| 摘要 |
PROBLEM TO BE SOLVED: To improve precision of holes, shorten a processing time and reduce a variation in the processing time by closely examining causes of problems such as reduction in the precision of holes, an extension of the processing time and the variation in the processing time. SOLUTION: The cemented carbide is a tungsten carbide-based cemented carbide which comprises≤10 wt.%, preferably≤7 wt.% Co and≤0.5 wt.% each of Cr, V, Ta, Nb and other unavoidable impurities and has a specific resistance of≤0.3μΩm. The cemented carbide has a microstructure wherein an average grain size of WC is≥0.8μm and a coarse WC which is≥3 times larger than the average grain size of WC accounts for≤20% by area ratio. COPYRIGHT: (C)2004,JPO
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