| 摘要 |
PROBLEM TO BE SOLVED: To provide a cemented carbide-made miniature drill capable of exerting excellent wear resistance at high-speed drill processing. SOLUTION: This miniature drill comprises a groove forming portion and a shank portion of which the above groove forming portion is at least composed of the cemented carbide, and also the above groove forming portion is divided into a body portion, an intermediate portion and a tip cutting edge face portion along a longitudinal direction, furthermore, the above body portion is made to contain Co: 4-13%, Cr: 0.1-0.7%, V: 0.1-0.5%, in mass % as every connecting-phase forming component, the remains of them are made to compose the cemented carbide having a composition comprising WC as a hard-phase forming component and inevitable impurities, and the above intermediate portion is composed of the cemented carbide having the content of the connecting-phase forming component less than 10-50% in comparison with that of the connecting-phase forming component of the above body portion, and furthermore, the above tip cutting edge face portion is composed of the cemented carbide having the content of the component for forming the connecting phase less than 10-50% in comparison with that of the component for forming the connecting-phase of the above intermediate portion, though Co more than 1 in mass % is contained.
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