DE3345015A1 - Process and apparatus for preventing the horizontal circulatory flow arising in the metal on emptying molten metals from a melt container with bottom tapping - Google Patents

Abstract

The invention relates to a process for preventing the horizontal circulatory flow arising, due to the churning effect, in the metal above the taphole and in the taphole itself, when emptying molten metals covered with slag on the melt surface, from a melt container via a bottom tapping, and the thereby caused entrainment of slag into the tapped stream. The invention is characterised in that the circulatory flow of the metal is disturbed or braked by moving or stationary lines of magnetic force passing through the metal approximately perpendicularly to this flow. Furthermore, the invention relates to an apparatus for performing this process with two electromagnetic inductors fitted near the taphole beneath the floor of the melt container and operated with three-phase current in the same direction for a moving magnetic field, and with DC or AC current for a stationary magnetic field, with a large pole pitch in comparison with the refractory wall thickness of the melt container. <IMAGE>

Description

Methods and devices for avoiding the

when emptying molten metals from a melting container horizontal circulation flow created in the metal with a bottom spout.

The invention relates to a method for avoiding the during Emptying molten metals from a melting container with a bottom spout in the Metal arising horizontal circulation flow according to the generic term of Main claim.

The invention further comprises devices for performing the Procedure.

When emptying molten metals from a melting container via a bottom spout arises in the metal above the spout through the so-called Vortex effect a horizontal circulation flow and thus a suction effect, the slag floating on the surface of the metal into the pouring stream can tear. This entrained slag is especially in those cases where the Metal emptied from a melting vessel with a bottom spout or hat cut into a pan. And from it in molds to form blocks or - @ via an intermediate container (tundish) with Bottom pouring in continuous casting systems to form a strand is undesirable. (Archive Eisenhüttenwesen (1983) No. 5, pages 187 ff.) The slag leads in the pan to undesirable reactions with the elements dissolved in the metal, like burn-off of aluminum and re-phosphorus in steel.

In liquid metal. of the block or strand can contain slag particles become trapped by the solidifying metal and lead to deterioration of the finished product.

So far, no methods have become known that running along with Slag from a melting vessel e.g. an oxygen inflation converter during the To prevent the emptying process effectively, there are methods and devices known, at the end of the emptying process, the outflow opening by stopper, slide To close compressed air or ball, but do not avoid them during the emptying process the entrainment of slag as a result of the circulation flow. The same goes for that Pan, especially when the metal level has sunk towards the end of pouring.

When casting steel in the continuous casting process, through the spout of the intermediate container in the continuous casting mold entrained slag the degree of purity of the steel strand deteriorate considerably. The the surface of molten steel Slag covering in the intermediate container is particularly entrained when the The fill level of the metal in the container is low towards the end of casting, because then the The suction effect caused by the rotation of the metal extends into the surface. In practice, one encounters such slag running along, which is caused by a suitable measuring device can be recognized (e.g. DE-PS 30 37 658) by streaks of the sink.

However, there is a much larger problem that has not yet been resolved in that outflow eddies are formed even when the intermediate container is at full zero can, at their core, slag from the surface with into the outflowing jet tear. This is particularly disadvantageous in the so-called sequence casting, where several Melts continuously poured one after the other via the intermediate container to form the strand and the intermediate container one during the pan change has a low level.

Every time metal comes out of a SchmeBbehalter aggravating the fact that the direction of rotation of such outflow effect is random. Even in a melting container that is constant due to its spatial dimensions Depending on the basic currents prevailing in the vessel, they rotate in the opposite direction Vortices are observed. Since the direction of rotation is not constant, the previous Attempts to prevent the metal from rotating, for example by means of electromagnetic stirring coils attached to the container control the rotary movement of the outflowing To compensate metal. Because the direction of rotation of the vortices is random and so is the Rotational strength can hardly be determined in practical operation, it can also be electromagnetic Forced circulation of the metal does not prevent the suction effect in the outflowing metal.

An electromagnetic orbital movement of the metal would even in the event that the rotation of the outflow vortex accidentally coincides with this orbit, movement is in the same direction, the suction effect and thus the entrainment of slag still amplify.

It is the object of the present invention to provide a method and devices to carry out the procedure to indicate with which it is possible to prevent the leakage liquid metals from a melting container via a bottom drain in the metal horizontal circulation flow regardless of their random direction of rotation brake and / or eliminate it entirely and thus avoid slag being carried away.

This problem is solved by what is laid down in the claims Characteristics.

Assumptions that the circulating flow of the metal through. sew on vertically to slow down this magnetic lines of force penetrating the metal, make use of it of two well-known principles namely 1. the linear motor (inductor) mi alternating and 2. the electromagnetic eddy current brake with stationary magnetic Field.

The inductors generate a traveling magnetic field, which is reason the eddy currents created in the metal have an electromagnetic force and a resulting movement of the metal generated. Given the present Invention causes e: inductor below the bottom of the melting container, immediately mounted next to the sink, operated with three-phase current, one formed vertically in the metal Cross flow (Fig. 1), which disturbs the circulation flow regardless of the direction of rotation, According to the principle of the electromagnetic eddy current brake are created by the movement of an electrical conductor in a standing position perpendicular to this movement magnetic field by induction eddy currents. It creates along with that magnetic field an electromotive force Kr3f (Lorenz force), which the movement of the electrical conductor is opposite, consequently the movement of the conductor (Melt) is braked.

In accordance with the present invention, the horizonta: rotating acts metal as a vertically moving conductor to a standing one penetrating the metal Magnetic field, which causes the said opposing force, which is always opposite Direction slows down the circulation flow.

The effect of both measures is greatest if, according to claim 2 the magnetic lines of force as parallel as possible and as close as possible to the outlet axis, which is also the axis of rotation of the circulation flow.

According to the device claimed in claim 3, the magnetic Field over two on both sides near the spout below the bottom of the melting pot attached electromagnetic inductors generated (Fig. 2a and 2b) with three-phase current in the same direction for the moving and with direct or alternating current for the standing magnetic field are operated.

The arrangement of two inductors is due to the symmetrical training of the magnetic field required. The pole pitch of the inductors must be as large as possible compared to the wall thickness of the bottom of the melting vessel according to claim 2 claimed course of the. to effect magnetic lines of force.

According to the device claimed in claim 4, the magnetic Field generated via two inductors, one of which acts as a magnetic pole below of the bottom next to the outlet, the other as a magnetic opposite pole so on an outer wall of the melting container is attached that part of the magnetic field is perpendicular is arranged for the horizontal circulation flow (Fig. 3). This device can also be used for large refractory \ and strengths if the n-: ch requirement claimed device is not applicable because of too large a pole pitch. Both inductors are in the device claimed according to claim 4 only with echsel or direct current operated because with this arrangement of the inductors only a stationary magnetic field is generated can be.

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Claims (4)

Claims: 1. Method for avoiding the melting liquid when emptying, on the melting surface of metals covered with slag from a melting vessel through a bottom spout in the metal above the spout and in the sink itself The vortex effect and the resulting horizontal circulation flow Entrainment of slag into the pouring stream, d u r c h e k e n n n z e i c h n e t that the circulating flow of the metal through approximately perpendicular to this the metal penetrating moving or standing magnetic lines of force gstört tez '.. is braked. 2. The method according to claim 1, d a d u r c h g e k e n n z e i c h n e t that the metal should be parallel to the pouring axis and as close as possible to the pouring jet running around magnetic lines of force is penetrated. 3. Vorriciitung according to claim 1 and 2, d a d u r c h g e k e n n e i c h.n e t that two below the bottom of the melting vessel next to the spout. attached electromagnetic inductors with three-phase current in the same direction for a moving and with direct --- or alternating current for a stationary magnetic field with Compared to the refractory wall thickness of the melting vessel operated with a large pole pitch will. 4. Apparatus according to claim 1 and 2, d a d u r c h g e k e n nz e i c hn e t that a standing magnetic field differs from an electromagnetic one Device is generated, which consists of two inductors with different magnetic Poland exists and with Direct or alternating current is operated, one pole below the bottom and the other on the outer wall of the melting vessel is appropriate.