JP5134464B2 - Refractories for nozzles used for continuous casting and nozzles for continuous casting - Google Patents

Description

  The present invention relates to a continuous casting nozzle in which an inner hole side layer having higher thermal expansion than an outer peripheral side layer is disposed on an inner hole surface with which molten steel contacts.

  In the present invention, the “inner hole side layer” is present on the inner hole side of 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 the case where the inner hole side layer is composed of 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.

  In the present invention, the “peripheral layer” is a general term for the 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 In this case, the coefficient of thermal expansion is the minimum value of any one of the outer peripheral layers.

  Long nozzles that discharge molten steel from a ladle to a tundish, immersion nozzles that inject molten steel from a tundish into a continuous casting mold (hereinafter collectively referred to as “nozzles for continuous casting”), etc. A tubular refractory having an inner hole through which a high-temperature object stays or passes has a temperature gradient between the inner hole side and the 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 temperature gradients cause stress distortion inside the refractory regardless of whether the refractory is a single layer or multiple layers, and cause damage such as external cracks in the tubular refractory. It is one. The greater the temperature gradient and the greater the coefficient of thermal expansion of the inner hole side layer than the coefficient of thermal expansion of the outer peripheral side layer, the greater the thermal stress and the higher the risk of destruction of the outer peripheral side layer.

  As a general countermeasure against destruction caused by this temperature gradient (thermal stress), for example, a refractory constituting a continuous casting nozzle contains a large amount of graphite, or fused silica with a small thermal expansion amount is added or increased. There is a reduction in thermal stress due to high thermal conductivity, low expansion, low elastic modulus and the like. However, increasing the amount of graphite and fused silica, on the other hand, reduces oxidation resistance and increases reactivity with molten steel components, and thus has a detrimental effect on wear resistance, corrosion resistance, etc., particularly the durability of the inner hole side layer. .

  In addition, since the molten steel flow passes through the inner hole surface of the continuous casting nozzle while violently colliding, the vicinity of the inner hole surface is particularly worn by molten metal and non-metallic inclusions in the molten steel, oxidizing components in the molten steel, etc. Damages such as weakening and loss of structure due to corrosion, reaction melting loss with FeO and other components in molten steel are large.

  In recent years, nonmetallic inclusions in molten steel such as alumina have increased, and the continuous casting nozzle has also been found to have inclusions centering on alumina or clogging of the inner hole on the inner hole surface of the continuous casting nozzle. It has become one of the major factors that determine the lifespan.

  Under such circumstances, demands for high durability and safety (stable casting) of nozzles for continuous casting are increasing.

  In order to meet these demands, a refractory material having 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. The life of the continuous casting nozzle has been extended by disposing a refractory material having excellent wear resistance and corrosion resistance on the inner hole side layer having the inner hole surface in contact with the flow.

  In particular, various functions have been promoted for the inner-hole side layer. Recently, a material with a low carbon content, a material that does not contain graphite at all, and a component that has excellent wear resistance and erosion resistance, such as basicity. It is not uncommon to line a material containing ingredients on the inner hole surface. Furthermore, in order to reduce or prevent the adhesion and clogging phenomenon of alumina component etc. to the inner surface of the immersion nozzle, the immersion nozzle is equipped with a refractory layer containing a CaO component highly reactive with the alumina component on the inner surface of the immersion nozzle. Nozzle applications are being promoted.

  Such a high-performance refractory has a small content of graphite or the like having a large function of relaxing thermal expansion and contains a large amount of refractory aggregate having a high thermal expansion property. The difference in thermal expansion between the inner hole side layer and the outer peripheral side layer is also due to the increase in thermal gradient due to the increase in the thermal conductivity relative to the outer peripheral side layer of the inner hole side layer due to the reduction of the carbon content. And the thermal stress caused by it tends to increase more and more, the risk of destruction of the continuous casting nozzle, especially the outer peripheral layer, is further increased.

  As an attempt to prevent destruction of such a highly inflatable inner hole side layer due to thermal stress, for example, Patent Document 1 discloses a nozzle for continuous casting in which a refractory sleeve containing 20 mass% or more of CaO is incorporated. In addition, a fire-resistant bone is applied to the outer peripheral surface of the sleeve or a part or the whole of the wall surface of the body inner hole of the portion to which the sleeve is mounted, or a joint formed between the inserted sleeve and the wall surface of the body inner hole. The joint structure of the refractory sleeve for the inner hole of the nozzle for continuous casting in which the porosity of the dried joint joint adhesive is adjusted to 15 to 90% by applying an adhesive mixed with a binder and a binder is shown. . In addition, it has been shown that the porosity of the joint adhesive is adjusted by increasing or decreasing the solvent and binder constituting the adhesive or changing the filling amount. This is to obtain the stress relaxation ability by the porosity of the mortar, that is, the space in the mortar structure, the degree of which is to increase or decrease or change the filling amount of the solvent and binder constituting the mortar (adhesive). It is something to be adjusted with.

  However, since a large amount of liquid (solvent and binder) is required to obtain a high stress relaxation capability with such an adjustment method, there is a negative effect such that fluidity occurs in the mortar and the shape retention is significantly reduced. It is difficult to ensure the necessary thickness of the mortar layer and the filling layer. Specifically, in the operation of installing the inner hole side layer with such high fluidity or low shape retention mortar on the continuous casting nozzle body which is the outer peripheral side layer, the inner hole side layer is biased and the mortar layer In many cases, there is a portion with little thickness or an excessively large portion, or a large number of space portions. As a result, the stress relaxation function, the function of suppressing molten steel and other intruders, etc. cannot be ensured, and in particular, the outer peripheral layer is broken and the inner hole side layer is dropped.

  Even if the inner hole side layer can be fixed to the outer peripheral side layer (the main body of the nozzle for continuous casting) in a predetermined arrangement with such a mortar layer, the mortar layer inevitably has a density. Since the structure is low and the structure is weak, the structure is weak and low in strength. When relieving stress during the heat, the structure can be destroyed by weak external forces such as when handling the nozzle. It becomes difficult to maintain. For this reason, there exists a problem of becoming easy to cause peeling, a shift | offset | difference, etc. of an inner-hole side layer.

  Furthermore, since such a mortar layer has a high porosity and large pores in the structure are continuously present, molten steel and slag are transferred to the mortar layer through the pores (including fractured and expanded pores) as a route. There are problems such as penetration of components and the like, and mortar layer erosion and destruction.

  In addition, in mortar construction, a large amount of liquid is contained in order to obtain workability. Therefore, the liquid is absorbed into the refractory to be bonded, and the solid content concentration of the filled mortar is likely to change. This is because the shrinkage rate and adhesive strength of the mortar vary from site to site because the solvent in the mortar that gives plasticity and bonding properties is absorbed by contact with adjacent refractory materials with different apparent porosity. This means that the contractibility and adhesiveness are not stable depending on the adjacent material and mortar joint thickness. Furthermore, it tends to cause problems such as shrinkage and cracking of the mortar layer itself during absorption and drying processes, and voids and peeling between the refractory and the target refractory. Further, when the liquid is reduced, aggregate fine particles are aggregated with each other, and cracks and peeling are likely to occur in the mortar layer, so that problems are likely to occur in terms of adhesion.

  Further, for example, in Patent Document 2, a refractory layer that does not contain carbon only in the inner hole side layer, that is, has a high thermal expansion property and high corrosion resistance, is disposed, and the other outer peripheral side layer contains carbon. It has a two-layer structure in which a refractory layer having excellent ring properties is arranged, and a combustible material such as polypropylene and nylon is set and fired between the layers, and the formed separation layer is at least 80% of the contact surface between the refractory layers. The casting nozzle in which the inner hole side layer and the outer peripheral side layer are separated from each other by this separation layer is disclosed.

  However, in the structure of this patent document 2, it has an adhesion part in less than 20% between an inner-hole side layer and an outer peripheral side layer. Even if it is a slight adhesion portion, the cracking stress is transmitted from the inner hole side layer to the outer circumference side layer through this adhesion portion, and therefore, it becomes a starting point of the cracking phenomenon. Further, when the bonded portion is 0%, a basic problem that the inner hole side layer cannot be held as a structure occurs. Furthermore, in a joint of a so-called space such as the separation layer of Patent Document 2, the molten steel easily enters the joint, and the refractory is caused by solidification shrinkage of the molten steel and expansion of the steel during heating when subjected to a temperature change. There arises a problem that a crack occurs or the inner hole side layer is peeled off because the inner hole side layer is not bonded to the outer peripheral side layer.

In this way, the stress relieving layer of the continuous casting nozzle with a highly expanded inner hole side layer has a function to relieve stress due to thermal expansion from the inner hole side layer, and suppresses penetration of molten steel and slag components. Such large pores do not exist continuously, and have the properties and shape retaining properties that can obtain the necessary thickness and packed structure in installation work, and do not lead to stress due to thermal expansion of the inner hole side layer It must be strong enough not to break depending on the external force, and it must have a support function that prevents the inner hole side layer from peeling off from the outer peripheral side layer, but a mortar layer that combines these functions has not yet been obtained. .
International Publication No. 03/086864 Pamphlet Japanese Patent Laid-Open No. 7-232249

  An object of the present invention is to provide a continuous casting nozzle in which a highly functional layer such as high corrosion resistance and high adhesion prevention is arranged on the inner hole side to improve durability, and the inner hole side layer and the outer peripheral side which is a main body material While preventing the outer side layer from being cracked due to the difference in thermal expansion with the layer, the inner hole side layer has a property that can be fixed to the outer side layer (main body of the nozzle for continuous casting) in a predetermined arrangement, To provide a refractory material (mortar) for an intermediate layer of a continuous casting nozzle having a function of preventing peeling of an inner hole side layer during casting, and a continuous casting nozzle using the refractory material for the intermediate layer. is there.

The present invention
(1) 10% by volume or more and 75% by volume or less of a hollow refractory aggregate that satisfies a ratio of the average radius R of the grains and the average wall thickness t of the grains of R / t ≧ 10;
As a proportion of the total amount of the remainder other than the hollow refractory aggregate, one or more of single metals or alloys of Al, Si, Mg (hereinafter referred to as “specific metals”) are converted into only those metal components. Refractories for the intermediate layer of the nozzle for continuous casting containing 0.5% by mass to 15% by mass in total and 2% by mass to 99.5% by mass of carbon in total (Claim 1),
(2) The hollow refractory aggregate contains a glassy structure containing 70 mass% or more of SiO ₂ and 1 to 10 mass% in total of alkali metal oxide and alkaline earth metal oxide. The refractory for the intermediate layer of the continuous casting nozzle according to Item 1 (Claim 2),
(3) a refractory used for a continuous casting nozzle in a hot non-oxidizing atmosphere having a compressibility of 10% to 80% under pressure of 2.5 MPa and 1000 ° C. to 1500 ° C. The refractory for the intermediate layer of the continuous casting nozzle according to claim 1 or 2 having an adhesive strength of 0.01 MPa to 1.5 MPa (Claim 3),
(4) The whole or part of the inner hole surface with which the molten steel contacts has a multi-layer structure of an inner hole side layer, an intermediate layer, and an outer peripheral side layer in order from the inner hole surface, and the inner hole side layer In the continuous casting nozzle, the thermal expansion is greater than the thermal expansion of the outer peripheral side layer at a position corresponding to the inner hole side layer.
The said intermediate | middle layer consists of the refractory material in any one of Claims 1-3, and satisfy | fills following Formula 1, The nozzle for continuous casting characterized by the above-mentioned.
K ≧ [(Di × αi−Do × αo) / (2 × Tm)] × 100 Equation 1
here,
K is the shrinkage ratio of the intermediate layer (%)
Di is the outer diameter of the inner hole side layer (mm)
Do is the inner diameter of the outer peripheral layer (mm)
Tm is the (initial) thickness of the intermediate layer at room temperature (mm)
αi is the maximum coefficient of thermal expansion (%) in the range from room temperature to 1500 ° C of the refractory on the inner hole side layer
αo is the coefficient of thermal expansion (%) at the temperature at the start of steel passing of the refractories on the outer layer
(Claim 4)
It is.

  Details will be described below.

  The failure of the continuous casting nozzle due to cracking or splitting of the outer peripheral layer by the inner hole side layer is caused when the thermal expansion of the inner hole side layer is larger than the thermal expansion of the outer peripheral side layer, particularly the refractory of the inner hole side layer. This is noticeably generated when the thermal expansion characteristic (synonymous with the coefficient of linear expansion associated with temperature rise in the present invention) is larger than the thermal expansion characteristic of the refractory on the outer peripheral side layer.

  The stress due to the thermal expansion of the inner hole side layer acts as a radial compressive stress in the horizontal section of the continuous casting nozzle, and the continuous casting nozzle also has an outer peripheral side layer at the end in the long side axial direction. In the case of the structure, the axial compressive stress also acts on the outer peripheral layer. 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, exceeding the tensile strength of the outer peripheral layer. In the former case, cracks in the axial (longitudinal) direction occur, and in the latter case, horizontal (lateral) direction cracks are generated, and the outer peripheral layer is damaged.

  As a means for imparting a function to relieve stress between the inner hole side layer and the outer peripheral side layer having such a relationship, in the present invention, at least after the preheating is finished, at least the start of passing the molten steel (in the present invention The start of casting in the submerged nozzle and the start of pouring of molten steel into the tundish of the long nozzle are synonymous. The same shall apply hereinafter.) An intermediate layer having a contractibility is installed at the time.

  By installing such an 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 can reduce the stress due to expansion of the inner hole side layer by reducing the thickness in the radial direction or the axial direction according to the compressive stress, in other words, by reducing its volume. It becomes. In the present invention, such a property that the thickness and volume can be reduced is referred to as contractibility.

  In the present invention, the contractibility of the refractory constituting the intermediate layer is obtained mainly by the hollow refractory aggregate which is one of the constituent materials of the refractory.

  This hollow refractory aggregate provides shrinkability, and the main mechanisms that relieve stress due to thermal expansion are the following two points.

(1) The hollow refractory aggregate is pressurized with a stress greater than its breaking strength due to thermal expansion of the inner hole side layer, the wall surface of the hollow refractory aggregate is destroyed and the volume is reduced, and the space volume generated by the destruction is reduced. It becomes an absorption margin for thermal expansion of the inner hole side layer. This process occurs mainly when a load is applied before the softening of the hollow aggregate particles.

(2) In a high temperature range exceeding 1000 ° C., the wall of the hollow refractory aggregate softens (the degree of softening varies depending on the temperature), and when the softened hollow refractory aggregate is pressurized, the volume is easily deformed. The space volume generated by the reduction and the softening deformation to the reduction serves as an absorption margin for the thermal expansion of the inner hole side layer.

  The shrinkable target range to be obtained by the intermediate layer will be described below.

In the case of a 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 when a pressure of several MPa is applied to the inner wall surface of the outer peripheral side layer Break. For example, a refractory material having an outer peripheral side layer of Al ₂ O ₃ -graphite material having a maximum tensile strength of 6 MPa and having a general cylindrical shape of a nozzle for continuous casting and a practically minimum radial structure (outer periphery) In the case of the inner diameter of the side layer is 80 mm and the outer diameter of the outer layer is 135 mm, if pressure is applied from the inner wall surface of the pipe, it will break if a pressure of about 2.5 MPa is applied to the inner wall surface by calculation from the equation of the wall pressure cylinder. Will come.

  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)] × 100 Equation 1
here,
K is the shrinkage ratio of the intermediate layer (%)
Di is the outer diameter of the inner hole side layer (mm)
Do is the inner diameter of the outer peripheral layer (mm)
Tm is the (initial) thickness of the intermediate layer at room temperature (mm)
αi is the maximum coefficient of thermal expansion (%) in the range from room temperature to 1500 ° C of the refractory on the inner hole side layer
αo is the coefficient of thermal expansion (%) at the temperature at the start of steel passing of the refractories on the outer 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 (vertical 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. In addition, the measurement of the thermal expansion coefficient accompanying a temperature rise can be performed by the method (however, in non-oxidizing atmosphere) according to JISR2207-1 or this.

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 rate of the refractory for 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%.

  Here, the lower limit value of the shrinkable rate can be based on a measured value at 1000 ° C., and the upper limit value can be based on a measured value at 1500 ° C. (both in a non-oxidizing atmosphere). The standard of the lower limit of the shrinkable rate can be 1000 ° C. At 1000 ° C., the shrinkability of the refractory including the hollow refractory aggregate is almost caused by the destruction of the hollow refractory aggregate (strictly speaking, the refractory The shrinkage characteristics of the matrix structure are also slightly added), and the characteristics of this destruction are almost the same in the temperature range from room temperature to about 1000 ° C., and the volatile components in the binder component are sufficiently scattered, so that the carbonaceous bond structure is Completion of the connective structure that forms the basis of the matrix of the refractory is considered to indicate that the contractibility is almost the lower limit, so that evaluation with little variation is possible, and 1000 ° C. In the high temperature range from 1500 to 1500 ° C. (molten steel temperature), the softening characteristics of the hollow refractory aggregate are added to the destruction of the hollow refractory aggregate, which tends to be higher than the contractibility at 1000 ° C. The reason why the upper limit of the shrinkable ratio can be set to 1500 ° C. is that the temperature of the intermediate layer is about 1500 ° C. with respect to the temperature of the molten steel whose inner hole surface is the maximum temperature.

  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 with 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 off 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.

  In the present invention, the contractibility for stress relaxation can be obtained mainly by the hollow refractory aggregate in the intermediate layer as described above. The size of the contractibility is substantially equal to the volume ratio of the hollow refractory aggregate in the refractory for the intermediate layer. That is, when the intermediate layer contains 10% by volume or more and 75% by volume or less of the hollow refractory aggregate, the shrinkable ratio can satisfy the requirement of 10% or more and 80% or less at 1000 ° C. The matrix portion other than the hollow refractory aggregate also has a slight contractibility, but by including 10% by volume or more and 75% by volume or less of the hollow refractory aggregate, there is no difference in the contractibility of the matrix portion. It becomes possible to obtain a stable design contractibility.

  Here, the volume% of the hollow refractory aggregate is the volume calculated from the average particle density and the weight of the hollow refractory aggregate (that is, the volume of the hollow refractory aggregate itself, the volume of closed pores in the aggregate, and the unevenness of the aggregate surface. The volume of the space of the part) divided by the sum of the volume occupied by the hollow refractory aggregate and the volume occupied by the remaining matrix part. The method for calculating the volume% of hollow refractory aggregate is the most accurate method based on the raw material density used during blending, but it is based on the two-dimensional information of the hollow refractory aggregate from micrographs. In addition, the numerical value of the volume fraction of the hollow refractory aggregate can be substituted by image analysis such as a line segment method.

  The hollow refractory aggregate used in the present invention has a space inside and an outer wall formed by a wall. The compressive strength is less than 1000 ° C. (it can be evaluated at room temperature since there is almost no change to room temperature). When the aggregate particle is compressed between two planes, Further, it is preferable to break at a set maximum pressure based on a continuous casting nozzle, that is, a compressive stress of 2.5 MPa or less.

In order to satisfy this pressure strength, the ratio (R / t) of the average radius R of the hollow refractory aggregate to the average wall thickness t (R / t) needs to be 10 or more. When R / t is less than 10, the fracture rate under a pressure of 2.5 MPa is small, and the necessary contractible rate may not be ensured.
The R / t is preferably 60 or less. If it exceeds 60, the hollow refractory aggregate may be destroyed by the mechanical impact such as the handling of the nozzle for continuous casting in which the intermediate layer of the present invention is installed or the stability of the intermediate layer may be impaired. This is because it becomes larger.

  Here, the average radius means a value obtained by simply averaging the maximum dimension and the minimum dimension of the cross section near the center of the projection or the center of the hollow refractory aggregate particles, or a weighted average value of arbitrary plural points.

  The size of the hollow refractory aggregate satisfying the above R / t ratio (average radius R of the grains) is also distributed uniformly in the intermediate layer to make the contractible behavior in the intermediate layer uniform. It is better to be fine. The upper limit of the size of such a hollow refractory aggregate particle is a relative value that varies depending on the thickness of the layer (intermediate layer) of the refractory to be installed, its installation (construction) method, and the like. That is not appropriate. However, considering the industrial thickness of the continuous casting nozzle to which the refractory of the present invention is applied, considering the thickness of the intermediate layer, the lower limit thickness of the intermediate layer is about 1 mm (generally during installation) In consideration of the workability, quality, etc., as well as the rational structure of the nozzle for continuous casting, etc., it is about several millimeters. It is difficult to uniformly disperse the hollow refractory aggregate in the layer having such a thickness as the diameter increases. For example, when filling a refractory material as an intermediate layer between the inner hole side layer and the outer peripheral side layer (filling by a method similar to joint mortar or pouring), coarse hollow refractory aggregate particles are From the time of construction, segregation tends to occur and segregation tends to occur. Furthermore, the larger the average radius R, the easier it is to crack. As a result, the contractibility of each part in the intermediate layer also varies. For this reason, the maximum radius of the hollow refractory aggregate particles is preferably 250 μm or less.

  The minimum radius of the hollow refractory aggregate is preferably 2.5 μm or more. When the minimum radius is less than 2.5 μm, it is preferable in terms of uniformity, but the pressure strength tends to be high, and the ratio of not breaking at a compressive stress of 2.5 MPa or less increases, and the shrinkable amount tends to decrease. This is not preferable.

  In the present invention, the maximum radius means that one side of the mesh passes through a mesh having a set radius particle diameter, or is classified by a method corresponding thereto, and the minimum radius is , One in which one side of the mesh does not pass through a mesh having a diameter of a set radius particle, or one classified by a method equivalent thereto.

  Moreover, it is preferable that the outer shape of the hollow refractory aggregate is spherical or rounded. Since the hollow refractory aggregate is spherical or rounded, the aggregate particles are in point contact with each other, and the stress is less variable than in the case of a wide contact surface (here 2.5 MPa or less) The wall of the hollow refractory aggregate breaks down, and it is easy to obtain stable pressure resistance. Also, when the mortar-shaped intermediate layer is filled or applied in the gap between the inner hole side layer and the outer peripheral side layer (continuous casting nozzle body), the fluidity of the intermediate layer in the gap is As a result, it is not necessary to use an excessive amount of solution, and segregation can be reduced. When using a large amount of a liquid containing a large amount of volatile components for the purpose of providing fluidity necessary to obtain workability during filling, there is a risk of lowering the adhesion and strength of the refractory in the intermediate layer. .

As such a hollow refractory aggregate, a hollow refractory aggregate containing vitreous material known by a name such as a glass balloon, a silica balloon, and a shirasu balloon is particularly preferable. Furthermore, the chemical composition of the hollow refractory aggregate containing the vitreous material is a vitreous material containing 70% by mass or more of SiO ₂ and 1% by mass or more and 10% by mass or less of alkali metal oxide and alkaline earth metal oxide in total. In which the balance (parts other than SiO ₂ , alkali metal and alkaline earth metal oxides) is composed of a neutral oxide or an acidic oxide component other than SiO ₂ , specifically the balance The aluminosilicate system is the best, which consists of Al ₂ O ₃ .

In such a composition, especially an aluminosilicate system with the balance being Al ₂ O ₃ , the softening point is 1000 to 1400 ° C. (where “softening” is outside of fracture under pressure of 2.5 MPa or less) This is a state in which the shape is deformed.), And the intermediate layer is liable to be softened and deformed in a high temperature range, so that the amount of heat shrinkage is increased.

  Further, such a hollow refractory aggregate exhibits a contractibility due to brittle fracture at a pressure of 2.5 MPa or less in a low temperature range before softening, that is, less than about 1000 ° C., but alkali metal oxides and alkaline earth metals. By making a glassy composition containing 1% by mass or more and 10% by mass or less in total, it becomes easy to soften and deform in a high temperature range of about 1000 ° C. to 1500 ° C. (molten steel temperature), thereby reducing its volume. Thus, it can contribute to the development of stress absorption function and hot strength.

When SiO ₂ is less than 70% by mass, the total of alkali metal oxides and alkaline earth metal oxides is more than 10% by mass, or when SiO ₂ is 70% by mass or more, alkali metal oxides and alkaline earth metal oxides When the total amount is more than 10% by mass, a problem in producing a hollow raw material arises from the viscosity of the molten glass, or a problem occurs in the adhesive force for holding the inner hole side layer because the high temperature viscosity is low. . On the other hand, when SiO ₂ is less than 70% by mass and the total amount of alkali metal oxides is less than 1% by mass, or when SiO ₂ is 70% by mass or more and the total amount of alkali metal oxides and alkaline earth metal oxides is 1% by mass. If it is less than%, the viscosity of the glass composition tends to be too high, causing problems in the production of hollow raw materials, softening deformation behavior at high temperatures, and lowering the adhesive strength to retain the inner hole side refractory layer There is a problem to do.

  In specifying the composition of the hollow refractory aggregate in the present invention, volatile matter and combustible materials in a non-oxidizing atmosphere are not included. Specifically, a sample after heat treatment in a non-oxidizing atmosphere of about 600 ° C. or higher is used as a reference.

  Such hollow refractory aggregates exist as aggregates having a volume in the refractory structure before the volume is reduced by breaking or softening due to stress. Compared to the above, it is possible to significantly reduce the expression and maintenance of high strength as an intermediate layer, a high stress dispersion function, and the intrusion or passage of fluid such as molten metal or air from the outside. That is, it can also contribute to the stability of the layer itself described later, the stability of the layer structure of the nozzle for continuous casting, and the like.

  Such an intermediate layer should not cause misalignment, delamination, breakage, etc. of the inner hole side layer due to the external force received at each stage of conveying and installing the continuous casting nozzle, preheating and steel passing. is necessary.

  A mortar that simply has a large amount of space in the matrix structure of the refractory destroys the structure after shrinkage, causing weakening of the intermediate layer itself and a decrease in adhesive strength, leading to the collapse of the layer itself. . As a result, the risk of causing peeling or destruction of the inner hole side layer, intrusion of molten steel or the like between the layers becomes extremely high.

  It has been found that many troubles related to the inner hole side layer during casting were caused by the lack of adhesion of such an intermediate layer. Therefore, the inner hole side layer is kept in contact with the outer peripheral side layer while maintaining a certain strength through the intermediate layer during passage of the molten steel at a high temperature, particularly after the intermediate layer itself contracts due to thermal expansion of the inner hole side layer. It is necessary to maintain stable adhesiveness.

  As described above, the shrinkability of the refractory material of the intermediate layer of the present invention is realized mainly by the destruction, deformation, etc. of the hollow refractory aggregate, so that the matrix structure portion has higher strength and denseness than the mortar of the prior art. is there. Therefore, the weakening of the strength and the decrease in the adhesive strength are greatly suppressed.

  In addition, when a certain amount of stress is applied to the hollow refractory aggregate in the refractory structure of the intermediate layer, only the portion that requires the contractibility is destroyed, or the temperature is 1000 ° C. or higher and 1500 ° C. (molten steel temperature) or lower. The heat in a non-oxidizing atmosphere is deformed by softening, and the stress is relieved by them to prevent breakage of the continuous casting nozzle. At the same time, in a portion that does not require stress relaxation, the shape as an aggregate constituting the refractory skeleton of the intermediate layer is maintained.

  When the hollow refractory aggregate is broken or softened, the hollow refractory aggregate is deformed by breaking or deforming the wall of only the portion subjected to compressive stress from the surrounding matrix etc. toward the inside of the aggregate particle. Reduce the volume. In addition, the deformation due to the breakage or softening of the hollow refractory aggregate does not cause a large local deformation in the matrix structure because small particles of the hollow refractory aggregate are dispersed in the tissue, and the conventional high porosity. Unlike the mortar, the matrix structure is not destroyed to such an extent that the shape retention cannot be maintained.

  As a result, the hollow refractory aggregate remains in an adhesive state with the surrounding tissue, i.e., without generating voids in the surrounding tissue of the hollow refractory aggregate, and as an aggregate in an refractory structure without destruction. It can exist while maintaining the form. As a result, the intermediate layer hardly generates pores or spaces on the contact surface with the inner hole side layer and the outer peripheral side layer, while maintaining a sound dense structure and receiving an external force due to expansion of the inner hole side layer. The adhesion between the inner hole side layer and the outer peripheral side layer can always be maintained.

  However, it is preferable to provide more aggressive adhesion between the contact surfaces of the intermediate layer, the inner hole side layer, and the outer peripheral side layer.

  Therefore, in the present invention, as a means for enhancing the adhesiveness of the intermediate layer, the production of carbides and the like by the reaction of the metal at a high temperature is used. That is, the refractory for the intermediate layer of the present invention is a single metal or alloy of Al, Si, Mg as a balance other than the hollow refractory aggregate of 10 volume% or more and 75 volume% or less in the total amount of the balance. 1 type or multiple types (specific metal) of these is converted into only those metal components, and 0.5 mass% or more and 15 mass% or less in total, and carbon contains 2 mass% or more and 99.5 mass% or less. In specifying the composition of the hollow refractory aggregate in the present invention, volatile matter and combustible materials in a non-oxidizing atmosphere are not included. Specifically, a sample after heat treatment in a non-oxidizing atmosphere of about 600 ° C. to 800 ° C. is used as a reference.

  In this way, the specific metal and carbon are dispersed and coexisted in the remainder, so that in addition to carbon bonds derived from resins etc. used for the purpose of bonding between ordinary constituent materials of refractory or shape retention. Thus, it is possible to reinforce the adhesive strength of the intermediate layer and the bond strength of the refractory structure itself at a temperature of about 800 ° C. or higher, particularly about 1000 ° C. or higher.

  This action is considered as follows. Because these specific metals are exposed to a reducing atmosphere during casting due to coexistence with carbon, Mg-based gases and Al-based gases that are specific metal components evaporate, and some of them are metal carbides and metal oxides. As a result, it precipitates and adheres to pores or the like that are considered to have a relatively high oxygen partial pressure in the refractory structure (hereinafter simply referred to as “deposit”). In addition to the pores in the refractory, the specific metal is not included in the adjacent part of the refractory, particularly in the pores or voids in the vicinity of the contact interface between the molten steel containing the oxygen component and the intermediate layer. The oxides concentrate and deposit.

  The strength and adhesiveness of the intermediate layer as a refractory at a temperature lower than about 800 ° C. are primarily borne by carbon bonds derived from the resin or the like. At a high temperature of about 800 ° C. or higher, particularly about 1000 ° C. or higher, carbides formed by the reaction of the specific metal and carbon, and a connective structure formed by the oxide generated by the deposit, etc. are added to the carbon bonds derived from the resin, etc. To strengthen the bond.

  Thereby, the strength in the refractory structure of the intermediate layer is strengthened, and the adhesive force with the inner hole side layer and the outer peripheral side layer is also strengthened. Furthermore, the remarkable effect which prevents the permeation | transmission of the molten steel etc. in an intermediate | middle layer is acquired. (Hereafter, the connective tissue formed by these deposits is also referred to as “reconnective tissue”.)

  In the refractory material of the present invention, even if the hollow refractory aggregate is broken or deformed and reduced, the structure of the matrix structure other than the hollow refractory aggregate is not greatly damaged. In addition, even when partial damage occurs in the connective tissue and the matrix tissue, the recombination tissue is formed, and the connective tissue of the matrix of the intermediate layer itself is regenerated or strengthened. This also contributes to an improvement in adhesive strength between the layer and the outer peripheral side layer. As a result, the adhesive strength is improved without decreasing at a high temperature of about 1000 ° C. or higher.

  The effect of the present invention by such a hollow refractory aggregate, a specific metal and carbon, etc., can be provided with a large or large size space before the start of receiving steel, and only has bonds derived from the initial resin. This is an advantage that is decisively different from the prior art such as mortar in a form that promotes the destruction of the tissue with shrinkage.

  When the adhesiveness is quantitatively shown by the adhesive strength, the intermediate layer is 0.01 MPa or more between the inner hole side layer and the outer peripheral side layer and in a non-oxidizing atmosphere of 1000 ° C. or more and 1500 ° C. (molten steel temperature) or less. It is necessary to have an adhesive strength of 1.5 MPa or less. In addition, since the intermediate | middle layer itself has the intensity | strength more than the adhesive strength as a premise provided with adhesive strength, only adhesive strength is described below.

  When the adhesive strength is less than 0.01 MPa, the ability to hold the inner hole side layer is small, so local melting damage occurs in the inner hole side layer due to impact at the start of steel passing, changes in molten steel flow velocity, etc. If you do, there is a possibility of peeling off. Further, when the adhesive strength exceeds 1.5 MPa, the intermediate layer internal structure is in a high strength state at the same level as the adhesive strength, and the contractibility of the intermediate layer is impaired. It becomes easy to propagate to an outer peripheral side layer, without thermal expansion being relieved, and it becomes easy to cause the crack of an outer peripheral side layer especially.

  This adhesive strength can be evaluated as the compressive shear strength S. As shown in FIG. 2, the compressive shear strength S is obtained by placing a tubular sample having a three-layer structure in which an inner-hole side layer 2 is embedded in an outer peripheral side layer 3 (4) via an intermediate layer 1 on a table 8. After uniformly heating and holding in between, only the upper surface portion of the inner hole side layer 2 is compressed within a range of the moving speed of the crosshead 9 of 0.001 to 0.1 mm / sec, and the maximum load P (N) The displacement is measured and obtained by the following equation 4.

S (Pa) = P / A Formula 4
Here, A represents the adhesion area (m ² ) of the inner hole side layer to the intermediate layer.

  The shape of the sample is not particularly limited as long as it is tubular, and the sample can be cut out from an actual nozzle and measured. However, since the maximum load P increases as the adhesion area A increases, the sample height is preferably within 100 mm. The minimum temperature during measurement is 1000 ° C., and the atmosphere is a non-oxidizing atmosphere. 1000 ° C is a temperature at which the volatile components in the organic binder component are sufficiently scattered to complete the carbonaceous connective structure, exhibiting stable contractibility and adhesion state, and further, the reaction of specific metal to deposit, etc. starts. This is because of the temperature.

  If the content of the specific metal exceeds 15% by mass in the balance, the strength and adhesiveness of the intermediate layer will be strengthened, but on the other hand, the structure of the bonded portion by the metal carbide bond is as a refractory. Since the intermediate layer strength of the entire tissue is increased, the contractibility is impaired and it becomes difficult to obtain the necessary contractibility. In addition, the specific metal melts from the temperature raising process, and there is a risk that the specific metal may be washed away from the original location in the matrix, and it becomes difficult to obtain uniform strength and adhesive strength throughout the layer. Furthermore, partial collapse of the matrix structure, formation of gaps between layers, and the like are also caused, and intrusion of molten steel or the like easily occurs in a space or the like generated thereby. On the other hand, if the content of the specific metal is less than 0.5% in the remainder, the improvement of the strength of the intermediate layer itself and the improvement of the adhesive strength of 0.01 MPa or more in a non-oxidizing atmosphere at 1000 ° C. cannot be obtained or segregated. This is likely to cause destruction of the intermediate layer, peeling of the inner hole side layer, and intrusion of molten steel.

The specific metals are limited to Al, Si, and Mg components. Among these specific metal components, Al and Mg have a high affinity with oxygen, and trap oxygen and have corrosion resistance such as Al ₂ O ₃ and MgO. This is because Si forms a SiC having excellent strength and corrosion resistance by reacting with carbon in the intermediate layer in a high temperature range of about 1300 ° C. or higher. The purity of these specific metals is preferably as high as possible from the viewpoint of reactivity and dispersibility. However, the purity may be low as long as the reactivity is not impaired.

  The specific metal is preferably as small as possible in view of reactivity and dispersibility. However, the smaller the particle size, the greater the risk of handling and the more likely oxidation in the air occurs. Therefore, the lower limit value of the particle size is preferably about 5 μm, and the upper limit value is preferably about 300 μm. Since the surface area is suddenly increased at 20 μm or less, the reactivity is increased, and the dispersibility is further increased, 20 μm or less is more preferable.

  The carbon component for reacting with the specific metal needs to be 15% by mass or more and 99.5% by mass or less as a proportion of the total amount of the remaining part of the intermediate layer.

As the carbon source, it is possible to use various pitches, carbon black, graphite, carbon fibers, and the like, including thermosetting resins such as phenol resins that retain carbon at the time of temperature rise, and these plural types can also be combined. Among them, in order to increase the reactivity with a specific metal and to improve the uniformity, the carbon source includes carbon such as carbon black as small as possible, amorphous carbon derived from a connective tissue, etc. It is preferable that fine carbon ") be included.
For the purpose of imparting strength from room temperature to several hundreds of degrees Celsius, organic adhesives and resins such as vinyl acetate resins, epoxy resins, acrylic resins, and polyester resins can also be used.

  The refractory matrix structure of the intermediate layer includes the above-mentioned fine carbon, which is responsible for basic strength and adhesion, as well as graphite and carbon fibers that form a base material for forming a continuous connective structure and matrix structure skeleton. Etc. (hereinafter simply referred to as “skeleton base carbon”). In particular, graphite has a flat crystal shape in addition to its layered crystal structure, so it can obtain a flexible and continuous three-dimensional structure, and carbon fiber can also obtain a similar three-dimensional structure. Since it is possible, it is more preferable.

  By forming such a flexible and continuous three-dimensional structure in a matrix, it becomes possible to impart toughness to the connective structure in which carbides intervene after reacting with a specific metal. When the matrix is deformed or broken, the surrounding matrix can be prevented from collapsing, and the soundness of the layer can be further improved.

  The specific ratio of the fine carbon and the skeleton base carbon is the ratio of the 15% by mass or more and 99.5% by mass or less of the total carbon, and the effect of increasing the three-dimensional continuity with a large aspect ratio. The proportion of the skeleton base carbon such as graphite or carbon fiber is preferably 70% by mass to 95% by mass. If it is less than 70% by mass, the three-dimensional continuity may be lowered and flexibility may be impaired. On the other hand, if the amount is more than 95% by mass, local damage may occur due to the low adhesive strength.

As a method for supplementarily improving the corrosion resistance due to the deposit effect on the working surface of the specific metal by coexistence of the specific metal and carbon, there is a method of coexisting a refractory material having excellent corrosion resistance as the remaining component. However, when the refractory material composed of other components is included in the balance other than the specific metal and carbon, the components (hereinafter also simply referred to as “other components”) include the inner hole side layer and the outer peripheral side layer. Therefore, it is necessary to select a refractory aggregate mainly composed of components that do not cause a low melting phenomenon or a volatilization disappearance phenomenon at a casting temperature. When the intermediate layer generates a liquid phase by contact with the inner hole side layer or outer peripheral side layer at the casting temperature, the strength of the refractory is reduced to such an extent that the hot adhesive strength is reduced or the compressibility is impaired by excessive sintering. Is not preferable. In addition, since the inside of the refractory is exposed to a strong reducing atmosphere, for example, in a volatile component such as SiO ₂ component that does not form a stable mineral with other components, the loss of the carbon component is caused. Since the component itself volatilizes and disappears, it is not preferable.

The aggregates that can be selected include Al ₂ O ₃ , MgO, ZrO ₂ , Al ₂ O ₃ .MgO-based spinel, etc., so that the contact portion between the intermediate layer and the inner hole side layer does not generate a low-melt material. In addition, these components are appropriately selected according to the material of the inner hole side layer. For example, when the inner hole side layer is a refractory containing CaO, a MgO-quality refractory aggregate is suitable, and the inner hole side layer is mainly composed of Al ₂ O ₃ or MgO. Are preferably Al ₂ O ₃ , MgO, Al ₂ O ₃ —MgO-based spinel, and the like. Further, when the MgO purity of the refractory aggregate in such other components is 90% or more, it is also suitable for the case where the inner hole side layer is an Al ₂ O ₃ system or a ZrO ₂ system, Since it can respond | correspond widely to the component of various inner-hole side layers, it is preferable.

  The particle size of the refractory aggregate constituting such other components is 0.5 mm or less when the lower limit thickness of the intermediate layer is 1 mm in order to improve the dispersibility and the uniformity of the above-described functions in the intermediate layer. It is preferable that

  Here, the case where the corrosion resistance of the intermediate layer is required means that the molten steel or the like is prevented from coming into direct contact with the outer peripheral side layer which is inferior in corrosion resistance when a defect portion of the inner hole side layer occurs due to various actions during operation. This is to prevent corrosion and in such a case, the intermediate layer itself also has corrosion resistance, wear resistance, and the like.

  For continuous casting nozzles, fragile parts such as missing parts due to damage of the inner hole side layer itself, the boundary part between the inner hole side layer and the nozzle body (outer peripheral side layer), the gas pool part for gas blowing and the interlayer joint part In addition to the locally damaged parts, there are parts that are already directly exposed to the molten steel in the state of the continuous casting nozzle as a product in the processing step when manufacturing the continuous casting nozzle such as the discharge hole part of the immersion nozzle, for example. Or it may exist. 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.

  The refractory for the intermediate layer of the present invention has inner holes such as an immersion nozzle, an open nozzle, a ladle long nozzle, a sliding nozzle (hereinafter referred to as “SN”), an SN upper nozzle, and an SN lower nozzle (also referred to as a collector). Is suitable for a nozzle for continuous casting having a function and structure through which molten steel passes.

The material of the inner hole side layer of such a continuous casting nozzle does not need to be particularly limited, and the characteristics required for the continuous casting nozzle according to the operation of each continuous casting, specifically, Refractories containing Al ₂ O ₃ , MgO, ZrO ₂ , etc. having properties suitable for each purpose, such as wear resistance, corrosion resistance of the inner holes, and prevention of inclusions such as Al ₂ O _{3 in the} inner holes (It may contain graphite or other components) can be used as appropriate. Similarly, there is no need to limit the outer peripheral side layer as well, and since the outer peripheral side layer is usually a part constituting the main body of the continuous casting nozzle, a general Al ₂ O ₃ -graphite or mold powder part is used. In addition, a refractory containing high corrosion-resistant ZrO ₂ or the like may be used in part or in whole.

  The use of the refractory for the intermediate layer of the present invention is such that the thermal expansion coefficient of the refractory in the inner hole side layer is the refractory in the outer layer in the inner hole side layer and outer periphery side layer. It is suitable in the case of a combination larger than the thermal expansion coefficient. Even if the inner hole side layer and the outer peripheral side layer are the same material and have the same thermal expansion characteristics, the temperature gradient and the thermal shock are naturally large enough to destroy the continuous casting nozzles composed of these refractories. Can be used.

  When the thermal expansion of the inner hole side layer is larger than the thermal expansion of the outer peripheral side layer, the refractory of the present invention is particularly durable by disposing a high-functional layer such as high corrosion resistance and high adhesion prevention on the inner hole side. By applying to the intermediate layer of the continuous casting nozzle with increased, preventing cracking of the outer peripheral side layer due to the thermal expansion difference between the inner hole side layer and the outer peripheral side layer that is the body material, and It is possible to prevent peeling and destruction of the inner hole side layer during casting.

In particular, it is possible to obtain a stable adhesion by depositing a specific metal, and also to realize a dense and high-strength structure of the refractory of the intermediate layer itself. Can also be improved.
By using the multi-layered continuous casting nozzle to which the refractory material of the present invention is applied, the characteristics required for the continuous casting nozzle, specifically the hot water supply, according to the specific operating conditions of individual continuous casting. Various refractories with suitable properties for each purpose, such as improvement of wear resistance of parts, improvement of corrosion resistance of inner holes, prevention of inclusions such as Al ₂ O _{3 in} inner holes, etc. It can be used and the choice of materials and combinations thereof can be greatly expanded. As a result, it can contribute to extending the life of nozzles for continuous casting, improving the quality of steel, stable operation, and resource saving.

  First, a method for producing a refractory according to the present invention will be described.

  When the refractory material of the present invention itself includes a hollow refractory aggregate, carbon, a specific metal, and other constituents, the refractory material particles constituting the constituents are mixed, and the mixture includes phenol resin, vinyl acetate, etc. A binder having such a strength as to give a cohesiveness or adhesiveness between the grains by wetting the admixture, such as an organic resin, and retaining the shape as a molded product after curing. An appropriate amount necessary for molding and shape retention is added and kneaded to obtain a kneaded product. Next, the kneaded product is poured into a space provided in advance, filled and molded by an appropriate method such as blowing, and dried at an appropriate temperature of about 110 ° C. to 800 ° C. according to the properties of the binder, It can be obtained by heat treatment such as baking. Details will be described below.

  Oxidation of 10 to 75% by volume of hollow refractory aggregate and 25 to 90% by volume of carbonaceous particles derived from scaly graphite, earthy graphite, carbon black, pitch, resin, such as magnesia, zirconia, corundum particles, etc. Mix material and metal particles.

  The proportion of carbonaceous particles, oxide particles, and metal particles derived from scaly graphite, earthy graphite, carbon black, pitch, resin, etc. in the amount of 25 to 90% by volume in the total amount of portions other than the hollow refractory aggregate As a single metal or an alloy (specific metal) of Al, Si, Mg, converted into only those metal components, a total of 0.5 to 15% by mass, and 2% of carbon % And 99.5% by mass or less, and the remainder is blended so as to be composed of a refractory aggregate (including zero) other than the specific metal and carbon. The particle size of this raw material is such that the maximum particle size of the raw material particle size used is 0.5 mm or less in order to make the compressibility of the refractory in the intermediate layer more uniform and to make it a mortar with excellent coating workability. Is preferred.

  The amount of the hollow refractory aggregate is calculated from the relationship between the thermal expansion coefficient of the inner hole side layer and the outer peripheral side layer and the thickness of the refractory material of the intermediate layer, What is necessary is just to determine by adjusting the ratio of a hollow refractory aggregate and another structural raw material.

  The blend is wetted to give the mixture a cohesiveness or adhesion between grains, such as phenolic resin, vinyl acetate, and other organic resins. A binder having a strength sufficient to have a suitable amount for the molding is added in an appropriate amount, and they are kneaded using a mixer such as a mortar mixer to form a mortar shape. Obtain a blend. The amount of the phenolic resin and other organic resin used may be adjusted according to the required workability within a range of about 40 parts by mass or more and 90 parts by mass or less when the powder mixture is 100 parts by mass. .

Next, the mortar-like admixture is filled into a space previously provided between the inner hole side layer and the outer peripheral side layer by an appropriate method such as application, fitting, pouring, or blowing on one or both surfaces. Then, the inner hole side layer and the outer peripheral side layer are integrated. And shape retention ability and interlayer fixing ability are expressed by performing heat processing, such as drying and baking, at an appropriate temperature according to the properties of the binder, such as 110 ° C. or more and 600 ° C. or less.
Such an intermediate layer refractory is practically used mainly as a part of a continuous casting nozzle structure as described below as a manufacturing process of a continuous casting nozzle structure as described later, as a single unit continuous casting nozzle of a product. Get as a form. In addition, molding using molds, etc., firing in a dry or non-oxidizing atmosphere, forming as a part of any shape such as a cylinder, etc., and assembling and using as a part of a continuous casting nozzle Is also possible.

  Next, a continuous casting nozzle manufacturing method to which the refractory of the present invention is applied will be described.

Prepare a molded body to be an inner hole side layer that has been molded, heat-treated, and peripherally processed in advance as a single unit, and an outer peripheral side layer that will be a nozzle body for continuous casting that has been previously molded, heat-treated, and processed as a single unit. A spacer with a predetermined thickness is installed on the outer surface of the inner hole side layer so that a space with a predetermined intermediate layer thickness can be formed between the inner layer and the inner hole side layer, and the outer peripheral side through the mud-like intermediate layer kneaded material The inner hole side layer is inserted inside the layer to form a predetermined intermediate layer to obtain a nozzle having a multilayer structure. Details will be described below.

  The refractory material of the present invention applied to the intermediate layer has a mud-like indefinite shape that can be filled to fill a narrow space between the inner hole side layer and the outer peripheral side layer. In order to provide workability in the filling process, for example, a liquid resin is externally applied to 100 parts by mass of powder mixed with a hollow refractory aggregate, a carbon raw material as a solid, and a refractory material as another component. An amount of about 40 parts by weight to 90 parts by weight (determined in consideration of space size and construction workability) is added and kneaded.

  In this way, the refractory for the intermediate layer provided with workability is applied to the outer peripheral surface of the inner hole side layer in which the spacer is installed so that a space with a predetermined intermediate layer thickness can be formed, or the inner hole surface of the outer peripheral side layer. The inner hole side layer is inserted inside the outer peripheral side layer (the main body of the nozzle for continuous casting). The space between the outer peripheral surface of the inner hole side layer and the inner hole surface of the outer peripheral side layer is equal to the thickness of the refractory layer of the intermediate layer.

  In addition to such a method by coating, an intermediate layer refractory with improved fluidity, such as by increasing the liquid addition ratio, in a space of a predetermined thickness provided between the outer peripheral side layer and the inner hole side layer. It can also be filled by a method such as pouring.

  The continuous casting nozzle after being filled with the refractory for the intermediate layer is subjected to heat treatment such as drying and firing to cure the refractory for the intermediate layer and fix the inner hole side layer and the outer peripheral side layer. . This curing may be performed at an appropriate temperature according to the characteristics of the binder contained in the refractory material of the intermediate layer, which is about room temperature to 600 ° C. For example, when a vinyl type is used, it may be dried at about 150 ° C., and when a phenol resin is used, it is preferably 200 ° C. or higher. Further, after that, it may be fired in a non-oxidizing atmosphere of about 1000 to 1300 ° C., for example.

  In this way, a molded article of a continuous casting nozzle having the refractory of the present invention in the intermediate layer can be obtained.

  The hollow refractory aggregate used for the refractory for the intermediate layer of the present invention is not crushed by the external force during the installation work on the outer peripheral side layer of the inner hole side layer as described above. Therefore, the necessary contractibility is not impaired by excessively reducing the solvent or absorbing the solvent. Furthermore, since this hollow refractory aggregate is formed in a balloon shape, there are few edge parts like crushed grains and it has a rounded outer shape, which improves the fluidity of the refractory in the mud intermediate layer In other words, it is possible to obtain an effect, that is, to reduce the amount of liquid phase to form a dense matrix structure.

  However, in any method, if a pressure exceeding the strength of the hollow refractory aggregate is applied during molding or other construction, the hollow refractory aggregate is broken and the function of relaxing the stress is impaired. Therefore, general simultaneous and integral hydrostatic molding (CIP) and other various high pressures of continuous casting nozzles premised on pressurization far exceeding 2.5 MPa at which the hollow refractory aggregate breaks. It cannot be press-molded.

  In the above-mentioned manufacturing method, the refractory for the intermediate layer has the purpose of retaining the shape of the intermediate layer itself, imparting strength between room temperature and hot during use, and ensuring the moldability of the soil. If the inner hole side layer contains MgO-CaO, especially CaO that exists in a single form (not a solid solution or compound), the construction caused by the hydration of the CaO component therein In order to prevent the body from collapsing, it is necessary to use a material that does not contain moisture and that does not release moisture during the heating process. As a binder suitable for such conditions, non-aqueous phenol resins, furan resins, tars, melamine resins, epoxy resins, vinyl acetate resins using alcohol as a solvent, and the like can be used.

  Carbon derived from the binder and remaining at 600 ° C. or higher becomes a part of the composition as a carbon component of the refractory of the intermediate layer.

  The molded body of the nozzle for continuous casting after such processing as filling and heating can be processed in the same manner as the processing steps for a general continuous casting nozzle, such as the outer periphery and other molding processes, and the application of an antioxidant. it can.

  By the above manufacturing method, a continuous casting nozzle having an intermediate layer having a shrinkable structure and a continuous structure in which the inner hole side layer and the outer peripheral side layer are integrated can be obtained.

  FIG. 1 shows an immersion nozzle as an example of the continuous casting nozzle of the present invention. In FIG. 1, 1 is an intermediate layer made of a refractory for the intermediate layer of the present invention, 2 is an inner-hole side layer, 3 is an alumina-graphite layer that forms the main body of a continuous casting nozzle among the outer peripheral side layers, 4 Is a zirconia-graphite layer forming a powder part of a continuous casting nozzle in the outer peripheral side layer, 5 is an inner hole, 6 is a molten steel inflow hole, and 7 is a discharge hole.

  Examples are shown below.

<Example A>
In Example A, when an external force of 2.5 MPa was applied to the hollow refractory aggregate, the average radius R of the hollow refractory aggregate and the ratio of the average radius R to the average wall thickness t of the grain (R / t) is the result of an experiment investigating the effect of t) on the destruction.

  Table 1 shows the configuration and experimental results of each sample of Example A.

The sample was selected from those that are generally available on the market and dispersed in water, and then the floating particles were selected, classified, and dried at 110 ° C. The composition of the test sample, SiO ₂ of 70 wt% or more, alkali metal oxides and less than 10 mass% 1 mass% or more in total of alkaline earth metal oxides, _Al 2 _{O 3} of 5 to 20 mass% And a glassy structure.

  The size of the sample is 2.5 μm (preferred minimum radius), 250 μm (preferred maximum radius), and 35 μm between them, and each particle is divided into a group of a plurality of particle groups having different wall thicknesses. Classification was performed to obtain samples having different R / t ratios.

  As shown in FIG. 3, the test method is as follows. The sample 10 is filled into a cylindrical metal container 11 having an inner diameter of 60 mm so as to have an initial height of 10 mm, and a pressurizing machine (upper liner 12). And the lower liner 13) are pressurized to a static pressure of 2.5 MPa, and then the sample 10 in the container 11 is taken out, dispersed in 1 liter of water, floated, and settled. What separated and floated was collect | recovered, and the weight was measured after drying.

  The crushing rate (%) is obtained by subtracting the total weight of the floating portion from the total weight of the sample 8 initially filled in the cylindrical metal container 11 (hereinafter referred to as “initial total weight”). A value obtained by dividing the value by the above-mentioned initial total weight was displayed as a percentage.

  In this Example A, considering that the matrix portion also shows some contractibility, the crushing rate of the hollow refractory aggregate is 90% or more, and the requirement for obtaining the required contraction rate It was. Further, in this test method, the fragments of particles broken by pressurization are filled in the spaces between the particles, and the fragments perform a stress distribution function. It is considered that the particles are difficult to break, and some of them may remain without being broken. Therefore, particles having a crushing rate of 90% or more have the same or higher destruction characteristics in the refractory structure. Judgment can be made.

  In each sample in which the preferable minimum radius R was 2.5 μm and the preferable maximum radius R was 250 μm, the fracture rate was 90% or more when the R / t ratio was 10 or more.

<Example B>
Example B is a result of investigating the influence of the volume ratio of the hollow refractory aggregate in the refractory on the shrinkability and the adhesive strength, and the result of conducting a simulation test of molten steel casting by heating the inner hole It is.

  Table 2 shows the configuration of each sample of Example B and the experimental results.

  The hollow refractory aggregate is a powder having the same composition as that used in Example A, a hollow particle having an average radius R of 35 μm, a wall thickness of 1 μm, and a crushing rate of 99% at 2.5 MPa. The body (Example 3) was used. The composition of the remainder excluding the hollow refractory aggregate was the same in all examples.

The shrinkage rate was measured by the following method. Two test pieces for adhesion having a shape of φ20 × 50 mmL, Al ₂ O ₃ of about 75% by mass, and C of about 25% by mass are manufactured by the same manufacturing method (same molding pressure, The method shown in the means for solving the above-mentioned problems by placing each blended sample in a mortar shape between the planes of the two test specimens for adhesion to each other, by drying, firing, etc.) Then, a measurement sample was molded and dried. For this measurement sample, the contractibility at 1000 ° C. and 1500 ° C. (both in a nitrogen gas atmosphere) was measured.

The adhesion strength was measured by the following method. Al ₂ O ₃ is about 55% by mass, C is about 30% by mass, and SiO ₂ is about 14% by mass by the same manufacturing method (same molding pressure, drying, firing, etc.) as a normal continuous casting nozzle. A refractory material generally used for the body of a continuous casting nozzle and a cylinder corresponding to the outer peripheral side layer having an inner diameter of φ95 × 100 mmL are prepared, and MgO is about 49 mass%, CaO is 44 C mass%, and C is 4 A cylinder corresponding to the inner hole side layer having an outer diameter of φ90 × 100 mmL is made of dolomite refractory material of mass%, and each blended sample in the form of mortar is placed between these two cylinders with a thickness of 2.5 mm. The sample was dried and a ring-shaped sample for measurement was obtained. With respect to this ring-shaped measurement sample, the adhesive strength at 1000 ° C. and 1500 ° C. (both in a nitrogen gas atmosphere) was measured by the method described with reference to FIG.

The cylindrical sample for the inner hole heating test was produced by the following method. First, a cylindrical and tubular molded body was molded by CIP. The molded body was subjected to a drying process at 200 ° C. and a heat treatment in a non-oxidizing atmosphere at 1000 ° C., and a sleeve made of a dolomite carbon material having an outer diameter of 90 mm, an inner diameter of 70 mm, and a height of 750 mm was manufactured by outer peripheral processing. The thermal expansion amount of the material at 1500 ° C. was 1.32%. The sleeve _Al 2 _{O 3} is about 55 wt%, C is from about 30 wt%, the thermal expansion amount at SiO ₂ is about 14 wt% of _Al 2 _O 3 -SiO ₂ -C material (1500 ° C. 0.55 %) And a refractory for a mortar-shaped intermediate layer shown in Table 2 with a joint thickness of 2.5 mm inside a cylindrical refractory having a flange portion (inner diameter: 95 mm, outer diameter: 140 mm, height: 750 mm) The interior was evenly distributed through the objects. This refractory for the intermediate layer is composed of graphite fine powder, Al-Mg alloy powder, MgO fine powder, pitch powder, and hollow refractory aggregate (hollow glass aggregate) as a compressible source, and is a liquid phenolic resin Were used as a workability imparting agent and a binder. A 200 ° C. drying treatment was applied to obtain a cylindrical sample for heating the inner hole.

  The inner hole heating test was performed as follows. From the upper part of the flange part toward the lower part, a combustion gas of propane and oxygen was passed through the inner hole part, and rapid heating was performed from the inner hole part. The cylindrical sample was heated under the condition that the outer surface temperature at the center of the cylindrical sample reached 1400 ° C. in 1 hour and held at 1400 ° C. for 1 hour. Thereafter, the heating was stopped and the mixture was allowed to cool to 300 ° C. or lower. This heat treatment was repeated, and the states of the inner hole side layer and the outer peripheral side layer were observed.

  From the measurement results shown in Table 2, it can be seen that substantially the same shrinkage ratio as the volume ratio of the hollow refractory aggregate can be obtained. And it turns out that a hollow refractory aggregate is 10 volume% or more and 75 volume% or less, and a contractibility can satisfy 10% or more in 1000 degreeC, and 80% or less in 1500 degreeC. Also, it can be seen that the adhesive strength of the hollow refractory aggregate is 10 volume% or more and 75 volume% or less and can satisfy 0.1 MPa or more and 1.5 MPa or less.

  In the inner hole heating test, when the hollow refractory aggregate is less than 10% by volume (Comparative Examples 3 to 5), cracking occurs, and when the hollow refractory aggregate exceeds 75% by volume (Comparative Examples 6 and 7). The inner hole side layer loosened and tended to fall off.

<Example C>
In Example C, the effect of the ratio of the specific metal in the refractory material including the hollow refractory aggregate on the contractibility and the adhesive strength was investigated by experiment, and in each case, the molten steel by inner hole heating was used for each example. This is a result of comparison with a casting simulation test.

  Table 3 shows the configuration and experimental results of each sample of Example C.

  Hollow refractory aggregate particles having the same composition and particle size distribution as those used in Example B were used. The composition of the remainder other than the hollow refractory aggregate except for the specific metal was the same in all examples, and the amount of the specific metal was added to the composition.

  The measurement of the shrinkable ratio and the adhesive strength, and the simulation test of the casting of the molten steel by heating the inner hole were performed by the same method as in Example B.

  From the measurement results shown in Table 3, it can be seen that the adhesive strength of 0.01 MPa to 1.5 MPa can be satisfied when the content of the specific metal is in the range of 0.5 mass% to 15 mass%. If the content of the specific metal is less than 0.5% by mass, an adhesive strength of 0.01 MPa cannot be obtained at 1500 ° C., and if it exceeds 15% by mass, it exceeds 1.5 MPa at any temperature.

  In the inner hole heating test, good results were obtained when the content of the specific metal was in the range of 0.5% by mass or more and 15% by mass or less, and this tendency was mainly different from the range of the predetermined value of the adhesive strength. You can see that you are doing it.

<Example D>
In Example D, the effect of the proportion of carbon in the balance other than the hollow refractory aggregate on the compressibility and the adhesive strength was experimentally investigated, and a simulation test of molten steel casting by inner hole heating was performed. It is a result.

  Table 4 shows the configuration and experimental results of each sample of Example D.

  As the hollow refractory aggregate, the same composition and particle size distribution as those used in Examples B and C were used.

  In this example, the specific metal amount and the phenol resin solution (converted as C remaining after heat treatment in a non-oxidizing atmosphere at 1000 ° C.) are basically fixed (except for the case where the carbon amount is 99.5% by mass or more). The amount of carbon was changed by substituting the fine powder of MgO (MgO purity 95 mass% to 98 mass%, the same in other examples) with the fine graphite powder.

  The shrinkage ratio and adhesive strength measurement, and the simulation test of casting of molten steel by heating the inner hole were also performed by the same method as in Examples B and C.

  From the measurement results shown in Table 4, it can be seen that the adhesive strength of 0.01 MPa or more and 1.5 MPa or less can be satisfied when the carbon content in the balance is 2 mass% or more and 99.5 mass% or less.

  In Comparative Example 12 in which the carbon content is less than 2% by mass, an adhesive strength at 1500 ° C. of 0.01 MPa or more was not obtained, and in Comparative Example 13 in which no specific metal was contained, even if the amount of carbon was large. (100% by mass) Adhesive strength at 1500 ° C. of 0.01 MPa or more cannot be obtained.

  In the inner hole heating test, good results were obtained when the carbon content was in the range of 2% by mass or more and 99.5% by mass or less, and as in Example C, this tendency was mainly due to the adhesive strength. It can be seen that this is consistent with a predetermined value range.

It is an axial sectional view showing an immersion nozzle as an example of a continuous casting nozzle using the refractory for the intermediate layer of the present invention. It is an image figure of the axial direction cross section of the sample at the time of an adhesive strength test, and an apparatus. It is an image figure of the axial cross section of the sample and apparatus at the time of the destructive test of the hollow refractory aggregate in Example A.

Explanation of symbols

1 Intermediate layer (a layer made of a refractory for the intermediate layer of the present invention)
2 Inner hole side layer 3 Alumina-graphite layer forming the main body of the continuous casting nozzle in the outer peripheral side layer 4 Zirconia-graphite layer forming the powder part of the continuous casting nozzle in the outer peripheral side layer 5 Inner hole 6 Molten steel inflow hole 7 Discharge hole 8 units 9 Crosshead 10 Sample (hollow refractory aggregate)
11 Container 12 Upper liner (pressurizing jig by lowering)
13 Lower liner (Jig for pressurization by ascending)

Claims (4)

A hollow refractory aggregate containing 10% by volume or more and 75% by volume or less of hollow refractory aggregate satisfying a ratio of the average radius R of the grains and the average wall thickness t of the grains of R / t ≧ 10;
As a proportion of the total amount of the remainder other than the hollow refractory aggregate, one or more of single metals or alloys of Al, Si, Mg (hereinafter referred to as “specific metals”) are converted into only those metal components. A refractory for an intermediate layer of a continuous casting nozzle containing 0.5% by mass to 15% by mass in total and 2% by mass to 99.5% by mass of carbon. The hollow refractory aggregate is, SiO ₂ of 70 wt% or more, and in claim 1 comprising a tissue of the vitreous, including: 10 wt% or more 1 wt% of alkali metal oxides and alkaline earth metal oxides in total A refractory for the intermediate layer of the continuous casting nozzle described.   A refractory used for a continuous casting nozzle and 0.01 MPa in a non-oxidizing atmosphere having a compressibility of 10% to 80% under pressure of 2.5 MPa and 10% to 80%. The refractory for the intermediate layer of the continuous casting nozzle according to claim 1 or 2, which has an adhesive strength of 1.5 MPa or less. All or a part of the inner hole surface with which the molten steel contacts has a multi-layer structure of an inner hole side layer, an intermediate layer, and an outer peripheral side layer in order from the inner hole surface, and the thermal expansion of the inner hole side layer is In the continuous casting nozzle larger than the thermal expansion of the outer peripheral side layer at the position corresponding to the inner hole side layer,
The said intermediate | middle layer consists of the refractory material in any one of Claims 1-3, and satisfy | fills following Formula 1, The nozzle for continuous casting characterized by the above-mentioned.
K ≧ [(Di × αi−Do × αo) / (2 × Tm)] × 100 Equation 1
here,
K is the shrinkage ratio of the intermediate layer (%)
Di is the outer diameter of the inner hole side layer (mm)
Do is the inner diameter of the outer peripheral layer (mm)
Tm is the (initial) thickness of the intermediate layer at room temperature (mm)
αi is the maximum coefficient of thermal expansion (%) in the range from room temperature to 1500 ° C of the refractory on the inner hole side layer
αo is the coefficient of thermal expansion (%) at the temperature at the start of steel passing of the refractories on the outer layer

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