SE544399C2

SE544399C2 - System for fall teeming under vacuum of liquid steel

Info

Publication number: SE544399C2
Application number: SE2051074A
Authority: SE
Inventors: Martin Eriksson
Original assignee: Martin Eriksson
Priority date: 2020-09-14
Filing date: 2020-09-14
Publication date: 2022-05-10
Also published as: WO2022053478A1; SE2051074A1

Abstract

The invention relates to a system for fall teeming under vacuum of liquid steel (2) through a closable outlet opening (4a) in a bottom wall (1a) of a movable ladle (1) into a liquid steel receiving apparatus (A) and therefrom into a distributor (14), to which at least one distributor pipe (17) is connected discharging into a mould (24). Said liquid steel receiving apparatus (A) comprises a housing (9) having a through channel (9a) and an upper housing part (6) movably and sealingly arranged inside said through channel (9a). Said at least one distributor pipe (17) is provided with a flow restriction means (18) so that an upper end (6a) of said movable upper housing part (6) is forced upwardly by a static pressure from the liquid steel filling said liquid steel receiving apparatus (A) and acting upon lower end (6b) of said movable upper housing part (6).

Description

SYSTEM FOR FALL TEEMING UNDER VACUUM OF LIQUID STEEL Field of the Invention The present invention relates to a system for fall teemingunder vacuum of liquid steel according to the preamble of claim l.

Background of the Invention During fall teeming under vacuum, liquid steel is teemed froma ladle into a receiving housing from which it is distributedvia a distributor into at least one mould in which a vacuum isprovided. As an example, by fall teeming under vacuum theamount of oxygen of an ingot is reduced to about 20 ppm at a vacuum of about -0.9 bar.

The ladle with liquid steel has a closable outlet opening inthe bottom wall and is handled by a crane or is standing on a teeming car.

Before the teeming operation starts the closable outletopening in the bottom wall of the ladle has to be aligned withan inlet of the receiving housing and is lowered against thereceiving housing so as to abut against the same for achievingan airtight sealing between the closable outlet opening andthe inlet of the receiving housing which should be maintained during the teeming operation.

Object of the Invention An object of the invention is to provide an improved systemfor connecting the closable outlet opening in the bottom wallof the ladle with the inlet of the receiving housing in an airtight manner.

Thus, this object is achieved by the invention by providing asystem for fall teeming under vacuum of liquid steel through a closable outlet opening in a bottom wall of a movable ladle into a liquid steel receiving apparatus vacuum sealed andfluidly connected to said closable outlet opening andtherefrom into a distributor arranged on a distributor plate,to which distributor an upstream end of at least onedistributor pipe is vacuum sealed and fluidly connected, anoutlet end of which is placed in a mould sealingly arrangedunderneath said distributor plate and arranged to be filledwith liquid steel and provided with vacuum by a vacuum pipe,characterized in that said liquid steel receiving apparatuscomprises a housing having a through channel and an upperhousing part movably and sealingly arranged inside saidthrough channel, and that said at least one distributor pipeis provided with a flow restriction means enabling an upperend of said movable upper housing part to be forced upwardlyby a static pressure from the liquid steel filling said liquidsteel receiving apparatus and acting upon a lower end of saidmovable upper housing part whereby said upper end of saidmovable upper housing part is adapted to exert a force on saidclosable outlet opening in said bottom wall so as to provide amore powerful sealing between said upper end of said movable upper housing part and said closable outlet opening.

Brief description of drawings The invention will now be described by way of a non-limiting example with reference to the accompanying drawing, in which - Fig. l is a partial sectional side view of a systemaccording to the invention for teeming under vacuum liquidsteel from a ladle via at least one distributor pipe into atleast one mould before the teeming operation has started andshowing a vacuum valve of a liquid steel receiving apparatusin a closed position and with a meltable jet concentrating means discharging into a mould, the bottom of which is not shown, - Fig. la is an enlarged sectional side view of a portion ofthe inventive system shown in figure l, - Fig. lb is an enlarged sectional side of an portion of theinventive system shown in figure l, - Fig. lc is a view similar to the view shown in figure la ina further enlarged scale and without the vacuum valve, - Fig. 2 is a view similar to the view shown in figure l butduring teeming operation and showing the vacuum valve in anopened position and with the meltable jet concentrating meansbeing melted at its lower end as the level of the liquid steelraises in the mould, - Fig. 2a is a view similar to the view shown in figure lb butduring the teeming operation and showing the vacuum valve inan opened positioned, - Fig. 2b is an enlarged view of a part of a distributor plateand an upper portion of the mould during teeming operation andshowing a jet of liquid steel leaving an end of thedistributor pipe and diverging towards an inside of themeltable jet concentrating means, - Fig. 3 is a view similar to the view shown in figure 2 butwith a non-meltable jet concentrating means having a fixedlength which ends above/at the level of the finished ingot,and - Fig. 3a is a view similar to the view shown in figure2ashowing how a jet of liquid steel diverge towards the inside of the non-meltable jet concentrating means.

Description of preferred embodiments Figs. l, la, lb, and lc show the inventive system before theteeming operation has started, i.e. before the closable outletopening 4a in a bottom wall la of a ladle l is opened so as to teem liquid steel into the inventive system.

Fig. l is a partial sectional side view of a system accordingto the invention for teeming under vacuum liquid steel 2 fromthe ladle l into at least one mould 24. The ladle l has abottom wall la in which preferably a potty 3 is arranged. Theladle l filled with liquid steel 2 is preferably handled by acrane (not shown) for placing said ladle l in contact with a liquid steel receiving apparatus A.

In or below the bottom wall la a closable outlet opening 4a isprovided, possibly in the form of a slide gate having a slide5 for opening and closing the closable outlet opening 4a. Theclosable outlet opening 4a of the ladle l is shown placed inthe centre of and connected to the liquid steel receiving apparatus A.

More particularly, as can be inferred from figures la and lb,the liquid steel receiving apparatus A comprises a housing 9placed on a distributor plate 25 and having a through channel9a in which an upper housing part 6 is movably and sealinglyarranged. The upper housing part 6 can move in thelongitudinal direction of the through channel 9a and is sealedagainst an inner wall 9b of the through channel 9a by sealings8. The sealings 8 provide necessary friction so that the upperhousing part 6 will not sink down in the through channel 9a bygravity. At the bottom of the housing 9 a vacuum valve lO isarranged. Said vacuum valve lO is adapted to in its openedposition provide vacuum, via a distributor l4, at least onedistributor pipe l7, and at least one mould 24, in the housing9 from a vacuum pipe 27 connected to a suitable vacuum pump(not shown). The distributor l4 is preferably sealed to thehousing 9 by a distributor sealing l5. At least one distributor pipe l7 is connected to the distributor l4.

In figures l, la, and lb the vacuum valve lO is shown in its closed position. The distributor pipe l7 is arranged at said distributor plate 25 and extends from said distributor 14 toan upper portion of a mould 24 in which it discharges via a meltable jet concentrating means 20.

Moreover, in figure 1 the closable outlet opening 4a of bottomwall 1a of the ladle 1 is shown placed in contact with theupper housing part 6 via a sealing 7 arranged at an upper end 6a of the upper housing part 6.

Fig. 1b shows, in enlarged scale, a portion of the distributorplate 25 and an upper portion of the mould 24 together with preferred piping components.

More particular, the distributor plate 25 is placed on top ofthe mould 24 via an intermediate part 30 having a sealing 26against an upper end 24a of the mould 24. The vacuum pipe 27is in communication with the interior of the mould 24 forproviding a suitable vacuum of at most -0.9 bar, for example,in the mould 24, the distributor 14, and the piping components17, 20. The vacuum is maintained in these parts since thevacuum valve 10 is in its closed position. Said vacuum pipe 27by the vacuum pump (not shown) is arranged to suck outgas(air) from said liquid steel receiving apparatus A when thevacuum valve 10 is in its opened position and thus the mould24 at least until a surface of an ingot in the mould has frozen.

A vacuum duct 11 (see particularly figures 1, la and lb) canbe provided parallel to the vacuum valve 10 enabling vacuum toact on the space inside the liquid steel receiving housing A even in case said vacuum valve 10 is in its closed position.

Furthermore, a flow restriction means 18 is arranged in the atleast one distributor pipe 17 close to an outlet end 17b thereof.

In the embodiment shown in figures l, la, lb, lc, 2, 2a, and2b a meltable jet concentrating means 20 extends to close to abottom (not shown) of the mould 24 and is arranged to melt offas the liquid steel 2 fills the mould, i.e. it is adapted tomelt progressively at its end immersed into the liquid steelat the same rate as the level of the liquid steel raises inthe mould 24. This is made possible by making the meltable jetconcentrating means 20 of a steel grade having a lower meltingpoint that the melting point of the liquid steel 2 to be teemed.

Figures 2, 2a, and 2b show similar views as figures l, la, andlb except that said figures show the teeming operation inprogress, i.e. the liquid steel receiving housing A, thedistributor l4, the at least one distributor pipe l7 and themould 24 are filled with liquid steel 2.

After centring the closable outlet opening 4a of the bottomwall la of the ladle l relative to the liquid steel receivingapparatus A and lowering the ladle l until the closable outletopening 4a of the bottom wall la is in contact with the upperhousing part 6 via the sealing 7 arranged at the upper end 6aof the upper housing part 6, the ladle l being preferablylowered a bit further, a few centimetres, for example, so thatgood contact is established between the ladle l and the upperend 6a of the upper housing part 6, then vacuum is appliedthrough the vacuum pipe 27 to the system via the vacuum ductll, if provided, with the vacuum valve lO closed and theteeming operation starts by opening the slide 5. It is ofcause possible to apply vacuum to the vacuum pipe 27 also justbefore the closable outlet opening 4a of the bottom wall lahas established contact with the upper housing part 6.

In so doing, liquid steel 2 will flow into the liquid steel receiving housing A. At a certain level of the liquid steel in the liquid steel receiving housing A the vacuum valve lO willopen by floating due to density difference between the vacuumvale lO and the liquid steel 2, and liquid steel 2 will thusflow through the distributor l4 into the at least onedistributor pipe l7 and further through the flow restrictionmeans l8 via the jet concentrating means 20 into the mould 24.A stop means l2 is arranged at a lower end lOa of the vacuumvalve lO. In the open position of the vacuum valve lO the stopmeans lOa is adapted to abut on a stop surface l2a arranged ata lower portion of the housing 9, thus preventing the vacuum valve from floating up too much. See figure la.

In an embodiment a flotation body of the vacuum valve lO isprovided with a cavity lOb so as to increase its floatabilityin the liquid steel receiving housing A when filled with liquid steel. See figures l, la, and lb.

As the flow restriction means l8 restricts the flow of liquidsteel through said at least one distributor pipe l7, theliquid steel 2 will thus totally fill up the liquid steelreceiving housing A including the movable upper housing part6. See figures 2 and 2a. When the liquid steel 2 reaches alower end 6b of the movable upper housing part 6, the liquidsteel will, by hydraulic action, act on said lower end 6b andthereby lift and force the movable upper housing part 6upwards. This lifting force will press the upper housing part6 with its sealing 7, further against the closable outletopening 4a of the ladle l and thus improve the sealing betweenthe liquid steel receiving housing A and the closable outlet opening 4a.

In a preferred embodiment the movable upper housing part 6 ismade of a ceramic material having a density which issubstantially lower that the density of the liquid steel and this will also assist, in addition to the hydraulic action, lifting the movable upper housing part 6 towards against the closable outlet opening 4a of the ladle l.

The movable upper housing part 6 has, as an example, a shape,as seen in cross section, selected from the group consisting of a cylinder, oval, triangle and polygon.

The increase of lifting force of the upper housing part 6 hasimportance particularly at the end of the teeming operation incase the ladle is handled by a crane, for instance, since theweight of the ladle l is reduced at the end of the teemingoperation, and the inherent flexibility of the crane andpossible lifting equipment for lifting the ladle l will tosome extent raise the ladle l away from the upper housing part 6 of the liquid steel receiving housing A.

Figure 2 shows, and in enlarged scale in figure 2a, how theflow of liquid steel 2 leaving the end l7b of the distributorpipe l7 diverge (at 22) towards the inside of the jetconcentrating means 20. In said figures, a vacuum channel 2lis also shown enabling vacuum which reside where the flow ofliquid steel diverges, at 22, to also reduce the pressure inside the jet concentrating means 20.

In case the jet concentrating means 20 is arranged to extendfrom an upper end 24a of said mould 24 to close to a bottom(not shown) of said mould 24 it is of a meltable type, and incase an outlet end 20a of said jet concentrating means 20(figs. 3 and 3a) is positioned above a top of a finished ingot 23 in said mould 24 it is of a non-meltable type.

As the liquid steel fills the mould the jet concentrationmeans 20 is adapted, in case of a meltable jet concentratingmeans 20, to melt progressively at its end immersed into theliquid steel at the same rate as the level of the liquid steel raises in the mould 24, as explained above.

Preferably, the vacuum is applied to the system through thevacuum pipe 27 from the beginning of the ladle l being centrerelative to the movable upper housing part 6 until the top/surface of the liquid steel has frozen in the mould 24.

The teeming of liquid steel from the ladle l is stopped whenthe level of liquid steel reaches an upper level of the putty3. The purpose of the putty 3 is to reduce the risk of oxygenbeing sucked into the closable outlet opening 4a of the ladlel and thereby into the teemed liquid steel by formation of a vortex.

Each distributor pipe l7 is at its upstream end connected tothe distributor l4 and at its downstream end provided with theflow restriction means l8, preferably in the form of areduction of the diameter of the pipe. The purpose of the flowrestriction means l8 is to ensure that the flow of liquidsteel 2 is the same in all distributor pipes l7 so that all the moulds 24 will be filled evenly.

Figure lc shows a further embodiment of the inventive systembut without a vacuum valve arranged in the liquid steelreceiving housing A. This embodiment will function in the sameway as the embodiment first described, but vacuum to theliquid steel receiving housing A, the at least one distributorpipe l7 and the mould 24, etc. is only provide when theteeming is in operation and thus no vacuum in these parts after teeming to the ingot frozen.

It should be noted that the at least one distributor pipe l7is arranged horizontally or with a slope towards the mould 24so as to be free draining when teeming of liquid steel has stopped.

Claims

1. l. A system for fall teeming under vacuum of liquid steel (2) through a closable outlet opening (4a) in a bottom wall(la) of a movable ladle (l) into a liquid steel receivingapparatus (A) vacuum sealed and fluidly connected to saidclosable outlet opening (4a) and therefrom into adistributor (l4) arranged on a distributor plate (25), towhich distributor (l4) an upstream end (l7a) of at least onedistributor pipe (l7) is vacuum sealed and fluidlyconnected, an outlet end (l7b) of which is placed in a mould(24) sealingly arranged underneath said distributor plate(25) and arranged to be filled with liquid steel (2) andprovided with vacuum by a vacuum pipe (27), characterized inthat said liquid steel receiving apparatus (A) comprises ahousing (9) having a through channel (9a) and an upperhousing part (6) movably and sealingly arranged inside saidthrough channel (9a), and that said at least one distributorpipe (l7) is provided with a flow restriction means (l8)enabling an upper end (6a) of said movable upper housingpart (6) to be forced upwardly by a static pressure from theliquid steel filling said liquid steel receiving apparatus(A) and acting upon a lower end (6b) of said movable upperhousing part (6) whereby said upper end (6a) of said movableupper housing part (6) is adapted to exert a force on saidclosable outlet opening (4a) in said bottom wall (la) so asto provide a more powerful sealing between said upper end(6a) of said movable upper housing part (6) and said closable outlet opening (4a).

2. The system according to claim l, characterized in that avacuum valve (lO) is arranged at a bottom of said housing (9) and adapted to provide vacuum by said vacuum pipe (27) in at least said at least one distributor pipe (l7) and saidmould (24) until said liquid steel has reached apredetermined level in said housing (9) due to said flow restriction means (l8).

3. The system according claim 2, characterized in that saidflow restriction means (l8) has such dimension relative tothe dimension of said at least one distributor pipe (l7), inwhich it is provided, and relative to a flow of liquid steel(2) teemed from said ladle (l), that said liquid steelreceiving apparatus (A) and said at least one distributorpipe (l7) are totally filled with liquid steel (2) when said vacuum valve (lO) is open during teeming.

4. The system according to any of the preceding claims,characterized in that a jet concentrating means (20) isarranged at said outlet end (l7b) of said at least one distributor pipe (l7).

5. The system according to claim 4, characterized in thatsaid jet concentrating means (20) is either of a meltabletype wherein it extends from an upper end (24a) of saidmould (24) to close to a bottom of said mould (24) or is ofa non-meltable type wherein it is positioned so that anoutlet end (20a) of said jet concentrating means (20) ispositioned above a top of a finished ingot (23) in said mould (24).

6. The system according to claim 5, characterized in thatsaid jet concentrating means (20), in case it is of meltabletype, is made of a steel grade having a lower melting pointthat the melting point of said liquid steel (2) to beteemed, so that said jet concentrating means (20) meltsprogressively at its outlet end (20a) as a level of the liquid steel (2) rises in said at least one mould (24).

7. The system according to any one of the preceding claims,characterized in that said vacuum pipe (27) is arranged tosuck out gas(air) from said liquid steel receiving apparatus(A), said at least one distributor pipe (l7), and said mould (24) until a surface of an ingot (23) has frozen.

8. The system according to claim 2, characterized in that avacuum duct (ll) is provided parallel to the vacuum valve(lO) enabling vacuum to act on a space inside the liquidsteel receiving apparatus (A) even in case said vacuum valve (lO) is in its closed position.

9. The system according to any one of the preceding claims,characterized in that the ladle (l) has a bottom wall (la) in which a potty (3) is arranged. lO The system according to any one of claims 2 to 9,characterized in that a flotation body of the valve (lO) is provided with a cavity (lOb).