JPH06135762A - Carbon-containing refractory - Google Patents

Abstract

PURPOSE:To provide carbon-contg. refractories excellent in resistances to spalling, wear and oxidation. CONSTITUTION:A starting material blend of 3-50wt.% carbon material with 50-97wt.% refractory aggregate is prepd. and lanthanum boride is added to the blend by 0.1-5 pts.wt. per 100 pts.wt. of the blend to obtain the objective carbon-contg. refractories.

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 having excellent spalling resistance, abrasion resistance and oxidation resistance.

[0002]

Refractory materials containing carbon materials such as graphite are
Since carbon has a high thermal conductivity and a property that it is difficult to wet molten metal and slag, it has been widely used as a refractory material for various metallurgy. However, in recent years, the use conditions of refractories have become more severe, and further improvement in durability of carbon-containing refractories is desired.

The damage mechanism of carbon-containing refractories is generally wear,
The present invention relates to spalling resistance, abrasion resistance, and oxidation resistance, which are roughly classified into four types: spalling, melting loss, and oxidation. Conventionally, as a means for improving the oxidation resistance of a carbon-containing refractory, for example, Japanese Patent Application Laid-Open No. 54-163913 discloses a method of adding a metal powder such as Al having a stronger oxygen affinity than carbon. However, this method has a problem that the expansion coefficient of the refractory increases due to the volume expansion when the metal powder is oxidized, and the spalling resistance decreases.

Further, in Japanese Patent Laid-Open No. 57-5811, B
By adding a boron compound such as ₄ C or BN, B ₂
A method of forming an O ₃ -based glass phase to coat carbon and improve the oxidation resistance of the refractory is disclosed. However, with this method, the strength cannot be improved, and conversely, the abrasion resistance tends to decrease due to the formation of the glass phase having a low softening point.

As a means for improving the spalling resistance of the carbon-containing refractory, for example, Japanese Patent Publication No. Sho 62-9553 discloses a method of adding carbon fiber. However, it is not easy to uniformly disperse the carbon fibers in the refractory structure, and even if the carbon fibers are uniformly dispersed, the effect is small, so that the technique has not been widely used.

[0006]

In order to improve the durability of the carbon-containing refractory, it is important that spalling resistance, abrasion resistance and oxidation resistance are all excellent at the same time.
However, as described above, a technology that satisfies these requirements at the same time has not yet been provided.

Therefore, an object of the present invention is to provide a carbon-containing refractory material which is excellent in spalling resistance, abrasion resistance and oxidation resistance at the same time.

[0008]

As a result of various studies to solve the above problems, the present inventors have found that adding lanthanum boride is very effective, and completed the present invention. Came to do.

That is, in the carbon-containing refractory material according to the present invention, lanthanum boride is externally applied to 100 parts by weight of a raw material mixture consisting of 3 to 50% by weight of carbon material and 50 to 97% by weight of refractory aggregate. It is characterized in that 0.1 to 5 parts by weight is added.

[0010]

[Function] The damage of the carbon-containing refractory progresses due to the dissolution and desorption of the refractory aggregate particles into the slag on the operating surface and the oxidation disappearance of the carbon material, and the cracking occurs inside the refractory separated from the operating surface. Outbreak accelerates damage. Therefore, in order to reduce the damage of the carbon-containing refractory, it is necessary to simultaneously improve the oxidation resistance, the wear resistance and the spalling resistance.

In general, it is effective to prevent the supply of oxygen to the carbon material in order to improve the oxidation resistance of the carbon-containing refractory, and to improve the wear resistance and spalling resistance. Increasing the strength of carbon-containing refractories is believed to be effective. By adding lanthanum boride, the carbon-containing refractory material of the present invention could have both properties.

In the carbon-containing refractory material of the present invention, lanthanum boride reacts preferentially with oxygen in the operation aspect due to its high affinity with oxygen, thereby preventing the supply of oxygen to the carbon material and by reacting with oxygen. Generate B ₂ O ₃ -L
The a ₂ O ₃ -based oxide coats the carbon material and further functions to hinder the supply of oxygen. As a result, the oxidation disappearance rate of the carbon material is significantly reduced, and the oxidation resistance of the carbon-containing refractory is improved.

Further, lanthanum boride reacts with the surrounding carbon material inside the carbon-containing refractory at a high temperature to form a carbide, and acts as a binder for bonding the carbon materials together. As a result, the strength of the refractory material is increased, and the wear resistance and spalling resistance are improved.

The lanthanum boride according to the present invention has a chemical formula of L
It refers to what is expressed as aB _6, and there is no problem if the starting material used contains impurities. However, in order to expect the above-mentioned action, a material with high purity is desirable. Further, the particle size is preferably 44 μm or less in consideration of dispersibility in the carbon-containing refractory structure.

The lanthanum boride is preferably added in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the total amount of the carbon material and the refractory aggregate. If it is less than 0.1 part by weight, a sufficient effect cannot be obtained, and if it is more than 5 parts by weight, the corrosion resistance is deteriorated, which is not preferable.

The refractory aggregate that can be used in the present invention includes:
Examples thereof include oxides such as magnesia, spinel, calcia, dolomite, alumina, silica, zirconia and zircon, and non-oxides such as silicon carbide, silicon nitride, boron nitride, boron carbide and zirconium boride.

The carbon materials usable in the present invention include natural graphite such as scaly graphite and earth-like graphite or artificial graphite,
Examples include electrode scrap, carbon fiber, and pyrolytic carbon. Although the blending ratio of the carbon material varies depending on the kind of the refractory raw material and the purpose of use of the carbon-containing refractory material of the present invention, the carbon material 3 to
It is in the range of 50% by weight, that is, 50 to 97% by weight of the refractory aggregate. If the carbon material is less than 3% by weight, the characteristics that the carbon material is difficult to wet with molten metal or slag cannot be sufficiently exhibited. Further, if it exceeds 50% by weight, sufficient strength cannot be obtained.

Furthermore, the carbon-containing refractory material according to the present invention has the purpose of improving the strength of the refractory material and preventing oxidation of the carbon material.
It is also possible to add metal powders such as 1, Mg, Ca, Si, Cr, and Ti, or alloy powders thereof. The addition amount of these metal powders or alloy powders is usually about 0.5 to 10% by weight.

The carbon-containing refractory material according to the present invention is prepared by kneading the above raw material mixture with a binder (such as a thermosetting resin typified by a phenol resin, pitch, etc.), and after molding, 200 to An unfired product can be obtained by drying to about 300 ° C. Further, it can be fired in a reducing atmosphere or an oxygen-free atmosphere at about 900 to 1500 ° C. and used as a fired product.

[0020]

EXAMPLES The carbon-containing refractory material of the present invention will be described below with reference to examples. Example 1 Various raw materials were adjusted to the compounding ratios shown in Table 1, kneaded, and then 230 × 114 at a pressure of 1500 kgf / cm ^2.
It was pressure-molded to a size of 65 mm. 200 this molded body
It was dried at 0 ° C for 10 hours.

[0021]

[Table 1]

The characteristics of the obtained unfired carbon-containing refractory material are as follows:
As shown in Table 1, the product of the present invention has a smaller weight loss rate in the oxidation test, a smaller amount of wear in the wear test, and a higher hot strength than the comparative product. From these test results, it can be seen that the carbon-containing refractory material of the present invention is simultaneously excellent in oxidation resistance, wear resistance and spalling resistance.

Example 2 As a gas blowing nozzle for a molten metal container, the compound of magnesia, graphite and lanthanum boride of the product 2 of the present invention shown in Table 1 above was mixed with liquid phenol resin 3 as a binder.
In a carbon-containing refractory added with wt%, an inner diameter of 1.5 mm,
An unfired gas-blowing nozzle equipped with a stainless steel tube having an outer diameter of 3.5 mm was manufactured. This gas blowing nozzle was arranged at the bottom of a 250 ton converter furnace, and 8 kgf / cm ² of argon gas was blown at a rate of 8 Nm ³ / min to smelt molten steel. As a result, the wear rate was reduced by 23% as compared with the conventionally used comparative product 9, and no abnormal damage such as peeling due to heat spalling and gas leakage was observed, and the product of the present invention is very effective. It was confirmed.

Example 3 Inventive product 6 and comparative product 13 in Table 1 were molded into a slide valve plate brick shape and fired at 1000 ° C. for 12 hours. As a result of using the obtained fired plate brick as a steel output control device for a 100-ton ladle, the product of the present invention has less surface roughness, less cracks and less corners, and has been used 2 times more than the conventional comparison product. It was confirmed that the effect of the product of the present invention was extremely large after being extended.

[0025]

EFFECT OF THE INVENTION Since the carbon-containing refractory of the present invention contains lanthanum boride, the lanthanum boride reacts preferentially with oxygen to form B during operation of the refractory.
_{The 2} O ₃ —La ₂ O ₃ -based oxide covers the carbon material to suppress the oxidation disappearance, and the oxidation resistance of the carbon-containing refractory is improved. Further, inside the carbon-containing refractory material of the present invention, lanthanum boride reacts with the carbon material to form a carbide, and acts as a binder for joining the carbon materials to each other to improve the strength of the refractory material, Abrasion resistance and spalling resistance are improved. Therefore, the carbon-containing refractory material of the present invention can exhibit high durability when used under conditions in which damages due to oxidation, abrasion and spalling become large at the same time.

Claims (1)

[Claims] 1. A carbon material in an amount of 3 to 50% by weight and a fire-resistant aggregate 5
A carbon-containing refractory material, wherein 0.1 to 5 parts by weight of lanthanum boride is externally added to 100 parts by weight of a raw material mixture consisting of 0 to 97% by weight.