THREADED JOINT FOR STEEL PIPES

摘要

A threaded joint for steel pipes constituted by a pin having male threads and a box having female threads is improved with respect to ease of insertion of the pin and galling resistance of the threaded portions. The stabbing flanks of the threads in a complete thread portion of one of the pin and box has a two-step stabbing shape having a chamfer. The two-step stabbing shape has a stabbing flank angle .alpha. of 5 - 45° and a chamfer angle .beta. of 20 - 60°. The ratio h/H of the chamfer height h to the thread height H of the pin is 0.25 - 0.50, or the ratio of the cross-sectional area of the chamfered portion to the overall cross-sectional area of the stabbing flank is made at least a value corresponding to a chamfer height ratio h/H of 0.25 and at most a value corresponding to a chamfer height ratio of 0.50.