Method of making electrical heater bars

Claim 1

METHOD OF MAKING AN ELECTRIC FURNACE BAR HAVING A HOT ZONE BETWEEN COLD ENDS COMPRISING FORMING A TUBE OUT OF SILICON CARBIDE FINES AND A TEMPORARY BINDER; HEATING THE TUBE TO BETWEEN 1650*C. AND 2650*C. AND THEREBY RECRYSTALLIZING THE SILICON CARBIDE; PLUGGING ONE END OF THE TUBE WITH A REFRACTORY PLUG; FILLING THE TUBE TO THE LENGTH OF THE COLD END MINUS THAT OF THE PLUG AND MINUS THAT OF THE PORTION OF THAT COLD END WHICH MIGHT, UNDER THE HIGHEST TEMPERATURE CONDITIONS UNDER WHICH THE BAR IS OPERATED, BE EXPOSED TO TEMPERATURE AS HIGH AS 1000* C. WITH SILICON; INSERTING A SECOND REFRACTORY PLUG; FILLING THE TUBE TO THE LENGTH OF THE HOT ZONE PLUS THOSE PORTIONS OF THE TWO COLD ENDS OF THE BAR WHICH MIGHT BE EXPOSED TO TEMPERATURES HIGHER THAN 1000*C., WITH MOLYBDENUM SILICIDE; INSERTING A THIRD REFRACTORY PLUG; FILLING THE TUBE TO THE REMAINING LENGTH THEREOF MINUS THAT OF ANOTHER PLUG WITH SILICON; INSERTING ANOTHER REFRACTORY PLUG IN THE END OF THE TUBE; HEATING THE TUBE TO A TEMPERATURE OF BETWEEN 2000*C. AND 2600*C. UNDER REDUCING CONDITIONS THEREBY IMPREGNATING THE ENDS WITH SILICON AND THE MIDDLE WITH MOLYBDENUM SILICIDE; AND CUTTING A HELIX BETWEEN THE COLD ENDS TO FORM THE HOT ZONE.