WO1986004980A1

WO1986004980A1 - Apparatus and process for transferring a predetermined amount of liquid metal from a vessel containing a molten metal bath into a receiving container

Info

Publication number: WO1986004980A1
Application number: PCT/EP1986/000069
Authority: WO
Inventors: Ralph Weber
Original assignee: Kortec Ag
Priority date: 1985-02-20
Filing date: 1986-02-13
Publication date: 1986-08-28
Also published as: EP0211952A1; HUT42844A; IN164059B; DE8504755U1; TR23406A; IN164135B; HU196497B; BR8605562A

Abstract

For the purposes of transferring a predetermined amount of liquid metal from a vessel (1) containing a molten metal bath (2) into a receiving container (3), there is provided a discharge flow pipe (4) which has a refractory lining and which is in the form of an inverted U or V with two downwardly pointing limbs (5, 6) of which the first has an intake opening and the second has an outlet opening for the liquid metal, which outlet opening can be gas-tightly closed by a closure means. Provided in the upper region of the discharge flow pipe (4) is a pipe connection (14) which has a refractory lining and which can be communicated with a vacuum means (19, 20). The discharge flow pipe is dipped with its first limb (5) into the molten metal bath (2) and the liquid metal is removed on the basis of the principle of a liquid siphon.

Description

Apparatus and process for transferring a predetermined amount- of liquid metal frαn a vessel containing a molten metal bath into a receiving container

Description

Technical Field The invention relates to an apparatus for transferring a predetermined amount of liquid metal frαn a vessel containing a molten metal bath, in particular a furnace vessel, into a receiving container, by means of a discharge flow pipe having a refractory lining. The invention further relates to a process using such an apparatus.

Background Art

In a known apparatus of the above-indicated kind (German laid- open application (DE-OS) No 3 241 987), the floor of a portion of an electric arc furnace, which projects out in a bay window-like configuration, is provided with a tapping hole which can be closed frαn beneath by means of a pivotable plate and which is lined with a refractory tube. In order to protect the plate frαn being attacked by the molten metal, a filling mass of refractory material is provided in the tapping hole. For the tapping operation, the closure plate is pivoted to the side thereby opening the tapping hole. The jet of metal passes over a short distance into a ladle which is beneath the tapping hole. After the desired amount of liquid metal has been drawn off, the vessel of the arc furnace is tilted and in that way the tapping operation is terminated, with the slag that floats on the molten metal bath being retained in the furnace vessel.

That procedure for transferring a predetermined amount of liquid metal frαn a vessel into a receiving container presupposes equipment for tipping the furnace vessel, which is relatively expensive particularly when dealing with vessels of larger sizes. In addition the tipping operation takes a number of minutes, having regard to the large masses to be moved.

Disclosure of JCnvaitiαi

The object of the present invention, in an apparatus of the kind set forth in the opening part of this specification, is to permit transfer of a predetermined amount of the molten metal into a receiving container without the vessel having to be tipped. The invention seeks to make it possible in that connection to retain the slag that floats on the molten metal bath, in the vessel. The invention further¹ seeks to make it possible to protect the flow of metal, as it passes into the receiving container, frαn being attacked by the free atmosphere. Finally the invention seeks to provide that discharge of the liquid metal from the vessel can be immediately interrupted if required.

That object is attained by the features set forth in claim 1.^*

Advantageous embodiments of the invention and a process using the apparatus according to the invention are set forth in the other claims.

The teaching in accordance with this invention makes use of the principle of a liquid siphon, that is to say, the pressure difference between the intake and the outlet of a conduit. In that connection the configuration of the apparatus takes account of the particular factors which are involved in transferring liquid metal frαn a vessel into a receiving container. In that connection measures are provided such that the flow of metal can be securely and safely started and can be instantly interrupted, and the slag that floats on the molten metal bath in the vessel is retained. In that connection the flow of metal is guided within a pipe almost over the entire distance between the vessel and the receiving container so that the metal is protected frαn attack by the free atmosphere. Oxygen is virtually completely prevented frαn having access to the metal by means of a protective curtain of inert gas in the region of the point at which the flow of metal issues frαn the pipe. Brief Description of Drawings

The invention will now be described in greater detail by means of two embodiments with reference to three Figures of drawings in which: Figure 1 is a basic diagrammatic view of an enbodiment of the invention,

Figure 2 is a view in section of a portion of Figure 1, and

Figure 3 is a basic diagrammatic view of a second embodiment of the invention. Modes for Carrying Out the Invention

Figures 1 axfi 2 show an apparatus with a vessel 1 which contains a molten metal bath 2. The vessel 1 may be an arc furnace, in particular the portion of an arc furnace which projects in a bay window-like configuration, a heating or soaking furnace, a ladle or another vessel which contains, liquid metal, in particular liquid steel. In order for the liquid metal which is at a high temperature to be transferred in a predetermined amount into a receiving container 3 such as a ladle truck or another container, the arrangement has a discharge flow pipe 4 in the form of an inverted U having two downwardly pointing limbs 5 and 6. Of those limbs, the first limb 5 has an intake opening 7 while the second limb 6 has an outlet opening 8 which is lower than the intake opening 7. In the condition shown in Figure 2, the outlet opening 8 of the discharge flow pipe 4 is gas-tightly closed by a closure means 9 and in addition the intake opening 7 of the discharge flow pipe 4 is closed off by a plate member 10 which cc prises a material whose melting point is below the temperature of the molten metal bath 2. The plate member 10 serves to ensure,, when the first limb 5 of the discharge flow pipe 4 dips into the vessel 1, that slag floating on the molten metal bath 2 cannot penetrate into the discharge flow pipe, the layer of slag being indicated at 11. For that purpose it is advantageous for the plate member 10 to be of a wedge-like or frustoconical configuration so that the end of the pipe which is closed by the plate member 10 can pass through the layer of slag, without entraining slag therewith.

The discharge flow pipe 4 includes a steel casing 12 and a refractory lining 13. In the illustrated embodiment, it is made up of a plurality of pipe portions which are gas-tightly joined together. The steel casings of the pipe portions may be for example welded together or they may be connected by sealed annular flanges. In addition, in the region which is exposed to the slag and the liquid metal, the first limb 5 has a refractory cladding 13a.

A pipe connection 14 which has a refractory lining is provided in the upper region of the discharge flow pipe 4, in the illustrated embodiment in the region joining the limbs 5 and 6 thereof. The connection 14 is connected to a flexible gas line 15 which can be selectively connected to a vacuum means 17 by way of a first valve 16 or communicated by way of a second valve 18 to the free atmosphere. The vacuum means includes a vacuum pump 19, a vacuum storage means 20 and a pressure measuring device 30. The capacity of the vacuum storage means 20 approximately corresponds to thirty times the capacity of the discharge flow pipe including the conduits as far as the valves 16 and 18. Disposed upstream of the vacuum storage means is a gas cooler 34 whose function is to remove dust frατi and to cool the gas which is sucked out by the vacuum means, from the discharge flow pipe 4. It includes a chamber 35 with a coolin coil 36. When the hot gas which has been sucked out by the vacuum means passes into the chamber, the gas can expand because of the abrupt substantial increase in the flow cross-section. The gas drops in temperature when that occurs and in heat exchange relationshi with the cooling coil 36. In addition, the reduction in the flow • speed causes the dust which is entrained with the flow of gas to be separated out. As shown in Figure 1, the receiving container 3 is disposed on a weighing means 21 for measuring the amount of metal which is introduced into the receiving container 3. The closure means 9 for the outlet opening 8 of the discharge flow pipe 4 includes a closure plate 23 which is provided with an annular seal 22 and which is movable from a closure position in which it bears against the edge of the outlet opening 8, as shown in Figure 2, into an open position (not shown) in which the outlet opening 8 is open. The closing and opening movements are produced by a drive means 24 which is shown in diagrammatic form. In order to ensure that the closure means 9 closes in a vacuum-tight manner, the steel casing 12 is provided at the discharge end of the discharge flow pipe 4 with an annular flange 31 which, within the surface that presses against the annular seal 22, has an annular groove 32 which cαnmunicates with at least one small pipe 33. The annular groove may be connected by way of the pipe 33 and by a conduit (not shown) to a vacuum source whereby, in the closed position of the closure plate 23, that is to say, when the annular seal 22 is pressed against the annular flange 31, it is possible to • provide a vacuum-tight connection between the annular flange 31 and the annular seal 22 which is fixed on the closure plate 23. If such a vacuum closure arrangement is not used, the arrangement does not always guarantee that the annular seal 22 is pressed vacuum- tightly against the annular flange 31.

Granular refractory material 25 is disposed above the closure plate, to a height of about 300 mm. The material 25 serves to protect the closure plate 23 frαn direct contact with the liquid metal. For the purposes of introducing a predetermined amount of that granular refractory material, a gas-tightly closable filling connection 26 is provided at the upper end of the second limb 6. Connected to the connection 26 by way of a valve 27 is a container (not shown) for granular refractory material, having a metering means, The connection 26, like the connection 14, must be provided with a refractory lining to a height that the liquid metal can reach in the suction operation performed by the vacuum means. The flow cross-section of the discharge flow pipe 4 is reduced in the fashion of a venturi tube at a location 28 just upstream of the outlet opening 8 in order to increase the flow speed at that location and to ensure that air cannot penetrate into the discharge flow pipe 4 when the closure plate 22is removed while the liquid metal is flowing out. In addition, provided at the lower end of the second limb 6 of the discharge flow pipe 4, on the outside thereof, is an annular pipe 29 having downwardly facing openings which are distributed around the periphery thereof and which can provide a protective gas enclosure around the jet issuing frαn the discharge flow pipe in order to protect it frαn an oxidising effect frαn the ambient air.

The mode of operation of the above-described apparatus will now be described. Prior to the operation of tapping the vessel containing the molten metal bath or prior to transferring a predetermined amount of liquid metal from the vessel 1 into the receiving container 3 which is disposed on the weighing device 21, the valves 16, 18 and 27 are closed and a vacuum of about 98% of absolute vacuum is formed in the vacuum storage means 20 by means of the vacuum pump 19.

That vacuum is maintained until the discharge flow pipe 4 is used.

In order to ensure that the refractory lining 13 of the discharge flow pipe is not subjected to a thermal shock when it is put into use and in order to ensure that the metal does not freeze on to the discharge flow pipe while it is being conveyed therethrough, the refractory lining is preheated by means of gas, oil or electrical power.

Directly prior to the discharge flow pipe 4 being brought into use, the closure plate 23 of the closure means 9 is moved into the closure position by actuation of the drive 24 and the annular groove 32 is connected to the vacuum source which is provided for that purpose, for example the vacuum storage means 20.

A predetermined amount of granular refractory material 25 is introduced by opening the valve 27. Thereafter the valve 27 is closed again and the plate member 10 is moved into position at the intake opening 7 of the discharge flow pipe 4. After those preparatory steps, the discharge flow pipe 4 is dipped with its first limb to the desired depth into the molten metal bath 2 in the vessel 1. That position is shown in Figure 2. When it passes through the layer of slag 11, the plate member 10 ensures that slag cannot pass into the interior of the discharge flow pipe 4. After a few seconds, the plate member 10 which preferably comprises the same material as the molten metal in order to prevent contamination melts and the liquid metal passes upwardly into the discharge flow pipe, to approximately the level of the surface of the metal bath in the vessel 1. When the time has come for tapping the vessel 1 or for transferring the liquid metal to the receiving container 3, the valve 16 is opened, with the valves 18 and 27 still being closed, whereby, as the system is gas-tightly closed off and atmospheric pressure acts on the molten metal bath 2 in the vessel 1, the liquid metal is sucked in by virtue of the vacuum through the gas line 15 and, when that occurs, the entire discharge flew pipe is filled as far as the granular refractory material as well as a part of the connection 14 and a part of the connection 26. That suction operation occurs suddenly by virtue of the vacuum storage means 20. In that stage of operation, the vacuum will drop frαn about 98% to about 95%. The vacuum pump 19 continues to be operated during the transfer operation in order to remove any gases which may be developed and which may accumulate in the system. In that operation, the gases which are sucked away are cooled down and dust is removed therefrom, in the gas cooler 34.

When the discharge flow pipe 4 is filled with liquid metal, the connection of the annular groove 32 to the vacuum source is interrupted, the annular groove is exposed again to atmospheric pressure and the drive means 24 is operated to move the closure plate 23 into the position in which it opens the outlet opening 8. The granular refractory material 25 falls out or is urged outwardly, and a jet of liquid metal pours out of the outlet opening 8.

A curtain of protective gas can be formed around the jet of liquid metal and above the surface of the bath in the receiving vessel 3 by feeding inert gas to the annular conduit 29. The amount of liquid metal which is introduced into the receiving container 3 is measured by the weighing means 21. When the desired amount of metal has been transferred into the container 3 or if the discharge flow of liquid metal frαn the vessel 1 is to be interrupted for other reasons, then the valve 16 is closed and directly thereafter the valve 18 is opened. The valve 18 breaks the vacuum and instantly stops the flow through the discharge flow pipe 4.

The discharge flow pipe 4 is now removed again frαn the vessel 1 and frαn the receiving container 3, checked and repaired as far as may be necessary in order to make it ready for the next tapping operation. Figure 3 diagrarraratically shows the operation of tapping frαn a melting vessel such as for example an arc furnace la. Water-cooled elements 38 which form the upper vessel are fitted in position on a hearth 37 of the vessel la. At the top the vessel la is closed by a cover 39. The water-cooled element 38 which is shown on the right in the sectional view in Figure 3 has a closable opening 40 through which the first limb 5 of a discharge flow pipe 4a can be inserted, the discharge flow pipe being in the form of an inverted V. In other respects the discharge flow pipe 4a is of the same construction as the discharge flow pipe 4 in the first embodiment. For the purposes of tapping the vessel la, the limb 5, as shown in Figure 3, is inserted into the vessel la through the opening 40 until the intake opening 7 of the discharge flew pipe dips into the molten metal bath 2 and then a predetermined amount of liquid metal is transferred frαn the vessel la into the receiving container 3 in the same manner as in the case of the first embodiment.

Claims

CLAIMS__

1. Apparatus for transferring a predetermined amount of liquid metal frαn a vessel (1) αontaining a molten metal bath (2) , in particular a furnace vessel, into a receiving container (3), by means of a discharge flow pipe (4) having a refractory lining, characterised in that the discharge flow pipe (4) is in the form of an inverted U or V having two downwardly pointing limbs (5, 6) , of which the first limb (5) has an intake opening (7) and the second limb (6) has an outlet opening (8) for the liquid metal, which outlet opening can be gas-tightly closed by a closure means (9), further that provided in the upper region of the discharge flow pipe (4) is a pipe connection (14) which has a refractory lining and which can be ccmmunicated with a vacuum means (19, 20) , and the discharge flow pipe can be dipped with the first limb (5) into the molten metal bath (2) .

2. Apparatus according to claim 1 characterised in that a gas cooler (34) is arranged between the pipe connection (14) with the refractory lining, and the vacuum means (19, 20).

3. Apparatus according to claim 1 or claim 2 characterised in that the pipe connection (14) which has a refractory lining can be selectively connected to the vacuum means (19, 20) by way of a first valve (16) or cαnmunicated with the free atmosphere by way of a second valve (18).

4. Apparatus according to one of claims 1 to 3 characterised in that the vacuum means includes a vacuum pump (19) and a vacuum storage means (20).

5. Apparatus according to one of claims 1 to 4 characterised in that the first limb (5) has a casing (13a) of refractory material, in the region which dips into the molten metal bath (2) .

6. Apparatus according to one of claims 1 to 5 characterised in that the intake opening (7) of the discharge flew pipe (4), before dipping into the molten metal bath (2) , is closed by a plate member (10) cαπprising a material whose melting point is below the temperature of the molten metal bath.

7. Apparatus according to one of claims 1 to 6 characterised in that the closure means (9) for the outlet opening (8) of the discharge flow pipe (4) includes a closure plate (23) which is provided with a seal (22) and which is movable frαn a closure position of bearing against the edge of the outlet opening (8) into an open position in which the outlet opening (8) is open.

8. Apparatus according to claim 7 characterised in that provided at the discharge end of the discharge flow pipe (4) is an annular flange (31) against which the seal (22) fixed an the closure plate

(23) is pressed in the closure position of the closure plate {23) , and that the annular flange (31), in the region in which it presses against the seal (22), has an annular groove (32) which can be connected to a vacuum source (20) .

9. Apparatus according to claim 7 or claim 8 characterised in that a filling connection (26) for granular refractory material (25), which connection can be gas-tightly closed, is provided at the upper end of the second limb (6) .

10. Apparatus according to claim 9 characterised in that a container having a metering means is connected to the filling connection (26) by way of a valve (27).

11. Apparatus according to one of claims 1 to 10 characterised in that the flow cross-section of the discharge flow pipe (4) is reduced just before the outlet opening (8).

12. Apparatus according to one of claims 1 to 11 characterised in that the pipe connection (14) with the refractory lining extends upwardly to beyond the maximum suction height of the molten metal.

13. A process for transferring a predetermined amount of liquid metal frαn a vessel (1) conta-Lning a molten metal bath, in particular a furnace vessel, into a receiving container, by means of an apparatus according to one of claims 3 to 12 characterised in that the outlet opening (8) of the discharge flow pipe (4) is gas- tightly closed by actuation of the closure means (9) and a metered amount of granular refractory material is introduced into the space above the closed outlet opening (8), that, with the first and second valves (16 and 18 respectively) closed and with the filling connection for granular refractory material closed, the first limb (5) is lowered into the molten metal bath (2) , the first valve (16) is opened and the outlet opening (8) is opened by actuation of the closure means (9) .

14. A process according to claim 13 characterised in that the refractory lining (13) of the discharge flow pipe (4) is heated prior to closure of the outlet opening (8) .

15. A process according to claim 13 or claim 14 characterised in that, to terminate the removal of the liquid metal frαn the vessel (1), the first valve (16) is closed and the second valve (18) is opened.

16. A process according to one of claims 13 to 15 characterised i that the intake opening (7) of the discharge flow pipe (4) is closed by a plate member (10) prior to being dipped into the molten metal bath (2).