rullkon - borrkrona with improvements in skärelement placement and materials for optimization of skärarbete at the borehole corner

摘要

A rolling cone bit (10) includes a cone cutter (14, 15, 16) having a pair of adjacent rows of cutter elements (70, 80) that are positioned so as to divide the sidewall (5) and bottom hole (7) duty. The wear resistance, hardness and toughness of the cutter elements (70, 80) in the adjacent rows are optimized depending upon the type of cutting the respective rows perform. In most applications, the cutter elements (70) experiencing the sidewall cutting will have cutting surfaces that are more resistant or harder than the cutting surfaces of the cutter elements (80) in the rows experiencing more bottom hole duty. Likewise, the cutter elements (80) exposed to the bottom hole duty will generally be tougher than those (70) experiencing substantial sidewall cutting. The material enhancements include varying the grades of tungsten carbide used in the cutter elements (70, 80) and by selectively employing layers of superhard abrasives, such as PCD or PCBN. The cutter elements (70, 80) may be either inserts or steel teeth.