WO2016068469A1

WO2016068469A1 - Submerged nozzle for continuous casting

Info

Publication number: WO2016068469A1
Application number: PCT/KR2015/008949
Authority: WO
Inventors: 김장훈; 김세훈; 배극남
Original assignee: 주식회사 포스코
Priority date: 2014-10-31
Filing date: 2015-08-26
Publication date: 2016-05-06
Also published as: JP6419331B2; CN107073565A; KR101597254B1; CN107073565B; JP2018501109A

Abstract

The present invention suggests a submerged nozzle for continuous casting, the submerged nozzle comprising: a tubular nozzle body; an internally hollow part provided so as to surround the internal wall of the nozzle body; and a discharge opening provided at the bottom part of the nozzle body, and the internally hollow part is formed from a mixture comprising perovskite (CaTiO₃), calcium zirconate (CaZrO₃), calcium silicate (CaOㆍSiO₂) and graphite (C).

Description

Immersion nozzle for continuous casting

The present invention relates to an immersion nozzle for continuous casting, and more particularly, to an immersion nozzle for continuous casting that can suppress nozzle clogging by reacting with an alumina (Al ₂ O ₃ ) inclusion to form a low melting point material.

In general continuous casting process, the molten steel contained in the ladle is injected into the tundish, the molten steel injected from the tundish is continuously injected into the mold to cool the molten steel first, and then the cooling water is sprayed on the surface of the first cooled slab. It is the process of making cast slab by solidifying molten steel as it cools. At this time, in the process of supplying the molten steel accommodated in the tundish into the mold, the molten steel is interrupted by a gate or a stopper installed in the tapping outlet of the tundish, and is supplied into the mold through the immersion nozzle.

There are alumina (Al ₂ O ₃ ) inclusions in the molten steel. Fine inclusions that are not removed by flotation are attached to the inner wall of the immersion nozzle connecting the tundish and the mold and act as a cause of the immersion nozzle clogging. In order to solve this problem, conventionally, Ar gas is supplied to the inner wall of the immersion nozzle to trap the inclusions in a bubble, thereby suppressing the inclusion of the inclusions on the inner wall of the immersion nozzle. And a method of removing the inclusions by forming on the inner wall to form alumina and a low melting point material.

The method using Ar gas can reduce the inclusion of inclusions on the inner wall of the immersion nozzle to some extent, but there is a limit to suppressing the inclusion of inclusions due to the cooling effect by Ar gas. In addition, the method of forming a material layer containing CaO in the inner cavities is considered to be one of the most effective methods for suppressing the inclusion of inclusions on the inner wall of the immersion nozzle. As the material layer containing CaO, calcium zirconate (CaZrO ₃ ), calcium silicate (CaO.SiO ₂ ), and graphite (C) are used as shown in Korean Patent Publication No. 194-0014253. CaO elutes from the CaO and reacts with alumina to inhibit inclusion adhesion.

However, if the elution of CaO run out of a refractory material such as CaO. 2Al ₂ O _3, CaO and 7Al ₂ O ₃ is formed, which results can be rather occurs when the acceleration nozzle clogging.

In addition, in order to effectively form the low melting point material (12CaO.7Al ₂ O ₃ ), the CaO content in the inner cavity should be increased, and for this purpose, the content of calcium zirconate must be increased. However, when the content of calcium zirconate is increased, ZrO ₂ destabilizes with CaO elution, resulting in volume change due to the phase transition from cubic or monoclinic to tetragonal at the casting temperature. do. This may cause problems such as cracking or dropping of the discharge port during casting, which is why it is impossible to increase the CaO content by increasing the calcium zirconate content. In addition, when the molten steel of 1550 ℃ directly contacts at room temperature, cracks may occur in the immersion nozzle due to instantaneous expansion due to thermal shock, and thus, the immersion nozzle is preheated at 800 to 1100 ℃. This requires higher control of the immersion nozzle preheating.

The present invention provides an immersion nozzle for continuous casting that can suppress adhesion of inclusions by allowing a low melting point compound to be easily formed when the alumina inclusions adhere to the inner cavity.

The present invention provides an immersion nozzle for continuous casting that can increase the CaO content without causing problems such as cracking or dropping of the discharge port during casting.

The present invention provides an immersion nozzle for continuous casting using a mixture containing rare titanium (CaTiO ₃ ), calcium zirconate (CaZrO ₃ ), calcium silicate (CaO.SiO ₂ ), and graphite (C). do.

The continuous casting immersion nozzle according to the embodiments of the present invention includes a tubular nozzle body, an internal hole provided to surround at least a portion of the inner wall of the nozzle body, and an outlet provided in the lower portion of the nozzle body. Is formed from a mixture containing rare titanium (CaTiO ₃ ), calcium zirconate (CaZrO ₃ ), calcium silicate (CaO.SiO ₂ ) and graphite (C).

The inner cavity is formed to a thickness of 3mm to 5mm.

The rare titanium, calcium zirconate, calcium silicate and graphite are added in an amount of 95 wt% to 99 wt% and mixed with a binder of 1 wt% to 5 wt% with respect to 100 wt% of the mixture.

The rare titanium and calcium zirconate are contained in an amount of 40 wt% to 90 wt% with respect to 100 wt% of the mixture.

The rare titanium is contained in 5% to 50% of calcium zirconate.

The graphite is contained in an amount of 5 wt% to 35 wt% with respect to 100 wt% of the mixture.

The calcium silicate is contained in an amount of 1 wt% to 25 wt% with respect to 100 wt% of the mixture.

The discharge port is formed of a mixture containing rare titanium, calcium zirconate, calcium silicate and graphite.

The discharge port has a less CaO content than the inner cavity.

CaO content of the inner cavity is 15wt% to 35wt%, CaO content of the discharge port is 10wt% to 25wt%.

The inner cavity and the discharge port are formed with a porosity of 15% to 35%.

In an embodiment of the present invention, a mixture including a rare titanium (CaTiO ₃ ), calcium zirconate (CaZrO ₃ ), calcium silicate (CaO.SiO ₂ ), and graphite (C) To form. According to the present invention, even if the preheating time of the immersion nozzle is short or the preheating temperature is low, the likelihood of problems such as crack generation and discharge port dropping becomes low, and as TiO ₂ is present in the inner cavity and the CaO content is increased, The inclusion of inclusions can be effectively suppressed. Therefore, it is possible to realize the long life of the immersion nozzle to achieve the productivity and cost reduction effect at the same time.

1 is a schematic view of a continuous casting apparatus is applied to the immersion nozzle according to an embodiment of the present invention.

Figure 2 is a cross-sectional view of the immersion nozzle for continuous casting according to an embodiment of the present invention.

3 is an image after the alumina adhesion reaction test for Al ₂ O ₃ -C, CaZrO ₃ and CaTiO ₃ .

4 to 7 is a result of the reactivity experiment of the sample formed by CaTiO ₃ and CaZrO ₃ in different ratios on the alumina substrate.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various forms, and only the embodiments are intended to complete the disclosure of the present invention and to those skilled in the art. It is provided for complete information.

1 is a schematic diagram of a continuous casting apparatus including an immersion nozzle according to an embodiment of the present invention, Figure 2 is a cross-sectional view of the immersion nozzle of the present invention.

Referring to FIG. 1, the continuous casting apparatus to which the present invention is applied includes a tundish 200 for storing molten steel that has undergone a steelmaking process in the ladle 100 and a lower side of the tundish 200 to solidify the molten steel. A mold 300 for manufacturing a cast steel, a gate 400 corresponding to a lower side of the tapping hole 210 of the tundish 200 to control tapping of molten steel, and a tapped dish correspondingly disposed below the gate 400. An immersion nozzle 500 for guiding the molten steel in the mold 200 to the mold 300. In addition, the gate 400 may use a sliding gate, and the sliding gate may include upper and

lower fixing plates

410 and 420, and a sliding plate 430 provided between the upper fixing plate 410 and the lower fixing plate 420. It includes. The continuous casting device may control the tapping of the molten steel by sliding the sliding plate 430 to control the communication between the tapping hole 210 of the tundish 200 and the immersion nozzle 500. Of course, the present invention is not limited thereto, and any means capable of controlling communication between the tapping hole 201 of the tundish 200 and the immersion nozzle 500 may be used.

The immersion nozzle 500 is formed in the tubular nozzle body 510 and the inner wall of the nozzle body 510 to guide the molten steel in the tundish 200 into the mold 300, as shown in FIG. The molten steel in the immersion nozzle 500 is formed so as to be symmetrical with each other on the inner cavities 520, the sloughed portion 530 outside the nozzle body 510, and both sides of the lower part of the nozzle body 510. A discharge port 540 to be discharged to

The nozzle body 510 may be manufactured using any one material of Al ₂ O ₃ -C and Al ₂ O ₃ -SiO ₂ -C, and is manufactured in a tubular shape so that molten steel can flow. In addition, the slain portion 530 may be formed using a material of ZrO ₂ -C, it may be formed on the outer surface of the nozzle body 510 above the discharge port 540.

The inner cavity 520 is formed on the inner wall of the nozzle body 510. That is, the inner cavities 520 may be formed on the inner wall of the immersion nozzle 500 to have a predetermined thickness, for example, 3 mm to 5 mm, to be in contact with the molten steel. At this time, the inner cavity 520 may be formed so as not to protrude from the inner wall of the nozzle body 510. That is, the internal hole 520 may be formed on the inner wall of the immersion nozzle 500 to a depth of 3 mm to 5 mm. Of course, the inner cavities 520 may be inserted into the inner wall of the immersion nozzle 500 at some depth and protruded from the inner wall of the immersion nozzle 500. In addition, the internal hole 520 may be formed to have a length of 50% or more from the lower side in the longitudinal direction of the nozzle body 510. Of course, the inner cavity 520 is preferably formed on the entire inner wall of the nozzle body 510. The inner cavity 520 of the present invention may be formed using a mixture of rare titanium (CaTiO ₃ ), calcium zirconate (CaZrO ₃ ), calcium silicate (CaO · SiO ₂ ), and graphite (C) and a binder. have. By forming the inner cavity 520 into a mixture containing rare titanium, CaO is eluted by the following reaction and CaO is reacted with alumina to inhibit inclusions.

CaTiO ₃ → CaO + TiO ₂

CaZrO ₃ → CaO + ZrO ₂

CaOZrO ₂ → CaO + ZrO ₂

12CaO + 7Al ₂ O ₃ → 12CaO7Al ₂ O ₃

That is, CaO and TiO ₂ are separated from the raretite, CaO and ZrO ₂ are separated from the calcium zirconate, and then CaO and alumina react to form 12CaO.7Al ₂ O ₃ , thereby forming inclusions on the inner wall of the immersion nozzle 500. Will be suppressed. Here, the rare titanium is lower in activation energy than the calcium zirconate and the rare titanium is separated into CaO and TiO ₂ before the calcium zirconate is separated into CaO and ZrO ₂ . Therefore, since CaO is first separated from the rare titite before CaO is separated from calcium zirconate, the overall CaO content is increased, thereby improving the reactivity of CaO and alumina, thereby further suppressing adhesion of inclusions. can do. In this case, after CaO is separated, TiO ₂ and ZrO ₂ serve to maintain the shape of the inner cavity 520. However, when the content of calcium zirconate is increased to increase the content of CaO, ZrO ₂ may be destabilized and cracks may be generated during casting. That is, when CaO is separated from calcium zirconate, ZrO ₂ remains, but since CaO used as a stabilizer of ZrO ₂ is separated, ZrO ₂ is not stabilized, and thus molten steel contacts the inner cavity 520 or the immersion nozzle. Cracks and the like occur during preheating 500. However, when the rare titanium is included, the TiO ₂ remaining after the CaO is separated from the rare titanium is maintained in a stabilized state and no crack is generated because CaO is not used as a stabilizer. Therefore, since the titanium dioxide is contained and TiO ₂ separated therefrom, even if the preheating time of the immersion nozzle 500 is short or the preheating temperature is low, problems such as cracking and dropping of the discharge port are reduced. In addition, ZrO ₂ does not react with alumina, but TiO ₂ may react with alumina to further suppress inclusion adhesion. That is, the reaction scheme described the main reaction of CaO and alumina, but TiO ₂ also reacts with alumina. As a result, by containing rare titanium, the content of CaO can be increased without increasing the content of calcium zirconate, and the reactivity with alumina can be further improved by TiO ₂ reacting with alumina, further suppressing adhesion of inclusions. can do. In addition, since TiO ₂ does not use CaO as a stabilizer, generation of cracks or the like during casting can be prevented.

The internal vacancy part 520 according to the present invention is formed by mixing a rare titanium, calcium zirconate, calcium silicate, and graphite with a binder. The internal vaccinating material including the rare titanium is mixed at 95 wt% to 99 wt%, The binder may be mixed at 1 wt% to 5 wt%. That is, with respect to 100 wt% of the mixture of the internal cavity material and the binder, the internal cavity material is mixed at 95wt% to 99wt%, and the binder is mixed at 1wt% to 5wt%. Thermosetting resins, such as a phenol resin, can be used as a binder. Here, if the binder is less than 1wt%, the mixing of the internal cavity material is difficult, and if the binder is more than 5wt%, the humidity is high, so that molding of the internal cavity 520 is difficult. In addition, the rare titanium and calcium zirconate in the mixture may be contained in 40wt% to 90wt%. That is, the rare-tarite and calcium zirconate may be contained in an amount of 40 wt% or more and 90 wt% or less with respect to 100 wt% of the mixture of the inner cavity material and the binder. Since the rare titanium and calcium zirconate have a role of maintaining TiO ₂ and ZrO ₂ in the shape of the inner cavity 520 after CaO is eluted, it should be contained at least 40wt% to maintain the shape of the inner cavity 520. It should be contained below 90wt% for addition of other ingredients. In addition, the rare titanium may be contained in 5% to 50% compared to calcium zirconate. That is, the rare titanium may be contained in an amount of 5 wt% to 50 wt% with respect to 100 wt% of the mixture of rare titanium and calcium zirconate. When the rare titanium is mixed less than 5% compared to calcium zirconia, the effect of the present invention is insignificant, and when it is mixed in excess of 50wt%, the reactivity is excessive and the life of the immersion nozzle 500 may be shortened. That is, when the excessive content of the rare titanium stones, the inner cavity 520 is quickly consumed due to the excessive reaction, and the life of the immersion nozzle 500 may be shortened accordingly. And, graphite may be contained in 5wt% to 35wt% with respect to 100wt% of the mixture. Graphite should be added at least 5wt% for heat transfer to the outside of the immersion nozzle 500, and may be oxidized when excessively added in excess of 35wt%. In addition, the calcium silicate is composed of CaO.SiO ₂ + 2CaO.SiO ₂ and may be contained in an amount of 1 wt% to 25 wt% with respect to 100 wt% of the mixture. The amount of calcium silicate may vary depending on the amount of rare titanium, but in order to induce a reaction with alumina, the amount of calcium silicate must be contained in an amount of 1 wt% or more, and when added in excess of 25 wt%, the life of the immersion nozzle 500 is excessive. Can be shortened.

On the other hand, the discharge port 540 may also be provided with the same material as the internal hole 520. That is, it can be formed using a mixture of rare titanium, calcium zirconate, calcium silicate and graphite (C) and a binder. However, the discharge port 540 may be formed to a content lower than the content of the mixture of the internal cavity 520 to form a total CaO content less than the total CaO content of the internal cavity 520. That is, the CaO content of the rare titanium, calcium zirconate, calcium silicate, and graphite may be formed in the inner cavities 520 of 15wt% to 35wt%, and the discharge holes 540 may be formed of 10wt% to 25wt%. On the other hand, the inner cavity 520 and the discharge port 540 is preferably manufactured so that the porosity is 15% to 35%. If the porosity of the inner cavity 520 and the discharge port 540 is dense to less than 15%, cracks may occur during casting, and if it exceeds 35%, the strength may decrease.

An immersion nozzle 500 is three in studying diluent titanium 520 formed on the inner wall of the nozzle body (510) (CaTiO _3), calcium zirconate (CaZrO ₃₎ in accordance with one embodiment of the present invention as described above, It is formed of a material containing calcium silicate (CaO.SiO ₂ ) and graphite (C). The inclusion of rare titanium can increase the content of CaO without increasing the content of calcium zirconate, improve the reactivity with alumina by reacting TiO ₂ with alumina, and further suppress the adhesion of inclusions. Heavy cracking can be prevented.

3 is an image after the alumina adhesion reaction test according to the material of the sample, the image after the alumina adhesion reaction test for Al ₂ O ₃ -C, CaZrO ₃ and CaTiO ₃ . That is, FIG. 3 (a) is an image of the Al ₂ O ₃ -C substrate, Figure 3 (b) is an image of CaZrO ₃ substrate, and Fig. 3 (c) is the image of the CaTiO ₃ substrate. As shown, it can be seen that the inclusion adhesion level is the lowest in Al ₂ O ₃ -C and the highest in order of CaZrO ₃ and CaTiO ₃ . Further, after the alumina reaction tests for each substrate component analysis, Al ₂ O ₃ is -C Al ₂ O ₃ is 98wt% and the other appeared to 2wt%, CaZrO ₃ is a _{_{57wt% Al 2 O 3, CaO}} -Al ₂ O ₃ compound was found to be 37wt% and the other 6wt%. In addition, CaTiO ₃ was 15 wt% in Al ₂ O ₃ , 78 wt% in CaO-Al ₂ O ₃ , and 7 wt% in the other. Therefore, CaTiO ₃ having the highest reactivity is easier to dissolve CaO in the material than CaZrO ₃ , and CaO is easy to make alumina and low melting point materials. As a result, when CaTiO ₃ is added as the material of the inner cavities 520 and the discharge holes 540 of the immersion nozzle 500, the adhesion of the inclusions of the immersion nozzle 500 can be effectively suppressed.

4 to 7 are mixed with CaTiO ₃ and CaZrO ₃ in a ratio of 0: 100, 30:70, 50:50, and 70:30 on an alumina substrate, and then maintained at 1550 ° C. for 3 hours to observe reactivity. to be. Here, FIGS. 4 to 7 (a) show the reactivity of Al, and FIGS. 4 to 7 (b) show the reactivity of Ca. As shown in (b) of FIGS. 4 to 7, it can be seen that all of Ca in the sample is diffused into the alumina substrate. When CaTiO ₃ and CaZrO ₃ are mixed in a ratio of 30:70, the sample remains intact. In the case of 50:50, it was confirmed that the sample was active but remained undissolved after 3 hours without melting. However, when CaTiO ₃ and CaZrO ₃ are mixed in a ratio of 70:30, it can be confirmed that all of the samples are dissolved after 3 hours, and in this case, they cannot be used as internal parts of the immersion nozzle due to the rapid reaction. Therefore, the content of CaTiO ₃ is preferably added in not more than 50% compared to CaZrO _3.

On the other hand, although the technical spirit of the present invention has been described in detail according to the above embodiment, it should be noted that the above embodiment is for the purpose of explanation and not for the limitation. In addition, those skilled in the art will understand that various embodiments are possible within the scope of the technical idea of the present invention.

Claims

A tubular nozzle body, an internal hole provided to at least partially surround the inner wall of the nozzle body, and a discharge port provided at a lower portion of the nozzle body,

The inner cavity is a continuous casting immersion nozzle formed of a mixture containing rare titanium (CaTiO 3 ), calcium zirconate (CaZrO 3 ), calcium silicate (CaO.SiO 2 ) and graphite (C).
The immersion nozzle for continuous casting according to claim 1, wherein the inner cavities have a thickness of 3 mm to 5 mm.
The immersion nozzle for continuous casting according to claim 1 or 2, wherein the rare titanium, calcium zirconate, calcium silicate and graphite are added in an amount of 95 wt% to 99 wt% and mixed with a binder of 1 wt% to 5 wt% with respect to 100 wt% of the mixture. .
The immersion nozzle for continuous casting according to claim 3, wherein the rare titanium and calcium zirconate are contained in an amount of 40 wt% to 90 wt% with respect to 100 wt% of the mixture.
The immersion nozzle for continuous casting according to claim 4, wherein the rare titanium is contained in an amount of 5% to 50% relative to calcium zirconate.
The immersion nozzle for continuous casting according to claim 4, wherein the graphite is contained in an amount of 5 wt% to 35 wt% with respect to 100 wt% of the mixture.
The immersion nozzle for continuous casting according to claim 6, wherein the calcium silicate is contained in an amount of 1 wt% to 25 wt% based on 100 wt% of the mixture.
The immersion nozzle for continuous casting according to claim 1 or 2, wherein the discharge port is formed of a mixture containing rare titanium, calcium zirconate, calcium silicate and graphite.
The immersion nozzle for continuous casting according to claim 8, wherein the discharge port has a lower CaO content than the inner cavity.
The immersion nozzle for continuous casting according to claim 9, wherein the CaO content of the inner cavity is 15wt% to 35wt%, and the CaO content of the discharge port is 10wt% to 25wt%.
The immersion nozzle for continuous casting according to claim 10, wherein the inner hole and the discharge hole are formed at a porosity of 15% to 35%.