JP4203440B2 - Molten metal flow control device - Google Patents

Description

  The present invention relates to a molten metal flow control device, and in particular, an electromagnetic stirrer that applies a circulating force to the molten metal in a mold, an electromagnetic brake device that applies a braking force to the downward flow of the molten metal, and the electromagnetic stirrer. It is suitable for use in a molten metal flow control device comprising a magnetic flux shielding plate for reducing mutual interference between the device and the electromagnetic braking device.

  In continuous casting in which slabs are produced from molten steel melted in a blast furnace, molten steel in a ladle is injected into a mold from an immersion nozzle through a tundish. The molten steel injected into the mold is drawn from the bottom surface of the mold and formed into a slab.

  As described above, when the molten steel is molded from the molten steel to the slab, if the temperature of the molten steel in the mold is not uniform with respect to the horizontal direction, surface cracking, shell fracture, and the like are likely to occur in the molded slab.

  In view of this, an electromagnetic stirrer of the opposed linear motor type is installed at the upper position outside the mold side wall, and an electromagnetic stirrer for circulating the molten steel in the mold to make the molten steel temperature uniform has already been proposed and put into practical use. Yes.

  Furthermore, if bubbles or inclusions are involved in the molten steel, the quality of the molded slab will deteriorate, so an electromagnetic braking device that suppresses the downward flow of the molten steel in the mold will be used to prevent the inclusion of these bubbles and inclusions. Installation is also proposed and put into practical use.

  Furthermore, Patent Document 1 discloses a technique in which a magnetic flux shielding plate is installed between the electromagnetic stirring device and the electromagnetic braking device to reduce mutual interference between the electromagnetic stirring device and the electromagnetic braking device. Are listed.

JP 2001-219255 A

  As described above, when a magnetic flux shielding plate is installed between the electromagnetic stirring device and the electromagnetic braking device, the space in the direction parallel to the back plate side surface between the electromagnetic stirring device and the electromagnetic braking device. Is often not enough. This is because, in the configuration in which the molten steel agitated and uniformed by the electromagnetic stirring device is braked by the electromagnetic braking device, if the electromagnetic braking device is arranged at a position far from the surface of the molten steel, the downward flow of the molten steel is caused in the mold. This is because it is not possible to sufficiently perform the function of suppressing and preventing bubbles and inclusions from being entrained in the molten steel.

Therefore, it is difficult to ensure a sufficient space between the electromagnetic stirring device and the electromagnetic braking device in a direction parallel to the side surface of the back plate. Accordingly, the size of the magnetic flux shielding plate may be increased to increase the magnetic flux shielding ability.
The present invention has been made in view of the above problems, and a small installation space in the direction parallel to the side surface of the back plate is small between the electromagnetic stirring device and the electromagnetic braking device, and a large magnetic flux shielding ability is obtained. An object of the present invention is to provide a magnetic flux shielding plate to be provided.

A molten metal flow control device according to the present invention is a molten metal flow control device for a metal slab having a magnetic flux shielding plate between an electromagnetic stirring device and an electromagnetic braking device, the electromagnetic stirring device, the electromagnetic braking device, In the magnetic flux shielding plate disposed between, a small thickness portion and a large thickness portion are provided along a direction perpendicular to the side surface of the back plate of the mold, and the region facing the coil and the yoke constituting the electromagnetic braking device is provided. The feature is that a large thickness portion is arranged.
In addition, another feature of the present invention is that the small thickness portion and the large thickness portion of the magnetic flux shielding plate are formed separately, and are configured as an integral magnetic flux shielding plate by welding or bolting. It is a feature.
Another feature of the present invention is that the magnetic flux shielding plate is made of an electromagnetic steel plate having a high magnetic permeability, and its easy axis (RD) is along a magnetic circuit formed by the magnetic flux shielding plate. The transverse axis (TD) perpendicular to the easy axis of the electromagnetic steel sheet is arranged so as to face a direction perpendicular to the direction along the magnetic circuit.

According to the present invention, in the magnetic flux shielding plate disposed between the electromagnetic stirring device and the electromagnetic braking device, the small thickness portion and the large thickness portion are provided along the direction perpendicular to the side surface of the back plate of the mold, and the electromagnetic braking is performed. Since the large thickness portion is arranged on the magnetic flux shielding plate in the region facing the coil and the yoke constituting the device, the magnetic resistance value at the upper portion of the electromagnetic braking device coil and the upper portion of the electromagnetic braking device yoke is reduced. Thus, the amount of magnetic flux passing can be increased, and the magnetic flux shielding ability of the magnetic flux shielding plate can be greatly improved.
According to another aspect of the invention, the small thickness portion and the large thickness portion of the magnetic flux shielding plate are configured separately, and the small thickness portion and the large thickness portion are integrally attached by welding or bolting. Since it did in this way, also in the existing magnetic-flux shielding board, the capability which prevents the mutual interference of an electromagnetic stirring apparatus and an electromagnetic braking device can be improved, without performing a big construction.
Further, according to another feature of the present invention, the magnetic steel plate is constituted by a magnetic steel plate having a high magnetic permeability, and is arranged so that its easy axis (RD) faces a direction along a magnetic circuit formed by the magnetic flux shielding plate. Since the transverse axis (TD) perpendicular to the easy axis of the magnetic steel sheet is arranged in a direction perpendicular to the direction along the magnetic circuit, the resistance value of the magnetic circuit formed by the magnetic flux shielding plate is further reduced. Thus, the ability of the magnetic flux shielding plate to prevent mutual interference between the electromagnetic stirring device and the electromagnetic braking device can be further improved.

(First embodiment)
FIG. 1 is a cross-sectional view illustrating the configuration of the molten metal flow control device according to the first embodiment, and an electromagnetic stirring device 11 for providing a circulating force to the molten steel 10 is installed above the mold 3. ing. The electromagnetic stirring device 11 includes an electromagnetic stirring device core 1 and an electromagnetic stirring device coil 2.

  Further, an electromagnetic braking device 12 that applies a braking force to the downward flow of the molten steel 10 is disposed in the middle stage of the mold 3. In the present embodiment, the electromagnetic braking device 12 is constituted by an electromagnetic braking device core 6, an electromagnetic braking device coil 7, and an electromagnetic braking device yoke 8.

  Further, a magnetic flux shielding plate 5 for shielding magnetic flux induced by the electromagnetic braking device 12 is disposed between the electromagnetic stirring device 11 and the electromagnetic braking device 12.

  By installing the magnetic flux shielding plate 5, out of the magnetic flux generated by the electromagnetic braking device 12, the magnetic flux leaking upward from the mold 3 is guided into the magnetic flux shielding plate 5, and the magnetic flux shielding plate 5 Can be passed. That is, the electromagnetic braking device core 6, the magnetic flux shielding plate 5, and the electromagnetic braking device yoke 8 form a closed loop magnetic path, and leaks upward in the magnetic flux generated by the electromagnetic braking device 12. Much of the magnetic flux can be passed through the closed loop magnetic path as shown by arrow Y in FIGS.

  Thereby, the magnetic flux generated by the electromagnetic braking device 12 leaks to the height region of the electromagnetic stirring device 11, and the adverse effect on the electromagnetic stirring action by the electromagnetic stirring device 11 can be reduced. 3 is a cross-sectional view of a portion indicated by an arrow A in FIG. 2, and FIG. 4 is a cross-sectional view of a portion indicated by an arrow B in FIG.

  As described above, in the present embodiment, the magnetic flux shielding plate 5 is configured by the small thickness portion 5a and the large thickness portion 5b formed to have a plate thickness larger than the small thickness portion 5a. And the area | region which opposes the upper part of the electromagnetic brake device coil 7 which bears the magnetic flux reinforcement | strengthening function of the electromagnetic brake device 12 and the upper part of the electromagnetic brake device coil 7 which is a magnetic flux generation source instead of the vicinity of the casting_mold | template 3 which wants to reduce a leakage magnetic flux. The large thickness portion 5b is arranged in the above. Thereby, the amount of magnetic flux passing through the upper part of the electromagnetic braking device coil 7 and the upper part of the electromagnetic braking device yoke 8 can be increased, and the magnetic flux shielding ability of the magnetic flux shielding plate 5 can be greatly improved.

  Table 1 below shows an electromagnetic stirrer in the case where only the small thickness part 5a is configured and in the case where the small thickness part 5a and the large thickness part 5b are configured like the magnetic flux shielding plate 5 of the present embodiment. 11 is a table showing measurement results of magnetic flux density caused at the height center of 11 and the height center of the electromagnetic braking device 12;

  In Table 1, the cross-sectional area in the longitudinal section is normalized by the cross-sectional area of the small thickness portion 5a, and the cross-sectional area is increased by 1.34 times by providing the large thickness portion 5b. The magnetic flux density is normalized by the magnetic flux density at the height center of the electromagnetic braking device 12 when only the small thickness portion 5a is present, and the magnetic flux density at the height center of the electromagnetic stirring device 11 in the small thickness portion 5a is It represents that the size is 1/20 of the height center of the braking device 12.

  Here, the Lorentz force that prevents the circulation of the molten steel 10 at the center of the height of the electromagnetic stirrer 11 caused by the direct current magnetic flux induced by the electromagnetic brake device 12 is proportional to the square of the magnetic flux density, and is thus understood from Table 1 above. As described above, when the large thickness portion 5b is provided, the magnetic flux density caused by the DC magnetic flux at the height center of the electromagnetic stirrer 11 is reduced to 52% of the reference magnetic flux shielding plate 5, so that the circulation of the molten steel 10 is hindered. Lorentz force is reduced to 27%.

  In contrast, at the center of the height of the electromagnetic brake device 12, the magnetic flux density is reduced to 96.1% and the braking force is reduced to 92.4%, but the reduction amount is the center of the height of the electromagnetic brake device 12. Much less than. That is, although the braking force at the height center of the electromagnetic braking device 12 slightly decreases, the generation of Lorentz force that hinders the circulation of the molten steel 10 can be reliably suppressed.

  The magnetic steel sheet constituting the magnetic flux shielding plate 5 is arranged such that its easy axis (rolling direction: RD) faces the direction of the space forming the magnetic circuit of the magnetic flux shielding plate 5, and is perpendicular to the easy axis of the magnetic steel sheet. A transverse direction (TD) is arranged so as to face a direction perpendicular to the direction along the magnetic circuit. The electrical steel sheet used in the present embodiment has values of, for example, a magnetic permeability of the easy axis (RD) of 30,000 and a magnetic permeability of the transverse axis (TD) of 1,000.

  On the other hand, a magnetic steel sheet having a normal non-directional permeability has, for example, a permeability of RD and TD of 10,000 to 17,000. Although the magnetic permeability in the thickness direction of the electrical steel sheet can be kept small, the magnetic steel sheet having high permeability with directionality can reduce the permeability in the transverse axis direction. It is important to use a magnetic steel sheet having high magnetic permeability having directionality in an appropriate arrangement.

  By configuring as described above, it is possible to prevent a region having a low magnetic resistance from being formed outside the magnetic flux shielding plate 5. Thereby, the magnetic flux generated by the electromagnetic braking device 12 can be prevented from adversely affecting the stirring action of the electromagnetic stirring device 11.

(Second Embodiment)
In the first embodiment, the example in which the magnetic flux shielding plate 5 is integrally formed is shown. However, the small thickness portion 5a and the large thickness portion 5b may be configured separately. As described above, when configured separately, the attachment of both may be fixed by welding or the like, but a structure that can be divided by bolting or the like may be adopted. In this way, maintainability can be improved.

  As described above, when the small thickness portion 5a and the large thickness portion 5b are separately configured, the existing magnetic flux shielding plate is modified to constitute the magnetic flux shielding plate 5 having the excellent advantages as described above. be able to. For example, as shown in FIGS. 5 (a) and 5 (b), a magnetic flux shielding plate having a short length in the vertical direction on the side surface of the back plate of the mold is regarded as the small thickness portion 5a and has a thickness that is thicker than the existing thickness. It is also possible to improve the magnetic flux shielding capability by adding a large part 5b.

(Third embodiment)
As shown in FIG. 6A, in the case of the magnetic flux shielding plate 50 having a sufficiently long magnetic flux shielding plate, the magnetic flux protruding from the electromagnetic stirring device 11 as shown in FIG. 6B. By providing the magnetic flux shielding plate 50b for increasing the thickness on the upper surface of the shielding plate 50, the magnetic flux shielding plate 5 similar to that of the first embodiment described above can be configured.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows the 1st Embodiment of this invention and shows schematic structure of the flow control apparatus of a molten metal. It is sectional drawing explaining the flow of the magnetic flux in the flow control apparatus of the molten metal of embodiment. It is a figure which shows the cross section of the arrow A part of FIG. 2, and demonstrates the flow of the magnetic flux of an electromagnetic braking device core part. It is a figure which shows the cross section of the arrow B part of FIG. 2, and demonstrates the flow of the magnetic flux of a magnetic flux shielding board. It is a figure which shows the 2nd Embodiment of this invention and demonstrates the 1st example which increased the large thickness part to the existing magnetic-flux shielding board. It is a figure which shows the 3rd Embodiment of this invention and demonstrates the 2nd example which increased the large thickness part to the existing magnetic-flux shielding board.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electromagnetic stirrer core 2 Electromagnetic stirrer coil 3 Mold 4 Back plate 5 Magnetic flux shielding plate 5a Thickness small part 5b Thickness large part 6 Electromagnetic braking device core 7 Electromagnetic braking apparatus coil 8 Electromagnetic braking apparatus yoke 10 Molten steel 11 Electromagnetic stirring apparatus 12 Electromagnetic Braking device 50 Magnetic flux shielding plate 50b with sufficient length Magnetic flux shielding plate for increasing thickness

Claims (3)

A molten metal flow control device for a metal slab having a magnetic flux shielding plate between an electromagnetic stirring device and an electromagnetic braking device,
In the magnetic flux shielding plate disposed between the electromagnetic stirring device and the electromagnetic braking device, a small thickness portion and a large thickness portion are provided along a direction perpendicular to the side surface of the back plate of the mold to constitute the electromagnetic braking device. The molten metal flow control device is characterized in that the large thickness portion is disposed in a region facing the coil and the yoke.   2. The molten metal flow according to claim 1, wherein a small thickness portion and a large thickness portion of the magnetic flux shielding plate are formed separately and are formed into an integral magnetic flux shielding plate by welding or bolting. Control device. The magnetic flux shielding plate is made of an electromagnetic steel plate having a high magnetic permeability, and is arranged so that its easy axis (RD) faces a direction along a magnetic circuit formed by the magnetic flux shielding plate, 3. The molten metal flow control device according to claim 1, wherein a transverse axis (TD) perpendicular to the magnetic circuit is oriented in a direction perpendicular to the direction along the magnetic circuit. 4.

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