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

a. Inner surface defects
An inner flap: presenting a straight line, a spiral or a semi-helical sawtooth defect on the inner surface of the steel pipe.
inside scarring: scars in the steel pipe inner surface, generally easily peel off.
Warping: a straight line or intermittent small nail-like tilt leather. Often seen in the capillary head, and easy to peel.
inside straights: a straight shape scratch with a certain width and depth.
inner edge: a straight shape protrusion with a certain width and depth.
inner drum kits: a super and regular protrusion and outer surface is not damaged.
Pull pits: a regular or non-regular pit and the outer surface without damage.
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
An outer fold: the outer surface of the pipe presents a layered folded spiral.
separation: presenting a spiral shape or blocky delamination and cracking.
external scarring: scars on the outer surface.
pock surface: steel surface showed uneven pits.
Line: a substantially symmetrical or asymmetrical linear rolling marks.
Hairline: a continuous or discontinuous hairy fine lines.
net cracks: scaly small cracks.
scratches: linear or spiral-shaped groove-like defects.
touch deflated: the outer surface of the steel pipe rendered in a convex outer concave phenomenon, and pipe wall thickness without injury.
bumps: collision irregular scars.
straightening recess: steel spiral concave outer surface.
rolled off: longitudinally local or long presentation in a convex outer concave folds, the outer surface into strips depression.
crack:opened the rupture surface phenomenon, much produced in the thin-walled tube.
seamless pipe sizes
Out diameter: 1/2 inch - 36 inch (21.3mm-914.4mm)
Thickness: 2.11mm-60mm ( SCH10, SCH20, SCH40, SCH80, STD, SCH120, SCH160, XXS)

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https://www.nan-steel.com/news/seamless-steel-pipe-sizes.html