JP2014073527A - Continuous casting nozzle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a continuous casting nozzle capable of suppressing the adhesion of alumina to a part contacted with molten steel of the continuous casting nozzle, even if heating temperature is low.SOLUTION: A continuous casting nozzle 1 has a nozzle body 2, and a nozzle inner hole 3 formed so as to penetrate the nozzle body 2 and through which molded steel circulates. On an inner hole surface 4 of the nozzle inner hole 3, a refractory 5 containing alumina and pyrophillite as main components, to which silica and fluorite are added and mixed, molded, and subjected to a heat treatment is arranged.

Description

  The present invention relates to a nozzle used for continuous casting such as an immersion nozzle, a long nozzle, and a tundish upper nozzle for injecting molten steel from a tundish into a mold. More specifically, the present invention relates to a continuous casting nozzle in which a refractory having an alumina adhesion preventing function is disposed in an inner hole that comes into contact with molten steel.

  When casting slabs, the alumina inclusions in the molten steel repeatedly adhere to, coalesce, and drop off on the inner hole surface of the continuous casting nozzle, and these are taken into the slab along with the molten steel flow, resulting in defects in the slab. Has led to a decline. In addition, alumina inclusions may adhere to the inner hole surface of the continuous casting nozzle, resulting in narrowing of the inner hole and thus blocking. In particular, the adhesion of these alumina inclusions to the inner hole surface is remarkable in continuous casting of aluminum killed steel.

  As a method for solving this problem, the present applicants first applied a refractory composed mainly of alumina and rholite to a refractory constituting the nozzle for continuous casting and a refractory constituting the inner hole surface. The nozzle used for continuous casting was proposed.

  However, this continuous casting nozzle may be used by heating in advance at a high temperature, but there is a problem that the adhesion suppressing performance is not sufficiently exhibited when the heating temperature is low.

Japanese Patent No. 3101650

  Then, the subject of this invention is providing the nozzle for continuous casting which can suppress that an alumina adheres to the site | part which contacts the molten steel of the nozzle for continuous casting, even when heating temperature is low.

  What solves the said subject has a nozzle main body and the nozzle inner hole which penetrates the inside of this nozzle main body, and a molten steel distribute | circulates. A continuous casting nozzle characterized by comprising a refractory material mainly composed of stone and kneaded, molded and heat-treated by adding silica and fluorite.

The amount of silica is preferably 1 to 10% by weight. The blending amount of the fluorite is preferably 1 to 5% by weight. The rholite preferably has a particle size of 250 μm or less and 60% by weight or less of the total amount of rholite.
The rholite is pyrophyllite (Al ₂ O ₃
・ 4SiO ₂・ H ₂
O) is the main component. It is preferable that the rholite is calcined at 800 ° C. or higher to eliminate crystal water.

According to the continuous casting nozzle described in claim 1, even when the heating temperature is low, it is possible to suppress the alumina from adhering to the portion of the continuous casting nozzle that contacts the molten steel.
According to the nozzle for continuous casting described in claim 2, since a low melting point compound is easily generated on the inner surface of the nozzle inner hole, and a dense structure layer is more reliably formed, the adhesion of alumina is further suppressed. be able to.
According to the continuous casting nozzle described in claim 3, since a low-melting-point compound is easily generated on the inner surface of the nozzle inner hole and a dense structure layer is more reliably formed, the adhesion of alumina is further suppressed. be able to.

It is a longitudinal cross-sectional view of one Example of the nozzle for continuous casting of this invention.

  In the present invention, the inner surface 4 of the nozzle inner hole 3 is provided with a refractory 5 which is mainly composed of alumina and rholite, added with silica and fluorite, kneaded, molded and heat-treated. A low melting point compound is easily generated on the inner hole surface 4 of the hole 3 and a dense structure layer is formed. Even when the heating temperature is low, it is possible to prevent the alumina from adhering to the portion of the continuous casting nozzle that contacts the molten steel. The nozzle 1 for continuous casting was realized.

The continuous casting nozzle of the present invention will be described with reference to an embodiment shown in the drawings.
As shown in FIG. 1, the continuous casting nozzle 1 of this embodiment has a nozzle body 2 and a nozzle inner hole 3 that is formed through the nozzle body 2 and through which molten steel flows. The inner surface 4 of the hole 3 is provided with a refractory 5 which is mainly composed of alumina and rholite, kneaded, molded and heat-treated by adding silica and fluorite. Hereinafter, each configuration will be described in detail.

  The continuous casting nozzle 1 is an immersion nozzle that is disposed between a tundish and a mold and injects molten steel from the tundish into the mold. The surface layer portion of the nozzle inner hole 3 through which the molten steel of the continuous casting nozzle 1 flows is formed of the refractory 5 and the nozzle body 2 is formed of a conventional alumina-graphite refractory.

  The nozzle body 2 is a substantially cylindrical body, and a neck portion 7 whose diameter is increased upward is integrally formed at an upper portion thereof. A nozzle inner hole 3 through which molten steel flows is formed at the center of the nozzle body 2 so as to penetrate downward from the upper end of the nozzle body 2. The nozzle inner hole 3 communicates with the upper end opening 8 and communicates with the discharge ports 6a and 6b provided in the lower portion so as to face each other in the horizontal direction.

  The dimensions of the continuous casting nozzle 1 are, for example, a total length of about 1 m, a diameter of the nozzle inner hole 3 of about 6 cm, a diameter of the nozzle body 2 of 16 cm, and a thickness of about 5 cm. And the thickness of the refractory 5 is about 2 to 15 mm. In addition, this dimension is an example, Comprising: This invention is not limited, A design is suitably changed by the dimension of the cast piece cast.

  A refractory 5 is disposed inside the inner hole surface 4 of the nozzle inner hole 3. This refractory 5 is made of alumina and rholite as main components, and is kneaded, molded and heat-treated by adding silica and fluorite.

Alumina, one of the main components of the refractory 5, is a component that imparts the strength of the refractory 5, and is preferably blended in an amount of 15 to 60% by weight. As an aggregate mainly composed of alumina (Al ₂ O ₃ ), spinel (MgO.Al ₂ O ₃ , Al ₂ O ₃ , 4SiO ₂ ) may be blended in place of or together with alumina.

  The rholite, which is one of the main components of the refractory 5, has a semi-melting temperature of around 1500 ° C. and melts at the working surface in contact with the molten steel to form a glass film. Smoothes the air and suppresses air entrainment through the refractory structure by the glass film.

  In order to actively generate a glass film on the inner hole surface 4 and to maintain the spalling resistance, it is desirable that the blending weight ratio of the rholite is 40% by weight or more, and 86% by weight or more. Then, since softening deformation becomes large and corrosion resistance against molten steel is inferior, 85% by weight or less is desirable.

  Three types of rholite can be used: pyrophyllite loam, kaolinic loite, and sericite rholite, but the inner surface 4 that comes into contact with the molten steel at the time of use becomes semi-molten and the glass layer Pyrophyllite rholite having a fire resistance of SK29 to 32 is preferable in view of the formation of slag and the resistance to erosion of molten steel. This is because the kaolinic loite has a high fire resistance of SK33 to 36, and conversely, the sericite loite has a low fireproofness of SK26 to 29, which is undesirable.

  As the rholite, it is preferable to use a rholite which has been calcined at 800 ° C. or higher and crystal water has disappeared. When a nozzle formed by blending rhostone that is not calcined is fired, the crystal water in the rholite is released at 500 to 800 ° C., and at this time, the coefficient of thermal expansion becomes abnormally large, and the molded body is cracked. It is.

  The rhostone is preferably one having a particle size of 250 μm or less and 60% by weight or less of the total amount of rhostone. When the grain size of rholite is an average grain size of 250 μm or less and 60% or more of the rhostone compounding weight ratio, it tends to cause structural defects such as lamination during molding, and when used as a nozzle for continuous casting, Since softening deformation of rholite particles is likely to occur, it is preferably 60% or less.

Silica (SiO ₂ ) and fluorite (CaF ₂ ) added to the two main components are added to form a low melting point compound on the inner surface 4 of the nozzle inner hole 3 to form a dense structure layer. Is. Thereby, even when the heating temperature of the nozzle 1 for continuous casting is low, it is suppressed that an alumina adheres to the site | part which contacts the molten steel of the nozzle 1 for continuous casting.

  The amount of silica is preferably 1 to 10% by weight. This is because when the amount is less than 1% by weight, the formation reaction of a dense tissue layer is small, and the alumina adhesion suppressing effect is low. This is because if it exceeds 10% by weight, the melting loss tends to increase.

  The blending amount of fluorite is preferably 1 to 5% by weight. This is because when the amount is less than 1% by weight, the formation reaction of a dense tissue layer is small, and the alumina adhesion suppressing effect is low. This is because if the amount exceeds 5% by weight, the tendency for melting loss to increase appears.

  In order to form a composition in which silica and fluorite are added to alumina and rholite, which are the main components, into a refractory 5, a thermosetting resin such as phenol resin or furan resin is used as a binder. Mix by weight, shape into nozzle shape and fire. This forming method is preferable in that CIP uniformly compresses the formed body. The firing temperature is preferably about 1000 to 1300 ° C. Further, as the firing atmosphere, a reducing atmosphere, that is, a non-oxidizing atmosphere is preferable to an oxidizing atmosphere because it does not oxidize the blended resin.

  As a method of arranging the refractory 5 on the inner hole surface 3a of the inner hole 3, a method of integrally forming the nozzle body 2 simultaneously with the molding of the nozzle body 2, or after forming only the nozzle body 2, the inner hole surface of the nozzle inner hole 3 is coated. And a method of casting and casting, and a method of forming and firing the refractory 5 separately and placing the refractory 5 on the nozzle body 2 through a mortar or the like.

(test)
The following molded body was prepared from the composition obtained by adding powder and solution phenol resin in the range of 5 to 10% by weight to 6 mixtures having different component compositions, and mixing and kneading them. .

  The first molded body (hereinafter referred to as molded body 1) is a molded body having a size of 30 mm × 30 mm × 230 mm for testing the adhesion amount of non-metallic inclusions such as alumina and the corrosion resistance against molten steel. The second molded body (hereinafter referred to as the molded body 2) is a molded body having dimensions of an outer diameter of 100 mm, an inner diameter of 60 mm, and a length of 250 mm for testing heat-resistant spalling properties. Samples 1 to 6 were prepared by reducing and firing each of the obtained compacts at a temperature in the range of 1000 ° C. to 1200 ° C.

  The following table shows the composition, porosity, bulk density, and bending strength of Samples 1 to 3 (hereinafter referred to as Invention Examples 1 to 3) and Samples 4 to 6 (hereinafter referred to as Comparative Examples 4 to 6). It was shown in 1.

  In addition, each of Invention Examples 1 to 3 and Comparative Samples 4 to 6 of the molded body 2 were heated in an electric furnace at a temperature of 1500 ° C. for 30 minutes, and then quenched with water to investigate the heat resistant spalling property. The results are also shown in Table 1 below.

  Further, Examples 1 to 3 of the invention 1 and Comparative Samples 4 to 6 of the molded body 1 were immersed in molten steel at a temperature of 1520 ° C. containing aluminum in the range of 0.02 to 0.05% by weight for 180 minutes. Then, the erosion rate (%) and the alumina adhesion amount (mm) were investigated. The results are also shown in Table 1 below.

(Discussion)
There were no cracks in any of the inventive examples and the comparative examples.
Further, in Example 1 of the present invention, the amount of alumina adhered is 1.0 mm, and it is considered that the adhesion is small because a dense alumina layer is formed of silicon fluoride. In Example 2 of the present invention, the alumina adhesion amount is 1.0 mm, and it is considered that the adhesion is small because a dense alumina layer is formed of silicon fluoride. In Invention Example 3, since the amount of fluorite added was the largest, the amount of alumina adhered was the smallest, 0.8 mm. In Comparative Example 4, since silica and fluorite were not added, the amount of alumina adhered was as large as 2.0 mm. In Comparative Example 5, silica and fluorite were not added, and graphite was blended, so that the amount of adhered alumina was the largest at 3.0. In Comparative Example 6, silica and fluorite were added, but graphite was added, so the amount of alumina adhered was as high as 1.8.

  From the above, the amount of alumina adhered is less in the inventive examples 1 to 3 than in the comparative examples 4 to 6, and the refractory prepared by adding silica and fluorite to the main components alumina and rholite is used as the inner surface. It was confirmed that the adhesion of alumina can be reduced and the inner hole narrowing of the nozzle for continuous casting and further the blockage can be suppressed.

DESCRIPTION OF SYMBOLS 1 Nozzle for continuous casting 2 Nozzle body 3 Nozzle inner hole 4 Inner hole surface 5 Refractory 6 Discharge port 7 Neck part 8 Upper end opening

Claims (3)

  A nozzle body and a nozzle inner hole formed through the nozzle body and through which molten steel circulates, and the inner surface of the nozzle inner hole is mainly composed of alumina and rholite, silica And a refractory material kneaded, molded and heat-treated with fluorite added thereto, and a continuous casting nozzle.   The nozzle for continuous casting according to claim 1, wherein the amount of silica is 1 to 10% by weight.   The continuous casting nozzle according to claim 1, wherein a blending amount of the fluorite is 1 to 5 wt%.

Images