CA2047779A1

CA2047779A1 - Casting system for the introduction of a melt

Info

Publication number: CA2047779A1
Application number: CA 2047779
Authority: CA
Inventors: Ralf Schneider
Original assignee: Individual
Current assignee: Vodafone GmbH
Priority date: 1990-07-27
Filing date: 1991-07-24
Publication date: 1992-01-28

Abstract

ABSTRACT OF THE DISCLOSURE

The invention relates to a casting system for the introduction of a melt from a first vessel to a second vessel, for example from a tundish into a continuous casting mold, or from a ladle into a tundish. The casting system is simple, compact and suitable for small mold cross sections, particularly with billet formats of about 90 x 90 mm2, in which casting can be effected with the exclusion of air.
The casting system has a first vessel which is a ladle or a tundish having a discharge opening, located on the bottom of the vessel, in a closure plane, a second vessel which is a tundish or a mold, an immersion tube, having an end surface, a passage opening on the end surface and a longitudinal axis substantially perpendicular to the end surface, with the passage opening located eccentric to the longitudinal axis of the immersion tube. The immersion tube is arranged below the discharge opening of the first vessel, with the end surface of the immersion tube engaging the discharge opening of the first vessel in the closure plane. The immersion tube extends into the second vessel below the melt level. The immersion tube is fastened, rotatable around its longitudinal axis with respect to the first vessel, so that the end surface of the immersion tube, which adjoins the discharge opening, blocks the flow of melt when the discharge opening and the passage opening are not aligned, and allows a flow of melt when the discharge opening and the passage opening are substantially aligned.

Description

2 ~i 4 7 7 ~ ~
TITL,E OF THE INYENTION

CASTING SY~TEM FOR TH13 INTRODUCTION OF A MELT

IELD OF INVENTION

The present invention relates to a casting system for the introduction of a melt from a tundish or ladle into a vessel such as a continuous casting mold, having a discharge opening arranged in the bottom of the tundish or ladle.

~7~7Y

BACKGROUND OF l['HE INVE~NTIC)N

Federal Republic of Germany AS 20 43 588 teaches that a casting system of the above-indicated type is known, in which the discharge opening of the vessel containing the liquid melt can be close~ by way of a rota~y valve. For this purpose a stationary apertured plate having a funnel-shaped passage opening, which widens ~owards the container, is arranged at the discharge opening of the container. The end sur~ace of the apertured plate facing away from the container is beveled. A turnable slide-valve plate, which is provided with a passage opening, is arranged flush on the beveled end surface of the apertured plate.
This slide-valve plate is held and guided rotatably in its peripheral region by co~Tesponding means for retaining and rotating. The beveled end surface of the aperture plate results in an axis of rotation with respect to the slide plate, forming an acute angle with the casting axis.
The arrangement of the structure disclosed in Federal Republic of Germany AS 20 43 588 has the disadvantage that the holding and turning means, acting in the peripheral regio of the slide-valve plate, is expensive to fabricate in order to obtain sufficient tightness.
Another disadvantage ,directly resulting from this design is that the di~ficult vperation of changing the slide valve plate must be frequently performed, which is necessary because of its short life.
Another casting system is known from Federal Republic of Germany Patent 27 44 443, whi(h also discloses a rotary slide valve closure. The slide-valve plate is arranged in a tumable frame and provided with a plurality of passage openings. There are three passage openings arranged 120 apart with respect to the middle or cer.ter of rotation of the valve ~J~77 7~
plate. By turning the frame together with the valve plate, one passage opening in each case can be brought below the discharge opening, for instance, oF a tundish. The valve plate is in this connection pressed by the frame over a large surface against a nozzle block at the discharge opening, and is turned under sliding mction. The common valve plate is large, due in part to the fact that there are severaJ passage openings provided in it. As a result, relatively large contact areas are also present in this known arrangement, resulting in the disadvantage that the force required to turn the valve plate is very high, due to the high friction. This turning force is filrther increased by the fact that a stationary immersion tube is pressed against the end surface of the slide plate which faces away from the tundish.
Furthermore, the entire holding and turning means are large and expensive.

2 ~ 7 ~

_JECTS OF THE INVENTION

It is therefore an object of the present invention to create a casting system, having a smail size and simple structure, for small mold cross sections, in particular having billet cross-sections of about 90 x 90 mm2, in which casting can be effected while excluding air.
It is also an object of the present invention to provide a casting system, having a small size and inexpensive structure which allows the transfer of melt from a ladle to a tundish while excluding air.
It is a further object of the present invention to provide a casting system which allows dependable filling, transport and treatment of the melt in the ladle without impairment by the otherwise customary slide closure, even in the event of a long period of treatment, or of mechanical damage during the transport operation.
It is a still further object of the present inverltion to provide an improvement in the quality of a molded steel product and an undisturbed flow path of melt during the casting procedure.

- 2~3~77~.~

SUMMARY OF THE INVENTION

According to one embodiment of the present invention, a casting system ~or introducing a melt from a tundish into a continuous casting mold, having a discharge opening arranged in the bottom of the tundish, is provided with an immersion tube arranged below the discharge port of the tundish. The tube, in the mold, extends to a level below the casting level, so that the axis of the discharge opening of the tundish is eccentric to the longitudinal axis of the mold. The immersion tube is fastened, rotatable around its longitudinal axis, to the tundish, with the longitudinal axis of the immersion tube substantially aligned with the longitudinal axis of the mold, and the end of the immersion tube which adjoins the discharge port acting as a closure element for the discharge port, so that the passage opening Iying in the end surface of the immersion tube is eccentric to the axis of rotation of the immersion tube, and the closu~e plane is substantially perpendicular or orthogonal to the axis of rotation and discharge.
The present invention therefore provides a rotary slide-valve plate integrated in an immersion nozzle, so that its passage opening can be shifted contimlously from "fully closed"
to "maximally open" with only one slide plate friction surface.
The arrangement of an immersion tube directly below ~he level of th~ discharge port of the tundish, results in the immersion tube extending, in the mold, to a level below the casting level, which permits casting with the substantial exclusion of air. The arrangement of the passage opening in the end of the immersion tube adjoining the discharge port makes it possible, in a particularly advantageous manner, to dispense with an additional slide-valve 7~J

plate. Another advantage is that the immersion tube has only one ~riction surface and thereby produces considerably lower ~rictional forces, which Facilitates the use of a smaller drive mechanism. ~3y the compact arrangement of the discharge port and the immersion tube, as well as close proximity of the rotation and discharge axes with respect to each other, the advantage is obtained that the immersion tube may also be of very small diameter.
In abov~-described apparatus in Federal Republic of (~ermany AS 20 43 588, a direct connection of the immersion t~be to the slide-valve plate, if implemented, would have the result that, upon the opening and closing of the slide-valve plate, the immersion tube would wobble or be displaced at the immersing end, precluding casting operations with narrow mold formats or those with restricted clearance.
The present invention also provides the advantage that the immersion tube may have an inside diameter which is larger than the inside diameter of the discharge opening, and the immersion tube is closed on its inlet side or its end surface except for a passage opening.
The passage opening preferably corresponds to the inside diameter of the discharge port, but it may also be larger or smaller. Such an immersion tube, which is of very simple construction, is easy to manufacture and handle.
In an alternative embodiment of the invention, the inside diameter of the immersion tube is approximately equal to the inside diameter of the discharge opening and an oblique canal, the longitudinal axis of which intersects the axis of the discharge opening and also the longitudinal or rotational axis of the irnmersion tube, thus providing a system where the discharge opening may communicate with the oblique canal when properly aligned. A
longitudinal canal may extend along the longitudinal axis of the immersion tube fr~m its free ~7~
end to the oblique canal. The advantage of such an arrangement is that the free end of the immersion tube dipping in, to the melt in the mold can have a very small diameter. As a further advantageous embodiment of such an immersion tube, the immersion tube may be tapered or widened with a funnel-shape in the region of the side facing the discharge port thus being tapered outwardly toward the end surface, and may have a collar on which the immersion tube can be supported or retained and rotated. The advantage of this arrangement is that the irnmersion tube can be held and turned in a particul rly simple manner.
In the case of both of the above-mentioned embodiments in accordance with the invention, due to the possibility of dispensing with a slide-valve plate, the advantages of structural simplification and a reduction of frictional forces are obtained. Further, the reduction in friction not only allows for a smaller drive mechanism, but also reduces wear.
According to another embodiment, the casting system of the present invention is also intended primarily for use on a ladle, the bottom of which has a discharge opening which can be closed by a removable stopper.

BRIEF DESCRIPrl[ON OF T~IE DRAWINGS

The pref~rred embodiments are shown by way of example in the accompanying drawings in which:
Fig. 1 is a first embodiment of a casting system with an immersion tube;
Fig. 2 is a second embodiment of a casting system with an immersion tube;
Fig. 3 is a partial sectional view of the bottom of a ladle provided with a discharge pOIt; and Fig. 4 is a section through a modified casting system according to Figs. 1 and 2- which can be fastened to the ladle bottom shown in Fig. 3.

2 ~

DETAILED DESCRIPTIO OF THE PREFERE?ED EMBODIMENTS

Fig. 1 shows the major components of a casting system according to a first embodiment of the present invention. The immersion tube 4 and the end surface 12 of the immersion tube 4, which acts as a valve and effects the closure, are formed of a single piece.
The axis of rotation 5 of the immersion tube 4 is substantially aligned with the axis 7 of the mold 10. Both the discharge opening 3 of the container 1 and the passage opening 14 of the immersion tube 4 are located eccentric with respect to axis of rotation 5 and axis 7 which are substantially aligned with each other. The position of the immersion tube 4 with respect to the discharge opening 3 of the container 1, which is shown in Fig. 1, represents the closed condition. In the open condition, the immersion tube 4 has its passage opening 14 turned directly below the discharge opening 3 of the container l so that the discharge opening 3 and the passage opening 14 are approximately aligned.
Fig. 2 shows the major components of a casting system according to a second embodiment of the invention. In this case, the axis of rotation S of the immersion tube 4 is substantially aligned with the axis 7 of the mold 10, and both the discharge opening 3 of the container 1 and the entrance opening on the end surface 12 of the immersion tube 4, facing the container 1, are arranged located eccentric to the axis of rotation 5. The lateral offset of the discharge opening 3 with respect to the axis of rotation 5 of the immersion tube 4 can be compensated for by an oblique canal 8 in the immersion tube 4. The immersion tube 4 has a longitudinal axis of rotation 5 along which a canal may connect the oblique canal and the free end of the immersion tube 4. The immersion tube 4 has a widene~ cross section in the outer ~ 2~7~

region, towards the container 1, and its outer profile may be tapered outwardly toward the end surface. The immersion tube 4 is provided in the region resting against the container 1 with a collar 13 which is connected in form-locked, i.e. interfitting or force-locked, i.e.
pressure mediated manner, with the turning and holding device 11, which is known in the art and need not be extensively described. The entire immersion tube 4 in this ~se may also be made as a single piece. Fig. 2 shows the casting system in open, or flow conducting, condition.
In accordance with the advantages described above, the casting system of the invention finds use, due to its compact construction, in particular in the field of the casting of small billet cross sections, preferably having a size of about 80 x 80 mm2 to about 100 x 100 mm2, particularly about 90 x 90 cm2.
Furthermore, the steel can be cast with a smaller overheat temperature, since the combined immersion tube and rotary slide valve has a very small area of contact with the molten steel and thus only small heat losses are likely bo occur.

2 ~ ~ 7 ~

shows lhe major c~mps)nents OI a part o~ the ladle in the re~ion of lh~
discharge port accordin~ t~ another embod~ment of the prcserl~ ~nvenLion. In the metal ~ottom ~4 of the ladl~ and within its refractory linlng 2S, a nozzle blo~k 26 i~ inserted, whieh rec~ives the di~harge port 21. The dischar~e openin~ of the dis~ar~e port ~1 is closed from ~he ~ottom of the ladle by a burnable ~oppa 22, which pre&e~ably colasists of pap~r. Above it, the dis6har~e opcnln~ 1~ fl11ed ~ granul~te 23, for ex~mpl~ sand.
Ourillg the filling of the ladls wllh melt and dlJring the mov~mcnt o~ the l~dle to the s~to of the sllcceeding opera~ios~3, and also durin~ secondary n~e~llur~ical measu~s to ~ car~ed out in lhe ladl~, ~uch as desu~furi~tion or vacuum treatment, lhe stop~r 22 is ~ecured by a pl~te 27 which is fa~tened, for instanc~, by w~dging, ~o ~he boUom ~4 of the 1~d1e. AT-PS 2g1 323, ~or ~xamp1e, sh~w~ a plate which i~ pre~scd below th~ plug wh~ch provides se¢uri~r trc~m ~he acciden~al di~lodging of ~ plug ~n ~ho dls~butor openin~, which would result in lh~
expulsion of ~hc sand, with ~he resul~ng unimpeded fiow of melt. AT-PS 207 OS3 ~hows a plate which can ~ swung ~ideways, out of the flow path. Mechanical ~uides for guiding slidin~ closure~ of castin~ laslle~ are ~escnbed in D~ )S 24 ~7 305.

-lOa-~7~

Fig. 4, which corresponds to the immersion tube 4 of Figs. 1 or 2, of the present invention, may be fastened below the ladle in the casting position, wieh the plate 27 eliminated. A discharge tube 28, which is an immersion tube and corresponds to the immersion tube 4 of Figs. 1 or 2t and indeed is given different nomenclature only to differentiate its location within the casting system from the immersion tube 4, is fastened below the ladle. By the cooperation of the discharge tube 28 with the discharge port 21 of Fig. 3, a rotary slide valve results due to the contact of the bottom surface 21' of the discharge port 21 and the end surface 28' of the discharge tube 28, which has an opening 30 for the passage of the melt. The opening 30 is located eccentric to ~he longitudinal axis 29 of the discharge tube 28. The discharge port 21 and discharge tube 28 are precisely aligned and so clamped with respect to each other by suitable centering devices, that the bottom surface 21' and the end sur~ace 28' abut against each other with substantially no gap. The discharge tube 28 is flanged, and supported by a member which interfits with the flange in such a manner th~t the siischarge opening of the discharge port 21 and the opening 30 of the discharge ~ube 28 form a rotary slide valve. When tbe opening 30 and the discharge opening of the discharge port 21 are substantially aligned, the thus formed rotary slide valve is fully open.
An oxygen-gas mixture is introduced into the discharge tube 28 prior to casting by means of a burn pipe, and the discharge opening of the discharge port 21 burned open so that the melt can flow into another vessel. The quantity of melt which flows per unit time 2 B4 7 7 7 ~3J

through the apparatus can be adjusted by rotation of the discharge tube 28 via a drive mechanism 31 in order to modulate the degree of alignment and therefore the area of the aperture of the siide valve. It is, of course, possible to modulate the flow during the molding operation to a level between no flow and maximal flow, if desired.
The casting system of the present invention results in the following advantages:
Dependable filling, transport and treatnnent of the melt in the ladle without impairment by the otherwise customary slide closure, even in the event of a long period of treatment, or of mechanical damage during the transport operation; reduction of the expense for the mechanical elements of the rotary slide valve closure itself; reduction of the arnount of air drawn in with the melt, since only a single sealing sur-face is present; and improvement in the quality of the molded steel product and an undisturbed flow path during the casting procedure.
It should be understood that the preferred embodiments and examples described herein are for illustrative purposes only and are not to be construed as limiting the scope of the present invention, which is properly delineated only in the appended claims.

Claims

1. A casting system for transferring a melt comprising:
a first vessel comprising an aperture defining a discharge opening, located on the bottom of said first vessel, in a closure plane;
a second vessel having a melt level;
an immersion tube, having an end surface, an aperture defining a passage opening on said end surface and a longitudinal axis substantially perpendicular to the end surface, said passage opening located eccentric to said longitudinal axis of said immersion tube, said immersion tube being arranged below said discharge opening of said first vessel, with said end surface of said immersion tube operatively engaging said discharge opening of said first vessel in said closure plane, said immersion tube extending into said second vessel to a level below said melt level, and said immersion tube being fastened, rotatable around its longitudinal axis with respect to said first vessel, so that said end surface of said immersion tube which adjoins said discharge opening blocks a flow of melt when said discharge opening and said passage opening are not aligned, and allows a flow of melt when said discharge opening and said passage opening are substantially aligned.

2. The casting system according to claim 1, wherein said first vessel comprises a tundish, said second vessel comprises a continuous casting mold having a longitudinal axis, said discharge opening of said tundish being located eccentrically to said longitudinal axis of said mold, and said longitudinal axis of said immersion tube being substantially axially aligned with said longitudinal axis of said mold.

3. The casting system for the introduction of a melt in accordance with Claim 1, wherein said immersion tube has an inner diameter which is greater than an inside diameter of said discharge opening and said immersion tube is closed on said end surface except for said passage opening, said passage opening having an inside diameter which is substantially equal to a diameter of said discharge opening.

4. The casting system for the introduction of a melt according to Claim 1, wherein said discharge opening has an inner diameter and an axis, said immersion tube having an inner diameter which is substantially equal to said inner diameter of said discharge opening;
said immersion tube further comprising an oblique canal having an axis, said axis of said oblique canal intersecting said axis of said discharge opening and said longitudinal axis of said immersion tube.

5. The casting system for the introduction of a melt in accordance with Claim 4, said immersion tube additionally comprising a collar on which the immersion tube can rest and turn and an outer wall being tapered outwardly toward said end surface.

6. The casting system for the introduction of a melt in accordance with claim 1, wherein said first vessel comprises a ladle for receiving the melt from a metallurgical furnace and for supplying the melt to a place of casting, said discharge opening of said ladle comprising a refractory lining for preventing penetration of the melt, said second vessel comprises a tundish for providing melt to a continuous casting mold, and said ladle bottom being closed from the outside by said immersion tube when said discharge opening and said passage opening are not aligned.