JP3524668B2 - Nozzle refractories for continuous casting - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a nozzle refractory for continuous casting.

[0002]

2. Description of the Related Art A conventional refractory for continuous casting nozzles is formed as a composite material in which an alumina graphite material is a main material and a powder line portion, a fitting portion and the like are reinforced by a zirconia graphite material and a magnesia graphite material.

These carbon-containing refractories generally use natural scaly graphite as a carbon source. However, the flake graphite is 30
Since it does not sinter below 00 ° C., it cannot be expected to improve the strength due to the sintering of scaly graphite particles or the sintering of scaly graphite particles and other aggregate particles. Therefore, the strength of the refractory material depends on how much carbon bonds are formed due to the binder.

As the binder containing carbon-containing refractory, liquid phenol resin or powder resin having a carbon yield of 40% or more, pitch binder having a carbon yield of 50% or more are generally used.

[0005]

However, in the step of kneading the liquid binder or powder binder and the aggregate particles such as alumina, zirconia or magnesia or the fine powder such as silicon carbide, silica, graphite powder, etc. It is very difficult to control the surface of the particles so that they are uniformly wet with the liquid binder or the powder binder.

When the wet state is not uniform, the strength is lowered and abnormal melting damage occurs in the uneven portion of the binder.

Further, in the case of a digestible material such as magnesia, the moisture contained in the liquid binder causes digestion in the granules of the magnesia aggregate, and the material strength remarkably decreases due to volume expansion and the like.

On the other hand, in the unfired magnesia-carbon brick described in JP-A-2-311358, 0.5 mm of magnesium-aluminum alloy powder coated with pitch is used to facilitate handling of magnesium or magnesium-aluminum alloy. It is configured to contain 10%.

Further, Japanese Patent Laid-Open No. 6-293565 discloses that
In order to obtain a homogeneous and dense Si-SiC material, a method for producing a Si-SiC composite ceramic is disclosed, in which a compact is formed from SiC powder coated with mesophase-containing pitch, and the compact is fired and then impregnated with Si.

However, the unfired magnesia-carbon brick disclosed in JP-A-2-311358 was proposed for the purpose of facilitating the handling of magnesium or a magnesium-aluminum alloy, and the brick itself has a coefficient of thermal expansion. It is expensive and has problems such as cracking due to thermal shock during use, so it cannot be said to be optimal as a nozzle for continuous casting.

Further, S in Japanese Patent Laid-Open No. 6-293565
Since i-SiC composite ceramics also has a high coefficient of thermal expansion,
Since it has defects such as cracking due to thermal shock, it cannot be said to be optimal as a continuous casting nozzle.

In view of the above problems of the prior art, the present invention provides a continuous casting nozzle refractory which is suitable for various nozzles for continuous casting having a small apparent porosity, a sufficient strength and a large corrosion resistance. Is intended to provide.

[0013]

[0014]

Means for Solving the Problems The first invention of the present application is 100
Particle size 7 with the surface coated with pitch that softens at ~ 300 ° C
40 to 90% by weight of a zirconia raw material of 4 to 1000 μm is used as an aggregate, and at least one of silica, graphite powder and calcia is used as another refractory raw material having a particle size equal to or smaller than that of the aggregate particles, and a resin is used as a binder. Using a binder
A gist is a nozzle refractory for continuous casting, which has a structure in which a pitch is carbon-bonded by firing in a reducing atmosphere.

In the second invention of the present application, a particle size of 74 to 3000 μm having a surface coated with a pitch that softens at 100 to 300 ° C.
40 to 90% by weight of the magnesia raw material of
At least one of silicon carbide, silica, and graphite powder is used as another refractory material having a particle size equal to or less than that of the aggregate particles, and a resin binder is used as the binder, and the pitch is carbon-bonded by firing in a reducing atmosphere. The gist is a nozzle refractory for continuous casting, which is characterized by having a simplified structure.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION A nozzle refractory for continuous casting according to the present invention uses alumina, zirconia or magnesia whose surface is coated with a pitch of a binder component as an aggregate and has a particle size equal to or smaller than that of the aggregate particles. At least one of silicon carbide, silica black smoke powder, and calcia is used as a refractory material, a resin binder is added as a binder, and the pitch is carbon-bonded by firing in a reducing atmosphere. If the aggregate is alumina, 10
Bending strength of 7 MPa or more in the case of zirconia and 6 MPa or more in the case of magnesia is preferable. More preferable bending strength is 10 MPa, respectively
As described above, the pressure is 8 MPa or more and 7 MPa or more. The pitch is
What softens at 100-300 degreeC is used.

The strength of the aggregate particles can be improved by uniformly covering the surface of the aggregate particles with the pitch of the binder component, firing it in a reducing atmosphere to form carbon bonds, and dispersing the carbon bonds evenly. . The firing temperature is 400 ° C to ensure carbon bonding.
The above is preferable.

Since the pitch around the aggregate particles softened by firing fills the minute gaps in the matrix, the apparent porosity can be reduced and the corrosion resistance can be improved.

The grain size of alumina, zirconia or magnesia of the aggregate is 74 μm or more. Aggregate particle size is 74 μm
When it is less than the above range, the thickness of the coating layer of the pitch becomes larger than the particle diameter of the aggregate due to the viscosity of the pitch, which causes a problem that the corrosion resistance decreases.

The particle size of alumina and zirconia of the aggregate is 10
The particle size of magnesia is set to 00 μm or less and 3000 μm or less. This is a general upper limit of the raw materials of alumina, zirconia and magnesia used as refractory for continuous casting, and when it exceeds 1000 μm or 3000 μm, the problem that strength is extremely lowered occurs.

From this point of view, the more preferable particle size of alumina and zirconia used as the aggregate is 74 to 100.
0 μm, and the more preferable particle size of magnesia is 74-
It is 3000 μm.

The particle size is 74 to 1000 (or 300).
0) μm means a minimum particle size of 74 μm and a maximum particle size of 1
It means a continuous grain of 000 (or 3000) μm.

When an alumina raw material is used as the aggregate, its content is 30 to 80% by weight, and when a zirconia or magnesia raw material is used, the content is 40%.
Up to 90% by weight. The reason for limiting the compounding amount of the aggregate in this way is that the compounding amount is currently used as a nozzle refractory for continuous casting.

The pitch and the aggregate of alumina, zirconia or magnesia are preferably kneaded while heating at 100 to 200 ° C. This makes it possible to uniformly coat the surface of the aggregate particles.

Magnesia has digestibility, but by covering the particle surface with pitch, digestion due to water contained in the binder can be prevented.

The other refractory raw material having a particle size equal to or smaller than that of the aggregate particles according to the present invention has a particle size equal to or smaller than that of the aggregate particles, thereby sufficiently obtaining the effect of the pitch coating of the present invention. Is something that can be done.

[0027]

EXAMPLES Examples 1 to 5 and Comparative Example 1 of the present invention will be described below.
5 will be described.

Examples 1 and 2 are examples of refractory materials of continuous casting nozzle made of alumina graphite.

Alumina particles, graphite powder, silica particles, and silicon carbide were prepared at the compounding ratios shown in Table 1, and kneaded, molded, and molded.
Fired to produce a refractory.

The diameter of the alumina particles was 74 to 1000 μm. The surface of the alumina particles was coated with hard pitch and mesophase pitch with a thickness of about 0.05 μm. The coating was performed by bringing the pitch into a liquid state at a temperature of 200 ° C. or lower and kneading the aggregate raw material.
The particle size of graphite powder, silica particles, and silicon carbide compounded as fine particle raw materials are 100 to 200 μm and 88 to 297, respectively.
μm and 44 μm or less.

On the other hand, refractory materials of Comparative Examples 1 and 2 were manufactured by the same procedure except that the alumina particles were not coated with pitch.

The bending strength, kinetic elastic modulus, apparent porosity, bulk specific gravity and corrosion resistance index of the refractories of Examples 1 and 2 and Comparative Examples 1 and 2 were measured. The results are shown in Table 1. The corrosion resistance index is set to 100 in Comparative Example 1, and the larger the value, the better the corrosion resistance.

From Table 1, it can be seen that Examples 1 and 2 have a higher bending strength, a smaller apparent porosity, and a higher corrosion resistance than Comparative Examples 1 and 2.

Examples 3 to 4 are zirconia graphite-based continuous casting nozzle refractories.

Zirconia particles having a particle size of 74 to 1000 μm were used as an aggregate, and graphite powder, silica particles, and calcia were added, and a refractory material was manufactured in the same manner as in Example 1.

On the other hand, the refractory materials of Comparative Examples 3 to 4 were manufactured in the same manner except that the zirconia grains were not coated with pitch.

Similarly, the physical properties of Examples 3 to 4 and Comparative Examples 3 to 4 were measured. The results are shown in Table 2. Looking at Table 2,
It can be seen that Examples 3 and 4 have higher bending strength, smaller apparent porosity, and higher corrosion resistance than Comparative Examples 3 and 4.

Example 5 is a magnesia graphite-based continuous casting nozzle refractory material.

A magnesia grain having a grain size of 74 to 3000 μm was used as an aggregate, and graphite powder, silica grain, and silicon carbide were added, and a refractory was manufactured in the same manner as in Example 1.

On the other hand, the refractory of Comparative Example 5 was manufactured in the same manner except that the zirconia grains were not coated with pitch.

Similarly, the physical properties of Example 5 and Comparative Example 5 were measured. The results are shown in Table 3. Looking at Table 3, Example 5
It can be seen that No. 4 has a larger bending strength, a smaller apparent porosity, and a higher corrosion resistance than Comparative Example 5. In Comparative Example 5, the digestion phenomenon was found in the magnesia grains after firing.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3]

[0045]

The nozzle refractory for continuous casting according to the present invention has a small apparent porosity, a sufficient strength, and a high corrosion resistance, so that the service life can be greatly improved.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI C04B 35/48 C04B 35/10 G (72) Inventor Sei Takigawa 1st Nanto, Ogakie-cho, Kariya city, Aichi Toshiba Ceramics Co., Ltd. Kariya factory (56) References JP-A-7-277838 (JP, A) JP-A-7-303958 (JP, A) JP-A-2-268953 (JP, A) JP-A-58-151368 (JP, A) Kai 56-14060 (JP, A) JP 2-172862 (JP, A) JP 5-319916 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B22D 11 / 10 330 B22D 41/54 C04B 35/00 C04B 35/043 C04B 35/103 C04B 35/48

Claims (2)

(57) [Claims] 1. A zirconia raw material having a particle size of 74 to 1000 μm and having a particle size of 74 to 1000 μm and having a particle size of 74 to 1000 μm, which is softened at 100 to 300 ° C., is used as an aggregate. As raw material, silica, graphite powder,
A nozzle refractory for continuous casting, characterized in that at least one kind of calcia is used, a resin binder is used as a binder, and the pitch is carbon-bonded by firing in a reducing atmosphere. 2. A 40-90% by weight magnesia raw material having a particle size of 74-3000 μm, coated on the surface with a pitch that softens at 100-300 ° C., is used as an aggregate, and another refractory having a particle size equal to or less than that of the aggregate particle is used. As raw materials for silicon carbide, silica,
A nozzle refractory for continuous casting, characterized in that at least one kind of graphite powder is used, a resin binder is used as a binder, and the pitch is carbon-bonded by firing in a reducing atmosphere.