JPH0343232B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a refractory for sliding parts, such as plate bricks, which are most suitable for use in sliding nozzle devices (sliding devices) such as molten metal flow rate adjustment ports. The refractory that comes into contact with the molten metal in the sliding flow rate adjustment device is made of two plate bricks that have an outlet at the bottom of the molten metal container such as molten steel, and holes for the molten metal to flow out at the bottom, that is, the upper side is moved. It consists of a fixed plate brick, which is not attached to the fixed plate, and a lower sliding plate brick, which is in watertight contact with the fixed plate and slides in the horizontal direction to control flow rate adjustment such as outflow and stoppage of molten metal. There are various problems with sliding flow rate adjustment devices, but
The durability of this type of refractory built into equipment is the most important of these, and various studies have been conducted on how to reduce the frequency of replacing the refractory. The main causes of replacement of refractories in this type of application are abrasion of the refractory due to the passage of molten metal and erosion of the refractory due to enlargement of pore diameter due to reaction with the molten metal. These types of refractories currently mainly used in molten steel processing include Al ₂ O ₃ -C type and Al ₂ O ₃ -
Although it is a SiO ₂ type material, it is not sufficiently resistant to corrosion damage caused by molten steel. The present invention was discovered as a result of various studies in view of these points, and it not only has excellent durability against erosion caused by molten steel, etc., but also has a sliding surface that is further necessary for this type of refractory. We have succeeded in providing a refractory with sufficient accuracy and impact (thermal and mechanical) resistance. That is, the present invention significantly improves problems such as erosion in movable refractories for molten metal flow control ports such as sliding plate bricks by selecting ZrB ₂ (zirconium diboride) refractories as the material. It was. The refractory for the flow control port of the present invention, such as a plate brick for a sliding flow control device, can be in various forms. For those with communication holes, it is necessary that the inner surface of the communication hole, that is, the surface facing the molten metal, be made of ZrB ₂ material.In other words, at least a part of such surface must be made of ZrB ₂ material refractory. As long as it is suitable, the object of the present invention can be achieved to a certain extent. Specifically, the ZrB ₂ surface (ZrB ₂ containing layer) according to the present invention
The formation of can be roughly divided into the following two types. One is directly the refractory itself, mostly ZrB ₂
The main molded product itself is usually made of a different material (for example, _{Al 2 O 3} -C). refractories), and at least the part that becomes the flow path that comes into contact with the molten steel flow.
This is a layered structure in which a ZrB ₂ -containing layer is formed by an appropriate method. To explain these in more detail, the following can be used as the former. 1 ZrB _2- quality sintered body This is made by molding ZrB _2- quality powder or raw materials that can become ZrB ₂ during sintering, sintering material, reducing agent, etc., and then sintering at high temperature and high pressure in a reducing atmosphere. can get. For example, ZrO _binary powder is preformed with an organic resin as a binder, and this is then heated at a temperature of 2000°C or higher and under pressure.
It was obtained by hot pressing at a pressure of 500 kg/cm ² or more. Furthermore, if a few percent of powder such as SiC or B ₄ C is added to ZrB ₂ powder as a sintering aid, sintering can be performed at 2000°C without hot pressing. 2 _ZrB binary melted and resolidified product A predetermined amount of refractory raw material whose main component crystals become ZrB ₂ by melting and resolidification is heated in an electric arc furnace using a graphite electrode, and after resolidification, a predetermined shape is obtained. It can be obtained by molding into parts having holes or parts constituting them. For example, in weight%, B ₂ O ₃ 40%, ZrO ₂ 40%,
Powder raw material consisting of 20% C is placed in an electric arc furnace.
Examples include crystals made of 90% or more ZrB ₂ that are obtained by thermally melting at a high temperature of 2700°C or higher, then slowly cooling it to room temperature. Among such sintered bodies or melted and resolidified bodies, those containing 90% or more of ZrB ₂ by weight are suitable for the present invention, but these have a certain effect from the purpose of the present invention. As for ZrB, it is necessary to contain at least 5% or more as _two components, and it is usually better to contain 50% or more. In addition, when the content of the ZrB _two components is relatively small, it is desirable that the other components be those that can take advantage of the characteristics of the ZrB _two components as much as possible.
In such a case, ZrC, TiC, etc. are suitable as the composite component. In addition, when it is difficult to obtain these ZrB _two- component molded bodies as an integral body due to the size, shape, etc. of the refractory, it is possible to obtain them as divided partial molded bodies and combine them with at least the most necessary part of the refractory. It is also effective to use it as a refractory. The following methods can be used to form the _ZrB2 surface layer. That is, the surface of the molded body is coated with ZrB _binary powder paste by coating or spraying, or
A refractory molded body is immersed in a suspension of ZrB _binary powder to impregnate and coat the pores and surface of the molded body with the liquid, and then dried and fired to form a _ZrB binary layer. It will be done. The composition of ZrB ₂ powder is, for example, ZrB ₂ powder 90
%3Al powder + Si powder + phenol resin 10% can be used. Firing is performed, for example, at 1000° C. or higher in a graphite sheath or in a strongly reducing atmosphere furnace to form a strong coating on the surface of the refractory molded product. If it is difficult to bake the film and impregnation is preferable, ZrB _binary fine powder is suspended in a liquid and impregnated into an air-permeable molded body in a vacuum container. Plasma coating can also be used to form a stronger coating. In addition, in the case of this method of forming a film, this
It is possible to form the _ZrB2- containing layer only at the necessary location, that is, at least on the surface near the inlet part of the flow path of molten steel, etc., which is economical depending on the purpose, but it is preferable to form Apply to all surfaces of the body that come into contact with molten metal. Among these refractories formed with ZrB ₂ or ZrB _2- containing layers, the one most suitable for the purpose of use of the present invention is the heat-fused refractory, which has the most substantial effect in improving durability such as corrosion resistance and abrasion resistance. It is a re-solidified product, and on the other hand, in consideration of practical effects and cost, it is obtained by coating, impregnating, or spraying on molded bodies for refractories for molten metal flow control ports, such as plates. As a result, the refractory of the present invention has almost no or no reaction with molten steel, etc., and has an extremely high hardness (possible Mohs height of 8 or higher), for example, high-temperature bending strength of 1.0 Kg/mm at 1670°C. ² , and the characteristics of having wear resistance against molten steel flow paths are exactly suitable for the purpose of the present invention. For example, compared to conventional Al ₂ O ₃ -C plate bricks, it is generally extremely easy to achieve an improvement of 20% or more (see Table 1), and specifically, the lifespan of plate bricks can be increased by several times the number of uses. Depending on the type and scale of the molten steel, further improvements can be made, and its industrial value is enormous, including the significant reduction in replacement work that results from this. be.

【table】

[Table] For the erosion test, a 30φ x 60 sample rod was sprayed into molten steel and slag, and the dimensional changes after erosion were compared. (The corrosion resistance index is the amount of corrosion of the sample
(shown as the ratio of corrosion resistance when

Claims (1)

[Scope of Claims] 1. A refractory for a molten metal flow rate adjustment port, characterized in that a portion that comes into contact with molten metal is formed of ZrB ₂ or a ZrB ₂ -containing layer. 2. A patent claim in which the refractory is a plate brick for use in a sliding flow rate regulating device, which has a molten metal flow hole, and at least the inner surface of the flow hole is formed of ZrB ₂ or a layer containing ZrB ₂ A refractory for a molten metal flow rate adjustment port according to item 1.