Ball hole welding using the friction stir welding (fsw) process

Abstract

A roller cone drill bit includes a bit body, at least one leg extending downward from the bit body, a journal on each leg, and a roller cone mounted on each journal. A ball race is configured between each journal and roller cone, and a plurality of retention balls is disposed within each ball race. A ball hole extends from the back face of each leg to the ball race, and a ball hole plug fits within the ball hole. The ball hole plug is secured to the leg by a friction stir weld.

1 . A roller cone drill bit, comprising:
 a bit body;   at least one leg extending downward from the bit body, wherein each leg comprises a leg back face and a journal and each journal has a journal race surface;   a roller cone mounted on each journal, wherein each roller cone has a roller cone race surface;   a ball race configured between the journal race surface and the roller cone race surface;   a plurality of retention balls disposed within the ball race;   a ball hole extending from the leg back face to the journal race surface; and   a ball hole plug, wherein the ball hole plug is secured to the leg by a friction stir weld.   
     
     
         2 . The roller cone drill bit of  claim 1 , wherein the ball hole plug is welded directly to the leg back face without a filler material. 
     
     
         3 . The roller cone drill bit of  claim 1 , wherein the ball hole plug material is the same as the leg material. 
     
     
         4 . The roller cone drill bit of  claim 1 , wherein the ball hole plug comprises a material selected from at least one of austenitic stainless steel, high alloy carbon steel, and nickel and cobalt based alloys. 
     
     
         5 . The roller cone drill bit of  claim 3 , wherein the high alloy materials are nickel based materials. 
     
     
         6 . The roller cone drill bit of  claim 1 , wherein the ball hole plug comprises the same material as the leg. 
     
     
         7 . The roller cone drill bit of  claim 1 , wherein the ball hole plug comprises a different material from the leg. 
     
     
         8 . The roller cone drill bit of  claim 7 , wherein the ball hole plug comprises material with a higher yield strength and higher toughness than the leg. 
     
     
         9 . The roller cone drill bit of  claim 1 , wherein the ball hole plug is heat treated. 
     
     
         10 . The roller cone drill bit of  claim 1 , further comprising a keyhole in the friction stir weld. 
     
     
         11 . The roller cone drill bit of  claim 1 , wherein no keyhole remains in the friction stir weld. 
     
     
         12 . The roller cone drill bit of  claim 1 , wherein the ball hole plug comprises:
 a plug head, wherein the plug head comprises a top surface and a side surface;   a plug body; and   a ball retainer end.   
     
     
         13 . The roller cone drill bit of  claim 12 , wherein the top surface of the plug head is flush with the leg back face. 
     
     
         14 . The roller cone drill bit of  claim 12 , wherein the friction stir weld extends down the entire side surface of the plug head. 
     
     
         15 . The roller cone drill bit of  claim 12 , wherein the friction stir weld extends down to a depth of the side surface. 
     
     
         16 . The roller cone drill bit of  claim 12 , wherein the plug head is non-cylindrical. 
     
     
         17 . The roller cone drill bit of  claim 16 , wherein the ball hole is non-cylindrical at the opening to the leg back face. 
     
     
         18 . A roller cone drill bit, comprising:
 a bit body;   at least one leg extending downward from the bit body, wherein each leg comprises a leg back face and a journal and each journal has a journal race surface;   a roller cone mounted on each journal, wherein each roller cone has a roller cone race surface;   a ball race configured between the journal race surface and the roller cone race surface;   a plurality of retention balls disposed within the ball race;   a ball hole extending from the leg back face to the journal race surface, wherein the ball hole is non-cylindrical near the leg back face; and   a ball hole plug, wherein the ball hole plug is secured to the leg by a friction stir weld, the ball hole plug, comprising:
 a plug head, wherein the plug head is non-cylindrical; 
 a plug body; and 
 a ball retainer end. 
   
     
     
         19 . The roller cone drill bit of  claim 19 , wherein the ball retainer end has a mating curve with the same radius of curvature as the race. 
     
     
         20 . A method for retaining a roller cone on a bit leg, comprising:
 mounting a roller cone on a journal extending downward from the bit leg;   inserting a plurality of retention balls into a ball hole extending through a leg back face to the journal;   inserting a ball hole plug into the ball hole; and   friction stir welding the ball hole plug to a back face of the bit leg.   
     
     
         21 . The method of  claim 21 , further comprising providing an additive material and friction stir mixing the additive material into the bit leg. 
     
     
         22 . The method of  claim 21 , further comprising covering the ball hole plug with a plate prior to friction stir welding, wherein the friction stir welding welds the ball hole plug, the plate, and the bit leg together. 
     
     
         23 . The method of  claim 23 , wherein the ball hole plug is friction stir welded to the bit leg prior to friction stir welding the plate. 
     
     
         24 . The method of  claim 21 , wherein the ball hole plug comprises a non-cylindrical head and the ball hole is non-cylindrical near the back face of the bit leg. 
     
     
         25 . The method of  claim 21 , further comprising welding a plurality of bit legs together. 
     
     
         26 . A method for retaining a roller cone on a bit leg, comprising:
 inserting a plurality of retention balls into a ball hole;   inserting a ball hole plug into the ball hole;   friction stir welding the ball hole plug to a back face of the bit leg using a friction stirring tool; and   removing the friction stirring tool.   
     
     
         27 . The method of  claim 27 , further comprising removing the friction stirring tool at an initial removal location. 
     
     
         28 . The method of  claim 27 , further comprising removing the friction stirring tool by a gradual removal process, wherein the gradual removal process comprises:
 beginning the removal of the friction stirring tool at an initial removal location;   gradually removing the friction stirring tool as the friction stirring tool is moved a distance away from the initial removal location; and   completely removing the friction stirring tool at a distance from the initial removal location.   
     
     
         29 . The method of  claim 27 , wherein removing the friction stirring tool comprises pulling the friction stirring tool onto a sacrificial material.