| 摘要 |
PROBLEM TO BE SOLVED: To improve an anti-plastic deformation property easy to generate on the corner of an outer periphery, while keeping an anti-chipping property by specifying the Co content of a cemented carbide to a specific weight %, the average grain diameter of WC and the lattice constant of Co. SOLUTION: When a Co content is less than 5 weight %, the strength of a cemented carbide is low and a twist drill is easy to break and when it is contained beyond 12 weight %, as an anti-plastic deformation property is deteriorated, it is made to 5-12 weight %. As the WC average grain diameter is less than 0.3μ, the hardness of the cemented carbide becomes extremely high and its toughness is deteriorated and when it exceeds 1.2μ, as the anti-water property is deteriorated, it is made to 0.5-1.2μ. The lattice constant of Co is made to 3.565Å-3.575Å, as the deterioration of the anti-chipping property and the solid solution reinforcement of Co itself are not enough at the high carbon side of less than 3.565Åand when it exceeds 3.575Å, as a weak decarburizing phase is appeared.
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