Tube-forging method

Abstract

A tube is made by first making a tubular billet with a central cavity by a primary shaping operation. Then the billet is fed to a radial forging machine where it is forged into the tube by decreasing an outer diameter of the billet and a radial thickness of a wall of the billet.

1 . A method of making a tube, the method comprising the steps of:
 making a tubular billet with a central cavity by a primary shaping operation;   feeding the billet to a radial forging machine; and   forging the billet into the tube by decreasing an outer diameter of the billet and a radial thickness of a wall of the billet.   
     
     
         2 . The tube-making method defined in  claim 1 , wherein the primary shaping operation is electro-slag conversion. 
     
     
         3 . The tube-making method defined in  claim 1 , wherein the primary shaping is rotary casting. 
     
     
         4 . The tube-making method defined in  claim 1 , further comprising the step after making the billet and before feeding the billet to the forging machine of:
 mechanically machining the billet.   
     
     
         5 . The tube-making method defined in  claim 4 , wherein the mechanical machining removes a surface skin from the billet. 
     
     
         6 . The tube-making method defined in  claim 4 , further comprising the step after making the billet and before feeding the billet to the forging machine of:
 heating the billet.   
     
     
         7 . The tube-making method defined in  claim 4 , wherein between the step of making the billet and the step of feeding the billet to the forging machine the billet is not heated. 
     
     
         8 . The tube-making method defined in  claim 4 , further comprising the step before feeding the billet to the forging machine of:
 descaling the billet.   
     
     
         9 . The tube-making method defined in  claim 8 , wherein high pressure is used to descale the billet. 
     
     
         10 . The tube-making method defined in  claim 1 , further comprising the step before feeding the billet to the forging machine of:
 coating an inner surface of the billet that defines the cavity with a lubricant.   
     
     
         11 . The tube-making method defined in  claim 10 , wherein the lubricant includes glass, phosphate, or graphite.