| 摘要 |
PROBLEM TO BE SOLVED: To provide a small drill which is made of tungsten carbide-based cemented carbide and has a very small outside diameter of at most 0.1 mm, and has a long breakage-free life, and is suitable for drilling a printed board. SOLUTION: The small drill made of the tungsten-carbide-based cemented carbide contains 13-25 wt.% Co and/or Ni, 0.1-2.0 wt.% VC, 0.1-2.0 wt.% Cr<SB>3</SB>C<SB>2</SB>, 0.01-0.4 wt.% TaC, and the balance of tungsten-carbide and unavoidable impurity, and has an average grain diameter of the tungsten carbide of at most 0.6μm, and satisfies the following conditions, (Cr<SB>3</SB>C<SB>2</SB>+VC)/(Co+Ni)>0.07, Cr<SB>3</SB>C<SB>2</SB>/(Co+Ni)<0.057, VC/Cr<SB>3</SB>C<SB>2</SB>>0.65. In addition, the diameter of the drill is at most 0.1 mm. COPYRIGHT: (C)2005,JPO&NCIPI
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