Continuous vacuum degassing and casting of steel

In a method for continuous vacuum processing and casting of molten steel and other metals, in which a molten metal column is maintained with its top surface under vacuum in a continuous post-treatment vessel located adjacent to a continually replenished molten metal bath, and said column is fed with metal from said bath by way of a withdrawal tube with the inlet end inserted below and withdrawing metal from beneath the surface of said bath and the outlet directing the metal into said column, with a lateral extension of the lower portion of said column forming a pouring pool confined within a tundish chamber equipped with at least one nozzle outlet for pouring of metal at a level below the surface level of said molten bath;

• the combination thereof with sealing of said pouring pool apart from outside atmosphere and maintaining this seal during operation, thus substantially preventing any contact of the molten metal with the atmosphere during passage from within said bath as the metal passes through said tube, column and pouring pool, at least until passage of molten metal through said nozzle outlet;
• and introducing the molten metal via said nozzle outlet directly into a continuous casting mold within which at least the outer surface of the metal solidifies and from which the metal exits at a rate governed by external adjustment of the withdrawal speed of the solidified casting.

In a method for continuous vacuum processing and casting of molten steel and other metals in which a molten metal column is maintained with its top surface under vacuum in a continuous post-treatment vessel located adjacent to a continually replenished molten metal bath, and said column is fed with metal from said bath by way of a withdrawal tube with the inlet end inserted below and withdrawing metal from beneath the surface of said bath and the outlet directing the metal into said column, with a lateral extension of the lower portion of said column forming a pouring pool confined wihtin a tundish chamber section equipped with at least one nozzle outlet for pouring of metal at a level below the surface level of said molten bath;

• the combination thereof with the additional steps preceding the above substantially steady-state conditions, to start initial flow, comprising:
• sealing of the cover of the tundish chamber against the outside atmosphere;
• closing said nozzle opening with the effect of substantially sealing said tundish and vacuum chamber when in the pre-operational nonfilled condition;
• evacuating said tundish and vacuum chamber to effect molten metal flow by movement from said bath through said tube into said degassing chamber and progressive filling of said chamber and tundish with molten metal up to said barometric height of said column;
• and removing the closure from said nozzle outlet to allow metal discharge to begin and thereby establish the conditions of continuous vacuum degassing and pouring.

In a method for continuous vacuum processing and casting of molten steel and other metals in which a molten metal column is maintained with its top surface under vacuum in a continuous post treatment vessel located adjacent to a continually replenished molten metal bath, and said column is fed with metal from said bath by way of a withdrawal tube with the inlet end inserted below and withdrawing metal from beneath the surface of said bath and the outlet directing the metal into said column, with a lateral extension of the lower portion of said column forming a pouring pool confined within a tundish chamber section equipped with at least one nozzle outlet for pouring of metal at a level below the surface level of said molten bath;

• the combination thereof with the additional steps preceding the above substantially steady-state conditions to start initial flow, comprising:
• sealing of the cover of the tundish chamber against the outside atmosphere;
• effecting closure and sealing of the metal passage through said withdrawal tube;
• closing said nozzle opening with the effect of substantially sealing said tundish and vacuum chamber when in the pre-operational non-filled condition;
• evacuating said tundish and vacuum chamber;
• opening of said metal passage closure through said wihtdrawal tube to effect molten metal flow by movement from said bath through said tube into said degassing chamber and progressive filling of said chamber and tundish with molten metal up to said barometric height of said column;
• and removing the closure from said nozzle outlet to allow metal discharge to begin and thereby establish the conditions of continuous vacuum degassing and pouring.

In an apparatus for continuous vacuum degassing and pouring of molten steel and other metals from a continually replenished molten metal bath, comprising a continuous post-treatment vessel stationed adjacent to said molten metal bath incorporating a vacuum degassing column section with an evacuated top space maintained over a columnar enclosure for molten metal extending upwards above the level of said molten metal bath and incorporating a metal withdrawal tube with the inlet inserted beneath the surface of said molten bath and the outlet connected into said degassing column section, the lower portion of which is in direct communication with a laterally extending pouring tundish section incorporating at least one pouring nozzle outlet situated below the surface level of said metal bath;

• the combination thereof with:
• an enclosed and sealed cover over said tundish section adapted to exclude the outside atmosphere and prevent communication between the interior of said tundish section and the outside atmosphere during evacuation of said post-treatment vessel;
• a tundish cover aperture with sealed opening and closure means in said cover above the surface level of said molten bath adapted to allow opening of said tundish to atmospheric pressure following filling of said post-treatment vessel with molten metal;
• a sealed opening and closure means for said withdrawal tube;
• and a separating barrier adapted to limit free movement of molten metal between said vacuum column section and said pouring tundish section, said barrier completely covering the tundish chamber entry cross section to a level extending essentially below the surface level of said molten metal bath;
• and sealed opening and closure means for said pouring nozzle outlet adapted to facilitate evacuation of said tundish chamber section when closed and flow of molten metal therethrough when opened.