JP2010005662A - Nozzle for continuous casting and method for manufacturing the same - Google Patents

Abstract

In a continuous casting nozzle in which a high-performance refractory layer such as high corrosion resistance and high anti-adhesion property is arranged on the inner hole side to improve durability, the inner hole side layer and the outer peripheral side layer which is a main body material The nozzle for continuous casting which can prevent the outer peripheral side layer from being cracked due to the difference in thermal expansion between the inner hole and the inner hole side layer during casting, and a manufacturing method thereof are provided.
The boundary portion between the inner hole side layer 2 and the intermediate layer 4 and the boundary portion between the intermediate layer 4 and the outer peripheral side layer 3 have a structure in which they are in direct contact with each other, and the intermediate layer is adjacent to the intermediate layer. The adhesive strength of the hole side layer and the outer peripheral side layer in a non-oxidizing atmosphere at 1000 ° C. is 0.01 MPa or more and 1.5 MPa or less, and the intermediate layer is compressible in a non-oxidizing atmosphere at 1000 ° C. under a pressure of 2.5 MPa. This is a continuous casting nozzle having a rate K (%) of 10% to 80%.
[Selection] Figure 1

Description

  The present invention comprises a nozzle for continuous casting of molten metal, in particular, a tubular refractory structure having an inner hole through which molten metal passes in the axial direction, and a part or all of the region of the tubular refractory structure is formed. The present invention relates to a continuous casting nozzle including an inner hole side layer, an intermediate layer, and an outer peripheral side layer.

  In the present invention, the term “tubular” refers to all shapes having an inner hole in the axial direction, and the cross-sectional shape in the direction orthogonal to the axial direction is not limited. That is, the cross-sectional shape in the direction orthogonal to the axial direction is not limited to a circle, but may be an elliptical shape, a rectangle, a polygon, or the like.

  Further, in the present invention, the “inner hole side layer” is present on the inner hole side with respect to the intermediate layer in the horizontal cross section at any position where the molten steel passage direction (vertical direction) of the continuous casting nozzle is the entire length. The refractory layer is generically referred to, and includes a case where the inner hole side layer includes a plurality of layers, and the thermal expansion coefficient in that case is the maximum value of any one of the inner hole side layers.

  Furthermore, in the present invention, the “peripheral layer” is a general term for a refractory layer existing on the outer peripheral side of the intermediate layer in the cross section, and the outer peripheral layer is composed of a plurality of layers (for example, AG quality). In this case, the coefficient of thermal expansion is the minimum value of any one of the outer peripheral layers.

  Continuous casting nozzles such as long nozzles that discharge molten steel from a ladle to a tundish and immersion nozzles that inject molten steel from a tundish into a continuous casting mold have molten metal such as molten steel that passes near the center in the axial direction. It is comprised from the tubular refractory structure which has a hole, and when a molten steel passes an inner hole, a temperature gradient arises in an inner hole side and an outer peripheral side. In particular, when the discharge and passage of molten steel are started, the temperature is rapidly increased on the inner hole side, and this phenomenon becomes remarkable.

  Such a temperature gradient causes stress distortion inside the refractory regardless of whether the refractory constituting the refractory structure is a single layer or a plurality of layers. This is one of the causes of destruction. As the temperature gradient increases and the thermal expansion coefficient of the inner hole side layer is larger than the thermal expansion coefficient of the outer peripheral side layer, the thermal stress increases and the risk of destruction of the outer peripheral side layer increases.

  On the other hand, since the molten steel flow passes through the inner hole surface of the nozzle for continuous casting while violently colliding, especially the vicinity of the inner hole surface is worn by molten metal or non-metallic inclusions in the molten steel, oxidizing components in the molten steel, etc. Damage due to weakening and loss of structure due to corrosion, reaction melting loss with FeO and other components in molten steel, etc. is significant. In recent years, there has been an increase in non-metallic inclusions in molten steel such as alumina accompanying the upgrading of steel, etc. Blockage and the like are also one of the major factors that determine the life of a continuous casting nozzle.

  Under such circumstances, the durability and safety of the continuous casting nozzle are improved by improving the corrosion resistance and wear resistance of the inner surface, and reducing the adhesion or blocking of non-metallic inclusions on the inner surface. ) Demands are increasing.

  In order to meet these demands, a refractory material with excellent thermal shock resistance is applied to the main body portion of the continuous casting nozzle, that is, the outer peripheral side layer to form the basic skeleton portion of the continuous casting nozzle. A layer having a nozzle inner hole surface that is in contact with the flow, that is, an inner hole side layer, is formed of a material having excellent wear resistance, corrosion resistance, or the like, or a refractory made of a material to which inclusions such as alumina are difficult to adhere. The life of the continuous casting nozzle has been extended by arranging it on a part or the entire surface of the nozzle.

In particular, various functions have been promoted for the inner hole side layer. Recently, a material with a reduced amount of graphite or silica, which is a fusible aggregate, or a material system that does not contain them at all, is Al ₂ O _3. , ZrO ₂ , MgO, and other materials that contain a large amount of corrosion resistance components to achieve high corrosion resistance, and reduce or prevent adhesion of inclusion components such as Al ₂ O ₃ from the molten steel to the inner hole surface Therefore, the application of a submerged nozzle or the like equipped with a refractory layer of a basic material containing a CaO component having high reactivity with the Al ₂ O ₃ component has been advanced.

  The refractory aggregate containing the above components for obtaining such a high-performance refractory has a high thermal expansibility, and the high-function refractory contains a large amount of these refractory aggregates. The side layer tends to be highly expanded. In addition, factors such as an increase in thermal gradient due to a decrease in the thermal conductivity relative to the outer peripheral layer of the inner hole side layer accompanying the reduction of the carbon content add to the thermal expansion amount of the inner hole side layer and the outer peripheral side layer. The difference and the resulting thermal stress tend to increase, and the risk of breakage of the continuous casting nozzle, especially due to the splitting of the outer layer, is further increasing.

  As a general countermeasure against destruction caused by a temperature gradient (thermal stress) of the continuous casting nozzle, for example, fused silica with a small thermal expansion coefficient containing a large amount of graphite in the refractory constituting the continuous casting nozzle, etc. There is a reduction in thermal stress due to high thermal conductivity, low expansion, low elastic modulus, etc., such as adding or increasing the amount. However, the increase in graphite and fused silica, on the other hand, has the detrimental effect of lowering durability such as wear resistance and corrosion resistance due to reduced oxidation resistance and increased reactivity with other refractory components and components in molten steel. Yes, there is a limit to the application to the inner hole side layer, which is not a realistic solution.

  Therefore, in order to avoid the risk of destruction of the continuous casting nozzle, for example, when a molded body that becomes the inner hole side layer is installed on the inner hole side of the outer peripheral side layer, a refractory raw material such as a general oxide is mainly used. The mortar layer itself is made by using a mud-like mortar composed of inorganic binders such as silicates containing a lot of solvent, and also increasing the porosity and low strength of the mortar. An attempt to relieve the stress associated with thermal expansion of the inner hole side layer by breaking the nozzle, that is, by containing a large amount of solvent, a method of avoiding nozzle cracking by applying mortar that exhibits a high porosity even though the adhesive force is relatively low It is taken. However, this mortar crack avoidance measure has the following problems.

(1) Mortar with excessive solvent has the property that the solvent in the mortar is absorbed into the material of the other layer by contact with the nozzle material. In the case of the mortar layer, the porosity of the mortar layer tends to be lower and denser toward the material interface side, so that the stress relaxation function of the mortar layer itself after setting is reduced or disappears.
(2) Apparent porosity cannot be controlled substantially. That is, since it is impossible to control the pore distribution capable of buckling under a predetermined stress, it is necessary to use an excessive amount of solvent, and compatibility with adhesiveness is impossible.
(3) Since the stress relaxation by the mortar layer relaxes the stress by forming a deformation margin of the inner hole side layer by irreversible destruction of the skeleton in the mortar layer forming the pores, Because there is no adhesive force, there is a strong risk of falling off, and because it involves expansion of the space after the mortar collapses due to the temperature change of the nozzle, it easily allows intrusion of molten steel and slag, etc. Erosion or the like often occurs, causing damage to other layers or continuous casting nozzles.

  As another attempt to prevent destruction due to thermal stress while aiming at such high corrosion resistance, for example, Patent Document 1 discloses a refractory with high thermal expansion and high corrosion resistance that does not contain carbon only on the inner hole side. The other outer peripheral side is provided with a carbon-containing refractory layer excellent in spalling resistance to form a two-layer structure, and at least 80% or more of the contact surface between the refractory layers of this two-layer structure is formed. Further, a casting nozzle is disclosed in which a combustible material such as polypropylene and nylon is set at the time of molding and is separated by a separation layer formed by disappearing the combustible material.

  However, in the casting nozzle of Patent Document 1, less than 20% of the contact surface between the refractory layers is bonded. Even if it is a slight adhesion portion, the cracking phenomenon is the starting point because the split stress is transmitted from the inner hole side layer to the outer circumference side layer through this adhesion portion. Further, when the bonded portion is 0%, a basic problem that the inner hole side layer cannot be held as a structure occurs. Furthermore, the molten steel easily penetrates into the separation layer, and when subjected to temperature changes, cracks occur in the refractory due to solidification shrinkage of the molten steel and expansion of the steel during heating, and the inner hole side layer is different from the outer layer. There is a problem of peeling off because they are not bonded.

  On the other hand, in Patent Document 2, a CaO nozzle containing 70 wt% or more of CaO and having an apparent porosity of 50% or less is incorporated in an immersion nozzle for the purpose of suppressing the adhesion of inclusions, and between this CaO nozzle and the base material nozzle. It is disclosed that a gap corresponding to the thermal expansion amount of the CaO nozzle is provided. Further, it is also disclosed that a CaO nozzle is fixed by packing a thin ceramic fiber or a small amount of mortar between the end of the CaO nozzle and the base material nozzle as necessary.

  However, in the structure in which a gap corresponding to the thermal expansion allowance of the CaO nozzle is provided between the inner hole side CaO nozzle (inner hole side layer) and the outer peripheral side base material nozzle (outer side layer), the high expansion As described in paragraph 0022 of Patent Document 2, it is preferable to provide a gap of 3% or more of the CaO nozzle outer diameter at the time of preheating, although the cracking phenomenon of the outer peripheral side base metal nozzle by the CaO nozzle can be suppressed. It is considered that the inner hole side CaO nozzle and the outer peripheral side base material nozzle are not in close contact with each other in the heat (the thermal expansion coefficient of the CaO-based material is the highest level, which is composed of only CaO at about 1500 ° C. The material is about 2% or less.) If the CaO nozzle and the base material nozzle are not in close contact with each other during hot use, that is, when the nozzle is used, there is a risk that the CaO nozzle will be displaced or dropped due to the compressive stress received during use. Also, because molten steel easily enters the gap between the CaO nozzle and the nozzle base material, there is a risk of damage to the CaO nozzle and the nozzle base material on the outer peripheral side due to solidification shrinkage of the molten steel and thermal expansion of the steel when subjected to temperature changes. Accompanied by. Furthermore, the material that produces deoxidation products and low-melting compounds in steel, such as CaO, is a material based on the premise that it will be melted and melted and thinned, and there is no support base behind it. There is a risk of dropping off and destruction.

  Thus, when the design of the joint part between the inner hole side layer and the outer peripheral side layer, such as the separation layer of Patent Document 1 and the gap of Patent Document 2, is too wide, the inner hole due to molten steel intrusion into the joint part. There is a risk of peeling or damage to the side layer and damage to the outer side layer. If it is too narrow, longitudinal cracks may occur in the axial direction of the tubular refractory structure due to the tensile stress acting in the circumferential direction on the outer peripheral side layer due to thermal expansion of the inner hole side layer, or lateral crack damage (axial Cracks in a direction having an angle with respect to the direction, so-called folds, etc.) are likely to occur.

  Therefore, in the case of a continuous casting nozzle equipped with a highly expanded inner hole side layer, in addition to the function of mitigating the effects of stress due to thermal expansion from the inner hole side layer, the structure has a structure in which molten metal does not penetrate or pass easily. Furthermore, the function of adhering the inner hole side layer to the outer peripheral side layer during casting is considered to be important, but heretofore, measures for imparting these three functions or structures have hardly been studied.

In addition, as shown in Patent Documents 1 and 2, etc., in the conventional interior system, the outer peripheral side layer and the inner hole side layer, which are also the main body part of the continuous casting nozzle, are manufactured in separate steps, and finally A process of combining them by installing mortar or the like near the process is required, leading to a decrease in productivity and an increase in manufacturing cost. Furthermore, when combining each refractory layer as such individual parts, the layers are in contact with each other on a smooth surface, and sufficient mutual adhesive strength and fixing force to solve the above-mentioned problems. It is difficult to obtain, and a means for strengthening the adhesive strength with an adhesive or the like is required separately.
JP 60-152362 A Japanese Patent Laid-Open No. 7-232249

  The problem to be solved by the present invention is a continuous casting nozzle in which a highly functional refractory layer such as high corrosion resistance and high anti-adhesion property is arranged on the inner hole side to improve durability, and the inner hole side layer and Provided is a continuous casting nozzle capable of preventing the outer peripheral layer from being cracked due to a difference in thermal expansion from the outer peripheral layer, which is a main body material, and preventing the inner hole side layer from shifting or peeling off during casting. In particular, another object of the present invention is to provide a method for manufacturing such a continuous casting nozzle stably and easily.

  More specifically, it is composed of a tubular refractory structure having an inner hole through which molten metal passes in the axial direction, and the refractory of the inner hole side layer in a part or all of the region of the tubular refractory structure. In the continuous casting nozzle, in which the thermal expansion of the outer peripheral side layer is larger than the thermal expansion of the outer peripheral side layer in the radial direction, (1) the destruction of the outer peripheral side layer is prevented, and (2) the stability during casting of the inner hole side layer And (3) to prevent the intrusion of molten steel or the like into the interlayer including the intermediate layer, in other words, to provide a continuous casting nozzle having a structure satisfying these functions, and to provide the continuous casting It is an object of the present invention to provide an optimum and labor-saving manufacturing method capable of stably obtaining a working nozzle.

The present invention
(1) It consists of a tubular refractory structure having an inner hole through which molten metal passes in the axial direction, and the thermal expansion of the refractory in the inner hole side layer occurs in a part or all of the region of the tubular refractory structure. In the continuous casting nozzle larger than the thermal expansion of the refractory in the outer circumferential side layer in the radial direction,
Between the inner hole side layer and the outer peripheral side layer, an intermediate layer having a contractibility exists as a multi-layer structure integrated at the same time during molding,
The adhesive strength in a non-oxidizing atmosphere at 1000 ° C. between the intermediate layer and the inner hole side layer and the outer peripheral side layer adjacent to the intermediate layer is 0.01 MPa or more and 1.5 MPa or less,
And,
A continuous casting nozzle characterized in that the compressible ratio K (%) of the intermediate layer in a non-oxidizing atmosphere at 1000 ° C. under a pressure of 2.5 MPa satisfies the following formula 1.
K ≧ [(Di × αi−Do × αo) / (2 × Tm)] Equation 1
Di: outer diameter of inner hole side layer (mm)
Do: Inner diameter of outer peripheral layer (mm)
Tm: Initial thickness of the intermediate layer at room temperature (mm)
αi: Maximum thermal expansion coefficient (%) of the refractory material on the inner hole side layer in the range from room temperature to 1500 ° C.
αo: Thermal expansion coefficient (%) at the temperature at the start of steel passing of the refractory on the outer side layer

(2) The intermediate layer contains expanded expansive graphite particles (hereinafter referred to as “expanded graphite particles”) after heat treatment in a non-oxidizing atmosphere at 600 ° C. or higher. A continuous casting nozzle according to claim 1 (claim 2),

(3) The intermediate layer contains a total of 16% by mass (including 100% by mass) of carbon components (excluding compounds with other components) after heat treatment in a non-oxidizing atmosphere at 1000 ° C. The continuous casting nozzle according to claim 1 or claim 2 (claim 3),

(4) After the heat treatment in a non-oxidizing atmosphere at 1000 ° C., the intermediate layer contains a total of 16 mass% or more of carbon components (excluding compounds with other components), and the remainder other than the carbon components is oxidized. A continuous casting nozzle according to claim 1 or claim 2, wherein the nozzle is a refractory raw material composed of at least one of a material, a carbide, a nitride, and a metal.

(5) It consists of a tubular refractory structure having an inner hole through which molten metal passes in the axial direction, and a part or all of the region is in order from the inner hole surface to the radially outer side in order from the inner hole side to the middle. A method for producing a continuous casting nozzle comprising a layer and an outer peripheral side layer,
As an intermediate soil for the intermediate layer, it contains 5% by mass to 45% by mass of unexpanded expandable graphite particles, 55% by mass to 95% by mass of combustible particles, and an organic binder is added to the intermediate layer. The ratio of the carbon component of the organic binder only (excluding compounds with other components) to the entire refractory for the intermediate layer after heat-treating the refractory for use in a non-oxidizing atmosphere at 1000 ° C. is 2. Preparing an earth soil added to the total of the unexpanded expandable graphite particles and combustible particles so as to be 5% by mass or more and 15% by mass or less;
This intermediate layer soil is molded together with the inner hole side layer soil and the outer layer side layer soil by simultaneous and simultaneous pressing with a CIP device,
By heat-treating the obtained molded body at 600 ° C. or higher and 1300 ° C. or lower, combustibles in the molded body for the intermediate layer disappeared to form a space. A method for producing a nozzle for continuous casting, comprising the step of expanding unexpanded expandable graphite in the molded body of the above and filling the space with expanded expanded graphite (Claim 5).

(6) It consists of a tubular refractory structure having an inner hole through which the molten metal passes in the axial direction, and a part or all of the region is arranged in order from the inner hole surface toward the outer side in the radial direction. A method for producing a continuous casting nozzle comprising a layer and an outer peripheral side layer,
As the soil for the intermediate layer, the unexpanded expandable graphite particles are 5% by mass or more and 45% by mass or less, the combustible particles are 55% by mass or more and 95% by mass or less, and oxides, carbides, nitrides, and metals. The organic binder comprising a total of 40% by mass or less of refractory raw materials composed of one or more components, and the organic binder after heat-treating the refractory for the intermediate layer in a non-oxidizing atmosphere at 1000 ° C. The unexpanded expandable graphite particles so that the ratio of only carbon components (excluding compounds with other components) to the entire refractory for the intermediate layer is 2.5% by mass or more and 15% by mass or less. Prepare an earth soil added to the flammable particles and the total of the refractory raw materials composed of one or more of oxide, carbide, nitride and metal,
This intermediate layer soil is molded together with the inner hole side layer soil and the outer layer side layer soil by simultaneous and simultaneous pressing with a CIP device,
By heat-treating the obtained molded body at 600 ° C. or higher and 1300 ° C. or lower, combustibles in the molded body for the intermediate layer disappeared to form a space. A method for producing a nozzle for continuous casting, comprising the step of expanding unexpanded expandable graphite in a green body and filling the space with expanded expanded graphite (Claim 6).
It is.

In order to solve the above problems, in the present invention, in the structure of the nozzle for continuous casting,
(1) installing an intermediate layer having a function of relieving stress between the inner hole side layer and the outer peripheral side layer;
(2) maintaining the form of the intermediate layer as a layer, preventing the layer from collapsing due to breakage, that is, enhancing the stability of the layer,
(3) Adhering and fixing the intermediate layer, the inner hole side layer, and the outer peripheral side layer as a multi-layer structure integrated simultaneously at the time of molding;
These three points were taken as basic equipment conditions.
(Hereinafter, (1) is referred to as “contractable condition”, (2) is referred to as “stability condition”, and (3) is referred to as “adhesive condition”.)

Hereafter, each said condition is explained in full detail.
(1) About the contractibility condition As described above, the inner hole side layer has improved corrosion resistance and wear resistance, restrictions on elution of carbon components from the refractory to molten steel, and non-metallic inclusions such as alumina. Refractory with increased content of Al ₂ O ₃ , MgO, ZrO ₂ , CaO, etc., which is excellent in corrosion resistance, wear resistance, etc., for the purpose of preventing main inclusions from adhering to the inner hole surface or blocking the nozzle. Tend to use.

On the other hand, in many cases, the content of Al ₂ O ₃ , MgO, ZrO ₂ , CaO, etc. in the outer peripheral side layer (including the outer peripheral side layer as a part of the main body part) mainly focusing on thermal shock resistance is the inner hole. Lower than the side layer. For this reason, the thermal expansion coefficient of the refractory material in the inner hole side layer is inevitably larger than that of the refractory material in the outer peripheral side layer.

  The destruction of the continuous casting nozzle due to the cracking or cracking of the outer peripheral layer by the inner hole side layer is noticeably caused by using the above-mentioned refractory having a higher thermal expansion coefficient than the outer peripheral layer on the inner hole side. . Moreover, even if each layer of the inner hole side layer and the outer peripheral side layer is composed of the same or a refractory material having the same thermal expansion characteristics, the destruction is accompanied by preheating from the inner hole side, rapid temperature increase, steel passing, etc. This also occurs when the inner hole side is at a relatively higher temperature than the outer peripheral side and a large thermal gradient occurs between them.

  That is, in the present invention, the case where the thermal expansion of the inner hole side layer is larger than the thermal expansion of the outer peripheral side layer means that the maximum thermal expansion coefficient of the refractory of the inner hole side layer is 1500 ° C. (substantially near the casting temperature range) or less. Of course, the maximum thermal expansion coefficient or the thermal expansion behavior is the same (for example, the material having the same composition, the same structure, etc.). The degree of thermal expansion of the inner hole side layer at the time of heating due to the temperature difference (temperature gradient) between the inner hole side layer and the outer peripheral side layer due to preheating from the steel receiving or inner hole is the thermal expansion of the outer peripheral side layer. Including the case of larger than the degree.

  When there is no or very little function to relieve stress between the inner hole side layer and the outer peripheral side layer, the stress due to the inner hole side layer is expressed as the radial compressive stress on the horizontal cross section, and the long side shaft. In the case of a structure having an outer peripheral layer also on the end side in the direction, it acts on the outer peripheral layer as an axial compressive stress. These compressive stresses are converted into tensile stresses in the outer circumferential layer, radial compressive stresses in the circumferential direction, and axial compressive stresses in the same axial direction. In the latter case, cracks in the axial (= longitudinal) direction occur in the former case and horizontal (= lateral) direction occur in the latter case, and the outer peripheral side layer is damaged.

  In the present invention, as a means for imparting a stress relieving function between the inner hole side layer and the outer peripheral side layer having such a relationship, in the present invention, up to the nozzle preheating process and 1500 ° C. (substantially near the casting temperature range). In the process, an intermediate layer having contractibility and adhesion is installed.

  By installing the intermediate layer, the thermal expansion of the inner hole side layer acts as a compressive stress on the intermediate layer without directly acting on the outer peripheral side layer. At this time, the intermediate layer itself is reduced in thickness in the radial direction according to the compressive stress, and in the axial direction, the thickness in the axial direction is reduced. In other words, by reducing the volume, stress due to expansion of the inner hole side layer can be relaxed. In the present invention, such a property that the thickness and volume can be reduced is referred to as contractibility.

In the case of a tubular refractory material mainly composed of Al ₂ O ₃ -C, which is a general material of the outer peripheral side layer of the immersion nozzle, generally a pressure of several MPa is applied to the inner wall surface of the outer peripheral side layer. And break. For example, in the case of Al ₂ O ₃ -graphite refractory with an outer peripheral side layer (inner diameter φ80 mm, outer diameter φ135 mm) and a maximum tensile strength of 6 MPa, which has a practically minimum radial structure, from the inner wall surface of the pipe When the pressure is applied, if the pressure of about 2.5 MPa is applied to the inner wall surface by calculation from the equation of the wall pressure cylinder, it will break.

  In order to relieve the stress applied to the outer peripheral layer due to the thermal expansion of the inner hole side layer when preheating or casting is started or during the middle layer and inner hole side layer are arranged on the inner hole side of the outer peripheral side layer The intermediate layer itself must exhibit deformation behavior. That is, the stress applied from the inner hole side layer to the outer peripheral side layer needs to be stopped to 2.5 MPa or less by deformation (reduction) of the intermediate layer.

  From the above, in the process of heating the inner hole side layer or through the steel, the tensile stress generated in the outer peripheral side layer is 2.5 MPa or less, and in order to further improve safety, the tensile stress should be suppressed to as small as possible. Preferably, the intermediate layer itself needs to exhibit a deformation behavior under such a compressive stress value that results in a tensile stress value.

The contractibility required for the intermediate layer under a pressure of 2.5 MPa can be expressed by the contraction rate K (%) of the following equation.
K ≧ [(Di × αi−Do × αo) / (2 × Tm)] Equation 1
Di: outer diameter of inner hole side layer (mm)
Do: Inner diameter of outer peripheral layer (mm)
Tm: Initial thickness of the intermediate layer at room temperature (mm)
αi: Maximum thermal expansion coefficient (%) of the refractory material on the inner hole side layer in the range from room temperature to 1500 ° C.
αo: Thermal expansion coefficient (%) at the temperature at the start of steel passing of the refractory on the outer side layer

  Di and Do are the positions of the outer peripheral side surfaces of the inner hole side layer for the planar shape of the inner hole side layer and the outer peripheral side layer on the cross section in the direction horizontal to the axial direction of the target portion in the entire area in the axial direction, It means the diameter of the position of the inner hole side surface of the outer peripheral side layer. Further, when these planar shapes are not circular, the position of the outer peripheral side surface of the inner hole side layer is Di and the position of the outer peripheral side layer on the same straight line extending radially from the center of the planar shape of the inner hole side layer on the plane. If the position of the side surface of the inner hole is Do, the above equation 1 may be satisfied for the entire shape.

  It should be noted that the contractibility at the end in the axial direction is obtained by dividing Di in the formula 1 with respect to the planar shape of the inner hole side layer and the outer peripheral side layer on the cross section passing through the center of the axis in the axial direction (perpendicular direction). The length in the axial direction to the other end with the axially outer side surface position of the hole side layer as one end, and the outer periphery to the other end with Do as the axial inner side surface position of the outer peripheral side layer as one end What is necessary is just to replace with the length of the axial direction of a side layer.

  Here, αi is the maximum coefficient of thermal expansion (%) in the range from room temperature to 1500 ° C. of the refractory in the inner hole side layer, which means that the maximum refractory in the inner hole side layer is substantially up to the molten steel temperature. The coefficient of thermal expansion means that αo is the coefficient of thermal expansion (%) at the temperature at the start of steel passing of the refractory on the outer peripheral side layer. The temperature to which the layer is exposed, and the condition should be determined individually for each site.

When the continuous casting nozzle is used without preheating, the outer peripheral layer is the same as the room temperature (temperature of the surrounding environment), and αo is an expansion rate at room temperature, which is a reference point for measuring the thermal expansion rate, that is, It can be regarded as almost “zero”, and the above equation 1 becomes equation 2.
K ≧ [Di × αi / (2 × Tm)] Equation 2

  The shrinkage ratio K satisfying this expression 2 is the shrinkage ratio considering the most severe condition, that is, the case where the thermal expansion difference between the inner hole side layer and the outer peripheral side layer is maximized. If the shrinkage is equal to or greater than the shrinkage ratio, the outer peripheral layer will not break, but in order to ensure safety that is more difficult to break, it is preferable to set the shrinkage ratio K to satisfy this equation 2 under all operating conditions. .

  Note that K in the formulas 1 and 2 is a target in a non-oxidizing atmosphere in a reducing gas or inert gas atmosphere or in an oxidizing gas atmosphere such as air by applying an antioxidant to the surface. The value under the condition that the refractory is not oxidized. The intermediate layer when using an actual continuous casting nozzle is a non-oxidizing atmosphere. In addition, when the target sample is oxidized in the measurement of K, it is impossible to grasp an accurate property.

  In the present invention, the shrinkage ratio of the refractory material of the intermediate layer is preferably 10% or more and 80% or less.

  By adjusting the thickness of the intermediate layer according to the contractibility of the intermediate layer, the expansion allowance of the inner hole side layer can be reduced, but if it is less than 10%, the inner hole side layer and the outer peripheral side layer Due to the difference in thermal expansion coefficient, the thickness of the intermediate layer must be increased, and the thickness of the nozzle for continuous casting is limited. As a result, the thickness of the main body material is reduced, causing a problem in strength as a structure. On the other hand, if the thickness is greater than 80%, the thickness of the intermediate layer can be designed to be thin, so the above-described problems are unlikely to occur. However, manufacturing problems in forming the thin intermediate layer and the inner hole side layer and the outer peripheral side layer This is likely to cause a problem of lowering the adhesion strength. For example, the inner diameter of the outer peripheral layer, which is near the minimum size of a commonly used continuous casting nozzle, is approximately φ80 mm, the thermal expansion coefficient of the inner hole side layer is 2.0%, and the thermal expansion coefficient of the outer peripheral layer is Assuming a condition of 0.8%, the thickness of the intermediate layer is about 4 mm, the contractibility required for the refractory of the intermediate layer is 10%, the inner diameter of the outer peripheral layer near the maximum size is about φ150 mm, Assuming the condition that the thermal expansion coefficient of the hole side layer is 2.0% and the thermal expansion coefficient of the outer peripheral side layer is 0.8%, the thickness of the intermediate layer is about 1.2 mm, which is necessary for the refractory of the intermediate layer. The contractibility is about 78%.

  The shrinkable rate can be measured by the following method, and the measured value can be regarded as the shrinkable rate.

  A columnar refractory (φ20 × 5 mmt) made of a mixture that has been molded at the same pressure as the molding pressure and has the property of being shrinkable after heat treatment is placed in a carbon-based restraint space having the same shape as the columnar refractory. Then, heat treatment is performed in a predetermined temperature rising pattern in a non-oxidizing atmosphere to eliminate the combustible component, and a cylindrical sample (about φ20 × about 5 mmt) is obtained. The columnar sample after this heat treatment is placed between the end faces of two refractory jigs having a shape of φ20 × 40 mmL. Furthermore, when pressing the sandwiched cylindrical sample from the longitudinal direction, a cylindrical sample guide made of a refractory material having an inner diameter of 20 mm / outer diameter of 50 mm and a height of 78 mm in order to prevent the sample from peeling from the side surface. Is extrapolated to the sample to obtain a measurement sample.

This measurement sample is placed in a furnace of a material testing machine that can control the temperature, atmosphere, and pressurization rate, heated to a predetermined temperature in a non-oxidizing atmosphere, held until the temperature becomes uniform, and then heated. Start pressure and take measurements. First, the initial thickness t ₀ (mm) of the cylindrical sample in a non-pressurized state is measured. Next, after holding the measurement sample at a predetermined temperature, the cylindrical sample is compressed from the vertical direction at a crosshead moving speed of 0.001 to 0.01 mm / sec and pressurized to 2.5 MPa. The displacement amount h ₁ (mm) is measured. The same load of the refractory-made jig for sandwiching a cylindrical sample, in order to measure the blank value at the same temperature, in a state not to pinch the cylindrical sample, measuring the pressurized displacement h ₂ under the same conditions. By calculating these measured values according to the following equation, the shrinkable ratio K (%) at each temperature can be obtained.

K = (h ₁ −h ₂ ) / t ₀ × 100 (%) Equation 3

It can also be measured from an actual casting nozzle having a continuous structure in which the inner hole side layer is integrated with the outer peripheral side layer by the intermediate layer during molding. Core drilling of φ20mm from the outer peripheral side layer to the central axis at right angles to the refractory central axis, and an integrated inner hole and outer peripheral side of about φ20mm including the inner hole side layer, intermediate layer and outer peripheral side layer A core sample with a curvature is obtained. The shrinkage ratio of the intermediate layer is such that the upper and lower surfaces of the core sample are processed horizontally and bonded to a refractory jig so that they can be uniformly pressed, or a refractory jig with the same curvature as the upper and lower surfaces of the core sample. The sample is processed into a predetermined measurement sample of φ20 × 80 to 100 mmL including the inner hole side layer, the intermediate layer, and the outer peripheral side layer. (If the sample for measurement is smaller than the size, it is possible to measure and convert the conditions such as the unit area, unit length, etc. to the same extent as described above by calculation.) The initial thickness t ₀ (mm) of the intermediate layer in the pressure state is accurately measured, the displacement amount h ₁ of the intermediate layer is measured in a non-oxidizing atmosphere at a predetermined temperature, and the intermediate layer has no intermediate layer. the displacement amount h ₂ of the blank value to calculate the measured Kachijimi rate K. By sampling from an actual nozzle, the contractibility of the intermediate layer can be accurately measured.

(2) Stability conditions and adhesive conditions The intermediate layer is sufficient with the inner hole side layer and the outer peripheral side layer from the production of the nozzle for continuous casting to the time of use after satisfying the above-mentioned contractibility. It is necessary to maintain stability and adhesion.

  As described above in the background art, in particular, in the conventional method of buckling a high-liquid-volume, low-strength mortar and high-porosity structure, that is, obtaining contractibility by collapse, the structure after buckling or collapse Becomes a mere powder and cannot maintain the interlayer itself as well as the adhesive strength between the layers. If there is a space between the inner hole side layer and the outer peripheral side layer due to the intermediate layer in such a state, that is, if the interlayer is peeled without being fixed to each other, the intermediate layer itself is If the space is further expanded due to local destruction due to biased stress, etc., or if the intermediate layer has disappeared, the inner hole side layer becomes movable, causing dropout or destruction. Stress concentration and breakage due to contact of the hole side layer with the local outer peripheral side layer are likely to occur. Further, there is a possibility that molten steel or the like may enter such a space to further promote the destruction of the layer or the delamination of the layers.

  For this reason, it is necessary for the intermediate layer having contractibility to be present as an intermediate layer even after compression and to maintain a certain degree of adhesion (described later) with the interlayer.

  The fact that such an intermediate layer has a certain adhesiveness with the inner hole side layer and the outer peripheral side layer means that the refractory material of the intermediate layer itself is necessary for expressing the adhesiveness as a layer as a premise of adhesion. It is assumed that it has the above strength and maintains a healthy layer state, and it is a natural reason.

  Therefore, in the present invention, in order to enhance the stability of the intermediate layer itself and the fixing property between the intermediate layer and the inner hole side layer and the outer peripheral side layer, the adhesion between these layers is enhanced.

  Adhesiveness, i.e., bondability or fixability, can be evaluated as adhesive strength (as described above, as a premise for evaluating adhesiveness, it is considered that the stability is more than necessary to show the adhesive strength. ). The present inventors have found that the optimum range of the adhesive strength is 0.01 MPa to 1.5 MPa in a hot measured value in a non-oxidizing atmosphere at 1000 ° C.

  The minimum value of 0.01 MPa of the adhesive strength is a value obtained as a result of repeating the experiment, and the friction between the minimum layers so that the inner hole side layer and the outer peripheral side layer can maintain a predetermined installation place. This is a value for obtaining resistance. If the adhesive strength is less than 0.01 MPa, the holding capacity of the inner hole side layer is low even if the inner hole side layer does not fall before the start of steel passing. There is a risk of peeling off due to vibrations caused by the vibration, or when local melting damage or the like occurs in the inner hole side layer. In addition, when transporting the nozzle for continuous casting and installing it in a continuous casting apparatus, during preheating, in each stage during steel passing, the inner hole side layer is displaced from a predetermined position by their respective external forces, There is a greater risk of peeling and dropping off. Furthermore, in combination with such a phenomenon, a portion that does not satisfy the necessary contractibility is generated, and therefore, the risk of causing the destruction of the inner hole side layer or the outer peripheral side layer is increased.

  When the adhesive strength exceeds 1.5 MPa, such an adhesive strength means that the strength of the refractory material itself of the intermediate layer is strengthened accordingly. Even in the internal structure of the intermediate layer, it is in a state of high strength that is the same level as the adhesive strength, and the contractibility of the intermediate layer is impaired, and the thermal expansion of the inner hole side layer is propagated to the outer peripheral side layer without relaxation. It becomes easy to increase the risk of breaking the continuous casting nozzle.

  As shown in FIG. 3, this adhesive strength is measured by measuring a portion having an intermediate layer with a horizontal cross section (perpendicular to the longitudinal axis direction) of a continuous casting nozzle having a thickness of about 100 mm parallel to the cross section. A pressure body 11 (a circle made of a refractory material having a flat bottom end) in a furnace maintained at a predetermined temperature and having an outer diameter that is substantially the same as the outer diameter of the inner-hole-side layer. This can be done by pushing down only the inner hole layer 2 with a columnar pusher and dividing the total load by the adhesion area. The temperature during measurement is 1000 ° C., and the atmosphere is a non-oxidizing atmosphere.

  It should be noted that the conditions for measuring the contractibility and the adhesive strength described above are in a non-oxidizing atmosphere at 1000 ° C., and in the specification of the refractory components of the intermediate layer, the heat treatment in a non-oxidizing atmosphere at 1000 ° C. is used. This is because 1000 ° C. is a temperature at which the volatile component in the organic binder component is sufficiently scattered to complete the carbonaceous connective structure and exhibit stable contractibility and adhesion.

  The intermediate layer of the present invention is characterized in that it has an integral multi-layer structure in which a part or all of the refractory structure is formed simultaneously with the inner hole side layer and the outer peripheral side layer at the time of molding. The integral multi-layer structure refers to a state in which there is no space between the layers, and matrix structures near the boundaries of the layers are in direct contact with each other without interposing a third adhesive layer or the like.

  As will be described later, the intermediate layer of the present invention has an integral continuous structure by simultaneously forming the inner hole side layer and the outer peripheral side layer and the soil for each layer by CIP (Cold Isostatic Pressing).

Construction technology for conventional adhesives and mortars (such as “adhesives and mortars” are simply referred to as “mortars” hereinafter), such as molding each layer separately and bonding the compacts via silicate adhesives. However, there are the following problems.
(1) When filling mortar or the like into a thin gap, an unfilled portion or large bubbles are mixed, or an unbonded portion or the like is generated, and the quality of the portion such as mortar is not stable.
(2) Since a large amount of liquid is contained to ensure workability, the liquid is absorbed by the layer to be bonded, causing shrinkage of the mortar and the like, and shrinkage cracks of the mortar and the like themselves and space on the bonding surface (peeling) Is likely to occur.
(3) Since there is an abrupt tissue change at the boundary between layers, stress tends to concentrate on the boundary, and the adhesive part is easily broken or the adhesive part is peeled off.
(4) In a high temperature range such as during steel passing, the component such as adhesive reacts with the component of the layer to be softened or melted, the adhesive strength is reduced, or the layer itself contracts or deforms, and the layer The fixing force is weakened, and there is a greater risk that the inner hole side layer will fall off, peel off, or the outer peripheral side layer will break.

In contrast to such a conventional technique, the integrated structure of the present invention is an adhesive form based on mechanical entanglement of the constituent components of each layer, and therefore the following effects can be obtained.
(1) It is possible to uniformly disperse a predetermined amount of combustible particles throughout the soil during the manufacture of the soil, and the volume of the disappeared portion of the combustible particles accompanying the heat treatment is expanded graphite having a fine space. Since the particles are replaced and filled with particles, a uniform and stable contractible amount can be controlled.
(2) Adhesion through a binder component such as carbonaceous material in the intermediate layer is also manifested in the heat treatment process, and is uniform and stabilized.
(3) The expanded graphite particle portion having a fine lamellar space in the intermediate layer expands and contracts so that the accordion expands and contracts by the fine space formed by expanded graphite being finely dispersed throughout the structure in the heat treatment process after forming. By doing so, it is possible to maintain the adhesive force without causing large tissue destruction as the intermediate layer, and the expansion of the inner hole side layer can be absorbed uniformly.

  For this reason, there is little risk that the inner hole side layer will drop off, peel off, or the outer peripheral side layer will break, and strong interlaminar fixing properties or stability of each layer can be obtained.

  Also, by performing such simultaneous integral molding, the continuous casting nozzle having the above-mentioned characteristics is compared with the case where construction of mortar or the like of the prior art is performed. Can be stably obtained in a highly accurate state with a small amount (in the process of expansion of expandable graphite, the pressure accompanying the expansion is generated inside the intermediate layer, and the intermediate layer is mainly composed of expanded graphite. The product is made uniform for reasons such as self-filling and dispersing so that the internal pressure is averaged in the space where the combustible material has disappeared), and the manufacturing process is simplified, labor-saving, manufacturing time is shortened, and cost is reduced. Can be realized.

  In order to ensure the above-mentioned contractibility, adhesion and stability, the intermediate layer of the present invention has a structure in which a flaky unit layer made of carbon having a thickness of 1 μm or less forms a layer through a space (“thickness The flaky unit layer of carbon having a thickness of 1 μm or less is referred to as a “lamellar layer shape through a space”. This structural portion is mainly composed of particles in an expanded state (referred to as “expandable graphite” in the present invention) having expandable graphite (referred to as “expandable graphite” in the present invention).

  The contractibility of the intermediate layer of the present invention is mainly due to the fact that the expanded graphite particles having the structure of the lamellar layer compress the space between the layers against an external force and that the lamellar layer itself deforms flexibly. Brought about. If the thickness of the carbon flake layer is 1 μm or less, the property of being deformed flexibly by external force while maintaining the shape of the carbon flake layer itself is strengthened, and further, a space of about 10 μm or more and 200 μm or less between the carbon flake layers is formed. It can be a space necessary for deformation and movement of the carbon flake layer. In addition, the presence of such a carbon flake layer and space intricately intertwined in three dimensions makes it possible to disperse stress in all directions, thereby improving the contractibility, that is, the stress relaxation effect. it can.

  In the present invention, unexpanded expandable graphite particles are contained in an amount of 5% by mass to 45% by mass and combustible particles are contained in an amount of 55% by mass to 95% by mass. There is no crack or exfoliation by using an intermediate layer for which an organic binder is added as an outer layer so that the proportion of the total refractory for the layer is 2.5% by mass or more and 15% by mass or less. In addition, an intermediate layer having a desired shrinkage ratio and adhesive strength can be formed after heat treatment in a non-oxidizing atmosphere at 600 ° C. or higher and 1300 ° C. or lower.

  In the present invention, the unexpanded expandable graphite particles are 5% by mass or more and 45% by mass or less, the combustible particles are 55% by mass or more and 95% by mass or less, and the balance is 1% of oxide, carbide, nitride, metal. 40% by mass of a refractory material composed of more than one component, and the proportion of the total refractory for the intermediate layer as a carbon component after heat treatment in a non-oxidizing atmosphere at 1000 ° C. is 2.5% by mass to 15% by mass By using the soil for the intermediate layer to which the organic binder is added as an outer cover, there is no crack or peeling, and the intermediate layer having the desired shrinkage ratio and adhesive force is 600 ° C. or higher and 1300 ° C. or lower. It can be formed after heat treatment in a non-oxidizing atmosphere.

  The contractibility of the intermediate layer of the present invention is such that a part or all of the volume of the combustible particles and the organic binder in the layer is expanded in the process of disappearing during heating. This is achieved by replacing with graphite oxide. The expansive graphite is preferably one in which the organic component starts to expand in a temperature range almost the same as the temperature at which the disappearance of heat begins, and is selected from the expansive graphite having a different expansion start temperature depending on the disappearance start temperature of the combustible particles. In general, the temperature is appropriately selected from an expansion start temperature range of 130 ° C to 350 ° C. The particle size of the expandable graphite is preferably 50 to 800 μm, more preferably 100 to 600 μm. When the thickness is less than 50 μm, the ability to fill a fine space is excellent, but the expandability during heating is poor and it is difficult to obtain desired contractibility. On the other hand, if it is larger than 800 μm, the expandability is excellent and the contractibility is excellent, but the three-dimensional entanglement of the graphite particles is small and the adhesive strength tends to be lowered.

  As a constituent of the refractory of the intermediate layer after heat treatment in a non-oxidizing atmosphere at 1000 ° C., the balance other than the expanded graphite contains one or more kinds of refractory materials of oxide, carbide, nitride and metal. be able to.

  Among these, the other refractory material particles as the remaining components other than the carbon component mainly have a function of ensuring the corrosion resistance of the intermediate layer. Specifically, when the intermediate layer is damaged, it prevents or prevents the molten steel or the like from coming into direct contact with the outer peripheral side layer that is inferior in corrosion resistance, and also ensures the corrosion resistance and wear resistance of the intermediate layer itself. It also serves a skeletal function for maintaining the strength of the intermediate layer as a refractory.

  The continuous casting nozzle has a locally damaged portion such as a damaged portion of the inner hole side layer itself, a boundary portion between the inner hole side layer and the nozzle body, a fragile portion such as a gas blowing gas pool portion or an interlayer joint portion. In addition, there is a portion that is already directly exposed to the molten steel in a state as a product of a continuous casting nozzle, such as a discharge hole portion of an immersion nozzle. If the corrosion resistance, wear resistance, etc. of the part directly exposed to such molten steel are weak, the molten steel penetrates between the inner hole side layer and the outer peripheral side layer due to selective disappearance of the part, etc. This will cause the destruction of the nozzle for continuous casting which is fatal in the operation of continuous casting.

As a refractory material applied to the refractory portion of the intermediate layer directly exposed to such molten steel, a refractory composed of one or more components selected from the group of Al ₂ O ₃ , SiO ₂ , MgO, CaO, and ZrO _2. Aggregate, specifically alumina-silica (corundum, mullite, sillimanite, kayanite, kaolinite are preferably selected in the order described above from the viewpoint of obtaining corrosion resistance against molten steel), alumina-magnesia. Spinel, zirconia, zircon, alkaline earth metal oxide, etc. can be selected and used depending on the degree of corrosion resistance required under the conditions of individual operations. In addition, refractory materials made of silica alone and glassy refractory materials containing alkali metal components cause problems such as vaporization in a reducing atmosphere, oxidation of metal components and carbon components, and formation of low-melting materials with other refractory materials. It is preferable not to use.

  Furthermore, carbides such as silicon carbide and titanium carbide, nitrides such as BN and silicon nitride, and the like can be included for the purpose of suppressing oxidation of the refractory in the intermediate layer.

  The remaining refractory material is not an indispensable element, so it is not included unless the corrosion resistance etc. need to depend on the remaining refractory material in light of the individual operating conditions and the damage situation of the continuous casting nozzle. It doesn't matter.

  In addition, the refractory material of the intermediate layer of the present invention is mainly composed of carbon having high stability in a high temperature range even at a temperature of about 1000 ° C. or higher at which a reaction such as sintering or low melting of oxides starts or increases. Therefore, since the intermediate layer itself has high stability, the expanded graphite is dispersed so as to cover other refractory material particles, so that the mutual reaction of refractory aggregates such as other oxides. It is an advantage of the present invention mainly composed of expanded graphite that there is almost no generation of sintering, shrinkage, low melting, etc., and no generation of space due to sintering or softening of the constituent refractory materials.

  The refractory material particles constituting the refractories of the intermediate layer are bonded to each other by a bonding material. As a binder, after heat treatment at 600 ° C. or higher, a carbonaceous connective structure starting from a thermosetting resin, tar, pitch, etc. maintains the contractibility of the refractory in the intermediate layer. In addition, it is preferable for preventing the softening or melting and maintaining the bonding function even at a high temperature.

  For this reason, in the present invention, the total amount of the refractory in the intermediate layer after the heat treatment in the non-oxidizing atmosphere at 1000 ° C. is obtained by converting the organic binder to the carbon component of the binder after the heat treatment in the non-oxidizing atmosphere at 1000 ° C. It is added so that it may become 2.5 mass% or more and 15 mass% or less with respect to the component (including carbon components other than the carbon component of the said binder). If it is less than 2.5% by mass, it is advantageous for the expansion of the expandable graphite and the contractibility of the intermediate layer, but sufficient adhesive strength between the inner hole side layer and the outer peripheral side layer cannot be obtained. On the other hand, if it is more than 15% by mass, the adhesive strength is advantageous, but the expansion of the expandable graphite during the heat treatment process is hindered, so that it becomes difficult to ensure the contractibility required for the intermediate layer.

  Furthermore, in order to ensure the contractibility and sound structure required for the intermediate layer, it is necessary to contain expanded graphite particles as a carbon component in an amount of 13.5% by mass or more. If the content is less than 13.5% by mass, the possibility of generating a weak portion of the structure of the intermediate layer increases, and the occurrence of shrinkage cracks in the intermediate layer itself and the adhesion to the inner hole side layer and the outer peripheral side layer decrease. The possibility increases.

That is, the intermediate layer of the present invention includes expanded graphite particles and an organic binder component after heat treatment in a non-oxidizing atmosphere at 1000 ° C., and the total of the expanded graphite particles and the organic binder component is a carbon component (for example, 16% by mass or more (including 100% by mass) as a component (excluding compounds with other components such as SiC, B ₄ C, and AlC). That is, the lower limit of 16% by mass of the total carbon component indicates the total amount of the minimum content of expanded graphite particles of 13.5% by mass and the minimum content of organic binder component of 2.5% by mass. The portion exceeding 16% by mass may be composed only of an organic binder component (maximum content 15% by mass) and expanded graphite particles, or other than the above expanded graphite particles and organic binder component, You may be comprised with carbonaceous components, such as general scaly graphite and carbon black.

  Further, the balance when the total carbon component is 16% by mass or more and less than 100% by mass includes a total of 84% by mass or less of a refractory raw material composed of one or more components of oxide, carbide, nitride, and metal. be able to.

  Note that the adhesive strength also varies depending on the balance between the content of the binder and the content of combustible particles in the soil.

  Binders such as silicates and phosphates that contain a large amount of alkali metals may cause softening of oxides, melting, or vaporization of carbon components, resulting in deterioration of the structure of the intermediate layer or other adjacent layers. Therefore, it is preferable not to use it. In order to maintain the structure strength particularly in a low temperature range (for example, 600 ° C. or less), it is possible to use an organic resin or the like that does not leave carbon.

  Next, the intermediate layer refractory according to the present invention and the production method for obtaining the continuous casting nozzle provided with the intermediate layer refractory will be described.

  The nozzle for continuous casting having the compressible intermediate layer of the present invention comprises a step of producing a dedicated clay for each of the inner hole side layer, the intermediate layer and the outer peripheral side layer, and the inner mold side layer in the molding mold. A step of providing a plurality of spaces partitioned into a predetermined size for forming the intermediate layer and the outer peripheral side layer, and filling each of the spaces in the molding mold with a dedicated earth, The step of directly contacting adjacent soils by removing the partition of the material, the step of pressing these directly contacted soils by pressing with a CIP device, and the resulting molded body in a non-oxidizing atmosphere Or it can obtain by the manufacturing method including the process of heat-processing in 600 degreeC or more and 1300 degrees C or less in the oxidation atmosphere in the state which gave the antioxidant process to the surface. Prior to the heat treatment step, an independent heat treatment step for removing volatile components or curing the resin may be included at a temperature lower than the temperature.

  The basic operation / working method of each step and the apparatus used are the same as those of a general continuous casting nozzle manufacturing method. The continuous casting nozzle manufacturing method of the present invention is the following first. To the third feature.

  The first feature is the structure of the refractory earth for the intermediate layer. The intermediate soil is a powder part excluding volatile matter. (1) 5 to 45% by mass of unexpanded expandable graphite particles and (2) 55% by mass or more of combustible particles 95% by mass or less, (3) optionally containing 40% by mass or less (including zero) of a refractory raw material composed of one or more components of oxide, carbide, nitride and metal in the balance, and The carbon component (compound with other components) of only the organic binder after heat treating the refractory for the intermediate layer in a non-oxidizing atmosphere at 1000 ° C. with respect to the total of the powder portions. Except for the intermediate layer of the refractory for the intermediate layer, so that the ratio is 2.5% by mass or more and 15% by mass or less.

  The second feature is that each layer is CIP-molded as a single piece without joints at the boundary.

  The third feature is that in the process of heat-treating the integrated molded body at 600 ° C. or higher and 1300 ° C. or lower, combustibles in the molded body of the intermediate layer are removed to form a space, and then unexpanded The purpose of this is to expand the expandable graphite.

  These features are described in detail below.

  The intermediate layer refractory comprising the expanded graphite of the present invention as a main component is the degree of contractibility necessary for the state of the above-mentioned product (synonymous with the contraction rate satisfying the above-mentioned formula 1; hereinafter simply “ It is difficult to install the refractory having the product shrinkability)) or having the same structure during the molding process of the nozzle for continuous casting using the refractory or the earth soil. That is, CIP molding on the premise that it is manufactured by an apparatus according to a general continuous casting nozzle manufacturing method, basic operation / working method, etc. (normal molding pressure is much higher than 2.5 MPa) In other words, the refractory having shrinkability is compressed by the molding process, and the refractory after molding loses the contractibility. Therefore, a continuous casting nozzle is manufactured using a refractory having the same compressibility as that of the product, or its soil, and the product has compressibility and has an integral structure. It is difficult to obtain a continuous casting nozzle.

  Therefore, in the step of forming at the same time for integration at least under high pressure, the volume of the shrinkage due to the filling of the refractory powder for a normal continuous casting nozzle during the CIP molding is not included in the molding earth. Except for the contractibility (hereinafter simply referred to as “tightening allowance” in order to distinguish from the contractibility described above), there should be almost no contractibility comparable to product contractibility.

  The production method of the present invention makes it possible to obtain a continuous casting nozzle in which the refractory material in the intermediate layer has a product shrinkability and an integral structure.

  According to the soil having the structure shown in the first feature, the expanded graphite after expansion, which is the main component responsible for the contractibility in the product state, has a special contractibility in the unexpanded state. Since this soil is hardly present, even if this soil is exposed to high pressure by CIP molding, each component hardly reduces its volume. Can be stopped. Thereby, predetermined | prescribed volume, such as the thickness required as an intermediate | middle layer and the dimension of an axial direction, can be ensured.

  By using the soil that can withstand such CIP molding, it can be molded simultaneously with the refractory soil for the inner hole side layer and outer periphery side layer other than the refractory soil for the intermediate layer. It becomes possible.

  The unexpanded expansive graphite particles in the intermediate layer are preferably 5% by mass or more and 45% by mass or less. If the amount is less than 5% by mass, the shrinkability of the refractory layer after the heat treatment becomes excessively small, and in order to satisfy the above-described formula 1 regarding shrinkability, it is necessary to excessively increase the thickness of the intermediate layer. It is not preferable because the design is restricted by the thickness of the refractory, and the contractibility of each part in the layer is likely to vary. On the other hand, if the amount of unexpanded expandable graphite particles exceeds 45% by mass, the expandable graphite expands exceeding the volume of the space generated by the disappearance of the combustible particles. There is a problem that the pressure in the product becomes too large, and the outer peripheral side layer is destroyed, resulting in a decrease in manufacturing yield.

  55 mass% or more and 95 mass% or less of the combustible particle | grains in the said soil for intermediate | middle layers is preferable. If it is less than 55% by mass, the space volume lost by heating the combustible particles during the heat treatment in the production process becomes too small, and the space between the layers of the expanded graphite is filled after the space is expanded due to the expansion of the expandable graphite. Can not be sufficiently secured, and there is a greater risk of shrinkage reduction. If it exceeds 95% by mass, the space volume after disappearance becomes excessive, and even after filling the space accompanying expansion of the expandable graphite, the space including the space between the layers of expanded graphite becomes excessive, and the strength of the layer itself The risk of causing a decrease in adhesiveness is increased. The content of combustible particles is preferably equal to or greater than the content of expandable graphite. As the combustible particles, polyethylene particles, polyester powder, cereal powder and the like can be used. The flammable particles are preferably as small as possible with a particle size of about 45 μm or less in order to form a uniform space and obtain a uniform expanded graphite structure.

  The amounts of unexpanded expandable graphite particles and combustible particles in the intermediate layer of the soil may be determined by relative adjustment so as to satisfy the above-described formula 1 relating to shrinkability.

  The remainder of 40% by mass or less in the intermediate layer soil (the minimum amount of unexpanded expandable graphite particles is 5% by mass, and the minimum amount of combustible particles is 55%. 100-5−55 = 40, and the minimum value is zero.) Can be composed of a refractory material composed of one or more components of oxide, carbide, nitride, metal, These components are not essential and may not be included. These refractory materials include expandable graphite according to the structure and shape conditions of individual operations, equipment, etc., that is, according to the degree of corrosion resistance to be provided in the intermediate layer, and according to the degree of contractibility. Depending on the amount of combustible particles (in this case, as the remainder), the type, configuration, amount, etc. are selected from the viewpoint of controlling the reactivity with the material of the inner hole side layer or outer peripheral side layer. You can decide.

  Therefore, the carbon component after heat treatment at 600 ° C. or higher of the refractory of the intermediate layer of the nozzle for continuous casting of the present invention includes the portion excluding the binder or the entire binder including the binder when only the carbon system is used for the binder. In contrast, the maximum content may be 100% by mass.

  Next, when the intermediate layer contains unexpanded expandable graphite particles, combustible particles, and other refractory material particles in the remainder, these refractory material particles (collectively "raw material particle powder") Is mixed evenly. Then, a binder for adding fluidity, wettability and shape retention, a binding function, etc. (a solvent can be used, in which case the solvent is also added) is added to the uniformly mixed raw material particle powder. Knead uniformly.

  Yes, it is necessary to ensure the shape retention at the time of molding and the subsequent process and the strength of the refractory after the heat treatment. Therefore, in the present invention, one or more organic binders such as various tars, pitches, phenol resins, furan resins, etc. account for the proportion of the total refractory for the intermediate layer in terms of carbon components after heat treatment in a non-oxidizing atmosphere at 1000 ° C. It is added so that it becomes 2.5 mass% or more and 15 mass% or less. More specifically, the amount of the organic binder added is the total mass of solids (non-1000 ° C) with respect to a total of 100 parts by mass of the powdery part composed of the above expandable graphite, combustible particles, and the remaining refractory material. The amount of carbon components after heat treatment in an oxidizing atmosphere and the total value of other organic binders that do not retain carbon components after heat treatment in a non-oxidizing atmosphere at 1000 ° C., converted to solid content excluding solvent at room temperature) The amount is preferably 5 parts by mass or more and 30 parts by mass or less. This is because if the solid content of the organic binder is less than 5 parts by mass or more than 30 parts by mass, the fluidity and compressibility during molding of the soil, the strength after molding, and the like are lowered.

  In addition, in order to ensure strength in the low temperature range from room temperature to about 300 ° C or lower, such as mainly for shape retention after molding, an organic substance that does not leave carbon components (carbon bonds) at about 600 ° C or higher. A binder can also be used in combination.

  As an organic binder that does not leave a carbon component (carbon bond), an organic adhesive such as an acrylic resin, a vinyl acetate resin, a polyester resin, or a polyacrylonitrile resin can be used in combination.

  When using an organic binder that does not leave such a carbon component (carbon bond), the amount as a solid content (room temperature) excluding the solvent and the heat treatment of the organic binder in a non-oxidizing atmosphere at 1000 ° C. What is necessary is just to add so that the total amount with the amount of carbon components may be 5 mass parts or more and 30 mass parts or less by outer coating.

  In order to improve the strength after heat treatment in the production of the continuous casting nozzle of the present invention, it is preferable to increase the use ratio of pitches. This strength is based on the premise that the strength of the refractory itself of each layer is equal to or greater than its adhesive strength, and the binder that produces carbon bonds also contributes to the strength of the intermediate layer itself.

  In the case of bonding with mortar using an inorganic binder such as silicate, etc. (or constituting a layer corresponding to an intermediate layer) mainly composed of ordinary oxides often used in the prior art In particular, in the temperature range of 1000 ° C. to 1500 ° C., the reaction between the oxide component and the alkali metal oxide causes the softening, and the adhesive strength gradually decreases or the melting occurs at 1200 ° C. or more. This often results in a significant decrease in the adhesive strength, causing shrinkage or melting or collapse of each layer, and creating a space between the layers, which often impairs the sound structure of the continuous casting nozzle.

  In contrast to such a conventional technique, according to the joint structure of the present invention, since it is a structure mainly composed of carbonaceous bonds, it does not contain components accompanying sintering promotion or low melting, and deteriorates even at high temperatures. Since there is almost nothing, such a problem can be solved.

  Separately from the above-mentioned intermediate layer soil, a dedicated soil is prepared for each of the inner hole side layer and the outer peripheral side layer.

  The soil of the inner hole side layer and the outer peripheral side layer can be appropriately determined arbitrarily so as to suit the conditions and purpose of individual continuous casting. However, it is premised on having various properties such as fillability, shape retention, strength development, etc. that can be simultaneously molded by CIP.

  Next, a plurality of spaces divided into a predetermined size are provided in the molding mold for CIP to form the inner hole side layer, the intermediate layer, and the outer peripheral side layer, and a predetermined soil is placed in each predetermined space. Fill.

  Thereafter, these adjacent soils are brought into direct contact with each other without being separated. In this process, separate spaces for filling the soil for each layer are separated in advance by a partition plate or the like, and each space for each layer is filled with each soil, and then the partition plate. It is possible to adopt a method in which the soil for the intermediate layer and the soil for each adjacent layer are directly contacted without any boundary. Alternatively, either 1 or 2 of the soil for the intermediate layer, the inner hole side layer, and the outer peripheral side layer is temporarily formed (a temporary molded body is manufactured), and this is placed in a CIP molding mold. A method of filling a predetermined space with the soil for the layer adjacent to the temporary molded body may be employed. Furthermore, it is also possible to press and unite multiple times step by step for each filling of the soil in the same mold, and finally to simultaneously press and integrate them.

  Next, pressurization is performed by a CIP apparatus. The conditions such as pressure and pressurization time during molding may be the same as those of a general continuous casting nozzle (about 150 MPa).

  Through these steps, an integral molded body in which the refractories for each layer have a multilayer structure can be obtained.

  The obtained molded body may be subjected to drying of several hundred degrees C or less, etc., but heat treatment at 600 ° C. or higher and 1300 ° C. or lower in a non-oxidizing atmosphere or an oxidizing atmosphere in which the surface is subjected to an antioxidant treatment. I do. In this heat treatment step, the combustible material (flammable particles, solvent, etc.) in the molded body of the intermediate layer is lost to form a space, and then the unexpanded expandable graphite is expanded to The space formed after removing the combustible material is filled with expanded graphite (expanded graphite).

  That is, the volume portion occupied by the combustible particles in the soil is replaced by the multi-layer structure particles with the carbonaceous layer and the space after the expansion of the expandable graphite, and the fine and uniform space. A refractory layer having a volume and contractibility can be obtained.

  The disappearance of the combustible material and the expansion phenomenon of the unexpanded expansive graphite proceed from about several hundred degrees Celsius, and it is preferable to treat at a temperature of 600 degrees Celsius or higher in order to complete these changes reliably. On the other hand, when the heat treatment temperature exceeds 1300 ° C., there is a high possibility that the physical properties of the refractory parts other than the refractory of the intermediate layer of the present invention other than the main body of the continuous casting nozzle will cause an undesirable change in terms of thermal shock resistance and the like. Therefore, the maximum temperature is preferably 1300 ° C. or lower.

  Thereafter, various processes such as cutting, polishing, and antioxidant treatment can be performed as necessary. Through these steps, the continuous casting nozzle of the present invention can be obtained.

  According to the manufacturing method having the features of the present invention, it is possible not only to obtain a continuous casting nozzle excellent in shrinkability and adhesion, but also to produce a continuous casting nozzle according to the prior art, that is, individual parts for each layer. Compared with the manufacturing method by the process of combining them, bonding with adhesive or mortar, and drying, etc., it can realize a significant reduction in the number of processes and cost, and improve productivity At the same time, it is possible to improve the accuracy of the dimensions and the like of the continuous casting nozzle.

  By the continuous casting nozzle of the present invention, a layer of a refractory having a high function such as high corrosion resistance and high inclusion adhesion preventing property on the inner hole side, that is, the thermal expansion coefficient of the inner hole side layer is larger than that of the outer peripheral side layer. Inner hole side, such as continuous casting nozzles with improved durability, even when the inner hole side layer and outer peripheral side layer have similar thermal expansion characteristics, but there is a large thermal gradient due to rapid heating, etc. It is possible to prevent the outer peripheral layer from being cracked due to a difference in thermal expansion between the layer and the outer peripheral layer.

  Moreover, since each layer is a structure integrated with each other, it is possible to obtain a bonding force and a fixing force between the respective layers that do not require a special adhesive or the like and are superior to a bonding method using an adhesive or mortar. .

  As a result, the thermal shock resistance, stability and the like of the continuous casting nozzle can be greatly improved, and realization of high functionality and high durability of the continuous casting nozzle by multilayering can be promoted.

  Furthermore, the manufacturing method of the present invention enables simultaneous and integral molding, and can continuously obtain a nozzle for continuous casting having the above-mentioned excellent characteristics with high accuracy, high quality, and simplification of the manufacturing process. It is possible to achieve labor saving, shortening of the manufacturing time, and cost reduction.

  The best mode for carrying out the present invention will be described based on examples.

  The present invention was applied to a tubular refractory structure called a long nozzle used for transferring molten steel between a pan and a tundish in a continuous casting process.

As shown in FIG. 1, the distribution structure of the long nozzle 1 (inner hole diameter: φ140 mm, straight body outer diameter: φ226 mm, length 1500 mm) has a maximum thermal expansion rate of up to 1500 ° C. as the inner hole side layer 2. 8% MgO—C material (MgO = 77% by mass, C = 19% by mass) is distributed over the entire inner hole surface with a thickness of 10 mm, and the outer peripheral side layer 3 is not immersed in the molten steel bath (unimmersed part) Side) with an Al ₂ O ₃ —SiO ₂ —C material (Al ₂ O ₃ = 50 mass%, SiO ₂ = 25 mass%, C = 25 mass%) having a maximum coefficient of thermal expansion up to 1500 ° C. of 0.5%. The material was distributed at a thickness of 30 mm, and the intermediate layer 4 for relaxing the thermal expansion of the inner hole side layer 2 had a thickness of 3.0 mm.

  The soil for the intermediate layer 4 contains unexpanded expandable graphite particles as an expanding agent, polyethylene particles as flammable particles, alumina and magnesia particles as refractory aggregates, and pitch powder as an organic binder. And an acrylic resin were added as outer shells, and after granulating in a high speed mixer, the residual volatile matter was adjusted in a fluidized drying furnace to adjust the plasticity during molding. After that, the granulated soil obtained by drying was sized to 1 mm or less to prepare an intermediate layer.

  Details are shown in Table 1. The shrinkage ratio and hot bond strength (compression shear strength) of the intermediate layer in Table 1 were measured by the method described above. In the long nozzle 1 of the present embodiment, the contraction ratio required for the intermediate layer according to the formula 1 is 34% or more.

  For comparison, Comparative Example 1 was prepared by interpolating the inner hole side layer 2 into the outer peripheral side layer 3 using a general mud-like mortar. In Comparative Example 1, the contractibility of the intermediate layer measured from the actual shape was not obtained, and cracks and peeling of the inner hole side layer occurred in the outer peripheral side layer in the first pouring test.

Comparative Example 2 is a case where 50% by mass of expansive graphite is contained, the remainder is 50% by mass of flammable particles, and 5 parts by mass of pitch is externally added. Occurred. This is because the expansive graphite exceeds 50% by mass, which exceeds the upper limit of 45% by mass, and the outer peripheral side layer was cracked by the expansion force of the expansive graphite during the heat treatment process.

  In Examples 1 to 3 and Comparative Examples 3 and 4, the carbon component of pitch powder (hereinafter referred to as the carbon component amount in a non-oxidizing atmosphere at 1000 ° C.) is used as an organic binder with 45% by mass of expandable graphite. And “pitch charcoal component”) are evaluated by changing 2.0 to 16% by mass.

  As the pitch charcoal component increases, an increase in adhesive strength is observed.

  In Examples 1 to 3 and Comparative Example 3, the expandable graphite was sufficiently expanded during the heat treatment process to fill the space occupied by the polyethylene particles, and a large contractibility could be obtained. However, in Comparative Example 3 in which the pitch charcoal component was reduced to 2% by mass, sufficient adhesive strength was not obtained, and the inner hole body was peeled off by the pouring test. Further, in Comparative Example 4 in which the pitch charcoal component was increased to 16% by mass, the adhesive strength was too strong, and sufficient contractibility was not obtained, and a crack occurred in the first pouring test.

  In Examples 1 to 3, the yield of the actual shape and repeated results of the pouring test did not cause any problems, and good results were obtained.

  Comparative Example 5 is a case where no expansive graphite was used, but required levels of both contractibility and adhesive strength could not be obtained, and a peeling phenomenon occurred even in a pouring test.

  In Examples 4 to 6, the combustible particles were further increased, but both the compressibility and the adhesive strength were sufficiently obtained, and good results were obtained.

  Comparative Example 6 is a case where combustible particles were further increased. Although the compressibility was sufficient, the adhesive strength could not be obtained, and a dropping phenomenon occurred in the pouring test.

  Example 7 and Example 8 are the cases where a part of combustible particle | grains were substituted by the refractory particle | grains. The compressibility and adhesiveness were sufficiently obtained, and good results could be obtained. In Comparative Example 7, although the refractory particles were further increased as compared with Example 7, sufficient contractibility was not obtained, shrinkage cracks were observed in the intermediate layer, and sufficient adhesive strength was not obtained. As a result, the peeling phenomenon of the inner hole side layer occurred in the second pouring test.

  In the above embodiment, the present invention is applied to the long nozzle shown in FIG. 1. However, the present invention is not limited to this. For example, the present invention can also be applied to a tubular refractory structure as shown in FIG.

  2A and 2B are applied to the same long nozzle as the example of FIG. 1, but the example of FIG. 2A uses the refractory of the outer peripheral side layer 3 as the lower end portion of the long nozzle 1. The intermediate layer 4 is also disposed between the lower end portion of the inner hole side layer 2 and the outer peripheral side layer 3. Further, in the example of FIG. 2B, the refractory of the outer peripheral side layer 3 is also arranged at the upper end and lower end of the long nozzle 1, and the upper end and lower end of the inner hole side layer 2 and the outer peripheral side layer 3 are arranged. The intermediate layer 4 is also disposed therebetween.

  The example of FIG. 2C is applied to an immersion nozzle. In the immersion nozzle 1 ′ shown in FIG. 2 (c), the outer peripheral side layer 3 is composed of an AG material 3 a and a ZG material 3 b, and a discharge hole 5 is provided on the side surface as a bottomed structure. The inner hole side layer 2 also has a bottomed structure, and the intermediate layer 4 is disposed between the inner hole side layer 2 and the outer peripheral side layer 3.

It is sectional drawing which shows the long nozzle to which this invention is applied. It is sectional drawing which shows the other example of application of this invention. It is explanatory drawing which shows the measuring method of the hot bond strength of an intermediate | middle layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Long nozzle 1 'immersion nozzle 2 Inner hole side layer 3 Outer peripheral side layer 3a AG material 3b ZG material 4 Intermediate layer 5 Discharge hole 10 Sample 11 Pressurizing body

Claims (6)

It consists of a tubular refractory structure having an inner hole through which molten metal passes in the axial direction, and the thermal expansion of the refractory in the inner hole side layer is in the radial direction in a part or all of the region of the tubular refractory structure. In a continuous casting nozzle that is larger than the thermal expansion of the outer refractory outer layer,
Between the inner hole side layer and the outer peripheral side layer, an intermediate layer having a contractibility exists as a multi-layer structure integrated at the same time during molding,
The adhesive strength in a non-oxidizing atmosphere at 1000 ° C. between the intermediate layer and the inner hole side layer and the outer peripheral side layer adjacent to the intermediate layer is 0.01 MPa or more and 1.5 MPa or less,
And,
A continuous casting nozzle characterized in that the compressible rate K (%) of the intermediate layer in a non-oxidizing atmosphere at 1000 ° C. under a pressure of 2.5 MPa satisfies the following formula 1.
K ≧ [(Di × αi−Do × αo) / (2 × Tm)] Equation 1
Di: outer diameter of inner hole side layer (mm)
Do: Inner diameter of outer peripheral layer (mm)
Tm: Initial thickness of the intermediate layer at room temperature (mm)
αi: Maximum thermal expansion coefficient (%) of the refractory material on the inner hole side layer in the range from room temperature to 1500 ° C.
αo: Thermal expansion coefficient (%) at the temperature at the start of steel passing of the refractory on the outer side layer   The intermediate layer includes expanded graphite particles expanded after heat treatment in a non-oxidizing atmosphere at 600 ° C. or higher (hereinafter “expanded expanded graphite particles” is referred to as “expanded graphite particles”). The nozzle for continuous casting according to claim 1.   The intermediate layer contains a total of 16 mass% (including 100 mass%) of carbon components (excluding compounds with other components) after heat treatment in a non-oxidizing atmosphere at 1000 ° C. The nozzle for continuous casting according to claim 1 or claim 2.   After the heat treatment in a non-oxidizing atmosphere at 1000 ° C., the intermediate layer contains a total of 16% by mass of carbon components (excluding compounds with other components), and the balance other than the carbon components is oxides and carbides. The continuous casting nozzle according to claim 1, wherein the nozzle is a refractory raw material composed of at least one component selected from the group consisting of metal, nitride, and metal. It consists of a tubular refractory structure having an inner hole through which the molten metal passes in the axial direction, and part or all of the region in order from the inner hole surface to the outer side in the radial direction, the inner hole side, the intermediate layer, and the outer periphery A method for producing a continuous casting nozzle comprising a side layer,
As an intermediate soil for the intermediate layer, it contains 5% by mass to 45% by mass of unexpanded expandable graphite particles, 55% by mass to 95% by mass of combustible particles, and an organic binder is added to the intermediate layer. The ratio of the carbon component of the organic binder only (excluding compounds with other components) to the entire refractory for the intermediate layer after heat-treating the refractory for use in a non-oxidizing atmosphere at 1000 ° C. is 2. Preparing an earth soil added to the total of the unexpanded expandable graphite particles and combustible particles so as to be 5% by mass or more and 15% by mass or less;
This intermediate layer soil is molded together with the inner hole side layer soil and the outer layer side layer soil by simultaneous and simultaneous pressing with a CIP device,
By heat-treating the obtained molded body at 600 ° C. or higher and 1300 ° C. or lower, combustibles in the molded body for the intermediate layer disappeared to form a space. A method for producing a nozzle for continuous casting, comprising the step of expanding unexpanded expansive graphite in the green body and filling the space with expanded expanded graphite. It consists of a tubular refractory structure having an inner hole through which the molten metal passes in the axial direction, and part or all of the region in order from the inner hole surface to the outer side in the radial direction, the inner hole side, the intermediate layer, and the outer periphery A method for producing a continuous casting nozzle comprising a side layer,
As the soil for the intermediate layer, the unexpanded expandable graphite particles are 5% by mass or more and 45% by mass or less, the combustible particles are 55% by mass or more and 95% by mass or less, and oxides, carbides, nitrides, and metals. The organic binder comprising a total of 40% by mass or less of refractory raw materials composed of one or more components, and the organic binder after heat-treating the refractory for the intermediate layer in a non-oxidizing atmosphere at 1000 ° C. The unexpanded expandable graphite particles so that the ratio of only carbon components (excluding compounds with other components) to the entire refractory for the intermediate layer is 2.5% by mass or more and 15% by mass or less. Prepare an earth soil added to the flammable particles and the total of the refractory raw materials composed of one or more of oxide, carbide, nitride and metal,
This intermediate layer soil is molded together with the inner hole side layer soil and the outer layer side layer soil by simultaneous and simultaneous pressing with a CIP device,
By heat-treating the obtained molded body at 600 ° C. or higher and 1300 ° C. or lower, combustibles in the molded body for the intermediate layer disappeared to form a space. A method for producing a nozzle for continuous casting, comprising the step of expanding unexpanded expansive graphite in the green body and filling the space with expanded expanded graphite.

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