JPH01167268A - Carbon-containing uncalcined refractory - Google Patents

Abstract

PURPOSE:To obtain a carbon-containing uncalcined refractory having improved strength in a wide temperature range from low temperature range to high temperature range and spalling resistance, by blending a carbon-containing refractory component with aluminum coated carbon fibers. CONSTITUTION:100 pts.wt. carbon-containing refractory component is blended with 0.5-30 pts.wt. aluminum coated carbon fibers to give an uncalcined refractory. SiO2, Al2O3, ZrO2, MgO, CaO, SiC, TiC, B4C, Si3N4, AlN, TiN, graphite, etc., may be cited as refractory aggregate to be used. The aluminum coated carbon fibers mean carbon fibers obtained by forming an aluminum layer or an aluminum alloy layer on carbon fibers having about 5-50mu diameter by melt plating method, PVD method, CVD method, etc., or by coating the same carbon fibers with an aluminum compound to form aluminum or an aluminum alloy by beating in use of the refractory.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applicable to low temperature ranges of 200 to 600°C and
The present invention relates to an unfired refractory with particularly improved strength and spalling resistance in the intermediate temperature range of 00°C.

Conventional technology and its problems Unfired refractories made of refractory aggregate and organic binder are less prone to cracking, and even if cracks do occur, cracks are less likely to spread than fired bricks. It has some degree of spalling resistance.

However, for special refractories such as plate bricks of sliding nozzles (hereinafter referred to as SN) used for controlling the flow rate of molten metal flow, physical and chemical erosion effects due to rapid thermal shock and wear caused by the molten metal flow occur. Therefore, a higher degree of spalling resistance and corrosion resistance is required.

Carbon is a material with excellent slag resistance, high thermal conductivity, and low coefficient of thermal expansion, so it has excellent spalling resistance, and this property is maintained even when mixed or combined with fine materials. be done. Therefore, materials that are strongly required to have spalling resistance often contain carbon.

Organic binders are broadly classified into two types: thermoplastic resins that soften and melt as the temperature rises, and thermosetting resins that harden as the temperature rises. The unfired refractories bonded with the former have 100~
Because the binder softens and melts at a temperature of 300°C, the strength decreases, and the strength of the bonded material at the latter temperature is 400-800°C.
Because the resin undergoes polycondensation and carbonization at a temperature of ℃, the strength decreases.

In order to suppress the decrease in strength in such low temperature ranges (200 to 600 °C) and intermediate temperature ranges (600 to 1000 °C), fine metal powders such as aluminum and aluminum alloys are added. For example, Japanese Patent Publication No. 54-163
Such examples are found in JP-A-55-107749 and the like.

Furthermore, attempts have been made to add thin wires (fibers) made of aluminum or aluminum alloy as a means of suppressing the decrease in strength in the intermediate temperature range, improving spalling resistance, and preventing peeling and wear due to cracking. For example, JP-A-6
Such techniques are described in Japanese Patent Application Publication No. 1-136966, Japanese Patent Application Laid-open No. 146773/1983, and the like.

However, by adding metal powder or metal fiber such as aluminum or aluminum alloy, intermediate temperature (60
Although considerable effects have been recognized in improving strength and corrosion resistance in the high temperature range (1000°C and above) from 0 to 1000°C, unlike SN plate bricks, it is not only good in corrosion resistance and spalling resistance, but also in the low temperature range. For refractories that are used under severe conditions that require a high degree of dimensional accuracy up to a high temperature range, improvements in effectiveness are still insufficient in terms of preventing the occurrence of cracks and the propagation of cracks that have occurred.

Means for Solving the Problems The present inventor has developed an unfired refractory that exhibits high mechanical strength and excellent corrosion resistance in a wide temperature range from low to high temperatures, and has significantly improved spalling resistance. In order to obtain this, we have conducted various studies.

As a result, they found that the objective could be achieved when aluminum-coated carbon fibers (referring to carbonaceous or graphite fibers; the same shall apply hereinafter) were added to a mixture of carbon-containing refractory aggregate and organic binder. , we have completed the present invention.

That is, in the present invention, for 100 parts by weight of the carbon-containing refractory component,
The present invention provides a carbon-containing unfired refractory characterized by blending 0.5 to 30 parts by weight of aluminum-coated carbon fiber.

The refractory aggregate used in the present invention is not particularly limited, and includes silica (Si02), alumina (A1203), zirconia (Zr02), magnesia (MgO), lime (
Oxides such as CaO) and their compounds and mixtures; 5iC1TiCSB4 C5Si3 N4, AΩ
N5TiN.

Carbides, nitrides, and borides represented by BN and ZrB2, as well as their compounds and mixtures, graphite (including natural graphite such as scale graphite and engineered graphite, and artificial graphite such as pitch coke and needle coke); Any known material can be used, such as carbon materials such as amorphous carbon. When producing the refractory of the present invention, the above-mentioned materials may be appropriately mixed and used so that the carbon content in the refractory aggregate is 3 to 50% by weight.

The organic binder is also not particularly limited, but thermosetting resins with a large amount of residual carbon are preferred, and phenolic and furan resins are more preferred in terms of cost. The amount used is not particularly limited, but it is usually 2 to 1 part by weight per 100 parts by weight of the total amount of fire-resistant aggregate and aluminum-coated carbon fiber.
It is approximately 0 parts by weight.

The aluminum-coated carbon fiber used in the present invention is
Aluminum or aluminum alloy layers are formed on carbon fibers with a diameter of about 5 to 500 μm by melt plating, PVD, CVD, etc., and aluminum or aluminum alloys are formed on similar carbon fibers by heating when using refractories. means coated with an aluminum compound that produces Aluminum compound-coated fibers can be produced, for example, by dissolving an aluminilla compound such as an alkoxide in an organic solvent and dipping carbon fibers in this.
can get. The thickness of the coating layer (as AΩ) is not particularly limited, but is usually 1/'100 to 1/' of the carbon fiber diameter.
It is within the range of about 2.

Aluminum coated carbon fiber can be straight, curved, chevron,
It can be used in various shapes such as waveform. The thickness of the aluminum-coated carbon fiber is 0.005 to 0.00 mm in diameter.
A range of 5 mm is suitable.

If the thickness is less than 0.005 mm, it will be difficult to disperse it into the formulation, and if the thickness exceeds 0.5 mm, no significant improvement in spalling resistance can be expected.

The appropriate length is 1 to 15 mm. If the length is longer than 15 mm, the fibers become entangled with each other, making it difficult to uniformly disperse them into the clay or brick composition, resulting in a decrease in spalling resistance and in filling properties. On the other hand, if it is shorter than 1 mm, it will not contribute sufficiently to improving spalling resistance. The amount of aluminum-coated carbon fiber added is 0.5 parts by weight per 100 parts by weight of the fire-resistant aggregate.
~30 parts by weight. If this amount is less than 0.5 parts by weight,
Sufficient strength and spalling resistance cannot be obtained. - way, 3
If it exceeds 0 parts by weight, the proportion of carbon fiber in the matrix becomes large, making mixing and kneading operations difficult and making it difficult to obtain a refractory of good quality.

In the present invention, in the above-mentioned formulation, if necessary, for example, carbon, aluminum (Af2), silicon (Si), magnesium (Mg), zinc (Zn), and alloys thereof with a particle size of 0 are added. 1 to 15 parts by weight of metal powder of .5 mm or less can be added to 100 parts by weight of the refractory aggregate.

This makes it possible to more effectively prevent a decrease in strength in the intermediate temperature range of 600 to 1000°C.

Effects of the Invention According to the present invention, an unfired refractory which has excellent spalling resistance and whose strength decreases little from a low temperature range to a high temperature range can be obtained.

In addition, aluminum, which is an optionally added component, produces alumina (Al2O2), which is a typical fire-resistant material, when oxidized, and carbon has excellent slag resistance. This contributes not only to improving properties but also to improving corrosion resistance.

The unfired refractory of the present invention exhibits similar remarkable effects not only as a shaped refractory but also as a monolithic refractory such as a castable refractory or a plastic refractory.

EXAMPLES Hereinafter, examples will be shown to further clarify the features of the present invention.

Examples 1 to 6 and Comparative Examples 1 to 5 Alumina-carbon blends shown in Table 1 (parts by weight)
were mixed and kneaded, and this was pressed into a 1000 m
114mmx230mmx4 at kg/cm2 pressure
After molding to 5 mm, it was dried in a hot air dryer at 220° C. for 24 hours to prepare a sample.

The results are also shown in Table 2.

As is clear from Table 2, the example product had a bending strength of 150 kgf/8 at all tested temperatures.
It has w12 or more and has excellent corrosion resistance and spalling resistance.

Note 1) For tests at 500°C, 1000°C, and 1400°C, the sample embedded in coke pleat was sent into a tunnel electric furnace, held at a predetermined temperature for 30 minutes, and then measured using the three-point method.

Note 2) 30mm x 30 in hot metal kept at 1600°C
Immerse the specimen cut into mm x 230 mm for 3 minutes 2
After performing air cooling three times for 15 minutes and measuring the elastic modulus of the test specimen, it was divided into two equal parts in the length direction and cracks in the cross section were observed. ○: Fewer cracks, △: Considerable cracks, ×: Significantly more cracks. The smaller the rate of decline in elastic modulus, the better the spalling resistance.

Note 3) High-frequency furnace lining method: A high-frequency furnace is lined with sample bricks, ordinary steel is melted, and iron oxide is used as a flux.
Hold at 650°C for 3 hours.

After the test, measure the area of erosion loss and use it as the amount of erosion loss.

The smaller the erosion index, the better the corrosion resistance.

Example 7 and Comparative Example 6 Table 3 shows the formulations of the magnesia-carbon materials used.

This mixture was mixed and kneaded and molded at a molding pressure of 1000 kgf/cm2 to form a 114 mm x 230 mm x 45
After molding into a size of 2 mm, it was dried at 200°C for 36 hours.

The results are also shown in Table 3.

As seen in Table 3, it is clear that the products of the present invention are significantly superior in bending strength and spalling resistance.

Table 3 *Corrosion-resistant high-frequency furnace lining method: A high-frequency furnace is lined with sample bricks, ordinary steel is melted, and synthetic slag with C/S=1 and iron content (Total, Pe) -20% is used. Amount of erosion when held at 1680°C for 3 hours.

Test methods for bending strength, spalling resistance, etc. are based on Examples 1-6 and Comparative Examples 1-5.

Example 8 and Comparative Example 7 Plate bricks for sliding nozzles for tundish were molded using the same formulations as in Example 5 and Comparative Example 2, and after drying and polishing under the same conditions as the products shown in Table 1, Actual machine used (Example 8 and Comparative Example 7, respectively)
).

As a result, in Example 8, 12 stations (total amount of molten steel passing through 1
200 tons), and no surface roughness was observed on the sliding surfaces of the plate bricks, whereas in Comparative Example 7, hot water leaked from the sliding surfaces at the 6th brick (575 tons) and the plate bricks were not used. has been discontinued.

(that's all)

Claims (1)

[Claims] (1) A carbon-containing unfired refractory characterized in that 0.5 to 30 parts by weight of aluminum-coated carbon fibers are blended with 100 parts by weight of a carbon-containing refractory component.