KR20160056623A - Continuous casting apparatus and Continuous casting method - Google Patents

Continuous casting apparatus and Continuous casting method Download PDF

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Publication number
KR20160056623A
KR20160056623A KR1020140157172A KR20140157172A KR20160056623A KR 20160056623 A KR20160056623 A KR 20160056623A KR 1020140157172 A KR1020140157172 A KR 1020140157172A KR 20140157172 A KR20140157172 A KR 20140157172A KR 20160056623 A KR20160056623 A KR 20160056623A
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KR
South Korea
Prior art keywords
electromagnetic
cast steel
mold
electromagnetic stirring
casting
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KR1020140157172A
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Korean (ko)
Inventor
최정윤
Original Assignee
주식회사 포스코
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Priority to KR1020140157172A priority Critical patent/KR20160056623A/en
Publication of KR20160056623A publication Critical patent/KR20160056623A/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
    • B21B3/02—Rolling special iron alloys, e.g. stainless steel
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/04—Continuous casting of metals, i.e. casting in indefinite lengths into open-ended moulds
    • B22D11/043—Curved moulds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/10—Supplying or treating molten metal
    • B22D11/11—Treating the molten metal
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/10—Supplying or treating molten metal
    • B22D11/11—Treating the molten metal
    • B22D11/114—Treating the molten metal by using agitating or vibrating means
    • B22D11/115—Treating the molten metal by using agitating or vibrating means by using magnetic fields
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/12—Accessories for subsequent treating or working cast stock in situ
    • B22D11/128—Accessories for subsequent treating or working cast stock in situ for removing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/16—Controlling or regulating processes or operations
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/16—Controlling or regulating processes or operations
    • B22D11/20—Controlling or regulating processes or operations for removing cast stock
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
    • B22D27/02—Use of electric or magnetic effects

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Continuous Casting (AREA)

Abstract

The present invention relates to a continuous casting apparatus and a continuous casting method, and more specifically, to a continuous casting apparatus and a continuous casting method which use an electronic agitation device to improve a cast center segregation and prevent a white band at the same time. According to an embodiment of the present invention, the continuous casting apparatus comprises: a mold into which molten steel is injected; a transport unit which is connected to the mold and transports a cast drawn from the mold; and a plurality of electronic agitation devices disposed around the transport unit in a transport direction of the cast and separated from each other. Also, according to another embodiment of the present invention, the continuous casting method comprises: a step of injecting molten steel into a mold; a step of transporting a cast drawn from the mold; and a step of using a plurality of electronic agitation devices separated from each other in a transport direction of the cast to agitate an unsolidified portion of a middle portion of the cast.

Description

[0001] Continuous casting apparatus and continuous casting method [0002]

The present invention relates to a continuous casting apparatus and a continuous casting method, and more particularly, to a continuous casting apparatus and a continuous casting method capable of improving casting center segregation and preventing white band by using an electromagnetic stirring apparatus will be.

In a continuous casting process, molten steel is continuously injected into a mold having a predetermined shape, and the molten steel is continuously drawn into the lower side of the mold to form slabs, blooms, , Billet, and the like.

In order to improve bismuth segregation in producing a bloom or billet casting by continuous casting in which the continuous casting process is carried out, it is necessary to accelerate the production of equiaxed crystals by stirring the non-solidified molten steel. An electromagnetic stirrer (EMS) is generally used for stirring.

The electromagnetic stirrer is mainly used at the mold position for stirring the molten steel as in Korean Patent No. 10-0553577 (Feb. 23, 2006), and is also used in the strand of the continuous casting apparatus to stir the non- . When the agitation force (for example, current intensity) of the electromagnetic stirring apparatus is increased, the possibility of segregation improvement increases because the equiaxed region is widened. However, if the agitation force is too strong, the concentration of the alloy in the molten steel adjacent to the solid phase at the time of agitation is low After completion of solidification, a white band (loose stones) is left in the inside of the slab, thereby causing a problem that the slab quality is lowered.

As described above, as the agitation force of the electromagnetic stirrer increases, the possibility of segregation improvement increases, but the area of the white band also widens. Therefore, it is required to select agitation conditions capable of simultaneously improving the center segregation and preventing white band.

Korean Patent Registration No. 10-0553577

The present invention provides a continuous casting apparatus and a continuous casting method capable of simultaneously performing casting center segregation improvement and white band prevention by stirring with a plurality of electromagnetic stirring apparatuses.

A continuous casting apparatus according to an embodiment of the present invention includes: a casting mold into which molten steel is injected; A transferring unit connected to the mold and transferring the casting material drawn from the mold; And a plurality of electromagnetic stirring devices provided to be spaced apart from each other in the feeding direction of the casting material around the conveyance portion.

The plurality of electromagnetic stirring apparatuses may be located in a section where the solidification fraction of the cast steel is 0.3 to 0.9.

Wherein the transfer unit comprises: a vertical part connected to a lower end of the mold; A horizontal part for horizontally feeding the cast steel; And a curved portion connecting the vertical portion and the horizontal portion, and the plurality of electromagnetic stirring devices may be provided around the curved portion.

A guide member may be disposed between the plurality of electromagnetic stirring devices.

The intensity of the electric current provided to each of the plurality of electromagnetic stirring apparatuses may be 100 to 600 A and the intensity of the electric current provided to each of the plurality of electromagnetic stirring apparatuses may be different from each other.

According to another aspect of the present invention, there is provided a continuous casting method including: injecting molten steel into a mold; Transferring a casting material drawn from the casting mold; And stirring the non-solidified portion of the cast steel by using a plurality of electromagnetic stirring devices spaced apart from each other in the feeding direction of the cast steel.

A vertical part connected to a lower end of the casting mold; A horizontal part for horizontally feeding the cast steel; And a curved portion connecting the vertical portion and the horizontal portion, and the plurality of electromagnetic stirring devices may be provided so as to surround the curved portion of the feeding portion.

In the stirring step, the non-solidified portion of the center of the cast steel can be agitated in a section where the solidification fraction of the cast steel is in the range of 0.3 to 0.9, and the current is supplied to the plurality of electromagnetic stirring apparatuses The non-solidified portion of the center portion can be stirred, and the intensity of the electric current provided to each of the plurality of electromagnetic stirring devices can be made different from each other.

The continuous casting apparatus and the continuous casting method according to the present invention can stir a long solidification zone with a plurality of electromagnetic stirring apparatuses to improve segregation or center shrinkage hole quality without strong agitating force, Can also be prevented.

Further, since it is possible to set the agitation force differently according to the position of each electromagnetic stirring apparatus, it is possible to obtain an energy saving effect by setting an optimum stirring condition.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing an equiaxed area fraction and a white band index according to a current value of an electromagnetic stirring apparatus in a continuous casting apparatus according to an embodiment of the present invention. FIG.
BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a continuous casting apparatus,
3 is a sectional view showing a continuous casting apparatus according to an embodiment of the present invention;
4 is a flowchart showing a continuous casting method according to another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It will be apparent to those skilled in the art that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, It is provided to let you know. In the description, the same components are denoted by the same reference numerals, and the drawings are partially exaggerated in size to accurately describe the embodiments of the present invention, and the same reference numerals denote the same elements in the drawings.

FIG. 1 is a graph showing an equiaxed area ratio and a white band index according to a current value of an electromagnetic stirring apparatus in a continuous casting apparatus according to an embodiment of the present invention. FIG. 1 (a) FIG. 1 (b) is a graph of one electron stirring apparatus at the end of solidification of the cast steel, and FIG. 1 (c) Graph.

In order to improve the seismic centering of the cast steel, when the non-solidified portion of the cast steel is agitated, the isostatic generation is promoted as the agitation force is increased. When the agitation force is larger than a certain level, The area becomes wider. Referring to FIG. 1, as the current value (i.e., agitating force) of the electromagnetic stirrer increases, the equiaxed area fraction increases and the white band index increases. have. At the beginning of solidification of the casting, a single agitator can obtain a range of agitating force in which the white band index does not exceed the allowable limit and the equiaxed area fraction becomes a certain fraction or more. However, It is not possible to obtain such a range of the agitation force only by the apparatus, and it is understood that two or more electromagnetic stirring apparatuses are required to obtain the range of the agitation force. This means that unlike the initial stage of solidification, which can improve the center segregation of the cast steel even with one electromagnetic stirrer, two or more electromagnetic stirrers are required at the end of casting to improve the center segregation. In addition, when the number of electromagnetic stirrers increases, the graph of the white band index shifts to a higher value than that of only one graph of the equilibrium constant area fraction in the flakes without changing. Thus, the range of the white band index does not exceed the allowable limit It can be seen that the fraction of the equiaxed area can be increased by the current value of the low electromagnetic stirrer to improve the internal quality of the cast steel. As the number of electromagnetic stirrers increases, the amount of the equiaxed portion of the steel is shifted upward and the current value of each electronic stirring device can be lowered. Therefore, when a large number of electromagnetic stirrers are installed, a high quality cast steel with a low white band index is produced .

In the present invention, at least two electromagnetic stirrers are installed and stirred in the final stage of solidification of the casting. However, since the stirring can be performed in a long section as the number of the electromagnetic stirrer increases, the intensity of the current , It was possible to broaden the equiaxed crystal zone as much as possible.

2 is a plan view showing a shape of a cast steel and an electromagnetic stirring apparatus in a continuous casting apparatus according to an embodiment of the present invention.

Referring to FIG. 2, the electromagnetic stirring apparatus 110 may be a rotative electromagnetic stirring apparatus having a circular inner hole, and may include a coil core 111. The rotary electronic stirring device can be used in the case of a casting 120 having a width and a thickness ratio of the casting slab of less than 2 so that the non-solidified portion of the casting center portion is well stirred when the casting slip passes the inner hole. The billet 120 having a ratio of less than 2 may include blooms and billets. In consideration of being provided in the curved section (or curved section) of the conveying section or the strand, the electromagnetic stirrer 110 may have a length of 1 m or less in the casting direction. When the length in the casting direction of the electromagnetic stirring apparatus becomes longer than 1 m, there is no problem other than the fact that the power consumption is large in the straight section (vertical section or horizontal section), but the electromagnetic stirrer can not be installed due to the curvature in the curved section. The length of the electromagnetic stirring apparatus can be made long by making the electromagnetic stirring apparatus into a bending type, but the bending type electromagnetic stirring apparatus has a problem in that it is difficult to manufacture and the price is high because mutual balance (or symmetry) must be taken into account in stirring.

3 is a cross-sectional view illustrating a continuous casting apparatus according to an embodiment of the present invention.

Referring to FIG. 3, a continuous casting apparatus according to an embodiment of the present invention includes a mold 130 into which molten steel is injected; A transfer unit 140 connected to the mold 130 and transferring the cast 120 to be withdrawn from the mold 130; And a plurality of electromagnetic stirring devices 110 provided to be spaced apart from each other in the feeding direction of the strip 120 around the feeder 140.

The mold 130 is a mold used to form the casting 120 by injecting molten steel, and may be made of a suitable heat-resistant material according to the temperature of the molten steel. Sand, metal (mainly steel) is used as a mold for making the casting slab 120, each of which is called a sand mold. There is also a shell type that is made by mixing thermosetting resin in the sand of refractories.

The transfer unit 140 is connected to a lower portion of the mold 130 and serves to transfer the cast 120 from the mold 130 and may include a guide member. In addition, a cooling water supply device (not shown) may be included to assist solidification of the cast steel.

The electromagnetic stirrer 110 is installed outside the feeder 140 so as to surround the feeder 140. The electromagnetic stirrer 110 generates electromagnetic force to generate convection in the non-solidified portion of the center of the cast steel 120, thereby stirring the un-solidified portion. The electromagnetic stirrer 110 can adjust the agitating force by the intensity of the electric current using the electromagnetic force proportional to the intensity of the electric current, and the solidification rate of the product 120 is between 0 (pure liquid phase) and 1 Area. ≪ / RTI > On the other hand, since the coagulation layer to be permeated by the electromagnetic force is thick at the end stage of coagulation near the coagulation fraction of the cast steel 120 of 1, in order to stir the coagulation force (for example, current strength) It is preferable that the above-described electromagnetic stirring apparatus 110 is provided.

In addition, the plurality of electromagnetic stirring apparatuses 110 may be located in a section where the solidification fraction of the cast steel 120 is 0.3 to 0.9. At the initial stage of solidification (or the solidification fraction of less than 0.3) of the casting slab 120, the non-solidified portion is wide and the solidification fraction increases at a high rate, Can occur. In addition, if stirring is performed at the initial stage of solidification of the cast steel 120, the stirring effect is reduced as the steel moves closer to the end of solidification, and stirring is required later, which is troublesome and inefficient. On the contrary, in the section where the solidification fraction of the cast steel 120 is larger than 0.9, since the solidification layer is thick, the electromagnetic force is difficult to permeate and the non-solidified portion is small. If the solidification fraction of the cast steel 120 is agitated in a range of 0.3 to 0.9, the equiaxed crystal region in the cast steel 120 can be maximized by an agitation force whose white band does not exceed the allowable limit, thereby reducing the segregation phenomenon of the cast steel 120 effective. On the other hand, at the final stage of solidification of the cast steel 120, the agitating force of the strong electromagnetic stirrer 110 is required because the solidification layer to be permeated by the electromagnetic force is thick. In the section where the solidification fraction of the cast steel 120 is 0.8 to 0.9, A plurality of electromagnetic stirrers 110 are provided so as to be spaced apart from each other in a direction in which the solidification fraction is lowered from a position where the coagulation fraction is lowered. When stirring is performed in a long section, Can be prevented. In one embodiment of the present invention, a plurality of electromagnetic stirring apparatuses 110 are installed so as to be spaced from each other in a direction in which the solidification fraction is lowered at a position where the solidification fraction of the cast steel 120 is 0.9, When the plurality of electromagnetic stirring apparatuses 110 were provided up to a position where the coagulation fraction of the casting body 120 was 0.3, (120) was the best in internal quality. On the other hand, the number of the electromagnetic stirring apparatuses 110 provided in the section where the solidification fraction of the cast steel 120 is 0.3 to 0.9 satisfies a plurality, and is not particularly limited. The number of the electromagnetic stirring apparatuses 110 and the spacing distance may vary depending on various casting conditions Can be determined.

The transfer unit 140 includes a vertical part connected to a lower end of the mold 130; A horizontal portion 142 for horizontally feeding the slab 120; And a curved portion connecting the vertical portion and the horizontal portion 142. A plurality of electromagnetic stirring devices 110 may be provided around the curved portion. However, in the case where only the vertical portion exists, the height of the equipment is increased in order to increase the casting speed and the cross-sectional area of the casting, so that the length of the casting is limited, If there is only the horizontal portion 142, there is a great difficulty in feeding the slab. Due to such a problem, the conveying part 140 including the curved part is used, and the vertical part may have a very short section. In an embodiment of the present invention, since the electromagnetic stirring device 110 having a length of 1 m or less in the casting direction is used, a plurality of electromagnetic stirrers 110 may be provided in the curved portion to increase the stirring interval. If the length of the electromagnetic stirring apparatus in the casting direction is long, it can not be installed in the curved portion due to the curvature. However, the electromagnetic stirring apparatus 110 having the length of 1 m or less in the casting direction can be installed without being affected by the curvature, The stirring section can be easily increased by disposing the electromagnetic stirrers 110 of the casting 120 in the conveying direction of the casting 120. On the other hand, in the continuous casting apparatus, the solidification of the casting 120 is completed mainly at the curved portion of the conveying portion 140 and the boundary portion of the horizontal portion 142. The reason for this is that when the solidification of the cast steel 120 is completed prior to the completion of the solidification of the cast steel 120, the quality of the cast steel 120 is deteriorated because the cast steel 120 must be artificially deformed by applying pressure to the cast steel 120, Since the curved portion of the curved portion must be maintained constant so that the curved portion can be smoothly conveyed from the curved portion to the curved portion, This is because when the pressure is applied and the overall curvature of the curved portion becomes gentle, the device becomes large. When the solidification of the slab 120 is completed too late at the horizontal portion 142, the solidification of the slab 120 is completed at the boundary between the curved portion of the transfer portion 140 and the horizontal portion 142, There is a reason that the direction length becomes long. In this way, solidification of the casting 120 can be completed at the curved portion of the conveying portion 140 and at the boundary portion of the horizontal portion 142, so that the casting 120 can be effectively straightened and conveyed, And the solidification complete point exists at the boundary portion between the horizontal portion 142 and the curved portion of the feeder 140, the section having the coagulation fraction of 0.3 to 0.9 is positioned in the curved portion of the feeder 140. Accordingly, the plurality of electromagnetic stirring apparatuses 110 can be provided in the curved portion of the conveyance portion 140 where the solidification fraction of the cast steel 120 ranges from 0.3 to 0.9.

A guide member 141 may be disposed between the plurality of electromagnetic stirring apparatuses 110. The guide member 141 supports the casting 120 in the conveying unit 140 to assist the conveying of the casting 120 so that the casting 120 is guided along the conveying unit 140, And may be a guide roll or a pinch roll. In this case, the shape of the casting 120 may be corrected by applying a pressure when the casting rolls 142 enter the casting roll 142. When the stirring is performed on the cast steel 120, the shape of the cast steel 120 may be deformed. If there is the guide member 141, such deformation can be corrected. If a plurality of electromagnetic stirring apparatuses 110 are continuously installed without the guide member 141 between the electromagnetic stirrers 110, the deformation of the cast steel may be caused during the long stirring period. As a result, It is preferable that the guide member 141 is disposed between the plurality of electromagnetic stirring apparatuses 110. [ Particularly, a guide member 141 is required between the electromagnetic stirring devices 110 at the curved portion, the curved portion and the horizontal portion 142 of the conveying portion 140. The curved portion of the conveying portion 140 is provided with a guide member The feed 120 may not be guided along the feed part 140 and may be deformed after a long agitation period and the curved part and the horizontal part 142 The tensile strain of the cast steel 120 generated in the curved portion can not be removed and the thickness of the cast steel 120 can be made non-uniform. Accordingly, the guide member 141 can be disposed between the plurality of electromagnetic stirring apparatuses 110, thereby stably calibrating the cast steel 120. On the other hand, if the guide member 141 is not disposed between the plurality of electromagnetic stirring apparatuses 110 but only a part of the guide member 141 is disposed, the effect of calibrating the feeding direction and shape of the casting strip 120 is insignificant.

And a current of 100 to 600 A may be provided to each of the plurality of electromagnetic stirring apparatuses 110 using an electromagnetic force proportional to the intensity of the electric current as an agitating force. If the current intensity of the electromagnetic stirrer 110 exceeds 600 A, the white band area within the cast steel 120 becomes wider than the allowable limit, which adversely affects the internal quality of the cast steel 120 (refer to FIG. 1) If the current intensity of the apparatus 110 is less than 100 A, the solidification layer is thick at the final stage of solidification of the casting 120 and no agitation of the unsolidified portion occurs, Since the stirring device 110 is required, it is inefficient in equipment installation and power consumption.

Further, the intensity of the electric current provided to each of the plurality of electromagnetic stirring apparatuses 110 may be different from each other. Since the solidification layer is thin at the position where the solidification fraction of the cast steel 120 is low, the strength of the electric current of the electromagnetic stirring apparatus 110 is relatively weak and the solidification layer is thick at the position where the solidification fraction of the cast steel 120 is high, The intensity of the current of the device 110 can be made relatively strong. At this time, the intensity of the electric current of the electromagnetic stirrer 110 may be lowered by 50 to 60 A each time the coagulation fraction is decreased to 0.1 as the solidification fraction is lowered at the solidification completion point of the casting 120. When the agitation section is increased by the plurality of electromagnetic stirring apparatuses 110, the intensity of the electric current of each of the electromagnetic stirring apparatuses 110 can be made lower than when the stirring section is short, The intensity of the current may be lowered according to the solidification fraction at the position where the solidification is performed. As described above, the intensity of the electric current of the electromagnetic stirring apparatus 110 can be set differently according to the position where each electromagnetic stirring apparatus 110 is provided, so that if the optimum stirring conditions are set, the power consumption by the electromagnetic stirring apparatus 110 can be reduced have. Such an effect can be advantageous in a conveying portion having only a vertical portion or a horizontal portion as compared with a long electromagnetic stirring device. The optimum stirring conditions may be determined through casting tests prior to production run.

In the continuous casting apparatus of the present invention, one or two electromagnetic stirring apparatuses 110 may be installed at the initial stage of solidification of the cast steel 120 in order to more effectively stir and improve the internal quality of the cast steel 120, A mold electronic stirring device may be installed. The mold electronic stirring apparatus is not particularly limited in kind, shape, number, length of the casting direction, stirring direction and the like.

As described above, in the continuous casting apparatus according to the present invention, the non-solidified portion of the center of the cast steel 120 is stirred by a plurality of electromagnetic stirrers in a section where the solidification fraction of the cast steel 120 is 0.3 to 0.9, Can be achieved at the same time. In addition, it is possible to reduce power consumption by the electromagnetic stirring apparatus 110 in the continuous casting process by adjusting the current intensity of each electromagnetic stirring apparatus 110 appropriately.

4 is a flowchart illustrating a continuous casting method according to another embodiment of the present invention.

Referring to FIG. 4, a continuous casting method according to another embodiment of the present invention includes injecting molten steel into a mold (S100); (S200) of feeding the casting material drawn from the mold; And a step S300 of stirring the unfrozen portion of the cast steel by using a plurality of electromagnetic stirring devices spaced apart from each other in the feeding direction of the cast steel.

First, the molten steel is injected into the mold (S100). When the molten steel is injected into the mold, it is cooled to form a solidified layer, and the molten steel is drawn to the lower portion of the mold to form a cast product.

Next, the casting is pulled to the lower part of the casting mold through the conveying unit (S200). Wherein the transfer unit comprises: a vertical part connected to a lower end of the mold; A horizontal part for horizontally conveying the slab; And a curved portion connecting the vertical portion and the horizontal portion, and may include a guide member. The conveying portion may have only a vertical portion or a horizontal portion, but a conveying portion including a curved portion is used due to various problems that occur when there is only a vertical portion or a horizontal portion. The plurality of electromagnetic stirring devices may be provided to surround the curved portion of the conveying portion and a plurality of electromagnetic stirring devices may be provided in the curved portion of the conveying portion so as to be spaced apart from each other in the conveying direction of the casting material and stirred in the long solidifying portion . On the other hand, if the length in the casting direction of the electromagnetic stirrer is long, the electromagnetic stirring device can not be installed in the curved portion due to the curvature. In an embodiment of the present invention, the electromagnetic stirrer having a length of 1 m or less in the casting direction can also be installed in the curved portion And the agitation section may be increased by providing a plurality of electromagnetic stirring apparatuses in the curved section so as to be spaced apart from each other in the feeding direction of the main body. Therefore, even in the curved portion, the equiaxed region in the cast steel can be widened by the agitating force of the electromagnetic stirring apparatus which is low enough not to cause the white band, thereby improving the center segregation of the cast steel.

Subsequently, a plurality of electromagnetic stirring apparatuses spaced apart from each other in the feeding direction of the cast steel are used to stir the non-solidified portion of the cast steel (S300). The casts drawn from the mold move through the conveying part. As the mold moves away from the mold, the casting solidifies gradually, and the solidification layer thickens and then completely coagulates. Here, the non-solidified portion that has not yet solidified at the central portion of the cast steel moving through the conveying portion is stirred using a plurality of electromagnetic stirring devices. At this time, if the non-solidified portion of the center of the cast steel is agitated in a long section by a plurality of electromagnetic stirrers, the intensity of the electric current of each electromagnetic agitator can be made lower than that when the agitating period is short. If an agitation section is increased by using an electromagnetic stirring apparatus having a length of 1 m or less in the casting direction, a long agitation section can be efficiently formed also in the curved section of the conveyance section. Depending on the position of each electromagnetic stirring apparatus, The strength of the electric current can be made different from each other. If a plurality of electromagnetic stirring devices are provided so as to be spaced apart from each other in the feeding direction of the cast steel, a guide member may be disposed between the plurality of electromagnetic stirring devices.

In the step of stirring, the non-solidified portion of the center of the cast steel can be agitated by a plurality of electromagnetic stirrers in a section where the solidification fraction of the cast steel is 0.3 to 0.9. In the section where the solidification fraction of the cast steel is less than 0.3, the non-solidified part is wide and the solidification fraction is increased at a high rate, so that the uniform stirring is not performed uniformly. Further, if stirring is performed at the initial stage of solidification of the casting, the stirring effect decreases as the solidification proceeds, and it is troublesome and inefficient because stirring is required to be performed later. On the contrary, in the section where the solidification fraction of the cast steel is greater than 0.9, the stirring effect is insignificant because the solidification layer is thick and the electromagnetic force is difficult to permeate and the uncoagulated portion is small. If the solidification fraction of the cast steel is in the range of 0.3 to 0.9, it is effective to reduce the segregation phenomenon of the cast steel because the equiaxed area in the cast steel (120) can be maximized by the agitating force of the white band not exceeding the allowable limit. On the other hand, at the end of solidification of the casting, strong agitation of the electromagnetic stirrer is required because the solidification layer to be permeated by the electromagnetic force is thick. In the region where the solidification fraction is 0.8 to 0.9, the solidification fraction is decreased If a plurality of electromagnetic stirring apparatuses are provided so as to be spaced apart from each other and stirred in a long section, the equiaxed area in the cast steel can be widened by a weak engaging force, thereby preventing white band from occurring. In one embodiment of the present invention, the casting test was carried out by placing a plurality of electromagnetic stirring apparatuses apart from each other in a direction in which the solidification fraction was lowered at a position where the solidification fraction of the casting was 0.9, The equilibrium area of the cast steel was widened by the reaction force and the internal quality of the cast steel was highest when a plurality of electromagnetic stirrers were provided up to a position where the solidification fraction of the cast steel was 0.3. On the other hand, the number of the electromagnetic stirring devices provided in the section where the solidification fraction of the cast steel is in the range of 0.3 to 0.9 satisfies a plurality, and is not particularly limited, and the number and spacing distance of the electromagnetic stirring device can be determined in consideration of various casting conditions.

Further, in the stirring step, the non-solidified portion of the center of the cast steel can be agitated by a plurality of electromagnetic stirring apparatuses provided with a current intensity of 100 to 600 A. If the current intensity of the electromagnetic stirrer exceeds 600 A, the white band area inside the cast steel becomes wider than the allowable limit, which adversely affects the internal quality of the cast steel (see FIG. 1) In the case where the coagulation temperature is small, the coagulation layer is thick at the end of coagulation and the non-coagulated portion is not stirred. Since the stirring effect is small even at the initial stage of coagulation, a large number of electromagnetic stirring devices are required. The current intensity of the device can be limited to a range of 100 to 600 A.

In addition, in the stirring step, the intensities of the electric currents provided to the plurality of electromagnetic stirring devices can be made different from each other. Since the solidification layer is thin at the position where the solidification fraction of the casting is low, the strength of the electric current of the electromagnetic stirring apparatus is relatively weakened and the solidification layer is thick at the position where the solidification fraction of the casting is high, can do. At this time, the intensity of the electric current of the electromagnetic stirring apparatus may be lowered by 50 to 60 A whenever the coagulation fraction is lowered to 0.1 as the solidification fraction is lowered at the solidification completion point of the casting. Further, if the stirring section is increased by a plurality of electromagnetic stirring apparatuses, the current intensity of each electromagnetic stirring apparatus can be made lower than when the stirring section is short, and the current intensity of the current stirring apparatus It is also possible to lower the strength. In this way, the intensity of the electric current of the electromagnetic stirring apparatus can be set differently according to the position where each electromagnetic stirring apparatus is provided, and power consumption by the electromagnetic stirring apparatus can be reduced if the optimum stirring conditions are set. The optimum stirring conditions may be determined through casting tests prior to production run. On the other hand, if the separation distances of the plurality of electromagnetic stirring apparatuses become too far away, the effect of lowering the current intensity of each electromagnetic stirring apparatus by a plurality of electromagnetic stirring apparatuses may be insignificant.

As described above, in the continuous casting apparatus and the continuous casting method according to the present invention, the non-solidified portion of the cast steel is agitated in a long section by a plurality of electromagnetic stirrers in a section having a solidification fraction of 0.3 to 0.9, It is possible to improve the center segregation of the cast steel and to prevent the white band at the same time. In addition, it is possible to reduce power consumption by the electromagnetic stirring apparatus in the continuous casting process by appropriately adjusting the current intensity of each electromagnetic stirring apparatus. On the other hand, in the present invention, a long agitation section can be efficiently formed even in the curved section of the transfer section by using the electromagnetic stirring device of 1 m or less. When a plurality of electromagnetic stirring devices are provided so as to be spaced apart from each other in the conveying direction of the casting, The guide member can be disposed between the stirring devices, so that it is possible to calibrate the casting more stably than when stirring in a long section without the guide member.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be construed as limited to the embodiments set forth herein. Those skilled in the art will appreciate that various modifications and equivalent embodiments may be possible. Accordingly, the technical scope of the present invention should be defined by the following claims.

110: electromagnetic stirrer 111: coil core
120: Casting line 121: Bath surface
130: mold 140:
141: guide member 142: horizontal part

Claims (11)

A mold into which molten steel is injected;
A transferring unit connected to the mold and transferring the casting material drawn from the mold; And
And a plurality of electromagnetic stirring devices provided to be spaced apart from each other in the feeding direction of the casting piece around the conveying portion.
The method according to claim 1,
Wherein the plurality of electromagnetic stirring apparatuses are located in a section where the solidification fraction of the cast steel is 0.3 to 0.9.
The method according to claim 1,
The transfer unit
A vertical portion connected to the lower end of the mold;
A horizontal part for horizontally feeding the cast steel; And
And a curved portion connecting the vertical portion and the horizontal portion,
Wherein the plurality of electromagnetic stirring devices are provided around the curved portion.
The method according to claim 1,
And a guide member is disposed between the plurality of electromagnetic stirring devices.
The method according to claim 1,
Wherein an intensity of a current provided to each of said plurality of electromagnetic stirring apparatuses is 100 to 600 A.
The method according to claim 1,
Wherein the plurality of electromagnetic stirring devices have different intensities of electric current supplied to each of the plurality of electromagnetic stirring devices.
Injecting molten steel into a mold;
Transferring a casting material drawn from the casting mold; And
And stirring the non-solidified portion of the cast steel by using a plurality of electromagnetic stirring devices spaced apart from each other in the feeding direction of the cast steel.
The method of claim 7,
A vertical part connected to a lower end of the casting mold; A horizontal part for horizontally feeding the cast steel; And a curved portion connecting the vertical portion and the horizontal portion,
Wherein the plurality of electromagnetic stirring devices are provided so as to surround the curved portion of the conveying portion.
The method of claim 7,
In the stirring step,
Wherein the non-solidified portion of the center of the cast steel is agitated in a zone having a solidification fraction of 0.3 to 0.9.
The method of claim 7,
In the stirring step,
Wherein said non-solidified portion of said cast steel is agitated by said plurality of electromagnetic stirrers provided with an electric current intensity of 100 to 600 A.
The method of claim 7,
In the stirring step,
Wherein the electric currents provided to each of the plurality of electromagnetic stirring devices have different intensities.
KR1020140157172A 2014-11-12 2014-11-12 Continuous casting apparatus and Continuous casting method KR20160056623A (en)

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