KR101412922B1 - Evaluation method for molten steel and refractories reactivity - Google Patents

Abstract

The present invention relates to a method of evaluating reactivity of molten steel and a refractory, comprising: a refractory preparation step of preparing a refractory using the refractory; A molten steel heating step for heating the molten steel by providing the molten steel to the reaction part; an iron alloy input step for injecting the molten iron after the molten steel is heated; A molten steel-refractory reaction step in which the refractory is immersed in molten steel into which the alloy iron is injected and then the refractory is rotated to react with the molten steel; And a reaction confirming step of analyzing the refractory after lowering the temperature of the molten steel after completion of the reaction between the molten steel and the refractory.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating reactivity of molten steel and refractory,

The present invention relates to a method for evaluating the reactivity of molten steel and refractory, and more particularly, to a method for evaluating reactivity of molten steel and refractory by reflecting the actual behavior between molten steel and refractory, And the like.

Since the molten steel is generally reacted and moved in a high temperature state in the continuous casting process, the inside of the apparatus for receiving the molten steel and the molten steel or for passing the molten steel is made of refractory. As the continuous casting process proceeds, a part of the molten steel reacts with the refractory material to form inclusions. For example, the tundish provided with molten steel is provided with a nozzle at its bottom, and the molten steel is moved to the mold through the nozzle and is continuously cast. At this time, the inclusion formed by the reaction of the molten steel and the refractory inside the nozzle causes the clogging cause. The clogging of the nozzles in the continuous casting process causes a great loss in the process and safety problems such as the occurrence of industrial accidents during the replacement of the nozzles.

Therefore, in order to prevent this, a method has been used in which the reactivity of the molten steel and the refractory is checked, and the components of the refractory according to the characteristics of the molten steel are determined in advance and applied to the nozzle. Conventionally, molten steel was placed in a crucible and heated to dissolve the molten steel, and then the refractory was added to the molten molten steel to check the reactivity between the molten steel and the refractory. At this time, the refractory is not immersed in the molten steel due to the difference in specific gravity between the molten steel and the refractory, so that it is difficult to precisely confirm the reactivity between the molten steel and the refractory. In addition, since the above evaluation method is a static reaction between the molten steel dissolved in the crucible and the refractory, a substantial reactivity between the molten steel passing through the nozzle and the refractory at the speed of continuous casting, that is, There is a problem that it is difficult to reproduce the adhesion characteristics of inclusions as they are.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for evaluating the reactivity of molten steel and refractories capable of identifying clogging of a nozzle caused in a continuous casting process.

Another object of the present invention is to provide a method for evaluating the reactivity of molten steel and refractories, which can identify the mechanism of reacting molten steel with refractories in consideration of the flow of molten steel in a continuous casting process and the actual continuous casting process.

According to an aspect of the present invention, there is provided a method of evaluating reactivity of a molten steel and a refractory, comprising: refractory preparation step of processing and refining the refractory; A molten steel heating step of raising the temperature of the molten steel to a reaction temperature after the molten steel is provided in the reaction part, the step of injecting ferroalloy into the molten steel; A molten steel-refractory reaction step of immersing the first part of the refractory in the molten steel and then rotating the refractory to react with the molten steel; And a reactivity determining step of analyzing the refractory after lowering the temperature of the molten steel after completion of the reaction between the molten steel and the refractory.

In the refractory preparation step, the refractory may be manufactured by processing into a cylindrical shape, and the refractory formed in a cylindrical shape may be preheated and decarburized.

The refractory may be heated to a temperature of 800 ° C to 1000 ° C in an air atmosphere.

In the molten steel heating step, the temperature of the molten steel is sequentially increased to the first and second steps, and the second step may be heated to the reaction temperature.

The temperature of the molten steel may be increased from room temperature to 1000 ° C for 30 minutes in the first step and from 1000 ° C to 1500 ° C for 20 minutes in the second step.

In the molten steel heating step, the molten steel is provided in the reaction part, and the refractory may be provided at an upper portion of the molten steel and spaced apart from the molten steel.

In the alloying iron addition step, the alloy iron may be introduced after maintaining the molten steel heated to the above reaction temperature for 5 to 15 minutes.

In the molten steel-refractory reaction step, the refractory is provided in a cylindrical shape, and the first portion of the refractory may be 15 mm to 20 mm at the bottom of the cylindrical shape.

In the molten steel-refractory reaction step, the refractory may be rotated at a speed of 50 rpm to 200 rpm.

In the reactivity checking step, it is possible to analyze the deposit attached to the outside of the refractory after the temperature of the molten steel is lowered, and the molten steel after the reaction with the refractory.

Wherein in the step of confirming the reactivity, the deposit adhering to the refractory is separated to evaluate the thickness of the deposit, the composition of the deposit, and the strength with which the deposit adheres to the refractory, and the molten steel, after solidification of the molten steel, , The composition and number of the inclusions can be evaluated.

As described above, according to the present invention, it is possible to provide a method for evaluating the reactivity of molten steel and refractory which can identify the clogging phenomenon of a nozzle occurring in a continuous casting process.

In addition, according to the present invention, it is possible to provide a method for evaluating reactivity of molten steel and refractories, which can identify the mechanism of the reaction of molten steel and refractory by reflecting the flow of molten steel and the actual continuous casting process in the continuous casting process.

1 is a flow chart showing a method for evaluating reactivity of molten steel and refractories according to the present invention.
2 is a schematic view of an apparatus for evaluating the reactivity of molten steel and refractories according to the present invention.
3 is a perspective view of a device for evaluating reactivity of molten steel and refractory according to the present invention.
4 is a graph schematically showing the temperature change of molten steel and refractory according to the present invention.
5A is a schematic view showing a treatment method for evaluating refractories and deposits according to the present invention.
5B is a schematic view showing a treatment method for evaluating molten steel according to the present invention.
Fig. 6 is a view of a refractory processed into a reactive pre-evaluation cylinder according to the present invention. Fig.
7 is a photograph showing the refractory after the evaluation of the reactivity according to the comparative example.
8 is a photograph showing the refractory after the reactivity evaluation according to Examples 1 to 3;
9 is a photograph showing the molten steel after the evaluation of the reactivity according to Examples 1 to 3. Fig.
10 shows the results of evaluation of refractories and deposits after the reactivity evaluation according to Example 1. Fig.
11 shows the results of evaluation of refractory materials and deposits after the reactivity evaluation according to Example 2. Fig.
12 shows the results of evaluation of refractory materials and deposits after the reactivity evaluation according to Example 3. Fig.
13 is a result of evaluation of molten steel after the evaluation of the reactivity according to Example 1. Fig.
14 is a result of evaluation of molten steel after the evaluation of the reactivity according to Example 2. Fig.
15 is a result of evaluation of molten steel after the evaluation of the reactivity according to Example 3. Fig.

The details of other embodiments are included in the detailed description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and the manner of achieving them, will be apparent from and elucidated with reference to the embodiments described hereinafter in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments described below, but may be embodied in various forms. In the following description, it is assumed that a part is connected to another part, But also includes a case in which other elements are electrically connected to each other in the middle thereof. In the drawings, parts not relating to the present invention are omitted for clarity of description, and like parts are denoted by the same reference numerals throughout the specification.

Hereinafter, the present invention will be described with reference to the accompanying drawings.

1 is a flowchart showing a method for evaluating reactivity of molten steel and refractories according to the present invention. FIG. 2 is a schematic view of an apparatus for evaluating the reactivity of molten steel and refractories according to the present invention, and FIG. 3 is a perspective view of an apparatus for evaluating reactivity of molten steel and refractories according to the present invention.

Referring to FIG. 1, the present invention provides a method of evaluating reactivity of molten steel and refractories, comprising: a refractory preparation step (S1) of processing and pre-treating the refractory; A step (S2) of heating the molten steel to raise the temperature of the molten steel to a reaction temperature after the molten steel is provided in the reaction part; (S3) an iron-making step of injecting ferroalloy into the molten steel; A molten steel-refractory reaction step S4 of immersing the first portion of the refractory in the molten steel and then rotating the refractory to react with the molten steel; (S5) of analyzing the refractory after the temperature of the molten steel is lowered after the completion of the reaction between the molten steel and the refractory. The present invention also relates to a method for evaluating reactivity of molten steel and refractories.

The above reactivity evaluation methods are largely classified into three stages, namely, a pre-reaction evaluation step (processing and pretreatment of refractory), a reaction evaluation step (deoxidization of molten steel and confirmation of reactivity of molten steel and refractory) The refractory preparation step S1 is included in the pre-reaction evaluation stage, and the molten steel heating step S2, the ferroalloy feeding step S3 and the molten steel-refractory reaction step S4 are included in the reactivity evaluation step , And the reactivity confirmation step (S5) may be included in the post-reactivity evaluation step.

In the refractory preparation step (S1), the refractory (s) can be manufactured by processing into a cylindrical shape. The cylindrical refractory (s) may be preheated and the refractory (s) may be decarbonized by preheating. The refractory s may be made of the same or similar material as the material of the immersion nozzle through which the molten steel m passes during the continuous casting process. For example, the refractory s may be a spinel-graphite alumina- Graphite, Al2O3-graphite, or the like. The refractory s may be processed into a cylindrical shape having a size of 60 (mm) * 10 (PHI).

The refractory (s) may be heated in an air atmosphere using an atmospheric furnace or the like, for example, at a temperature of 800 ° C to 1000 ° C, and the heating may be performed for 8 hours to 10 hours. If the temperature is less than 800 ° C, the decarbonization time of the refractory is increased to lower the process efficiency, and the temperature must be maintained for a long time, thereby increasing the cost. On the other hand, when the temperature is 1000 ° C, the refractory is melted rather than removing only carbon in the refractory. The heating time is preferably 8 hours to 10 hours. If the heating time is less than 8 hours, the decarburization of the refractory material is incompletely performed. If the heating time is visually checked, black (carbon) remains in the refractory material. can confirm. If it exceeds 10 hours, the refractory may be damaged by heating for a long time. Therefore, the heating of the refractory material is preferably performed at 800 ° C to 1000 ° C for 8 to 10 hours. It is further preferable that the heating of the refractory material is performed at 1000 DEG C for 10 hours. This is because the carbon in the refractory can be completely removed in the state where the refractory is not deformed when heated at 1000 ° C for 10 hours. The temperature and time for preheating the refractory (s) can be applied to simulate preheating of the immersion nozzle during continuous casting and to confirm the reactivity of the molten steel (m) and refractory (s) similarly to the actual operation.

The reactivity evaluation method according to the present invention can be performed by the apparatus 10 for evaluating the reactivity of molten steel and refractory shown in FIG. 2, wherein the apparatus 10 for evaluating reactivity of molten steel and refractory comprises a reaction unit (100); A control unit 200 for controlling the reaction unit 100; A power supply unit 300 for supplying power to the reaction unit 100; And a heat exchange medium supply unit 400 for supplying the reaction unit 100 and the heat exchange medium. The control unit 200 may control the temperature raising conditions of the molten steel, the reaction time of the molten steel and the refractory in the reaction unit 100, and the like. The power supply unit 300 may apply power to the reaction unit 100 and the heat exchange medium supply unit 400 may supply the heat exchange medium such as cooling water to the reaction unit 100 and the power supply unit 300 And can exchange heat with the reaction unit 100 and the power supply unit 300. For example, the reaction unit 100 may include an induction furnace.

Referring to FIGS. 2 and 3, the reaction unit 100 includes a reaction tube 110 having an upper portion and a lower portion opened at one side thereof and a space therein. A cap member 130 covering the reaction tube 100 at an upper portion of the reaction tube 100; An induction coil 140 installed to surround the reaction tube 110 on the outer surface of the reaction tube 110; And a crucible 111 provided inside the reaction tube 110 to receive molten steel and refractory. The reaction unit 100 further includes a carbon heating body 112 enclosing the crucible 111 inside the reaction tube 110. The carbon heating body 112 is connected to the induction coil 140 And a support member 113 for supporting the carbon heating element 112 at a lower portion of the carbon heating element 112 may be provided.

The power supply unit 300 can generate an induction electromotive force by applying power to the induction coil 140, which can raise the temperature of the carbon heating element 112. The temperature of the heated carbon heating element 112 can increase the temperature of the crucible 111 placed in the carbon heating element 112 by heat transfer and the molten steel m provided in the crucible 111. The crucible 111 may be made of aluminum oxide (Al ₂ O ₃ ), and the carbon heating element 112 may be provided in a container form to receive the crucible 111. The support member 113 may be made of a refractory material and support the reaction tube 111 at a lower portion of the reaction tube 110. A lower thermocouple (T / C) 114 may be provided under the carbon heating element 112 to measure the temperature of the carbon heating element 112. The lower thermocouple 114 may be connected to the controller 200 to control the temperature of the carbon heating element 112. The lower thermocouple 114 may be provided to pass through the support member 113.

The reaction tube 110 may be made of a transparent material, which is transparent and visible to the operator. Therefore, the worker can confirm the process of reacting the molten steel with the refractory. And a cap member 130 provided to cover the reaction tube 110 at an upper portion of the reaction tube 110. The cap member 130 may be connected to the control unit 200 to be movable up and down by a lift (not shown) or the like. The cap member 130 may be formed to have a size corresponding to the reaction tube 110. The cap member 130 may have a bar-shaped connecting rod 152 for fixing the refractory s, An inlet pipe 170 for inputting ferroalloy and an upper thermocouple 160 for measuring the temperature of the molten steel m in the crucible 111 may be provided. The upper thermocouple 160 can directly measure the temperature during the reaction of the molten steel m and the refractory s and confirms the temperature difference controlled by the lower thermocouple 114 using the upper thermocouple 160, The reaction temperature can be precisely controlled so as to be similar to the actual continuous casting process.

The connecting rod 152 may protrude from the cap member 130 toward the reaction tube 110 and a connecting rod 1520 may be provided at one end thereof with a rotating motor (not shown) for rotating the connecting rod 152 And the refractory s may be fixed to the other end of the connecting rod 152. In addition, since the connecting rod 152 can be separated, the length of the connecting rod 152 can be varied. The refractory s is difficult to deposit in the molten steel m due to the difference in specific gravity between the refractory a and the molten steel m made of the refractory and the reactivity of the immersion nozzle and the molten steel through which the molten steel passes It was difficult to accurately identify. On the other hand, in the case of the present invention, the refractory s can be easily deposited in the molten steel m through the vertical movement of the cap member 130 and the control of the length of the connecting rod 152, s) can be accurately confirmed.

The molten steel s may be provided in the reaction part 100 and the refractory s may be provided on the molten steel m so as to be spaced apart from the molten steel m. That is, before the molten steel m is melted, the refractory s is spaced apart from the molten steel m, and the refractory s is transferred to the heat transmitted through the induction coil 140 and the carbon heating element 112 of the reaction tube 110 The refractory s may be deposited into the molten steel m after a predetermined process such as melting the molten steel m.

FIG. 4 is a graph schematically showing changes in temperature of molten steel and refractories according to the present invention. FIG.

Referring to FIG. 4, in the molten steel raising step S2, the temperature of the molten steel m is gradually raised to the first and second stages, and may be raised to the reaction temperature in the second stage. For example, the temperature of the molten steel m may be increased from room temperature to 1000 ° C for 30 minutes (t1) in the first step, and from 1000 ° C to 1500 ° C for 20 minutes (t2) in the second step.

In the alloying iron injection step (S3), the ferroalloy may be introduced to deoxidize the molten steel. For example, the ferroalloy may include at least one of Al, Ti, Ca, Ce, and Ca-Si. For example, when Al, Ce, and Ca-Si are introduced, Al → Ca-Si → Ce may be sequentially injected. The ferroalloy may be introduced after maintaining the molten steel heated to the reaction temperature (for example, 1500 DEG C) for 5 minutes to 15 minutes. When the molten steel is maintained for less than 5 minutes and the alloy steel is charged, the entire temperature of the molten steel is not uniformly 1500 ° C., so that the alloy iron which is supplied to the molten steel and deoxidizes the molten steel may partially exhibit different reactivity. On the other hand, if the time is 15 minutes, the inside of the molten steel sufficiently reaches 1500 DEG C and the molten steel composition becomes uniform as a whole. If the time exceeds 15 minutes, the unnecessary reaction time is increased and the process efficiency may be lowered. Therefore, it is preferable that the molten steel heated to 1500 ° C is maintained for 5 minutes to 15 minutes so as to have a uniform composition and a uniform temperature as a whole, and then the alloy iron is injected. After the alloy iron is charged, the refractory is immersed in the molten steel, and for example, the molten steel and the refractory can react for about 30 minutes. The molten steel m and the refractory s can react for a predetermined time t3 while maintaining the reaction temperature and the temperature of the molten steel m can be lowered after the reaction.

In the molten steel-refractory reaction step (S4), the degree of reaction can be confirmed by reacting the molten steel (m) with the refractory (s). The molten steel m may be provided in the crucible 111 and then the temperature of the molten steel m may be raised to the reaction temperature so that the ferroalloy may be introduced into the molten steel m in a similar manner . After the alloying iron is charged, the refractory (s) may be reacted with the molten steel by rotating the refractory (s) after depositing the first portion (1) of the refractory (s) in the molten steel (m).

In the molten steel-refractory reaction step, the refractory (s) is provided in a cylindrical shape, and the first portion (l) of the refractory (s) To 20 mm. The first portion 1 of the refractory s is a portion where the molten steel m and the refractory s are in direct contact with each other. When the length of the first portion 1 is less than 15 mm, And the contact area of the refractory (s) are so narrow that it is difficult to precisely confirm the actual reactivity of the molten steel (m) and the refractory (s). That is, the amount of the molten steel (m) and the refractory (s) reacted is too small to be separated and analyzed. If the length of the first portion 1 is 20 mm, the reactivity between the molten steel m and the refractory s can be sufficiently confirmed. If the length of the first portion 1 exceeds 20 mm, Since the size of the reaction part 100 for evaluating the reactivity of the molten steel m and the refractory s is also increased since the size of the refractory s provided in the refractory 152 is unnecessarily increased, And an increase in cost.

The refractory (s) can be rotated at a speed of 50 rpm to 200 rpm. The rotation speed of the refractory (s) is less than 50 rpm and the reactivity of the molten steel (m) and the refractory (s) is lower than that generated in actual continuous casting. If the rotation speed of the refractory (s) is more than 200 rpm, the reflux (s) causes a large eddy in the molten steel (m) . Further, it is difficult for the refractory (s) to be sufficiently deposited on the molten steel (m) at the same time, so that it is difficult to confirm the correct reactivity. That is, when the rotation speed of the refractory (s) is less than 50 rpm or exceeds 200 rpm, the speed at which the molten steel passes through the immersion nozzle in actual continuous casting is not sufficiently reflected, so that it is difficult to clearly identify the reactivity occurring in actual operation . The rotation speed of the refractory (s) reflects the casting speed (peripheral speed) flowing out through the immersion nozzle in the actual continuous casting operation, wherein the 50 rpm corresponds to the slowest rotation in the actual continuous casting operation, It can correspond to the state. Therefore, in case of intermediate speed during continuous casting work, it may correspond to a rotation speed of 125 rpm which is an intermediate rotation speed between 50 rpm and 200 rpm.

Generally, as a method of evaluating the reactivity between molten steel and refractory, a predetermined temperature is maintained for a predetermined time with iron alloy and refractory just dipped in a crucible containing molten molten steel. Since the alloy iron must be injected into the molten steel at the same time as the refractory, it is difficult to precisely simulate the behavior of the ferroalloy introduced in the middle of the actual operation, and the refractory is not immersed deeply into the molten steel due to the difference in specific gravity between the refractory and the molten steel, It was difficult to evaluate the reactivity. Also. Since the molten steel passes through the immersion nozzle at a constant velocity during the continuous casting process, refractory material in the molten steel and the inner wall of the immersion nozzle reacts under dynamic conditions rather than in a static condition. On the other hand, There is a problem that it is difficult to reproduce.

On the other hand, in the method for evaluating reactivity of molten steel and refractory according to the present embodiment, the alloy iron may be introduced into the molten steel in the same order as the actual operation in consideration of the order and time of the alloyed iron using the alloy iron feed pipe . Since the first portion of the refractory is immersed in the molten steel at a predetermined depth, the problem caused by the specific gravity difference between the refractory and the molten steel can be solved, and the reactivity with the molten steel can be confirmed by rotating the refractory. The reactivity of the molten steel and refractories to the change of flow velocity can be clearly evaluated and reflected in the operation.

The flow rate of molten steel can be changed in actual continuous casting. In the method of evaluating the reactivity of molten steel and refractory according to the present invention, this can be reflected by changing the rotation speed of the refractory. The reactivity and correlation between the refractory and the molten steel can be identified before the actual continuous casting by varying the amount of the alloyed iron and the material of the refractory. In addition, when developing a new grade, it is possible to evaluate the reactivity between the refractory and the molten steel according to the composition of the steel, and to refine the refractory used in the apparatus such as the immersion nozzle beforehand, so that the productivity can be improved and the clogging of the immersion nozzle The phenomenon can be prevented in advance.

FIG. 5A is a schematic view showing a treatment method for evaluating refractories and deposits according to the present invention, and FIG. 5B is a schematic view showing a treatment method for evaluating molten steel according to the present invention.

In the reactivity checking step (S5), the deposit attached to the outside of the refractory after the temperature of the molten steel is lowered, and the molten steel after the reaction between the refractory and the refractory can be respectively analyzed. For example, the first part of the refractory material is preferably reacted with molten steel to adhere to the molten steel, and the molten steel also has a result of reaction with refractory and molten steel. For example, the deposit attached to the refractory is separated to evaluate the thickness of the deposit, the composition of the deposit, and the strength with which the deposit adheres to the refractory, and the molten steel has an average size of the inclusions in the molten steel, The composition and the number of the inclusions can be evaluated.

At this time, the refractory is cut in a direction perpendicular to the refractory with the adhered portion as a center, and the interface between the deposit and the refractory and the components of the deposit are analyzed using SEM-EDS. The behavior can be evaluated. After the molten steel is solidified, the molten steel in the metal state is cut in the longitudinal direction, and the components of the inclusions in the molten steel are analyzed using SEM-EDS. The size and number of the inclusions are analyzed using an electron microscope, The components of the cut specimen can be analyzed.

Hereinafter, examples and comparative examples of the present invention will be described. However, the following examples are only a preferred embodiment of the present invention, and the scope of the present invention is not limited by the following examples.

FIG. 6 is a view showing a refractory processed into the cylindrical shape of the reactive pre-evaluation according to the present invention, and Table 1 shows the evaluation conditions and the method according to the present embodiment.

As shown in Fig. 6, the refractory (Alumina-C) was processed into a cylindrical shape having a size of 60 mm * 10 (Φ), and in order to simulate preheating of the immersion nozzle used in actual operation, The refractory was prepared by decarburizing the carbon (C) in the refractory by preheating at 1000 DEG C for 10 hours. STS309Si is used as the molten steel, and the alloy iron which can deoxidize the molten steel may be composed of Al, Ca-Si and Ce.

First, 300 g of the molten steel is placed in a crucible of a reaction part, and the molten steel is melted using an induction furnace and an induction furnace including a carbon heating element. At this time, the molten steel may be divided into a first step and a second step, which are different temperature raising rates. In the first step, the temperature is elevated from room temperature to 1000 ° C for 30 minutes, and then to 1500 ° C in the second step for 20 minutes. The melted molten steel is maintained at 1500 ° C for about 10 minutes, and then alloy iron made of Al, Ca-Si, and Ce is introduced by using an alloy iron feed pipe. Al was added, stirred, and maintained for 2 minutes. After Ca-Si was added, stirring was continued for 2 minutes. Then, Ce was added, stirred, and then maintained for 2 minutes. At this time, the amounts of Al, Ca-Si and Ce added are as shown in Table 1.

After the alloying iron is completely charged, the connecting rod is adjusted so that the first portion of the refractory provided in the connecting rod is immersed in the molten steel. Further, the refractory is rotated at a speed of 100 rpm for about 30 minutes by using a rotary motor connected to the connecting rod. Therefore, molten steel and refractory material can react for about 30 minutes. At this time, the interior of the reaction part is formed in an Ar atmosphere, and the crucible is made of Al ₂ O ₂ material.

In the comparative example, the molten steel was heated to 1500 DEG C in the crucible, and Al, Ca-Si, and Ce, which are alloy iron, were then charged together with the refractory. In this case, the amount and temperature of molten steel, refractory, and ferroalloy were the same as those of the examples, but unlike the examples, the ferroalloys were fed together with the refractory at once, and the refractory was not rotated.

Ferroalloy (wt%) Molten steel Refractory Al Ca-Si Ce material Reaction temperature
(° C) material Rotation speed
(rpm) Comparative Example 0.02 0.002 0.03 STS309Si 1500 Alumina
(Alumina-C) - Example 1 0.02 0.002 0.03 STS309Si 1500 Alumina
(Alumina-C) 100 Example 2 0.02 0.001 0.03 STS309Si 1500 Alumina
(Alumina-C) 100 Example 3 0.02 0 0.03 STS309Si 1500 Alumina
(Alumina-C) 100

FIG. 7 is a photograph showing the refractory after the evaluation of the reactivity according to the comparative example, FIG. 8 is a photograph showing the refractory after the reactivity evaluation according to Examples 1 to 3, FIG. 9 is a photograph showing the refractory according to Examples 1 to 3 This is a photograph showing molten steel after evaluation.

Referring to FIG. 7, according to the comparative example, it was confirmed that the refractory material was floating in the molten steel due to the difference in specific gravity between the molten steel and the refractory material. Therefore, in the case of the comparative example, it was confirmed that the refractories were not sufficiently immersed in the molten steel, so that even though they were reacted at the same temperature and for the same time as in Examples 1 to 3, the reaction between the refractory and the molten steel hardly occurred.

On the other hand, referring to FIG. 8 and FIG. 9, it can be confirmed that the reactivity between the molten steel and the refractory sufficiently occurs in Examples 1 to 3, unlike the comparative example. The amount of Ca-Si introduced into the alloy iron was changed in Example 1 (a), Example 2 (b) and Example 3 (c), and the difference in the degree of reaction between molten steel and refractory . Although the alloy iron is a factor affecting the reactivity of the molten steel and the refractory, in the comparative example, since the method of inputting the alloy iron does not simulate actual operation and is put into the refractory together with the refractory, the influence of the reactivity of the molten steel and the refractory by the alloy iron I could not confirm it. On the other hand, in the method for evaluating reactivity of molten steel and refractory according to the present invention, the order of iron alloy input, the time of injection, and the like can be controlled similarly to the actual operation by the ferroalloy input tube provided in the cap member of the reaction part.

The results of the evaluation of the reactivity of the molten steel and the refractory according to the present invention will be specifically discussed with reference to FIGS. 10 to 15. FIG. Fig. 10 shows the results of evaluation of the refractories and deposits after the reactivity evaluation according to Example 1, Fig. 11 shows the results of evaluation of refractories and deposits after the reactivity evaluation according to Example 2, Fig. 12 shows the results of evaluation of refractories And the results of the evaluation of the attachment. Fig. 13 shows the results of evaluation of molten steel after the evaluation of reactivity according to Example 1, Fig. 14 shows the results of evaluation of molten steel after the evaluation of reactivity according to Example 2, Fig. 15 shows the results of evaluation of molten steel after the evaluation of reactivity according to Example 3 Results.

10 to 12, the sizes of the deposits adhered to the refractories of Examples 1 to 3 were compared with each other. In Example 1, the size of deposits was the smallest. In Example 3, I was able to confirm the greatness. The thickness of the adherend of Example 1 was approximately 1.8 mm or less, and the composition of the adherend was Al-Ca-Ce-O. In the case of Example 2, the thickness of the adhered material was about 2.5 mm or less, and the adhered material was Al-Ce-O. Further, in Example 3, it was confirmed that the thickness of the adherend was about 9 mm or less, which is four times greater than that of Example 1 and Example 2. In Example 3, it was confirmed that the composition of the deposit was Ce-O.

Referring to Figs. 13 to 15, molten steel after reacting with the refractory in Examples 1 to 3 was examined, and it was confirmed that the inclusion in molten steel was the largest in Example 1. Specifically, in Example 1, the average inclusion size is 3.53 μm and the composition of the inclusions is 70 wt% Al 2 O 3 - 30 wt% Ce 2 O 3. In Example 2, the average inclusion size is 3.12 μm and the composition of the inclusions is 77 wt% Ce2O3. In Example 3, the average inclusion size was 3.95 mu m, and the inclusion composition was 92% wtAl2O3-8 wt% Ce2O3. In addition, the number of inclusions was the largest in Example 1, the intermediate level in Example 2, and the smallest in Example 3.

When the refractory material corresponds to the inner wall of the immersion nozzle and the molten steel is used in the same molten steel in the actual operation using the conditions of the first to third embodiments, As a result, the tendency of adhering to the immersion nozzle of Example 1 was weak, while in Example 2, the adherence adhered to the immersion nozzle was relatively coarse But it was confirmed that the attachment tendency was strong. It was confirmed that the molten steel reflects the tendency of Examples 1 to 3 as well as the refractory.

In the above-described Embodiments 1 to 3, although the iron alloy composition was finely changed, it was confirmed that the difference between the results of the evaluation of the reactivity of molten steel and the refractory was remarkably different. In addition, it is confirmed that the experimental results applied in Examples 1 to 3 are almost reflected even in actual operation.

On the other hand, conventionally, it is difficult to control not only the conditions of the input of the ferroalloy but also the flow of the molten steel and the immersion degree of the refractory, so that there is inconsistency when the results of the evaluation of the reactivity of the molten steel and the refractory are reflected in the actual operation. Further, even after evaluating the reactivity of molten steel and refractory in the related art, the evaluation and analysis method of the results of the molten steel and the refractory have not been clearly established, and thus it has been difficult to apply it to practical operation.

In the case of the present invention, it was confirmed that the result of the reactivity evaluation of molten steel and refractory has a similar result to the actual operation, and the method also has an advantage that the continuous casting process can be reflected as it is. Therefore, the results of the evaluation of the reactivity of the molten steel and the refractory according to the present invention can be used to evaluate the effect of the molten steel, the refractory and the alloy, It is possible to predict the abrasion of the apparatus or the composition change due to the unexpected reaction. Therefore, it is possible to improve the process efficiency and to manufacture the expensive device efficiently, thereby reducing the cost. Further, the material of the immersion nozzle suitable for each type of molten steel can be selected and applied efficiently.

It will be understood by those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the foregoing detailed description, and all changes or modifications derived from the meaning and scope of the claims and the equivalents thereof are included in the scope of the present invention Should be interpreted.

100: reaction part 200: control part
300: Power supply unit 400: Heat exchange medium supply unit
110: reaction tube 130: cap member
140: induction coil 152: connecting rod
160: upper thermocouple 170: input tube

Claims (11)

As a method for evaluating the reactivity of molten steel and refractory,
A refractory preparation step of processing and refining the refractory;
Heating the molten steel to raise the temperature of the molten steel to a reaction temperature to melt the molten steel after the molten steel is provided in the reaction part;
An alloy iron feeding step of feeding alloy iron into the molten steel for deoxidizing the molten iron;
A molten steel-refractory reaction step of immersing the first part of the refractory in the molten steel and then rotating the refractory to react with the molten steel; And
And a reactivity checking step of analyzing the refractory after lowering the temperature of the molten steel after completion of the reaction between the molten steel and the refractory,
In the refractory preparation step, the refractory is processed into a cylindrical shape, and the cylindrical refractory is preheated and decarburized to be pre-treated, thereby evaluating the reactivity of the refractory. delete The method according to claim 1,
Wherein the refractory is heated to a temperature of 800 to 1000 占 폚 in an air atmosphere. The method according to claim 1,
In the molten steel heating step,
Wherein the temperature of the molten steel is gradually raised to the first and second stages and the temperature is raised to the reaction temperature in the second stage. 5. The method of claim 4,
In the molten steel heating step,
Wherein the temperature of the molten steel is elevated from room temperature to 1000 캜 for 30 minutes in the first step and elevated from 1000 캜 to 1500 캜 for 20 minutes in the second step. The method according to claim 1,
In the molten steel heating step,
Wherein the molten steel is provided in the reaction part, and the refractory is provided at a distance from the molten steel at an upper part of the molten steel. The method according to claim 1,
In the ferroalloy feeding step,
Wherein the alloy iron is charged after maintaining the molten steel heated to the reaction temperature for 5 minutes to 15 minutes. The method according to claim 1,
In the molten steel-refractory reaction step,
Wherein the refractory is provided in a cylindrical shape and the first portion of the refractory is a portion of 15 mm to 20 mm from the lower surface of the cylindrical shape. The method according to claim 1,
In the molten steel-refractory reaction step,
Wherein the refractory is rotated at a speed of 50 rpm to 200 rpm. The method according to claim 1,
In the step of confirming the reactivity,
A method for evaluating the reactivity of molten steel and a refractory for analyzing a deposit adhering to the outside of the refractory after lowering the temperature of the molten steel and a molten steel having undergone reaction with the refractory. 11. The method of claim 10,
In the step of confirming the reactivity,
Wherein the deposit attached to the refractory is separated to evaluate the thickness of the deposit, the composition of the deposit, and the strength with which the deposit adheres to the refractory, wherein the molten steel has an average size of the inclusions in the molten steel, And evaluating the composition and the number of the refractories.

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