JP2011206781A - Nozzle for continuous casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nozzle for continuous casting in which the sticking of alumina at the part in contact with molten metal therein is prevented, and further, molding conditions and strength can be held without progressing hydration during its storage.SOLUTION: The nozzle 1 for continuous casting includes: a nozzle body 2; and a nozzle inner hole 3 formed through the inside of the nozzle body 2, and through which molten steel circulates, and a refractory obtained by adding calcium silicate or die calcium silicate, magnesia, graphite and a binder, performing kneading, and subjecting the kneaded matter to molding and heat treatment is disposed on the inner hole face 3a of the nozzle inner hole 3.

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 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 refractory constituting the continuous casting nozzle and the refractory constituting the inner hole surface were allowed to contain aggregates such as lime clinker, dolomite clinker, calcium zirconate as a CaO source and adhered. A method has been proposed in which a CaO—Al ₂ O ₃ -based low-melt material is produced by reaction with alumina.

  However, the refractory formed using the above-mentioned conventional hard-to-adhere alumina material as a CaO source has a problem that hydration proceeds during storage and the molded state and strength cannot be maintained.

JP 2006-68799 A

  The present invention has been made to solve the above-described problems. That is, the object of the present invention is to prevent alumina from adhering to the portion of the continuous casting nozzle that contacts the molten steel, and to hydrate during storage. An object of the present invention is to provide a continuous casting nozzle that can maintain the molding state and strength without progressing.

  What solves the said subject has a nozzle main body and a nozzle inner hole which penetrates the inside of the nozzle main body and allows molten steel to circulate, and the inner surface of the nozzle inner hole has calcium silicate or A continuous casting nozzle characterized in that a refractory material kneaded, molded and heat-treated by adding dicalcium silicate, magnesia, graphite and a binder is disposed.

The refractory material disposed on the inner surface of the nozzle inner hole has a mass ratio W1 / W2 of CaO component content W1 and MgO component, Al ₂ O ₃ component and SiO ₂ component content W2. It is preferably blended so as to be from 0.5 to 0.50, and kneaded, molded and heat-treated by adding graphite and a binder.

  According to the continuous casting nozzle described in claim 1, since calcium silicate or dicalcium silicate functions as a CaO source, it is possible to prevent alumina from adhering to a portion of the continuous casting nozzle that contacts the molten steel. Further, since calcium silicate or dicalcium silicate does not hydrate naturally at room temperature, the refractory forming the inner pore surface and strength can be maintained without hydration progressing during storage.

  According to the continuous casting nozzle described in claim 2, in addition to the effect of claim 1, the continuous casting nozzle can prevent alumina from adhering to the portion of the continuous casting nozzle that contacts the molten steel, and has excellent corrosion resistance. A nozzle can be constructed.

It is a longitudinal cross-sectional view of one Example of the nozzle for continuous casting of this invention. It is a longitudinal cross-sectional photograph of the nozzle body for demonstrating the effect | action of the nozzle for continuous casting of this invention. It is a longitudinal cross-sectional photograph of the nozzle body of the conventional continuous casting nozzle.

  In the present invention, the continuous casting nozzle 1 is provided on the inner hole surface 3a of the nozzle inner hole 3 by adding a refractory to which calcium silicate or dicalcium silicate, magnesia, graphite and a binder are added, kneaded, molded and heat-treated. The continuous casting nozzle 1 was realized in which the alumina was prevented from adhering to the portion in contact with the molten steel and the molding state and strength could be maintained without hydration proceeding during storage.

The continuous casting nozzle of the present invention will be described with reference to an embodiment shown in FIG.
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. A refractory material kneaded, molded and heat-treated by adding calcium silicate or dicalcium silicate, magnesia, graphite and a binder is disposed on the inner surface 3a of the hole 3. Hereinafter, each configuration will be described in detail.

  The nozzle body 2 is composed of a refractory material formed by combining various oxides with carbon-containing raw materials such as graphite and organic resin, and is a substantially cylindrical body with a diameter gradually increasing upward. The neck that has been made is integrally molded.

  A nozzle inner hole 3 through which molten steel flows is formed at the center of the nozzle body 2 so as to penetrate from the upper end to the lower end of the nozzle body 2. More specifically, the nozzle inner hole 3 expands upward in a substantially conical shape at the upper part and communicates with the upper end opening, and communicates with the discharge port 5 at the lower part. In addition, although the discharge port 5 of this Example is a single hole, generally two discharge ports may be installed in the horizontal direction.

  A cylindrical refractory 4 is disposed inside the inner hole surface 3 a of the nozzle inner hole 3. The refractory 4 is formed by adding, kneading, molding and heat treatment with calcium silicate or dicalcium silicate, magnesia, graphite and a binder.

Calcium silicate or dicalcium silicate is a refractory raw material mainly composed of CaO and SiO ₂ , and is added as a CaO source and hydrated during storage based on the knowledge that these are not naturally hydrated at room temperature. It is added for the purpose of prevention.

More specifically, since calcium silicate or dicalcium silicate is mainly composed of CaO and SiO ₂ , the molten steel is passed through the refractory 4 disposed on the inner hole surface 3 a of the nozzle inner hole 3. In this case, Al ₂ O ₃ in the molten steel adheres to the working surface of the refractory 4. Al ₂ O ₃ adhering to the working surface reacts with CaO in calcium silicate or dicalcium silicate to form a CaO—Al ₂ O ₃ —SiO ₂ -based compound and flows out together with the molten steel. Al ₂ O ₃ is prevented from adhering to the surface. Further, since calcium silicate or dicalcium silicate does not hydrate naturally at room temperature, the molding state and strength are maintained without hydration progressing during storage.

  The binder may be any inorganic binder or organic binder generally used for refractories, but is preferably an organic binder. The organic binder is used to form a carbon bond, and for example, phenol resin, furan resin, tar, pitch, and the like can be suitably used.

  The refractory 4 of this example is formed from calcium silicate or dicalcium silicate, magnesia, graphite, and a binder. However, other raw materials may be used as long as they do not adversely affect the material. What was added in anticipation of the effect is also included in the category of the present invention. For example, alumina, mullite, rholite, spinel, silicon carbide, silicon nitride, carbon flag, metal powders such as Al and Si, antioxidants such as B4C, glass components and the like can be used in small amounts.

  The refractory 4 is obtained by adding a binder to the blend, kneading by a known method, molding and heat treatment. After molding, a refractory is produced by heat treatment at an appropriate temperature according to the binder used.

  As a method of arranging the refractory 4 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 forming only the nozzle body 2 and then coating the inner hole surface of the nozzle inner hole 3 For example, a method of casting or casting, and a method of separately manufacturing the refractory 4 and arranging the refractory 4 on the nozzle body 2 through a mortar or the like can be used. In this embodiment, the refractory 4 is manufactured separately and disposed on the nozzle body 2.

The refractory 4 has a mass ratio W1 / W2 between the CaO component content W1 and the MgO component, Al ₂ O ₃ component and SiO ₂ component content W2 of 0.05 to 0.50. It is preferable that it is compounded.

This is because, when W1 / W2 is blended to be less than 0.05, the CaO component is too small and a CaO—Al ₂ O ₃ -based low-melt material is not formed. On the other hand, when W1 / W2 exceeds 0.5, there is too much CaO component, and CaO—Al ₂ O _{3 is} caused by reaction with Al ₂ O ₃ in the molten steel. This is because a large amount of low melt material is produced, resulting in a large melting loss and a problem in corrosion resistance.

(Alumina adhesion test 1)
As shown in Table 1 below, each refractory raw material was blended and kneaded, and then the molded body was heat-treated at 800 ° C. to prepare a sample body of Comparative Example 1 or Example 1.

  After the low carbon aluminum killed steel was melted at 1550 ° C. by a high frequency induction furnace and the sample body of Comparative Example 1 or Example 1 was rotated and immersed in the molten steel for 2 hours while giving a peripheral speed of 1.5 m / sec, It pulled up and the adhesion amount of the alumina was measured, respectively.

  The adhesion index of Example 1 is expressed as an index with Comparative Example 1 taken as 100, and the smaller the index, the less the alumina adheres, but the adhesion index of Example 1 is 3, which is compared with Comparative Example 1. As a result, it was confirmed that the hard adhesion of alumina was remarkably improved.

(Alumina adhesion test 2)
The refractory 4 (cylindrical body) prepared by the composition of Comparative Example 1 and Example 1 shown in Table 1 above, and the immersion nozzle arranged on the inner surface 3a as shown in FIG. Each was used. After 180 minutes of casting time, the immersion nozzle was cut and the longitudinal sections were observed.

  As a result, the refractory formed in Comparative Example 1 formed a refractory in Example 1 while a large amount of alumina adhered to the inner hole surface and turned white as shown in FIG. As a result, it was confirmed that the alumina was not visible and the adhesion was very slight.

(Hydration test)
After leaving the sample body prepared by the composition of Example 1 in Table 1 above in an apparatus prepared at a humidity of 90% and a temperature of 25 ° C. for 7 days, the hydrate was measured with an X-ray diffraction apparatus. A Japanese product was not detected. Thereby, it was confirmed that Example 1 was not hydrated and excellent in digestion resistance of CaO.

(Alumina adhesion and corrosion resistance test)
As shown in Table 2 below, each of the W1 / W2 mass ratios (CaO component content W1 and MgO component, Al ₂ O ₃ component and SiO ₂ component content W2) is different. After blending and kneading the refractory raw material, the molded body was heat treated at 800 ° C. to prepare sample bodies of Example 2, Example 3, Example 4, Example 5, and Example 6, respectively.

  Next, the low-carbon aluminum killed steel is melted at 1550 ° C. by a high-frequency induction furnace, and immersed in the molten steel for 2 hours while giving a peripheral speed of 1.5 m / sec by rotating the sample bodies of Examples 2 to 6. Then, it was pulled up and the amount of adhered alumina and the amount of erosion loss were measured.

  Further, for the sample bodies of Example 2, Example 3, Example 4, Example 5, and Example 6, the alumina adhesion amount or the amount of erosion loss of Example 4 in which the mass ratio of W1 / W2 is 0.2 is set. The respective adhesion index and erosion index were calculated as the erosion index 1.00 and the alumina adhesion index 1.00, respectively, and the results shown in Table 2 below were obtained.

  Furthermore, when the correlation between W1 / W2 and the adhesion index and the erosion index was shown in a graph using the adhesion index and the erosion index shown in Table 2, the following Table 3 was obtained.

From Table 3, it was confirmed that when W1 / W2 is smaller than 0.05, the CaO component is too small, the adhesion index of alumina becomes extremely high, and the adhesion of alumina becomes remarkable (W1 / W2 is 0). 0.03 Example 2). On the other hand, when W1 / W2 exceeds 0.5, there are too many CaO components, and a large amount of CaO—Al ₂ O ₃ -based low melt is generated by reaction with Al ₂ O ₃ in the molten steel. As a result, it was confirmed that the melting loss increased and a problem was caused in the corrosion resistance (see Example 6 in which W1 / W2 is 0.60).

Thereby, as the refractory 4 arranged on the inner hole surface 3a of the nozzle inner hole 3, the mass ratio of the CaO component content W1 and the MgO component, Al ₂ O ₃ component and SiO ₂ component content W2 It has been verified that when W1 / W2 is blended so as to be 0.05 to 0.50, it is possible to constitute a continuous casting nozzle that can prevent adhesion of alumina and also has excellent corrosion resistance.

1 Nozzle for continuous casting 2 Nozzle body 3 Nozzle inner hole 3a Inner hole surface 4 Refractory 5 Discharge port

Claims (2)

  A nozzle body and a nozzle inner hole formed through the nozzle body and through which molten steel flows, and the inner surface of the nozzle inner hole has calcium silicate or dicalcium silicate, magnesia, graphite and A continuous casting nozzle comprising a refractory material kneaded, molded and heat-treated with a binder added thereto.   The refractory disposed on the inner surface of the nozzle inner hole has a mass ratio W1 / W2 of the CaO component content W1 and the MgO component, Al2O3 component and SiO2 component content W2 of 0.05 to 0.00. 2. The continuous casting nozzle according to claim 1, wherein the continuous casting nozzle is blended so as to be 50, and is formed by kneading, molding, and heat treatment by adding graphite and a binder.