| 摘要 |
PROBLEM TO BE SOLVED: To provide a drill made of a sintered body of microstructure displaying excellent chipping resistance on its cutting blade face of a point face. SOLUTION: This drill having a shank part and a groove forming part using a point face as a cutter face and having an outer diameter of 4-16 mm, is composed of a sintered body of microstructure in which a dispersion phase finely grained by including Cr, occupies 85-98 area % in average on the basis of the observation of the structure by a scanning electron microscope, the remained part is composed of a binding phase and an unavoidable impurity, the dispersion phase forming the sintered body is composed of a single phase of a composite carbide solid solution of W, Co, Cr including Co and Cr in tungsten carbide in a solid solution state in observing the structure by a transmission-type electron microscope under a condition that a content of Co is 0.1-3 wt.%, and that of Cr is 0.1-2 wt.% in average in the dispersion phase, and the binding phase is composed of a Co group alloy single phase including 1-8 wt.% of Cr in average in the binding phase in observing the structure by the transmission-type electron microscope.
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