JPH1110321A - Nozzle for casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a casting nozzle (material of a nozzle main body) which does not break and does not generate cracks due to thermal stress and mechanical stress without reducing the corrosion resistance of the casting nozzle. To do. SOLUTION: (1) a fused alumina raw material having a specific composition, (2) a fused mullite-zirconia raw material also having a specific composition, and
(3) a casting nozzle combining graphite raw material,
(1) Fused alumina raw material having Al ₂ O ₃ of 94% by weight or more, Fe ₂ O ₃ of 0.4% by weight or less, and Na ₂ O of 0.4% by weight or less: 50 to 87
(2) Al ₂ O ₃ is 40 to 53% by weight and SiO ₂ is 13 to ₂ % by weight.
0 wt%, ZrO ₂ is 32 to 44 wt% of fused mullite - zirconia material: 3 to 25 weight percent, (3) graphite material: the raw material blend consisting of 10 to 35 wt%, kneaded together with a binder A casting nozzle made by molding, firing and firing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nozzle for casting molten metal, and more particularly, to a nozzle for casting which does not cause deterioration due to thermal stress and mechanical stress without reducing corrosion resistance.

[0002]

2. Description of the Related Art The inside surface of a casting nozzle has little reaction with molten metal, resists wear and damage caused by the flow of molten metal, and suffers from "nozzle clogging" due to adhesion and deposition of alumina clusters and the like precipitated from molten steel. Refractory materials that are unlikely to occur are required. Also, the outer surface of the casting nozzle must withstand erosion by slag and casting powder.

[0003] The casting nozzle is preheated immediately before casting. However, at the start of casting, the nozzle is in direct contact with a high-temperature molten metal and is therefore exposed to a sudden thermal shock. At the same time, it receives a mechanical force such as vibration caused by the passage of the molten metal through the nozzle. Therefore,
The casting nozzle is subjected to very large thermal stress and mechanical stress at the same time, especially in the early stage of casting, and often causes "nozzle cracking" and breaks of the nozzle.

By the way, recent casting nozzles include:
In general, different materials are generally used for the main body and the powder line part which is a part of the outer surface. For example, an alumina-carbonaceous material is used for the main body portion, and a zirconia-carbonaceous material having high corrosion resistance to slag and casting powder is used for the powder line portion. Further, on the inner surface of the casting nozzle, recently, for the purpose of preventing clogging due to alumina in particular precipitated from the molten steel, a combination of a different CaO · ZrO ₂ material and carbon as the main body portion CZ-
C-type or alumina-type may be applied, and there are many examples in which effects are obtained.

Further, in order to prevent the above-mentioned "nozzle cracking", a method of adding and using fused silica to alumina-carbon material is known and widely used. This is an improvement in spalling resistance to thermal shock by utilizing the fact that the coefficient of thermal expansion of fused silica is very low.

[0006] In addition, Japanese Patent Publication No. 59-19067 discloses a casting nozzle excellent in corrosion resistance of a powder line portion, abrasion resistance of a working surface, and prevention of hole clogging. The main mineral phase is mullite, butterite, Consisting of corundum and chemical composition of Al ₂ O ₃ , ZrO ₂ , SiO ₂ within a certain range
A nozzle using a refractory raw material clinker (hereinafter abbreviated as “ZRM”) described in (Note) is disclosed. (Note): Al ₂ O ₃ → 25 to 85% by weight, ZrO ₂ → 10 to 70% by weight, SiO
₂ → 5 to 25% by weight

[0007] Japanese Patent Publication No. 61-2619 relates to an "alumina-carbon sliding plate" using zirconia mullite clinker having a low expansion property to reduce the progress of fatigue due to repeated thermal shock at high temperatures. Techniques are disclosed. Similarly, Japanese Unexamined Patent Publication No. 63-117950 discloses a method for producing a slide gate plate brick utilizing the low expansion property of zirconia mullite clinker.
Is disclosed.

[0008] Japanese Patent Publication No. 7-74091 discloses a "sporing-resistant porous plug refractory for gas injection" using zirconia mullite. Further, Japanese Patent Application Laid-Open No. 9-25157 discloses a "refractory for casting having excellent thermal shock resistance and corrosion resistance" using alumina-zirconia-silica clinker having a high SiO ₂ content.

[0009]

As described above, the inner surface of the casting nozzle requires a refractory material that is resistant to corrosion, abrasion, and nozzle blockage against molten metal, and the outer surface has slag and slag. Corrosion resistance to powder is required.
Further, it must have resistance to cracking against large thermal stress and mechanical stress during casting.

[0010] In order to meet the above demand, a technique for adjusting damage by providing a nozzle clogging prevention layer on the inner surface of a casting nozzle is being established. However,
The nozzle blockage prevention layer on the inner surface does not necessarily have high corrosion resistance and abrasion resistance, and therefore, the material of the main body needs to have a conventional level of corrosion resistance. On the other hand, damage to the outer surface of the nozzle has led to a situation where corrosion resistance of practically no problem is obtained by providing a powder line portion made of zirconia-carbonaceous material and the like. It may be about the same as that of the related art, and need not be further increased.

[0011] As described above, by applying the prior art of arranging a material suitable for each of the powder line portions of the nozzle inner surface layer and the nozzle outer surface layer as described above, the problem is almost eliminated. Can be eliminated.

[0012] However, a material having the above-mentioned "cracking resistance to large thermal stress and mechanical stress during casting" has not been known so far. In other words, there was no satisfactory material (material of the nozzle body) regarding “cracking resistance to thermal and mechanical stress” due to thermal shock and vibration at the start of casting.

For example, when fused silica is used, it has the effect of suppressing cracking against thermal shock, but has no effect on mechanical stress, and when the amount of fused silica used is increased, There is a disadvantage that the corrosion resistance is significantly reduced. Also, regarding the “nozzle using ZRM” disclosed in the above-mentioned Japanese Patent Publication No. 59-19067, no consideration is given to crack resistance, and the corrosion resistance is remarkable depending on the composition and blending ratio of ZRM. It has the disadvantage that it can be reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to reduce the corrosion resistance of conventional nozzles without deteriorating thermal and mechanical stresses. An object of the present invention is to provide a casting nozzle (material of the nozzle body) that does not break and does not break.

[0015]

Means for Solving the Problems The present inventors, while comparing with a conventional alumina-carbonaceous nozzle, have studied a fused alumina raw material having a composition range with good corrosion resistance and crack resistance. The fused mullite-zirconia raw material of a specific composition range is
The decrease in corrosion resistance is small, the coefficient of thermal expansion is small and stable, and it is found that it has hot deformability, and by combining the fused alumina raw material and the fused mullite-zirconia raw material, The present invention has been completed.

That is, the casting nozzle according to the present invention is made of “Al
₂ O ₃ is 94% by weight or more, Fe ₂ O ₃ is 0.4% by weight or less, Na ₂
Fused alumina raw material with O less than 0.4% by weight 50-87% by weight
When, in Al ₂ O ₃ is 40 to 53 wt%, and SiO ₂ is 13 to 20 wt%, fused mullite is ZrO ₂ is 32 to 44 wt% - zirconia material 3-25 wt%, graphite material 10 A casting nozzle obtained by kneading, shaping and firing a raw material mixture consisting of up to 35% by weight together with a binder. (Claim 1), and the raw material mixture is further mixed with a fused silica raw material in an amount of 3 to 15% by weight (Claim 3)
Is the gist.

Further, the casting nozzle according to the present invention is characterized in that the fused alumina raw material is a raw material containing 3.5% by weight or less of TiO ₂ (Claim 2).

[0018]

Embodiments of the present invention will be described below in detail.

(Fused Alumina Raw Material) The fused alumina raw material used in the present invention contains Al ₂ O ₃ of 94% by weight or more,
The composition must be such that Fe ₂ O ₃ is 0.4% by weight or less and Na ₂ O is 0.4% by weight or less.

As described above, the alumina raw material (fused alumina raw material) used in the present invention must have an Al ₂ O ₃ content of 94% by weight or more. If the Al ₂ O ₃ content is less than 94% by weight, the corrosion resistance of the electrofused mullite-zirconia raw material is not high as described later, and it is difficult to maintain the corrosion resistance. (A more preferable Al ₂ O ₃ content is 97% by weight or more.)

The content of Fe ₂ O ₃ in the alumina raw material (electrofused alumina raw material) used in the present invention is preferably 0.4% by weight or less. Exceeding this not only causes a decrease in corrosion resistance, but also causes a reduction atmosphere in the internal structure of the nozzle due to the effect of graphite used at the same time, and a reduction reaction of Fe ₂ O ₃ may occur.
This reduction reaction results in embrittlement of the structure of the nozzle, resulting in a reduction in strength, cracking, and breaking. (The content of Fe ₂ O ₃ is more preferably 0.2% by weight or less.)

Further, the content of Na ₂ O in the alumina raw material (electrofused alumina raw material) used in the present invention is preferably 0.4% by weight or less. Above this, not only is the corrosion resistance reduced, but also Na
The effect of the volatilization of ₂ O increases, leading to embrittlement of the nozzle structure. (The content of Na ₂ O is more preferably 0.3
% By weight or less. )

The alumina raw material used in the present invention must be fused alumina. In the case of a sintered alumina raw material, since corundum crystals are small and easily reacted, corrosion resistance is inferior and is not preferable. Therefore, in the present invention, it is preferable to use a raw material in which corundum crystals have greatly developed by electrofusion.

Further, as the fused alumina raw material used in the present invention, a raw material containing TiO ₂ in the range of 3.5% by weight or less may be used in order to improve the cracking property of the grains themselves.
The fused alumina containing a small amount of TiO ₂ is based on the fact that it has a property of not easily breaking due to mechanical stress. However, since the fused alumina raw material containing TiO ₂ has lower corrosion resistance than the high-purity alumina raw material, the TiO ₂ content preferably does not exceed 3.5% by weight.

(Electrofused mullite-zirconia raw material) The electrofused mullite-zirconia raw material used in the present invention is as follows.
In al ₂ O ₃ is 40 to 53 wt%, and SiO ₂ is 13 to 20 wt%, ZrO
₂ must have a composition within the range of 32 to 44% by weight.

The electrofused mullite-zirconia raw material used in the present invention has a crystal structure in which monoclinic zirconia precipitates in the course of cooling the electrofused liquid composition, and the surroundings are surrounded by mullite. Is preferred. Further, when alumina is added in a slightly excessive amount to form mullite, a material having a crystal structure in which corundum, which is a crystal of alumina, is slightly crystallized is also preferable.

With such a crystal structure, it is possible to obtain a feature that the coefficient of thermal expansion is low and stable, and that the material has hot deformability. Therefore, even if the overall composition is the same, clinker obtained by sintering cannot be used for the casting nozzle according to the present invention, because the method of crystallizing is different.

As can be seen from the phase equilibrium diagram of FIG. 3, the composition region for obtaining such a crystal structure has a corundum as a primary crystal when Al ₂ O ₃ is excessive or ZrO ₂ is too small. Or mullite is precipitated, so that mullite cannot be deposited around monoclinic zirconia. For this reason, as the electrofused mullite-zirconia raw material used in the present invention, Al ₂ O ₃ must be 53% by weight or less and ZrO ₂ must be 32% by weight or more. Especially
If ZrO ₂ is less than 32% by weight, hot deformability is poor, which is not preferable.

As will be described later, the lower limit of Al ₂ O ₃ is S
Nearly all of the iO ₂ must be sufficient and sufficient to produce mullite, requiring at least 40% by weight, while the upper limit for ZrO ₂ is 44% by weight. If the content of ZrO ₂ exceeds 44% by weight, abnormal expansion of monoclinic zirconia at a high temperature adversely affects the volume stability of the nozzle and undesirably lowers the corrosion resistance. In order to obtain hot deformability, a ZrO ₂ content of 44% by weight or less is sufficient.

On the other hand, when the SiO ₂ is too much, crystals are precipitated, such as zircon and cristobalite, since and corrosion resistance decreases, SiO ₂ is required to be 20 wt% or less. When the amount of SiO ₂ is too small, the amount of monoclinic zirconia or corundum crystals becomes too large, and the expansion coefficient becomes irregular and large. Therefore, 13% by weight or more of SiO ₂ is necessary. In addition, the lower limit of Al ₂ O ₃ must be sufficient and sufficient for almost all of SiO ₂ to generate mullite, and it is necessary to be 40% by weight or more.

The fusible mullite-zirconia raw material used in the present invention may be strictly defined as a straight line connecting ZrO ₂ and 3Al ₂ O ₃ .2SiO ₂ (Alchemade line) in FIG. ) in the region more than the SiO ₂ ", usually the monoclinic zirconia, mullite, besides the crystalline corundum, amorphous silica remains. Amorphous silica has a low coefficient of thermal expansion and has no problem in the casting nozzle according to the present invention.

However, ZrO ₂ · SiO ₂
Since There may be crystallized, it fused mullite used in the present invention - composition range of the zirconia material is a Al ₂ O ₃ is 40 to 53 wt%, and SiO ₂ is 13 to 20 wt%, ZrO ₂ is 32 ~ 44 a% by weight, yet, SiO ₂ is connecting the "ZrO ₂ and 3Al ₂ O ₃ · 2SiO ₂ in the 3-component phase equilibrium diagram of _{SiO 2 -Al 2 O 3 -ZrO 2} ( see FIG. 3) Arukemade It is more preferable to be in the vicinity of the line or in the "region less than the line of the Arkemade".

Further, if the amount of SiO ₂ is less than the “line connecting ZrO ₂ and the eutectic point of the three components” shown by the one-dot chain line in FIG. 3, corundum crystals may precipitate before mullite. The fused mullite-zirconia raw material used in the invention is
The composition range is as described above (Al ₂ O ₃ is 40 to 53% by weight, SiO ₂ is 13 to 20% by weight, ZrO ₂ is 32 to 44% by weight), and SiO ₂ -Al ₂ O ₃ including a region (line between the -ZrO ₂ ternary phase equilibrium diagram as "straight line connecting the eutectic point of ZrO ₂ and 3Al ₂ O ₃ · 2SiO ₂ and the Arukemade line and ZrO ₂ connecting the three components" It is more preferable that the amount of SiO _{2 is in} ()).

The impurity component in the electrofused mullite-zirconia raw material is preferably 2% by weight or less, more preferably 1% by weight or less. If the amount of the impurity component is large (exceeding 2% by weight), the original hot deformability cannot be obtained and the corrosion resistance is further reduced, which is not preferable.

As described above, unless the composition is strictly adjusted, the fused mullite-zirconia raw material used in the present invention can suppress cracks generated by thermal stress and mechanical stress without deteriorating corrosion resistance. It is difficult. Therefore,
It is preferable that the mullite surround the monoclinic zirconia precipitated from the molten state, and if alumina is added in a slightly excessive amount to form mullite, corundum, which is an alumina crystal, is used. In order to obtain a slightly crystallized crystal structure, the above-mentioned ZrO ₂ , Al
It must be ₂ O ₃ and SiO ₂ content.

(Blending ratio of each raw material in the casting nozzle according to the present invention) In the casting nozzle according to the present invention, a graphite raw material is further added to the above-mentioned electrofused mullite-zirconia raw material as in the above-mentioned electrofused alumina raw material. It is made. The amount of each raw material is 50 to 87% by weight of the fused alumina raw material, 3 to 25% by weight of the fused mullite-zirconia raw material, and 10 to 35% by weight of the graphite raw material.

In order to ensure the corrosion resistance of the casting nozzle, it is necessary to use the fused alumina raw material having high corrosion resistance in an amount of 50% by weight or more. Particularly considering the fact that a metal having a high erodibility is cast, the use of 61% by weight or more is more preferable. The maximum usage (upper limit) of this fused alumina raw material is
87% by weight of the minimum remaining amount of other essential ingredients
It is.

The electrofused mullite-zirconia raw material exhibits stable low expansion properties and hot deformability, which are its characteristics.
In order to ensure sufficient crack resistance of the nozzle against thermal and mechanical stress applied by thermal shock and vibration at the start of casting,
It is necessary to use at least 3% by weight or more, more preferably 5% by weight or more. On the other hand, the electrofused mullite-zirconia raw material has a lower melting point than alumina or mullite raw material and does not have high corrosion resistance, and therefore, when used in excess, may cause reaction erosion, and therefore the upper limit is 25% by weight.
It is. More preferably, the content is controlled to 18% by weight or less.

As described above, the casting nozzle according to the present invention is obtained by blending an electrofused alumina raw material and an electrofused mullite-zirconia raw material with a graphite raw material. %. This graphite raw material is also used in conventional nozzles, and is for improving thermal conductivity and improving spalling property against thermal shock. For this purpose, 10% by weight or more of the graphite raw material is required. On the other hand, graphite is hardly wetted by slag and powder and does not easily react with it, but easily dissolves in, for example, molten steel. Therefore, if it is used in an excessively large amount, damage to the entire nozzle becomes large. Therefore, the upper limit is 35% by weight.

If a large amount of the electrofused mullite-zirconia raw material and the graphite raw material are used at the same time, the graphite raw material is quickly dissolved in the molten steel, while the electrofused mullite-zirconia raw material is not easily dissolved in the slag or the molten steel. When the electrofused mullite-zirconia raw material is used in an amount of 20% by weight or more, the graphite raw material is more preferably 25% by weight or less.

As described above, the casting nozzle according to the present invention, which is formed from the fused alumina raw material, the fused mullite-zirconia raw material, and the graphite raw material, has a high ability to withstand thermal shock and mechanical stress, and is most useful in actual use. Even at the beginning of casting under severe conditions, cracking and breakage hardly occur.

(Mixing of fused silica raw material) In the casting nozzle according to the present invention, the fused silica raw material, the fused mullite-zirconia raw material, and the graphite raw material are further mixed with a fused silica raw material within a range of 3 to 15% by weight. It can be used in addition.

Fused silica is a high-purity amorphous silica raw material that has been once melted and then cooled, and has a very low coefficient of thermal expansion, as is well known. Has the effect of improving. If the thermal stress generated by thermal shock is suppressed by the fused silica raw material,
Since the electro-fused mullite-zirconia raw material only needs to be responsible for the deformability to withstand mechanical stress, the effect of making the nozzle as a whole more difficult to break occurs.

In particular, in the case of a usage method in which the residual heat immediately before casting is not sufficient, the "stress due to thermal shock" at the start of casting is reduced.
Is characteristic of the present invention, and it is very effective to alleviate the mechanical stress due to vibration with the fused mullite-zirconia raw material. If the added amount of the fused silica raw material is less than 3% by weight, the effect of the addition is not remarkable, so 3% by weight or more is preferable. On the other hand, if it exceeds 15% by weight, the corrosion resistance of the nozzle is rapidly reduced, which is not preferable.

(Manufacture of the Nozzle for Casting According to the Present Invention) The nozzle for casting according to the present invention is manufactured by adding a binder to the compound of each raw material, kneading, molding and firing. (Note that
As the binder, conventionally used tars, pitches, resins such as phenolic resins, molasses, lignin, starch and the like can be used. That is, a binder is added to the mixture of the raw materials, and thereafter,
It is kneaded, molded, and fired at ordinary temperature or heated by a usual method. The firing temperature is usually around 900-1200 ° C,
In the firing atmosphere, the oxygen concentration and the like are adjusted as necessary.

Also in the casting nozzle according to the present invention, a refractory material of a different material can be used for the powder line portion and the inner surface layer of the nozzle as in the prior art, and this is also included in the present invention. is there. For example, the casting nozzle according to the present invention may be used as a nozzle body, and a portion in contact with slag or mold powder may be made of ZrO ₂ -C material with particular emphasis on corrosion resistance. In order to make use of the reactivity with alumina inclusions,
Material containing O · ZrO ₂ and CaO · TiO ₂ · ZrO _2, etc. Alternatively,
An oxide material containing no carbon can be used.

[0047]

Next, the present invention will be described in more detail with reference to Examples of a casting nozzle according to the present invention together with Comparative Examples, but the present invention is not limited to the following Examples.

(Examples 1 to 6, Comparative Examples 1 to 5) Example 1
As Comparative Examples 1 to 5, electrofused alumina raw materials and electrofused mullite-zirconia raw materials (A to F) having the chemical compositions and constituent minerals shown in Tables 1 and 2 were used.
Fused silica was used. Then, each formulation shown in Table 3 (formulation N
o. 1 to 11) were weighed to obtain starting materials. A phenolic resin was added to these starting materials in an amount of 12% by weight and kneaded to obtain a kneaded raw material for sample preparation. With respect to the raw materials used, the raw materials other than graphite were adjusted to have a maximum particle size of 0.59 mm, and the raw materials sieved with a standard sieve were used to adjust the composition to a continuous particle size.

[0049]

[Table 1]

[0050]

[Table 2]

[0051]

[Table 3]

The above kneading raw materials (formulation Nos. 1 to 11 shown in Table 3)
(A kneaded raw material obtained by adding a 12% by weight of a phenol resin to the starting raw material of Example 1) and kneading the resulting mixture at 1.0 t / cm ² by CIP molding. Next, each molded body was fired in a non-oxidizing atmosphere at 1200 ° C. for 3 hours to prepare a sample for corrosion resistance evaluation. The shape of the sample was a long column of 30 × 30 × 300 mm.

Each sample was subjected to a corrosion resistance evaluation test by immersion in molten steel, and the test results are shown in Table 4. The corrosion resistance evaluation test was as follows: C: 30 ppm, Si: 0.03%, Mn: 0.25%, P: 0.
007%, S: 0.015%, O: 500ppm
Each sample was immersed at a position 15 cm from the lower end while the temperature was kept at 00 ° C. The immersion time was 3 hours. And about the sample after a test, the thickness at the position of 7 cm from the lower end of the immersion part was measured at two places, and the erosion amount (mm) was obtained from the average value.
Further, the immersed portion was subjected to surface processing, a sample for strength measurement was prepared, the bending strength (MPa) was measured, and the porosity [apparent porosity (%)] was measured. In addition, also about the sample before a test, the bending strength (MPa) and the porosity [apparent porosity (%)] of each sample were measured.
It was shown to.

[0054]

[Table 4]

As is clear from Table 4, the samples of the present invention
(Examples 1 to 6) show that the amount of erosion is small.
Further, it can be understood that the material has a small decrease in bending strength and a small increase in porosity and can be used stably for a long time. On the other hand, in Comparative Examples 1 to 5, the amount of erosion is large, and the effect of the raw material composition is considered to be large. In addition, the decrease in strength and the increase in porosity of the sample after the test were particularly large in Comparative Examples 2, 4, and 5 in which a raw material having a large amount of impurities and a raw material having a large amount of SiO ₂ were used.

(Examples 7 to 12 and Comparative Examples 6 to 10) Each of the kneaded raw materials obtained by adding 12% by weight of a phenol resin to the starting materials of Formulation Nos. 1 to 11 shown in Table 3 and kneading the mixture was 1.0%. t
/ Cm ² , and baked at 1200 ° C. for 3 hours in a non-oxidizing atmosphere to produce a “spolling test nozzle 10” having the shape shown in FIG.

The spalling test was performed as follows. A nozzle kept at room temperature was immersed in hot metal at 1600 ° C. to a position 30 cm from the lower end, kept for 3 minutes, taken out, and quenched in water. In this test method, a tensile stress is generated at the outer periphery of the nozzle during rapid cooling in water, and the same conditions as the initial thermal stress conditions in an actual furnace can be obtained. Table 5 shows the results of the spalling test.

[0058]

[Table 5]

From Table 5, it can be seen that the nozzles of Examples 7 to 12
It became clear that no cracks were generated and the thermal shock resistance was excellent. On the other hand, among Comparative Examples 6 to 10, Comparative Examples 7, 8, and
Nozzle 10 did not crack and did not break, but nozzles of Comparative Examples 6 and 9 using formulation Nos. 7 and 10 generated many cracks during rapid cooling in water, The lower end of the nozzle fell off.

(Examples 13 to 18, Comparative Examples 11 to 16)
Kneading raw material obtained by adding 12% by weight of a phenolic resin to the starting materials of Formulation Nos. 1 to 6 (formulation of the present invention) and Formulations 8, 9, and 11 (comparative formulation) shown in Table 3 above In the same manner as in Examples 7 to 12, each kneaded raw material was subjected to CIP molding at 1.0 t / cm ² , and calcined at 1200 ° C. for 3 hours in a non-oxidizing atmosphere. An immersion nozzle 20 "for casting test in an actual furnace was manufactured. (Note that the comparative formulation No.
Items 7 and 10 were excluded because they were judged to be dangerous for use in actual furnaces based on the results of the spalling test. )

As shown in FIG. 2, this actual furnace test immersion nozzle is composed of a nozzle body A, a powder line portion B, and a fitting portion C. Examples 13 to 18 and Comparative Example 11 The kneading raw materials used in Nos. 1 to 16 were applied to the nozzle body portion A in FIG. 2, and the powder line portion material and the fitting portion material were arranged in the powder line portion B and the fitting portion C, respectively. This is a nozzle with a structure.

The continuous casting machine used for the actual furnace test was 2
Strand type, No. 1 strand Example 13
No. 2 to No. 18 (products of the present invention) were used as No. 2 strands.
6 (comparative product), and a total of six casting tests were performed. The average composition of the cast steel is C: 30 ppm, S
i: 0.02%, Mn: 0.30%, P: 0.01%, S: 0.02%,
O: 470 ppm, and casting of 3 ch (casting time about 150 minutes) was performed.

The used nozzle was recovered, the amount of erosion of the inner hole was measured, and the entire nozzle was observed. Table 6 shows the results. The amount of erosion in the inner hole was measured by cutting the nozzle in half in the longitudinal direction after use, and measuring the amount of erosion at one point P in FIG. 2 (the amount of erosion on one side).

[0064]

[Table 6]

As shown in Table 6, as a result of the casting test in the actual furnace, as shown in Table 6, the nozzles of Examples 13 to 18 had good erosion loss at the inner hole portion and no cracks occurred during casting. It became clear that it could be used. On the other hand, Comparative Examples 11 to 16
Nozzle has large erosion around the discharge hole together with the inner hole,
The result was inferior in corrosion resistance. Comparative Examples 12 and 1
As for Nos. 4 and 15, casting was stopped because a vertical crack which was considered to be due to thermal shock occurred during casting. It was also found that the heat resistance was unsuitable.

[0066]

As described in detail above, the present invention relates to a raw material blend obtained by blending a fused alumina raw material having a specific composition range, an electrofused mullite-zirconia raw material and a graphite raw material also having a specific composition range at a specific blending ratio. It is a casting nozzle made by adding and kneading a binder, molding and firing.
It is possible to provide a casting nozzle which does not break due to thermal stress and mechanical stress and does not break without reducing the corrosion resistance of the nozzle.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a “spalling test nozzle” manufactured in Examples 7 to 12 and Comparative Examples 6 to 10.

FIG. 2 is a longitudinal sectional view of an “immersion nozzle for actual furnace test” manufactured in Examples 13 to 18 and Comparative Examples 11 to 16.

FIG. 3 is a phase equilibrium diagram of Al ₂ O ₃ —SiO ₂ —ZrO ₂ .

[Explanation of symbols]

 10 Nozzle for spalling test 20 Immersion nozzle for actual furnace test

Claims (3)

[Claims] In 1. A Al ₂ O ₃ is 94 wt% or more and Fe ₂ O ₃ is 0.
50 to 87% by weight of fused alumina raw material having 4% by weight or less and 0.4% by weight or less of Na ₂ O, 40 to 53% by weight of Al ₂ O ₃ and SiO 2
₂ to 13 to 20% by weight, ZrO ₂ to 32 to 44% by weight, fused mullite-zirconia raw material 3 to 25% by weight, graphite raw material 10 to 35
Kneading the raw material mixture consisting of
A casting nozzle characterized by being formed and fired. 2. The casting nozzle according to claim 1, wherein the fused alumina raw material is a raw material containing 3.5% by weight or less of TiO ₂ . 3. The method according to claim 1, wherein the content of Al ₂ O ₃ is at least 94% by weight and the content of Fe ₂ O ₃ is not less than 0.4%.
50 to 87% by weight of fused alumina raw material having 4% by weight or less and 0.4% by weight or less of Na ₂ O, 40 to 53% by weight of Al ₂ O ₃ and SiO 2
₂ to 13 to 20% by weight, ZrO ₂ to 32 to 44% by weight, fused mullite-zirconia raw material 3 to 25% by weight; fused silica raw material
A casting nozzle obtained by kneading a raw material mixture consisting of 3 to 15% by weight and 10 to 35% by weight of a graphite raw material together with a binder, followed by molding and firing.