The production process is different:
Hot-rolled (squeeze seamless steel tubes): round tube perforation → → → heated three-roll cross rolling, continuous rolled or extruded-cannula → sizing (or reducing) steel tube straightening → → → → cooling water pressure test (or testing) → tags → storage.
Precision seamless steel tube: round tube perforated → heat → → → → start → annealing pickling oil (copper) → multi-pass drawing (cold rolled) steel tube heat treatment straightening → → → → hydrostatic test (testing) → tags → storage.
Of different sizes:
Hot-rolled tube outer diameter 32~630mm. 2.5~75mm wall thickness. Cold rolled (cold drawn) outer diameter 5~200mm. 2.5~12mm wall thickness.
If to get size more small and quality better of seamless tube, must used cold rolled cold pulled or both joint of method cold rolled usually in II roll type mill Shang for, pipe in variable section round hole slot and not moving of tapered head by composition of ring hole type in the rolling, cold pulled usually in single chain type or double chain type cold pulled machine Shang for extrusion method is heating good of tube billet put in closed of extrusion cylinder within perforation rod and extrusion rod with movement, makes extrusion pieces from smaller of die hole in the extrusion, this method can production diameter smaller of pipe.