Spalling Failure Analysis and Resource of Back-up Roll for Cold Mill

Spalling failure had taken place on back up roll for cold mill.Through fracture morphology analysis,it was proved that main causes for roll’s spalling were contact fatigue.Due to the applied mill load and the localized flattening of the rolls at their contact point,the maximum resultant shear stress(Hertzian Stress) is located at a short distance below the roll surface.Cracks at multiple locations can initiate and propagate at that sub-surface location when the Hertzian Stress exceeds the compressive strength of the roll.