JP3101651B2 - Nozzle for continuous casting - 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 capable of effectively suppressing narrowing and blocking of a nozzle inner hole through which molten steel passes in continuous casting of aluminum-killed steel or the like containing aluminum.

[0002]

2. Description of the Related Art A nozzle for continuous casting of molten steel is used for the following purposes. In continuous casting of molten steel, the nozzle for continuous casting has the function of injecting molten steel from the tundish into the mold.At this time, oxidation of the molten steel due to contact with air is prevented, the scattering of molten steel is prevented, and non-metallic It is used for the purpose of rectifying the pouring of the molten metal to prevent the material and the floating material on the mold surface from getting into the slab.

[0003] Conventionally, the material of a continuous steel nozzle for continuous casting of molten steel is mainly composed of graphite, alumina, silica, silicon carbide or the like. However, casting aluminum killed steel or the like has the following problems. I have.

In aluminum-killed steel and the like, aluminum added as a deoxidizing agent reacts with oxygen present in molten steel to form non-metallic inclusions such as α-alumina. Further, when the molten steel passes through the nozzle, it reacts with oxygen in the atmosphere, and further generates alumina. Therefore, when casting aluminum-killed steel, etc., non-metallic inclusions such as the above-mentioned alumina adhere to the surface of the inner hole of the nozzle for continuous casting, accumulate and consequently narrow the inner hole, and in the worst case, close the inner hole And make stable casting difficult. Alternatively, non-metallic inclusions such as α-alumina adhered and deposited in this manner may peel or fall off and get caught in the slab, resulting in deterioration of the quality of the slab.

[0005] In order to prevent the inner hole from being narrowed and clogged by the non-metallic inclusions such as α-alumina, the inner surface of the continuous casting nozzle which forms the inner hole is directed toward the molten steel flowing through the inner hole. A method of injecting an active gas to prevent non-metallic inclusions such as α-alumina present in molten steel from adhering and depositing on the inner surface of a continuous casting nozzle is widely used (for example, Japanese Patent Publication No. -59533).

However, the method of injecting the inert gas from the inner surface of the continuous steel casting nozzle has the following problems. That is, if the amount of the inert gas to be ejected is large, bubbles of the inert gas are caught in the slab and defects due to pinholes occur. Conversely, if the amount of the inert gas to be jetted is small, non-metallic inclusions such as α-alumina adhere to the inner hole surface of the continuous casting nozzle, accumulate and narrow the inner hole, and in the worst case, close the nozzle. .

Further, it is structurally difficult to blow an inert gas uniformly from the inner surface of the continuous casting nozzle toward the molten steel flowing through the inner hole. With the deterioration of the structure and the structure of the material, the control of the ejected inert gas becomes unstable. As a result, non-metallic inclusions such as α-alumina adhere to and accumulate on the inner surface of the continuous casting nozzle, narrowing and even closing the inner hole.

It is considered that nozzle blockage due to nonmetallic inclusions, particularly nozzle blockage due to alumina (Al ₂ O ₃ ) inclusions, occurs as follows. That is, (1) Aluminum in steel is oxidized by the entrainment of air passing through the refractory joint and the refractory braid, and is generated by reduction of silica in the refractory containing carbon.
O supplies oxygen and alumina is produced. (2) The alumina diffuses and aggregates to form alumina inclusions. (3) Further, graphite and carbon disappear on the inner hole surface of the nozzle, the inner hole surface becomes uneven, and alumina inclusions are easily deposited.

On the other hand, as a countermeasure from the material side, SiC, Si ₃
Nozzles have been proposed in which non-oxide raw materials such as N ₄ , BN, ZrB ₂ , and Sialon are added to alumina-graphite, or nozzles made of the same (for example, Japanese Patent Publication No. 61-381).
No. 52).

However, when the above raw materials are added to the commonly used alumina-graphite, it is not practical unless added in a large amount, since the effect of preventing adhesion is not recognized and the corrosion resistance is deteriorated. Also, when a nozzle is made only from a non-oxide raw material, the effect can be expected, but it is not suitable for practical use because of the raw material and manufacturing costs.

Further, an oxide raw material containing CaO (Ca
O · ZrO ₂ , CaO · SiO ₂ , 2CaO · SiO ₂
Etc.) produce a low-melting-point substance by a reaction between CaO and Al ₂ O ₃ , and therefore a nozzle made of a graphite-CaO-containing oxide raw material has also been proposed (for example, Japanese Patent Publication No. Sho 62-56101).
No.).

However, the reactivity of CaO and Al ₂ O ₃ is susceptible to the influence of the molten steel temperature conditions at the time of casting, a low melting point substance is not generated, and a large amount of Al ₂ O ₃ inclusions are contained in the steel. In this case, the CaO content cannot be sufficiently contained in terms of spalling resistance and corrosion resistance. Further, among the aggregates flowing out of the material into the molten steel, ZrO ₂ has a high specific gravity and therefore has a small floating effect, and does not float as slag.

[0013]

SUMMARY OF THE INVENTION The present invention forms a glass layer on the inner surface of a nozzle during use to prevent air from passing through a refractory, prevent the formation of alumina,
Continuous casting that suppresses the deposition and adhesion of alumina inclusions on the nozzle bore surface by smoothing the structure of the nozzle bore surface, prevents the bore from becoming narrower, and further prevents clogging, and enables stable casting. The purpose of the present invention is to provide a nozzle.

[0014]

According to a first aspect of the present invention, a surface portion of an inner hole of a continuous casting nozzle which is in contact with molten steel is mainly composed of Al ₂ O ₃ or Al ₂ O ₃ and has a melting point of 1800 ° C. or more. Is a composition comprising 15 to 60% by weight of an aggregate, 1 to 10% by weight of silicon carbide, and a balance composed of rubble stone.

According to a second aspect of the present invention, the inner surface layer of the continuous casting nozzle which is in contact with molten steel is mainly composed of alumina (Al ₂ O ₃ ) or alumina (Al ₂ O ₃ ) and has a melting point of 18%.
15 to 60% by weight of aggregate at 00 ° C or more, and 1 to 1% of silicon carbide
A nozzle for continuous casting of molten steel, characterized in that a binder is added and kneaded to a composition consisting of 10% by weight, the balance being lozenge, molded and fired in a non-acidic atmosphere.

According to a third aspect of the present invention, the rock stone has a particle size of 250 μm.
m is set to 60% by weight or less of the total mixing ratio of the raw stone, and is a nozzle for continuous casting of molten steel.

According to a fourth aspect of the present invention, there is provided a nozzle for continuous casting of molten steel, characterized in that the rock is mainly composed of pyrophyllite (Al ₂ O ₃ .4SiO ₂ .H ₂ O).

A fifth invention is a nozzle for continuous casting of molten steel, characterized in that the rock is calcined at 800 ° C. or higher to eliminate water of crystallization.

A sixth invention is a nozzle for continuous casting of molten steel, wherein the binder is a thermosetting resin.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The most remarkable point in the present invention is that rhoite and silicon carbide coexist as main components of a nozzle refractory. That is, in the coexistence of silicon carbide, the boulder is apt to develop a blowing phenomenon, and can suppress the entrainment of air through the refractory structure even at a low temperature, and at the same time, it is often blended with a conventional nozzle. Is that no graphite is blended. Graphite reacts with silica contained in the refractory as follows when the nozzle is used.

SiO ₂ (s) + C (s) = SiO (g) + CO (g) 3SiO (g) + 2Al = 2Al ₂ O ₃ (s) + 3Si 3CO (g) + 2Al = 2Al ₂ O ₃ (s) + 3C

By the above reaction, silica is decomposed and SiO 2 is decomposed.
(G) and CO (g) are generated, serve as an oxygen supply source into the steel, and react with Al in the steel to generate Al ₂ O ₃ . However, in the case of loasite, even in the presence of oxygen in the molten steel, the particles of the roasite do not decompose and pyrophyllite (Al ₂ O ₃ .4SiO ₂ .H ₂ O), which is the main mineral of the loasite, etc. SiO ₂ of is stable. This point was clarified from the fact that a briquette made of lozenge, silicon carbide, resin powder, and carbon fine powder was prepared, embedded in a breath, and observed under a microscope after heat treatment at 1500 ° C. for 24 hours.

The conventional material to which about 10% by weight of graphite is added has a thermal conductivity of 9.8 (kcal / m / hr / ° C.).
On the other hand, the material to which the graphite of the present invention is not added has a low value of 3.6 (kcal / m / hr / ° C.), is excellent in heat insulation, and has a non-metallic property such as adhesion of metal and α-Al ₂ O _3. It is difficult for metal inclusions to precipitate.

Furthermore, the nozzle including a conventional graphite if graphite is oxidized and reduced smoothness of the inner bore surface, since the molten steel flowing nozzle hole is turbulent, α-Al ₂ O _3, etc. Non of Metal inclusions will be deposited. However, when graphite is not added, the smoothness does not decrease, so that the inner surface of the nozzle is smooth, and nonmetallic inclusions such as α-Al ₂ O ₃ do not deposit.

The semi-molten temperature of the rock is about 1500 ° C. and melts on the working surface in contact with the molten steel to form a glass film. Therefore, the structure of the working surface is smoothed, and the refractory structure is formed by the glass film. The entrainment of air through.

In this respect, 1500 points in an oxidizing atmosphere
° C. × 1hr alumina was added graphite after heat treatment - to permeability of roseki material is about 6.5 × 10- ² darcy,
Other conditions are the same and 1500 ° C for the material without graphite
× ventilation rate after heat treatment at 1hr is 1.0 × 10- ⁵ dar
cy and became clear from the decrease in the air permeability.

Further, the heat treatment temperature was lowered to 1450 ° C. × 1
Alumina-Rhoite material with heat permeability of 10 after heat treatment at hr
× 10- ⁴ darcy such whereas, S other conditions identical
iC small as 1.0 × 10- ⁴ darcy is a material obtained by adding, since the permeability is lowered, blow phenomenon also roseki at low temperature is expressed and entrainment of air through the refractory tissue Can be suppressed.

When used as a continuous casting nozzle,
In order to positively form a glass film on the inner surface and maintain the spalling resistance, the mixing weight ratio of the rock is desirably 30% by weight or more, and if it exceeds 84% by weight, softening deformation occurs. It is desirable that the content be 84% by weight or less, because the corrosion resistance to molten steel is deteriorated. This amount is the balance of the other components.

The compounding ratio of silicon carbide is desirably 1% by weight or more in order to positively generate the blowing phenomenon of the rock, and if it exceeds 10% by weight, melting is remarkable and melting loss is increased. % Is desirable.

Al ₂ O ₃ or Al ₂ O as an aggregate
Aggregate (for example, MgO.Al ₂ O ₃ ) containing ₃ as a main component and having a melting point of 1800 ° C. or more is blended in an amount of 15 to 60% by weight. The aggregate has an effect of imparting strength and corrosion resistance to the nozzle as a molded body.

Any of three types of loasite can be used: pyrophyllite loasite, kaolinite loasite, and sericite loasite. When used, the inner hole surface that comes into contact with molten steel becomes semi-molten, Considering the formation of the glass layer and the erosion resistance of the molten steel, pyrophyllite-type rock with a fire resistance of SK 29 to 32 is the best. Kaolinite has a fire resistance of S
K33-36 is high, and conversely, sericite lozenge is low in fire resistance SK26-29.

The reason for using a calcite that has been calcined at 800 ° C. or higher to eliminate water of crystallization is as follows. This is because water is released at 500 to 800 ° C., and at this time, the coefficient of thermal expansion becomes abnormally large, and cracks may be formed in the molded body.

If the average particle size of the rock is less than 250 μm and exceeds 60% of the weight ratio of the raw stone, structural defects such as lamination during molding are liable to occur, and when used as a continuous casting nozzle. In this case, since the softening deformation of the rock particles is likely to occur, the content is preferably 60% or less.

Pyrophyllite (Al ₂ O ₃ .4SiO)
_A refractory composition comprising 65 to 90% by weight of a rock mainly composed of ₂ · H ₂ O) and 15 to 60% by weight of an aggregate mainly composed of Sic, Al ₂ O ₃ or Al ₂ O _3. Is
No decomposition of the low stone particles, not a source of oxygen into the steel, such as SiO _2. The semi-melting temperature of the rock is 1
500 ° C. close to the casting temperature of the molten steel before and after, since forming the glass coating layer in operation surface in contact with molten steel, to smooth the operation surface tissue, and to suppress the entrainment of air through the refractory tissue, Al ₂ It has the effect of suppressing the adhesion of O ₃ and metal.

In order to form a composition containing the above-mentioned rock stone and aggregate into a nozzle, a thermosetting resin such as a phenol resin or a furan resin is used as a binder in an amount of 5 to 15%.
% By weight, formed into a nozzle shape, and fired. This molding method is desirable in that the CIP (Cold Isostatic Pressing) process uniformly compresses the compact. Further, the firing temperature is desirably about 1000 ° C. to 1300 ° C.
Further, the firing atmosphere is more desirably a reducing atmosphere than an oxidizing atmosphere, that is, a non-oxidizing atmosphere, since the compounded resin is not oxidized.

Next, the nozzle for continuous casting of molten steel according to the present invention will be described with reference to the drawings. FIG. 1 shows an example of a vertical cross section of a continuous casting immersion nozzle according to the present invention. The continuous casting nozzle 10 is disposed between the tundish and the mold, and is used as an immersion nozzle for injecting molten steel from the tundish into the mold.

As shown in FIG. 1, the continuous casting nozzle 10
The surface layer 2 of the inner hole 1 through which the molten steel flows is formed of a refractory having the above-described chemical composition. The portion 3 other than the surface layer portion is made of conventional alumina-graphite.

The dimensions of the continuous casting nozzle are, for example, about 1 m in total length, about 6 cm in inner hole diameter, 16 cm in outer diameter, and about 5 cm in wall thickness. The thickness of the refractory according to the present invention is about 2 to 15 mm. Note that this dimension is an example and does not limit the present invention, and varies depending on the dimension of the cast slab.

FIG. 2 shows an embodiment of a nozzle in which the entire part immersed in the molten steel in the mold is made of the refractory of the present invention.
In either case, the alumina that normally closes the nozzle bore accumulates in the bore below the nozzle. The immersion nozzle of the present invention suppresses non-metallic inclusions such as alumina present in molten steel from adhering to and depositing on the surface portion 2 of the inner hole 1. Next, the present invention will be described with reference to examples.

[0040]

EXAMPLE 1 5 to 1 were added to 9 mixtures having different component compositions.
0% by weight of a powder and a solution of a phenolic resin are added, and the resulting mixture is mixed and kneaded to obtain a composition of 10%.
It was baked at a temperature between 00 ° C and 1200 ° C. The following molded articles were prepared from the nine compositions.

The first compact (hereinafter, referred to as "compact 1") has a size of 30 mm.times.30 mm.times.2 for testing the amount of nonmetallic inclusions such as alumina and the corrosion resistance to molten steel.
It is a compact having a size of 30 mm.

The second molded body (hereinafter referred to as “molded body 2”) has a size of 50 mmφ × 20 mm for measuring the air permeability.
And a third molded body (hereinafter, referred to as a third molded body)
It is referred to as "mold 3". ) Indicates an outer diameter of 100 mm, an inner diameter of 60 mm and a length of 250 mm for testing spalling resistance.
It is a molded body having a dimension of mm. Each of the obtained molded bodies was reduced and fired at a temperature in the range of 1000 ° C. to 1200 ° C. to prepare refractory samples 1 to 9.

The physical properties (porosity and porosity) of each of the above-mentioned samples 1 to 5 of the present invention (hereinafter, referred to as “sample of the present invention”) and samples 6 to 9 (hereinafter, referred to as “comparative samples”). The bulk density is shown in Table 1 shown in Fig. 3. Samples 1 to 5 and Comparative Samples 6 to 9 of the above-mentioned molded article 3 of the present invention were each heated in an electric furnace at a temperature of 1500 ° C for 30 minutes, and The spalling resistance was investigated by rapid cooling with water, and the results are shown in Table 1 shown in FIG.

The above-mentioned samples 1 to 5 of the molded article 1 of the present invention and comparative samples 6 to 9 each contain aluminum containing 0.02 to 0.05% by weight of aluminum.
It was immersed in molten steel at a temperature of 00 ° C. for 180 minutes to examine the erosion rate (%) and the amount of nonmetallic inclusions such as alumina. The results are shown in Table 1 shown in FIG.

The samples 1 to 5 and the comparative samples 6 to 9 of the molded article 2 of the present invention were each heated in an electric furnace at a temperature of 1450 ° C. for 60 minutes, and after cooling, the air permeability was measured. Table 1 shows the test results as shown in FIG.

As is clear from Table 1, the sample of the present invention has excellent spalling resistance and does not adhere to nonmetallic inclusions such as alumina despite its low erosion rate. It is possible to effectively suppress the narrowing of the inner hole of the casting nozzle and, further, the blockage.

Further, since the sample of the present invention has a small air permeability, air entrapment through a refractory can be suppressed during actual use, so that the amount of alumina adhered was extremely small. On the other hand, in Sample 6 for comparison, although the amount of adhered alumina is small due to the high content of the rock, it is clear that the amount of erosion to molten steel is large.

In Comparative Sample 7, the brothability of the rock was promoted despite the low content of the rock, due to the high content of silicon carbide, and the alumina adhesion Is small, but the amount of erosion to molten steel is large. Sample 8 contains silicon carbide, but has a high alumina content and a low content of rubble, so that the air permeability is large and the alumina adhesion amount is large. Also, the spalling resistance is remarkably inferior.

In Comparative Sample 9, graphite,
Although it is composed of rock and Al ₂ O ₃ , it contains graphite, so when the molten steel temperature is as low as 1520 ± 10 ° C., the amount of alumina adhered was slightly large, and the amount of metal ingot was also large.

[0050]

As described above, according to the nozzle for continuous casting of molten steel of the present invention, the inner hole of aluminum-killed steel is narrowed and closed by non-metallic inclusions such as alumina without deteriorating the refractory structure. , And casting was stabilized.

Using the nozzle of the present invention, one charge 3
When 00 tons of low carbon aluminum killed steel was cast using a two-strand continuous slab caster, 5 to 7 charges could be cast without nozzle closure. In addition, when casting was performed using a conventional nozzle, when 2 to 4 charge casting was performed, the nozzle was closed and the casting was interrupted.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a nozzle provided with a refractory according to the present invention on a surface portion of a nozzle inner hole that comes into contact with molten steel.

FIG. 2 is a cross-sectional view of a nozzle provided with a refractory according to the present invention in a lower part of a nozzle (a part immersed in molten steel) in contact with molten steel.

FIG. 3 is a table showing the composition and physical properties of the present invention and a comparative example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 inner hole 2 inner hole surface layer 3 part other than surface layer 10 continuous casting nozzle

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-8-215811 (JP, A) JP-A-7-51819 (JP, A) JP-A-6-254664 (JP, A) JP-A-5-218 JP-A-319918 (JP, A) JP-A-63-112057 (JP, A) JP-A-10-24351 (JP, A) JP-A-51-33725 (JP, A) JP-A-2-172859 (JP, A) JP-A-57-205377 (JP, A) JP-A-63-203666 (JP, A) JP-A-57-56377 (JP, A) JP-A-10-128507 (JP, A) JP-A-10-118749 (JP, A) JP-A-10-166115 (JP, A) JP-A-10-166116 (JP, A) JP-A-10-166117 (JP, A) JP-A-10-202349 (JP, A) ( 58) Field surveyed (Int. Cl. ⁷ , DB name) B22D 11/10 330 C04B 35/18 B22D 41/50

Claims (6)

(57) [Claims] An inner surface layer portion of a continuous casting nozzle which is in contact with molten steel is mainly composed of Al ₂ O ₃ or Al ₂ O ₃ , and 15 to 60% by weight of an aggregate having a melting point of 1800 ° C. or more; A nozzle for continuous casting of molten steel, wherein the composition is composed of silicon carbide in an amount of 1 to 10% by weight and the balance being roite. 2. The continuous casting nozzle, wherein the inner surface layer of the inner hole which comes into contact with molten steel is mainly composed of Al ₂ O ₃ or Al ₂ O ₃ , and has a melting point of 1800 ° C. or more of 15 to 60% by weight of aggregate. A nozzle for continuous casting of molten steel, wherein a binder is added and kneaded to a composition comprising 1 to 10% by weight of silicon carbide and the remainder being rubble, molded and fired in a non-acidic atmosphere. 3. The nozzle for continuous casting of molten steel according to claim 2, wherein the rock stone has a particle size of 250 μm or less and 60% by weight or less of a total mixing ratio of the rock stone. 4. The method according to claim 1, wherein the rock is pyrophyllite (Al ₂
O ₃ · 4SiO continuous casting nozzle according to any one of claims 1 _to 3, ₂ · H ₂ O) and is characterized in that a main component. 5. The nozzle for continuous casting of molten steel according to claim 2, wherein said rock is calcined at 800 ° C. or higher to eliminate water of crystallization. 6. The nozzle for continuous casting of molten steel according to claim 2, wherein the binder is a thermosetting resin.