JPS5976647A - Method and device for stirring molten metal for casting in continuous casting - Google Patents

Abstract

PURPOSE:To prevent the intrusion of slag and foam by acting a static magnetic field on the flow of the molten steel charged into a continuous casting mold and the flow of a part of the molten steel flowing down along the wall of the mold in the direction intersecting with the respective flow directions thereby decelerating the flow of the molten steel. CONSTITUTION:A static magnetic field 14a is acted on the flow 20 of the molten steel charged from an immersion nozzle 12 into a continuous casting mold 11 in the direction intersecting orthogonally with the flow direction near the inflow position thereof. The flow thereof is decelerated in conformity with a Fleming's rule according to the direction where the magnetic field 14a acts to force the dispersion and stirring. Upward dispersing flow 21 is thus generated in the flow 20, whereby the intrusion of slag and foam in the unsolidified casting region is effectively prevented and the dissipation of the slag and foam by floating are made easy. On the other hand, the remaining flow of the molten steel is stopped substantially and is intensified in dispersion and stirring by receiving the braking force proportional to the square of the velocity of said flow with the static magnetic field 17a from an excitation means 17 which acts in the transverse direction of a casting strand 15 across the flow direction right under the mold 11, whereby the another upward dispersion flow is generated and the effect for the above- described intrusion is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for stirring poured molten steel in continuous casting.

In a casting method using a continuous casting machine, it is common to supply molten steel from a tundish into a continuous casting mold directly or through a submerged nozzle. However, in the conventional continuous casting method, even if the discharge hole angle of the submerged nozzle is changed, the molten steel flow injected into the continuous casting mold deeply penetrates into the unsolidified casting area, resulting in the slag accompanying it. Similarly, air bubbles also penetrate deeply and are trapped in the solidified shell, and the difference in specific gravity between them and the molten steel prevents them from surfacing and escaping to improve the surface of the molten steel, resulting in a reduction in product quality. Ta.

Therefore, in order to solve this problem,
As disclosed in Japanese Patent Application No. 856, a technique has been proposed in which the flow of molten steel in a continuous casting mold is decelerated by a static magnetic field and dispersed and stirred. As shown in FIG. 1, an excitation means 2 consisting of a DC exciting electromagnet bundle or an electromagnet having a pair of magnetic poles is placed outside the continuous casting mold 1 at a position immediately after the molten steel flows into the continuous casting mold 1. The flow of the molten steel 5 is decelerated by applying a static magnetic field 6 to the molten steel 5 flowing into the continuous casting mold 1 from each injection port of the immersion nozzle 8 in a direction that intersects with the flow direction of the molten steel 5. This results in an upward dispersion flow. According to this technology, melt! a5
The generation of an upwardly dispersed flow effectively prevents the entrainment of slag and air bubbles, and also reduces the depth of penetration of the molten steel flow into the unsolidified casting area based on the deceleration of the flow, and prevents its solidification. By preventing collision with shell 8,
Obstruction of floating and escape of slag and air bubbles onto the surface of the molten steel and their capture by the solidified shell B are respectively prevented.

However, according to this technique, the penetration depth of the molten steel flow into the unsolidified casting region is approximately half that of the conventional technology, as shown in FIG. 2, but the penetration depth is still 2i. Therefore, even with this technique, there was a problem that deterioration in product quality could not be sufficiently prevented.

The present invention advantageously solves this problem by applying a static magnetic field to the flow of molten steel injected into the continuous casting mold in a direction intersecting the flow direction of the molten steel. The continuous casting strand is forced to decelerate to disperse stirring, and the remaining flow of the molten steel, which escapes the force and flows downward along the wall surface of the continuous casting mold, is caused to flow in a continuous casting strand directly below the continuous casting mold in a direction that intersects with this. The present invention provides a method for stirring poured molten steel in continuous casting, which comprises a combination of applying a static magnetic field to further slow down the flow and strengthening it by dispersion stirring, and a device directly used for carrying out the method. be.

The present invention applies a static magnetic field to the poured molten steel flow in a continuous casting mold, decelerates the flow, and disperses and stirs it in the L direction, thereby preventing the entrainment of slag and air bubbles.
In addition, by applying a static magnetic field directly under the continuous casting mold to the residual flow of molten steel that is not dispersed and stirred, this residual flow is also decelerated, and by dispersing and stirring, the unsolidified steel is This effectively prevents slag and air bubbles from entering the casting area, thereby making it easier to prevent slag and air bubbles from floating and escaping.

The present invention will be explained below based on illustrated examples.

FIG. 8 is a sectional view illustrating an apparatus for carrying out the method of the present invention, in which 11 is a continuous casting mold, 12 is an immersion nozzle for injecting molten steel into the continuous casting mold 11, and 18 is an immersion nozzle 12. It shows an inlet opening in the desired direction at the lower end of the figure.

Here, on the outside of the continuous casting mold 11, the immersion nozzle and the
Two sets of excitation means 14 made of DC excitation electromagnets or permanent magnets having a pair of magnetic poles are arranged in the vicinity of the condition injection position from 2 to there so that a static magnetic field 14a can be applied in the thickness direction of the continuous casting mold 11. Further, an excitation means 17 similar to that described above having a pair of magnetic poles sandwiching the casting strand 15 is disposed directly below the continuous casting mold 11 so as to directly oppose the solidified shell 16 of the casting strand 15.

As is clear from FIG. 4, which shows a cross section taken along line N-F/ in FIG. Core 18
and a coil 19 wound around this iron core 18, and a static magnetic field 17a generated by the coil 19 acts in the width direction of the cast strand 15.

According to the device configured in this way, the immersion nozzle 12
A static magnetic field 14a acts on the molten steel flow go injected into the continuous casting mold 11 in a direction perpendicular to the flow direction near the inflow position, so that the flow is caused by the static magnetic field 14.
Depending on the direction of action of a, the speed is reduced in accordance with Fleming's law to force dispersion and stirring. Therefore, an upward dispersion flow 21 is generated in the molten steel flow 20, effectively preventing slag and bubbles from being drawn into the unsolidified casting region, and facilitating their floating and escape.

On the other hand, the residual flow of the melt that is decelerated but not forced to undergo the above-mentioned dispersion stirring is caused by the excitation means 17 acting in the width direction of the cast strand 16 in the direct direction of the continuous casting mold 11, intersecting with the flow direction. The static magnetic field 17a from the flow rate is substantially stopped by the rml kJJ force proportional to the square of the flow velocity, and the dispersion agitation is enhanced, resulting in a separate upward dispersion flow 22. Therefore, the entrainment of slag and bubbles is more effectively prevented here, and their escape from the surface based on the difference in specific gravity is further ensured by piggybacking on the upward dispersion flow z2 and substantially stopping the residual flow. Become.

FIG. 5 is a sectional view showing a modification of the excitation means disposed in the straight line F of the continuous casting mold 11. Two sets of excitation means 28 and 24 are placed on both sides of the casting strand 15 and sandwich it in the thickness direction.
is placed, and a static magnetic field 28 is applied in the thickness direction of the cast strand 15.
a, 24a. Note that each of these excitation means 28 and 24 consists of an iron core and a coil as described above.

According to this example, the static magnetic fields 23a and 24a effectively act only on the part where the downward residual flow of molten steel occurs, so that the iron core distance of the excitation means can be shortened and the operating cost can be reduced. , it is possible to force dispersion stirring sufficiently effectively.

According to this example, by appropriately changing the shape of the iron core and the like, it is possible to sufficiently cope with changes in the downward residual flow caused by changes in the injection lobe pattern of the submerged nozzle.

As described above, the illustrated example of the present invention has been described. Depending on the pouring pattern of the immersion nozzle, the excitation means provided outside the continuous casting mold may be arranged in three or more sets, or in multiple stages on each side of the immersion nozzle. It can also be placed in

Therefore, according to the present invention, the excitation means provided under the continuous casting mold ensures that slag and air bubbles are prevented from being drawn in and floated out, thereby confining them within the casting strand and solidifying the shell. This brings about the remarkable effect that the product quality can be sufficiently improved by effectively preventing the trapping.

[Brief explanation of the drawing]

Fig. 1 is a sectional view illustrating the prior art, Fig. 2 is a line diagram showing the penetration depth of molten steel flow in the prior art and the prior art, Fig. 8 is a sectional view illustrating the device of the present invention, and Fig. 4 is a sectional view illustrating the prior art. This figure is a sectional view taken along the line II/-1/ in FIG. 8, and FIG. 5 is a sectional view showing a modification of the excitation means shown in FIG. 4. 11... Continuous casting mold 12... Immersion nozzle 1
3-! - Inlet 14, 1, 28, 24...excitation means 14a
, 17 a, 2B & , 24 a--Static magnetic field 15... Casting strand 16... Solidified shell 1B... Iron core 19... Coil 20
... Molten steel flow 21 , 22 ... Upward dispersion flow O Patent applicant Kawasaki Steel Corporation Figure 1 Figure 2 Meniscus and 10Q distance 1 cm Figure 3 Figure 41 Figure 5

Claims (1)

[Claims] Within the L4itJ mold, a static magnetic field is applied to the flow of molten steel injected into the mold in a direction crossing the flow direction of the molten steel to decelerate the flow and force fractional stirring. Also, J! I! A method for stirring poured molten steel in continuous casting, which comprises applying a static magnetic field that pinches the continuously cast strand directly below the mold to further slow down the flow and intensifying fractional stirring. At least one set of excitation means consisting of a DC-excited 1α magnet or a permanent magnet having a pair of magnetic poles sandwiching the continuous casting mold is disposed outside the continuous casting mold in a portion near the point where molten steel flows into the continuous casting mold. However, casting in continuous casting in which an excitation means consisting of a DC excited electromagnet or a permanent magnet having a pair of magnetic poles that directly oppose the solidified shell of the cast strand and sandwich the cast strand is placed directly below the continuous casting mold. Molten steel stirring device. & The stirring device for pouring molten steel in continuous casting according to claim 2, wherein excitation means are arranged to sandwich the cast strand in the width direction. 4L The device for stirring poured molten steel in continuous casting according to claim 2, wherein two sets of excitation means are arranged on both sides of a cast strand to sandwich the strand in the thickness direction.