KR101707307B1

KR101707307B1 - Method of manufacturing steel prventing clogging of subemrged entry nozzle

Info

Publication number: KR101707307B1
Application number: KR1020150057649A
Authority: KR
Inventors: 장철호; 김해곤; 박근호
Original assignee: 현대제철 주식회사
Priority date: 2015-04-24
Filing date: 2015-04-24
Publication date: 2017-02-15
Also published as: KR20160126516A

Abstract

A method of manufacturing a steel that prevents clogging of an immersion nozzle according to an embodiment is disclosed. In the method of manufacturing the steel, CaS is injected into the molten steel in the refining process. The oxidizing agent is injected into the molten steel in the tundish during the casting process to generate the liquid CaO from the CaS to suppress the adhesion or growth of CaS inclusions on the inner wall of the tundish immersion nozzle.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of manufacturing a steel for preventing clogging of an immersion nozzle,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of manufacturing a steel, and more particularly, to a method of manufacturing a steel that prevents clogging of the immersion nozzle.

Generally, the steel production process uses a steel-rolling-correction process. Particularly, in the case of special steel, if the steelmaking process is subdivided into electric furnace process - ladle process - degassing process - performance process. As a specific example, first, after scrap iron is melted in an electric furnace process, a temperature raising operation, a desulfurization, and a deoxidizing operation are performed in a ladle process. After that, the degassing (oxygen, nitrogen, hydrogen) work is performed through the degassing process, and semi-finished products are produced through the performance process.

On the other hand, special steels are required as clean steel with few inclusions in the material due to the nature of its application. On the other hand, inclusions that inhibit the cleanliness of the steel can be generated by the immersion nozzle clogging phenomenon in the performance process. When large inclusions adhered to the immersion nozzle are separated from the immersion nozzle, hunting occurs in the mold for continuous casting, and the large size inclusions are formed in the casting mold, It can proceed to the process of incorporating the inclusions. Therefore, there is a need to prevent clogging of the immersion nozzle, and related prior arts include Korean Patent Publication No. 2011-0109316 (published on October 10, 2011, entitled " Device for preventing clogging of immersion nozzle in continuous casting, Immersion nozzle clogging prevention method).

The present invention provides a method of manufacturing a steel capable of suppressing clogging of an immersion nozzle by an inclusion.

A method of manufacturing a steel for preventing clogging of an immersion nozzle according to one aspect of the present invention is disclosed. In the method of manufacturing the steel, CaS is injected into the molten steel in the refining process. The oxidizing agent is injected into the molten steel in the tundish during the casting process to generate the liquid CaO from the CaS to suppress the adhesion or growth of CaS inclusions on the inner wall of the tundish immersion nozzle.

In one embodiment, the step of introducing CaS may proceed during the vacuum degassing step of the molten steel.

In another embodiment, the amount of CaS introduced may be determined in consideration of the content of sulfur in the produced steel.

In another embodiment, when the content of sulfur in the produced steel is 100 to 700 ppm, the amount of CaS may be 0.4 to 2.7 kg per ton of molten steel.

In another embodiment, the oxidizing agent is FeO, and the amount of FeO may be maintained at a ratio of 0.5 to 1.0 as compared to the amount of CaS introduced.

In another embodiment, the FeO may convert CaS in the form of inclusions in the molten steel to liquid CaO.

In yet another embodiment, the FeO reacts with the input CaS to produce liquid CaO, and the resulting CaO in the liquid phase can inhibit the growth of CaS in the form of inclusions in the melt.

According to the embodiment of the present invention, CaS in the form of inclusions present in the molten steel after refining is converted into liquid CaO, or the CaO concentration in the liquid phase is increased by the reaction of CaS and FeO introduced separately, Or the growth of CaS inclusions into large inclusions can be suppressed. As a result, occurrence of clogging of the immersion nozzle can be effectively prevented.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view schematically showing the generation behavior of a large inclusion occurring between tundish-molds in a continuous casting process. FIG.
Fig. 2 is a graph schematically showing fluctuation of a mold bath surface caused by clogging of an immersion nozzle.
3 is a flowchart schematically showing a method of manufacturing a steel for preventing clogging of an immersion nozzle according to an embodiment of the present invention.

Hereinafter, a method of manufacturing a steel capable of suppressing clogging of the immersion nozzle according to an embodiment of the present invention will be described in detail. The terms used below are appropriately selected terms in consideration of functions in the present invention, and definitions of these terms should be made based on the contents throughout this specification.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view schematically showing the generation behavior of a large inclusion occurring between tundish-molds in a continuous casting process. FIG. Fig. 2 is a graph schematically showing fluctuation of a mold bath surface caused by clogging of an immersion nozzle.

1, inclusions generated during steelmaking refinement, or inclusions 20 generated by re-oxidation of components in the molten steel in a casting process, are formed when the molten steel 10 moves from the tundish 110 to the mold 120 The seat portion 131 or the inner wall portion 132 of the immersion nozzle 130 and the outer peripheral surface of the stopper 115. [ The adhered inclusion 22 may be enlarged while growing, and nozzle clogging may occur during the process of growing the adhered inclusion 22 beyond a predetermined size. The large inclusion 25 that has grown to a predetermined size or larger may be detached from the immersion nozzle 130 or the stopper 115 and may be incorporated into the molten steel 10 of the mold 120. At this time, as shown in FIG. 2A, the molten steel in the mold 120 may be fluctuated in the process of dropping and mixing the large inclusion 25. In Fig. 2, the mold level, which is an index indicating the stability of the bath surface, generates several peaks 210 as time elapses. It can be estimated that the fluctuation of the bath surface occurred due to the drop of the large inclusion 25 at the time when the peak 210 was generated. The inclusion of the large inclusion 25 in the molten steel is an element that hinders the cleanliness of the produced steel, and therefore it is necessary to suppress such large inclusions 25.

In the embodiment of the present invention, CaS is selected as a non-metallic inclusion in a molten steel capable of causing nozzle clogging, and a method of inhibiting growth of CaS as a high melting point inclusion attached to an immersion nozzle or a stopper is proposed. According to the present invention, it is found that, if the nonmetal inclusion in the molten steel is a solid phase, it is easy to adhere to the immersion nozzle or the stopper to cause clogging of the nozzle and, in contrast, the nozzle clogging phenomenon can be suppressed when the non- Based on this, a method of converting solid CaS to liquid CaO is proposed as in the following examples.

3 is a flowchart schematically showing a method of manufacturing a steel for preventing clogging of an immersion nozzle according to an embodiment of the present invention. Referring to FIG. 3, in step S110, CaS is injected into the molten steel in the refining process. Specifically, the CaS may be introduced during the vacuum degassing process before the molten steel is supplied to the tundish. Subsequently, in step S120, an oxidizing agent is injected into the molten steel in the tundish during the performance process. The oxidizing agent may be, for example, FeO. At this time, the FeO may convert CaS in the form of inclusions in the molten steel to CaO in the liquid phase. Also, the FeO may react with the CaS added in the refining step to produce CaO in the liquid phase.

The addition of CaS in step S110 is to increase the content of CaO in the liquid in the tundish molten steel by the action of the oxidizing agent in step S120. As the content of CaO in the liquid phase increases, the concentration of CaO in the liquid phase may increase around the solid inclusion CaS. Thereby, the probability that the solid inclusions CaS grow into large inclusions can be lowered. That is, the liquid CaO generated from the CaS can inhibit the growth of CaS in the form of inclusions in the molten steel.

However, the input amount of CaS may be determined in consideration of the content of sulfur in the produced steel in step S110. As an example, if the sulfur content in the produced steel is requested to be in the range of 100 to 700 ppm, the amount of CaS added may be 0.4 to 2.7 kg per ton of molten steel. When the amount of CaS added is less than 0.4 kg, the liquid CaO can not sufficiently exhibit the function of suppressing the growth of solid inclusions CaS. On the other hand, when the amount of CaS supplied exceeds 2.7 kg, the amount of sulfur in the produced steel may exceed 700 ppm.

On the other hand, in step S120, FeO as an oxidizing agent to be fed into the molten steel can proceed as in the following equation (1).

CaS + FeO - > CaO + S --------------- (1)

Based on the above reaction formula, the input amount of FeO may be equal to the input amount of CaS. However, considering the case where oxygen is supplied for re-oxidation of the impurities in the tundish or the mold in the casting process, the actual amount of FeO may be determined so as to have a ratio of 0.5 to 1.0 as compared with the amount of CaS.

In step S120, as described above, the reaction of the solid CaS inclusions originally present in the molten steel and the FeO in addition to the reaction of generating the liquid CaO by the charged CaS and the FeO is performed in the same manner as in equation (1) Lt; / RTI > Therefore, the solid CaS inclusions originally present in the molten steel can be removed.

As described above, according to the embodiment of the present invention, the CaS in the form of inclusions present in the molten steel after refining can be converted into liquid CaO, or the CaO concentration in the liquid phase can be increased by the reaction of CaS and FeO added separately. As a result, it is possible to prevent CaS inclusions from adhering to the inner wall of the immersion nozzle or from growing CaS inclusions into large inclusions. As a result, occurrence of clogging of the immersion nozzle can be effectively prevented.

It is to be understood that the invention includes various modifications and equivalent embodiments that can be derived from the disclosed embodiments as well as those of ordinary skill in the art to which the present invention pertains. Accordingly, the technical scope of the present invention should be defined by the following claims.

10: molten steel, 20, 22, 25: inclusions,
110: tundish, 120: mold, 130: immersion nozzle.

Claims

(a) introducing CaS into the molten steel in the refining process; And
(b) adding an oxidizing agent to the molten steel in the tundish during the casting process to produce liquid CaO from the CaS, thereby suppressing adhesion or growth of CaS inclusions on the inner wall of the tundish immersion nozzle
A method for manufacturing a steel which prevents clogging of an immersion nozzle.

The method according to claim 1,
(a)
And is carried out during the vacuum degassing step of the molten steel
A method for manufacturing a steel which prevents clogging of an immersion nozzle.

The method according to claim 1,
In step (a)
The input amount of CaS is determined in consideration of the content of sulfur in the produced steel
A method for manufacturing a steel which prevents clogging of an immersion nozzle.

The method of claim 3,
When the content of sulfur in the produced steel is 100 to 700 ppm,
The amount of CaS added is 0.4 to 2.7 kg per ton of molten steel
A method for manufacturing a steel which prevents clogging of an immersion nozzle.

The method according to claim 1,
The oxidant is FeO,
The input amount of FeO is in the range of 0.5 to 1.0 in comparison with the input amount of CaS.
A method for manufacturing a steel which prevents clogging of an immersion nozzle.

6. The method of claim 5,
The FeO converts CaS in the form of inclusions in molten steel into CaO in liquid phase
A method for manufacturing a steel which prevents clogging of an immersion nozzle.

6. The method of claim 5,
The FeO reacts with the input CaS to form CaO in liquid phase,
The resulting CaO in the liquid phase inhibits the growth of CaS in inclusion form
A method for manufacturing a steel which prevents clogging of an immersion nozzle.