What is it?

This defect looks like small breaks or lines in the steel surface (perpendicular to rolling direction of forming), usually after forming or bending. It is also known as coil breaks, cross breaks, luder lines, or yield point elongation. The defect can be caused when material is temper-passed to reduce or minimize the effect of fluting in the material. A tendency for fluting can return in the material even after temper-rolling over a matter of time (process of age hardening). Material stored at higher temperatures will harden faster and could be affected with fluting when formed.

Fluting