Inner fold of hot rolled seamless steel pipe refers to spiral rendered in the steel pipe inner surface, the semi-helical or irregular distribution of the zigzag folding, some rendered as linear warping. Below are details:

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.