Hot Rolled (Extruded Seamless Steel Pipe): Round billet → Heating → Piercing → Three-roller oblique rolling, continuous rolling, or extrusion → Tube removal → sizing (or reduction in diameter) → Cooling → Straightening → Hydrostatic test (or flaw detection) → Marking → Storage
2. Cold Drawn (rolled) Seamless Steel Tubes: Round billet → Heating → Piercing → Heading → Annealing → Acid washing → Oiling (copper plating) → Multi-pass cold drawing (cold rolling) → Bloom → Heat treatment → Straightening → Hydrostatic test (non-destructive testing) → Marking → Storage