Hot-rolled seamless steel pipe defects



Hot-rolled seamless steel pipe production base deformation process can be summarized as three stages: perforation, extension and finishing.

a. Inner surface defects
  1. An inner flap: presenting a straight line, a spiral or a semi-helical sawtooth defect on the inner surface of the steel pipe.
  2. inside scarring: scars in the steel pipe inner surface, generally easily peel off.
  3. Warping: a straight line or intermittent small nail-like tilt leather. Often seen in the capillary head, and easy to peel.
  4. inside straights: a straight shape scratch with a certain width and depth.
  5. inner edge: a straight shape protrusion with a certain width and depth.
  6. inner drum kits: a super and regular protrusion and outer surface is not damaged.
  7. Pull pits: a regular or non-regular pit and the outer surface without damage.
  8. internal thread (this defect produced only at Accel units): spiral traces often seen in the thin-walled tube surface, and there are obvious rugged feelings.
b. outer surface defects
  1. An outer fold: the outer surface of the pipe presents a layered folded spiral.
  2. separation: presenting a spiral shape or blocky delamination and cracking.
  3. external scarring: scars on the outer surface.
  4. pock surface: steel surface showed uneven pits.
  5. Line: a substantially symmetrical or asymmetrical linear rolling marks.
  6. Hairline: a continuous or discontinuous hairy fine lines.
  7. net cracks: scaly small cracks.
  8. scratches: linear or spiral-shaped groove-like defects.
  9. touch deflated: the outer surface of the steel pipe rendered in a convex outer concave phenomenon, and pipe wall thickness without injury.
  10. bumps: collision irregular scars.
  11. straightening recess: steel spiral concave outer surface.
  12. rolled off: longitudinally local or long presentation in a convex outer concave folds, the outer surface into strips depression.
  13. crack:opened the rupture surface phenomenon, much produced in the thin-walled tube.


Seamless pipe Specification, standard and identification

Seamless pipes are extensively applied for the nuclear device, gas, petrochemical, ship building and boiler industries. Seamless pipes dominates 65% of market share in Chinese boiler industry.