An integrated 3D Direct Chill (DC) casting model was used to simulate the heat transfer, fluid flow, solidification, and thermal stress during casting. Temperature measurements were performed in an industrial casting facility to setup and validate the model. The key features such as heat transfer between cooling water and the ingot surface as a function of surface temperature, cooling water flow rate, air gaps caused by mold and bottom block design were also considered in the model. An elasto-viscoplastic constitutive model, which was determined based on mechanical testing, was used to calculate the evolution of stress during casting. The stress evolution was compared at various locations and correlated with physical phenomena associated with the casting process. An Ingot Cracking Index, which represents the ingot hot cracking propensity, was established based on the ratio of stress to strength. The Index calculation results were consistent with observations in industrial casting practice.