from the conferences organized by TANGER Ltd. provisional website
Indefinite chill cast iron rolls are commonly used in the finishing stands in hot strip rolling mills. Due to characteristic rolling conditions in these stands and due to a hypoeutectic ledeburitic microstructure with graphite inclusions in the working layer, the mechanism of thermo-mechanical wear is different from earlier stands. Some research has been done on thermal fatigue crack formation and propagation in various alloys used for working layers in rolls. This research focuses on the impact of formation and propagation of extremely long cracks in some enhanced grades along with possible influence of the amount of added special carbide forming elements in these grades. These long cracks propagate from the surface of the roll inwards and may lead to bigger problems during rolling campaigns when not dealt with properly. Previous work also suggests that the ledeburitic network microstructure is indicative of the formation of thermal fatigue cracking on the surface of the roll. We analyzed the as-is microstructure of the roll’s surface after a campaign using silicon replicas to assess the crack mesh created on the surface during rolling. The results of this work highlight the combined influence of microstructure and thermo-mechanical fatigue in work roll degradation.Keywords: Indefinite chill cast iron, work rolls, thermal fatigue, crack propagation, roll surface degradation.