Lead retaining purge plug

Abstract

A purge plug containing a refractory material is configured to be inserted in the bottom of a ladle for introducing purging gas through a heat of molten metal in the ladle. The purge plug houses a retention chamber for holding the lead content of lead-containing molten steel alloys that leaches into, or infiltrates into, the purge plug. The purging gas supply tube is provided with a portion that protrudes into the retention chamber, thereby preventing the lead content of lead-containing molten steel alloys from entering and blocking the purging gas supply tube.

We claim: 
     
         1 . A purge plug, comprising:
 a refractory body having a feed end, a delivery end, an exterior and a longitudinal axis,   at least one gas delivery structure disposed in fluid communication with the feed end and the delivery end,   a retention chamber in fluid communication with the gas delivery structure and located at the feed end of the refractory body, and   a gas supply tube in fluid communication with the retention chamber and having a gas supply tube protrusion protruding into the retention chamber.   
     
     
         2 . The purge plug of  claim 1 , wherein the gas supply tube protrusion has an axis, and the axis of the gas supply tube protrusion is parallel to the longitudinal axis of the refractory body. 
     
     
         3 . The purge plug of  claim 2 , wherein the gas supply tube protrusion has an axis, and the axis of the gas supply tube protrusion is coaxial to the longitudinal axis of the refractory body. 
     
     
         4 . The purge plug of  claim 1 , wherein the gas supply tube protrusion terminates in a structure selected from the group consisting of a bend, a crimp, a nozzle and a ported cap. 
     
     
         5 . The purge plug of  claim 4 , wherein the gas supply tube protrusion terminates in a ported cap, and wherein the planes of the ports of the ported cap are not orthogonal to the longitudinal axis of the refractory body. 
     
     
         6 . The purge plug of  claim 1 , wherein the gas delivery structures are selected from the group consisting of slots, tubes of porous material, channels, voids formed in castable material, materials containing unidirectional gas passages parallel to the longitudinal axis of the refractory body and formed in pressed and fired plates, and combinations of these structures. 
     
     
         7 . The purge plug of  claim 1 , further comprising a metal housing at least partially enclosing the refractory body exterior. 
     
     
         8 . The purge plug of  claim 1 , further comprising a feed end cap, disposed on the refractory body feed end so as to define the retention chamber between the refractory body and the feed end cap, wherein the feed end cap accommodates the gas supply tube. 
     
     
         9 . The purge plug of  claim 1 , wherein the extent of the protrusion of the gas supply tube into the retention chamber is at least 5 millimeters. 
     
     
         10 . The purge plug of  claim 1 , wherein the extent of the protrusion of the gas supply tube into the retention chamber is at least 10 millimeters. 
     
     
         11 . The purge plug of  claim 1 , wherein the extent of the protrusion of the gas supply tube into the retention chamber is at least 15 millimeters. 
     
     
         12 . The purge plug of  claim 1 , wherein the extent of the protrusion of the gas supply tube into the retention chamber is at least 20 millimeters. 
     
     
         13 . The purge plug of  claim 1 , wherein the gas supply tube has a termination point within the retention chamber, and wherein the ratio of the volume of the retention chamber below the termination point to the volume of the retention chamber above the termination point is at least 1:1. 
     
     
         14 . The purge plug of  claim 1 , wherein the gas supply tube has a termination point within the retention chamber, and wherein the ratio of the volume of the retention chamber below the termination point to the volume of the retention chamber above the termination point is at least 2:1. 
     
     
         15 . The purge plug of  claim 1 , wherein the gas supply tube has a termination point within the retention chamber, and wherein the ratio of the volume of the retention chamber below the termination point to the volume of the retention chamber above the termination point is at least 3:1. 
     
     
         16 . The purge plug of  claim 1 , wherein the gas supply tube has a termination point within the retention chamber, and wherein the ratio of the volume of the retention chamber below the termination point to the volume of the retention chamber above the termination point is at least 4:1. 
     
     
         17 . The purge plug of  claim 1 ,
 wherein the retention chamber comprises a cylindrical upper portion having a radius r and a cylindrical lower portion having a radius R;   wherein r<R; and   wherein the gas supply tube protrusion protrudes into the retention chamber cylindrical upper portion.   
     
     
         18 . The purge plug of  claim 1 , wherein the gas supply tube has a termination point within the retention chamber, and wherein the gas supply tube comprises a check valve.