On the damage mechanisms in a continuous casting mold: After-service material characterization and finite element simulation

A mold is a part of a continuous casting plant where the molten steel starts to solidify. The inner surface of the mold undergoes a cyclic thermal load. In fact, service conditions are characterized by a high thermal flux, which vanishes when the plant is switched off. The highest temperatures occur in the area just beneath the free level of liquid steel (meniscus). The same area is typically characterized by thermal fatigue cracks when the mold is inspected after service. This work presents the characterization of the material of a copper mold after it had been used in the plant. The aim was to understand the damage and cracking mechanism, and our analysis confirmed that a network of cracks was present on the inner mold surface in the meniscus area, which experienced the maximum temperature gradients. Metallurgical examination demonstrated the transgranular characteristics of cracks, thus suggesting that thermal fatigue was the main cause of the damage observed. The location of the thermal fatigue cracks corresponded to the area experiencing the highest levels of plastic strains, as confirmed by the results of a finite element analysis simulating the mold in- service conditions.