AU703992B2 - Electromagnetic confinement of molten steel in a twin roll continuous caster - Google Patents

Description

-2- ELECTROMAGNETIC CONFINEMENT OF MOLTEN STEEL IN A TWIN ROLL CONTINUOUS CASTER The present invention relates to a twin roll continuous caster.

In a twin roll continuous caster as shown in Figs. 3 and 4, between tops of opposite ends of a pair of rolls 1 and 2 arranged horizontally and in parallel with each other, side dams 3 and 4 are abutted to confine a molten metal pool 5 above a nip between the rolls 1 and 2. Molten metal 6 is supplied to the pool 5 and is solidified on the surfaces of the rolls 1 and 2. The rolls 1 and 2 are rotated under this condition so that solidified shells formed on the surfaces of the rolls 1 and 2 are pulled down together to directly cast a sheet metal 7.

In the conventional twin roll continuous caster as 15 described above, the molten metal pool 5 above the nip between the rolls 1 and 2 must have no possible leakage.

For this purpose, the side dams 3 and 4 are abutted to the end surfaces of the rolls 1 and 2. This makes it difficult 0e09 to change the width of the sheet metal 7 to be produced.

To change the width of the sheet metal, there is no other means but to replace the rolls 1 and 2 with those having different length.

under such circumstances, in order to change the width of the sheet metal 7, the operation of the twin roll continuous caster must be stopped to replace the rolls 1 and 2, which causes decrease in production efficiency: 0 S.moreover, the replacement of the rolls 1 and 2 itself is much troublesome.

In view of the above, the present invention has its object to provide a twin roll continuous caster which can form a molten metal pool without using side dams and can therefore change the width of the sheet metal even during the operation.

The present invention provides a twin roll continuous caster, characterized in that an axially extending, annular recess for accommodation of a magnet is formed on each of opposite end surfaces of a pair of rolls arranged 22/7/96 -3horizontally and in parallel with each other; said magnets with polarities selected to generate magnetic field between ends of the rolls are inserted into the corresponding recesses; upper submersible electrodes which may be submersed into molten metal in a molten metal pool are arranged between tops of the rolls and near positions of said magnets: lower power-feeding rolls which may roll in contact with each of lateral ends of a sheet metal produced are arranged directly below a nip between the rolls; and circuits each having a DC power source are connected between the corresponding upper electrodes and lower rolls, respectively.

The twin roll continuous caster may further comprise width changing means for moving in unison the magnets, upper electrode and lower roll on each of the same sides in axial direction of the rolls.

Action of the present invention is as follows: Molten metal is supplied above the nip between the paired parallel rolls and is solidified on surfaces of the 20 rolls. The rolls are rotated under this condition so that the solidified shells formed on the surfaces of the rolls are brought together and are withdrawn downward to directly cast a sheet metal.

In this case, a DC power source is connected between the corresponding upper electrode and lower roll in each of the circuits at the opposite ends of the respective rolls S. to thereby supply electric current to the molten metal or the like at each of the opposite ends of the molten metal pool.

30 Then, because of -the magnets being arranged with properly selected polarities at each of the opposite ends .of the molten metal pool, Lorentz's forces directed *perpendicular to both the direction of electric current and the direction of magnetic field are generated in the molten metal pool.

By setting the directions of electric current and magnetic field to direct Lorentz's forces inwardly of the molten metal pool, the molten metal can maintained the S:P19873 22/7/96 4 molten metal pool by Lorentz's forces.

According to the present invention, since the upper electrode is submerged in the molten metal at each of the opposite ends of the molten metal pool and the lower roll is in contact with each of lateral ends of the sheet metal, electric current can be reliably concentrated to the molten metal at each of the opposite ends of the molten metal pool so that the electric current is not dispersed and strong Lorentz's forces can be generated.

Since the upper electrode and the lower roll are arranged at shortest distance positions, i.e. in the molten metal pool and at the exit side of the rolls, the electric current can be reliably fed with no interruption of electric continuity between the upper electrode and the lower roll.

Further, since the molten metal maintains the molten metal pool by Lorentz's forces, the width of the pool may be changed during the operation by activating the width changing means to move in unison the magnets, upper 20 electrode and lower roll mounted on the same side in the .axial direction. Thus, the width of the sheet metal to be produced may be easily changed.

-An embodiment of the present invention will be described in conjunction with the drawings.

Brief Description of the Drawings Fig. 1 is a side view of an embodiment of the present invention.

Fig. 2 is a plan view of Fig. i.

Fig. 3 is a side view of a conventional caster.

Fig. 4 is a plan view of Fig. 3.

Figs. 1 and 2 show an embodiment of the present invention.

A pair of rolls 8 and 9 are arranged horizontally and in parallel with each other. The rolls 8 and 9 have at their end surfaces annular recesses 11 to 14 extending in an axial direction 10 for accommodation of magnets mentioned hereinafter.

S:P19873 22/7/96 The recesses 11 to 14 may be formed by hollowing out the one-piece rolls 8 and 9 or may be defined by mutually engaged roll barrels and roll sleeves.

The rolls 8 and 9 are made of material such as stainless steel or copper so as not to interfere with magnetic fields. The rolls 8 and 9 may be internally cooled, if required.

Arranged in the recesses 11 to 14 of the rolls 8 and 9 are magnets 15 to 18 with polarities selected such that magnetic fields are generated at the opposite ends of the rolls 8 and 9.

More specifically, the magnets 15 and 17 placed in the corresponding recesses 11 and 13 on the adjacent rolls 8 and 9 have mutually different polarities and this also applies to the magnets 16 and 18 placed in the corresponding recesses 12 and 14 on the adjacent rolls 8 and 9. And the magnets 15 and 16 in the recesses 11 and 12 on the opposite ends of the roll 8 have one and the same polarity and this also applies to the magnets 17 and 18 in 20 the recesses 13 and 14 on the opposite ends of the roll 9.

As the magnets 15 to 18, either electromagnets or permanent magnets may be used. ••co On the other hand, arranged above and between the

S..

paired rolls 8 and 9 and slightly outwardly in the axial direction 10 of the positions of the magnets 15 to 18 are .a pair of auxiliary side dams 21 and 22 each of which has *arcuate side portions 19 and 20 slidably touching outer peripheral surfaces of the rolls 8 and 9.

Mounted on the auxiliary side dams 21 and 22 through an electrode support 23 are upper submersible electrodes 26 and 27 which may be submersed into a molten metal 25 in a molten metal pool 24. At the same time, arranged directly below the nip between the rolls 8 and 9 are lower powerfeeding rolls 29 and 30 which may roll in contact with lateral ends of a sheet metal 28. Connected between the corresponding upper electrodes 26 and 27 and the lower rolls 29 and 30 are circuits 35 and 36 comprising switches 31 and 32 and DC power sources 33 and 34, respectively.

S:P19873 22/7/96

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6 In the two circuits 35 and 36, the DC power sources 33 and 34 have opposite polarities.

More specifically, the circuit 35 has positive polarity at the side of the lower roll 29 whereas the circuit 36 has positive polarity at the side of the upper electrode 27.

Further, among the magnets 15 to 18, auxiliary side dams 21 and 22 and lower rolls 29 and 30, those on the same side are connected with the single support members 39 and via rods 37 and 38, respectively. Width changing means 41 and 42 such as cylinders are connected to the support members 39 and 40, respectively, so that, among the magnets to 18, auxiliary side dams 21 and 22 and lower rolls 29 and 30, those on the same side may be moved in unison in the axial direction 10 of the rolls 8 and 9.

As the width changing means 41 and 42, cylinders as shown in the figure may be used. Alternatively, jacking means, rack-and-pinion means, worm-and-worm-wheel means or other means may be used.

In the figure, reference symbols F and F' represent 20 Lorentz's forces generated in the molten metal Next, description will be given on mode of operation.

The molten metal 25 is supplied to an area covered by the auxiliary side dams 21 and 22 above the nip between the paired parallel rolls 8 and 9 to thereby form the molten metalpool 24.

Then, the molten metal 25 is solidified on surfaces of the rolls 8 and 9. The rolls 8 and 9 are rotated under this condition so that the solidified shells on the surfaces of the rolls 8 and 9 are brought together and are withdrawn 30 downward to directly cast the sheet metal 28.

In this case, the switches 31 and 32 are turned on to 0.*0 connect the DC power sources 33 and 34 between the .s corresponding upper electrodes 26 and 27 and the lower rolls 29 and 30 in the circuits 35 and 36, respectively, to supply electric current to the molten metal 25 or the like at the opposite ends of the molten metal pool 24.

Then, because of the magnets 15 to 18 at the opposite ends of the molten metal pool 24 having properly selected S:P19873 22/7/96 7 magnetic polarities, Lorentz's forces F and F' are generated in the molten metal 25 which are applied perpendicular to the direction of electric current and the direction of magnetic field.

By setting the directions of electric current and magnetic field such that the Lorentz's forces F and F' are directed inwardly of the molten metal pool 24, the molten metal 25 can maintains the molten metal pool 24 by Lorentz's forces F and F' without the auxiliary side dams 21 and 22.

Therefore, the auxiliary side dams 21 and 22 should maintain the molten metal pool 24 only in the initial stage of the operation. Thus, there is no need of strictly sealing the molten metal 25. If the upper electrodes 26 and 27 are supported by some means without the aid of the auxiliary side dams 21 and 22, the dams 21 and 22 may be removed after the molten metal pool 24 has been maintained by Lorentz's forces F and Further, it is also possible to arrange that side dams 3 and 4 similar to those shown in Figs. 3 and 4 are installed on the ends of the rolls 8 and 9 and only the upper electrodes 26 and 27 are moved together with the corresponding magnets 15, 17 and 16, 18 and lower rolls 29 and 30, respectively.

~In the present invention, the upper electrodes 26 and 27 are submersed into the molten metal 25 on the opposite ends of the molten metal pool 24 and the lower rolls 29 and 30 are contacted with lateral ends of the sheet metal 28.

As a result, electric current can be concentrated on the molten metal 25 at the opposite ends of the pool 24; and 30 electric current is not dispersed and strong Lorentz's forces F and F' can be generated.

Since the upper electrodes 26 and 27 and the lower rolls 29 and 30 are arranged at shortest distance positions, i.e. in the molten metal pool 24 and on exit side of the rolls 8 and 9, electric continuity between the upper electrodes 26 and 27 and the lower rolls 29 and 30 is not interrupted and reliable supply of electric current is ensured.

S:P19873 22/7/96 8 Further, since the molten metal 25 maintains the molten metal pool 24 by Lorentz's forces F and and not by the auxiliary side dams 21 and 22, the width of the pool 24 may be changed during operation by activating the width changing means 41 and 42 to move in unison, via the support members 39 and 40 and the rods 37 and 38, the magnets 17 and 16, 18 the auxiliary side dams 21 and 22, the upper electrodes 26 and 27 supported on the dams 21 and 22 via the electrode support member 23 and the lower rolls 29 and 30 on the same sides, respectively. This makes it possible to easily change the width of the sheet metal 28 to be produced.

It is to be understood that the present invention is not limited to the above embodiment and that various changes and modifications may be made without departing from the scope and the spirit of the invention. For example, combination and selection of polarities of the electrodes and magnets are not limited to those in the above embodiment.

As described above, according to the twin roll V continuous caster of the present invention, a molten metal pool may be formed without side dams and therefore width of sheet metal may be changed even during the operation.

e• S:P19873 22/7/96 9 THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. A twin roll continuous caster, characterized in that an axially extending, annular recess for accommodation of a magnet is formed on each of opposite end surfaces of a pair of rolls arranged horizontally and in parallel with each other; said magnets with polarities selected to generate magnetic field between ends of the rolls are inserted into the corresponding recesses; upper submersible electrodes which may be submersed into molten metal in a molten metal pool are arranged between tops of the rolls and near positions of said magnets; lower power-feeding rolls which may roll in contact with each of lateral ends of a sheet metal produced are arranged directly below a nip between the rolls; and circuits each having a DC power source are connected between the corresponding upper electrodes and lower rolls, respectively.

2. A twin roll continuous caster according to claim 1 further comprising width changing means for moving in unison the magnets, upper electrode and lower roll on each 20 of the same sides in axial direction of the rolls.

:DATED this 22nd day of July 1996 ISHIKAWAJIMA-HARIMA HEAVY INDUSTRIES COMPANY LIMITED and BHP STEEL (JLA) PTY LTD By their Patent Attorneys 25 GRIFFITH HACK CO Fellows Institute of Patent Attorneys of Australia.

S:P19873 22/7/96