FORM 2
THE PATENT ACT 1970
(39 OF 1970)
&
The Patent Rules, 2003
COMPLETE SPECIFICATION
(See Section 10 and Rule 13)
1 TITLE OF THE INVENTION : A TUNDISH ADAPTED FOR REDUCTION IN RESlPUAL METAL LOSSES AND A METHOD THEREOF.
2 APPLICANT (S)
Name : JSW Steel Limited.
Nationality : An Indian Company.
Address : Jindal Mansion, 5-A, Dr. G. Deshmukh Marg, Mumbai State of Maharastra, India. - 400 026,
3 PREAMBLE TO THE DESCRIPTION
COMPLETE
The following specification be performed. particularly describes the invention and the manner in which it is to

3 JUL 2008

FIELD OF THE INVENTION
The present invention relates to a tundish in continuous casting operations in steel plants and, in particular, to a tundish which is adapted for reduction in residual metal loss in continuous casting operations in steel plants without affecting the desired residence time of molten bath in tundish required for favored inclusion floatation and yet achieving advantageously reduction in volume of end skull in tundish and improved productivity of steel. Importantly, the invention provides for an improved configuration of the tundish directed to on one hand favour reducing residual metal in tundish and thus increasing the yield of casting steel and on the other hand also avoiding the possible entrapment of slag at upper layer of molten bath due to vortex motion at exit from tundish bottom, even when the surface level of liquid metal goes down in tundish towards end of a sequence casting. Advantageously, the tundish of the present invention with improved and selective configuration ensure reduction in the volume of residual end skull in tundish with added favour of net gain of steel in each sequence while maintaining desired cleanliness of steel. The invention is thus having significant impact in steel production and economy and the prospects of wide scale application in large steel industries involving continuous casting plants.
BACKGROUND ART
The continuous casting plant in large integrated steel plants comprises a tundish, a mold, a mold oscillator, a group of cast-strand supporting rolls, rolls for bending and straightening the cast strand, rolls to pinch and withdraw the cast strands, a group of spray nozzles, a torch cutter for cutting the cast strand, a dummy bar for extracting the cast strand at the start of casting, and other components. In continuous casting the molten steel passes from ladle to mould through an intermediate buffer called tundish. The tundish is thus basically a flow distributor and is adapted to maximize the liquid steel residence time in order to promote inclusion floatation. The performance of a tundish is generally evaluated in terms of functional ability to ensure inclusion floatability, slag entrapment, solid skull etc. and these are the parameters and strong determining factors for tundish design including the fluid flow conditions derived therein.
Usually the continuous casting plant in steel making shops operate at high productivity and each tundish is used to cast 8-10 heats for a sequence of a similar grade. It is a common
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experience for casting of molten steel from the ladle to mould through the tundish as flow distributor, ensuring desired residence time for inclusion floatation avoiding slag entrainment, a considerable amount of steel is left in each tundish in the form of solidified skull at the end of a sequence casting. This is done to avoid the entrapment of upper slag into the mould by vortex formation as the level in the tundish goes down at the end of the cast. It is thus unavoidable to circumstantially loose significant quantity of residual metal ranging between 3 to 5 tonnes, in the tundish at the end of a sequence casting. Moreover, the amount of metal left and wasted increases with increase in the size of the tundish and significantly reduces the yield.
There has been thus a continuous need to on one hand reduce the residual molten steel at the end of a sequence casting and also on the other hand achieve steel maintaining desired cleanliness of steel by way of desired residence time for molten bath in tundish ensuring inclusion floatation avoiding significant slag entrainment or solid skull. Also, it is important to ensure that the fluid/liquid meta! flow conditions in tundish during pouring in mould is so maintained by way of selective configuration of tundish bottom and discharge arrangement that the yield of tundish could improve minimizing end skulls.
OBJECTS OF THE INVENTION
It is thus the basic object of the present invention to provide for a tundish adapted to on one hand reduce the residual metal loss as end skull in tundish in continuous casting in sequence and on the other hand also ensure the production of good quality steel, free of inclusions with improved productivity.
A further object of the present invention is directed to improvement in continuous casting of steel involving a tundish by way of providing for a tundish adapted to on one hand reduce the residual metal loss as end skull in tundish in continuous casting in sequence and on the other hand also ensure the production of good quality steel, free of inclusions with improved productivity.
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A further object of the present invention directed to a method of reduction in residual steel in tundish by providing for advantageous flow condition of liquid steel from tundish to mould and in the process favoring improved productivity of good quality steel.
A further object of the present invention is directed to a method of reduction in residual steel in tundish and yet ensures that the steel obtained is not subject to any degrading due to unwanted inclusions during the casting process.
SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention there is provided a tundish adapted for reduction in residual metal losses comprising:
an embedded pouring box ;
a dam for flow control of the liquid metal ;
a stopper based outlet for liquid metal; and
a wedge adapted to minimize the residual metal between the said outlet and dam
operatively connecting said pouring box and said outlet.
Preferably, in the above tundish adapted for reduction in residual metal losses the said stopper comprises a turbo stopper.
According to another aspect of the invention there is provided a tundish adapted for reduction in residual metal losses comprising selectively slotted dam adapted to selectively drain out the left residual metal.
According to yet another aspect of the present invention the same is directed to said tundish adapted for reduction in residual metal losses, wherein said slotted dam is provided with releasable stoppers at the slots for selectively opening and closing the slots.
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A still further aspect of the present invention is directed to said tundish adapted for reduction in residual metal losses wherein the slotted dam is selectively provided along with selective dam height such that the same does not influence the overall height at which the vortex forms and do not thus degrade the steel-According to another aspect of the present invention the same is directed to a method for reduction in residual metal loss in tundish using the tundish adapted for reduction in residual metal losses comprising:
Allowing the liquid metal from the pouring box into the outlet through said wedge such as to minimize the residual metal between the stopper and the dam.
According to yet another aspect of the present invention the said method comprises further draining out the last metal by selectively opening the dam slots at the later part of sequence which initially is maintained closed.
The details of the invention, its objects and advantages are explained hereunder in greater detail" in relation to the non-limiting exemplary illustrations as per the following accompanying figures:
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
Figure 1: is an illustration of the conventional design of tundish having usual fixed dimensions e.g. width, breadth and depth of liquid.
Figure 2: is an illustration of the tundish with improved configuration having provision for embedded pouring box, wedge and slotted dam according to the present invention.
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DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING FIGURES:
It is well known in the art of continuous steel casting plants that Tundish is used as an intermediate buffer in between the ladle containing molten steel and the caster mold to allow for the residence time of liquid steel in tundish to achieve desired inclusion flotation and performance in respect of desired slag entrainment or solid skull formation etc.
Reference is first invited to accompanying Figure 1 which illustrates such a conventional design of tundish generally having size and dimensions e.g. width, breadth and depth of liquid that are normally fixed and cannot be varied. Such a tundish basically includes a pouring box (PB) for receiving the hot metal in the tundish and an outlet (OT) for the metal from the tundish to the mould below. Such tundish configurations also usually include a dam (DM) adapted to favor the controlled flow of the hot metal from the pour box towards the outlet maintaining desired residence time of the metal in the tundish to avoid unwanted inclusions during casting of the metal.
It is however experienced that for casting of molten steel from the ladle to mould through such conventional tundish as flow distributor, ensuring desired residence time for inclusion floatation avoiding slag entrainment, a considerable amount of steel is left in each tundish in the form of solidified skull at the end of a sequence casting. While, the need to avoid the entrapment of upper slag into the mould by vortex formation as the level in the tundish goes down at the end of the cast is met there is considerable loss in significant quantity of residual metal ranging between 3 to 5 tonnes, in the tundish at the end of a sequence casting. In particular it was noted that the maximum amount of metal left was in the space between pouring box and the dam. Moreover, the amount of metal left and wasted increases with increase in the size of the tundish and significantly reduces the yield.
It is to meet the objective of reducing the residual metal in tundish and thereby gain such valuable metal lost in the process that the tundish of the present invention has been configured and adapted such that on one hand it favors reducing the residual metal loss as end skull in tundish in continuous casting in sequence and on the other hand also ensures
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the production of good quality steel, free of inclusions with improved productivity. An illustrative embodiment of the tundish of the invention is shown in accompanying Figure 2.
Reference is now invited to accompanying Figure 2 which illustrates the tundish in accordance with the present invention. As clearly illustrated in the figure the tundish of the invention includes the insertion of an appropriate wedge (WG) into the existing tundish with embedded pouring box (EPB) whereby by better control of the flow of the molten metal it was possible to bring down the amount of tundish skull. Studies have further revealed that, insertion of a wedge does not influence the hydrodynamic performance of the tundish.
Advantageously also according to yet further aspect of the invention, the remaining last portion of metal can also be drained by making the dary, slotted (SDM) which are initially maintained closed but opens up at a later part of the sequence. Such slotted dam provided for considerable advantages in terms of reducing the tundish skull further. It was also observed that suitably designed holes in the dan-, does not influence the over all heiciht at which vortex forms and does not degrade the steel. The accompanyinp Figure 2 clearly illustrates the use of the tundish basal design consisting of wedge, embedded pouring box and slotted dam according to the invention directed to provide for significant gains by minimizing the loss of residual metal. Importantly, the net gain of 2t of steel could be achieved in a sequence casting and no adver-se impact on cleanliness of steel could be observed with the improved design of tundish.
It is thus possible by way of the present invention to provide for a tundish having improved provision for further controlling flow conditions and ensuring reduction in residual metal loss in tundish. The method of the continuous casting using the present tundish configuration should thus favor increasing the yield significantly and thus favoring wide application of the tundish in large steel plants adopting continuous sequence casting.
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CLAIM:
1. A tundish adapted for reduction in residual metal losses comprising:
an embedded pouring box ;
a dam for flow control of the liquid metal ;
a stopper based outlet for liquid metal; and
a wedge adapted to minimize the residual metal between the said outlet and dam
operatively connecting said pouring box and said outlet.
2. A tundish as claimed in claim 1 wherein said stopper comprises a turbo stopper.
3. A tundish as claimed in anyone of claims 1 or 2 comprising slotted dam adapted to drain out the left residual metal.
4. A tundish as claimed in claim 2 wherein said slotted dam is provided with releasable stoppers at the slots for selectively opening and closing the slots.
5. A tundish as claimed in anyone of claims 1 or 3 wherein the slotted dam are selectively provided along with the dam height such that the same does not influence the overall height at which the vortex forms and do not thus degrade the steel.
6. A method for reduction in residual metal loss in tundish using the tundish as claimed in anyone of claims 1 to 4 comprising :
allowing the liquid metal from the pouring box into the outlet through said wedge such as to minimize the residual metal between the stopper and the dam.
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A method as claimed in claim 5 further draining out the last metal by opening the dam slots at the later part of sequence which initially remain closed.
A tundish adapted for reduction in residual metal losses and a method for reduction in residual metal loss in tundish using the same substantially as hereindescribed and illustrated with reference to the accompanying Figure 2.

dated this 2nd day of July,2008


Anjan Sen
Of Anjan Sen & Associates
(Applicants Agent)

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