JPH02235554A - Apparatus for controlling flow of molten metal in mold - Google Patents

Abstract

PURPOSE:To eliminate surface flaw on a cast slab and to improve the inner quality by setting one or more pairs of electromagnetic coil to facing sides of a mold at both sides of a submerged nozzle and impressing the same magnetic poles to the pair of the electromagnetic coils. CONSTITUTION:Static magnetic field (line of magnetic force) 4 is impressed in the mold 2 for supplying molten metal with the submerged nozzle 1. Then, one or plural pairs of the electromagnetic coils 3a, 3b, 3a', 3b' faced to the thickness direction of the mold 2 are set to the faced side of the mold 2 at both sides of the submerged nozzle 1, respectively. The same magnetic poles are impressed to the pair of electromagnetic coils 3a, 3b, 3a', 3b' mutually faced. By this method, advance effect to braking force at the meniscus part can be eliminated.

Description

[Detailed description of the invention] Industrial application field> This invention relates to a flow control device for molten metal in a mold. In general, in the continuous casting method in which molten metal is supplied into a mold using a submerged nozzle, and then pulled out and cast while being cooled in the mold and a secondary cooling zone, the molten metal in the mold and in the unsolidified part of the slab is It is well known that suppressing the metal flow promotes the floating of inclusions in the molten metal and is effective in improving the quality inside the slab.

One method of applying braking force to such a molten metal flow is an electromagnetic brake that applies a static magnetic field. FIGS. 8 and 9 show such an electromagnetic brake consisting of a long-side mold 2A and a short-side mold 2B. This is a conventional example applied to a slab mold 2 in which an immersion nozzle 1 having a flat discharge hole IA is arranged in the center, and a pair of electromagnetic coils 3 facing each other in the mold thickness direction are attached to the long side mold 2 on the left and right sides of the immersion nozzle 1.
The magnetic poles of a pair of electromagnetic coils 3 facing each other are set to different N and S poles, and lines of magnetic force 4 form a static magnetic field perpendicular to the casting direction.

The molten metal flow from the horizontal discharge hole IA of the submerged nozzle is
As shown in Figure 0, the flow crosses the static magnetic field at right angles, so an induced current is generated within the molten metal flow, and the interaction between this current and the static magnetic field causes an electromagnetic force F in the opposite direction to the molten metal flow. occurs, which slows down and brakes the molten metal flow. However, in the conventional magnetic flux distribution, braking force is applied not only to parts of the molten metal flow where braking force is necessary, but also to parts where it is unnecessary (even in the upward flow, the braking force is applied in the opposite direction). The electromagnetic force F acts), which has a negative effect on the quality of the slab product. In particular, if a braking force is applied near the meniscus at the top of the molten metal surface, the temperature of the molten metal will drop significantly, causing skinning, etc., and causing surface defects such as vertical cracks and pinholes.

In addition, in order to reduce the braking force near this meniscus, if the applied current that adjusts the strength of the magnetic flux is reduced,
The magnetic flux in the part that originally requires braking force also becomes small, and the braking force does not work sufficiently, making it impossible to achieve the original purpose. moreover,
Regarding the floating of inclusions, it is not possible to expect a dramatic improvement simply by applying a braking force to the molten metal flow. This invention is
This was created to solve the above-mentioned problems, and its purpose was to create an in-mold molten metal that can apply braking force only to the necessary parts and control the direction and speed of the molten metal flow. An object of the present invention is to provide a flow control device.

In the present invention, as shown in FIG. 1, the same magnetic pole is applied to a pair of electromagnetic coils 3 facing each other in the mold thickness direction on both sides of the immersion nozzle 1, and As shown in FIG. 2, lines of magnetic force 4 repel each other to form a static magnetic field in the central longitudinal section along the width direction of the mold 2.

As long as it is a repulsive magnetic field, 3ajJ-
The N pole and 3b may be S poles, or as shown in FIG. 4, all of them may be N poles, or all of them may be S poles.

Moreover, as shown in FIG. 3, i! on one side! The distribution form of the magnetic flux can also be changed by increasing the magnetic flux of the magnetic coils 3a and 3b, or by increasing the magnetic flux of the diagonal magnetic coils.

Furthermore, by changing the angle between the central axis of the electromagnetic coil 3 and the back surface of the long side mold 2A, it is possible to control the shape of the space where the magnetic flux density is low, where the magnetic fields generated from the same opposing magnetic poles collide.

Effect》 When a current is applied to each tM1 coil 3, repelling static magnetic fields are formed as shown in Figs. 1 and 2. In the downward flow from the horizontal discharge hole IA, a braking force in the opposite direction acts in the vicinity of the mold due to the magnetic flux in a direction perpendicular to the casting direction, similar to the conventional method, and the floating of inclusions in the molten metal is promoted.

Figure 2 shows that in the vicinity of the meniscus near the coil, the gradient of magnetic flux density in the direction perpendicular to the scene (the casting direction) is small, but the gradient of magnetic flux density in the parallel direction becomes large, and compared to the conventional case, the gradient of magnetic flux density increases toward the scene. Since the braking force acting on the flow is considerably small, a drop in temperature can be prevented. In addition, the discharge flow from the horizontal discharge hole IA is rectified by preferentially flowing through a space with a low magnetic flux density where the magnetic fields generated from the same magnetic poles facing each other collide, so the magnetic flux of each coil is changed or each By controlling the position and size of the space by changing the installation angle of the coil, the flow direction and its velocity distribution can be easily controlled.

<Example of implementation> As shown in Figs. 1 and 2, the electromagnetic coil 3 is placed close to the back side of the long-side mold 2A so that the position of its central axis in the casting direction almost coincides with that of the horizontal discharge hole IA. At the same time, a pair of electromagnetic coils 3 are connected by a yoke 5 in the width direction of the mold. It is preferable that each electromagnetic coil 3 is installed so that its central axis can be tilted vertically and horizontally with respect to the back surface of the long side mold 2A. The results of continuous casting using such a device are shown in Figures 5 to 7 together with the conventional method.As is clear from the graphs, the present invention can significantly reduce the braking force near the meniscus. , it is possible to eliminate the temperature drop near the meniscus and to reduce the occurrence of vertical cracks compared to the conventional method.

Further, in the present invention, since the discharge flow is rectified and a braking force is applied in the vicinity of the mold where inclusions are likely to be captured, inclusions under the surface of the slab can be reduced more than before.

Effects of the Invention> As described above, according to the present invention, a static magnetic field is formed in the mold by magnetic poles of the same polarity, which collide with each other. The discharge flow is rectified, and an optimal braking force can be applied to the flow of molten metal in the mold. As a result, the adverse effects of the braking force, especially in the meniscus portion, can be completely eliminated, and while surface flaws in the slab can be eliminated, the internal quality can also be improved.

[Brief explanation of the drawing]

1 and 2 are a plan view and a sectional view showing a flow control device according to the present invention, FIG. 3 is a plan view showing a state in which the strength of magnetic flux is changed, and FIG. 4 is a plan view showing a modified example. , Figure 5 is a graph showing the inclusion index, Figure 6 is a graph showing the incidence of vertical cracks,
FIG. 7 is a graph showing the temperature inside the mold, FIGS. 8 and 9 are a plan view and a cross-sectional view of a conventional electromagnetic brake device, and FIG. 10 is a cross-sectional view showing the molten metal flow and braking force. 1... Immersion nozzle, IA... Horizontal discharge hole, 2...
Mold for slab, 2A... Long side mold, 2B... Short side mold, 3... Electromagnetic coil, 4... Line of magnetic force, 5... Yoke. Figure Figure Figure Figure 10

Claims (1)

[Claims] (1) In a device that applies a static magnetic field to a mold into which molten metal is supplied by a submerged nozzle, one or more pairs of electromagnetic coils facing each other in the thickness direction of the mold are placed on opposite sides of the mold on both sides of the submerged nozzle. A flow control device for molten metal in a mold, characterized in that the same magnetic pole is applied to each pair of opposing electromagnetic coils.