WO2019066151A1

WO2019066151A1 - Refractory composition and submerged entry nozzle

Info

Publication number: WO2019066151A1
Application number: PCT/KR2018/000428
Authority: WO
Inventors: 강윤배; 이주혁; 이우진; 김성광; 강명훈
Original assignee: 주식회사 포스코; 포항공과대학교 산학협력단
Priority date: 2017-09-28
Filing date: 2018-01-09
Publication date: 2019-04-04

Abstract

Provided is a refractory composition comprising, by wt%, 15-30% of carbon, 5-15% of silica, 3-10% of a carbon monoxide scavenger and the balance of alumina, wherein the carbon monoxide scavenger comprises a metal carbide.

Description

【Specification】

[Title of the invention]

Refractory composition and immersion nozzle

TECHNICAL FIELD

And to a dipping nozzle formed of a refractory composition and a refractory composition capable of preventing nozzle clogging by suppressing the formation of the nozzle.

BACKGROUND ART [0002]

Continuous casting equipment consists of ladle, tundish, mold, secondary angle. The molten steel in the ladle is injected into the mold via the tundish. All the molten steel produced is moved from the tundish to the mold through the immersion nozzle. Therefore, when the flow of the immersion nozzle or the molten steel is not smooth, It will be strongly influenced by steel production.

A representative problem that occurs with immersion nozzles is nozzle clogging. Nozzle clogging is the residual non-metallic inclusions within the molten steel that is attached to the inner wall of the nozzle ^portion, and the discharge by reducing my studies and the discharge portion and the inner diameter occurs, by inhibiting the flow of molten steel. On the other hand, in the case of extremely low carbon steels containing Ti, in addition to non-metallic inclusions, iron and iron oxide components adhere to form adherent forms in a more rigid form.

Several methods have been proposed to solve the existing nozzle clogging phenomenon. First, the absolute amount of the residual nonmetallic inclusions in the molten steel is lowered to reduce the inclusions to be adhered to the inner wall of the immersion nozzle at the time of continuous casting. With the development of clean steel production technology, removal of residual inclusions in the molten steel has been smoothly carried out. Secondly, when the residual nonmetallic inclusions, especially the alumina inclusions, adhere to the inner wall of the nozzle, they rapidly sinter with the refractory material and other inclusions due to the high temperature to form the deposit layer on the inner wall of the nozzle. To wash it down in liquid form.

Third. A method of injecting argon gas into the immersion nozzle from the upper part of the immersion nozzle to induce an argon gas layer between the inner wall of the nozzle and the molten steel to prevent the residual inclusion from contacting the inner wall of the nozzle.

However, the modern steelmaking process After that, nozzle clogging occurred frequently. In particular, in the case of ultra low carbon steel,

The nozzle clogging is significantly different depending on the presence or absence of Ti, and the shape of the nozzle attachment is not composed of only nonmetallic inclusions, and is observed as a mixture between a large amount of adhering type and nonmetallic inclusions. This phenomenon has a limit in solving the above-mentioned conventional methods. There is a need for a new method capable of reducing the influence of Ti on the clogging of the nozzle and the occurrence of the present-type deposit.

DETAILED DESCRIPTION OF THE INVENTION

[Technical Problem]

The present invention provides an immersion nozzle formed of a refractory composition and a refractory composition capable of preventing nozzle clogging by trapping carbon monoxide generated from refractory materials and suppressing the formation of carbon monoxide.

[Technical Solution]

The refractory composition according to one embodiment of the present invention comprises, in weight percent, 15 to 30% of carbon, 5 to 15% of silica, 3 to 10% of carbon monoxide collecting agent, and the balance alumina, Metal carbide.

The carbon monoxide scavenger may have a negative Gibbs free energy change value (AG) at 1500 to 1550 ^° C due to reaction with CO (g).

The carbon monoxide collecting agent may include at least one of B ₄ C, AI ₄ C 3, SiC, and CaC ₂ .

The carbon monoxide collecting agent is B ₄ C, and may contain 3 to 10%. The following expression (1) can be satisfied.

[Formula 1]

0.23 < [carbon monoxide scavenger] / [silica] 1

(In the formula (1), [silica] and [carbon monoxide collecting agent] represent amounts of silica and carbon monoxide collecting agent (% increase), respectively.

According to an embodiment of the present invention, there is provided an immersion nozzle in which molten steel is moved from a tundish to a mold, wherein at least a portion of the immersion nozzle in contact with the molten steel includes a nozzle body, Wherein the carbon monoxide trapping agent comprises 15 to 30% of carbon, 5 to 15% of silica, 3 to 10% of carbon monoxide collecting agent, and the balance alumina, Carbide.

The carbon monoxide collecting agent may include at least one of B ₄ C, AI ₄ C 3, SiC and CaC ₂ .

The molten steel may include at least one of A 1 and Ti.

Wherein the nozzle body is in contact with the molten steel, and the inner body is made of the refractory composition; And a discharging portion made of the refractory composition, in which the molten steel is discharged.

A concentration gradient may be formed in the nozzle body such that the concentration of the carbon monoxide trapping agent increases toward the contact interface where the molten steel is brought into contact with the molten steel.

【Effects of the Invention】

It is possible to prevent the clogging of the nozzle by trapping the carbon monoxide generated in the refractory through the carbon monoxide capturing agent such as metal carbide and suppressing the formation of the carbon monoxide.

BRIEF DESCRIPTION OF THE DRAWINGS

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing a process of generating gaseous carbon monoxide in a refractory and a deoxidation process by a carbon monoxide scavenger (B ₄ C) in a refractory composition according to an embodiment of the present invention.

FIG. 2 is a graph showing various types of oxides produced according to changes in the content of Al and Ti contained in molten steel.

Fig. 3 is a photograph now showing at the contact interface between the molten steel containing Al and Ti and the refractory.

4 is a graph showing values of change in free energy according to temperatures of ¾C, AI4C3 and CaC ₂ .

5 is a cross-sectional view of an immersion nozzle according to an embodiment of the present invention.

Fig. 6 is a graph showing the correlation between the compositional change of carbon monoxide scavenger (B ₄ C) and the present average thickness.

7 is a photograph showing the reactant produced in the contact interface according to the immersion rotation reaction result of Comparative Example 1. Fig. FIG. 8 is a photograph showing reactants produced in the contact interface according to the immersion rotation reaction result of Example 1. FIG.

BEST MODE FOR CARRYING OUT THE INVENTION

The terms first, second, and third, etc. are used to describe various portions, components, regions, layers, and / or sections, but are not limited thereto. These terms are used interchangeably with any part, element, region, layer or section of a section, element, or region. It is used only to distinguish it from layers or sections. Accordingly, a first portion, component, region, layer or section described in the sub-section may be referred to as a second portion, component, region, layer or section without departing from the scope of the present invention.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms as used herein include plural forms as long as the phrases do not expressly express the opposite meaning thereto. As used herein, the term " comprising " Integers, regions, integers, steps, operations, elements, and / or components; Steps, operations, elements and / or components.

When referring to a portion as being "on" or "on" another portion, it may be directly on or over another portion, or may involve another portion therebetween. By contrast, Quot; 1 " to " ^{1 &} quot ;, no other part is interposed therebetween.

Although not defined differently, all terms including technical terms and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention belongs. Commonly used predefined terms are further interpreted as having a meaning consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or very formal meanings unless defined otherwise.

Unless otherwise noted,% means weight%, and lppm means

0.00 Duality% Idy -.

In an embodiment of the present invention, the meaning of further including additional elements means that alumina is replaced by an additional amount of additional elements. Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

Refractory composition

The refractory composition according to one embodiment of the present invention contains 15 to 30% of carbon, 5 to 15% of silica, 3 to 10% of carbon monoxide scavenger, and the balance alumina,

The carbon monoxide scavenger includes a metal carbide.

Specifically, the carbon monoxide collecting agent may include at least one of B ₄ C, AL, SiC, and CaC ₂ .

First, the reason for limiting the components of the refractory composition will be described below.

Carbon: 15 to 30 wt%

Carbon can improve refractory corrosion resistance and invasiveness (resistance to permeation) of molten steel and can reduce thermal damage. If the content of carbon is too low, the effect of improving corrosion resistance and invasiveness may be insignificant. On the other hand, if the content is too high, the modulus of elasticity of the refractory may be increased and the resistance of the heat resistant layer may be deteriorated. Therefore, the content of carbon is controlled to 15 to 30 wt%.

Specifically, the carbon may include at least one of flaky graphite, carbon black, and pitch.

The impression roll can reduce the wettability of the refractory to molten steel and slag, and increase the invasiveness and corrosion resistance. Carbon black can be contained in the refractory composition to increase the strength of the refractory. The pitch could be contained in the composition as well as carbon black to increase the strength of the refractory.

Silica: 5-15 wt%

Silica (silica) can impart fluidity to the refractory composition and improve bond strength. When the content of silica is too low, the effect of imparting fluidity and improving the strength may be insignificant. On the other hand, if the content is too high, the flowability of the refractory composition may be deteriorated. Alumina-silica-based A low melting point material could be generated and the hot strength could be lowered. Therefore, the content of silica is controlled to 5 to 15% by weight.

Carbon monoxide collecting agent: 3 to 10 wt%

The carbon monoxide collecting agent is a material for trapping carbon monoxide (CO) generated by the reaction of carbon and silica contained in the refractory composition when the refractory material is attached to the inner wall of the immersion nozzle for moving molten steel. As can be seen from FIG. 1, carbon monoxide generated in the refractory moves through the pores in the refractory to the interface between the molten steel and the refractory, and then oxidizes Al by countering with the A1 contained in the molten steel. The oxidized A1 may form now, such as network alumina, and may adhere to the refractory surface to cause nozzle clogging. This can be explained by the following Equation 1 and Equation 2.

However,

_{Si0 2 (s) + C (} s) = SiO (g) + C0 (g)

[HanWoong2] ·

2A1 + 3C0 (g) = Al 2 0 3 (s) + 3C

In order to prevent oxidation of Al by carbon monoxide, collecting carbon monoxide moving to the contact interface between the molten steel and the refractory may be a method for preventing nozzle clogging.

When the molten steel contains Al as well as Ti, various types of oxides can be formed as shown in FIG. 2. If the oxygen concentration is high, as shown in FIG. 3, Fe _t Ol ^' iO _x -Al ₂ O ₃ is formed. This liquid oxide can now act as a product cause.

Therefore, due to the presence of the carbon monoxide trapping agent contained in the refractory, carbon monoxide moving to the contact interface between the molten steel and the refractory material can be trapped and prevented from being generated.

The carbon monoxide scavenger is deoxidized with carbon monoxide as shown in Reaction Scheme 3 below, so that only carbon remains. ,

[Hanwoong 3] MC (s) + C0 (g) = M0 (s or 1) + C (s)

The carbon monoxide collecting agent includes a metal carbide. Specifically, the carbon monoxide collecting agent may include at least one of B ₄ C, ALA, SiC, and Ca. In addition, it may further include Al, Si, Mg, Al-Si alloy, Al-Mg alloy, and the like. When the content of the carbon monoxide capturing agent is too low, the carbon monoxide is not sufficiently collected and it is difficult to prevent the formation of the carbon monoxide present. On the other hand, if the content of the carbon monoxide scavenger is too high, the resistance of the heat resistant layer may deteriorate or the corrosion resistance may deteriorate. Therefore, the content of the carbon monoxide trapping agent is controlled to 3 to 10 wt%. This can be confirmed from FIG.

The remainder can be made of alumina (alumina oxide). It is a refractory material to increase corrosion resistance to molten steel and slag. Specifically, fused alumina can be used.

In addition to alumina, ¾ of calcia (calcium oxide) and

10 to 20% by weight of zirconia (zirconia).

The calcia can form a liquid oxide having a low melting point by bonding with alumina in the molten steel adhering to the inner part of the nozzle and the discharge part.

Zirconia increases the corrosion resistance to slag, and is combined with calcia, which is essential for self-cleaning material refractory materials, to be present in refractory materials in CaZrO ₃ form.

Specifically, regarding the carbon monoxide trapping agent, the carbon monoxide trapping agent may have a negative Gibbs energy change value (AG) at 1500 to 1550 ^° C due to reaction with carbon monoxide in a gas state.

The temperature of the refractory attached to the inner wall of the immersion nozzle converged to the temperature of the molten steel. The temperature of the refractory could therefore be between 1500 and 1550 ^° C.

In this same temperature under an atmosphere of carbon monoxide trapping agent banung and ^'carbon monoxide in the gaseous phase resulting from the refractory material in order to effectively collect the carbon monoxide has to be a Gibbs free energy change value (AG) is negative.

As can be seen from the graph of FIG. 4, 155 (which may be in the TC B ₄ C, AI4C3 and CaC ₂ are both free energy change value (AG) cast is shown the negative seen that suitable as a carbon monoxide scavenger under the atmosphere, while, in the case of SiC, 1500 to 1550 ^° At lower temperatures than C, the Gibbs free energy change value (AG) is negative, but since it has a positive value at 1500 to 1550 ^° C, the carbon monoxide capture ability is lower than that of B ₄ C, AI ₄ C3 and CaC ₂ .

Concretely, regarding the composition of the refractory composition according to one embodiment of the present invention, the following formula 1 can be satisfied.

[Formula 1]

0.23 < [carbon monoxide scavenger] / [silica] 1

As shown in Equation 1, one carbon monoxide molecule per one silica molecule is formed. Six molecules of the carbon monoxide thus formed are trapped in a single carbon monoxide trapping molecule as shown in the following Equations 4 and 5. In this case, four metal atoms contained in the carbon monoxide trapping agent in the form of metal carbide are separated from six carbon monoxide Lt; / RTI >

However,

B ₄ C (s) + 6C0 (g) = 2B ₂ 0 ₃ (1) + 7C (s)

[Hanwoong 5]

A1 ₄ C ₃ (S) + 6C0 (g) = 2Al ₂ O ₃ (s) + 9C (s)

Therefore, it is possible to control the composition so as to have an optimum composition ratio of silica and carbon monoxide scavenger by controlling the ratio of the content of the carbon monoxide scavenger to the silica content through the formula 1.

When [carbon monoxide trapping agent] / [silica] is less than 0.23, it is difficult to prevent the formation of carbon monoxide from the refuse so that the formation of carbon monoxide is not carried out. On the other hand, if it exceeds 1, the thermal shock resistance may deteriorate or the corrosion resistance may deteriorate.

An organic binder is added to the refractory composition composed of the above-mentioned components and used. The organic binder to be added at the time of use may be a thermosetting resin have.

The immersion nozzle according to an embodiment of the present invention is an immersion nozzle in which molten steel is moved from a tundish to a mold with reference to FIG. Wherein at least the portion in contact with the molten steel comprises a nozzle body (100) made of a refractory composition, and the refractory composition is in an increased percentage. 15 to 30% of carbon, 5 to 15% of silica, 3 to 10% of carbon monoxide scavenger, and the remaining alumina, and the carbon monoxide scavenger includes metal carbide (carba i de).

Specifically, the carbon monoxide collecting agent is C.I. AI ₄ may include C3, C Si and one or more of CaC _2.

In the process of moving the molten steel to the mold for continuous ^casting, from a tundish for receiving molten steel from the ladle is supplied, is made of molten steel supplied to the mold through the nozzle body 100 is formed on the tundish bottom. At least a portion of the nozzle body 100 in contact with molten steel is made of a refractory composition having the above composition.

Since the composition of the refractory composition fire is the same as that of the above-mentioned refractory composition, repeated description will be omitted.

When the refractory composition further contains calcia and zirconia, a CaZr combined with calcia and zirconia is present in the nozzle body 100 made of the refractory composition.

Molten steel could contain A1 and Ti. Since C0 (g) can be continuously supplied to the contact interface 200 between the molten steel and the refractory by the above reaction formula 1, the oxygen concentration of the contact interface 200 may increase to 500 ppm. Al and Ti coexist in the steel. As shown in FIG. Various types of oxides can be formed, and if the oxygen concentration is high, a liquid oxide composed of Fe _t 0 -Ti () _x -Al ₂ O ₃ is formed. This liquid oxide can now act as a product cause.

Therefore, due to the presence of the carbon monoxide capturing agent contained in the refractory composition, carbon monoxide moving to the interface 200 with the molten steel can be trapped to prevent the present generation. Specifically, the nozzle body 100 may be in contact with molten steel, and may include an inner rim 110 made of a refractory composition and a discharging part 120 made of a refractory composition through which molten steel is discharged.

The inner layer 110 and the discharging part 120 in which the nozzle clogging phenomenon frequently occurs are made of a refractory composition containing a carbon monoxide capturing agent, so that carbon monoxide capture can be actively performed.

On the other hand, the concentration of the carbon monoxide capturing agent may be increased toward the contact interface 200 where the nozzle body 100 is in contact with molten steel.

As can be seen in Fig. Carbon monoxide generated in the nozzle body 100 composed of the refractory composition reaches the interface 200 with the molten steel along the pores, causing a problematic problem. Therefore, it is advantageous to collect carbon monoxide moving in the direction of the contact interface 200 when the density of the trapping agent increases toward the contact interface 200 of the nozzle body 100. That is, even when the same amount of carbon monoxide capturing agent is applied, the density of the carbon monoxide capturing agent near the contact interface 200 is relatively high, thereby effectively preventing the occurrence of the present.

Hereinafter, specific examples of the present invention will be described. However, the following examples are only a concrete example of the present invention, and the present invention is not limited to the following examples.

Example

The refractory compositions of Comparative Example 1, Comparative Example 2, Example 1 and Example 2 having the composition shown in the following Table 1 were prepared and sintered in the form of pellets, then placed in an alumina crucible, and an alloy containing Al and Ti . The crucible containing the sample was heated at 1560 ^° C using an induction furnace in a refined argon atmosphere, and then cooled for 2 hours and then cooled. Di were measured for the refractory surface and the average thickness banung water formed between the molten steel is made in contact with molten ^steel,. The results are shown in Table 2.

In addition, the refractory compositions of Comparative Examples 3 and 3 having the compositions shown in Table 1 were prepared and subjected to an immersion rotation reaction with molten steel containing Al and Ti. The molten steel contains 500 ppm of Ti, 800 ppm of Al, 400 ppm of O, the balance Fe, Impurities.

After the rotation reaction, the average thickness formed on the refractory surface, that is, the contact interface, which was in contact with the molten steel, was measured. Also, through experiments with magnet attachment. It was confirmed whether or not magnetism was present in the water. The results are shown in Table 3.

[Table 1]

[Table 3]

. As can be seen from Table 2 and FIG. 6, in the case of Comparative Example 1 and Comparative Example 2, it was confirmed that the carbon monoxide was not collected or collected sufficiently, and the amount of reactant was large. On the other hand, in the case of Example 1 and Example 2, carbon monoxide was collectively collected and the amount of reactant produced was relatively small. Since it is impossible to confirm whether or not it is attached only by the above Comparative Example 1, Comparative Example 2, Example 1 and Example 2, The rotation immersion experiment was carried out.

In Comparative Example 3, it was confirmed that the sample including the metal oxide such as alumina is present because of the magnetism due to the adhesion of the metallic substance by the interface reaction as a result of the rotational immersion test of the specimen processed with the immersion nozzle. As in Fig. 7, in the case of Comparative Example 3, now including the metal oxide at the contact interface was observed. On the other hand, in the case of Example 3, as shown in FIG. 8, the water was observed, but it was found that it contained only a trace amount of metal oxide or not to be attached to the magnet.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims and their equivalents. It will be understood that the invention may be embodied in other specific forms without departing from the spirit or scope of the invention. It is therefore to be understood that the embodiments and / or the examples described above are illustrative in all aspects and not restrictive.

[Description of Symbols]

100: nozzle body

110: My study

120:

200: contact interface

Claims

Claims:

[Claim 1]

By weight, carbon: 15 to 30%, silica: 5 to 15%, carbon monoxide scavenger: 3 to 10%, and the balance alumina,

Wherein the carbon monoxide trapping agent comprises a metal carbide.

[Claim 2]

The method according to claim 1,

The carbon monoxide collecting agent is:

Wherein the Gibbs free energy change value (AG) at 1500 to 1550 ^° C according to reaction with C0 (g) is negative.

[Claim 3]

The method according to claim 1,

The carbon monoxide collecting agent is:

B ₄ C, AI C, Si C, and CaC ₂ .

Claim 4

The method of claim 3,

The above-

B ₄ C, and 3 to 10%.

[Claim 5]

The method according to claim 1,

Wherein the refractory composition satisfies the following formula (1).

[Formula 1]

0.23 <[carbon monoxide scavenger] / [silica] <1

(In the formula (1), [silica] and [carbon monoxide collecting agent] represent the content (weight%) of each silica fine silica and carbon monoxide collecting agent.

[Claim 6]

An immersion nozzle in which molten steel is moved from a tundish to a mold, wherein at least a portion of the molten steel in contact with the molten steel is a refractory composition,

The refractory composition, By weight, carbon: 15 to 30%, silica: 5 to 15%, carbon monoxide scavenger: 3 to 10%, and the balance alumina,

Wherein the carbon monoxide trapping agent comprises metal carbide.

7.

The method according to claim 6,

The carbon monoxide collecting agent is:

B ₄ C, Al ₄ C _{: i} , at least one of SiC and CaC ₂ .

[8]

7. The method of claim 6, wherein.

Wherein,

A1, and Ti.

[Claim 9]

The method according to claim 6,

The nozzle body includes:

Wherein the refractory composition is in contact with the molten steel,

And a discharge part made of the molten steel and made of the refractory composition.

Claim 10

. The method according to claim 6,

The nozzle body includes:

Wherein the molten steel has a concentration gradient such that the concentration of the carbon monoxide capturing agent becomes higher toward the catalyst interface at which the molten steel is supplied.