KR101957594B1 - Continuous casting method using electromagnetic stirring - Google Patents

Abstract

A continuous casting method using an electromagnetic stirring (EMS) apparatus is disclosed. The continuous casting method is a continuous casting method of applying an electromagnetic stirring (EMS) device at the end of solidification in order to reduce center segregation when continuously casting carbon steel in a bloom and a ballet, wherein the intensity of the magnetic field applied to the electromagnetic stirring device is x , The following formula is used for the quasi-ratios.
_{-% C /% C TD (} y) = -7E-07x 2 + 0.0002x + 0.9378
Cholesterol (%) = 7E-05x ² - 0.0071x + 6.3203

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous casting method using an electromagnetic stirring apparatus,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous casting process of a steel material, and more particularly, to a continuous casting process using an electromagnetic stirring process.

In general, the process of continuously solidifying molten steel treated with a desired component in a certain form is referred to as continuous casting. The continuous casting machine which continuously performs the continuous casting is produced in the steel making furnace, the molten steel transferred to the ladle is received in the turndish, and supplied to the mold for the continuous casting machine to produce the slab of a certain size.

The molten steel introduced in the tundish is formed into a slab such as a slab, a bloom, or a billet having a predetermined width and thickness in the mold. The molten steel is first cooled in the mold, And is transferred while maintaining the shape formed in the mold.

As a technique related to this, Korean Patent Laid-Open Publication No. 2004-0057214 (published on July 02, 2004, a method of forming a Billet performance cast with reduced center segregation) is available.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a continuous casting method using an electromagnetic stirring (EMS) apparatus, in which the magnetic field applied to the EMS is controlled to suppress occurrence of white band and center segregation, So that it can be ensured at a high level.

A continuous casting method according to one aspect of the present invention is a continuous casting method in which a solidification end electronic stirring device (EMS) is applied in order to reduce center segregation when continuously casting carbon steel in a bloom and a ballet, when% C /% C _TD the y la, wherein - the strength of the magnetic field that is x,% C /% C _TD and part piece seokryul ((neighborhood average carbon content -% C /% CTD of minimum value) / ( The average carbon content in the vicinity of the solidification end) can be controlled according to the following equations (1) and (2), and the intensity of the electric field applied to the final solidification agitating apparatus (EMS) can be controlled.
Equation 1
^{y = -7E-07x 2 + 0.0002x} + 0.9378
Equation 2
Cholesterol (%) = 7E-05x ² - 0.0071x + 6.3203
Where% C is the carbon (C) content of the white band generator, and% C _TD is the tundish average carbon (C) content.

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In one embodiment of the present invention, the carbon steel may be a low carbon steel containing 0 to 0.25% by weight of carbon (C) in the total steel.

In one embodiment of the present invention, the carbon steel may be a large-area bloom having a short side portion of 300 mm or more.

According to the present invention, it is possible to calculate the loose stone rate according to the intensity of the magnetic field applied to the EMS, so that the internal quality of the cast steel can be predicted by controlling the intensity of the magnetic field applied by EMS according to the center segregation and loose stone ratio required for the steel The target quality can be secured.

1 is a view schematically showing an example of a continuous casting apparatus using EMS.
FIG. 2 is a view showing a state in which a white band is generated inside the cast steel in a continuous casting process using an EMS device.
3 is a graph showing the internal quality of the cast steel according to the intensity of the applied magnetic field in the continuous casting apparatus using the final EMS.
FIG. 4 is a graph showing the segregation rate according to the intensity of the magnetic field applied to the final EMS.
5 is a graph showing the ratio (% C /% C _TD ) of the tundish average carbon (C) content to the carbon (C) content of the white band generating portion according to the intensity of the applied magnetic field of the final EMS.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may be embodied in many different forms and is not limited to the embodiments described herein. Throughout this specification, the same or similar components are denoted by the same reference numerals. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

Electromagnetic Stirring (EMS) process in continuous casting process was developed in order to reduce segregation in continuous casting. By applying a rotating magnetic field or a moving magnetic field in close proximity to a cast steel, electric current is generated in the non-solidified portion inside the cast steel When a current flows perpendicularly to the magnetic field, a force perpendicular to the electric current, that is, a propulsive force, is applied by the Faraday's law. This is a process of agitating the non-solidified molten steel by the driving force. This stirring flow destroys crystals undergoing solidification, and the molten steel temperature is uniformized to low temperature, so that equiaxed crystals are developed and segregation can be solved.

1 is a view schematically showing an example of a continuous casting apparatus using EMS.

1, the continuous casting apparatus includes a ladle containing refined molten steel 10 in a steelmaking process, a tundish 20 for receiving molten steel through an injection nozzle connected to the ladle and temporarily storing the molten steel, A mold for temporarily receiving molten steel 10 temporarily stored in a tundish through an immersion nozzle and initially solidifying the molten steel in a predetermined shape, and a plurality of segments (not shown) provided at a lower portion of the mold, and a cooling line 40 in which segments are arranged continuously.

It takes some time until the solidified molten steel begins to solidify and completely solidify in the course of cooling out from the mold. The molten steel 10 is all liquid, and an electromagnetic stirring (EMS) device 30 is disposed on the casting throughout the region where solidification is almost complete in the continuous casting apparatus. The EMS 30 applies an electromagnetic field from the outside to generate a rotating current in the internal molten steel to control the internal structure. The EMS 30, 31, 32, 33 used in the continuous casting apparatus has a mold EMS 31, a strand EMS 32 and a final EMS 33 located at the end of solidification depending on the installation position , Alone or in combination.

In the case of the final EMS 33 installed at the final stage of solidification, the center segregation inside the cast steel can be removed to improve the quality of the cast steel when a suitable electromagnetic field is applied. However, since a relatively high electromagnetic field is applied to the cast steel, ), That is, it can occur in the brackish rocks.

FIG. 2 is a view showing a state in which a white band is generated inside the cast steel in a continuous casting process using an EMS device.

The white band shows a white band shape which can be partially visually confirmed by macro-etching at the time of agitation due to forced flow of the EMS device. If the loose stones of the white band portion where the component is partially reduced at such a specific position is large, it is necessary to control the loose stones because the desired tissue and mechanical properties may not be obtained in the final product.

3 is a graph showing the internal quality of the cast steel according to the intensity of the applied magnetic field in the continuous casting apparatus using the final EMS.

Referring to FIG. 3, as the intensity of the magnetic field applied to the final EMS increases, the incidence of center segregation decreases but the segregation rate increases. Therefore, it is necessary to control the magnetic field applied to the EMS such that the generation of center segregation is suppressed and the internal quality of the cast steel is secured to the target level while suppressing the generation of white bands as much as possible, as shown in the center of the graph.

In the continuous casting method using the final EMS, the present invention analyzes the trend of the occurrence of the false seam according to the applied magnetic field of the final EMS and derives a correlation between the magnitude of the magnetic field of the final EMS and the occurrence rate of the frac- tured stones. According to the present invention, the optimum magnetic field size of the EMS is set by using the correlation between the magnetic field of the final EMS and the occurrence rate of the frac- tions, and the maximum electromagnetic field is applied within a range where no white band is formed .

For this purpose, the loose stone ratio according to the size of the magnetic field was measured using a continuous casting apparatus equipped with the final EMS shown in FIG. The specific gravity is a value obtained by comparing the content of the white band generating portion with the average content of the white band adjacent portion with respect to the reference component, and is generally used based on the content of carbon (C).

More specifically, the final EMS was installed at a position 10 to 20 m from the mold of the continuous casting apparatus, and a test was conducted in a process of continuously casting a low carbon steel having a carbon (C) content of 0.25 wt% or less. At this time, the continuous casting was performed while changing the magnetic field applied to the EMS to 50 to 500 G, and then the occurrence of the white band was confirmed by macro-etching analysis of the continuous cast product. At this time, C / S analysis was performed after drill chip processing at intervals of 3 to 5 mm from the white band generating portion or the final EMS affected portion, and the results are shown in FIG. 4 and FIG.

FIG. 5 is a graph showing the ratio (% C /% C) of the tundish average carbon (C) content to the carbon content of the white band generating portion. _TD ) according to the intensity of the applied magnetic field of the final EMS.

Referring to FIG. 4, when the magnitude of the magnetic field applied to the final EMS was 90 G, the loose stones were 5.8%, 7.8% at 180G, 10.5% at 270G, 10.8% at 360G and 18.4% at 470G .

Referring to FIG. 5, when the magnitude of the magnetic field applied to the final EMS is 90 G, (% C /% C _TD ) is 0.948, 0.951 at 180 G, 0.905 at 270 G, 0.924 at 360 G, and 0.846 at 470 G appear.

As shown in FIG. 4 and FIG. 5, when the minimum value of the% V / C% _TD was checked using the C / S analysis value, The minimum value of _TD decreased. Using the above analytical values, Equation 1 and Equation 2 can be derived, where x is the intensity of the magnetic field and y is -% C /% C _TD .

Loose quartile = (nearest neighbor -% C /% C minimum value of _TD ) / (nearest neighbor)

Equation 1

^{y = -7E-07x 2 + 0.0002x} + 0.9378

Equation 2

Cholesterol (%) = 7E-05x ² - 0.0071x + 6.3203

By using Equation 1 and Equation 2, it is possible to calculate the loose stones according to the intensity of the magnetic field applied to the final EMS. Therefore, by controlling the intensity of the magnetic field applied by EMS according to the center segregation and loose stones required for the steel, And the target quality can be secured.

In one embodiment of the present invention, the steel material to be treated may be a low carbon steel having a carbon (C) content of more than 0 and 0.25 wt% or less, and a large area bloom having a short side portion of 300 mm or more.

According to the above formula, it is preferable to control the strength of the magnetic field so that the fragrance rate is generally 20 or less.

While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments. Such changes and modifications are intended to fall within the scope of the present invention unless they depart from the scope of the present invention. Accordingly, the scope of the present invention should be determined by the following claims.

Claims (4)

A continuous casting method for applying an electromagnetic stirring (EMS) device for reducing the center segregation during continuous casting of carbon steel into blooms and billets,
When the intensity of the magnetic field applied to the electromagnetic stirring device is x, -% C /% C _TD , y,
The above-mentioned% C /% C _TD and loose stones ((average value of adjacent carbon portion -% C /% of CTD minimum value) / (average carbon content of adjacent portion)) are calculated according to the following equations (1)
And controlling the strength of the electric field applied to the EMS device to control the partial quiescence rate.
Equation 1
^{y = -7E-07x 2 + 0.0002x} + 0.9378
Equation 2
Cholesterol (%) = 7E-05x ² - 0.0071x + 6.3203
here,
% C is the carbon content (C) of the white band generating portion
% C _TD is the tundish average carbon (C) content.
The method according to claim 1,
Wherein the carbon steel is a low carbon steel containing 0 to 0.25% by weight of carbon (C) in the total steel.
The method according to claim 1,
Wherein the carbon steel is a large-area bloom having a short side portion of 300 mm or more.
The method according to claim 1,
And the loose stone ratio is controlled to 20 or less.

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