Cemented tungsten carbide rock bit cone

Abstract

An earth-boring bit has a steel body and bearing pin for rotatably supporting a cone. The cone has an exterior surface containing rows of cutting elements. The cone and cutting elements are formed of cemented tungsten carbide. The cone may be manufactured by applying pressure to a mixture of hard particles and metal alloy powder to form a billet, then machining the billet to a desired over-sized conical shaped product. Then the conical-shaped product is liquid-phase sintered to a desired density, which causes shrinking to the desired final shape.

1 . An earth boring bit, comprising:
 a bit body having at least one bearing pin depending therefrom; and   a cone rotatably mounted to the bearing pin, the cone having a plurality of cutting elements, the cone and the cutting elements each being formed of sintered composite material comprising hard particles sintered with a metal alloy binder.   
   
   
       2 . The bit according to  claim 1 , wherein:
 the hard particles are selected from a group consisting of diamond, boron carbide, boron nitride, aluminum nitride, and carbide or borides of the group consisting of W, Ti, Mo, Nb, V, Hf, Ta, Cr, Zr, A, and Si; and   the binder is selected from a group consisting of cobalt, nickel, iron, titanium and alloys thereof.   
   
   
       3 . The bit according to  claim 2 , wherein the amount of binder relative to the hard particles is in the range from about five to forty percent by weight. 
   
   
       4 . The bit according to  claim 1 , wherein the cutting elements comprise teeth that are integrally formed with the cone. 
   
   
       5 . The bit according to  claim 1 , wherein the cutting elements comprise separately formed inserts attached to the cone. 
   
   
       6 . An earth boring bit, comprising:
 a body having a plurality of bearing pins, each depending therefrom and extending downward and inward toward a bit axis of rotation, the body and the bearing pins being formed of a steel alloy;   a plurality of cones, each of the cones having an inner cavity that mounts on one of the bearing pins for rotation relative to the bearing pin as the body of the bit rotates;   each of the cones having an exterior surface containing a plurality of cutting elements protruding therefrom; and wherein   the cones and the cutting elements are formed of cemented tungsten carbide.   
   
   
       7 . The bit according to  claim 6 , wherein the cutting elements comprise teeth that are integrally formed with each of the cones. 
   
   
       8 . The bit according to  claim 6 , wherein the cutting elements comprise separately formed inserts that are attached to the cones. 
   
   
       9 . The bit according to  claim 6 , wherein the cemented tungsten carbide has a binder metal selected from a group consisting of cobalt, nickel, iron and alloys thereof. 
   
   
       10 . A method of manufacturing a cone for an earth boring bit, comprising:
 (a) placing a powder of hard particles and a metal binder in a mold; then   (b) applying pressure to the powder to form a billet;   (c) machining the billet to create a cone-shaped product out of the billet; then   (d) sintering the cone-shaped product to a desired density.   
   
   
       11 . The method according to  claim 10 , wherein:
 step (c) comprises machining the billet so that at least some of the dimensions of the cone-shaped product are selectively oversized from the desired final dimensions of the cone; and   during step (d), the cone-shaped product shrinks to substantially the desired final dimensions of the cone.   
   
   
       12 . The method according to  claim 10 , wherein step (c) further comprises machining teeth on the cone-shaped product. 
   
   
       13 . The method according to  claim 10 , wherein:
 step (c) further comprises machining a plurality of holes in the billet; and   the method further comprises after step (d), installing cemented carbide cutting elements into the holes.   
   
   
       14 . The method according to  claim 13 , wherein the method further comprises:
 inserting cylindrical displacement members into the holes after step (c), the displacement members having a desired finished diameter for the holes;   and step (d) further comprises leaving the displacement members in the holes while sintering to limit the shrinkage of the holes.   
   
   
       15 . The method according to  claim 10 , wherein step (c) is performed while the billet is in a completely unsintered condition. 
   
   
       16 . The method according to  claim 10 , further comprising:
 after step (b) and prior to step (c), heating the billet to partially sinter the billet.   
   
   
       17 . The method according to  claim 10 , wherein:
 step (c) further comprises machining a cylindrical cavity within the billet for mounting the cone to a bearing shaft of the bit; and the method further comprises after step (d), finish machining the cylindrical cavity into a bearing surface having a desired dimension and surface finish.   
   
   
       18 . The method according to  claim 10 , wherein the wherein the hard particles comprise:
 a material selected from diamond, boron carbide, boron nitride, aluminum nitride, and carbide or borides of the group consisting of W, Ti, Mo, Nb, V, Hf, and Ta. Cr, Zr, A, and Si; and   the binder is selected from a group consisting of cobalt, nickel, iron, titanium and alloys thereof.   
   
   
       19 . The method according to  claim 10 , wherein step (b) is performed by:
 placing and sealing the powder within a flexible and impermeable container;   surrounding the container with a fluid; and   applying pressure to the fluid.   
   
   
       20 . The method according to  claim 10 , wherein step (b) is performed by:
 placing the powder within a cavity of a rigid mold; then   forcing a ram against the powder.