| 摘要 |
PURPOSE:To enhance durability by defining the material of a cemented carbide tip for both ends of cutter bits as low hardness and high toughness out of cemented carbide tips installed in parallel to cutter bits and the material of a cemented carbide tip in the central part as high hardness and high toughness. CONSTITUTION:A tip mounting recessed part 14 is formed on the tip of a sheet- like base metal 13 which constitutes a mounting part of the base end. A plurality of cemented carbide tips 15, 16, 17 and 18 are fixed with the tip mounting recessed part 14 by brazing 16 in such a state that they may line up breadthwise. To braze with the tips 15 ad 18 on both ends, there is adopted a material having a low hardness and high toughness out of the cemented carbide tips 15, 16, 17 and 18. Then, when excavating a hard ground or the like by mounting a cutter bit 11 to a cutter head of a shield driving machine, a face pressure exerting on the chips 15 and 18 on both ends is reduced, thereby protecting the chips 15 and 18 from being damaged. Although the tips 15 and 18 are subjected to wear out during excavation work, the properties of the hardness and high toughness tips 16 and 17 prevents a drop in their wearing properties. |
