JPH0812456A - High-strength refractory - Google Patents

Abstract

PURPOSE:To improve pulling resistance of fiber by strengthening bond strength between carbon fibers as a reinforcing material and a parent material matrix. CONSTITUTION:This high-strength refractory is obtained by blending a refractory aggregate with carbon fibers and optionally carbon raw material powder/ molding. The carbon fibers are at least one kind selected from carbon fibers obtained by carbonizing an organic resin applied to the surface of fibers and carbon fibers and carbon yarn obtained by knitting carbon yarns.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-strength refractory material which is used for refining molten metal, a container for transportation, a member for continuous casting and the like. More specifically, the present invention relates to a refractory material having a high strength by incorporating carbon fibers having enhanced pull-out resistance to a matrix matrix.

[0002]

Carbon-containing refractory materials such as MgO-C, Al ₂ O ₃ -C bricks, etc. are made of refractory aggregates such as MgO and Al ₂ O ₃ with carbon raw materials such as soil graphite, scaly graphite and artificial graphite. By compounding, it is a composite refractory in which the wettability to slag is deteriorated and the thermal conductivity is increased to improve the corrosion resistance and the thermal shock resistance. Due to these advantages, carbon-containing refractories are now
It is widely used as a refractory material for steel such as electric furnaces, towing cars, pots and other lining materials, and immersion nozzles.

In order to improve the thermal shock resistance of such a carbon-containing refractory material, it is considered to increase the thermal conductivity by increasing the compounding amount of graphite in the refractory material. However, an excessive amount of graphite compound causes the oxidation and disappearance of graphite, which deteriorates the strength and corrosion resistance. Therefore, for example, the graphite content of MgO-C bricks is usually
It remains around 20%. In this respect, MgO-C, which is excellent in thermal shock resistance, is inferior in oxidation resistance by increasing the graphite content by several% compared to other parts, such as converter tuyere, where thermal shock resistance is particularly required. Although the bricks are divided and used, it is costly to change the type of the refractory bricks depending on the site when constructing the refractory bricks, since the work on site is required.

Due to these drawbacks, it is desired to develop a refractory material having improved thermal shock resistance while maintaining corrosion resistance and oxidation resistance.

Conventionally, the addition of various fibers has been one of the means for improving the mechanical properties of refractory materials. Means for improving mechanical properties and impact resistance by adding fibers such as metal fibers and ceramic fibers have been studied so far, and in the case of irregular shaped refractories, addition of metal fibers such as steel and stainless steel is not recommended. It is general and already in practical use.

On the other hand, carbon fiber is superior in hot strength as compared with metal fiber, and in a carbon-containing refractory, the matrix of the base material is carbonaceous and is the same as the fiber, so that it is easily integrated in terms of material. It has advantages such as being able to achieve the above, and can be expected to have a reinforcing effect over metal fibers.

From this effect, JP-A-56-140080 discloses a means for improving the thermal shock resistance of the plate material by adding carbon fiber to the carbon-containing refractory material for the sliding nozzle plate.

The strengthening mechanism by the addition of these fibers is that cracks occur in the refractory, and the compounded fibers show resistance to bridging or pulling out when propagating in the matrix. This is a mechanical reinforcing effect that increases the fracture energy of the refractory matrix portion and inhibits the progress of cracks. In order to sufficiently obtain this effect, it is desirable that the fiber material to be added has long fibers rather than short fibers and is three-dimensionally uniformly dispersed in the matrix of the matrix.

However, in reality, it is difficult to uniformly add the long fibers by a general kneading method in the refractory production process, and the fibers are cut by aggregate particles during the kneading. There's a problem. Therefore, reinforcement by adding chopped fibers is being considered.
For the sake of convenience, the short fiber and the long fiber are referred to as having a length shorter than 10 mm and a long length.

A problem when using short fibers as a reinforcing material is weak bonding force between the matrix and the fibers.
That is, the bond form between the fiber and the matrix is generally a carbon bond generated by carbonization of an organic binder such as phenol resin, tar pitch, etc., whose strength is relatively weak and the reinforcing effect of the carbon fiber is expressed. The fiber pulls out before.

In Japanese Patent Publication No. 43662/1993, as a means for preventing the above-mentioned drawbacks, strengthening the bonding force between the matrix of the base material and the carbon fiber, and improving the pull-out resistance, the surface of the fiber is made of a boron compound-containing organic compound. Means for coating with a resin have been proposed.

This is because B ₄ C (s) is generated between the carbon fiber and the matrix of the base material at the time of temperature rise, and by forming a bond mediated by this, the bond strength is strengthened and pull-out resistance is increased. Is the way.

However, a carbon-containing refractory material in operation,
For example, in MgO-C brick, the atmosphere in the refractory is P _co = 1 (a
tm), and thermodynamically B ₄ C (s) is about 930 ℃
It reacts with CO (g) to form B ₂ O ₃ (l) and loses its binding strength. Similarly, a means for strengthening the bond with a metal carbide generated from Al, Si, etc., that is, a means for strengthening the bond by generating such a carbide and increasing the pull-out resistance is a metal carbide oxide depending on the temperature. Therefore, it cannot be said that its function is sufficiently exhibited at high temperature, which is not desirable.

[0014]

SUMMARY OF THE INVENTION Therefore, the present invention provides a bond between a matrix matrix and a fibrous material, which is a problem when short carbon fibers are used as a reinforcing material in order to improve the strength and thermal shock resistance of refractory materials. The purpose is to develop a technique for improving the weakness of force and improving the pull-out resistance of fibers.

[0015]

Here, the present inventors
As a result of various studies to achieve the above object, the following findings were obtained and the present invention was completed. (i) A carbon fiber having an irregular surface which enhances mechanical drawing resistance can be obtained by coating a carbon short fiber with an organic resin in advance and carbonizing the same. (ii) The same surface irregularity can be obtained by knitting fibers, for example, in three-knit or four-knit.

Therefore, the gist of the present invention is a refractory material formed by mixing and molding a refractory aggregate and carbon fibers, wherein the carbon fibers carbonize the organic resin coated on the fiber surface. It is a high-strength refractory material which is at least one selected from the group consisting of carbon fibers obtained by the above and carbon fibers obtained by weaving carbon fibers.

According to a preferred embodiment of the present invention, carbon raw material powder may be further added. As described above, according to the present invention, it is possible to improve mechanical characteristics such as strength characteristics and toughness by blending the carbon fibers having the fiber surface irregularities as described above.

[0018]

The function of the refractory material according to the present invention will be described in detail below. As carbon fibers, products having excellent specific physical properties such as strength and elastic modulus have already been marketed according to their uses.

Generally, carbon fibers designed to have a high elastic modulus are inferior in strength, but usually have a tensile strength of 2 GPa or more. On the other hand, the strength of the refractory as the base material is about several tens of MPa in terms of bending strength even in the case of fired bricks, and even high elastic carbon fiber has sufficient strength as a reinforcing material. Therefore, it is not necessary to limit the use to high strength carbon fiber.

Regarding the size, the diameter of the single fiber is 1 to 50 μm.
Preferred chopped fiber. This is because it is difficult to produce short fibers in this range or less in terms of the production method,
Also, if the diameter is larger than this, the flexibility of the fiber is lost and the fiber easily breaks and cracks easily.

The surface of the fiber is previously coated with a phenol resin, a furan resin, an organic resin such as tar / pitch, or a mixture thereof, and the fiber surface is heated to 500 to 3000 ° C. in an inert atmosphere or a reducing atmosphere for coating. Carbonize / graphitize the layer. The organic resin used for coating the fibers should be selected so that the carbonaceous material produced by the carbonization treatment has the same quality as the fibrous material. That is, if the fiber is a graphitic one, a graphitizable carbon material such as tar / pitch or vinyl chloride resin, which is easily graphitized, is used. It is desirable to select a non-graphitizable carbon material such as vinylidene.

In both cases, it is preferable to select an organic resin having a residual coal rate of 20 wt% or more, considering the amount of irregularities formed on the fiber surface. This is because when a resin having a residual carbon content of less than 20 wt% is used, sufficient unevenness is not always imparted.

The coating of the fiber surface with the resin can be carried out by kneading the fiber and the organic resin with a kneader such as a mixer and then heating and curing in a dryer. When the fibers are aggregated into a ball shape when kneading the resin and the fibers, the resin may be diluted with a solvent such as alcohol and then the solvent may be volatilized to deposit the resin on the surface of the fiber. Alternatively, the apparent viscosity of the resin may be lowered by heating to knead. These methods are means for chemically growing graphite or carbon generated from a resin on the surface of carbon fiber to impart irregularities.

Next, as another method of the present invention, a case where carbon fibers are knitted into carbon fibers having surface irregularities will be described. That is, it is possible to provide a means for physically providing unevenness on the fiber surface by forming a plurality of single fibers in a rope shape. This measure also increases the pull-out resistance of the fiber.

As a concrete means, the method of weaving fibers in this method is a general organic fiber (cotton, nylon, etc.)
The knitting method may be, for example, three-knitting, four-knitting or the like. What should be noted here is the low knot strength of carbon fiber. That is, in the case of carbon fiber, a phenomenon (nodule) in which the fiber breaks when bent is likely to occur,
Therefore, it is preferable to avoid tying carbon fibers in the above braiding.

At least one kind of carbon fiber prepared by the above-mentioned appropriate means is added at a ratio of 0.3 to 20% by weight in a refractory aggregate or a refractory aggregate and a carbon raw material together with a binder, and a conventional method is used. After kneading and molding by the method, perform a curing treatment in the air at a temperature of 300 ° C or less, or in a reducing atmosphere at 1500
The target carbon-containing refractory can be produced by firing at a temperature of ℃ or less. In the present invention, blending, kneading, molding and firing of each raw material powder may be carried out according to a conventional method, and there is no particular limitation.

The refractory aggregate that can be used in the present invention includes:
Examples thereof include MgO, CaO ₂ , Al ₂ O ₃ , ZrO ₂ , SiO ₂ and spinel, and as carbon raw materials, soil graphite, scaly graphite, artificial graphite, anthracite, carbon black and the like can be used. It is also possible to use metal powder such as Al and Si as an antioxidant. Next, the operation of the present invention will be described more specifically with reference to Examples.

[0028]

【Example】

(Example 1) In this example, a carbon fiber-containing MgO-C brick was prototyped. First, a PAN-based carbonaceous carbon fiber having a diameter of 20 μm and a length of 3 mm was added with a phenol resin (residual carbon ratio 35 wt%) so as to be 10 wt% with respect to the total amount of the fiber, and mixed for 15 minutes using an Erich mixer. . After curing at 200 ° C., carbonization at 1000 ° C. for 5 hours in a nitrogen atmosphere was performed to obtain the target surface-treated carbon fiber 1.

Further, carbon fibers 2 whose surface was coated with a resin in the same manner as above without heat treatment and carbon fibers 3 whose surface was not coated were used as comparative materials.
These carbon fibers 1, 2 and 3 are premixed with a scaly graphite fine powder having a diameter of 0.3 mm or less and a V-type blender,
After that, the total amount of electromelted magnesia and metallic Al, which are other components, and a phenol resin were added and kneaded.

The raw material mixture thus obtained was molded using a vacuum friction press at a molding pressure of ² ton / cm ² , and 230
A molded body of × 114 × 65 mm was produced, and then this molded body was heat-treated at 1000 ° C for 2 hours in a reducing atmosphere to produce a fired brick.

The physical properties of the refractory brick thus obtained,
The characteristics were evaluated. Table 1 collectively shows the raw materials used for the production, the blending ratio, and the respective physical property values obtained by the test.

The test procedures were as follows. (1) Bending strength: Measured according to JIS R 2213. The bending strength of Comparative Example 2 is 100, and the ratio is shown. The higher the value, the higher the strength. (2) Compressive strength: Measured according to JIS R 2206. The compression strength of Example No. 2 which is a comparative example is set to 100 and is expressed as a ratio to this.

(3) Slag erosion resistance Each sample was stretched in a high-frequency induction furnace, and the amount of reduction in cross-sectional area due to melting loss was compared and evaluated. The numerical value is the amount of erosion of Example No. 2 which is a comparative example.
It is set to 100 and expressed as a ratio to this, and the larger the value, the better the corrosion resistance. In addition, converter slag was used as an erosion agent.

(4) Thermal shock resistance: A sample of 30 × 30 × 120 mm was heated in an electric furnace in Ar gas at 1300 ° C. for 5 minutes, then dropped in liquid nitrogen to be rapidly cooled, and then the bending strength was increased. It compared by measuring. The numerical value is the bending strength of Example No. 2 which is a comparative example.
It was set to 100 and expressed as a ratio to this.

(5) Oxidation resistance: A sample having a diameter of 50 × 60 mm was held at 1000 ° C. for 2 hours in an electric furnace and the thickness of the decarburized layer was compared.
The values are expressed as a ratio to the thickness of the No. 2 decarburized layer, which is a comparative example, being 100. O ₂ gas was blown into the furnace and the O ₂ concentration was adjusted to be constant.

[0036]

[Table 1]

Next, the refractory material obtained in this example was actually subjected to 10 to
n When used as a brick material for the tuyeres of a composite blowing converter, the wear rate was about 50% compared to the conventional MgO-C brick.
The reducing effect was recognized.

Example 2 In this example, carbon fiber-containing Al ₂ O _3-
A SiC-C brick was produced. Tar pitch (residual coal rate 42 wt%) was added to pitch-based carbonaceous carbon fiber having a diameter of 15 μm and a length of 5 mm so as to be 10 wt% with respect to the whole fiber, and carbonized in the same process as in Example 1. By doing so, the target surface-treated carbon fiber 4 was obtained. Further, carbon fiber 5 which was not subjected to heat treatment was used as a comparative material.

Each of these carbon fibers 4 and 5 was premixed with scaly graphite fine powder of 0.3 mm or less, and then other components,
That is, the total amount of fused alumina and silicon carbide and the phenol resin were added and kneaded.

This raw material mixture was molded at a pressure of ² ton / cm ² using a vacuum friction press, and then this molded body was heat-treated at 1000 ° C. for ² hours in a reducing atmosphere to produce a fired brick.

The refractory bricks thus obtained were tested for properties such as strength. Table 2 shows the raw materials, blending ratios, and test results of the manufactured brick materials.

[0042]

[Table 2]

The test methods shown in Table 2 are in accordance with the test methods of Table 1, and the physical property values after the bending strength are expressed as a ratio to each physical property value of Comparative Example No. 7 as 100. .

(Example 3) In this example, a carbon fiber-containing MgO-C brick was produced. A pitch-based carbon fiber having a diameter of 7 μm was woven into three braids, and then cut into a length of 4 mm to obtain a target carbon fiber 6.

After the carbon fiber 6 was premixed with the fine graphite powder of 0.3 mm or less, the other components were added and kneaded.
This raw material mixture was mixed with a vacuum friction press 2
Molded at a pressure of ton / cm ² and then 1000 ° C in a reducing atmosphere
A fired brick was produced by adding a heat treatment for 2 hours.

The refractory bricks thus obtained were tested for properties such as strength in accordance with Example 1. Table 3 shows the raw materials of the brick material, the compounding ratio, and the test results collectively.

[0047]

[Table 3]

The test methods shown in Table 3 are in accordance with the test methods of Table 1, and each physical property value of Comparative Example No. 9 was set to 100 and expressed as a ratio to this.

[0049]

INDUSTRIAL APPLICABILITY The present invention improves the strength characteristics and the thermal shock resistance of conventional refractories. According to the present invention, at the same time, other characteristics such as corrosion resistance and oxidation resistance are compared with those of conventional refractories. Therefore, it is possible to improve without any loss. Due to such an effect, it can be effectively used as a carbon-containing refractory material such as a brick for tuyeres of a converter for which the oxidation resistance is lowered by increasing the blended carbon amount by placing emphasis on thermal shock resistance. In addition, in addition, it is possible to improve the life of members such as a hot metal wheel, a converter hot water contact portion, and a CC nozzle that require particularly high strength and thermal shock resistance.

Claims (2)

[Claims] 1. A refractory formed by mixing and molding a refractory aggregate and carbon fibers, wherein the carbon fibers are obtained by carbonizing an organic resin coated on the fiber surface, and carbon fibers. A high-strength refractory material which is at least one kind selected from the group consisting of carbon fibers obtained by knitting. 2. The high-strength refractory material according to claim 1, further comprising carbon raw material powder.