Thermal and mechanical behavior of copper molds during thin-slab casting (II): Mold crack formation

The formation of cracks in a funnel mold of thin-slab casting is investigated using metallographic studies and mathematical models. In Part II of this two-part article on thin-slab casting molds, short longitudinal cracks near the meniscus region of a thin-slab funnel mold are studied metallurgically. X-ray analyses revealed the formation of Cu-Zn brass on the copper matrix at high temperature where the crack initiated. Heat-transfer and thermal-elastic-viscoplastic stress models described in Part I are applied to investigate the temperature and stress fields associated with the cracks. Large cyclic inelastic strains were found in the funnel transition region just below the meniscus due to the slightly higher temperature at that location. The cracks then appear to have propagated by thermal fatigue caused by major level fluctuations at transitions. The stress and strain predictions suggest cycles to failure for molds for various hot-face temperatures.