prevent this, the casting nozzle was replaced with silicon nitride (
It is considered that silicon nitride sintered bodies may be manufactured using a sintered body of Si, 104 ), but although silicon nitride sintered bodies have excellent thermal shock resistance, they are inferior in erosion resistance.

Erosion damage of casting nozzles mainly occurs when casting is performed for a long time or when high-oxygen steel with a high concentration of dissolved oxygen is cast.

The cause of melting damage of the queen casting nozzle will be explained below.

(1) About melting loss during long-time casting. Generally, the dissolved AQ concentration in molten steel that is continuously cast is:

Since it is 0.01 to 0.02%, the dissolved oxygen in the molten steel determined by this is 3 to s ppm. Therefore.

Erosion damage of Si and N4 cast nozzles due to oxygen in steel hardly occurs, and the melting loss of cast nozzles is mainly due to the Sj and Sl of N4 that make up the @-made nozzle dissolving into the steel. happen.

Although some of the nitrogen in Si, N4 dissolves in the steel, most of it becomes nitrogen gas and adheres to the surface of the casting nozzle in the form of bubbles. This prevents the molten steel from directly contacting the surface of the casting nozzle to some extent, so the erosion rate of the -Si3N4 casting nozzle is slower than that of the +Si casting nozzle. However, when casting is carried out for a long time, the sl in 5i31J4 melts into the steel, albeit gradually, as described above, and the casting nozzle is damaged by melting.

(2) About erosion when high oxygen steel is cast.

When the dissolved oxygen concentration in steel is 60 or more, such as stainless steel, etc.
When the content is as high as 100 ppm, in addition to the melting loss described in (1), melting loss due to dissolved oxygen in the steel is added.

That is, when Si in 513N4 reacts with dissolved oxygen in steel, SiO gas is generated, and this gas escapes to the outside before becoming 5102. For this reason, Si3N,' is melted away.

From the above-mentioned viewpoints, this invention has the advantage of being effective even when casting for a long time or quickly, even when casting high-oxygen steel.
``7, ,] 2.-1.-1., - To provide a casting nozzle that is resistant to melting and damage, comprising silicon powder in the range of -20 to 90 weight factor as a raw material, and 1 to 2.
Aluminum powder within the range of 0 weight cake, and +A', 203, Zr within the range of 2 to 60 weight candy
O2, Y2O3, Cr2O3, Tx02, M2O.

It is characterized in that it is formed by sintering a cast nozzle molded body made of at least one oxide powder of Co0-1 in a nitrogen-containing atmosphere.

Next, the reasons for limiting the components in this invention will be explained.

The reason why the ratio of silicon powder as a raw material is set to 20 to 90% by weight is to maintain the strength of the nozzle when the molded body of the cast nozzle is molded.

+ AE203, ZrO2, Y2O as raw materials
3, ar2o, .

The ratio of at least one oxide powder of TlO2, MIIO, C, O, etc. is 2 to 60M and Ae
The reason why the weight ratio of the powder was set from 1 to 20 was due to the i of the casting nozzle.
fj;I This is to improve the melting resistance. That is, the purpose is to manufacture a casting nozzle that is not easily damaged by melting even when casting for a long time or during casting of high oxygen steel. This will be explained in more detail.

First, prevention of melting damage during long-term casting will be explained.

31. In addition to N4, oxides 1 that are difficult to dissolve in molten steel, such as Af! When a casting nozzle containing 2Ch is used, 81 in the surface layer of the casting nozzle is dissolved into the molten steel during casting, thereby forming a layer of sintered M2O, that is, a protective layer, on the surface layer of the nozzle. With this protective layer.

Dissolution of Si and N can be prevented. Said AI!
The 20° layer is easily formed due to the AQ added as a raw material. This is -A(! is nitrided and becomes AQN.

This is because the chemical change when this 80N changes into AQ, ..., O, during casting is extremely active.

The oxide must not only be difficult to dissolve in molten steel, but also must be a compound that is not latent by the components in the steel and is stable at an oxygen partial pressure that is in equilibrium with dissolved oxygen. Therefore, the above-mentioned oxides are used. For example, in molten steel with dissolved oxygen of 5 ppm, At! 20.
- When immersed in Al, the saturated solution of Al was 5 ppm and hardly dissolved.

In Zr (12, the saturation solubility of Zr is 0.04 p
It's so boring that it's almost impossible to understand it.

Next, regarding prevention of erosion when high oxygen steel is cast,
I will clarify.

In addition to Si and N, ΔQ2o, which is difficult to dissolve in common,
When a casting nozzle containing an oxide such as ZrO2 or the like is used, the protective layer is formed on the surface layer of the casting nozzle for the same reason as described above. For this reason, even if high-oxygen steel is made of V), melting damage of the υ1-made nozzle can be prevented. Other than this.

The following reasons also prevent melting and damage of the casting nozzle. That is, when the amount of dissolved oxygen in molten steel increases, 1, for example,
The saturation solubility of ΔF,, Zr decreases and these oxides become less soluble. These oxides present on the surface and shoulders of the casting nozzle become a nucleus for the SiO gas generated when Si and N4 are oxidized to reach SiO□ on the surface layer of the casting nozzle, and Sj on the surface layer of the casting nozzle. , 02 are more likely to be generated. Therefore, this 5i02 is mixed in the protective layer and prevents melting and damage of the casting nozzle.

'Next, embodiments of the present invention will be described.

The starting materials shown in Table 1 were adjusted to a predetermined particle size.

After adding an appropriate amount of a binder such as PVA and kneading, the mixture was dried to obtain a raw material for break ring. This raw material was molded into a break ring shape using a press machine using a rubber press and a mold, and then the molded break ring was prefired in an Ar atmosphere at 1200° C. to remove the binder and the like. Next, the pre-fired break ring was heated to 1000°C.
A break ring (product of the present invention) made of a silicon nitride composite sintered body was manufactured by firing in a combustible gas atmosphere.

This break ring is installed between the foot nozzle of a horizontal continuous casting machine and the mold, and a slab is cast by casting carbon steel with the components shown in Table 2. We investigated the volume of the ring. These results are shown in Table 3 together with the results obtained when a break ring manufactured in the same manner as described above was used except that the starting material component was 81 only.

The break ring erosion index is expressed as D mm (break ring erosion amount) ÷ slab length m) x 100, and the smaller the value, the smaller the erosion loss amount. Table 6 shows the results when stainless steel with the same composition as above was cast.
The results are shown when high chromium steel with the components shown in the table is cast.

As is clear from Table 3, Table 5, and Table 7, the break ring of the present invention does not have any grooves even after long-time casting, and even when high-oxygen steel is cast, the break ring made only of Si It can be seen that the amount of erosion loss is extremely small compared to the above.

As explained above, the casting nozzle of the present invention.

Even if you do V1 casting for a long time, it will only last for one year, and even if you cast high oxygen steel, it will be extremely resistant to melting and damage, which will always bring about extremely useful effects.

[Brief explanation of drawings]

The drawing is a cross-sectional view showing the structure of the connecting portion between the tongue tissue and the mold. In the drawing, ■... Tan tissue 2... Front nozzle 3... Mold
4... Casting nozzle 5... Feed nozzle 6.
...Brake Ring Applicant Nippon Kokan Co., Ltd. Applicant Shinagawa Shirorenga Co., Ltd. Furito Natsuo Shioya (and 2 others)

Claims (1)

[Claims] As raw materials, silicon powder within the range of 20 to 90% by weight, aluminum powder within the range of 1 to 20% by weight, and +A within the range of 2 to 60% by weight. , (t
203. ZrO2, Y2O3, Cr2O3, TiO2
,MyO. It is characterized by being formed by nitriding and sintering a cast nozzle molded body made of at least one oxide powder of CcL〇-I in a nitrogen-containing atmosphere. A casting nozzle for horizontal continuous casting with excellent melting and d properties.