JPS6148485A - Refractories for flowing molten metal - 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] [Industrial Field of Application] The present invention has a flow rate of molten metal of 2I! 11! This invention relates to refractories such as plate bricks that are most suitable for use in i-necks, especially sliding nozzle devices (sliding devices).

[Prior Art] At present, refractories of this type mainly used for processing molten steel include A1203-C series and Al2O3-5ICh series, but they have not yet been able to sufficiently withstand melting damage of molten steel. For this reason, the inventors of the present invention previously proposed the use of ZrB2 as a material for this purpose, and achieved a certain degree of improved evaluation.

[Problems to be solved by the invention] It is true that the method using ZrB2 is effective, and it is known that it will dramatically extend the life of this type of plate.
It has been found that ZrB2 has an extremely high #adhesiveness, and therefore has the disadvantage of causing clogging in some cases when used for a long time. This drawback can be solved by finishing the ZrB2 surface with a mirror finish, but this will require a large amount of cost and may hinder its versatility.Also, ZrB2 does not necessarily have sufficient spall resistance (ΔT 250℃)
For this reason, it is necessary to preheat sufficiently, and at this time, the surface may be partly oxidized and an oxide layer is formed, which may accelerate clogging and may even cause damage due to thermal spalling. I understand.

Means for Solving Problem c] The present invention was discovered as a solution to the above problems, and improves resistance to thermal spalling by forming a composite in which BN is added to ZrB2,
At the same time, it is possible to appropriately adjust the dispersibility of the molten metal at the molten steel contact surface.

That is, in the present invention, the surface that comes into contact with the flowing molten metal is coated with Zr.
The gist of the present invention is a refractory for molten metal distribution, which is characterized by being formed from a B2-BN composite sintered body.

For the flow control port of the present invention such as plate bricks for sliding devices (
There are various types of gastric materials for distribution, but at least the surface through which molten metal such as molten steel passes and comes into contact with the molten steel, especially those with distribution holes such as plate bricks, the inner surface of the distribution holes, i.e. 1. The surface facing the metal is ZrB
In other words, the object of the present invention can be achieved to a certain extent if at least a part of such a surface is made of ZrB2-BN.

Specifically, ZrB2-88 surface (ZrB2-B
The formation of the N-containing layer can be roughly divided into the following two types.

One is directly the refractory itself, most of which is ZrB2-BN.
The main molded body itself is usually made of a different material (of course, it may be ZrB2-BN). , is a layered body in which a ZrB2-BN containing layer is formed by an appropriate means on at least the surface thereof which becomes a flow path in contact with the molten steel flow.

To explain these in more detail, the following can be suitably used as the former.

ZrB2-BN sintered body This is made by ZrB2 and BN powder or sintered body.
It is obtained by molding raw materials that can become ZrB2 and BN, sintering material, reducing material, etc., and then sintering them at high temperature and high pressure in a reducing atmosphere.

For example, a predetermined portion of a mixed powder of ZrB2 and BN is preformed using an organic resin as a binder, and this is heated at a temperature of 20°C.
It was obtained by hot pressing at a temperature of 00° C. or higher and a pressure of 500 kg/en1 or higher.

In addition, when it is difficult to obtain these ZrB2-BN molded products as an integral product due to the size, shape, etc. of the refractory,
It is also effective to obtain it as a divided partial molded body and use this as at least the most necessary part of the refractory or as a combination.

As the latter method for forming the surface of the ZrB2-B)l-based sintered body, the following can be suitably used.

That is, the surface of the molded body is coated with ZrB2-BN paste by coating, spraying, etc., or ZrB2-BN
By immersing the molded body in a solid solution, the pores and surface of the molded body are impregnated and coated with the liquid, and then dried and fired.
This can be obtained by forming an rB2-BN layer. Plasma coating can also be used if a stronger coating is desired.

In the case of the latter method, it is also possible to form the ZrB2-BN layer only at the necessary location, that is, at least on the surface near the inlet of the molten steel flow path, which may be economical depending on the purpose. However, it is preferable to apply it to the entire surface of the molded article.

Among these refractories formed of ZrB2-BN or ZrB2-BN-containing layers, the one most suitable for the purpose of use of the present invention has the most substantial effect in improving durability such as corrosion resistance and abrasion resistance. However, in consideration of practical effects and cost, it is obtained by coating, impregnating, or spraying onto a plate or a molded body therefor.

In such a refractory of the present invention, ZrB2 and B
The blending ratio of N as a sintered body is in weight%, and the former is 85~
60%, the latter 5-40%, preferably the former 90%
~70%, the latter 10-30%.

This is because if the BN component is too small, corrosion resistance is sufficient, but
This is because the spalling resistance for this type of use will be insufficient, and if it is too large, the problem will arise that although the spalling resistance is good, the corrosion resistance is insufficient.

In the sintered body of the present invention, components other than ZrB2 and BN components are intended to be contained in as small a quantity as possible, but they may not be included to the extent that the objects and effects of the present invention are not substantially impaired. For example, some of the ZrB2 may be replaced by other borides such as Ti82.

It is possible to substitute other carbides such as 2rC. In any case, the content of ZrB2 and BN component is 9
It is desirable that it is 0% or more.

〔Effect of the invention〕

As described above, the present invention has successfully compensated for the insufficiency of ZrB2 by adding BN, and when used as a refractory for molten metal distribution, (1) there is no fear of clogging. (2) No more damage due to thermal shock resistance.

, (3) xq/melting fi 4500T or more 1 is 1
It has a corrosion resistance of 961 minutes. (4) It is excellent in that it does not require preheating or its temperature can be significantly lowered, and its practical value is high.Therefore, the optimum use of the refractory of the present invention is as a sliding device. It is a sliding plate-shaped refractory with flow holes, and is also used as a nozzle for continuous casting of molten steel, etc.

[Example] ZrB2 and BN powder finely pulverized to 1 lm or less were placed in a ball mill at a predetermined ratio, and mixed and pulverized for 48 hours. The mixed and pulverized fine powder has a maximum particle size of 0.5w or less. This mixed powder is dried, crushed, and granulated if necessary. These crushed powders or granulated powders are filled into a 5011IIφX 50mmH sample holder and hot pressed.

The hot press condition was to hold at 2000° C. for 1 hour under a pressure of 300 to 400 kg/−. After cooling, the sintered body was taken out from the sample holder and processed into the required size (a diamond processing machine and an electric discharge machine were used) to prepare a test sample.

Spalling resistance of various samples obtained in this way,
#The measurement results of dispersibility and bending strength are shown in FIGS. 1, 2, and 3.

Figure z1: A sintered body cut out into a size of 4 mm width x 3 mm thickness x 38 m+a length was placed in a furnace kept at a predetermined temperature and held there for 30 minutes, then dropped into water to be rapidly cooled. The bending strength of this sample was measured in accordance with JIS R1601, and was expressed as ΔT of the furnace at which the degree of bending decreased.

Figure 2: A sample of IOX IOX tom+o was placed in a crucible together with a steel piece in a high frequency induction furnace at 1500°C x 1.
Dissolved for hours. After removal, the reduction in 1OIIlrn dimension was measured, and this was divided by 2 to determine the amount of erosion.

Figure 3: Shows values measured in accordance with JIS R11301.

The sintered body (B
When applied to a tundish nozzle (N m 10, 20.30%), it was possible to maintain extremely stable flow rate regulation for a long time.

On the other hand, it was found that the i:r82 sintered body causes blockage due to the adhesion of slag, and the BN-only sintered body causes the nozzle diameter to expand, making it difficult to adjust the flow rate. I understand.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the relationship between BN firefly and ΔT of the refractory of the present invention. FIG. 2 is an explanatory diagram showing the relationship between the amount of BN and the amount of erosion. FIG. 3 is an explanatory diagram similarly showing the relationship between the amount of BN and the bending strength. Fig. 1 BN amount (%) Fig. 2 OTo 20 30 40 50 Fig. 3 OTo 20 30 40 50 60
70 60 90 to. BN amount (%)

Claims (1)

[Claims] 1. The surface that comes into contact with the flowing molten metal is made of ZrB_2-B.
A molten metal flow refractory characterized by being formed from an N-based composite sintered body. 2. Refractory is ZrB_295-60% by weight, BN5
The refractory according to claim 1, having a composition of .about.40%.