The invention relates to an
oil drilling tool, and in particular to a
friction welding type kelly bar, which comprises a
pipe body and a first joint and a second joint respectively positioned at two ends of the
pipe body; the shape of the section of the
pipe body is a square or hexagon; the pipe body is connected with the first joint and the second joint in a
friction welding mode; and the
welding parameters are that: the first-level friction pressure is between 3 and 5MPa and the time is 20 to 60 seconds; the second-level friction pressure is between 4 and 8MPa and the time is 60 to 180 seconds; and the upsetting force is between 10 and 18MPa. The
friction welding type kelly bar has the advantages that: the friction
welding type kelly bar is manufactured in segments, the manufacture is simple and the production efficiency is high; raw materials and energy are saved, and the cost is greatly reduced; and the
processing quality is easily guaranteed and the
processing accuracy is high. For the manual
welding mode adopted by the conventional kelly bar, welding lines generated easily have
crystal defects such as bubbles, segregation, inclusion, cracks and the like so as to severely influence the strength and service life of a kelly bar; and compared with the manual welding, the friction welding ensures that the joints have good and stable quality and are not melted in the
welding process, and belongs to
solid-phase hot-pressure welding, and the joints have
forging textures, so the welding lines do not have the
crystal defects such as bubbles, segregation, inclusion, cracks and the like, and the strength of the joints by the friction welding is far greater than that by
fusion welding and braze welding, and reaches or even surpass the strength of a
base metal.