The inner spiral copper tube produced by extrusion-rolling process has a kind of special line defect,which influences the production yield remarkably.

In the light of the status that there are caustic faults in the oil well tubing and there are not effective inspections, in this paper the plane roundness fault model of the is studied, and the magnetic leakage flux distributing model at the direction of the normal of the roundness fault is proposed.

Tension-leveling can eliminate shape defects effectively, so as to increase the quality of strip.

Tension-leveling line now is widely used in high quality aluminium rolling production, because it can eliminate shape defects such as wave and warp effectively.