JPH06107469A - Production of refractory for casting - Google Patents

Abstract

PURPOSE:To considerably enhance hot mechanical strength and to prevent the propagation of cracks in all directions while maintaining corrosion resistance. CONSTITUTION:Fireproof aggregate is prepd. as a base material and 0.2-8 pts.wt. bundles of carbonaceous or graphitic fibers having 0.05-1.0mm secondary fiber diameter and 0.5-10mm length obtd. by bundling single fibers are added to 100 pts.wt. of the base material. They are then kneaded and molded. The bundles are dispersed in the base material with satisfactory fillability and no directional property.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a refractory for casting such as a slide gate, a long nozzle, a dipping nozzle, or a tundish lining refractory used for casting ferrous and non-ferrous metals.

[0002]

2. Description of the Related Art Conventionally, as a method for producing a refractory for casting of this kind, unbonded carbonaceous fibers are added to a main material composed of refractory aggregate and carbon powder (Japanese Patent Publication No.
No. 3-24953, Japanese Unexamined Patent Publication No. 59-207871), or by disposing a net made of carbon fiber (Japanese Examined Patent Publication No. 60-49157, Japanese Unexamined Patent Publication No.
No. 9-156970), or carbon or graphite fiber bundles in which monofilaments are bound are arranged in a directional manner (see Japanese Patent Publication No. 61-38156).

[0003]

However, in the case of using unbundled carbonaceous fibers in the above conventional method for producing a refractory for casting, since the fibers are entangled with each other during kneading and blending, the compressibility at the time of molding is improved. There is a problem that it inhibits and reduces the density of the molded body and significantly reduces the corrosion resistance of the product. For example, the addition of about 3 parts by weight of carbonaceous fiber (externally applied) lowers the density by 10% or more and halves the corrosion resistance, so that it cannot be put to practical use. In addition, when arranging a net made of carbon fiber, the net is a bundle of fibers in a sense, but it is true that the net is uniformly arranged in the molded body in order to prevent crack propagation in all directions. It's impossible. Furthermore, when the carbon or graphite fiber bundles are arranged in a directional manner, there is a problem that crack propagation in all directions cannot be prevented. Therefore,
As a refractory for casting, it is necessary to overcome the above-mentioned drawbacks, but particularly for a slide gate, hot mechanical strength, high spall resistance, and corrosion resistance are required.
Therefore, an object of the present invention is to provide a method for manufacturing a refractory material for casting which can markedly increase the mechanical strength in a hot state and can prevent the development of cracks in all directions while maintaining the corrosion resistance.

[0004]

In order to solve the above problems, a method for producing a refractory for casting according to the present invention comprises a secondary fiber diameter obtained by bundling a single fiber to 100 parts by weight of a main material made of a refractory aggregate. This is a method of adding 0.2 to 8 parts by weight of a carbon or graphite fiber bundle having a length of 0.05 to 1.0 mm and a length of 0.5 to 10 mm, and kneading and molding. Here, the carbon or graphitic fiber bundle is aligned or twisted with carbon or graphitic long fibers (usually having an outer diameter of 3 to 20 μm) produced from polyacrylonitrile, polyvinyl alcohol, coal tar pitch or the like. It is obtained by binding.

[0005]

In the above means, the carbon or graphite fiber bundle is dispersed in the main material with good filling property without having directionality. As the refractory aggregate, alumina, magnesia, calcia, mullite, silica, chamotte, spinel, zircon, zirconia, etc., or a combination of one or more of these composite raw materials is used to enhance strength or oxidation resistance. Therefore, a metal such as silicon or aluminum, a carbide of these metals or boron, or the like is added if necessary. If the secondary fiber diameter of the carbon or graphite fiber bundle is less than 0.05 mm, the filling property becomes poor, and
When it exceeds 0 mm, the surface properties of the refractory material deteriorate, which is not preferable. The secondary fiber length of the carbon or graphite fiber bundle is
The above range is desirable from the viewpoint of dispersibility in the main material and density. If the secondary fiber length is less than 0.5 mm, the bending strength will be insufficient and the density will not increase, and if it exceeds 10 mm, the filling property will be poor and the density will not increase. Furthermore, the main material 10
If the amount of carbon or graphite fiber bundle added is less than 0.2 parts by weight relative to 0 parts by weight, the bending strength will be insufficient and 8
When it exceeds the weight part, the filling property is deteriorated, which is not preferable. In order to sufficiently exhibit the bending strength, it is necessary that the fiber bundle is firmly bonded to the main material, and it is preferable to use phenolic resins or coal tar pitch which are carbon-based bonding materials. When carbon is also used as the main material, a three-dimensional bond ring with carbon obtained from the binder is formed, and the effect on spall resistance becomes more remarkable.

[0006]

EXAMPLES Examples of the present invention will be described below together with comparative examples. Examples 1 to 3 and Comparative Examples 1 to 2 To manufacture a refractory applied to a slide gate plate, first, 90 parts by weight of sintered alumina having a particle size of 3.0 mm or less, which is a refractory aggregate, and a particle size of 75 μm. Graphite having a secondary fiber length of 5 mm in which the secondary fiber diameter is changed as shown in Table 1 to 100 parts by weight of a main material composed of 8 parts by weight of the following carbon powder and 2 parts by weight of metallic silicon powder having a particle size of 75 μm or less 3 parts by weight of a high-quality fiber bundle was added together with 6 parts by weight of a phenol resin as a binder, kneaded by a conventional method, molded at a pressure of 2000 kg / cm ² , and fired in a reducing atmosphere at a temperature of 1400 ° C. To obtain 40 × 40 × 150 mm test pieces. The apparent porosity, bulk density, compressive strength, bending strength at room temperature and 1400 ° C. of each of the obtained test pieces are shown in Table 1, respectively. In addition, spalling test (test piece 1400
After heating for 10 minutes in an electric furnace at a temperature of ° C, it is put into water. ) Subsequent room temperature bending strength (after the spalling test, the test piece was cooled, dried, and measured) and corrosion resistance (in a molten steel melted at a temperature of 1600 ° C. in a high frequency induction furnace, the test piece was placed for 1 hour. The reduction in the cross-sectional area of the melted portion after immersion was shown as a ratio when the melt loss of Comparative Example 3 described later was set to 100. The smaller the value, the smaller the melt loss.) The results are shown in Table 1.

[0007]

[Table 1]

As can be seen from Table 1, as the secondary fiber diameter increases, the fibers do not become entangled with each other and the filling property is not deteriorated, so that the porosity is low and the density is high. Although the compressive strength also increases with this, the bending strength, which is most expected for the effect of the fiber addition, is the highest at both room temperature and 1400 ° C. when the secondary fiber diameter is 0.3 mm. Also, the bending strength after the spalling test is highest when the secondary fiber diameter is 0.3 mm. From the above, in order to improve the spalling resistance or the bending strength at high temperature (hot), the secondary fiber diameter is 0.05 to 1.0.
It is preferable that the diameter is 0.2 mm, most preferably the secondary fiber diameter is about 0.3 mm, and when the secondary fiber diameter is 2 mm, the fibers fly out from the polished surface due to the polishing process and become defective.

Examples 4 to 6 and Comparative Examples 3 to 4 100 parts by weight of the same main material as in Examples 1 to 3 were used, but the addition amount was changed as shown in Table 2, the secondary fiber diameter was 0.3 mm, and the secondary fiber diameter was 0.3 mm. After adding a graphite fiber bundle having a next fiber length of 5 mm together with 6 parts by weight of phenol resin, each test piece of 40 × 40 × 150 mm was obtained through the same steps as in Examples 1 to 3. The apparent porosity and other physical properties of the obtained test pieces and the state of the polished surface of the plate are shown in Table 2.

[0010]

[Table 2]

As can be seen from Table 2, the porosity is high, the density is low, the compressive strength is low, and the room-temperature bending strength is low as the amount of the fiber bundle added increases. However, 14
The bending strength at a temperature of 00 ° C. and the bending strength after the spalling test are the highest when the addition amount of Example 5 is 5 parts by weight. From the above, in order to improve the spalling resistance or the bending strength at high temperature, the addition amount of the fiber bundle is 0.2 to 8
It can be seen that the amount is preferably about 5 parts by weight, and most preferably the amount added is around 5 parts by weight.

Example 7, Comparative Example 5 In Example 7, 100 parts by weight of a main material composed of 98 parts by weight of sintered alumina having a particle size of 3 mm or less and 2 parts by weight of metallic silicon powder having a particle size of 75 μm or less was used. 3 parts by weight of the graphite fiber bundle similar to 2 was added together with 6 parts by weight of phenol resin, while Comparative Example 5 added 6 parts by weight of phenol resin to 100 parts by weight of the same main material as in Example 7. , 40 × 40 × 15 through the same steps as in Examples 1 to 3.
Each test piece of 0 mm was obtained. The apparent porosity and other physical properties of the obtained test piece and the state of the polished surface of the plate are shown in Table 3, respectively.

[0013]

[Table 3]

As can be seen from Table 3, Example 7 in which the main material does not contain carbon powder has a slightly lower strength than Example 2 in which the main material contains carbon powder. The bending strength at high temperature and the bending strength after the spalling test are superior to those of Comparative Example 5 in which the fiber bundles were not added. From the above, it is possible to increase the bending strength and spalling resistance at high temperature by adding a fiber bundle, and the bending strength at high temperature due to the inclusion of carbon powder in the main material. It can be seen that the spalling resistance can be further enhanced.

Examples 8 to 9 and Comparative Examples 6 to 7 Graphite having a secondary fiber diameter of 0.3 mm in which 100 parts by weight of the same main material as in Example 1 was used and the secondary fiber length was changed as shown in Table 3 After adding 3 parts by weight of the high-quality fiber bundle together with 6 parts by weight of the phenolic resin, the same steps as in Examples 1 to 3 are carried out to obtain 40 × 40
Each test piece of × 150 mm was obtained. The apparent porosity and other physical properties of each of the obtained test pieces and the state of the plate polished surface are as follows.
The results are shown in Table 3, respectively.

As can be seen from Table 3, as the secondary fiber length becomes longer, the fibers are entangled with each other and the filling property is lowered,
The density decreases. From the above, in view of the bending strength at high temperature and the bending strength after spalling, the secondary fiber length is
It turns out that 0.5-10 mm is preferable.

In the above-mentioned embodiments, the case of manufacturing a refractory applied to the slide gate plate has been described, but the present invention is not limited to this, and the refractory aggregate or metal constituting the main material is used. It can also be applied to the production of long nozzles, immersion nozzles, tundish lined refractories and other refractories for casting by changing the powder and the like.
In addition, firing is not an essential step in manufacturing a refractory, and those that are fired during use may remain unfired.

[0018]

As described above, according to the method for producing a refractory material for casting of the present invention, the carbon or graphitic fiber bundles are dispersed in the main material with good directionality without having directionality. It is possible to dramatically increase the mechanical strength in the hot state as compared with the prior art, and it is possible to prevent cracks from propagating in all directions while maintaining the corrosion resistance.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kensei Kondo No. 1 Minamito, Ogakie-cho, Kariya city, Aichi Toshiba Ceramics Co., Ltd. Kariya factory Lamix Co., Ltd. Kariya Factory

Claims (1)

[Claims] 1. A secondary fiber diameter of 0.05 to 1.0 m obtained by binding a single fiber to 100 parts by weight of a main material made of a refractory aggregate.
A method for producing a refractory for casting, characterized by adding 0.2 to 8 parts by weight of a carbon or graphite fiber bundle having m and a length of 0.5 to 10 mm, and kneading and molding.