| 摘要 |
PURPOSE:To make a continuous long-distance excavation which excels in the anti-abrasiveness. CONSTITUTION:On the outer surface of a shank body 21 while contacts earth and sand and receives the earth pressure, an anti-abrasive layer 27 is provided which consists in a laminate of a super-hard alloy facial course 26 having a high toughness and a super-hard alloy inner layer 25 having a high hardness. The facial course 26 precludes local damage or exfoliation likely caused by an impact load due to debris, etc., while the inner layer prevents quick wear against eventual occurrence of local damage. |
