| 摘要 |
PROBLEM TO BE SOLVED: To provide a miniature drill made of cemented carbide with high strength. SOLUTION: A miniature drill is composed of cemented carbide showing texture comprising a first hard dispersed phase: 65-92.5 area %, a second hard dispersed phase: 0.5-5 area % and a connection phase mainly composed of Co and unavoidable impurities: the rest by texture observation by an electron microscope. The first hard dispersed phase comprises coated WC with WC coated over the whole surface or partially with a thin layer of (V, W, Cr) C. The second hard dispersed phase comprises (V, W, Cr) C minutely dispersed and distributed in the connection phase, respectively having the average diameter of 0.7μm or less, and the content of Co, Cr, V are to be Co: 5-13%, Cr: 0.2-2%, and V: 0.2-1%.
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