| 摘要 |
<p>The present invention relates to a thread joint of steel for percussive drilling wherein flushing water is used, comprising at least one substantially cylindrical external thread as well as a substantially cylindrical internal thread (12). The external thread is provided on a spigot (13) intended to constitute an integral part of a first drill string component. The threads (12) comprise thread flanks (16, 17; 18, 19) and thread roots (20; 21) provided between the flanks. The thread roots (20) of the cylindrical external thread are provided substantially distant from associated crests (22) of the cylindrical internal thread (12). By coating the thread roots (20) of the cylindrical external thread with at least one layer of a material of lower electrode potential than the steel, said layer being made from metals like aluminum, zinc and magnesium or alloys of these, an increased life length for the threaded connection is obtained.</p> |
