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钻进坚硬岩层时为了提高钻头的平均进尺,中央设计局研制成－2型新式钻头(见图)。钻头焊嵌有6块长方平行六面体状的BK15硬合金片,其底部呈圆柱形。由于合金片
In order to increase the average drill footage when drilling into hard rock formations, the Central Design Bureau developed a new type-2 drill (see picture). Bits welded 6 square parallelepiped BK15 hard alloy piece, the bottom of a cylindrical shape. Because of alloy sheet