| 摘要 |
PROBLEM TO BE SOLVED: To provide a twisted drill having prolonged life by improving the strength and welding resistance of a cemented carbide used for the twisted drill; and by improving the welding resistance and abrasion resistance of the knife-edge of a tip blade at around its outer periphery liable to be high temperatures. SOLUTION: A twisted drill made of a cemented carbide and consisting of a B1 type solid solution phase, a WC phase, and a binder phase, consists of a solid phase, 50-70 percent by area, consisting of tungsten carbide, a solid phase, 15-30 percent by area, consisting of the B1 type solid solution phase, and the binder phase, 15-25 percent by weight, consisting of an iron-family metal. A sintered body has average grain sizes of 0.3 to 1.2 microns in the tungsten carbide phase and 0.3 to 2 microns in the B1 type solid solution phase, and a lattice constant of 3.565 to 3.575Åin Co.
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