Method for analyzing liquid metal and device for use in this method

Abstract

A method for analyzing the composition of a bath comprising liquid metal, in which a laser beam is directed onto a surface of the bath and in which at least part of the metal forms a sample which is analyzed. In the method, at least at the location where the laser beam meets the bath, impurities at the surface of the bath are removed by purging with a stream of a purge gas. A device for analyzing the composition of a bath comprising liquid metal.

1 . A method for analyzing the composition of a bath comprising liquid metal, in which a laser beam is directed onto a surface of the bath and in which at least part of the metal forms a sample which is analyzed, comprising, at least at the location where the laser beam meets the bath, removing impurities at the surface of the bath by purging with a stream of a purge gas.  
   
   
       2 . The method according to  claim 1 , wherein the velocity and direction of the stream of the purge gas are selected in such a manner that the surface of the bath adjacent to the location where the laser beam meets it has a convex meniscus.  
   
   
       3 . The method according to  claim 1 , wherein a submerged pipe system provided with a top side, an underside and a casing is at least partially placed in the bath, and the stream of the purge gas is fed into the submerged pipe system above the bath and is directed onto the bath at least at the location where the laser beam meets the bath.  
   
   
       4 . The method according to  claim 3 , wherein purge gas in the submerged pipe system is discharged from the submerged pipe system below the surface of the bath.  
   
   
       5 . The method according to  claim 1 , wherein the liquid metal is a liquid aluminium alloy.  
   
   
       6 . A device for analyzing the composition of a bath comprising liquid metal, comprising: 
 a submerged pipe system provided with a top side, an underside and a casing having an inner wall and an outer wall,    a source for generating a beam of laser light, and    a gas supply tube for feeding purge gas into the submerged pipe system,    the gas supply tube for feeding the purge gas in the direction of the bath, and to run inside the casing, in such a manner that during use the bath inside the casing forms a convex meniscus along which purge gas flows.    
   
   
       7 . The device according to  claim 6 , wherein the gas supply tube has a reduced bore size for at least locally increasing the flow velocity of the purge gas.  
   
   
       8 . The device according to  claim 6 , wherein the casing of the submerged pipe system is provided, in the part which in use extends into the bath, with outlet openings and/or with slots arranged in the underside of the casing.  
   
   
       9 . The device according to  claim 8 , wherein the slots and/or openings run with an increasing cross section from the inside of the casing towards the outside thereof.  
   
   
       9 . The device according to  claim 6 , wherein at least part of the inner wall of the casing of the submerged pipe system is made from a material which is not wettable by the liquid metal.  
   
   
       10 . The device according to  claim 6 , further comprising: 
 the liquid metal bath;    wherein the casing has a downstream end submerged into the bath;    a portion of the bath being within the downstream end of the casing and having a convex meniscus;    the gas supply tube has a downstream end concentric with the casing and the gas supply tube passage is located within the casing for discharging purge gas into the casing onto the portion of the bath within the downstream end of the casing;    the source for generating a beam of laser light and for discharging the beam through the supply tube passage onto the portion of the bath being within the downstream end of the casing;    a downstream end of the gas supply tube passage having the bore size for at least locally providing the purge gas in the direction of the bath with sufficient flow velocity in the casing to form the convex meniscus along which purge gas flows on the bath inside the casing.