Centrifugally-cast tube and related method and apparatus for making

Abstract

An improved centrifugally-cast tube is provided, along with a related method and apparatus of making the tube. The tube includes a plurality of grooves and bosses that are mechanically machined into an interior surface of the tube, such as by a broaching process. The profile of grooves and bosses may be defined by a plurality of intersecting concave and convex radii. The tube is resistant to creep, carburization and metal dusting. The tube also has an enhanced heat transfer rate, and a desirable surface roughness. A method of making the tube is also provided. The method essentially consists of mechanically deforming the interior surface of the tube by passing a series of cutting inserts on support rings having incrementally-differing dimensions over the interior surface. An apparatus is also provided which includes a telescoping shaft upon which is mounted at least one cutting tool that has a plurality of cutting inserts and is adapted to form a plurality of grooves and bosses in the interior surface of the tube. The grooves and bosses may be straight or spiraled.

1 - 7 . (canceled) 
   
   
       8 . A method of improving a centrifugally-cast tube comprising:
 passing a first cutting tool having a plurality of first cutting inserts through a bore of the tube so as to mechanically remove a first quantity of material from the bore and to commence the formation of a plurality of grooves and bosses;   passing a second cutting tool having at plurality of second cutting inserts through the bore so as to mechanically remove a second quantity of material from the bore and to continue the formation of the plurality of grooves and bosses, the plurality of second cutting inserts having dimensions different than corresponding dimensions of the plurality of first cutting inserts; and   continuing to pass additional cutting tools having a plurality of additional cutting inserts through the bore so as to continue to mechanically remove additional quantities of material from the bore until a desired profile of grooves and bosses is achieved, each set of additional cutting tools having dimensions different than corresponding dimensions of the cutting inserts employed in the immediately preceding pass.   
   
   
       9 . The method of  claim 8 , wherein the dimensions of each subsequent set of cutting tools are larger than the corresponding dimensions of the cutting tools employed in the immediately preceding pass. 
   
   
       10 . The method of  claim 9 , wherein the dimensions incrementally increase at a rate of between 0.05 mm and 0.1 mm per pass. 
   
   
       11 . A method of improving a centrifugally-cast tube comprising:
 forming a plurality of grooves and bosses in an interior surface of the tube by mechanically deforming the interior surface.   
   
   
       12 . The method of  claim 11 , wherein the plurality of grooves and bosses are gradually formed by passing a series of cutting tools having incrementally-differing dimensions over the interior surface. 
   
   
       13 - 21 . (canceled)