Studies on Ceramics Bits for Rock Drilling.

概要

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In order to investigate the effect of cutter shape on cutting forces and cutter strength, rock cutting tests were conducted using ceramics bits with different shapes of cutters. The results of the tests are summarized as follows:(1) A cylindrical cutter (13.3mm in diameter by 5mm thick) is most preferable in rock drilling with regard to the cutting forces (horizontal and vertical forces) and the cutter strength.(2) Si3N4 has better cutter strength than Al2O3.(3) Wear resistance of Si3N4 is higher, but its cutter strength in chipping is lower when compared to that of WC-Co. From results of the previous work (Misawa et al., 1990) and the rock cutting tests mentioned above, material of ceramics, rake angle and shape of cutter suitable for rock drilling became clear. HQ size ceramics core bits were designed based on these results, and their performance was evaluated by drilling tests. The results of the tests are as follows:(1) Bits with cutters of Si3N4 can be applied to the drilling of soft rocks.(2) Fixing method of ceramics in a bit matrix used in this study can be applied to make ceramics bits. To apply ceramics bits to harder rocks, ceramic itself must be improved concerning toughness. Furthermore, the method to fix ceramics on a bit body must be investigated widely to attain firm and inexpensive fixing of ceramics.
日本地熱学会の論文