JP5291662B2 - Refractory, continuous casting nozzle using the refractory, method for producing the continuous casting nozzle, and continuous casting method using the continuous casting nozzle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent attachment of Al<SB POS="POST">2</SB>O<SB POS="POST">3</SB>inclusion or the like to the inside of a nozzle to be used or clogging due to the inclusion in a continuous casting operation using a steel type such as an aluminum-killed steel which particularly tends to take place a nozzle clogging phenomenon. <P>SOLUTION: There is provided a refractory 10 which contains, by mass, &ge;0.5% of CaO, &ge;0.5% of either B<SB POS="POST">2</SB>O<SB POS="POST">3</SB>or R<SB POS="POST">2</SB>O (R is Na, K or Li) or of the sum of those, &ge;50% of Al<SB POS="POST">2</SB>O<SB POS="POST">3</SB>, 8.0-34.5% of free carbon, and 1.0-15.0% of (CaO+B<SB POS="POST">2</SB>O<SB POS="POST">3</SB>+R<SB POS="POST">2</SB>O) and has a mass ratio CaO/(B<SB POS="POST">2</SB>O<SB POS="POST">3</SB>+R<SB POS="POST">2</SB>O) of &ge;0.1 and &le;3.0. The above attachment of or clogging due to the inclusion is prevented by disposing the refractory on a part of or the whole of a surface contacting the molten steel in the nozzle for continuous casting. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a refractory which suppresses or prevents the inclusion from inclusions from molten steel ("suppression or prevention" is hereinafter simply referred to as "prevention"), a continuous casting nozzle using the refractory, and a nozzle for continuous casting And a continuous casting method using the continuous casting nozzle.

  The nozzle for continuous casting that is the subject of the present invention is a general nozzle used for continuous casting of molten steel, and particularly, an immersion nozzle. A typical example is a tubular refractory structure having an inner hole through which molten steel passes in the axial direction, but other irregular shapes are also targeted.

  In the present invention, “axial direction” refers to the long direction of the continuous casting nozzle, and “tubular” refers to all shapes having an inner hole in the axial direction, and a cross section in a direction perpendicular to the axial direction. The shape is not limited. That is, the cross-sectional shape in the direction orthogonal to the axial direction is not limited to a circle, and may be an elliptical shape, a rectangle, a polygon, or the like.

In recent years, non-metallic inclusions in molten steel such as Al ₂ O ₃ accompanying the upgrading of steel (in the present invention, non-metallic inclusions, Al ₂ O ₃ inclusions and inclusions are almost synonymous). The inclusion of inclusions centering on Al ₂ O ₃ on the inner hole surface of the continuous casting nozzle or the blockage of the inner hole is one of the major factors that determine the life of the continuous casting nozzle. Yes.

In such a situation, there is an increasing demand for continuous casting nozzles with high durability by preventing non-metallic inclusions from adhering to or blocking the inner hole surface. Therefore, various proposals have been made regarding the refractory layer on the inner hole surface side of the nozzle for continuous casting in order to prevent inclusion components such as Al ₂ O ₃ from the molten steel from adhering to the inner hole surface. .

For example, in Patent Document 1, at least the inner hole part of the nozzle and / or the part in contact with the molten steel does not contain a carbon component, SiO ₂ is 5 to 10% by weight, and Al ₂ O ₃ is 90 to 95% by weight. There is shown a continuous casting nozzle composed of an Al ₂ O ₃ —SiO ₂ based refractory material having a main mineral phase of mullite and corundum and / or β-Al ₂ O ₃ .

However, such a refractory material that does not contain a carbon component has extremely low resistance to thermal shock, and in particular, there is a high risk of destruction due to thermal shock such as at the start of molten steel injection. Moreover, even if it does not contain a carbon component, such an Al ₂ O ₃ —SiO ₂ refractory material can sufficiently prevent the inclusion of inclusions centering on Al ₂ O ₃ or blockage of inner holes. I can't.

Therefore, the material of the refractory layer on the inner hole surface side contains a large amount of CaO component that easily reacts with inclusions centering on Al ₂ O ₃ to generate a low-melting matter, so that the inclusions do not adhere. Many proposals have been made to prevent the inner hole from being blocked.

  For example, Patent Document 2 shows that a lining layer of a composition containing 40 to 90% by weight of CaO, 0 to 50% by weight of MgO and 0 to 20% by weight of C is disposed in the inner hole of the nozzle. Yes. However, in such a lining layer, especially when the content of CaO is large, CaO exists as a free lime that is very easily hydrated. . Further, such a composition such as CaO has a very large thermal expansion property, and the outer main body layer, that is, the continuous casting nozzle itself is destroyed by the thermal expansion of the lining layer by this composition.

For such problems of CaO, for example, Patent Document 3 contains 16 to 35% by weight of CaO, 20 to 95% by weight of calcium zirconate-based clinker mainly composed of CaZrO ₃ , 5 to 50% by weight of graphite, etc. A ZrO ₂ —CaO-containing nozzle for continuous casting made of zirconia clinker containing 3 to 35% by weight of CaO (containing CubicZrO ₂ and CaZrO ₃ as a mineral composition) is 40 to 85%. %, Graphite, 10-30% by weight, silica 1-15% by weight, and magnesia 1-15% by weight. A nozzle is shown. In these materials, CaO is not present as a free lime, so that it is present as a mineral having a crystal structure with ZrO ₂ or the like.

However, in a refractory composed of such components, the effect of preventing the inclusion components such as Al ₂ O _{3 from} adhering to the inner hole surface in actual continuous casting operation is small, and a sufficient continuous casting nozzle The service life cannot be ensured. Moreover, although the problem of digestion can be solved, the thermal expansibility is lowered to the same level as that of Al ₂ O ₃ -graphitic refractory in the main body of a general continuous casting nozzle located outside the inner hole side layer. However, with a structure in which these are integrally installed, the continuous casting nozzle cannot be sufficiently prevented from being damaged by thermal shock.

  In order to install such a layer having a high thermal expansion property on the inner hole side, it is necessary to improve the thermal shock resistance on the structural surface of the continuous casting nozzle. For example, in Patent Document 5, a base material nozzle is externally mounted on a CaO nozzle made of a refractory having a CaO content of 70% by weight or more and an apparent porosity of 50% or less, and an inner hole side CaO nozzle and an outer base material nozzle are provided. A casting nozzle is shown in which a gap corresponding to the thermal expansion allowance of the CaO nozzle is provided therebetween.

  However, such a special structure such as providing a gap between the inner hole side layer and the outer peripheral side layer has a problem that it becomes difficult to provide a continuous casting operation as a normal integral molded body. . In addition, there is a problem that the risk of causing displacement or peeling of the inner hole side layer or damage or destruction of the continuous casting nozzle is increased.

Further, in the cited document 6, a continuous casting nozzle for reducing the amount of non-metallic inclusions adhering to the nozzle and preventing clogging can be manufactured at low cost, and the composition is Al ₂ O. ₃ ; 20 to 80% by weight, graphite; 10 to 45% by weight, SiO ₂ ; 1 to 20% by weight, and CaO; less than 0.1 to 3% by weight or an oxide of a IIa group element other than Ca; A continuous casting nozzle is shown which uses refractories of 1 to 5% by weight in whole or in part.

However, the refractory having this composition merely generates a low-melting material by the reaction of Al ₂ O ₃ , SiO ₂ and CaO in the entire refractory containing these components. That is, although SiO ₂ volatilizes and moves, CaO and Al ₂ O ₃ do not move from the position where they originally existed, and an Al ₂ O ₃ —CaO-based melt is formed in the tissue. The SiO ₂ component dispersed in the melt is also absorbed by the melt, and the liquid phase further proceeds, and is stabilized in the structure as CaO—Al ₂ O ₃ —SiO ₂ . High film formation becomes difficult. Furthermore, with the passage of time after the start of casting, these refractory components are supplied from the Al ₂ O ₃ and SiO ₂ aggregates to the melt side, so that the amount of low-melting material increases, and in terms of hot strength and corrosion resistance It becomes a problem.

That is, with this composition, a sufficiently low melt cannot be generated between the Al ₂ O ₃ inclusions in contact with the working surface, and the adhesion preventing effect of the Al ₂ O ₃ inclusions must be extremely limited. Absent. For this reason, with the passage of time, Al ₂ O ₃ inclusions tend to adhere within a relatively short time. In addition, Al in the molten steel is oxidized by SiO (gas) released from the working surface, which tends to promote the generation and adhesion of Al ₂ O ₃ . For this reason, the Al ₂ O ₃ —SiO ₂ —CaO-based material having the composition is not widespread as a difficult adhesion material.

  Thus, when a CaO-based refractory is arranged on the inner hole side, it often has many difficult problems such as structure, manufacturing, handling, performance, etc. There are still many unresolved issues in the industry, such as cost.

JP-A-10-128507 Japanese Patent Laid-Open No. 01-289549 Japanese Patent Publication No. 02-023494 Japanese Patent Publication No. 03-014540 Japanese Patent Application Laid-Open No. 07-232249 JP 2001-179406 A

The problem to be solved by the present invention is to prevent adhesion or clogging of Al ₂ O ₃ inclusions or the like in the nozzle used in continuous casting operation particularly in a steel type in which nozzle clogging is likely to occur, such as aluminum killed steel. . In addition, the problem of cracking caused by the high expansion inherent in the CaO-containing refractory as proposed in the prior art for the purpose of preventing adhesion of Al ₂ O ₃ inclusions, etc. has been solved. It is possible to produce a nozzle having a more stable structure than a divided structure (for example, a structure in which an inner hole body and a main body are formed of separate parts) even in operation, which can be manufactured more inexpensively and easily than a CaO-containing refractory. An object of the present invention is to provide a refractory material to be used, a continuous casting nozzle using the refractory material, a method for producing the continuous casting nozzle, and a casting method using the continuous casting nozzle.

The present invention is as follows.
[Claim 1]
The CaO component is 0.5% by mass or more, the total amount of either or both of B ₂ O ₃ and R ₂ O (R is any one of Na, K, and Li) is 0.5% by mass or more, Al ₂ O ₃ 50 mass% or more, free carbon is contained 8.0 mass% or more and 34.5 mass% or less, and the total of CaO, B ₂ O ₃ and R ₂ O is 1.0 mass% or more and 15.0 mass%. or less, the mass ratio _{CaO / (B 2 O 3 +} R 2 O) is in the range of 0.1 to 3.0, 1000 ° C. aeration rate at room temperature after firing under a non-oxidizing atmosphere, When R of the R ₂ O component is Na, the range is 0.4 × 10 ⁻³ to 4.0 × 10 ⁻³ cm ² / (cmH ₂ O · sec), and when R is K, 1.5 In the range of × 10 ⁻³ to 4.0 × 10 ⁻³ cm ² / (cmH ₂ O · sec), when R is Li, 2.2 × 10 ^-3 to 4.0 × ¹⁰ -3 ^cm 2 _/ refractory in the range of _(cmH 2 O · sec).
[Claim 2]
The refractory according to claim 1, wherein the ZrO ₂ content is 6% by mass or less (including zero).
[Claim 3]
A continuous casting nozzle in which the refractory according to claim 1 or 2 is disposed on a part or all of a surface in contact with molten steel.
[Claim 4]
An integral structure in which a layer in which the refractory according to claim 1 or 2 is arranged on a part or all of a surface in contact with molten steel is directly joined to a layer adjacent to the layer and made of other than the refractory. The nozzle for continuous casting according to claim 3.
[Claim 5]
A method for producing a continuous casting nozzle in which the refractory according to claim 1 or 2 is disposed on a part or all of a surface in contact with molten steel,
A part of or all of the layer composed of the refractory according to claim 1 or 2 in the nozzle for continuous casting is formed into a soil composed of a portion other than the refractory adjacent to the layer, and the earth provided for the molding. A method for producing a nozzle for continuous casting, comprising a step of simultaneously pressing adjacent soils to form a molded body having an integral structure.
[Claim 6]
Using a continuous casting nozzle in which the refractory according to claim 1 or 2 is disposed on a part or all of a surface in contact with molten steel, Al ₂ O ₃ inclusions on the wall surface of the continuous casting nozzle, etc. Continuous casting method that prevents adhesion of inclusions.

In the present invention, “R” of “R ₂ O” is any one of Na, K, and Li as described above. Therefore, “R ₂ O” is any of Na ₂ O, K ₂ O, and Li ₂ O. It is. However, “R ₂ O” is not limited to any one of Na ₂ O, K ₂ O, and Li ₂ O, and a plurality of them may coexist. .

  In the present invention, the chemical component value is based on the measured value of the sample after heat treatment in a non-oxidizing atmosphere at 1000 ° C.

  This will be described in detail below.

In order to solve the above-mentioned problems, the present invention forms a dense and viscous film on the working surface of a refractory that comes into contact with molten steel, and continuously forms and maintains the film, whereby Al ₂ O ₃ inclusions are formed. The basic principle is to prevent the adhesion of

  The dense and viscous coating is a coating layer including a molten slag layer, and this coating layer on the surface of the refractory is also referred to as a “semi-melted slag coating layer” or simply “slag coating layer” in the present invention. .

It is important that the semi-molten slag coating layer in the present invention is a dense and viscous liquid phase in the mechanism of removing Al ₂ O ₃ inclusions.

A slag coating layer having a dense and viscous liquid phase is a slag phase, which is a working layer of a refractory, that is, a film-like layer existing between a molten steel and a refractory, and within the slag phase. A state in which a component such as CaO, Al ₂ O _{3 and the} like is in a molten state that can move and the slag coating layer maintains a viscosity that does not easily flow out due to the molten steel flow. . Further, in the present invention, the slag phase means a structure containing a refractory part in a molten state, and the molten part may contain a glass phase or a melt other than the glass phase. In addition, a state in which crystal grains or the like that do not constitute or in a molten state coexist is included.

The refractory of the present invention is a carbon-containing refractory, and the refractory structure is a reducing atmosphere. In this refractory, CaO and an oxide which is a component of low melt and increases volatility especially in a reducing atmosphere, that is, either or both of B ₂ O ₃ and R ₂ O are dispersed in a predetermined amount. . By reacting these with a refractory aggregate mainly composed of Al ₂ O ₃ at a molten steel temperature level, a viscous molten slag phase is formed to form a slag coating layer on the surface of the refractory, and Al ₂ O _{3 and the} like are interposed. Prevent adhesion of objects.

The slag coating layer prevents Al ₂ O ₃ inclusions and the surface of the refractory from coming into direct contact with each other, smoothes the unevenness of the surface of the refractory, and makes microscopic disturbance of the molten steel near the very surface of the refractory. The effect of suppressing the flow (molten steel vortex) is obtained. Suppression of the molten steel vortex near the very surface of the refractory suppresses the collision of non-metallic inclusions such as Al ₂ O ₃ suspended in the molten steel due to the inertial force of the molten steel vortex on the refractory surface. become. As a result, adhesion of Al ₂ O ₃ inclusions is suppressed.

In addition, the dense and viscous slag coating layer on the refractory operating surface has a high coverage of the refractory surface, and there are almost no open pores in the coating layer itself. It becomes possible to suppress the dissolution of the components into the molten steel, and to prevent the inclusion phenomenon of inclusions such as Al ₂ O ₃ . This is due to the following mechanism. When the refractory comes into direct contact with the molten steel and refractory components such as C and Si dissolve into the molten steel, the surface tension gradient of the molten steel (near the refractory) due to the solute concentration gradient in the molten steel near the refractory surface. The surface tension in the molten steel becomes smaller. On the other hand, inclusions in molten steel such as Al ₂ O ₃ tend to move toward the lower surface tension of the molten steel, so that the Al ₂ O ₃ adhesion phenomenon near the very surface of the refractory is promoted.

In addition, the presence of a CaO-based molten slag coating layer at the molten steel / refractory working interface also has the effect of causing a desulfurization reaction in the molten steel due to CaO, and the solute concentration of sulfur near the refractory surface (refractory-molten steel interface). With the decrease, the surface tension of the molten steel in the vicinity of the refractory surface tends to increase, so there is an effect of suppressing Al ₂ O ₃ adhesion.

  In order to form such a dense and viscous slag coating layer at the interface between the refractory and the molten steel, a component constituting the slag phase in the refractory structure (hereinafter also referred to as “slag component”). .) And the refractory composition excluding its components, while it is necessary to ensure the formation of the slag coating layer on the working surface of the refractory (synonymous with the interface with molten steel).

The present inventors investigated how these slagging components affect the Al ₂ O ₃ adhesion phenomenon at a molten steel flow rate by a rotating test method in molten steel, and obtained the following knowledge.
1. When a refractory is tested in a rotating test method in molten steel, when a semi-molten slag coating layer with a coverage of 50% or more and a thickness of 0.1 mm or more is formed on the surface of the refractory, continuous casting of steel It is possible to remarkably suppress the Al ₂ O ₃ adhesion phenomenon.
2. The refractory for obtaining the slag coating layer in the molten steel in-rotation test method is 0.5% by mass or more of the CaO component, B ₂ O ₃ and R ₂ O (R is any one of Na, K, and Li). The total amount of either or both is 0.5% by mass or more, Al ₂ O ₃ is contained by 50% by mass or more, free carbon is contained by 8.0% by mass or more and 34.5% by mass or less, and CaO, B ₂ O ₃ and R ₂ O are 1.0 mass% or more and 15.0 mass% or less, and mass ratio CaO / (B ₂ O ₃ + R ₂ O) is in the range of 0.1 or more and 3.0 or less. about.

In many conventional techniques, the effect of preventing the inclusion of inclusions such as Al ₂ O ₃ has decreased with the lapse of casting time. The cause is that in the refractory composition of the prior art, the reaction with Al ₂ O ₃ or the low melting is achieved only by the composition in the vicinity of the surface of the refractory that contacts the molten steel, and the main effect is the loss due to the molten steel flow. It depends. That is, a component (CaO or the like) that reacts with Al ₂ O ₃ inclusions in molten steel in the vicinity of the surface of the refractory is consumed over time, or a solid reaction layer is formed on the surface to form the solid phase. This is because the subsequent reaction with Al ₂ O ₃ inclusions in the molten steel is significantly reduced or eliminated. To obtain such a Al ₂ O ₃ adhesion preventing effect over a stable or long in the prior art, it is necessary to add a relatively large amount of reactive components such as CaO, in which case the Al ₂ Due to the reaction with other refractory components coexisting such as O ₃ aggregate, there are problems such as a decrease in hot strength, a decrease in thermal shock resistance, and a decrease in corrosion resistance.

In the present invention, the effect of preventing the adhesion of Al ₂ O ₃ inclusions can be maintained for a long time without stopping at the start of casting and for a short time after casting, and further hardly decreasing. That is, the present invention utilizes the concentration phenomenon of the volatile oxides (B ₂ O ₃ and R ₂ O) at the molten steel operating interface in a reducing atmosphere at the molten steel temperature level, and this volatile oxide and the main bone. By reacting the Al ₂ O ₃ component, which is a material, a dense and viscous slag coating layer containing a molten slag phase is continuously formed at the interface between the molten steel and the refractory, and a nozzle made of inclusions in the steel It is characterized by preventing the blockage phenomenon.

  This will be described in detail.

In a refractory containing carbon that is located at a location where molten steel passes at a high speed, such as a nozzle for continuous casting, the very surface (inner wall surface) of the refractory that contacts the molten steel is almost always exposed to negative pressure during casting. . Under such circumstances, volatile oxides are negative when B ₂ O ₃ and R ₂ O components, which are known to be more volatile (gasification) components than SiO ₂ components, are present in the carbon-containing refractory structure. It moves quickly to the molten steel / refractory interface on the compression side. (Although the SiO ₂ component has a lower volatility than these components, it has the ability to promote film formation by coexistence. However, the SiO ₂ component is less than 0.2% in order to suppress low melting in the structure. It is preferably used with a particle size of 21 mm or more.) As a result of the concentration of volatile components at the molten steel / refractory interface, a molten slag phase is formed at the molten steel / refractory interface.

The molten slag phase preferentially takes in the CaO component, which is a basic component dispersed in the matrix, and the B ₂ O ₃ component and R ₂ O component that have been evaporated and concentrated on the working surface, and CaO-rich CaO— B ₂ O ₃ system or _{CaO-R 2} O system or _{CaO-B 2 O 3 -R 2} O -based molten slag phase is continuously formed.

A part of the molten slag phase reacts with the Al ₂ O ₃ aggregate at the working interface, and a film-like layer containing a dense and viscous molten slag phase, that is, a slag coating layer is interposed between the molten steel and the refractory. Form continuously.

A coating-like slag coating layer, which is a slag phase containing a molten phase formed on the working surface while maintaining an appropriate viscosity in the vicinity of the molten steel temperature, is from the molten steel due to the smoothing action and protective film action of the refractory working surface. Inclusion particles such as Al ₂ O ₃ are allowed to flow into the molten steel without being fixed to the refractory. Moreover, in the present invention, the movement of the volatile component or the concentration phenomenon on the operating surface side and the formation of the slag coating layer occur continuously while casting (operation) continues. Unlike the prior art, the refractory according to the present invention enables the Al ₂ O ₃ inclusion adhesion preventing effect to be maintained for a long time by forming such a continuous slag coating layer.

  Hereinafter, each component and each element will be described.

CaO has the effect of reacting with the sulfur component derived from the molten steel in the slag coating layer on the surface of the refractory that comes into contact with the molten steel, and reducing the free sulfur concentration in the molten steel at the working interface. When the free sulfur concentration in the molten steel decreases, the surface tension of the molten steel tends to increase. Such a reaction increases the surface tension in the molten steel near the refractory surface of the present invention. As described above, non-metallic inclusions such as Al ₂ O ₃ move to the side where the surface tension of the molten steel is smaller. As a result of the increase in the surface tension of the molten steel near the refractory surface due to this change in sulfur concentration, Al _The frequency with which nonmetallic inclusions such as ₂ O ₃ come into contact with the refractory surface can be reduced. CaO also has a function of generating a low melt by reaction with Al ₂ O ₃ and flowing it down into the molten steel. CaO is also a component that lowers the viscosity of the slag phase, and has the effect of increasing the reactivity with the Al ₂ O ₃ aggregate, particularly at the molten steel temperature, and also functions to form a viscous slag phase. For such an action, the CaO amount needs to be 0.5% by mass or more in the refractory.

CaO is stable even in a reducing atmosphere and does not move to the surface of the refractory that comes into contact with the molten steel by vaporizing the refractory structure like volatile components such as B ₂ O ₃ and R ₂ O. However, Al ₂ O ₃ adhesion can be effectively suppressed in the semi-molten slag phase on the operating surface. That is, CaO can move in the slag phase in a semi-molten state, and reacts with inclusions such as Al ₂ O ₃ and S (sulfur) derived from molten steel in the slag phase, and its reactivity. It can contribute to raising. When the CaO component is less than 0.5% by mass, the above functions cannot be obtained sufficiently.

B ₂ O ₃ and R ₂ O are components that constitute the slag phase (slag component), and either or both of these components coexist, resulting in a viscous semi-molten slag phase at the working interface A coating layer is produced. Since these components are in a molten state from a lower temperature than the other components, they contribute to coating immediately after the refractory surface contacts the molten steel. Even when the slag is formed by other components not including these components in the CaO amount, it is difficult to maintain a coating film sufficient to suppress adhesion of inclusions such as Al ₂ O _{3 in the} initial stage of casting. . Further, B ₂ O ₃ and R ₂ O have a vapor pressure much higher than that of the SiO ₂ component even at a molten steel temperature level, and are particularly volatile under a reducing atmosphere, and can easily move through the refractory structure by volatilization.

On the other hand, on the refractory working surface (contact surface with molten steel; the same applies hereinafter), the semi-molten slag coating layer reacts with inclusions such as Al ₂ O ₃ from the molten steel and mechanical wear due to molten steel flow It disappears gradually due to etc. Volatile B ₂ O ₃ and R ₂ O components move continuously toward the refractory operating surface where they decrease during casting (operation).

The B ₂ O ₃ and R ₂ O components that have moved to the refractory working surface side are concentrated at the refractory working interface (interface with molten steel; hereinafter simply referred to as “working interface”) and react with CaO in the structure. Slag phase. The slag phase generated at the working interface increases the reactivity with the surrounding refractory aggregate (mainly Al ₂ O ₃ ) to form a viscous and refractory slag layer.

In this way, the B ₂ O ₃ and R ₂ O components are capable of continuing to form a viscous slag phase film on the refractory operating surface by movement to the continuous refractory operating surface due to volatilization. Is responsible.

The amount of either or both of B ₂ O ₃ and R ₂ O for the continuous formation of these semi-molten slag coating layers during the initial casting and during the continuous casting (operation) is: On the premise of the presence of the aforementioned amount of CaO, 0.5 mass% or more is necessary. If the amount of either B ₂ O ₃ or R ₂ O or the total amount of both is less than 0.5% by mass, the amount is relatively small relative to other refractory aggregates, and the semi-molten state The slag phase as a coating layer is not formed. Further, it is difficult to uniformly disperse and continuously move them. Incidentally, CaO, optimum values of B ₂ O ₃ and R _{2 O} amount may be determined by the molten steel rotating test method in accordance with the individual operational conditions.

Because of the necessary amount of each component described above, CaO and the total amount of either or both of B ₂ O ₃ and R ₂ O (total amount of CaO and B ₂ O ₃ or total amount of CaO and R ₂ O or The total amount of CaO, B ₂ O ₃ and R ₂ O is required to be 1.0% by mass or more, and the upper limit of these is 15.0% by mass or less. When the total amount of either or both of CaO and B ₂ O ₃ and R ₂ O exceeds 15.0% by mass, the progress of molten slag formation in the refractory structure in the temperature range of the molten steel temperature level increases. Therefore, problems such as a decrease in fire resistance, an increase in melting loss, and a decrease in strength are likely to occur.

Furthermore, in order to form a dense and viscous slag coating layer on the refractory operating surface, the total amount of CaO and any one or both of B ₂ O ₃ and R ₂ O is 1.0 mass% or more and 15.0%. In addition to being mass% or less, the mass ratio CaO / (B ₂ O ₃ + R ₂ O) needs to be in the range of 0.1 or more and 3.0 or less.

In other words, this mass ratio is a non-volatile component / a volatile component with respect to the component (slag component) constituting the slag phase of the present invention. In the present invention, as described above, in order to form and maintain a viscous slag phase, supply of a volatile component to a continuous working surface is an important factor. Therefore, optimizing the balance of the non-volatile component / volatile component is effective in ensuring and enhancing the effects of the present invention. When the mass ratio is less than 0.1, there are relatively few CaO components that are stable in a reducing atmosphere, so the chemical components of the phase concentrated on the operating surface are mainly volatile oxides, Low viscosity and slag phase cannot exist stably at high temperature. For this reason, it becomes difficult to form a slag coating layer having a high coverage on the operating surface, resulting in an inferior adhesion suppressing effect of Al ₂ O ₃ inclusions. On the other hand, when the mass ratio exceeds 3.0, the CaO component that is stable in the reducing atmosphere is relatively increased, but the concentrated slag phase becomes a low-viscosity slag coating layer, so Since the slag phase which flows down easily increases, it becomes difficult to form a continuous slag coating layer over a long time. Thus resulting in poor adhesion inhibiting effect of Al ₂ O ₃ inclusions.

In order to continuously and effectively form a dense and viscous slag phase or a semi-molten slag coating layer by continuously supplying B ₂ O ₃ and R ₂ O to the working surface of the refractory, it is volatile. B ₂ O ₃ and R ₂ O components as components are preferably dispersed in a refractory matrix. When these volatile components are contained in the matrix, volatilization of the oxide, which is a volatile component, is facilitated, and component movement in the tissue is likely to occur.

  In the present invention, the matrix is a carbon mainly composed of carbon as a binder in the refractory structure, a structure mainly composed of a refractory material having a particle diameter of approximately 0.21 mm or less, and the above-mentioned regardless of the particle diameter. When a volatile component, CaO, or the like is fused or integrated or aggregated (hereinafter simply referred to as “fused or otherwise”), it is a tissue portion that includes the fused or otherwise tissue. It refers to a refractory structure portion existing between refractory aggregates having a particle diameter exceeding 0.21 mm (hereinafter simply referred to as “coarse grains”).

  The state dispersed in the matrix means that it exists with almost the same probability regardless of the location in the matrix (any position), that is, exists in the coarse particles themselves in a compound or mechanically constrained state. Rather, it refers to a state in which the refractory structure excluding coarse grains is present almost uniformly (the difference in content expressed in percentage is approximately within 30%).

  In order to make the refractory structure in a reducing atmosphere, the refractory must contain free carbon. Here, free carbon, whether it is amorphous or crystalline, excluding those that exist as compounds with components other than carbon, impurities and non-compounds are mixed in particles and continuous structures. Regardless of whether or not it exists, it means what exists as a simple carbon. Specifically, it refers to a binder derived from resin, pitch or the like, graphite, carbon black and the like.

Unlike the refractory containing a large amount of CaO mainly composed of high thermal expansion periclase, zirconate or the like, the refractory of the present invention is mainly composed of Al ₂ O ₃ having relatively low expansion. . For this reason, in order to obtain the thermal shock resistance, the thermal shock resistance can be ensured with the same amount of graphite as the Al ₂ O ₃ -graphitic refractory for the main body portion of a general continuous casting nozzle. On the other hand, especially when a refractory layer mainly composed of CaO is disposed on the working surface on the inner hole side in order to add a function of preventing inclusion of inclusions such as Al ₂ O ₃ , the refractory An attempt to increase the thermal shock resistance with the graphite contained in itself requires a large amount of graphite and is not realistic due to the adverse effects such as the deterioration of corrosion resistance and wear resistance. In the refractory of the present invention, compared to such a system, the main composition of the refractory is Al ₂ O ₃ having a lower thermal expansion than CaO, so the amount of graphite can be made relatively low. it can.

  That is, the refractory of the present invention contains 8.0% by mass to 34.5% by mass of free carbon. This free carbon refers to the sum of carbon as aggregate particles and carbon as a binder.

  Carbon as aggregate particles is mainly graphite aggregate, which is added as a filler between carbonaceous connective tissues to increase structure strength, heat conductivity, and coefficient of thermal expansion. The thermal shock resistance can be improved by the action of lowering. In addition, the presence of carbonaceous aggregate particles (carbon as a binder can also be regarded as a part of this) between oxides, etc., has the effect of suppressing oxide sintering and low melting reaction. Yes, stabilization of casting quality can be expected. It is also possible to use carbon black in part with graphite.

  The refractory of the present invention can also be applied only to the inner hole surface of the continuous casting nozzle, and the amount of carbon as aggregate particles (graphite aggregate, etc.) in that case is preferably 7% by mass or more. The refractory of the present invention can also be applied to the main body of a continuous casting nozzle. In this case, the amount of carbon as aggregate particles is more than 18.0% by mass and less than 33.5% by mass. preferable. If it is less than 18.0% by mass, for example, it may be difficult to ensure sufficient resistance to thermal shock when the molten steel is received from a low preheating temperature of about 1000 ° C., for example. If it exceeds 33.5% by mass, it will be easily damaged by the wear of the molten steel flow, the service life of the continuous casting nozzle will be shortened, and local wear due to molten steel drift will be likely to occur.

  Carbon as a binder bears the strength of the refractory itself, maintains its form as a structure, and mainly imparts fracture resistance to thermal shock. The carbon as the binder is preferably obtained mainly from a resin, pitch, tar, or the like that has a large amount of fixed carbon and forms a carbon bond at a high temperature (in a non-oxidizing atmosphere of about 1000 ° C. or higher). The carbon as the binder is preferably 1.0% by mass or more. If it is less than 1.0% by mass, it is difficult to obtain sufficient strength to maintain a structure in which aggregates are bonded with carbon. Moreover, when it is preferable to increase the initial strength when the thickness of the refractory of the present invention is relatively small (for example, about 10 mm or less), 2.0% by mass or more is more preferable. The upper limit is preferably 5.0% by mass or less. If the amount exceeds 5.0% by mass, the structure strength of carbon bonds is sufficient, but the thermal shock resistance decreases and the yield decreases in the manufacture of products (nozzles for continuous casting using the refractory of the present invention). It is not preferable because it is easy to do. The amount of carbon as the binding material may be determined by changing the carbon content in the above range in accordance with individual operations, manufacturing conditions, and the like.

  In this invention, the state of the specific slag coating layer by the rotating test method in molten steel is used as a reference for evaluating the effect of the present invention. It is not practical to directly measure and quantify the state of the slag coating layer in operation.

Therefore, in the present invention, a rotating test method in molten steel was adopted as a verification method in the laboratory for estimating the state of the slag coating layer in operation. Then, a slag coating layer having a coverage of 50% or more and a thickness of 0.1 mm or more is formed on the surface of the refractory used as a sample for this test (assuming that it was in a semi-molten state in the hot state). It was confirmed that the effect of preventing adhesion of inclusions such as Al ₂ O _{3 in} operation can be obtained.

  Next, the rotating test method in molten steel will be described.

  FIG. 1 shows a state in which a holder 2 holding a target sample (hereinafter referred to as “sample”) 1 processed into a predetermined shape at the bottom is immersed in molten steel 3 in a crucible 4. Four specimens 1 are installed in a rectangular parallelepiped, and are fixed to four surfaces of the lower part of the quadrangular prism holder 2, respectively. This sample 1 is inserted through a mortar into a recess provided in a square column holder 2 and can be removed by pulling it out after the test. The upper part of the holder 2 is connected to a rotating shaft (not shown) and is rotatably held with the longitudinal axis as the rotating shaft. Further, the holder 2 has a square shape with a side of 40 mm in the horizontal section with respect to the longitudinal axis, the length in the longitudinal direction is 160 mm, and is made of a zirconia-carbon refractory. The sample 1 has an exposed portion from the holder 2 of 20 mm in length, 20 mm in width, and 25 mm in length. Further, the lower end surface 1 a of the sample 1 is attached at a position 10 mm above the lower end surface 2 a of the holder 2.

  The crucible 4 is made of a cylindrical refractory having an inner diameter of 130 mm and a depth of 190 mm. The molten steel 3 is stored in the crucible 4, and the crucible 4 is built in the high frequency induction furnace 5, and the molten state and temperature of the molten steel 3 can be controlled. The immersion depth of the holder 2 in the molten steel 3 is 50 mm or more. Although not shown, the upper surface can be covered.

  In the rotating test in molten steel, the sample 1 was preheated by holding the sample 1 for 5 minutes immediately above the molten steel 3, and then the sample 1 was immersed in the low-carbon aluminum killed steel as the molten steel 3 by 50 to 100 mm from the surface of the molten steel. The outermost peripheral surface is rotated at an average peripheral speed of 1 m / sec. During the test, the oxygen concentration is maintained in the range of 50 ppm or less by adding aluminum to the molten steel, and the temperature is maintained in the range of 1550 to 1570 ° C. After 3 hours, the sample 1 is pulled up and the sample 2 is cooled together with the holder 2 in a non-oxidizing atmosphere so as not to be oxidized, and then the size of the sample 1 is measured.

  As shown in FIG. 2, the adhesion or erosion rate is measured by removing the sample 1 after the test from the holder and removing the sample 1 from the holder in a horizontal plane (surface in the circumferential direction) perpendicular to the rotation axis. Cut with. On the cut surface, six lengths are measured and averaged at a pitch of 3 mm from the side end surface 1b toward the rotation axis. The sample before the rotating test in molten steel is also measured and averaged at the same position. The average value (μm) after the rotating test in molten steel is subtracted from the average value (μm) before the rotating test in molten steel, and the adhesion or erosion rate (μm / min) is calculated by dividing the value by the test time of 180 minutes. To do.

  The adhesion or melting loss rate (μm / min) in the rotating test in molten steel was evaluated in four stages. That is, the amount of erosion and adhesion is (1) ± 10 μm / min or less, (2) ± 15 μm / min or less, (3) ± 30 μm / min or less, (4) exceeds ± 30 μm / min Classified into things. As a result of performing tests in actual operation by applying these materials with different amounts of erosion and adhesion, it was found that there are acceptable steel types at ± 30 μm / min or less. Therefore, it was determined that 30 μm / min or less was a usable level. . Here, “+” indicates adhesion, and “−” indicates melting damage.

  As conditions for satisfying the melting loss / adhesion speed of ± 30 μm / min or less, the thickness of the slag coating layer on the surface of the sample after the rotation test in molten steel is 0.1 mm or more, and the generated slag coating layer It was found by the rotating test method in molten steel that the coverage ratio of the sample on the molten steel contact surface (percentage of the area covered with the slag phase with respect to the molten steel contact area of the sample) must be 50% or more. .

  The thickness and coverage of the slag coating layer (which can be regarded as a slag phase in a hot state) generated on the sample surface after the test are measured as follows.

  The specimen after the test having the above-mentioned cut surface is impregnated and polymerized with a resin monomer and then polished, and the thickness of the slag phase generated on the refractory surface is measured with a microscope. In the sample 1 after completion of the test shown in FIG. 2, a line is drawn at a pitch of 3 mm from the side end surface 1b in the direction of the rotation axis in the region in contact with the molten steel (see FIG. 2B), and the rotation direction (circumferential direction 2 (b), the surface direction located in the upper part) and the opposite side (the opposite side of the circumferential direction of travel, the surface direction located in the lower part in FIG. 2 (b)). Measure the thickness of the slag coating layer near the intersection with the refractory working surface. For details of the measurement method, the thickness of the slag coating layer is measured from the boundary of the healthy part (when alumina aggregate reacted with the slag phase is included, from the part where the aggregate shape is known) to the surface layer of the slag coating layer. Let the thickness be the average value of the measured values, respectively, as the thickness of the slag coating layer.

The coverage C is measured and calculated as follows. In the region in contact with the molten steel, the region up to 6 mm on the rotational direction side facing the rotational axis from the side end surface 1b and the working surface on the opposite side (region from the right end to the second line on the right in FIG. 2B) From the ratio of the refractory working surface length (L0) (R-shaped region from the right end to the second line on the right in FIG. 2 (b)) and the length of the slag coating layer (L1), The rate C (%) is calculated.
C (%) = L1 / L0 × 100 Formula 1

  Furthermore, the present inventors have found that the continuous formation effect of the slag coating layer can be obtained more stably when the air permeability of the refractory is in a specific range.

  Specifically, in order for volatile oxide components to move stably and efficiently at high temperatures, it must have better conditions for volatile oxides to pass through, that is, within the refractory structure. The presence of a space (a pore) as a path for communicating with each other is more preferable.

  The present inventors have found that the air permeability K at normal temperature of the refractory after firing in a non-oxidizing atmosphere at 1000 ° C. is optimal as this index.

This air permeability K can be expressed by Equation 2.
K = (Q × L) / (S × (P1−P2)) Equation 2
here,
Q: Volume of air that passed through the sample per unit time (cm ³ )
L: Sample thickness (cm)
S: Cross-sectional area of the sample (cm ² )
P1: Air pressure at the time of sample inflow (cmH ₂ O)
P2: Air pressure at the time of sample outflow (cmH ₂ O)

In the present invention, the air permeability K at room temperature of the refractory after firing in a non-oxidizing atmosphere at 1000 ° C. is 0.4 × 10 ⁻³ to 4.0 × 10 ⁻³ cm ² / (cmH ₂ O · sec). When the air permeability is lower than 0.4 × 10 ⁻³ cm ² / (cmH ₂ O · sec), the volatile component, which is a gasified slag component, does not easily reach the working surface and is dense and viscous slag clothing The continuous or prolonged formation of the layer may be insufficient. When the air permeability is greater than 4.0 × 10 ⁻³ cm ² / (cmH ₂ O · sec), volatile components disappear in a short time after the start of casting, and a continuous slag coating layer is formed during casting. Failure to do so may result in adhesion of Al ₂ O ₃ (such as when the molten steel flow rate is high).

  The air permeability K is a value obtained by the above equation 2 by measuring air passing through a refractory having a diameter of about 30 mm to about 60 mm × thickness of about 5 mm to about 30 mm. The sample may be cut out from the refractory already in the product state, or may be manufactured in advance for the measurement.

The means for obtaining the above-mentioned specific air permeability need not be particularly limited. Examples of this means include the following method.
(1) The packing density is reduced during the molding of the refractory.
(2) Adjust the particle size of the refractory aggregate other than the volatile components and the composition ratio thereof (avoid the close packed structure).
(3) A flammable liquid or a fine solid is blended in the molding earth of the refractory before molding, and a minute space is formed after firing.
(4) Adjust the pressure during molding.

In the present invention, the content of Al ₂ O ₃ in the refractory is set to 50% by mass or more. A part of the molten slag phase generated at the working interface of the molten steel / refractory reacts with the refractory aggregate in the structure, and properties such as viscosity and fire resistance of the slag coating layer are determined. Al ₂ O ₃ aggregate is most preferred as the refractory aggregate for stably maintaining a smooth, dense, and viscous slag coating layer that is hardly flowed at the molten steel flow rate.

Al ₂ O ₃ is a neutral-based oxide, it is possible to obtain a viscous viscous by moderate reactivity with the molten slag phase, excellent corrosion resistance against molten steel, and Al ₂ O ₃ deposited measures material The thermal expansion is smaller than that of an aggregate mainly composed of ZrO ₂ , MgO or the like as conventionally used, and a refractory mainly composed of this has excellent thermal shock resistance.

When the Al ₂ O ₃ content is less than 50% by mass, the slag coating layer formed by the reaction between the oxide concentrated at the working interface and the aggregate lacks fire resistance, so the molten steel flow velocity at the refractory working interface It becomes difficult to maintain a dense slag coating layer.

The structure of the remainder of the components of a refractory constituent of the invention described above, an oxide other than the, for example SiO 2, _MgO, spinel, in combination, such as ZrO ₂ is possible. However, ZrO ₂ increases viscosity by mixing into the molten slag phase. For this reason, in the case where the molten steel temperature is higher than usual, the molten steel flow velocity is larger than usual, etc., it contributes to suppressing the loss of the slag coating layer and prevents the adhesion of Al ₂ O ₃ inclusions, etc. Can be maintained. However, under normal conditions such as molten steel temperature and molten steel flow velocity, adhesion of inclusions such as Al ₂ O ₃ may easily occur due to excessive increase in the viscosity of the slag coating layer. For this reason, it is usually preferable to limit the content of ZrO ₂ to 6% by mass or less in the entire refractory.

Moreover, it is also possible to select from one or more selected from the group of carbides such as SiC, TiC, and B ₄ C, nitrides such as Si ₃ N ₄ and BN, and metals such as Al, Si, and Ti.

As the mineral phase of Al ₂ O ₃ in the refractory composition, a thermally stable corundum phase is preferable. If it is Al ₂ O ₃ as a corundum, it will not dissolve at an early stage with respect to the slag phase, the function as a structure can be maintained, and an appropriate nozzle service life can be maintained. In addition, since it can have the same thermal expansion characteristics as Al ₂ O ₃ -graphite-based material, which is the material for the main body of general continuous casting nozzles, it can be handled on the surface of thermal shock resistance and erosion resistance. There is also an advantage that is easy.

The Al ₂ O ₃ mainly composed of corundum preferably has an Al ₂ O ₃ purity of about 95 mass or more. Examples of the Al ₂ O ₃ mainly composed of corundum include an artificial material obtained by an electrofusion method, a sintering method, and the like, and a heat-treated material that has been naturally produced. When a naturally occurring raw material is used as a starting raw material, TiO ₂ , SiO ₂ or the like is mixed as a mineral phase such as a compound. The influence of the impurities in the raw material particles on the effect of the present invention is small.

In addition, in the region of the present invention, in particular, in the region of the present invention, the smaller the particle size and the smaller the total amount of CaO and B ₂ O ₃ and R ₂ O, the impurities are slag phases at the interface of Al ₂ O ₃ particles mainly composed of corundum. It may contribute to the improvement of the adhesiveness. Therefore, SiO ₂ as an impurity derived from Al ₂ O ₃ mainly composed of these corundums in a region having a particle size of about 0.21 mm or less, that is, in the region constituting the matrix, is SiO for achieving the above-described function of the present invention. _It can also be used as part or all of the _two sources.

In general, for the purpose of improving thermal shock resistance, it is generally performed to contain molten SiO ₂ in a refractory material in a coarse particle size (about 0.5 mm to about 0.1 mm). Also in the present invention, such fused SiO ₂ can be used in combination.

Compared to B ₂ O ₃ and R ₂ O components, the SiO ₂ component has low molten steel temperature level and low volatility in a reducing atmosphere, but by coexisting, it has the ability to promote film formation at the molten steel / refractory interface. is there. However, when the silica component coexists with the CaO component in the structure, the silica component is stabilized as a slag phase and hardly volatilizes in the structure. Therefore, the silica component is preferably used with a particle size of 0.21 mm or more for the purpose of suppressing low melting.

The refractory of the present invention described above is arranged on a part or all of the surface in contact with the molten steel in the continuous casting nozzle, thereby preventing the inclusion of inclusions such as Al ₂ O ₃ or clogging in the nozzle. Can do. That is, the part with much adhesion may be mainly arranged according to the condition of individual operation and the adhesion situation of inclusions such as Al ₂ O ₃ . In addition, the thickness of the refractory according to the present invention is determined in consideration of the degree of erosion of the refractory, the degree of adhesion of inclusions such as Al ₂ O ₃ and the set lifetime. Just decide.

The nozzle for continuous casting in which the layer made of the refractory of the present invention is arranged on the inner hole side, the refractory of the present invention is almost the same as the Al ₂ O ₃ -graphitic layer of the main body of the continuous casting nozzle. Has thermal expansion characteristics. As a result, the layer made of the refractory of the present invention (especially the inner hole side layer of the continuous casting nozzle) and the other refractory layer adjacent to this layer (particularly from the axis of the continuous casting nozzle to the outer peripheral side in the radial direction). It has a unique structure such as a layer for the purpose of stress relaxation, such as a space, a shrinkable mortar layer, etc. between the Al ₂ O ₃ -graphite layer forming a certain body) There is no need. That is, it can be set as the integral structure where the layer which consists of the refractory material of this invention, and the other refractory layer adjacent to this is directly joined.

  Here, “direct bonding” means that the contact surface between the refractory layer of the present invention and another refractory layer adjacent to this layer is a third layer other than these refractories, such as an adhesive such as mortar. , Refers to a state of being in close contact without a space or the like. And this close_contact | adherence state includes the case where the structure | tissue of two layers is intertwined with an unevenness | corrugation, and the case where it is only in contact without being intertwined with an unevenness | corrugation.

Specific structures include the following types.
(1) Radial direction starting from the refractory layer of the present invention as a part or all of the inner hole side and bottom layer of the continuous casting nozzle and the other refractory layer starting from the axial center of the molten steel flow direction (2) A layer made of the refractory material of the present invention is disposed on a part or all of the inner surface layer of the discharge hole of the continuous casting nozzle, and the other refractory layer is discharged. The type of the outer peripheral surface (including the bottom) of the molten steel immersion portion of the continuous casting nozzle with a layer made of the refractory according to the present invention. A type in which other refractory layers are arranged on the inner side (in the direction of the inner hole of the nozzle) in some or all layers

  In the manufacturing method of the continuous casting nozzle having such an integral structure, the same manufacturing method as the general manufacturing method of the continuous casting nozzle can be adopted. In other words, this is a method in which a soil is formed by CIP (Cold Isostatic Press), and then dried, fired, mechanically processed, and the like. This is because the refractory of the present invention contains approximately the same level of graphite as the graphite-containing refractory applied to the above-described general production method.

  Therefore, in the method for producing a continuous casting nozzle in which the refractory of the present invention is disposed on a part or all of the surface in contact with the molten steel, part or all of the layer made of the refractory of the present invention in the continuous casting nozzle. On the other hand, it is possible to simultaneously fill the mold with the soil to be used for the molding and the soil to be used for the molding of the layer composed of other than the refractory adjacent to the layer, and simultaneously pressurize by CIP molding. As a result, it is possible to obtain an integrated structure in which the structure is intertwined with the projections and depressions in the vicinity of the contact portion between the two layers, and there is no apparent seam or a layer that separates the two.

The refractory material of the present invention and the continuous casting nozzle in which the refractory material is arranged prevent adhesion of inclusions such as Al ₂ O ₃ or clogging in the nozzle on the surface of the continuous casting nozzle in contact with the molten steel in the continuous casting operation. can do.

In addition, the function of preventing the inclusion of inclusions such as Al ₂ O ₃ or the clogging in the nozzle is compared with the conventional refractories and continuous casting nozzles, which are mainly composed of Al ₂ O ₃ -graphite or calcium zirconate. Can be maintained continuously for a long time.

Further, the refractory of the present invention and the continuous casting nozzle having the refractory disposed thereon are free from cracks caused by the high expansion inherent in the CaO-containing refractory of the prior art for the purpose of preventing adhesion of Al ₂ O ₃ inclusions and the like. Problems such as occurrence can be solved. This is because the refractory of the present invention has substantially the same thermal expansibility and graphite amount as Al ₂ O ₃ -graphitic refractories for main bodies and the like that are excellent in thermal shock resistance, and the glass phase or in the refractory structure. This is because a slag phase is generated, and the glass phase or slag phase also has a function of relaxing the generated stress inside the refractory while hot.

Furthermore, the refractory according to the present invention and the continuous casting nozzle provided with the refractory can be manufactured at a lower cost and more easily than conventional CaO-containing refractories. This is because the refractory of the present invention has a graphite amount excellent in thermal expansibility and stress relaxation ability similar to Al ₂ O ₃ -graphitic refractories for main bodies and the like having excellent thermal shock resistance. For this reason, even if the structure is in direct contact with other refractories having excellent thermal shock resistance, such as those for the main body, mutual stress (or distortion) that causes destruction is not generated.

  Further, by adopting an integral structure with the refractory material having excellent thermal shock resistance such as the main body, the stability of the nozzle during operation is improved as compared with the so-called divided structure product.

  Since such an integral structure can be used, the same method as that of an ordinary integral structure product can be adopted in the manufacture of the nozzle. According to this normal manufacturing method, the manufacturing process is simplified and the raw material cost is reduced as compared with a manufacturing method in which each part is manufactured separately in a so-called divided structure and then each part is joined with mortar or the like. Due to its superiority and the like, it can be manufactured at low cost. The manufacturing process can also be shortened.

  Further, in the conventional CaO-containing refractory, particularly in the case of a large amount of CaO content, destruction of the refractory and the nozzle due to CaO hydration reaction (digestion) is also a serious problem. Since the refractory can use the CaO source as a form having low digestibility (silicate, aluminate, etc.), it is possible to prevent destruction of the refractory due to the hydration reaction of CaO and the nozzle. This facilitates handling, storage, etc. of the refractory of the present invention and the continuous casting nozzle in which the refractory is disposed, and eliminates the need for digestion prevention measures.

It is explanatory drawing which shows the method of a rotating test in molten steel. It is an image figure of the cross section of the sample after a rotation test in molten steel, (a) shows the case of adhesion, (b) shows the case of melting damage. It is sectional drawing which shows an example of the nozzle for continuous casting of this invention (when applying the refractory of this invention only to an inner-hole surface). It is sectional drawing which shows an example of the nozzle for continuous casting of this invention (when applying the refractory of this invention to all the contact surfaces with molten steel). It is sectional drawing which shows the structure | tissue near the working surface of the sample after an experiment by the rotating test method in molten steel about the refractory of this invention, (A) is a refractory of a prior art (Comparative example 1 of an Example), (B ) Is a refractory according to the present invention (Example 17). It is a figure which shows the component (change of the component ratio accompanying the distance of a refractory internal direction from an operation surface) inside the refractory material of this invention of FIG. 5 (B). It is a cross-sectional photograph after use of the nozzle for continuous casting of Example I, (A) is the nozzle for continuous casting (immersion nozzle) of the prior art (refractory material of Comparative Example 1), and (B) is the present invention (Example). No. 17 refractory) nozzle for continuous casting (immersion nozzle).

  The manufacturing method of the refractory material of this invention is described.

As a raw material for B ₂ O _3, a raw material for boric acid, CaO, and R ₂ O is preferably a high purity reagent such as an alkaline earth oxide or an alkali metal oxide. However, compounds of B ₂ O ₃ , CaO, R ₂ O can also be used, such as boric acid powder, borosilicate slag, industrial slag powder, frit powder, synthetic slag powder, Portland cement, Al ₂ O ₃ cement, boron compound, borax powder, dolomite powder, various carbonates and the like can also be used. Moreover, the alkali silicate etc. which consist of a slag-forming base material component and a slag-forming auxiliary component can also be used. However, for uniform slag formation, it is preferable to use slag frit fine powder whose components have been adjusted and melt-pulverized in advance.

In addition, in the refractory structure, CaO and any one or both of B ₂ O ₃ and R ₂ O are 1.0% by mass or more and 15.0% by mass or less, and (CaO) / (B ₂ O ₃ + R Adjustment for satisfying the condition of the mass ratio of ₂ O) of 0.1 or more and 3.0 or less can be performed by adjusting the raw materials while comparing with the result of the rotating test in molten steel.

  In addition, these slagging components can enhance the effect by being evenly dispersed in the refractory structure. The matrix preferably has a particle size region of about 0.21 mm or less.

  In order to disperse the slag components more evenly in the matrix between the refractory aggregates, and to form a slag phase more quickly, the addition of these slag components is about 1 of the aggregate size. / 10 or less (The aggregate particle size used for refractories for continuous casting nozzles such as immersion nozzles and long nozzles is generally about 1 mm from the viewpoint of homogeneity of the structure, thermal shock resistance, and corrosion resistance. In the present invention, it is preferable to add a powder containing 90.0% by mass or more of particles having a size of about 0.1 mm or less in a similar size.

  As the carbon as the aggregate particle, it is preferable to use a graphite aggregate in which a hexagonal net surface crystal such as scale-like graphite, earth-like graphite particle, and artificial graphite is developed. In particular, the use of naturally occurring scaly graphite is most preferable in terms of thermal shock resistance. The carbon content in the graphite aggregate is preferably 90.0% by mass or more (including 100% by mass excluding inevitable impurities). The reason is that the purity is less than 90.0% by mass, resulting in a high elastic modulus of the refractory structure due to a sintering reaction between impurities or impurities and other raw material particles, etc., resulting in a decrease in thermal shock resistance. It is because there is a possibility of doing.

  By adding these graphite aggregates as fillers between carbonaceous connective structures, the thermal shock resistance can be improved by the action of increasing the strength of the structure, increasing the thermal conductivity, and decreasing the thermal expansion coefficient. In addition, since the carbon including the binder is uniformly dispersed between the oxides and the like, there is an effect of suppressing the sintering of the oxide and the low melting reaction, and the quality during the casting can be stabilized. In order to make it exist in the state disperse | distributed uniformly in this way, it is preferable to use the graphite aggregate whose particle size is 2 mm or less. However, when a graphite aggregate whose particle size is smaller than 0.1 mm is mainly used, the homogeneity of the structure is excellent, but the thermal shock resistance is lowered. On the other hand, when the particle size is larger than 2 mm, the thermal shock resistance is excellent, but the components are likely to be unevenly distributed in the structure. Therefore, the particle size of the graphite aggregate is preferably 0.1 mm or more and 2 mm or less. Various carbon blacks can be used in combination with graphite as carbon as aggregate particles.

The refractory Al ₂ O ₃ of the present invention is preferably 70.0% by mass or more, more preferably 90.0% by mass or more, with a particle size of more than 0.2 mm based on the total aggregate. It is. The reason is that the portion forming the slag phase is preferably dispersed only in the refractory matrix with only those components as much as possible, and other skeletons that maintain the structure and strength of other refractories. This is because the particles are dissolved in the slag phase or react with the slag component to form a low-melt material, thereby reducing as much as possible the factors that cause tissue deterioration. In addition, a part of Al ₂ O ₃ aggregate is about 10.0% by mass or less with respect to the refractory aggregate which hardly reacts with raw materials of slagging components such as SiC, ZrO ₂ and zirconia compounds and the aggregate. It is possible to substitute by range. However, since the ZrO ₂ component may excessively increase the slag viscosity and promote the adhesion of Al ₂ O ₃ inclusions as described above, it is preferably limited to 6% by mass or less in the entire refractory.

Here, in addition to the aforementioned Al ₂ O ₃ , the remainder other than the above-described slagging component and carbon may contain inevitable components such as those derived from the raw materials or mixed during production. Among these unavoidable components, impurities such as Fe ₂ O ₃ and TiO ₂ are preferably suppressed to about 1.0% by mass or less. This is because there is a possibility of partially reducing the viscosity of the semi-molten slag phase.

  These powders are mixed to make a uniform powder mixture. Then, a binder such as a phenolic resin, pitch, or tar as a carbonaceous raw material that bears the connective structure is appropriately selected and added to the powder mixture and uniformly kneaded to obtain a molding clay. The raw material used as the binder may be either powder or liquid, but it is important to adjust the plasticity of the earth according to the characteristics of the earth suitable for molding.

  Next, an example is described about the manufacturing method of the nozzle for continuous casting which installed the refractory material obtained from the said refractory material of this invention in the inner-hole side layer.

  Separately from the refractory clay of the present invention, an outer layer, that is, a clay for the main body of the nozzle for continuous casting is prepared (a general manufacturing method may be used). Next, a plurality of spaces partitioned to a predetermined size are provided in the molding mold to form the inner hole side layer and the outer peripheral side layer, and each of the spaces in the molding mold is made with a dedicated soil. And the adjacent soil is brought into direct contact with each other, for example, by removing the partition of the space.

  These directly contacted soils are simultaneously pressed by a CIP device to be integrally formed. The obtained molded body is heat-treated at 600 ° C. or higher and 1300 ° C. or lower in a non-oxidizing atmosphere or in an oxidizing atmosphere with the surface subjected to an antioxidant treatment. Prior to the heat treatment step, an independent heat treatment step may be included at a temperature lower than the above temperature for the purpose of removing volatile components and curing the resin. Finally, processing or the like is appropriately performed in the same manner as in the manufacture of a normal continuous casting nozzle.

  The basic operation / working method of each process described above, the apparatus to be used, and the like may be the same as those of a general continuous casting nozzle manufacturing method.

  As described above, the refractory according to the present invention is arranged as an inner hole side layer only on the inner hole surface of the continuous casting nozzle as described above. However, it can be used not only for the inner hole side layer but also for other parts such as the bottom part, the discharge hole, the outer surface and other parts in contact with the molten steel, the main body part and the entire continuous casting nozzle.

  The manufacturing method of the continuous casting nozzle using the refractory material of the present invention is not limited to an integrated manufacturing method with other materials as the inner hole side layer, and (1) manufactured as a cylindrical molded body. A method of attaching the pipe body to the inner hole of the separately manufactured main body part and fixing it with mortar or the like, or (2) forming the nozzle main body part and the inner hole side layer part as a single body with the refractory material of the present invention. The method of doing can be employed.

Next, examples (including experimental examples) of the present invention will be described. In the experiments of the embodiment, the formation of slag coating layer, the adhesion of the inclusions such as Al ₂ O _3, was evaluated by the molten steel of the above-described rotation test method.

<Example A>
Example A is an experimental example in which the effects of CaO, B ₂ O ₃ and R ₂ O were investigated. Table 1 shows the composition of the samples, the components of each sample, and the results.

As shown in Examples 1 to 10, when the CaO component is contained in an amount of 0.5% by mass or more and the total amount of either or both of B ₂ O ₃ and R ₂ O is 0.5% by mass or more, It can be seen that the thickness of the slag coating layer on the sample operating surface is 0.1 mm or more, and the coverage of the slag coating layer is 50% or more. In addition, with respect to the adhesion rate to the sample or the erosion rate of the sample, all of the examples have an adhesion rate of +30 μm / min or less, and satisfy the standard of ± 30 μm / min or less (melting or adhesion). I was able to.

In addition, Example 3, Example 4, and Example 5 are examples in which the R species of R ₂ O was changed to Na, K, and Li. All of these examples can satisfy the thickness of the slag coating layer within the standard, the coverage, and the erosion or deposition rate.

In contrast to these examples, Comparative Examples 1 to 5 have examples in which only the thickness of the slag coating layer exceeds 0.1 mm, but none of the comparative examples satisfy the coverage and the erosion or adhesion rate. That is, in these comparative examples, the slag coating layer for suppressing the adhesion of inclusions such as Al ₂ O ₃ is not sufficiently formed.

<Example B>
Example B is an experimental example in which the effect of substituting a part of the Al ₂ O ₃ aggregate, which is the main component of the refractory, with MgO based on the sample of Example 6 described above was investigated. Table 2 shows the composition of the samples, the components of each sample, and the results.

In Example 11, Example 12, and Example 6 in which the Al ₂ O ₃ content is 50% by mass or more, the slag coating layer thickness, the coating rate, and the erosion or deposition rate within the standard for all the samples used Can meet. However, in Comparative Example 6 in which the Al ₂ O ₃ content is 47.4% by mass, the thickness of the slag coating layer, the coating rate, and the melting loss or the deposition rate are not satisfied.

<Example C>
Example C is an experimental example in which the effect of changing the carbon content was investigated based on the sample of Example 6 described above. Table 3 shows the composition of the samples, the components of each sample, and the results.

In Example 13, Example 6, and Example 14 in which the carbon content is 8.0% by mass or more, the thickness, coverage, and erosion or deposition rate of the slag coating layer within the standard for all samples are included. Can meet. However, in Comparative Example 7 where the carbon content is 7.3% by mass, which is less than 8% by mass, the thickness of the slag coating layer slightly does not satisfy the standard, and the coverage and the erosion or deposition rate Does not meet. This is considered to be because the reducing atmosphere for volatilizing B ₂ O ₃ and R ₂ O was insufficient. Further, in Comparative Example 8 in which the carbon content exceeded 34.5% by mass, only the thickness of the slag coating layer satisfied the standard, but the coverage standard could not be satisfied, and the rate of erosion As a result, the standard of the melting rate could not be satisfied. This is presumably because the viscous slag coating layer was not sufficiently formed and the portion exposed to the molten steel on the surface of the refractory increased, and the melting phenomenon of carbon into the molten steel occurred.

  In addition, although carbon content of Example 13 is 8.2 mass%, it estimates from the relative relationship with the result of the comparative example 7 which did not reach a reference | standard slightly, and carbon content is 8.0 mass. It can be determined that the standard can be satisfied when the percentage is greater than or equal to%. (In such a carbon content region, since the content of the components constituting the other slag is the same, the thickness of the slag coating layer is considered to change linearly with the carbon content as a variable. It can be estimated that the standard is satisfied when the carbon content is 8.0 mass% or more.)

<Example D>
Example D is an experimental example in which the effect of changing the total amount of CaO, B ₂ O ₃ and R ₂ O was investigated. Table 4 shows the composition of the samples, the components of each sample, and the results.

In this example, based on the sample of Example 6, a range of up to 16% by mass was confirmed for the total amount of CaO, B ₂ O ₃ , and R ₂ O. In any of the examples in which the total amount of CaO, B ₂ O ₃ and R ₂ O is 1.0% by mass or more and 16% by mass, the thickness of the slag coating layer within the standard, the coverage, and the erosion or deposition rate Can meet. Further, in Comparative Example 9 in which the total amount of CaO, B ₂ O ₃ and R ₂ O is 16.0% by mass, the tendency of melting damage, the thickness of the slag coating layer, and the coverage rate are observed, and the coverage rate is observed. Although C is C, a portion close to D was also observed. Such a tendency can be controlled to some extent by adjusting other components (for example, ZrO ₂ ) such as aggregates that react with a slag phase other than Al ₂ O ₃ . However, the total amount of CaO, B ₂ O ₃ and R ₂ O is preferably 15% by mass or less from the viewpoint of stably maintaining the slag coating layer in the system mainly composed of Al ₂ O ₃ aggregate. Therefore, the total amount of the refractory according to the present invention is 15% by mass or less.

Here, using the sample after the experiment of Example D, the properties of the slag coating layer of the present invention and the behavior of the volatile components of CaO component, B ₂ O ₃ and R ₂ O in the refractory of the present invention, etc. A specific example will be shown.

FIG. 5 is a cross-sectional view showing the structure from the vicinity of the working surface to the center side of the post-experiment sample by the rotating test method in molten steel, (A) is a refractory of the prior art (Comparative Example 1), and (B) is It is a refractory according to the present invention (Example 17). In FIG. 5 (A), the circled number 1 (hereinafter “rounded number n” is expressed as “circle n”) is a conventional Al ₂ O ₃ -graphitic refractory structure, round Reference numeral 2 denotes a deposit layer on the working surface of the circle 1. In FIG. 5B, circle 3 is the refractory structure of the present invention, circle 4 is a slag coating layer (slag phase in a semi-molten state that is hot and viscous), and circle 5 is a space (no deposit layer). Show).

  It can be seen that the round 4 slag coating layer is uneven on the contact surface with the molten steel (round 5), and penetrates into voids such as pores of the refractory at the interface with the refractory. This indicates that the slag coating layer was a hot, viscous, semi-molten slag phase. (The lower the viscosity, the smoother the contact surface with the molten steel, and the higher the viscosity, the less likely it will penetrate into the pores of the refractory at the interface with the refractory. Is not such a tendency.)

  Moreover, FIG. 6 is a figure which shows the component of the inside of a refractory of this invention of FIG. 5 (B), and the component of a working surface (change of the component ratio accompanying the distance of a refractory inside direction from a working surface). Positions A, B, and C (open circles) in FIG. 5B correspond to A, B, and C in FIG.

  D in FIG. 6 indicates a component at the center position of the sample in FIG. (D in FIG. 6 is not shown in FIG. 5B because it is below the range of microscopic photography displayed in FIG. 5B.)

  The component values of A, B, C, and D are all measured for a part of the matrix. That is, since the component values at these positions are not a ratio with respect to the entire refractory, the meaning as an absolute value is scarce, but a relative difference at each position can be confirmed.

From FIG. 6, except for the inside of the slag coating layer, the amount of the CaO component is almost the same from the working surface of the refractory to the inside, and the amount of the volatile component of B ₂ O ₃ and R ₂ O is that of the refractory. It can be seen that the closer to the operating surface side, the more gradually increases, especially in the vicinity of the operating surface.

Moreover, in the slag coating layer, the amount of volatile components of B ₂ O ₃ and R ₂ O is further increased, while CaO is decreased.

The relative increase of the volatile components of B ₂ O ₃ and R ₂ O in the slag coating layer and on the working surface side is caused by volatilization of these components from the refractory structure and the working surface side or slag coating layer. Indicates that it has moved in. Moreover, such a change in the amount of CaO indicates that CaO reacted with molten steel-derived components (Al ₂ O ₃ , S, etc.) in the slag coating layer and flowed into the molten steel.

<Example E>
Example E is an experimental example in which the effect of changing the mass ratio CaO / (B ₂ O ₃ + R ₂ O) was investigated. Table 5 shows the composition of the samples, the components of each sample, and the results.

In this example, based on the sample of Example 17, a range from a minimum of 0.1 to a maximum of 3.2 was confirmed per mass ratio CaO / (B ₂ O ₃ + R ₂ O). As a result, all the examples can satisfy the thickness of the slag coating layer within the standard, the coverage, and the erosion or deposition rate. However, with the change in the mass ratio in Example 23 to Comparative Example 10 in which there are many CaO components, there is a tendency for the melting loss tendency and the thickness and coverage of the slag coating layer to decrease. In Comparative Example 10, although the coverage was C, a portion close to D was also observed. From the viewpoint of stably maintaining the slag coating layer in a system mainly composed of Al ₂ O ₃ aggregate, the mass ratio CaO / (B ₂ O ₃ + R ₂ O) maximum is preferably 3.0% by mass or less. In the refractory according to the present invention, the mass ratio is 3.0% by mass or less.

<Example F>
Example F is an experimental example in which the effect of changing the air permeability (value at room temperature after firing in a non-oxidizing atmosphere at 1000 ° C.) was investigated. Table 6 shows the composition of the samples, the components of each sample, and the results.

In this example, based on the sample of Example 6, the air permeability was changed by changing the pressure during molding. The air permeability was measured and calculated by the method described above. Passing air ratio is lowered in Comparative Example 12, the slag coating layer coverage of _{^{4.4 × 10 -3 cm 2 / (}} cmH 2 O · sec), is reduced, is seen a tendency that the deposition rate increases. From the viewpoint of stably maintaining the slag coating layer in a system mainly composed of Al ₂ O ₃ aggregate, the air permeability K is preferably 4.0 × 10 ⁻³ cm ² / (cmH ₂ O · sec) or less.

<Example G>
Example G is an experimental example investigating the effect when the content of the ZrO ₂ component is changed. Table 7 shows the composition of the samples, the components of each sample, and the results.

In this example, based on the sample of Example 17, the ZrO ₂ component content was changed by replacing the ZrO ₂ fine powder aggregate with the Al ₂ O ₃ aggregate. As a result, as the content of the ZrO ₂ component increases, the tendency to adhesion tends to shift from the erosion tendency. Or the deposition rate can be satisfied. However, the adhesion tendency of Example 31 in which the content of the ZrO ₂ component is 6.8% by mass is higher than that in Example 30 in which the content of the ZrO ₂ component is 6.0% by mass. It can be seen that the change in the adhesion thickness with respect to the change (0.8% by mass) is large. From the viewpoint of stably maintaining the slag coating layer in a system mainly composed of Al ₂ O ₃ aggregate, the content of the ZrO ₂ component is preferably 6.0% by mass or less.

<Example H>
Example H is an experimental example investigating the effect of changing the content of the SiO ₂ component. Table 8 shows the composition of the samples, the components of each sample, and the results.

In this example, based on the sample of Example 32, the SiO ₂ component content was changed by replacing the SiO ₂ fine powder aggregate with the Al ₂ O ₃ aggregate. In the range up to 15% by mass of the SiO ₂ component confirmed in this example, any of the examples can satisfy the thickness, coverage, and melting rate or adhesion rate of the slag coating layer within the standard. ing. That is, it can be seen that the effect of the present invention is not affected within the range of the SiO ₂ component content.

<Example I>
Example I is a test example in which the sample refractory of Example 17 was subjected to continuous casting of molten steel in actual operation together with the refractory of Comparative Example 1.

  The refractory material of Example 17 was an immersion nozzle having the structure shown in FIG. That is, the refractory of the present invention was disposed on the entire surface of the immersion nozzle that contacts the molten steel except the powder portion (reference numeral 10 in FIG. 4). The main body refractory (reference numeral 12) is the refractory of Comparative Example 1, and the refractory according to the present invention (reference numeral 10) and the main refractory (reference numeral 12) are manufactured by simultaneous molding. However, it has an integral structure.

  The refractory of Comparative Example 1 was an immersion nozzle having a structure integrated with the main body (reference numeral 12) without the refractory area (reference numeral 10) of the present invention shown in FIG. That is, the refractory material of Comparative Example 1 was disposed on the entire surface of the immersion nozzle that contacts the molten steel except the powder portion.

All the immersion nozzles of Examples and Comparative Examples were used under normal operating conditions such as preheating. The immersion nozzles of the examples and comparative examples were preheated with a gas burner, and then were subjected to a mold size of 350 × 450 mm and a casting speed of 0.5 to 0.8 m / min. It used for the continuous casting of carbon steel.
As a result, the maximum thickness of the deposits such as Al ₂ O ₃ in the comparative example was 22 mm and the deposition rate was 42 μm / min (512 minutes, 10 ch used), whereas in the example used simultaneously with the comparative example. The maximum thickness of deposits such as Al ₂ O ₃ was 1.5 mm, and the deposition rate was 3 μm / min (512 minutes, 10 ch used) (see FIG. 7). Furthermore, damage such as cracks did not occur in the immersion nozzle of the example.

According to this embodiment, the continuous casting nozzle in which the refractory according to the present invention is arranged can realize prevention of adhesion of Al ₂ O ₃ inclusions and the like, and a CaO-containing refractory as proposed in the prior art. Eliminates problems such as the occurrence of cracks due to inherent high expansion, and can be manufactured more inexpensively and easily than conventional CaO-containing refractories. It can be seen that a nozzle having a more stable structure can be obtained.

  In this example, the immersion nozzle having the structure shown in FIG. 4 in which the refractory according to the present invention is arranged on the entire surface of the immersion nozzle that contacts the molten steel except for the powder portion is used. It is also possible to provide an immersion nozzle having a structure shown in FIG.

DESCRIPTION OF SYMBOLS 1 Sample 1a Lower end surface of sample 1b Side end surface of sample 2 Holder 2a Lower end surface of holder 3 Molten steel 4 Crucible 5 High frequency generator 10 Refractory of the present invention 11 Inner hole of nozzle for continuous casting 12 Al ₂ O ₃ − Graphite refractory 13 Zirconia-graphite refractory Round 1 Prior art Al ₂ O ₃ -Graphitic refractory structure Round 2 Deposited layer on the working surface of the circle 1 Round 3 Refractory structure of the present invention Round 4 Slag Coating layer (slag phase in a hot, semi-molten state)
Circle 5 space (indicates no deposit layer)

Claims (6)

The CaO component is 0.5% by mass or more, the total amount of either or both of B ₂ O ₃ and R ₂ O (R is any one of Na, K, and Li) is 0.5% by mass or more, Al ₂ O ₃ 50 mass% or more, free carbon is contained 8.0 mass% or more and 34.5 mass% or less, and the total of CaO, B ₂ O ₃ and R ₂ O is 1.0 mass% or more and 15.0 mass%. or less, the mass ratio _{CaO / (B 2 O 3 +} R 2 O) is in the range of 0.1 to 3.0, 1000 ° C. aeration rate at room temperature after firing under a non-oxidizing atmosphere, When R of the R ₂ O component is Na, the range is 0.4 × 10 ⁻³ to 4.0 × 10 ⁻³ cm ² / (cmH ₂ O · sec), and when R is K, 1.5 In the range of × 10 ⁻³ to 4.0 × 10 ⁻³ cm ² / (cmH ₂ O · sec), when R is Li, 2.2 × 10 ^-3 to 4.0 × ¹⁰ -3 ^cm 2 _/ refractory in the range of _(cmH 2 O · sec). The refractory according to claim 1, wherein the ZrO ₂ content is 6% by mass or less (including zero).   A continuous casting nozzle in which the refractory according to claim 1 or 2 is disposed on a part or all of a surface in contact with molten steel.   An integral structure in which a layer in which the refractory according to claim 1 or 2 is arranged on a part or all of a surface in contact with molten steel is directly joined to a layer adjacent to the layer and made of other than the refractory. The nozzle for continuous casting according to claim 3. A method for producing a continuous casting nozzle in which the refractory according to claim 1 or 2 is disposed on a part or all of a surface in contact with molten steel,
A part of or all of the layer composed of the refractory according to claim 1 or 2 in the nozzle for continuous casting is formed into a soil composed of a portion other than the refractory adjacent to the layer, and the earth provided for the molding. A method for producing a nozzle for continuous casting, comprising a step of simultaneously pressing adjacent soils to form a molded body having an integral structure. Using a continuous casting nozzle in which the refractory according to claim 1 or 2 is disposed on a part or all of a surface in contact with molten steel, Al ₂ O ₃ inclusions on the wall surface of the continuous casting nozzle, etc. Continuous casting method that prevents adhesion of inclusions.