Damage in hot rolling work rolls

Samples from a couple of work rolls employed in a hot rolling steel strip mill were examined by scanning electron microscopy in order to study their surface, as well as the wear mechanisms responsible for their damage. It was found that a series of cracks develop within the rolls at the beginning of their operational cycle, these cracks follow the primary carbide network and are attributed to be caused either by thermal fatigue or contact stresses or by a combination of both. Work rolls heat up as a result of contact with the steel strip and an oxide layer forms on them. It is observed that oxidation proceeds through the cracks, isolating healthy material with brittle layers, a characteristic which might explain the high wear rate encountered in some stands of the mill.