JPH10118747A - Nozzle for continuous casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nozzle for continuous casting which is effective in preventing the clogging of the nozzle and capable of integral forming during a forming operation. SOLUTION: In a nozzle 10 for continuous casting capable of preventing the clogging of the nozzle caused by stuck alumina in continuous casting of steel, an in-nozzle hole part 11 in contact with the molten steel is made of a refractory material containing 1-10wt.% carbon, and refractory materials other than carbon are of grain size of <=420μm. The refractory material forming the in-nozzle hole part 11 is of the integrated structure which is simultaneously formed in forming the nozzle for continuous casting, and the thickness of the part is in the range of 2-12mm.

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, and more particularly to a continuous casting nozzle, such as a long nozzle or a submerged nozzle, which is effective in preventing nozzle blockage and can be integrally formed during molding.

[0002]

2. Description of the Related Art Alumina-graphite materials have been widely used as nozzles for continuous casting of steel. That is, as continuous casting nozzles, there are a long nozzle used between a ladle and a tundish, an air seal pipe, an immersion nozzle used between a tundish and a mold, and the like. From the conditions of use, the requirements for "corrosion resistance and spalling resistance to molten steel and slag" have become extremely strict. In fact, alumina-graphite materials are frequently used to meet such requirements.

When a nozzle made of an alumina-graphitic material is used, particularly when it is used for casting aluminum killed steel containing a large amount of Al in molten steel, alumina (Al ₂ O ₃ ) generated by oxidation of Al is used as a nozzle. There is a problem that the nozzle adheres to the inner wall and the nozzle is easily blocked.

[0004] Recently, continuous casting has been promoted from the viewpoint of improving productivity. However, if the nozzle is clogged due to adhesion of alumina, it becomes impossible to control the flow rate of molten steel, and it becomes difficult to continue casting. Also, during the casting, the plugging material may peel off due to the flow of the molten steel. In this case, the plugging material is mixed into the mold and is taken into the slab, which is one of the factors that cause the defect of the slab. It is with.

[0005] In general, a reaction represented by the following formulas (1) to (3) occurs between Al in molten steel and a refractory constituting the immersion nozzle, and alumina adheres to the nozzle. it seems to do. - formula _{(1) ......... SiO 2 (s} ) + C (s) = SiO (g) + CO (g) · formula (2) ......... 3SiO (g) + 2Al = Al 2 O 3 (s) + 3Si · formula (3) ......... 3CO (g) + 2Al = Al 2 O 3 (s) + 3C

First, the SiO ₂ (s) contained in the refractory
And C (s), a reaction represented by the above formula (1) occurs,
O (g) and CO (g) are produced. Next, between Al in the molten steel and these SiO (g) and CO (g),
The reaction shown in (3) occurs, and Al ₂ O ₃ (s) is generated and adheres to the nozzle inner hole surface. It is considered that starting from the alumina thus generated, the alumina in the molten steel adheres and deposits on the alumina, and the nozzle blockage proceeds.

[0007] As means for preventing such nozzle blockage, various methods have been conventionally studied and proposed. For example, as an effective method for preventing nozzle blockage, gas blowing is generally performed. This gas blowing method is a method in which an inner hole of an immersion nozzle or the like is made porous, and Ar gas or the like is caused to flow through the pores, and is a method of preventing the adhesion of alumina by the flow of the gas. This method is effective in preventing nozzle blockage, and many steelworks employ this method.

However, if the gas is flowed to such an extent that nozzle clogging can be prevented, there is a disadvantage that fine gas bubbles enter the mold and are taken into the slab to generate defects. In addition, the fluctuation of the molten metal level in the mold becomes large, and inclusions are easily entangled, so that there is also a disadvantage that defects are easily generated in the slab.

As a method other than the gas blowing method, there is known a "measure for preventing clogging by using a CaO-containing zirconia clinker" as disclosed in Japanese Patent Publication No. 2-23494. This is because CaO contained in the zirconia clinker reacts with Al ₂ O ₃ particles precipitated in the molten steel to generate a CaO-Al ₂ O ₃ -based low melting point compound, and the low melting point compound is formed by the flow of the molten steel. Remove
The purpose is to prevent the adhesion of alumina.

This method is considered to be effective in preventing alumina from adhering. And the immersion nozzle which arrange | positioned such a material using the zirconia clinker containing CaO in the inner pipe part is actually used in many continuous casting machines. However, the zirconia clinker containing CaO has a large coefficient of thermal expansion, and since a material using this zirconia clinker is disposed on the inner hole side of the nozzle, a large thermal stress occurs outside the nozzle in the early stage of casting. However, there is a disadvantage that the spalling resistance is poor.

On the other hand, JP-A-3-243258, JP-A-5-243258
154628, JP-A-8-57601 and JP-A-8-576
No. 13 describes that "the oxide material containing no carbon or containing less than 1% by weight of carbon is used in the inner hole portion of the nozzle and the contact portion with the molten steel," It is disclosed that this prevents nozzle blockage. That is, these publications disclose that oxides such as alumina and magnesia are arranged in the inner hole of the immersion nozzle and in the contact portion with the molten steel, and have an effect of preventing adhesion of alumina and prevention of carbon pickup. Is described.

However, in the inventions described in these publications,
Each of these materials is almost free of a carbon source, and therefore has a drawback that its coefficient of thermal expansion is inevitably increased and its spalling resistance is poor.

As means for solving the above-mentioned "defect of poor spalling resistance", JP-A-8-57601 and JP-A-3-243258 cited above disclose an inner hole of a nozzle and molten steel. Contact area of the nozzle is "formed separately from the nozzle body"
It describes that after the nozzle body is completed, a method of pouring or press-fitting an oxide-based material or inserting a sleeve is described. However, this method has the drawback that the manufacturing process of the continuous casting nozzle becomes very complicated, the number of processes is increased, and the manufacturing cost becomes very high.

Japanese Patent Application Laid-Open No. 51-54836 also discloses an immersion nozzle in which a material containing no carbon is applied to the inner hole portion, which contains 90% or more of SiO ₂ . However, there is a disadvantage that the melting loss during casting is large. Further, JP-A-63-203258 discloses carbon
(C) Although a material having an amount of 20% by weight or less is disclosed, this method does not consider the particle size composition of the raw material to be used and the arrangement thickness of the inner hole, etc. Not satisfactory in point. (Note that application of materials other than oxides to nozzles is described in JP-A-56-139260.
No. 5 to 8 as boron nitride.
An invention containing 0% is disclosed. )

[0015]

In the prior arts which have been adopted and proposed as "measures for preventing nozzle blockage", all of the above-mentioned problems and disadvantages are inherent.

The present invention has been made in view of the above-mentioned problems and drawbacks of the prior art.
A method for preventing nozzle clogging, which has been conventionally adopted as described above.A method for preventing by gas blowing, or a reaction between alumina in molten steel and a component (CaO component) in a refractory to generate a low melting point compound. To solve the above-mentioned problems and drawbacks in the method of forming a refractory material that does not contain a carbon source into the inner hole of the nozzle by pouring or press-fitting. An object of the present invention is to provide a continuous casting nozzle which is effective and can be integrally formed at the time of molding.

[0017]

SUMMARY OF THE INVENTION The present invention relates to a continuous casting nozzle capable of preventing nozzle blockage due to adhesion of alumina during continuous casting of steel. The inner hole portion is a continuous casting nozzle composed of 1 to 10% by weight of a carbon-containing refractory material, and the refractory material other than carbon has a particle size of 420 μm or less, and the refractory material forming the inner hole portion is continuous. The casting nozzle has an integrated structure formed at the same time when the casting nozzle is formed, and the thickness of the portion is in a range of 2 to 12 mm (claim 1).

Further, the continuous casting nozzle according to the present invention comprises:
(2) In the above (1), the refractory material forming the inner hole portion is composed of carbon and oxide (claim 2), and in this case, cordierite is contained in the oxide in an amount of 5 to 70%.
(3) In the above (1), the refractory material forming the inner hole portion comprises carbon, an oxide and a Ca-containing compound, and the content of the Ca-containing compound is CaO. The refractory material is contained in an amount of 1 to 10% by weight in terms of conversion (Claim 4), (4) In the above (1), the refractory material forming the inner hole portion is (A) carbon and nitride,
(B) carbon, nitride and oxynitride, (C) carbon, nitride, oxynitride and oxide (claim 5), (5) above (1) ~ (4)
A slit structure is provided outside the refractory material forming the inner hole portion (claim 6).

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail including embodiments of the present invention. The present inventors have used a continuous casting nozzle in which the inner hole portion of the nozzle is composed of 1 to 10% by weight of a carbon-containing refractory material and the refractory material other than carbon has a particle size of 420 μm or less for continuous casting of steel. In this case, it was found that the amount of alumina attached to the inner hole of the nozzle was small, and that erosion by molten steel was suppressed. The present invention is characterized in that such an inner hole portion is integrally formed at the time of forming a continuous casting nozzle.

As the material used for such an inner hole portion, a refractory material having a carbon content of 1% by weight or more and 10% by weight or less is suitable. As can be seen from the above formula (1), when the amount of C in the refractory decreases, the formation of SiO (g) and CO (g) caused by the reaction of formula (1) is suppressed, and therefore,
The generation of ₂ O ₃ is also suppressed [Equation (2), Equation
(See (3)). From this point of view, it is better not to include carbon in the material of the inner hole portion, but in the present invention, the range of the amount of carbon is limited from the following viewpoints.

That is, in the continuous casting nozzle according to the present invention, the carbon content is 1 to 10% by weight (more preferably 1 to 8% by weight).
% By weight) is preferred. The reason is that if the amount of carbon exceeds 10% by weight, the effect of preventing adhesion of alumina is significantly reduced. Conversely, if the amount is less than 1% by weight, the heat-resistant spall resistance of the nozzle is significantly reduced, and cracks during casting are reduced. This is because the danger of escalation increases.

In general, the smaller the amount of carbon, the lower the tendency of the adherence of alumina to "the degree of adhesion of alumina". However, the lower the amount of carbon, the lower the heat-resistant spalling property. Considering the use conditions such as the casting condition of the nozzle and the preheating condition of the nozzle,
Adjust the carbon amount appropriately within the range of "1-10% by weight",
It is necessary to control the spall resistance.

As the carbon source, graphite, artificial graphite, carbon black, pitch and the like can be suitably used. These carbon sources can be used alone or in combination. A component used as a binder at the time of kneading the raw materials, for example, carbon generated by carbonizing a phenol resin or the like is also suitable as a carbon source. The carbon particle size is preferably 600 μm or less. The reason for this is that, when the particle size exceeds 600 μm, the structural change when decarburization occurs due to oxidation becomes significantly large.

In addition to carbon, examples of the material used for the inner tube portion include oxides, Ca-containing compounds, nitrides, and oxynitride refractory materials. In the present invention, it has been clarified that the use of these materials as a refractory material for forming an inner hole suppresses alumina adhesion.

As the oxide, alumina, mullite, magnesia, spinel, zirconia, cordierite and the like can be used, but it is not particularly limited to these oxides. In the present invention, as the oxide, a compound having a melting point higher than the temperature of the molten steel is desirable. However, a compound having a melting point lower than the temperature of the molten steel, for example, cordierite, eucryptite, sponge yumen, etc. is also combined with the high melting point oxide. It can be used by

Further, in the present invention, it has been found that when cordierite is used as the oxide, the effect of preventing alumina adhesion is high. Cordierite 2M
It is a compound represented by the composition of gO · 2Al ₂ O ₃ · 5SiO ₂ , and its melting point is about 1460 ° C., which is about 100 ° C. lower than the temperature of molten steel.

The process of forming alumina is as described above.
Formulas (1) to (3) are shown, but the cordierite melts to form a liquid phase on the surface or inside of the inner hole member material, and SiO (g) or CO (g) from the nozzle body portion It is considered that the diffusion of Al ₂ O ₃ is suppressed and the generation of Al ₂ O ₃ is suppressed. Since cordierite decomposes into mullite and a liquid phase after melting, the amount of the generated liquid phase does not become excessive, and therefore, there is no danger that the entire inner hole is washed away by the molten steel flow. Furthermore, cordierite has a coefficient of thermal expansion as low as about one-fourth that of alumina, and the addition thereof can improve the thermal shock resistance of the inner hole.

The amount of cordierite to be added is 5 to 7
A range of 0% by weight is preferred. If it is less than 5% by weight, the effect of preventing alumina adhesion is small, while if it exceeds 70% by weight, the amount of liquid phase generated is excessive, the strength of the inner hole is reduced, and there is a risk of being washed away by the molten steel flow. Not preferred. Cordierite has a theoretical composition of "2MgO.2Al
_{Although represented by 2} O ₃ .5SiO ₂ ″, cordierite that can be used in the present invention can be used even if it is accompanied by a small amount of other minerals in addition to the mineral shown by this theoretical composition.

In the present invention, it has been found that when a Ca-containing compound is used together with carbon and oxide as the material used for the inner hole portion, the effect of preventing alumina from adhering is enhanced. This is because the Ca-containing compound reacts with the alumina in the molten steel to form a CaO-Al ₂ O ₃ based low-melting compound of presumably because be washed away by the flow of molten steel.

The Ca-containing compounds include CaF ₂ , Ca
CO ₃ , CaCO ₃ · MgCO ₃ , CaO · SiO ₂ , 2C
_{aO · SiO 2, 3CaO · SiO} 2, Ca 2 B 6 O 11 · 5
Although H ₂ O or the like can be suitably used, in the present invention,
It is not limited to these CaO-containing compounds. Ca
The content of the O-containing compound is preferably in the range of 1 to 10% by weight in terms of CaO in the refractory material forming the inner hole. Less than 1% by weight has little effect of preventing adhesion, 10% by weight
Above, the amount of liquid phase generated in the inner hole material becomes excessive,
This is not preferable because the strength of the inner hole is greatly reduced.

Examples of the nitride include silicon nitride and boron nitride, and examples of the oxynitride include sialon and silicon oxynitride. In the present invention, even when a nitride or an oxynitride is used, the adhesion of alumina is suppressed, but in this regard, SiO ₂ is hardly contained in these compounds, and therefore, the above-mentioned formula ( It is considered that the reaction represented by the formula (1) is suppressed. Also, the coefficient of thermal expansion of nitride is generally low, for example, the coefficient of thermal expansion of silicon nitride is about 3 × 10 ^-6 (average of 25 to 1000 ° C.). It is relatively close to that of ₂ O ₃ -carbon material, and is advantageous in terms of thermal shock resistance.

The oxynitride can be added at the kneading stage of the raw materials, but can also be formed by reacting during firing. For example, when silicon nitride and Al ₂ O ₃ are used, β-sialon is generated by a reaction at the time of firing. On the other hand, when oxides of rare earth elements such as silicon nitride, aluminum nitride and yttria are used, α-sialon is used. Will be generated. Of course, even during steel casting, these reactions proceed.

The above-mentioned nitride can be used in combination with an oxide. In this case, the following ranges are preferable. · Oxide (Al ₂ O ₃ and one or more kinds selected from oxides of rare earth elements) 0 to 50 wt%, of silicon nitride: 50-90% aluminum nitride: 0-20% by weight and nitriding Boron: 0 to 40% by weight-Graphite: 1 to 10% by weight

By firing the material of the inner hole member containing the raw material of the above combination or by heating at the time of casting the steel,
An inner hole member including an oxide, a Ca-containing compound, a nitride, and an oxynitride can be obtained. When nitride is used, there is a problem of nitrogen pickup. However, the erosion of the nozzle for continuous casting according to the present invention is slight, and the pickup of nitrogen can be minimized.

The oxides, nitrides, and Ca-containing compounds used in the present invention preferably have a particle size range of 420 μm or less. In this case, the following particle size range is more preferable. 1 μm or less: 20% by weight or less [more preferably 15% by weight or less] 1 to 44 μm: 10 to 85% by weight [more preferably 20 to 75%]
% By weight] 44-420 μm: 15-90% by weight [more preferably 20-80%
weight%]

In the present invention, when the particle size of the refractory material used is larger than 420 μm, the ratio of the maximum particle size to the wall thickness of the inner hole becomes too high, and the mechanical strength is reduced.
It is not preferable because coarse particles may fall off during casting. On the other hand, when the fine powder of 1 μm or less exceeds 20% by weight, the sinterability increases, and the sintering progresses due to the sintering step in the production of the product and the heating by the molten steel in the casting, causing shrinkage.
The inner hole portion comes off from the main body. Also, 1-4
For 4 μm particle size, less than 10% by weight or 85%
When the content is more than 10% by weight, the size gap between the raw material particles becomes too large, and there is a problem in thermal shock resistance.
If the particle size is less than 15% by weight or more than 90% by weight, the same problem as described above occurs, and neither is preferable.

In the continuous casting nozzle according to the present invention,
The thickness of the inner hole is preferably in the range of 2 to 12 mm. If it is less than 2 mm, erosion occurs during casting and the material of the nozzle body may be exposed, and if it exceeds 12 mm, the thermal expansion of the inner hole becomes large and the risk of cracking increases, which is not preferable. . In the present invention, there is no particular limitation on the thickness of the refractory material provided around the discharge hole other than the inner hole of the continuous casting nozzle or at the bottom thereof.

When a low carbon material is used in the inner hole of the continuous casting nozzle, the coefficient of thermal expansion of such a material is inevitably increased, resulting in poor heat spalling. Therefore, especially in the early stage of casting, it is considered that a large thermal stress is generated outside the nozzle due to thermal expansion accompanying a rapid temperature rise when the molten steel passes, and the refractory may be destroyed. To prevent this, for example, the above-mentioned JP-A-8-57601
In the invention described in the above publication, the inner hole and the portion in contact with the molten steel are not formed simultaneously with the nozzle main body, but are formed by pouring or press-fitting later, and at that time, as an expansion absorption allowance with the main body material. Joints are provided.

In the present invention, as a means for alleviating the thermal stress in the early stage of casting, formation of a slit structure (gap) between the inner hole and the nozzle body by simultaneous molding with the nozzle body and the inner tube material. Found to be effective. If the material of the inner hole is in direct contact with the material on the outside, the influence of the expansion on the inside is inevitable.However, by providing a slit structure between them, it acts as an expansion absorption allowance and reduces thermal stress. It is effective for

As an effect of the slit structure, an effect of heat insulation can be further considered. As one of the factors of the alumina adhesion, “promotion of adhesion due to a decrease in the temperature of the nozzle inner hole” can be considered. However, the heat insulation layer formed by the slit structure suppresses the diffusion of heat to the outside of the nozzle, It is estimated that alumina attachment is suppressed.

These slit structures need to be formed at the same time when the nozzle body is formed, and can be formed using, for example, a material which disappears by heating, such as paraffin paper. In the present invention, the thickness of the slit is
0.3 to 2.0 mm is preferred. If it is less than 0.3 mm, the effect of absorbing thermal expansion is small, and if it is more than 2.0 mm, the bonding force with the nozzle main body is weakened, and molten steel easily penetrates into the inner hole portion.

The length of the slit structure is preferably not less than 1/4 and not more than 9/10 of the total length of the inner hole.
If the slit length is less than one-fourth of the total length of the inner hole, the effect of preventing cracking is small. On the other hand, if the slit length is more than 9/10, the force holding the inner hole is weakened, and the inner hole is missing. It is not preferable because it easily leads to the like.

Further, in the present invention, as the slit structure portion, a bridge structure in which the nozzle main body portion and the inner hole portion are partially in contact with each other may be employed. This is because if the length of the slit is increased, the force for holding the inner hole is weakened, and the force of the molten steel flow pushes the inner hole to the outside, causing a risk of breaking. In such a bridge structure, the area of the contact is one third of the total area of the slit.
The following is preferred. If it exceeds one-third, the effect of the slit as the expansion absorption margin decreases, and the thermal shock resistance decreases. In the present invention, the shape of the bridge is not particularly limited.

In the continuous casting nozzle according to the present invention, the effect of preventing nozzle blockage due to alumina adhesion is extremely high.
On the other hand, the carbon content is "1 to 10% by weight", which is lower than that of a normal nozzle, so that the effect of suppressing carbon pickup due to erosion also occurs. Therefore, in casting of ultra-low carbon steel or the like in which carbon pickup becomes a problem, the material used in the present invention (1 to 10% by weight of a carbon-containing refractory material) is applied to the inner hole portion of a long nozzle or an immersion nozzle. It is effective to do.

As a method for producing the integrated refractory for continuous casting of the present invention, the following method can be mentioned.
First, a binder is added to a compound such as carbon, an oxide, a Ca-containing compound, or a nitride and kneaded using a mixer such as a wet pan to obtain a kneaded material for forming an inner hole.
Kneading is also performed on the nozzle body in the same manner to obtain a kneaded material for molding.

Next, these kneaded materials are filled into a molding frame, which is carried out by using a molding jig in order to adjust the arrangement thickness. Then, the jig is removed after filling, and then CI
Forming is performed by P forming, mechanical pressing or the like. (If a slit structure is to be formed, paraffin paper or the like is set around the jig.) The obtained molded body is dried and subsequently fired in a non-oxidizing atmosphere. After firing, if necessary, processing is performed to obtain the final shape.

[0047]

Next, examples of the present invention will be described together with comparative examples.
The present invention will be described in more detail, but the present invention is not limited by the following examples.

(Examples 1 to 9, Comparative Examples 1 to 4) Graphite, alumina, mullite, magnesia, cordierite, silicon nitride, BN (boron nitride), CaF,
Kneading was performed using CaO.SiO ₂ , a phenol resin and molasses as binders, and using a wet pan in a mixing ratio shown in Table 1 to obtain a kneaded soil for molding. The obtained kneaded material was subjected to CIP molding at a pressure of 1.0 t / cm ² , and then the molded body was fired at 1000 ° C. for 3 hours in a non-oxidizing atmosphere. A sample of 25 × 25 × 250 (mm) was prepared from the obtained fired body and used as a test piece for evaluation. The properties (apparent porosity, bulk specific gravity, bending strength) of these samples are also shown in Table 1.

The test piece prepared as described above was immersed in molten steel, and an alumina adhesion test was performed. In the adhesion test, “Al
% Al-killed steel "was melted using a high-frequency induction furnace, and 1% by weight of aluminum was further charged. The test piece was immersed in the bottom 12 cm from the lower end, and rotated at a speed of 10 revolutions per minute. After the test, the sample was cut in half in the longitudinal direction, and the thickness of the adhered alumina on both sides at a position 5 cm from the lower end was measured and averaged. Also described.

[0050]

[Table 1]

As a result of the alumina adhesion test shown in Table 1, in Examples 1 to 9 (graphite content: 1 to 8% by weight) of the present invention, Comparative Example 1
Compared with a product containing 15% of graphite, it was confirmed that the adhesion prevention effect was large. Comparative Example 2
Although the thickness of the sample was the same as that of Examples 1 to 9, after the test, cracks were considered to have occurred due to thermal spalling inside the sample, indicating that there was a problem in spalling resistance.

In Comparative Example 3, the strength was low due to the coarse-grained composition (see “Granularity” in Table 1).
(At the time of immersion in molten steel), particles were falling off. Furthermore, in Comparative Example 4, because of the fine powder composition (see the “granularity” section in Table 1),
Since the sintering occurred during the immersion of the molten steel, cracks occurred and the sample dropped off, so that the thickness of the adhered alumina could not be measured.

(Examples 10 to 13 and Comparative Examples 5 to 8) An actual machine in which the composition of Examples 1, 2, 3, and 6 and Comparative Example 1 (see Table 1) was applied to the inner hole portion. An immersion nozzle having a shape was manufactured. FIG. 1 shows an arrangement position in the inner hole of the immersion nozzle. In FIG. 1, reference numeral 10 denotes a nozzle body, 11 denotes a nozzle inner hole, 12 denotes a powder line material, and 13 denotes a discharge hole of molten steel.

In Examples 10 to 13 (Comparative Examples 5 to 8),
The nozzle inner hole 11 and other parts were simultaneously molded to form an integrated structure, and the thickness of the nozzle inner hole 11 was about 5 mm. As a molding means, a CIP molding method is adopted, and 1.0 t / cm ²
At a pressure of This molded body is placed in a non-oxidizing atmosphere
It was fired at 00 ° C. for 3 hours, and the obtained fired body was processed into a final shape to produce the immersion nozzle for a real furnace test shown in FIG.

A "casting test in an actual furnace" was performed using each of the manufactured immersion nozzles. In this casting test, a 2-strand mold was used as a continuous casting machine, and the product of this example was attached to the No. 1 strand (1st) and the comparative example was attached to the No. 2 strand (2st). This was performed four times in total. After the test, the immersion nozzle was collected afterward, and the adhesion state of alumina was investigated. The thickness of the adhered alumina was measured at three places of the pipe straight inside the immersion nozzle after cutting the used immersion nozzle in half in the longitudinal direction, and the average thickness was obtained. Table 2 shows the casting conditions and the measurement results of the adhesion thickness. [The cast steel type is the same in each test, and its components are on average about C: 0.01, Mn: 0.30, Al: 0.03, N: 0.004
(% By weight). ]

[0056]

[Table 2]

From Table 2 (casting test results in an actual furnace), it was confirmed that in Examples 10 to 13, even after 5 ch casting, adhesion of alumina was slight. On the other hand, in Comparative Examples 5 to 8, it was recognized that the adhesion of alumina was extremely large. In Comparative Example 6 in Test 2, the blockage became large in 4 ch, and the casting was stopped halfway.

(Examples 14 to 19, Comparative Examples 9 to 10) The kneaded products of the composition of Examples 3, 4, 5 and Comparative Example 1 (see "Table 1" above) were applied to the inner hole. An immersion nozzle having an actual machine shape was manufactured. At this time, a slit 24 was provided around the inner hole of the immersion nozzle at the position shown in FIG. (Note that in FIG. 2, reference numeral 20 denotes a nozzle main body, 21 denotes a nozzle inner hole, 22 denotes a powder line material, and 23 denotes a molten steel discharge hole.)

As shown in FIG. 2, the length "A" of the slit 24 was two-thirds "2/3 A" of the entire length of the nozzle inner hole 21. The thickness of the nozzle inner hole 21 was set to about 7 mm, and the thickness of the space of the slit 24 was set to 0.8 mm. As for Examples 14, 16, 18 and Comparative Example 9 (immersion nozzles having a slit structure), those having a structure without a slit structure were also manufactured and used for comparison (Examples 15, 17, 19, 19).
Comparative example 10).

A "casting test in an actual furnace" was performed using each of the manufactured immersion nozzles. The continuous casting machine used in this casting test was a one-strand type, and each test performed casting up to 4 ch. The immersion nozzle after the test was collected, and the state of adhesion of alumina was observed. The adhesion thickness of alumina is
After the used immersion nozzle was cut in half in the longitudinal direction, it was measured at three places on the straight body of the tube inside the immersion nozzle, and the average was determined.
Table 3 shows the casting conditions and the measurement results of the adhesion thickness. [The cast steel type is the same in each test, and the components are, on average, about C: 0.02, Mn: 0.20, Al: 0.04, N: 0.00.
4 (% by weight). ]

[0061]

[Table 3]

From Table 3 (the results of the casting test in the actual furnace), it was confirmed that in Examples 14 to 19, the adhesion of alumina was reduced. Then, even if the inner hole portion has the same composition, the immersion nozzles having the slit structure (Examples 14, 16, and 18) have a higher efficiency than the immersion nozzles without the slit structure (Examples 15, 17, and 19). However, a slight tendency was observed for the adhesion of alumina. In addition, in the blends of Examples 16 and 17, the amount of carbon was as small as 1% by weight and spalling was concerned. However, Example 16 having the slit structure was used without any cracks. On the other hand, those having a structure without a slit (Example 17)
A vertical crack occurred at the beginning of the second channel, and the casting was stopped. In Comparative Examples 9 and 10, cracking did not occur, but the alumina adhesion thickness was large (large clogging).

[0063]

As described in detail above, the continuous casting nozzle according to the present invention has an inner hole portion in contact with molten steel of 1 to 10% by weight.
A continuous casting nozzle composed of a carbon-containing refractory material of the present invention, and wherein the refractory material other than carbon has a particle size of 420 μm or less, wherein the refractory material forming the inner hole portion is formed at the time of molding the continuous casting nozzle. Having a one-piece structure molded at the same time, the thickness of the portion is in the range of 2 to 12 mm, whereby nozzle clogging does not occur,
In addition, it is possible to provide a continuous casting nozzle that can be integrally formed at the time of molding.

[Brief description of the drawings]

FIG. 1 is a view showing an arrangement position in an inner hole portion of an immersion nozzle.

FIG. 2 is a diagram in which a slit structure is provided around an inner hole of an immersion nozzle.

[Explanation of symbols]

 10,20 Nozzle body 11,21 Nozzle inner hole 12,22 Powder line material 13,23 Discharge hole of molten steel-, 24 Slit

Claims (6)

[Claims] 1. A continuous casting nozzle in which an inner hole portion in contact with molten steel is composed of 1 to 10% by weight of a carbon-containing refractory material, and a refractory material other than carbon has a particle size of 420 μm or less. Wherein the refractory material forming the above has an integrated structure formed simultaneously with the formation of the continuous casting nozzle, and the thickness of the portion is in the range of 2 to 12 mm. 2. The continuous casting nozzle according to claim 1, wherein the refractory material forming the inner hole portion is made of carbon and oxide. 3. The method according to claim 1, wherein cordierite is added to the oxide in an amount of 5 to 7%.
3. The nozzle for continuous casting according to claim 2, wherein said nozzle contains 0% by weight. 4. The refractory material forming an inner hole portion comprises carbon, an oxide and a Ca-containing compound.
The continuous casting nozzle according to claim 1, wherein the content of the compound is 1 to 10% by weight in the refractory material in terms of CaO. 5. The refractory material forming an inner hole portion,
(A) carbon and nitride, (B) carbon, nitride and oxynitride, (C) carbon, nitride, oxynitride and oxide The nozzle for continuous casting according to claim 1. 6. The continuity according to claim 1, wherein said inner hole portion is provided with a space by a slit structure outside said refractory material forming said inner hole portion. Nozzle for casting.