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1. WO1991015320 - PROCEDE ET APPAREIL DE REGULATION DE L'ECOULEMENT DU METAL FONDU

Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

[ EN ]

CLAIMS

1. A method of controlling the flow of molten metal from a holding vessel such as a tundish through a discharge orifice into a receptacle such as a mould; the method comprising
(i) providing within the holding vessel a flow control chamber comprising a down-flow chamber separate from but in fluid communication with the interior of the holding vessel, the down-flow chamber having an outlet at its lower end, said outlet leading to or forming part of the discharge orifice, and an opening towards or at its upper end;
(ii) creating a gas pressure within the flow control chamber sufficient to allow molten metal from the holding vessel interior to pass through the opening to establish in the lower end of the down-flow
chamber a column of the molten metal with a volume of gas occupying the upper end of the flow control chamber and serving to separate the column of molten metal from the opening, whereby an equilibrium is established between molten metal passing through the opening and molten metal passing out through the discharge orifice such that the height of the column of molten metal in the down-flow chamber remains substantially constant; and
(iii) (a) reducing the said volume of gas, thereby to increase the height of the column of molten metal and thus the flow rate through the discharge orifice, or (b) increasing the said volume of gas, thereby to reduce the height of the said column and thus the said flow rate.

2. A method according to claim 1 wherein there is provided an up-flow chamber, the up-flow and down-flow chambers being linked for molten metal flow therebetween by the opening towards or at the upper end of the down-flow chamber, wherein the up-flow chamber has an inlet at a point below the said opening through which molten metal from the holding vessel may pass.
3. A method according to claim 1 or claim 2 wherein the volume of gas in the upper end of the chamber is reduced by applying thereto a pulse or pulses of negative pressure; and/or the said volume is increased by applying thereto a pulse or pulses of relatively positive pressure.
4. A method of controlling the flow of molten metal from a holding vessel such as a tundish, into a receptacle such as a mould, the method
comprising :
(i) providing a refractory body, the hollow interior of which defines mutually laterally disposed first and second melt-receiving flow control chambers, which chambers are linked for molten metal flow
therebetween by an opening located at a point remote from the lower end of the chambers; the first chamber constituting an up-flow chamber and having an inlet at a point below the opening linking the first and second chambers; the second chamber constituting a down-flow chamber and having an outlet at or near its lower end through which molten metal may be dispensed, the refractory body being located within the melt-containing vessel such that said outlet is secured against a discharge orifice of the vessel; the
refractory body having a gas port or ports opening into said hollow interior at a point above the opening linking the first and second chambers; the gas port or ports being connected to means for selectively venting to atmosphere and lowering and raising the pressure within the chambers, for example by supplying pulses of relatively positive or negative pressure to the hollow interior;
(ii) allowing molten metal from within the holding vessel to pass through the inlet of the up-flow chamber to ascend said up-flow chamber, and creating a system pressure within the hollow interior of the refractory body at which molten metal can flow through the opening between the first and second chambers to establish a column of molten metal in the second chamber ;
(iii) allowing an equilibrium pressure to develop under which flow of molten metal through the said outlet and thence through the said discharge orifice is balanced by flow through said linking opening between the two chambers to maintain the said column of metal at a required height; and
(iv) temporarily displacing the pressure from its equilibrium value by exposing the system (e.g. by applying a pulse or pulses of negative or positive pressure) to a source of negative or positive pressure in order to effect stepwise reduction or increase of the gas volume within the chamber and increase or decrease respectively the column height in the down-flow chamber thereby to increase or decrease
respectively the flow rate through the discharge chamber.
5. A method according to any one of claims 2 to 4 wherein the flow of molten metal into the
receptacle is initiated by reducing the pressure in the chambers (for example by means of a series of timed pulses) to a level whereat liquid metal passes through the opening from the up-flow chamber to the down-flow chamber to provide a molten metal column of a desired height within the down-flow chamber and, where necessary, removing any closure means closing the discharge orifice, to permit molten metal flow
therethrough.
6. A method of controlling the pouring of molten metal from a holding vessel into a receptacle, which method comprises steps (i) to (iv) as defined in claim 4, and, when it is required to drain the holding vessel ;
(v) allowing the molten metal level in the said vessel to fall; and
(iv) incrementally reducing the system pressure to increase the height of the column of molten metal in the down-flow chamber to a level approximately to the height of the opening linking the up-flow and down-flow chambers.
7. A method according to any one of claims 2 to 6 in which there is provided a purge cycle whereby during or following initial filling of the holding vessel with molten metal, the pressure within the up-flow and down-flow chambers is reduced to allow the molten metal to rise to a level in the up-flow chamber below the opening between the two chambers and is then increased to expel the molten metal from the up-flow chamber through the inlet thereof.
8. A method of controlling the pouring of molten metal from a melt-containing vessel as defined in any one of claims 1 to 7; which process additionally comprises the steps:
(a) prior to allowing establishment of a column of molten metal in the down-flow chamber, closing the discharge orifice with a removable closure means to enable the down-flow chamber to be
pressurised ;
(b) creating a positive pressure within the chamber sufficient to prevent molten metal from
entering the down-flow chambers; and (c) monitoring the pressure at which bubbles of gas escape from the inlet and computing therefrom the depth of molten metal in the container.
9. A method according to any one of claims 2 to 8 wherein the up-flow and down-flow chambers are disposed side by side and share a common wall.
10. A method according to any one of claims 2 to 9 wherein the opening linking the up-flow and down-flow chambers takes the form of a third chamber
disposed above the up-flow and down-flow chambers and, for example, the gas port or ports is or are located at or near an upper end of the third chamber.
11. A method according to claim 10 wherein the height of the third chamber is less than half the height of the second chambers, for example is
approximately one third of the height of the second chamber .
12. A method according to any one of claims 4 to 10 wherein the refractory body is a column in the form of a tube, the lower part of the tube being divided by a central weir into two separate galleries which constitute the first and second chambers.
13. A method according to any one of claims 2 to 11 wherein there is provided a single gas port which is connected to means for selectively venting the chambers to atmosphere and adding gas to, or
withdrawing gas from the chambers as required.
14. A flow control system comprising a holding vessel for molten metal, equipped with a flow-control chamber and being suitable for use in the method defined in any one of the preceding claims, the flow-control chamber for example being connected to a pneumatic controller capable of applying pulses of positive and negative pressure to the flow control chamber.
15. A flow control system according to claim 14 wherein the receptacle (e.g. a mould) is provided with flow-rate sensing means (e.g. an automatic meniscus level sensing means in a continuous caster) and the sensing means is connected in a closed control loop to the pneumatic controller, to enable the
pneumatic controller to vary the flow rate to the receptacle in response to a signal from the sensing means .
16. A flow control system according to claim 14 or claim 15 wherein there is associated with the holding vessel, a molten-metal feeder vessel (such as a ladle) for supplying molten metal to the holding vessel, the feeder vessel having flow rate control means (such as a sliding gate valve) for controlling the supply of molten metal to the holding vessel; the flow control system including a closed control loop between the flow rate control means and a pneumatic controller whereby the rate of supply of molten metal to the holding vessel can be varied in response to a signal from the pneumatic controller.
17. A flow control device suitable for use in the method of any one of the preceding method claims and comprising a refractory body as defined in any one of claims 4, 9, 10, 11 and 12, wherein the gas port or ports is or are provided with means (e.g. a threaded connection) for removably connecting thereto, via a pipe or pipes as appropriate, a pneumatic controller.
18. A flow control device suitable for use in the method of any one of the preceding method claims and comprising a refractory body as defined in any one of claims 4, 5, 9, 10, 11 and 12, wherein the gas port or ports above the opening linking the up-flow and down-flow chambers is or are provided with means for connecting thereto, via a pipe or pipes as appropriate, a pneumatic controller, and wherein the said gas port or ports represent the only means for controllably introducing gas in the refractory body.
19. A flow control column suitable for use in the method of any one of the preceding method claims, the column comprising a generally tubular hollow refractory body, the lower end of the interior of which is divided by a weir into up-flow and down-flow chambers, the down-flow chamber having an outlet at or near its lower end through which molten metal may be dispensed and the up-flow chamber having an inlet through which molten metal from a molten metal
reservoir may pass, the inlet being located below the level of the top of the weir; wherein the upper end of the interior of the refractory body has a gas port or ports opening into the interior at a point above the level of the top of the weir, the said gas port or ports constituting the sole means of introducing gas into the refractory body.
20. A method of determining the depth of molten metal in a holding vessel such as a tundish, which method comprises:
(a) providing within the holding vessel a chamber separate from but in fluid communication with the interior of the holding vessel, the chamber having at a position towards the bottom of the holding vessel an inlet through which molten metal may pass, said inlet being disposed such that gas within the chamber cannot escape through the inlet until a gas pressure is reached within the chamber which exceeds a metallostatic pressure of the molten metal in the holding vessel;
(b) providing a pressure of gas within the chamber sufficient to prevent molten metal from
entering the said inlet;
(c) providing an excess pressure of gas within the chamber and monitoring the gas pressure at which a bubble of gas is first caused to pass out of the inlet into the molten metal; and (d) relating the excess pressure of gas to the depth of molten metal in the vessel.
21. A method of controlling the flow of molten metal from a holding vessel such as a tundish into a receptacle such as a mould, the method being substantially as described herein with reference to the accompanying drawings.
22. A molten-metal flow control system substantially as described herein with reference to the accompanying drawings.
23. A flow control device substantially as described herein with reference to the accompanying drawings .
24. A flow control column substantially as described herein with reference to the accompanying drawings .