JPH0578180A - Carbon fiber-containing refractory - Google Patents

Abstract

PURPOSE:To relax restrictions on the amount of blended carbon fiber in a conventional refractory in which the carbon fiber is dispersed and obtain a refractory remarkably improved in spalling resistance. CONSTITUTION:A refractory is obtained from a blend of 2-10wt.% carbon fiber having 10-50mum diameter and 0.20-2mm length with 1-10wt.% low-melting active metal such as Si or Al added to refractory powder. Nonoxide-based reaction products such as beta-SiC, Si2ON2, SiC-Al-O-N, Al4O3, AlN or SIALON, e.g. whiskers, flakes or protruding substances such as protruding coverings of the active metal are produced on the surface of the carbon fiber to increase adhesion of the carbon fiber to the surrounding matrix and exhibit withdrawing resistance of the fiber. Thereby, spalling resistance can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refractory material used in a portion which comes into contact with molten metal, particularly pig iron, steelmaking, non-ferrous metal, for example, a blast furnace, a pig iron making furnace for a mixed pig car, a converter, Electric furnace,
The present invention relates to a carbon fiber-containing refractory having excellent spalling resistance applicable to DH furnace, RH furnace, ladle, casting dipping nozzle, sliding nozzle, crucible and the like.

[0002]

2. Description of the Related Art Conventionally, in order to improve resistance to thermal and mechanical spalling in refractory used for lining metal containers, carbon powder such as graphite is sacrificed at the expense of corrosion resistance and heat resistance. Although low-expansion powders such as fused quartz, mullite, and cordierite have been added in excess, in recent years, for example, as disclosed in Japanese Patent Publication No. 62-9553, magnesia carbonaceous refractory. In the case of carbon-containing refractory materials, like carbon materials, attempts have been made to improve mechanical or thermal shock resistance and wear resistance by dispersing carbon fibers without lowering their corrosion resistance. It was

However, the strengthening of the refractory material by dispersing the carbon fiber is not compatible with the refractory material and the carbon fiber, and there is a limit in the amount of the compounded additive, and the effect of carbon fiber itself for strengthening the base is limited. In addition, there is a drawback that the characteristics of the refractory base material itself are lost.

[0004]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a refractory material containing such carbon fibers dispersed therein.
The purpose of the present invention is to provide a refractory material in which the limitation of the compounding amount of carbon fiber is relaxed, the reinforcing function by carbon fiber is increased, and the spalling resistance is further improved without losing the characteristics of the refractory material itself. ..

[0005]

According to the present invention, a refractory powder contains 2 to 10% by weight of carbon fibers having a diameter of 10 to 50 μm and a length of 0.20 to 2 mm, and Si and Al.
A refractory having a composition obtained by adding 1 to 10% by weight of an active metal having a low melting point such as β-SiC, Si ₂ ON ₂ , Si
C-Al-O-N, Al 4 C 3, AlN, SIALON
It is characterized in that non-oxide reaction products of active metals such as, for example, convex substances such as whiskers, flakes and convex coatings are formed on the carbon fiber surface.

The refractory powder may contain a carbon source in an amount of 1% by weight or more and 40% by weight or less.

As the carbon source, graphite powder excellent in oxidation resistance, spalling resistance, corrosion resistance, and conductivity is mainly used, but the carbon source is not limited to this. Anthracite, coke, mesophase pitch, High softening point pitch, liquid or solid high carbonization yield resin, carbon black, organic silicon described later, etc. can be used.

Carbon can also be added in the form of a binder.

Although the splicing effect is further improved by adding the carbon powder, the splicing effect is exhibited by the pulling resistance without adding the carbon powder.
Some do not add carbon sources other than carbon fiber. Further, in order to improve the splicing effect, it is also possible to use a resin binder which preferably exhibits the effect of carbon that can be expected as a carbon source from a resin. Further, it is also possible to use organic silicon or the like as described below.

As the low melting point active metal to be blended, metals such as Ca, Mg, Zr and Fe which have a good reactivity with carbon can be applied, but in particular, stability at room temperature up to metal powder,
Si containing organic silicon from the viewpoint of hot strength and corrosion resistance of the product
Alternatively, Al is suitable.

The formation of the non-oxide reaction product of the active metal on the surface of the carbon fiber is carried out by firing the compound, preheating before use, or heating during use, and the added metal and C, N in the atmosphere. A non-oxide-based compound that is formed by reacting with etc. is formed on the surface of the carbon fiber, and by this, that is, by the convex, the fiber pullout resistance is increased and the splicing effect is improved. Further, by this, the adhesion between the carbon fiber and the refractory is also improved, the amount of the compounded and added is increased, and the effect of improving the spalling resistance by the carbon fiber is dramatically improved.

As the refractory powder, various oxides, carbides, nitrides, oxynitrides, borides, or a mixture of two or more kinds of powders can be used. It can be selected as appropriate.

As the carbon fiber, any commercially available products such as PAN type, pitch type, phenol resin type, carbon type, graphite type and the like can be used and can be appropriately selected in consideration of cost, strength and the like.

[0014]

[Function] By adding a metal that reacts with carbon at a low melting point together with the carbon fiber to the refractory material to form a reaction product, that is, a convex object such as a whisker, around the fiber, the pullout resistance of the fiber is increased. Be done.

When the added metal is Si added, β-SiC is formed around the carbon fiber, and when Al is added, Al ₄ C ₃ and AlN are formed. This generation may be finally generated when the refractory material is in use. Si
Β-SiC due to carbon and carbon is 1200 ° C. or higher, Al ₄ C ₃ due to Al and carbon is generated at 700 ° C. or higher, and Al ₄ C ₃ due to the reaction between Al and nitrogen in the air at 1000 ° C. or higher. AlN by conversion of AlN to AlN
Is generated. Since this reaction occurs in a relatively short time, it can be expected that the heating reaction of the non-fired refractory during use contributes to the improvement of the spalling resistance of these reaction products.

When the amount of Si or Si alloy added is less than 1% by weight as Si, the amount of β-SiC formed around the fiber is not sufficient and the effect of improving spalling resistance is not sufficient. When the amount of Si added is more than 10% by weight, the elastic modulus increases with the formation of β-SiC, and the spalling resistance decreases. Moreover, the corrosion resistance is also reduced.

When the amount of Al or Al alloy added is less than 1% by weight as Al, Al ₄ formed around the fiber
The amounts of C ₃ and AlN are not sufficient, and the effect of improving spalling resistance is not sufficient. If the added amount of Al is more than 10% by weight, the elastic modulus increases greatly with the formation of Al ₄ C ₃ and AlN, and the spalling resistance decreases.

Al and Al alloys are generally industrially produced in the form of atomization, flakes and fibers. When added in the form of fiber, the amount of the fiber itself increases, so that a problem tends to occur in mixing, but there is no problem unless the absolute amount of the fiber added becomes extremely large. As for atomize and flakes, Al is oxidized by oxygen from the air in the pores contained in the molded body or the fired body to generate corundum, and then Al ₄ C ₃ , AlN
Occurs. Therefore, since atomized particles which are usually thicker have a higher generation rate of Al ₄ C ₃ and AlN, it is preferable to add atomized particles, but the mode of addition is not limited to atomized particles.

The matrix also has β-SiC and Al ₄
In order to generate C ₃ and AlN, it is necessary to add carbon powder in an amount of 1% by weight or more. Further, addition of 1% by weight or more of carbon powder can prevent infiltration of slag accompanying the molten metal. If the amount of carbon powder added is more than 40% by weight, corrosion resistance, wear resistance, and oxidation resistance are reduced, and as a result, durability is reduced.

The diameter of carbon fiber added is 10
If it is less than μm, the shear strength of the fiber itself is lowered, and the fiber is sheared before the pulling resistance force is exerted, and the effect of improving the spalling resistance is not obtained. Also,
If it is larger than 50 μm, a phenomenon of returning occurs when the pressure is reduced during the molding of the refractory, the structure of the molded body is destroyed, and as a result, the strength is lowered and the spalling resistance is not improved.

When the length of the carbon fiber is longer than 2 mm, the fibers themselves become entangled to generate hair lumps, so-called bulk, and uniform dispersion of the fiber does not occur, so that the fiber added carefully becomes meaningless. On the other hand, if it is shorter than 0.2 mm, the fiber pullout resistance becomes low, and the effect of improving spalling resistance cannot be expected.

If the amount of carbon fibers added is less than 2% by weight, the number of fibers themselves contributing to the pulling resistance of the fibers will be insufficient and the effect of improving spalling resistance will not be obtained. If the addition amount is more than 10% by weight, the moldability is lowered, the strength is lowered, and the spalling resistance is not improved.

[0023]

EXAMPLES Table 1 shows an example of a fired refractory made by mixing metallic silicon powder together with carbon fiber into refractory powder of alumina-carbon type. In the table, Examples 1 to 4
Indicates that the composition is within the range of the present invention. Comparative Example 1 is an example in which the amount of carbon powder added is less than 1% by weight, and Comparative Example 2 is an example in which the amount of carbon powder added is greater than 40% by weight.
Comparative Example 3 shows a case where no carbon fiber is contained, and Comparative Example 4 shows an example in which carbon fiber is blended but no metal is contained.

In the case of Examples 1 and 2 and Comparative Example 1 in the same table, the same composition was kneaded with a phenol resin as a binder and molded into a shape of 230 × 114 × 65 mm by a friction press, and then in coke powder. It was baked at 1350 ° C. Further, the compounds of Examples 3 and 4 and Comparative Examples 3 and 4 in the same table were mixed and granulated using a phenol resin as a binder, and molded into a shape of diameter 200 × length 500 mm by a hydrostatic press. And was fired in coke powder at 1000 ° C.

[0025]

[Table 1]

The characteristics of each fired refractory are shown in the lower column of the table.
As shown in each example of the table, carbon fiber and S
It is understood that the hot strength and the spalling resistance are improved by using i together. On the other hand, as shown in Comparative Example 3, although the hot strength is exhibited to some extent even by adding only Si, the level of spalling resistance is low.

In the comparison between Example 1 and Comparative Example 1 in Table 1, in the case of Comparative Example 1 in which the amount of carbon powder added is less than 1% by weight, the matrix is also used as in Example 1. The formation of sufficient β-SiC does not occur, and the spalling resistance and hot strength are not sufficiently expressed. Further, in comparison between Example 4 and Comparative Example 2, in the case of Comparative Example 2 in which the amount of carbon powder added was more than 40% by weight, abrasion resistance, hot strength, and further spalling resistance were found in Example 4. It turns out that it is lower than the case.

Table 2 shows an example in which alumina-carbon type refractory powder is mixed with carbon fiber together with metal silicon powder, and metal silicon powder and Si-Al alloy are used as firing refractories. Phenol resin is used as a binder, mixed and granulated, and the diameter is 200 with a hydrostatic press.
× Molded into a shape with a length of 500 mm, 1 in coke powder
It was baked at 000 ° C.

[0029]

[Table 2]

By comparing Example 5 shown in the table with Comparative Example 5 in which the amount of carbon fiber added is less than 2% by weight, when the amount of carbon fiber added is less than 2% by weight, the pull-out resistance of the carbon fiber is reduced. It can be seen that the spatter resistance and hot strength are not sufficiently obtained. The amount of carbon fiber added in Example 6 was 10
By comparing with Comparative Example 6 in which the amount of carbon fiber is more than 10% by weight, when the amount of carbon fiber added is more than 10% by weight, the moldability is lowered, the apparent porosity is slightly lowered, and the hot strength is also lowered. It can be seen that the spalling resistance is also reduced. In addition, comparing Example 7 in the table with Comparative Example 7 in which the amount of Si powder added is less than 1% by weight, when the amount of Si powder added is less than 1% by weight, the amount of produced β-SiC is not sufficient. It can be seen that the pulling resistance of the carbon fiber is not sufficiently exerted, and the spalling resistance and hot strength are not obtained. Further, by comparing Example 5 and Example 8, even in the case of Si-Al alloy, similar effects can be obtained if the Si content is 1 wt% or more.

When Example 9 is compared with Comparative Example 8 in which the amount of Si added is more than 10% by weight, the amount of Si added is 1
It can be seen that when the content is more than 0% by weight, the spalling resistance is deteriorated although the hot strength is satisfactory. It is considered that the cause is an increase in elastic modulus due to excessive production of β-SiC.

Table 3 shows the characteristics when the size of the carbon fiber was changed. Similarly, the mixture was mixed and granulated using phenol resin as a binder, and the mixture was granulated with a hydrostatic press to a diameter of 200 mm and a length of 500 mm. It is formed into a shape and baked in coke powder at 1000 ° C.

[0033]

[Table 3]

By comparing Comparative Example 9 and Example 10 in Table 3, the carbon fiber having a diameter of less than 10 μm may be sheared before the pulling resistance of the carbon fiber occurs. From Examples 11 and Comparative Example 10, no spalling property and hot strength were obtained, and when the diameter of the carbon fiber was larger than 50 μm, the phenomenon of returning occurred at the time of pressure reduction during molding, the structure of the molded body was destroyed, and the apparent porosity was increased. Is increased, the hot strength is lowered, and the spalling resistance is also lowered. Further, by comparing Example 12 and Comparative Example 11, when the length of the carbon fiber is longer than 2 mm, the fiber entanglement occurs due to the entanglement of the fiber, and the carbon fiber added carefully does not make sense. Therefore, spalling resistance and hot strength are not obtained. Comparative Example 12 and Example 13
From this, it is understood that when the length of the added carbon fiber is shorter than 0.2 mm, the pulling-out resistance of the carbon fiber is not sufficiently generated, and the spalling resistance and the hot strength are not obtained.

Table 4 shows magnesia-carbon blends with carbon fibers and Al, Al-Mg alloys, and
The mixture containing the Al-Mg-Ca alloy was kneaded using phenol resin as a binder, and the mixture was mixed with a friction press.
An example of molding into a shape of 30 × 114 × 65 mm and curing treatment at 250 ° C. is shown.

[0036]

[Table 4]

According to Example 14 and Comparative Example 13 shown in the table, when the amount of addition of Al is less than 1% by weight, Al
_The amount of ₄ C ₃ and AlN produced is insufficient, and the spalling resistance,
It can be seen that the hot strength does not appear. Example 18 and Comparative Example 14
By comparing with, when the added amount of Al is more than 10% by weight, the amount of Al ₄ C ₃ and AlN produced is excessive and the hot strength is not a problem, but the spalling resistance is deteriorated. To do. The cause is considered to be an increase in elastic modulus. Similarly, from Examples 15, 16 and 17, Al powder, Al-
The addition amount of Mg alloy powder and Al-Mg-Ca alloy powder is
It can be understood that the same can be used if Al is 2% by weight or more and 10% by weight or less.

An example of using the refractory compositions shown in the above tables in an actual furnace is shown below.

The slide nozzle (650 ×) was prepared by removing carbon fiber from Example 2 in Table 1 and adding 20% by weight of low-expansion synthetic mullite with the same amount of carbon powder.
A 350T ladle having a size of 350 × 45 mm and a diameter of 65 mm was used.

Although the carbon fiber-free product was used together with the low-expansion powder, the edge of the nozzle hole spalled and was severely chipped after three uses, and the use was stopped. .. On the other hand, Example 2
Was healthy after 5 times of use, and was in a usable state.

A long nozzle (nozzle inner diameter 100 mm, outer diameter 170 mm, length 950) was used for Example 3 and Comparative Examples 3 and 4.
(mm) used between a 250T ladle and a tundish.

The comparative example 3 was used once, and the comparative example 2 was used twice, so that the cracking occurred due to spalling and the use was stopped. In order to improve the spalling resistance, two carbon fibers obtained by removing the carbon fiber of Comparative Example 4 and adding 20 wt% of extremely low-expansion fused silica were used. One of them was used five times and cracked by spalling. When it occurs, it will be stopped and another one will be 6
After repeated use, the melted part in the immersion area became large and the use was stopped. On the other hand, in Example 3, cracking and large melt loss were not observed even after 10 times of use, and it was in a good state after use.

Example 15 and the one in which the amount of magnesia powder was increased by removing the carbon fiber, and the amount of carbon powder added was further increased to 30, 35% by weight to further improve the spalling resistance. Adhesion of the converter to the steel outlet (diameter 200 mm, outer diameter 400 mm, length 1
30 mm).

When the carbon fiber was removed after 20 times of continuous use, many cracks were generated by spalling, and the occurrence of chipping was recognized. The degree was more severe as the amount of carbon powder added was smaller. On the contrary, the tendency of melting or abrasion was observed in the carbon powder of 30, 35% by weight. Example 15 was quite sound. The materials other than Example 15 had insufficient durability. When Example 15 was fully covered, wear due to a slight melting loss was recognized after 50 times of use, but a significant improvement in durability was recognized as compared with the carbon fiber-free product.

From the above three examples, carbon fiber and Si
Alternatively, it was confirmed that the spalling resistance can be exhibited without sacrificing other physical properties by using Al together, as in the laboratory.

[0046]

The present invention has the following effects.

(1) By using the carbon fiber and the active metal in combination, the adhesiveness between the carbon fiber and the surrounding matrix can be increased and the pulling resistance of the fiber can be exhibited to improve the spalling resistance.

(2) The amount of carbon powder added is such that the amount of carbon fiber added, the fiber diameter, the fiber length, and the amount of alloy added are within appropriate ranges, and spalling resistance is maintained without sacrificing other physical properties. It is possible to improve.

(3) In particular, the combined use of Al, Si and their alloys is effective for preventing digestion and is therefore effective for intermittent use.

(4) The refractory powder is not limited to high-corrosion-resistant alumina, magnesia, calcia, and spinel, but other high-corrosion-resistant zirconia, zircon, ZrB _2, etc. can be used. Further, low-expansion powders such as fused quartz, synthetic mullite, and zirconia mullite can be sufficiently used if attention is paid to corrosion resistance and heat resistance.

(5) If the molten metal is iron-based, especially steel, there is a problem in corrosion resistance, so if you pay close attention to this point, SiC, Si ₃ N ₄ for increasing oxidation resistance and spalling resistance.
Etc. can also be used. If the molten metal is a non-ferrous metal such as Al or Cu, it can be used as a main body.

(6) The spalling resistance can be remarkably improved without sacrificing other physical properties, and the type, properties, and other conditions of use of the molten metal and the slag accompanying it can be improved. The type and use of the refractory powder may be appropriately selected and are not limited.

Claims (5)

[Claims] 1. A refractory powder containing 2 to 2 carbon fibers each having a diameter of 10 to 50 μm and a length of 0.20 to 2 mm.
A refractory containing 10% by weight and 1 to 10% by weight of an active metal having a low melting point, and containing carbon fiber formed by producing a non-oxide reaction product of the active metal on the surface of the carbon fiber. Refractory. 2. A composition containing a carbon source in an amount of 40% by weight or less as a carbon amount, and the remainder being refractory powder,
A refractory having a composition obtained by adding 2 to 10% by weight of carbon fiber having a diameter of 10 to 50 μm and a length of 0.20 to 2 mm and 1 to 10% by weight of an active metal having a low melting point,
A carbon fiber-containing refractory material obtained by forming the non-oxide reaction product of the active metal on the surface of the carbon fiber. 3. The carbon source according to claim 2, wherein the carbon source is selected from graphite powder, anthracite, coke, mesophase pitch, high softening point pitch, liquid or solid high carbonization yield resin, carbon black, organic silicon and the like. A refractory material containing carbon fibers, which is a combination of one or more of the above. 4. The low melting point active metal according to claim 1 or 2, wherein the active metal having a low melting point is Si, and the non-oxide reaction product formed on the surface of the carbon fiber is β-SiC, S.
Carbon fiber-containing refractory which is a compound of Si such as i ₂ ON ₂ and SIALON. 5. The method according to claim 1 or 2, wherein the active metal having a low melting point is Al, and the non-oxide reaction product formed on the carbon fiber surface is Al ₄ C ₃ , Al.
Carbon fiber-containing refractory that is an Al compound such as N and SIALON.