Hot-rolled (extruded seamless steel tube): Round billet → Heating → Piercing → Three-roller oblique rolling, continuous rolling, or extrusion → Tube removal → sizing (or reduction) → Cooling → Straightening → Hydrostatic test (or flaw detection) → Marking → Storage
2. Cold Drawn (rolled) Seamless Steel Tubes: Round Billet → Heating → Piercing → Heading → Annealing → Pickling → Oiling (Copper Coating) → Multi-pass Cold Drawing (Cold Rolling) → Bloom → Heat Treatment → Straightening → Hydrostatic Test (Non-destructive Testing) → Marking → Storage
