Refractory plug or brick for injecting gas into molten metal

Abstract

The invention concerns a plug or brick ( 1 ) for injecting gas into molten metal through a molten metal-contacting surface ( 11 ) comprising i) a porous refractory body ( 2 ) substantially surrounded by a substantially non-porous body ( 9 ) except at the molten metal-containing surface ( 11 ); and ii) gas conducting means ( 3,5 ) for conveying the gas from a gas source to the porous body ( 2 ). The plug or brick is characterized in that the non-porous body ( 11 ) is made of refractory material and in that the porous and non-porous bodies ( 2,11 ) have been co-pressed. This plug or brick can be used to inject efficiently and reliably small bubbles into a molten metal bath.

1 . Solid porous refractory plug or brick (1) for vessel limiting for injecting gas into molten metal through a molten metal-contacting surface ( 11 ) comprising 
 i) a porous refractory body ( 2 ) substantially encased in a substantially non-porous body ( 9 ) except at the molten metal-contacting surface ( 11 ); and    ii) gas conducting means ( 3 , 5 ) for converging the gas from a gas source to the porous body ( 2 ),    characterized in that the non-porous body ( 11 ) is made of refractory material and in that the porous and non-porous bodies ( 2 , 11 ) have been co-pressed.    
     
     
         2 . Plug or brick according to  claim 1  characterized in that the gas conducting means ( 3 , 5 ) comprises a plenum chamber ( 3 ).  
     
     
         3 . Plug or brick according to  claim 1  or  2 , characterized in that the porous and non-porous bodies are constituted of refractory materials with similar coefficients of thermal expansion.  
     
     
         4 . Plug or brick according to any one of  claims 1  to  3 , characterized in that the porous and non-porous bodies are constituted of more than 50 weight % of magnesia, magnesia spinel, alumina or alumina spinel, preferably more than 80 weight %.  
     
     
         5 . Plug or brick according to any one of  claims 1  to  4 , characterized in that the non-porous body comprises more than 50 weight %, preferably more than 80 weight %, of magnesia, magnesia spinel, alumina or alumina spinel.  
     
     
         6 . Plug or brick according to any one of  claims 1  to  5 , characterized in that the porous body ( 2 ) has a tapered section ( 7 ) towards its molten metal-contacting surface.  
     
     
         7 . Process for the manufacture of a solid refractory porous plug or brick for vessel lining for injecting gas into molten metal through a molten metal-contacting surface comprising the steps of: 
 1) introducing into a mould of appropriate amounts of the refractory materials constituting the porous and non-porous bodies while respecting the desired limits for these bodies;    2) simultaneous co-pressing of both refractory materials;    3) providing gas conducting means;    4) heat treating the co-pressed materials.    
     
     
         8 . Process according to  claim 7 , wherein the gas conducting means comprises a plenum chamber.  
     
     
         9 . Process according to  claim 8 , characterized in that the step (3) of providing the gas conducting means comprises a step of introducing a strip of consumable materials into the mould at the junction between the porous and non-porous bodies.  
     
     
         10 . Process according to  claim 9 , characterized in that the consumable material comprises wax.