JP2004291045A - Continuous casting mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To apply magnetic flux by an electromagnetic stirring device to a mold position other than the front part of a coil iron core, e.g., at the upper part of the mold near a meniscus. <P>SOLUTION: In the continuous casting mold provided with an electromagnetic stirring device, between an electromagnet consisting of an ac coil 24 coiled round an ac iron core 22 in the electromagnetic stirring device and a copper plate 8 of the mold, an iron core 40 for magnetic flux induction for forming a magnetic path in an oblique direction to the magnetic pole 28 of the electromagnet is arranged. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a mold for continuous casting, and more particularly to a mold for continuous casting that is preferably applied when reducing subepidermal defects generated near the surface of a continuously cast slab.
[0002]
[Prior art]
As a conventional continuous casting mold, a DC iron core 136 disposed along an outer wall of a mold made of a copper plate 108 is wound on each of the DC iron cores 136 as shown in an image of a cross section in which a main part of the mold is extracted in FIG. Some include an electromagnetic stirrer having a configuration in which the static magnetic field applied by the upper and lower DC coils 134 and the moving (oscillating) magnetic field applied by the upper and lower AC coils 124 are superimposed. Although not shown, there is also known a configuration in which two upper and lower magnetic poles are arranged on the back surface of the long side of the mold, and a DC static magnetic field and an AC moving magnetic field are superimposed on the magnetic pole arranged on one of the magnetic poles ( For example, see Patent Document 1).
[0003]
In such a mold for continuous casting, the iron core (magnetic pole) around which the coil constituting the electromagnet is wound is usually arranged perpendicularly to the copper plate 108. Was the highest, and was effective for molten steel in the front direction, which is the position of the copper plate (mold) closest to the iron core.
[0004]
However, in the electromagnetic stirrer, there is a case where it is desired to apply the magnetic flux generated from the magnetic pole to a direction other than the front direction of the iron core (perpendicular to the copper plate). For example, in a continuously cast slab, the influence on the occurrence of subcutaneous defects (powder entrapment, subcutaneous segregation) is near the meniscus (the surface of molten steel) where the thickness of the solidified shell is still small. Therefore, in order to reduce subepidermal defects, it is effective to increase the cleaning effect on the shell interface by electromagnetically stirring molten steel in the vicinity of the meniscus. For this purpose, it is necessary to apply a magnetic flux to the vicinity of the meniscus.
[0005]
[Patent Document 1]
JP-A-10-305353
[Problems to be solved by the invention]
However, in the continuous casting mold as shown in FIG. 10, since the magnetic flux can be applied only in the front direction of the coil iron core, it is difficult to apply the magnetic flux in the vicinity of the meniscus in the upper part of the mold, for example. Since the electromagnet constituting the stirrer is fixed and supported by the back frame, there is a problem that even if an attempt is made to install the magnetic pole (iron core) near the meniscus, the installation space is restricted by the back frame.
[0007]
The present invention has been made in order to solve the above-mentioned conventional problems, and it is possible to apply magnetic flux by an electromagnetic stirrer to a mold position other than the front of a coil iron core. It is an object of the present invention to provide a continuous casting mold capable of applying a magnetic flux to a portion above a mold close to a meniscus even when receiving a mold.
[0008]
[Means for Solving the Problems]
The present invention relates to a continuous casting mold provided with an electromagnetic stirrer, wherein a magnetic flux guiding iron core that forms a magnetic path oblique to a magnetic pole of the electromagnet between an electromagnet and the mold of the electromagnetic stirrer. By disposing the above, the above-mentioned problem has been solved.
[0009]
That is, in the present invention, the magnetic flux generated from the electromagnet included in the electromagnetic stirring device can be applied to the mold position oblique to the magnetic pole of the electromagnet by the magnetic flux guiding iron core. Therefore, for example, when the voltage is applied to the vicinity of the meniscus of the molten steel in the mold, the stirring efficiency can be improved, so that the occurrence of subcutaneous defects on the slab can be effectively prevented and reduced.
[0010]
Japanese Patent Application Laid-Open No. 59-70445 discloses an example in which an iron core is provided obliquely with respect to the direction of drawing a slab. And other problems.
[0011]
Further, in the present invention, the magnetic flux guiding iron core may be formed in a laminated structure in which an insulating material and a magnetic material are laminated along a magnetic path direction, and It may be formed so that the thickness gradually decreases. Further, the magnetic flux guiding iron core may be incorporated in a back frame. Further, the magnetic flux guiding iron core may be arranged close to the magnetic pole of the AC moving magnetic field, and a static magnetic field may be further superimposed on the AC moving magnetic field.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0013]
FIG. 1 is a schematic cross-sectional view showing an example of a continuous casting mold for steel suitable for carrying out the present invention. In FIG. 1, 10 is a mold, 12 is an immersion nozzle, 20 is an oscillating magnetic field generator, 22 is a comb-shaped iron core, 24 is an AC coil wound around the iron core 22, 26a and 26b are AC power supplies, 28 is a magnetic pole. The AC magnetic field applied by the AC coil 24 is superimposed on the static magnetic field of the orthogonal coil 34 connected to the DC power supply 32 of the static magnetic field generator 30.
[0014]
In the mold for continuous casting of the present embodiment, continuous casting is performed while applying a magnetic field to molten steel in the mold 10 having opposed long sides and short sides. The applied magnetic field is a magnetic field oscillating in the long side direction of the mold (hereinafter also referred to as an oscillating magnetic field) and a static magnetic field in the thickness direction. The applied oscillating magnetic field is an alternating magnetic field having the long side direction of the mold as an application direction, the direction of which is periodically inverted, and is a magnetic field that does not induce macro flow of molten steel.
[0015]
The oscillating magnetic field can be generated using the oscillating magnetic field generator 20. In the oscillating magnetic field generator 20, a comb-shaped iron core 22 having three or more (twelve in the figure) comb teeth in the long side direction of a mold is used, and a coil 24 is arranged on these comb teeth to form a magnetic pole. 28. The magnetic pole 28 adjusts the winding of the coil and the alternating current flowing through the coil so that adjacent magnetic poles have different polarities (N and S poles). The winding direction of the coil between the adjacent magnetic poles is set to the opposite direction, and the current flowing through the coil is set to an alternating current having the same phase and a predetermined frequency, or the winding direction of the coil between the adjacent magnetic poles is set to the same direction. It is preferable that the flowing current be an alternating current having a predetermined frequency and a phase shifted between adjacent magnetic poles.
[0016]
In the continuous casting mold of the present embodiment, since adjacent magnetic poles have different polarities, the electromagnetic force acting on molten steel between adjacent magnetic poles and the electromagnetic force acting on molten steel between adjacent magnetic poles are the The directions are almost opposite, and macro flow of the molten steel is not induced. Further, since the current flowing through the coil is an alternating current, the polarity of each magnetic pole is reversed at a predetermined cycle, and vibration can be induced in the molten steel near the solidification interface in the long side width direction of the mold. Thereby, trapping of inclusions and air bubbles at the solidified shell interface can be suppressed, and the surface quality of the slab can be significantly improved.
[0017]
FIG. 2 shows a cross-sectional view of a main part of the continuous casting mold according to the first embodiment of the present invention.
[0018]
The mold of this embodiment is provided with an electromagnetic stirrer in the vicinity of the copper plate 8 constituting the mold, similarly to FIG.
[0019]
In this electromagnetic stirrer, a static magnetic field is formed by a DC coil 34 wound around a two-stage DC iron core 36, and is superimposed on an oscillating (AC) magnetic field generated by an upper AC coil 24 wound around the iron core 22. It has become so.
[0020]
The iron core 36 around which the lower DC coil 34 is wound is longer than the upper stage and extends to a position close to the copper plate 8. The upper stage includes an electromagnet formed by the AC coil 24 and the molded steel plate 8. A magnetic flux guiding iron core 40 that forms a magnetic path obliquely upward with respect to the magnetic pole 28 is disposed between the magnetic poles 28. Note that FIG. 1 corresponds to a cross section in a plane direction passing through the DC coil 34 and the AC coil 24 in the upper stage in FIG. However, the magnetic flux guiding iron core is omitted.
[0021]
FIG. 3 schematically shows the relationship between the magnetic flux induction iron core 40 and the three magnetic poles 28 corresponding to the leading end portion of the comb tooth-shaped iron core (AC iron core) 22 omitting the AC coil 24. As described above, the magnetic pole 28 is disposed obliquely upward with respect to the horizontally disposed magnetic pole 28, and the extension direction thereof coincides with the vicinity of the meniscus position shown in FIG.
[0022]
The AC coil 24, the DC coil 34, the magnetic flux guiding iron core 40 and the like constituting the electromagnetic stirrer (oscillating magnetic field generator, static magnetic field generator) are actually fixed by a back frame made of a nonmagnetic material, for example, stainless steel. It is attached to the long side wall of the mold 10 while being supported. FIG. 4 is a cross-sectional view showing an image in which the AC iron core 22 and the DC iron core 36 omitting the coil and the magnetic flux guiding iron core 40 are fixed and supported by the back frame 50 attached to the molded copper plate 8. Indicated by However, dimensions such as the thickness of the iron core are changed from FIG. 2 for easy understanding.
[0023]
As shown in FIG. 4, a cooling water pipe (cooling water channel in the figure) 52 is formed inside the back frame 50, and the magnetic flux guiding iron core 40 is located at a position avoiding the pipe 52. The magnetic flux guided by the magnetic flux guiding iron core 40 is applied to a mold position in the vicinity of the meniscus obliquely above as described in detail below.
[0024]
The magnetic flux guiding iron core 40 will be described in detail. As schematically shown in an enlarged perspective view of FIG. 5, a magnetic material (iron plate) 40A and an insulating material 40B are alternately stacked along the magnetic path direction. It has a structure. As this insulating material, for example, aramid fiber can be mentioned. Further, as a specific example of the laminated structure, a structure in which the thickness of the insulating material is about 0.5 mm and about 30 magnetic materials having a thickness of 5 to 10 mm are laminated.
[0025]
As a result of such a laminated structure, the eddy current loss generated by the fluctuating magnetic field generated by the AC coil 24 can be reduced, and the stirring efficiency can be improved. Further, the application position of the magnetic flux can be set without being restricted by the coil size.
[0026]
As described in detail above, according to the present embodiment, the magnetic flux guiding iron core 40 enables the magnetic flux to be concentrated and applied to the mold height near the meniscus, thereby improving the stirring efficiency with respect to the molten steel near the meniscus. The cleaning effect can be improved. Actually, when a slab was cast using the continuous casting mold of the present embodiment, the incidence of subcutaneous subsurface defects was reduced by 30% as compared with a slab manufactured using a conventional mold without a magnetic flux guiding iron core. Could be reduced.
[0027]
FIG. 6 schematically shows a perspective view of a magnetic flux guiding iron core applied to the second embodiment according to the present invention.
[0028]
This magnetic flux guiding iron core 40 has a thicker coil 24 side and a thinner taper on the copper plate 10 (mold) side, and a plurality of magnetic materials 40A whose thickness gradually decreases toward the mold side are laminated with an insulating material 40B therebetween. It has a laminated structure. By forming the plate material 40A to be laminated in a tapered shape and making the entire iron core 40 tapered, the magnetic flux density at the application position can be further increased, so that the local stirring efficiency can be further improved. It becomes possible.
[0029]
When the continuous casting was actually performed by the continuous casting mold of the present embodiment, the occurrence rate of subcutaneous subcutaneous defects of the cast slab could be further reduced by 10% as compared with the case of the first embodiment shown in FIG. .
[0030]
FIG. 7 is a sectional view corresponding to FIG. 4 of the first embodiment, showing a feature of the third embodiment according to the present invention, and FIG. 8 is a perspective view corresponding to FIG.
[0031]
In the present embodiment, the magnetic flux guiding iron core 40 is disposed obliquely downward as also shown in FIG. 2 by a two-dot chain line. By doing so, the magnetic flux can be applied in the direction in which the AC iron core 22 extends, that is, below the front of the magnetic pole 28, and the occurrence of internal defects in the cast slab can be effectively prevented.
[0032]
FIG. 9 is a perspective view corresponding to FIG. 8, showing the features of the fourth embodiment according to the present invention.
[0033]
In the present embodiment, the magnetic flux guiding iron core 40 is directed downward as in the case of the third embodiment, and at the same time, as in the case of the second embodiment, the coil 24 side is thick and the copper plate 10 side is thin. It has a laminated structure with a taper. With such a tapered shape, the magnetic flux can be further concentrated and applied obliquely downward.
[0034]
In the above embodiment, the case where the magnetic flux guiding iron core 40 has a laminated structure has been described, but the magnetic flux guiding iron core 40 does not necessarily have to have a laminated structure. Further, the forming materials and dimensions are not limited to those described above.
[0035]
【The invention's effect】
As described above, according to the present invention, even when the installation space is limited by the back frame, the magnetic flux by the electromagnetic stirrer is applied to a mold position other than the front of the coil iron core, such as the top of the mold near the meniscus. be able to.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a cross section in a plane direction passing through an upper electromagnet of a continuous casting mold which is an example of the present invention. FIG. 2 is a schematic partial sectional view schematically showing a main part of the continuous casting mold. 3 is a schematic perspective view showing the relationship between the iron core of the AC electromagnet and the magnetic flux guiding iron core. FIG. 4 is a longitudinal sectional view schematically showing the relationship between the magnetic flux guiding iron core and the back frame in the first embodiment. 5 is a schematic perspective view showing characteristics of a magnetic flux guiding iron core applied to the first embodiment. FIG. 6 is a schematic perspective view showing characteristics of a magnetic flux guiding iron core applied to a second embodiment. FIG. 8 is a longitudinal sectional view schematically showing a relationship between a magnetic flux guiding iron core and a back frame according to the second embodiment. FIG. 8 is a schematic perspective view showing characteristics of a magnetic flux guiding iron core applied to the third embodiment. FIG. 1 is a schematic perspective view showing characteristics of a magnetic flux guiding iron core applied to a fourth embodiment. A schematic partial cross-sectional view schematically showing a main portion of a conventional continuous casting mold EXPLANATION OF REFERENCE NUMERALS
8 Copper plate 10 Mold 12 Immersion nozzle 20 Oscillating magnetic field generator 22 Comb-shaped iron core 24 AC coils 26a and 26b AC power supply 28 Magnetic pole 30 Static magnetic field generator 32 DC power supply 34 DC coil 36 ... DC iron core 40 ... Flux induction iron core 40A ... Magnetic material (iron plate)
40B: insulating material 50: back frame 52: cooling water piping

Claims (6)

In a continuous casting mold equipped with an electromagnetic stirring device,
A continuous casting mold, wherein a magnetic flux guiding iron core forming a magnetic path oblique to a magnetic pole of the electromagnet is disposed between the electromagnet and the mold of the electromagnetic stirring device. 2. The continuous casting mold according to claim 1, wherein the magnetic flux guiding iron core is formed in a laminated structure in which an insulating material and a magnetic material are laminated along a magnetic path direction. 3. 3. The continuous casting mold according to claim 1, wherein the magnetic flux guiding iron core is formed such that a thickness gradually decreases toward a mold side. 4. The mold for continuous casting according to claim 1, wherein the magnetic flux guiding iron core is incorporated in a back frame. The continuous casting mold according to any one of claims 1 to 4, wherein the magnetic flux guiding iron core is arranged near a magnetic pole of an electromagnet that generates an AC moving magnetic field. The mold for continuous casting according to claim 5, wherein the AC moving magnetic field is superimposed on a static magnetic field.

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