JP3476312B2 - Nozzle for continuous casting of zirconia-graphite - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous casting nozzle used between a ladle and a tundish, or between a tundish and a mold in a continuous casting process for steel or the like, and more particularly to a zirconia-graphite continuous casting nozzle. Is.

[0002]

2. Description of the Related Art Conventionally, a continuous casting nozzle such as a long nozzle or a dipping nozzle has been used between a ladle and a tundish or between a tundish and a mold in a continuous casting process of steel or the like. When these nozzles are used, the molten steel does not come into contact with air, so that oxidation of the molten steel can be prevented and good casting can be performed. Incidentally, in the nozzle for continuous casting, zirconia-graphite is generally used in a portion in contact with the molten slag covering the molten metal surface.

This continuous casting nozzle is made of alumina (Al
₂ O ₃ ), zirconia (ZrO ₂ ), silica (SiO
₂ ), magnesia (MgO), mullite (3Al ₂ O ₃
.2SiO ₂ ) or other oxide raw material, or silicon carbide (S
iC), a carbide raw material such as boron carbide (B ₄ C), or a boride raw material such as zirconium boride (ZrB ₂ ), and a metal such as silicon (Si) is required. It is composed of fire-resistant aggregate and graphite.

[0004]

By the way, the conventional continuous casting nozzle contains carbon as described above,
In addition, the structure is composed of carbon bonds resulting from the solidification of the binder. Therefore, oxidation (decarburization)
As a result, structural deterioration occurs, and this structural deterioration causes strength deterioration, corrosion resistance deterioration, thermal shock resistance deterioration, etc., and the service life of the continuous casting nozzle is shortened. In order to prevent this, conventionally, additives such as silicon as described above have been added to prevent oxidation of carbon, that is, deterioration of the structure. However, even if the above-mentioned additives such as silicon are added, the oxidation cannot be completely prevented, and the effective temperature range for preventing the oxidation of carbon is determined by the additives. There is a technical problem that carbon is oxidized depending on the use temperature of.

On the other hand, a so-called zirconia-graphite casting nozzle composed of zirconia (ZrO ₂ ) and graphite is
Although it has better corrosion resistance than other casting nozzles, it has technical problems such as deterioration of corrosion resistance due to carbon oxidation as described above.

The present invention has been made to solve the above technical problems, and provides a continuous casting nozzle for zirconia-graphitic continuous casting, which has dramatically improved corrosion resistance. The purpose is.

[0007]

The zirconia-graphite continuous casting nozzle according to the present invention is a zirconia-graphite continuous casting nozzle having 1 to 40% by weight of zirconium boride and 1 to 10% by weight. Of aluminum nitride. Further, the zirconia-graphite continuous casting nozzle according to the present invention produces aluminum nitride by adding metallic aluminum in an amount of 1 to 10% by weight and firing it in a nitrogen atmosphere to produce 1 to 10% by weight of aluminum nitride. It is desirable to contain. Further, in the zirconia-graphite continuous casting nozzle according to the present invention, it is desirable to add 1 to 10% by weight of metallic aluminum and fire it in a nitrogen atmosphere at 800 ° C or higher and lower than 1200 ° C to generate aluminum nitride. .

In the zirconia-graphite continuous casting nozzle according to the present invention containing 1 to 40% by weight of zirconium boride and 1 to 10% by weight of aluminum nitride, the thermal shock resistance, Improvement in corrosion resistance was observed. In particular, it was confirmed that the corrosion resistance was dramatically improved.

Further, it was confirmed that the same effect as described above can be obtained by using metallic aluminum instead of aluminum nitride, setting the atmosphere during firing to a nitrogen atmosphere, and interspersing aluminum nitride in the material.

Here, if the amount of aluminum nitride or metallic aluminum added is less than 1% by weight, the effect of addition is not remarkable. On the other hand, when the addition amount of aluminum nitride or metallic aluminum exceeds 10% by weight, the relative amount of zirconia decreases, which causes deterioration of corrosion resistance. Therefore, the addition amount of aluminum nitride or metallic aluminum is preferably in the range of 1 to 10% by weight.

The addition amount of zirconium boride is 1 to
A range of 40% by weight is desirable. If less than 1% by weight,
This is because the effect of improving the corrosion resistance does not appear remarkably, and when it exceeds 40% by weight, the thermal shock resistance is greatly reduced. Further, since zirconium boride is expensive as a refractory raw material, it is not desirable to use a large amount thereof. Therefore, the addition amount of zirconium boride is preferably in the range of 1 to 40% by weight.

Further, the firing atmosphere is a nitrogen atmosphere,
In order to generate aluminum nitride, it is preferable to perform firing at a temperature of 800 ° C or higher and lower than 1200 ° C. The temperature must be 800 ° C or higher because the temperature must be higher than the temperature at which aluminum metal is nitrided and aluminum nitride is formed. Further, at 1200 ° C. or higher, in the zirconia-graphite, the destabilization decrease occurs in which the stabilizer of the partially stabilized zirconia contained as a raw material is released, which causes an adverse effect on the characteristics of the material. Therefore, the preferable firing temperature is 800
C. or higher and lower than 1200.degree.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION A zirconia-graphite continuous casting nozzle is manufactured, and a thermal shock resistance coefficient and a corrosion resistance index are determined,
Each nozzle was compared and examined. Here, the thermal shock resistance coefficient is represented by the following equation: thermal shock resistance coefficient = bending strength / (thermal expansion coefficient × dynamic elastic modulus), and the larger the value, the better the thermal shock resistance. I can say. The corrosion resistance index is evaluated by immersing it in molten steel using a high-frequency induction furnace, and is calculated by the melt loss ratio when a certain specific nozzle is 100. The larger this number is,
It can be said that it has excellent corrosion resistance.

Next, Table 1 shows the blending ratio of each Example and Comparative Example. Comparative Example 1 is used as a basic composition, and aluminum nitride or metallic aluminum is added at an external ratio. In this basic formulation (Comparative Example 1), 5% by weight of zirconium boride is incorporated. The amount of aluminum nitride added was increased to Example 1 (3% by weight), Example 2 (7% by weight), and Comparative Example 2 (12% by weight). The amount of metallic aluminum added was increased to Example 3 (3% by weight), Example 4 (7% by weight), and Comparative Example 3 (12% by weight). It should be noted that Comparative Examples 2 and 3 are combinations of the same raw materials as those in Examples, but the amount of aluminum nitride or metallic aluminum added is 12% by weight, which is outside the range of the present invention.

Next, the procedure for producing the specimens of the examples and comparative examples shown in Table 1 will be explained. After kneading the raw materials, they were compacted by a hydrostatic press with a compacting pressure of 1.5 ton / cm ² and nitrogen. A sample was obtained by firing at 1000 ° C. in an atmosphere.

[0016]

[Table 1]

As shown in Table 1 above, the thermal shock resistance coefficient and the corrosion resistance are improved in Examples 1, 2 and 3 as compared with Comparative Example 1 which is the basic composition. In particular, it was confirmed that the corrosion resistance was dramatically improved. On the other hand, in Comparative Examples 2 and 3 in which the addition amount of aluminum nitride or metallic aluminum was increased and 12 wt% was added, the corrosion resistance index was lower than the basic composition, and the thermal shock resistance coefficient due to each addition,
It was confirmed that the effect of improving the corrosion resistance did not appear.

Next, trial production was carried out in which the amount of aluminum nitride added was kept constant and the amount of zirconium boride added was changed. Table 2 shows the respective examples and comparative examples. Zirconium boride is added by substituting partially stabilized zirconium. That is, using Comparative Example 4 as the basic composition,
The amount of zirconium boride added is increased in Example 5 (3% by weight), Example 6 (15% by weight), Example 7 (30% by weight), and Comparative Example 5 (45% by weight). Instead, the increased amount of zirconium boride is used in each formulation to reduce the amount of partially stabilized zirconia added. Comparative Example 5 is the same combination of raw materials as those in Examples, but the amount of zirconium boride added is 45% by weight, which is outside the range of the present invention. The procedure for producing the specimens of the examples and comparative examples shown in Table 2 is the same as the trial production procedure for each formulation in Table 1.

[0019]

[Table 2]

As shown in Table 2 above, the corrosion resistance of each of Examples 5, 6, 7 and Comparative Example 5 is dramatically improved as compared with Comparative Example 4 which is the basic composition. However, in Comparative Example 5, the thermal shock resistance was significantly reduced compared to the basic formulation (Comparative Example 4), and it was confirmed that the thermal shock resistance required for the continuous casting nozzle was not satisfactory. It was

From the above, by adding zirconium boride and aluminum nitride or metallic aluminum to the zirconia-graphite, the thermal shock resistance and corrosion resistance required as the characteristics of the nozzle for continuous casting are improved. It was confirmed that the corrosion resistance was drastically improved.

In the above example, the firing temperature was 1000 ° C. when the sample was prepared, but it may be lower or higher. As mentioned above, 1000
If the temperature is lower than ℃, the temperature should be higher than the temperature at which metallic aluminum is nitrided and aluminum nitride is formed.
Must be above 00 ° C. When the temperature is 1000 ° C or higher, the temperature is preferably lower than 1200 ° C. This is because at 1200 ° C. or higher, in the zirconia-graphite, the destabilization decrease occurs, in which the stabilizer of the partially stabilized zirconia contained as a raw material is released, and this adversely affects the properties of the material. Therefore, the preferable firing temperature is 800 ° C to 1200 ° C.

As a method of interspersing aluminum nitride in the material, aluminum nitride may be added as a raw material, or metal aluminum may be added as described above and aluminum nitride may be added by a reaction during firing. It may be generated and as a result interspersed with aluminum nitride.

[0024]

As described above, according to the invention described in claim 1, in a zirconia-graphite continuous casting nozzle, 1 to 40% by weight of zirconium boride and 1 to 1 are used.
Since it contains 0% by weight of aluminum nitride, it has an effect of suppressing carbon oxidation. As a result, it is possible to obtain a zirconia-graphite continuous casting nozzle having a high durability, which is excellent in heat shock resistance, particularly in corrosion resistance, while preventing the strength of the material from being lowered.

According to the invention described in claims 2 and 3, 1 to 10% by weight of metallic aluminum is added, and the aluminum nitride is produced by firing in a nitrogen atmosphere to produce 1 to 10% by weight. Aluminum nitride can be easily contained.

Front page continuation (72) Inventor Yoichiro Mochizuki, No. 1 Nanto, Ogakie-cho, Kariya city, Aichi Toshiba Ceramics Co., Ltd., Kariya factory (56) Reference JP-A-5-50197 (JP, A) JP-A-2-172860 ( JP, A) JP 62-202860 (JP, A) JP 8-112666 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B22D 11/10 330 B22D 11 / 10 320 B22D 41/54 C04B 35/48

Claims (3)

(57) [Claims] 1. A zirconia-graphite continuous casting nozzle comprising 1 to 40% by weight of zirconium boride and 1 to 40% by weight.
A nozzle for continuous casting of zirconia-graphite, which contains 10% by weight of aluminum nitride. 2. An aluminum nitride is produced by adding 1 to 10% by weight of metallic aluminum and firing in a nitrogen atmosphere, and contains 1 to 10% by weight of aluminum nitride. Zirconia
Graphite continuous casting nozzle. 3. Zirconia according to claim 2, characterized in that aluminum nitride is produced by adding 1 to 10% by weight of metallic aluminum and calcining in a nitrogen atmosphere at 800 ° C. or higher and lower than 1200 ° C. Graphite continuous casting nozzle.