Detection of Defects on Cold Rolling Mill (CRM) Rolls with Ultrasonic and Eddy Current Flaw Dectors

Abstract

The service induced defects in CRM rolls, due to them being subjected to complex mechanical & thermal stresses in cold rolling of steel strips or coils, if not removed completely during roll grinding, become primarily respo-nsible for roll spalling. The high instances of roll spalling lead to increased specific roll consumption and production delays. The inspection of some 15-20% of CRM work rolls with portable Ultrasonic and Eddy Current flaw detectors was undertaken to detect and remove the service induced defects on surface & sub-surface regions of rolls which would otherwise have remained undetected leading to roll spalling and other associated failures. The incid-ences of spalling has reduced by up to 38% during the period of roll inspection compared to the spalling incid-ences in the prior periods of time leading to prolonged uses of rolls. Although no reduction in Specific Roll Consumption (SRC) has been observed, the loss of useful roll materials due to reduced incidences of spalling has reduced. The reduced occurences of roll spalling have also resulted in savings of premature roll changing time lead-ing to increased mill availibility.