Method for producing a cathode steel bar with copper insert, and method for removing a copper insert from a used cathode bar

Abstract

The present invention relates to a method for producing a cathode steel bar with copper insert for use in an electrolytic cell for the electrolytic production of aluminium using the Hall-Héroult process. The present invention further relates to a method of removing a copper insert from a cathode bar used in an electrolytic cell for the electrolytic production of aluminium using the Hall-Héroult process, and reusing the copper from old copper inserts in production of new cathode bars with copper insert.

1 . A method for producing a cathode steel bar with copper insert for use in an electrolytic cell for the electrolytic production of aluminium using the Hall-Héroult process, comprising:
 i) providing a steel portion of the cathode steel bar equipped with a cavity for the copper insert and a sleeve on the upper part, 
 providing one or more solid copper item(s) sized to be inserted into the cavity of the steel portion, 
 entering the copper item(s) into the steel portion through the sleeve, 
 positioning at least one inductor in close proximity to at least parts of the outside of the steel portion, 
 supplying electric energy to the inductor, causing induction heating of the cathode steel bar to a temperature sufficiently high and for a time sufficiently long to molten at least the outer part of the copper item(s), 
 cooling, and solidifying the molten copper; 
 or 
 ii) providing a steel portion of the cathode steel bar equipped with a cavity for the copper insert and a sleeve on the upper part, 
 positioning at least one inductor in close proximity to at least parts of the outside of the steel portion, 
 supplying electric energy to the inductor, causing induction preheating of the cathode steel bar, 
 providing molten copper, 
 pouring the molten copper into the cavity of the steel portion through the sleeve, 
 cooling, and solidifying the molten copper, 
 wherein the cooling is carried out directionally, in a direction from the lower part of the cathode bar towards its upper part. 
 
     
     
         2 . The method, according to  claim 1 , comprising supplying electric energy with a frequency of between 1 kHz to 50 kHz from a power unit to the inductor. 
     
     
         3 . The method, according to  claim 1 , wherein the heating and preheating temperature is above the melting temperature of copper or copper alloy. 
     
     
         4 . The method, according to  claim 1 , wherein the heating and preheating be held for a period of 10 seconds to 12 hours. 
     
     
         5 . (canceled) 
     
     
         6 . The method, according to  claim 1 , wherein the directional cooling is obtained by upward moving of the inductor length wise along the cathode bar. 
     
     
         7 . The method, according to  claim 1 , wherein the method is circular in that the solid copper item(s) or molten copper is provided from used cathode bars. 
     
     
         8 . The method, according to  claim 1 , wherein the solid copper item(s) is provided from used cathode bars. 
     
     
         9 . The method, according to  claim 1 , wherein pouring of the molten copper into the cavity of the steel portion is obtained by top filling. 
     
     
         10 . The method, according to  claim 1 , wherein filling of the molten copper into the cavity of the steel portion is carried out by top or bottom filling. 
     
     
         11 . The method, according to  claim 9 , wherein the steel portion of the copper bar is kept at an angle during filling of molten copper. 
     
     
         12 . The method, according to  claim 1 , wherein the molten copper is provided from used cathode bars. 
     
     
         13 . A cathode steel bar with copper insert for use in an electrolytic cell for the electrolytic production of aluminium using the Hall-Héroult process, obtained by the process according to  claim 1 . 
     
     
         14 . A method of removing a copper insert from a cathode bar used in an electrolytic cell for the electrolytic production of aluminium using the Hall-Héroult process, comprising:
 providing an used cathode bar, 
 positioning an inductor in close proximity to at least parts of the cathode bar, 
 supplying electric energy to the inductor, causing induction heating of the cathode bar to a temperature above the melting temperature of copper, forming molten copper, 
 pouring the molten copper into a holding furnace; or 
 casting the molten copper into suitable items. 
 
     
     
         15 . The method, according to  claim 14 , comprising supplying electric energy with a frequency of between 1 kHz to 50 kHz from a power unit to the inductor. 
     
     
         16 . The method, according to  claim 4 , wherein the heating and preheating be held for a period of 1 minute to 1 hour. 
     
     
         17 . The method, according to  claim 10 , wherein the steel portion of the copper bar is kept at an angle during filling of molten copper.