JPH11116323A - Carbon-containing refractory product and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a carbon-contg. refractory product suitable to molten steel flow control and high in mechanical strength and corrosion resistance by adding an organic binder to a refractory inorganic material comprising a magnesia- based stock, carbonaceous stock and alumina-based stock followed by kneading to mold the resulting blend to a specified shape and then carrying out a baking. SOLUTION: A refractory inorganic material comprising 15-40 wt.% of a magnesia-based stock <=1 mm in particle size, 3-15 wt.% of a carbonaceous stock <=200 mesh in particle size and >=80 wt.% in fixed carbon content selected from flaky graphite, soil-like graphite, petroleum-based pitch, carbon black and organic or inorganic pyrolyzed carbon, and the rest of alumina-based stock >=90 wt.% in Al2 O3 content appropriately adjusted to coarse particle, medium particle and fine particle range, is incorporated with a thermosetting organic binder followed by kneading to mold the resulting blend to a specified shape, for example, to a shape of refractory product for molten metal followed by drying and then baking, using a hot press, in a nonoxidative atmosphere at >=1,700 deg.C, thus obtaining the objective carbon-contg. refractory product.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon-containing refractory and a method for producing the same, and more particularly to a high corrosion-resistant carbon-containing refractory suitable for a slide gate plate and the like and a method for producing the same.

[0002]

2. Description of the Related Art A slide gate plate (hereinafter referred to as an SG plate) formed of a refractory for continuous casting is used as a device for discharging molten metal in a ladle, a tundish, etc., and slides on the SG plate. By doing so, the flow rate of the molten metal is controlled.

[0003] For this reason, refractories used for SG plates are different from ordinary refractories and are required to have very high functions such as spalling resistance and corrosion resistance as well as mechanical strength.

The material of the SG plate has been a high alumina material obtained by adding a mullite material or a sillimanite material based on an alumina material in the past.
The variety of steel types has been diversified, and there is a demand for a further improvement in the number of times of use. Alumina-carbon materials obtained by adding carbon, metal silicon, metal aluminum, and the like to an alumina raw material have become mainstream.

[0005]

Various studies have been made on these alumina-carbon materials to improve their durability. For example, Japanese Patent Publication No. 61-2619 and Japanese Patent Publication No. 61-2620 disclose alumina-carbon materials. Although an SG plate is disclosed in which a zirconia-based material or the like is added to a material as a base, sufficient durability cannot be obtained with respect to a special steel type such as high oxygen steel or calcium-treated steel.

Further, magnesia is the highest melting temperature (MP) among general refractory materials currently used.
(2800 ° C.), and is known to have excellent corrosion resistance to basic slag, and various methods of using magnesia-based raw materials that take advantage of the characteristics of excellent corrosion resistance have been studied.

In a method of manufacturing an SG plate using a magnesia raw material, for example, Japanese Patent Application Laid-Open No. 59-54671,
By adding a magnesia raw material having an adjusted particle size and amount to the alumina raw material, and further lowering the firing temperature of the molded SG plate, spinelization caused by the reaction between the alumina raw material and the magnesia raw material is performed not by firing but by SG.
A method of making the SG plate dense when the plate is used to further improve the durability has been studied.

[0008] However, magnesia has the highest melting temperature and excellent corrosion resistance to basic slag, but has a large coefficient of thermal expansion. During firing, there is a possibility that cracks will occur in the SG plate fired body due to the difference in thermal expansion coefficient between the base material alumina and magnesia.

Therefore, in the conventional production method, the amount of magnesia added is about 10% by weight, as in the case of the refractory disclosed in JP-A-59-54671, and at most 20%.
% By weight, and cannot make use of the excellent corrosion resistance of magnesia.

Further, in the method in which the SG plate is used to form spinel by reacting the magnesia-based raw material and the alumina-based raw material, spinelization proceeds in a portion in contact with molten steel, but does not progress in a portion not in contact with the molten steel. In other words, when the densification proceeds, there is a difference in the expansion rate at the boundary between the part where the spinelization has progressed and the part where the spinelization has not progressed, and cracks may occur. Therefore, it cannot be said that sufficient durability can be obtained.

Therefore, there has been a demand for a high corrosion resistant refractory suitable for controlling the flow rate of molten steel such as a slide gate plate.

The present invention has been made in consideration of the above circumstances, and has as its object to provide a highly corrosion-resistant carbon-containing refractory suitable for controlling the flow rate of molten steel, such as a slide gate plate, and a method of manufacturing the same. .

[0013]

Means for Solving the Problems To achieve the above object, the invention of claim 1 of the present application provides a magnesia raw material 1
5 to 40% by weight, carbonaceous material 3 to 15% by weight, the balance being A
A thermosetting organic binder for binding the refractory inorganic material is added to a refractory inorganic material made of an alumina-based material having a l ₂ O ₃ content of 90% by weight or more, kneaded, and formed into a predetermined shape. The gist is that the body is a carbon-containing refractory characterized in that it is fired by a hot press in a non-oxidizing atmosphere at a temperature of 1700 ° C. or more.

According to a second aspect of the present invention, there is provided a carbon-containing refractory according to the first aspect, characterized in that the molded body has a shape of a refractory for molten metal.

According to a third aspect of the present invention, there is provided a carbon-containing refractory according to the second aspect, wherein the refractory for molten metal is formed in the shape of a slide gate plate.

According to a fourth aspect of the present invention, there is provided a carbon-containing refractory according to the second aspect, wherein the refractory for molten metal is formed in a ring shape.

The invention of claim 5 of the present application is directed to a refractory material comprising a magnesia-based raw material of 15 to 40% by weight, a carbonaceous raw material of 3 to 15% by weight, and a balance comprising an alumina-based raw material having an Al ₂ O ₃ content of 90% by weight or more. A thermosetting organic binder is added to a conductive inorganic material, kneaded, molded into a predetermined shape, dried, and then heated to 1700 in a non-oxidizing atmosphere using a hot press.
The gist of the present invention is to provide a method for producing a carbon-containing refractory characterized by firing at a temperature of not less than ° C.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a carbon-containing refractory according to the present invention and a method for producing the same will be described.

The carbon-containing refractory according to the present invention is composed of a magnesia raw material of 15 to 40% by weight, a carbonaceous raw material of 3 to 40% by weight, and a balance of an alumina raw material having an Al ₂ O ₃ content of 90% by weight or more. A thermosetting organic binder that binds the refractory inorganic material to the refractory inorganic material becomes kneaded, and after being kneaded, a molded body formed into a predetermined shape is dried and then hot-pressed in a non-oxidizing atmosphere at 1700 ° C. or higher. It is manufactured by firing at the temperature described above.

The alumina raw material must be excellent in corrosion resistance and wear resistance in order to fulfill the function of the main aggregate of the SG plate, and the chemical composition of Al ₂ O ₃ is 90% by weight or more. If so, either a sintered product or an electrofused product may be used. If the chemical composition of Al ₂ O ₃ is less than 90% by weight, S
Since it contains many impurities such as i ₂ O, TiO ₂ , and Fe ₂ O ₃ , the corrosion resistance of the SG plate is reduced.

The reason why the blending amount of the magnesia raw material is set to 15 to 40% by weight is that when the amount is less than 15% by weight, a large amount of the magnesia raw material is added to the SG plate by using a hot press which is a feature of the present invention. And it is not possible to provide excellent corrosion resistance, so there is no point in using a hot press. If it exceeds 40% by weight, the coefficient of thermal expansion of the entire SG plate increases, and the spalling resistance of the SG plate decreases. I do.

The above-mentioned alumina raw material is appropriately adjusted to coarse, medium, and fine powder regions so as to obtain a dense packing in order to fulfill the function of the main aggregate of the SG plate. Use the one with a particle size, not the coarse one.

The strength of the magnesia-based material is lower than that of the alumina-based material. When a magnesia-based material having a particle size of 1 mm or more is used, a thermal stress is generated in the SG plate that exceeds the strength of the SG plate, and cracks develop in the matrix. if you did this,
Because the crack propagates linearly in the magnesia particles,
This causes factors such as chipping of the edge of the hole diameter of the SG plate or separation of the sliding surface.

If the amount of the carbonaceous raw material is 3 to 15% by weight, the corrosion resistance becomes insufficient if the amount is less than 3% by weight.
If the content exceeds% by weight, the strength of the SG plate tends to decrease, and the oxidation resistance remarkably deteriorates.

The carbonaceous raw material used in the present invention may be selected from general carbonaceous refractories, such as scale graphite, earthy graphite, petroleum pitch, carbon black, organic or inorganic pyrolytic carbon, and the like. A type or two or more types are selected.

At this time, the amount of fixed carbon is desirably 80% by weight or more in consideration of a decrease in corrosion resistance due to impurities. The particle size of the carbonaceous raw material is 20
It is sufficient that the mesh size is 0 mesh or less.
Desirably, the mesh size is not more than 00 mesh.

After adjusting the particle size of the three components of the alumina raw material, the magnesia raw material and the carbonaceous raw material having the above characteristics,
An organic binder is added and kneaded at room temperature or under heating.

The thermosetting synthetic resin of the organic binder is preferably a phenolic resin from the viewpoint of the amount of fixed carbon and cost.

Next, the compound obtained through the above-described manufacturing process is subjected to, for example, an oil press, a friction press, or in a special case, a rubber press, into a predetermined shape, for example, a refractory for molten metal. It is molded into a shape to make a compact.

Specifically, as shown in FIG. 1, a frame (iron shell) 1 and a three-component raw material, which is filled in the frame 1 and is composed of the above-mentioned alumina-based material, magnesia-based material and carbon-based material, are combined with an organic material. SG plate main body 2 formed by adding and kneading a binder, and through-hole 3 provided in main body 2 for outflow of molten steel.
It can also be used for the SG plate 4 having various types and various nozzles.

Further, as shown in FIG.
Ring 5 used by being inserted into the severely eroded portion of the inner peripheral surface of through hole 3 provided in
Mold into a shape such as

The replacement ring 5 'is used when the SG plate 4 as shown in FIG. 1 is used for the molten steel control operation and melts around the through hole 3 when the SG plate 4 is used for the molten steel control operation. A portion of the through hole 3 is enlarged by cutting and cutting off the portion, and an exchange ring 5 'is inserted into the enlarged through hole 3 and fixed with mortar or the like.
Reuse G plate 4.

After that, the exchange ring 5 'formed into a predetermined shape, for example, a ring shape, is dried, and then fired under pressure and in a non-oxygen atmosphere using a hot press.

The firing temperature in a non-oxygen atmosphere is 1700 ° C.
The above is desirable, and when the temperature is lower than 1700 ° C., the effect of promoting the densification of the refractory is not so much recognized.

For the purpose of further improving the durability, the replacement ring 5 'manufactured as described above may be impregnated with tar or pitch at least once.

In the present invention, besides the above-mentioned compounding raw materials, if necessary, antioxidants and sintering aids which are usually used as additives for SG plates, which are the most suitable applications of the present invention, such as metal oxides and metal A metal compound such as carbide, metal nitride, metal boride, or metal powder may be added.

[0037]

Examples Table 1 shows examples (Examples 1 to 7) of firing at a firing temperature of 1750 ° C. using a hot press, comparative examples (Comparative Examples 1 to 3) of firing in a coke breeze, and hot pressing. And Comparative Examples (Comparative Examples 4 and 5) fired at a firing temperature of 1750 ° C. are shown.

[0038]

[Table 1]

Corrosion resistance test: In the corrosion resistance test, an induction furnace was used, and C (carbon) /
A slag of S (sulfur) = 1.5 was charged, and each sample was immersed for a certain time and then taken out.

The corrosion resistance index was calculated by taking the amount of erosion of Comparative Example 2 as 100
Is an index of the amount of erosion of the other samples when is used. The smaller the index is, the better the corrosion resistance is.

Spalling resistance test: In the spalling resistance test, each sample was put into an electric furnace maintained at 1400 ° C. for 20 minutes, taken out, immediately put into water and rapidly cooled. After repeating this three times, cracks on the sample surface and inside were observed and compared.

Results: Examples 1 to 3 using a hot press
No. 4 was significantly improved in strength as compared with Comparative Examples 2 to 3 in which firing was performed in a conventional coke breeze, and the amount of magnesia could be increased without cracking during firing. No. 4 was able to improve the corrosion resistance.

In Comparative Example 1 using the conventional firing method, cracks were generated during firing when 25% by weight of the magnesia raw material was added.

A large amount of a carbonaceous raw material was added at 18% by weight, and a hot press was performed at a firing temperature of 1750 in the same manner as in each example.
In Comparative Example 4 fired at ℃, no improvement in corrosion resistance was observed as compared with Comparative Example 2 using the conventional firing method.

Further, in Comparative Example 5 in which a large amount of magnesia material was added at 42% by weight and baked at a sintering temperature of 1750 ° C. using a hot press as in each of the examples, cracks occurred during sintering.

Further, in Examples 5 to 7 according to the present invention in which additives commonly used as additives for SG plates were externally added, improvements in bending strength and corrosion resistance were observed.

Table 2 shows Examples and Comparative Examples which were fired using a hot press while changing the firing temperature.

[0048]

[Table 2]

In Examples 1 and 8 to 10 in which the firing temperature was changed from 1700 ° C. to 1800 ° C., the strength, corrosion resistance and spall resistance were superior to those of Comparative Example 2 using the conventional firing method. However, it was also confirmed that the strength and corrosion resistance were superior to those of Comparative Example 6 at 1600 ° C. and 1650 ° C. 7 at a lower firing temperature using a hot press.

When a hot press is used and the firing temperature is relatively low, ie, 1600 ° C. or 1650 ° C., that is, less than 1700 ° C., the porosity, bending strength and corrosion resistance are equivalent to those of Comparative Example 2 using the conventional firing method. No effect using the hot press was observed.

[0051]

The sintering temperature is 1700 using a hot press.
By firing at a temperature of not less than ℃, it is possible to increase the amount of magnesia raw material without causing cracks in the refractory at the time of firing, and to provide a carbon-containing refractory having high strength suitable for SG plates and the like and excellent corrosion resistance, and a method for producing the same. Can be provided.

[Brief description of the drawings]

FIG. 1 is a plan view of an SG plate according to the present invention.

FIG. 2 is a plan view of an SG plate using a replacement ring according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Frame 2 SG plate main body 3 Through hole 4 SG plate 5 Ring 5 'Replacement ring

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tamotsu Wakita 1st Minamifuji, Ogakie-cho, Kariya-shi, Aichi Pref. Toshiba Cellular Co., Ltd. Lamix Corporation Kariya Factory

Claims (5)

[Claims] 1. A magnesia material having a content of 15 to 40% by weight, a carbonaceous material having a content of _{3 to} 15% by weight, and a balance having an Al ₂ O ₃ content of 9%.
A thermosetting organic binder that binds the refractory inorganic material is added to a refractory inorganic material made of an alumina-based material that is 0% by weight or more, and after kneading, a molded body formed into a predetermined shape is subjected to hot pressing. 1700 in an oxidizing atmosphere
A carbon-containing refractory fired at a temperature of at least ℃. 2. The carbon-containing refractory according to claim 1, wherein the molded body is formed into a shape of a refractory for molten metal. 3. The carbon-containing refractory according to claim 2, wherein the refractory for molten metal has a shape of a slide gate plate. 4. The carbon-containing refractory according to claim 2, wherein the refractory for molten metal has a ring shape. 5. A magnesia-based raw material of 15 to 40% by weight, a carbonaceous raw material of 3 to 15% by weight, and the remainder having an Al ₂ O ₃ content of 9
A thermosetting organic binder is added to a refractory inorganic material made of an alumina raw material of 0% by weight or more, kneaded, formed into a predetermined shape, dried, and then subjected to a non-oxidizing atmosphere using a hot press. And sintering at a temperature of 1700 ° C. or more.