Title of the invention: Nozzle and structure of nozzle and stopper
Technical field
[0001]
　The present invention relates to a continuous casting nozzle (specifically, a dipping nozzle, a tundish nozzle, etc.) and a continuous nozzle that are fitted to a stopper that controls the flow rate when the molten steel is discharged from the tundish to a mold in the continuous casting of molten steel. Regarding the structure of casting nozzles and stoppers.
　In this specification, the "nozzle for continuous casting" is simply referred to as a "nozzle".
Background technology
[0002]
　In continuous casting of molten steel, inclusions such as alumina may adhere to the fitting region including the contact portion between the stopper and the nozzle, making it difficult to control the flow rate.
　As a measure to prevent inclusions from adhering to such a fitting region, for example, in Patent Document 1, porous refractories are provided on the upper and lower molten steel contact surfaces with the contact portion with the stopper as a boundary, and from each porous refractory. A stopper receiving nozzle at the bottom of the tundish that can independently blow out argon gas is disclosed.
　However, when argon gas is blown out from a porous refractory, the bubble diameter of the gas in the molten steel becomes too large, the flow rate becomes excessive and control becomes difficult, and the gas discharge area is large, so the amount of gas to be discharged is the discharge surface. This may cause problems such as non-uniformity and easy adhesion of inclusions to some parts.
[0003]
　There is a form in which argon gas is discharged from a discharge port other than such a porous refractory.
　For example, Patent Document 2 makes it possible to blow the inert gas from a position close to the injection hole (inner hole of the nozzle) while suppressing the inflow of the inert gas into the molten steel in the mold. For the purpose of further reducing the chance of recontamination of molten steel after removal of inclusions, multiple gas injection holes were installed on the circumference of the upper end surface of the upper nozzle centered on the center of the injection hole. An upper nozzle for continuous casting is disclosed in which the relationship between the total cross-sectional area A (m 2 ) and the volume Vg (m 3 ) of the flow path through which the inert gas flows in the upper nozzle is within a specific range.
[0004]
　Since such a through-hole type nozzle is composed of a refractory material having a finer structure than a porous type refractory material, it is superior in corrosion resistance and wear resistance as compared with a porous type nozzle, but is inferior in heat impact resistance. Tend. Further, the through-hole portion is also a "defect" in the structure, and has a drawback that thermal or mechanical stress is concentrated and tends to be a starting point of fracture. In particular, when the discharge of molten steel is started or stopped or the flow rate is controlled by fitting the stopper to the upper end of the inner hole of the nozzle, the operation of the stopper itself such as directly applying impact or compression to the nozzle is mechanical. There is a high risk of destroying the through-hole type nozzle as an external force.
　For the purpose of providing a through-hole type nozzle that is hard to break, Patent Document 3 discloses a nozzle in which a through-hole that penetrates a nozzle body communicating with a gas pool is provided in a three-dimensional non-linear manner. There is.
[0005]
　On the other hand, in Patent Document 4, for the purpose of preventing blockage in the vicinity of the upper nozzle caused by inclusions in the molten steel, the upper end portion of the upper nozzle in contact with the portion where the molten steel flows and the portion in contact with the upper nozzle of the stopper head are provided. It is disclosed that a refractory material having a remarkable effect of suppressing clogging is disposed, and that the refractory material has a high Al 2 O 3 content or a high Mg O content that does not contain C element .
Prior art literature
Patent documents
[0006]
Patent Document 1: Japanese Patent
Application Laid-Open No. 6-297118 Patent Document 2: Japanese Patent Application Laid-Open No. 2017-64778
Patent Document 3: Japanese Patent Application Laid-Open No. 2013-184199
Patent Document 4: Japanese Patent Application Laid-Open No. 9-314292
Outline of the invention
Problems to be solved by the invention
[0007]
　As mentioned above, the gas discharge port, which is a through hole or slit, is also a defect in the integrated structure of the refractory, and mechanical stress or thermal stress is concentrated on the defect, which is also the starting point of fracture. Become. Moreover, destruction will occur in irregular directions and places. If the nozzle and stopper are broken in the mating area, the flow rate and distribution of gas discharge cannot be controlled, and the flow control and stopping functions of molten steel are impaired, resulting in serious problems such as the inability to maintain normal casting. May cause.
　Even if the structure is such that stress is difficult to concentrate in the gas discharge port or the through hole as the gas flow path as in Patent Document 3, there is still a risk of nozzle destruction.
　On the other hand, as in Patent Document 4, when a peculiar refractory material having excellent corrosion resistance and resistance to adhesion is partially arranged in the fitting region, the refractory material generally has a nozzle body having enhanced thermal impact resistance. It has a higher coefficient of thermal expansion and a higher elastic modulus than the refractory material for the main body. If such a peculiar refractory is installed in contact with the refractory for the main body, the risk of cracking the refractory for the main body also increases.
[0008]
　The problem to be solved by the present invention is to prevent irregular destruction of a nozzle or stopper having a gas discharge function starting from a gas discharge port or a gas passage path communicating with the gas discharge port, or even if destruction occurs. It is an object of the present invention to provide a nozzle and a structure of a nozzle and a stopper capable of preventing expansion.
　Furthermore, when a refractory material having a higher thermal expansion coefficient than the refractory material for the main body constituting the nozzle body is installed in the fitting area with the stopper, the nozzle and the nozzle capable of preventing irregular destruction of the nozzle body and the nozzle body. The purpose is to provide a nozzle and stopper structure.
Means to solve problems
[0009]
　The present invention is the nozzle and the structure of the nozzle and the stopper according to the following 1 to 11.
1. 1.
　A nozzle that fits with the stopper located below the stopper that controls the flow rate of molten steel in continuous casting of molten steel, and a refractory material for the fitting area in the fitting area including the contact portion with the stopper. A layer made of (hereinafter referred to as "refractory layer for fitting region") is provided, and the
　refractory layer for fitting region is a refractory material other than the refractory material for fitting region that constitutes the nozzle body. It is made of a refractory material different from (hereinafter referred to as "the refractory material for the main body"), and a
　gas discharge port is provided at least one of the boundary portions between the refractory material layer for the fitting region and the refractory material for the main body on the surface in contact with the molten steel. Equipped with a nozzle.
2. 2.
　The nozzle according to 1 above, wherein the gas discharge port is a plurality of through holes or slits.
3. 3.
　2. The nozzle according to 2, wherein the diameter of the through hole is 2 mm or less, and the width of the slit is 1 mm or less.
4.
　The refractory material for the fitting region is a refractory material having a carbon content of 5% by mass or less (including zero) (hereinafter referred to as “carbonless refractory material”), any one of the above 1 to 3 above. Nozzle described in.
5.
　The nozzle according to 4 above, wherein the carbonless refractory has a ZrO 2 content of 75% by mass or more, a carbon content of 5% by mass or less (including zero), and the balance is mainly composed of oxides.
6.
　The carbonless refractory has a spinel (Al 2 O 3 , MgO) content of 75% by mass or more, a carbon content of 5% by mass or less (including zero), and the balance is mainly composed of oxides. Nozzle described in.
7.
　The refractory for the main body is a refractory whose main component is a refractory raw material selected from alumina, alumina-silica, spinel, zircon and magnesia, any one of 1 to 6 above. Nozzle described in.
8.
　A structure of a nozzle and a stopper including the nozzle and the stopper according to any one of the above 1 to 7,
　wherein the stopper is provided with a gas discharge port below the contact portion with the nozzle. A nozzle and stopper structure in which the gas discharge port of the stopper is one or more through holes or slits.
9.
　The nozzle and stopper structure according to item 8, wherein the diameter of the through hole of the stopper is 2 mm or less, and the width of the slit is 1 mm or less.
10.
　8. The structure of a nozzle and a stopper according to 8 or 9, wherein a refractory layer for the fitting region is provided in at least a part of the fitting region of the stopper including a contact portion with the nozzle.
11.
　A nozzle-stopper structure including the nozzle-stopper according to any one of 1 to 7 above, wherein at least a part of the fitting region of the stopper including a contact portion with the nozzle. A nozzle and stopper structure comprising the refractory layer for the mating area.
[0010]
　Here, the "nozzle located below the stopper that controls the flow rate of molten steel in continuous casting of molten steel and mating with the stopper" is typically installed at the bottom of the tundish and pouring water below it. A nozzle called a tundish nozzle or an upper nozzle having a structure for connecting other nozzles for use, or a nozzle mounted in the tundish like the tundish nozzle or the upper nozzle, but below that, a typical one is Refers to a dipping nozzle that extends to the mold and is immersed in the mold.
The invention's effect
[0011]
　According to the present invention, in a nozzle or stopper having a gas discharge function, it is possible to prevent irregular destruction of the nozzle starting from the gas discharge port or a gas passage path communicating with the gas discharge port, or to prevent the spread of the destruction.
　Further, when a refractory material having a larger thermal expansion coefficient than the refractory material for the main body is installed as the refractory material layer for the fitting region, it is possible to prevent irregular destruction of the nozzle body or prevent the spread of the destruction. ..
　Furthermore, by applying a carbonless refractory as the refractory layer for the fitting part, it is possible to prevent the inclusions in the molten steel from adhering to the mating area, and it is possible to maintain the control function such as the flow rate of the molten steel for a long time. Can be.
A brief description of the drawing
[0012]
[Fig. 1] An example of a nozzle provided with a gas discharge port of the present invention, which is a cross-sectional view in the axial (longitudinal) direction shown together with a fitting state with a stopper.
FIG. 2 is an axial (vertical) cross-sectional view showing another example of a nozzle provided with a gas discharge port of the present invention together with a fitting state with a stopper.
FIG. 3 is an example in which the structure of the nozzle and the stopper shown in FIG. 1 is further provided with one gas discharge port which is a through hole at the tip of the stopper.
FIG. 4 is an example in which the structure of the nozzle and the stopper shown in FIG. 1 is further provided with a gas discharge port which is a plurality of through holes or slits at the tip of the stopper.
[Fig. 5] In the nozzle and stopper shown in Fig. 2, an example in which a refractory layer for the fitting area is further installed in the fitting area on the stopper side.
FIG. 6 is a plan view (image) of the upper view showing an arrangement example of the gas discharge port of the nozzle provided with the gas discharge port of the present invention.
FIG. 7 is a plan view (image) of the downward view showing an arrangement example of the gas discharge port of the stopper provided with the gas discharge port of the present invention.
[Fig. 8] An example showing the amount of alumina adhered to different refractories.
[Fig. 9] An example showing ventilation characteristics by a water model experiment with through-hole diameters of 5 mm and 2 mm and a slit width of 1 mm.
FIG. 10 is an example showing a bubble diameter distribution by a water model experiment with through hole diameters of 5 mm and 2 mm and a slit width of 1 mm.
Mode for carrying out the invention
[0013]
　A mode for carrying out the present invention will be described.
[0014]
　In the fitting region (see, for example, FIG. 1), which is the region including the contact portion between the stopper and the nozzle, a collision or the like occurs between the stopper and the nozzle due to the raising and lowering operation of the stopper and the vibration of the stopper during molten steel flow. Furthermore, when gas is discharged from the gas discharge port and blown into the molten steel, vibration due to the gas also causes mechanical stress inside the nozzle and stopper.
　Further, in the mating region, a large thermal change occurs at the time of preheating, at the start of passing through molten steel, or due to gas discharge (cooling), and thermal stress is generated inside the nozzle and stopper.
[0015]
　On the other hand, stress is concentrated on the portion (boundary portion) provided with a boundary that interrupts the continuity of the refractory that constitutes the nozzle or stopper, and tends to be the starting point of fracture.
　However, although these boundaries are not at a high level, they have a stress relaxation function.
[0016]
　Conventionally, in general, such a boundary portion has the following form.
(1) A form having a fault that is made of the same material but interrupts continuity, for example, a molded body is prepared in advance, and a clay is loaded so as to be in contact with the molded body to form an integral molded body. A form to be manufactured, or a form in which a plurality of molded bodies are integrally fixed in a state of being simply in contact with each other.
(2) A form in which different materials are combined, for example, a molded body is prepared in advance from one material, and a clay of another material is loaded so as to be in contact with the molded body to prepare an integrated molded body. Or a form in which each molded product made of a plurality of different materials is integrally fixed in a state of being simply in contact with each other.
(3) A form in which the same material or different materials are combined, but a layer of a different material such as mortar is provided between them.
　Here, the plurality of refractory parts (molded bodies) having structural boundaries may be the same or different types of refractories.
[0017]
　On the other hand, the gas discharge port or the gas passage path communicating with the gas discharge port is a void, that is, a defect in the refractory tissue, and stress is concentrated on this defect portion as well, and it is likely to be a starting point of fracture.
　On the other hand, such voids have a function of absorbing or relaxing various stresses in the refractory structure.
[0018]
　Based on the above considerations, in the present invention, the gas discharge port, which is the starting point of such further fracture, is integrated / continuous with the fitting region or fitting region of the nozzle and stopper, which is important for controlling the flow rate of molten steel. It was decided to place it at the above-mentioned boundary without existing in the area it has. That is, in the present invention, the occurrence of fracture or the spread of fracture is further suppressed or expanded by superimposing a gas discharge port as a void having a further stress relaxation function on the boundary portion having a stress relaxation function although it is at a low level. Can be prevented.
　The cooling effect associated with the gas discharge from the gas discharge port suppresses the temperature rise of the refractory and reduces the stress caused by the thermal expansion of the refractory (particularly the inner hole side or the upper end side of the nozzle). Effect can also be expected.
[0019]
　In the present invention, for example, in the nozzle 2 as shown in FIG. 1, when a cylindrical refractory layer 5A for a fitting region is installed near the upper end of the inner hole 4, the refractory for the fitting region is provided. It exists on the outer peripheral side of the layer 5A and in the lateral direction of the inner hole 4 (in the direction substantially perpendicular to the central axis in the vertical direction of the nozzle) on the lower side of the fitting region of the nozzle 2.
　The gas discharge port 8A can be installed on one or both of these boundary portions 9 on the surface in contact with the molten steel.
　Further, for example, as shown in FIG. 2, when the entire upper end portion of the nozzle 2 is used as the refractory layer 5A for the fitting portion, the inner hole 4 on the lower side of the fitting region of the nozzle 2 is laterally oriented (to the central axis in the vertical direction of the nozzle). The gas discharge port 8A can be installed on the surface of the boundary portion 9 in contact with the molten steel, which exists in a direction substantially perpendicular to the direction.
　In the nozzle 2 shown in FIGS. 1 and 2, the gas is introduced from the gas introduction hole 6 and discharged into the molten steel from the gas discharge port 8 via the gas pool 7.
[0020]
　In the present invention, the gas discharge port may be a plurality of through holes or slits. The stress relaxation function differs slightly depending on the number and size of through holes, the size (width) of slits, etc., but it may be determined according to individual operating conditions such as the balance with the amount of gas.
　In the case of a plurality of through holes, from the viewpoint of obtaining a stress relaxation function as uniform as possible on the entire circumference of the boundary portion, it is preferable that the number of through holes is approximately 8 or more, although it depends on the size of the boundary portion.
[0021]
　Here, according to the findings of the present inventors, the diameter of the through hole is 2 mm or less and the width of the slit is 2 mm or less from the viewpoint of optimizing the bubble diameter of the gas in the molten steel, which affects the floating effect of inclusions in the molten steel container or the mold. Is preferably 1 mm or less. The reason is that the gas discharge amount can be controlled with higher accuracy, and the proportion of small-diameter bubbles (generally less than 3 mm) that easily float the inclusions in the molten steel and are less likely to cause steel defects is large. The results of these water model experiments are shown in FIGS. 9 and 10.
[0022]
　By the way, even if the gas is discharged into the molten steel, inclusions in the molten steel (non-metal inclusions) mainly composed of alumina may adhere to the nozzle or stopper. The above-mentioned mating region has the greatest effect on flow control.
[0023]
　Therefore, in the present invention, a refractory (carbonless refractory) having a carbon content of 5% by mass or less (including zero), which has resistance to non-metal inclusions, is installed in this fitting region. Can be done.
　Adhesion of non-metal inclusions is a phenomenon that appears as a composite result of various behaviors depending on the composition of the refractory, but it also depends on the carbon content in the refractory in contact with the molten steel. The main cause is that carbon elutes into the molten steel at a high rate and the refractory structure becomes rough.
　In the laboratory and in actual operation, the present inventors set the carbon content of the refractory installed in this fitting region to 5% by mass or less (including zero) of the refractory to make it difficult to adhere. It was found that there was a significant improvement.
　This carbonless refractory may be alumina or alumina-silica, but the present inventors have a ZrO 2 content of 75% by mass or more or spinel (Al 2 O 3 , MgO) in a laboratory and actual operation. It was found that a material having a content of 75% by mass or more and the balance mainly composed of an oxide such as alumina is more preferable.
[0024]
　On the other hand, the refractory material for the main body (reference numeral 2A in FIGS. 1 to 5) constituting the nozzle body is mainly composed of a refractory raw material selected from alumina-based, alumina-silica, spinel-based, zircon-based or magnesia-based. It can be a refractory material. High thermal shock resistance is required for nozzles, especially long immersion nozzles. Therefore, also in the present invention, a material containing about 12 to about 30% by mass of a carbon component can be used as in the case of a general refractory for a main body.
[0025]
　The thermal expansion of the carbonless refractory (about 1.0 to about 1.4% at 1500 ° C.) is the thermal expansion of such a refractory for the main body (in the case of alumina with a carbon content of about 25% by mass). Since it is larger than about 0.5 to about 0.6% at 1500 ° C.), when this carbonless refractory is installed inside or above the main body refractory, these are particularly integrated or continuous structure. In some cases, the carbonless refractory often breaks the refractory for the main body.
　Therefore, it is preferable to apply the present invention when these carbonless refractories are applied to the “refractory layer for fitting region”.
[0026]
　By providing the carbonless refractory (refractory layer for the fitting region) (reference numeral 5B in FIG. 5) in at least a part of the fitting region of the stopper, the non-metal inclusions in the fitting region are resistant to adhesion. The function can be enhanced, or the effect of levitation of inclusions in the mold can be enhanced.
　The carbonless refractory material (refractory layer for the fitting area) to be applied to the nozzle fitting area and the stopper fitting area need not be the same material. For example, in the fitting region of the nozzle, as a carbonless refractory (refractory layer for the fitting region), "ZrO 2 content is 75% by mass or more, carbon content is 5% by mass or less (including zero), and the balance. A material "is mainly composed of oxides" is applied, and the content of "spinel (Al 2 O 3 , MgO) is 75% by mass or more as a carbonless refractory (refractory layer for the fitting region) in the fitting region of the stopper . Materials with a carbon content of 5% by mass or less (including zero) and the balance consisting primarily of oxides can also be applied.
[0027]
　In the present invention, for example, as shown in FIGS. 3 to 5, the stopper 1 can also be provided with the gas discharge port 8B. The gas discharge port 8B in the stopper 1 is provided below the contact portion with the nozzle 2, and may be one or a plurality of through holes or slits. Also in the stopper, the diameter of the through hole is preferably 2 mm or less, and the width of the slit is preferably 1 mm or less.
　In the stopper 1 shown in FIGS. 3 to 5, the gas is introduced into the inner hole 3 of the stopper, and is discharged into the molten steel from the gas discharge port 8B via the inner hole 3.
[0028]
　In the nozzle or stopper, either the refractory material for the fitting region or the refractory material for the main body may be arranged between the plurality of through holes as the gas discharge port. In other words, one of the through holes is in contact with the refractory for the mating area and the refractory for the main body, but they can also be buried in either the refractory for the mating area or the refractory for the main body. It may be in the middle of.
　Further, a mortar may be arranged between the refractory material for the fitting region and the refractory material for the main body, and a through hole may be arranged therein.
[0029]
　FIG. 6 shows an arrangement example of the gas discharge port 8A in the nozzle.
　FIG. 6A shows an example in which the inner holes 4 side of the plurality of through holes 8A are in contact with the refractory layer 5A for the fitting region, and the refractory material 2A for the main body is arranged between the plurality of through holes 8A.
　FIG. 6B is an example in which the nozzle outer peripheral side of the plurality of through holes 8A is in contact with the refractory material 2A for the main body, and the refractory layer 5A for the fitting region is arranged between the plurality of through holes 8A.
　FIG. 6C shows an example in which the gas discharge port 8A is a substantially continuous annular slit. The reason why the "almost continuous annular shape" is used is that a joint portion is partially required between the refractory material 2A for the main body and the refractory layer 5A for the fitting region (boundary portion).
　FIG. 6D shows an example in which a plurality of through holes 8A are arranged in the mortar 10.
[0030]
　FIG. 7 shows an arrangement example of the gas discharge port 8B in the stopper.
　FIG. 7A shows an example in which one through hole 8B is arranged
　. In FIG. 7B, the stopper center side of the plurality of through holes 8B is in contact with the refractory material 1A for the main body, and the plurality of through holes 8B are arranged . This is an example in which the refractory layer 5B for the fitting region is arranged between the two.
　FIG. 7C shows an example in which the outer peripheral side of the stopper of the plurality of through holes 8B is in contact with the refractory layer 5B for the fitting region, and the refractory material 1A for the main body is arranged between the plurality of through holes 8B.
　FIG. 7D shows an example in which the gas discharge port 8B is a substantially continuous annular slit. The reason for the "almost continuous ring" is as described above.
　FIG. 7 (E) shows an example in which a plurality of through holes 8B are arranged in the mortar 10.
Example
[0031]

　The stress relaxation effect when a plurality of through holes are provided at the boundary between the refractory layer for the fitting region (carbonless refractory) and the refractory for the main body is finite based on the knowledge so far. Table 1 shows the results of simple calculations by the element method.
　In Table 1, when the "integral" of the molding method is a continuous structure in which the clay of different refractories is molded simultaneously and integrally, the "division" is to fix the separately molded ones with open joints. Refers to the case. Further, the maximum generated stress index is indexed with the maximum generated stress of Comparative Example 1 as 100, and the smaller the maximum generated stress index is, the better the stress relaxation function is.
[0032]
[table 1]

[0033]
　Comparing Comparative Example 1 and Example 1 in which the molding method is "integral", it can be seen that Example 1 having a through hole is superior in stress relaxation function. Further, when comparing Comparative Example 2 and Example 2 in which the molding method is "division", it can be seen that Example 2 provided with a through hole is superior in stress relaxation function.
[0034]

　FIG. 8 shows the amount of alumina adhering to different refractories. This is a compilation of multiple findings in the laboratory and in production.
　In addition, sample No. 2, 7 and 10 do not contain carbon.
　In FIG. 8, the alumina adhesion amount of each sample is shown by the alumina adhesion amount index in which the alumina (also referred to as “AG material”) having a carbon content of 25% by mass, which is mainly graphite, is 1.
　From FIG. 8, it can be seen that the amount of alumina adhering to each of the carbonless refractories is reduced. That is, when the carbon content is 5% by mass or less, a remarkable effect of reducing the amount of alumina adhered is observed.
　Further, in the zirconia (ZrO 2 ) -based material and the spinel-based material, a remarkable effect of reducing the amount of alumina adhesion is observed when the content of zirconia or spinel is about 75% by mass or more, but a more remarkable effect is observed when the content of zirconia or spinel is about 80% by mass or more. It turns out that it can be obtained.
Code description
[0035]
　1 Stopper
　1A Refractory for the main body of the stopper
　2 Refractory
　2A Refractory for the main body of the nozzle (Refractory other than the refractory for the fitting area)
　3 Inner hole of the stopper
　4 Inner hole of the nozzle
　5A, 5B Refractory for the fitting area (Carbonless refractory)
　6 Gas introduction hole
　7 Gas pool
　8A, 8B Gas discharge port (through hole or slit)
　9 Boundary between fitting area refractory (carbonless refractory) and main body refractory
　10 mortar
The scope of the claims
[Claim 1]
　A nozzle for continuous casting (hereinafter simply referred to as "nozzle") that is located below a stopper that controls the flow rate of molten steel and fits with the stopper in continuous casting of molten steel, and includes a contact portion with the stopper. A layer made of a refractory material for the fitting region (hereinafter referred to as “a refractory material layer for the fitting region”) is provided in the
　mating region, and the refractory material layer for the fitting region constitutes a nozzle body. It is composed of a refractory material different from the refractory material other than the refractory material for the fitting region (hereinafter referred to as "fireproof material for the main body"), and the
　refractory material layer for the fitting region and the refractory material for the main body on the surface in contact with the molten steel. A nozzle with a gas outlet at least one of its boundaries.
[Claim 2]
　The nozzle according to claim 1, wherein the gas discharge port is a plurality of through holes or slits.
[Claim 3]
　The nozzle according to claim 2, wherein the diameter of the through hole is 2 mm or less, and the width of the slit is 1 mm or less.
[Claim 4]
　The refractory for the fitting region is any of claims 1 to 3, wherein the refractory has a carbon content of 5% by mass or less (including zero) (hereinafter referred to as "carbonless refractory"). The nozzle according to one item.
[Claim 5]
The nozzle according to claim 4, 　wherein the carbonless refractory has a ZrO 2 content of 75% by mass or more, a carbon content of 5% by mass or less (including zero), and the balance mainly composed of an oxide.
[Claim 6]
　The carbonless refractory has a spinel (Al 2 O 3 , MgO) content of 75% by mass or more, a carbon content of 5% by mass or less (including zero), and the balance is mainly composed of oxides. 4. The nozzle according to 4.
[Claim 7]
　The refractory for the main body is any of claims 1 to 6, wherein the refractory is mainly composed of a refractory raw material selected from alumina, alumina-silica, spinel, zircon, and magnesia. The nozzle according to paragraph 1.
[Claim 8]
　A structure of a nozzle and a stopper including the nozzle and the stopper according to any one of claims 1 to 7,
　wherein the stopper is provided with a gas discharge port below the contact portion with the nozzle. A structure of a nozzle and a stopper in which the gas discharge port of the stopper is one or more through holes or slits.
[Claim 9]
　The structure of a nozzle and a stopper according to claim 8, wherein the diameter of the through hole of the stopper is 2 mm or less, and the width of the slit is 1 mm or less.
[Claim 10]
　The structure of the nozzle and the stopper according to claim 8, wherein the refractory layer for the fitting region is provided in at least a part of the fitting region of the stopper including the contact portion with the nozzle. body.
[Claim 11]
　A structure of a nozzle and a stopper including the nozzle and the stopper according to any one of claims 1 to 7, wherein at least a part of the fitting region of the stopper including a contact portion with the nozzle. A nozzle and stopper structure provided with a fireproof layer for the fitting region.