Thermal Analysis of Direct Chill Casting

Direct Chill (DC) casting is a semi-continuous casting technique which is used to produce aluminum rolling ingots and extrusion billets. The knowledge of temperature field is highly essential for the prediction of displacement field and hot tears. Modeling the thermal field of DC casting is a challenging task due to the liquid-solid phase transition, time-dependent domain and boundary conditions, inverse nature of secondary boundary conditions, etc. Therefore, an attempt is made to model the thermal field of DC casting using a finite element method. A temperature-based finite element model is used to capture the effect of latent heat release. A temperature-dependent heat transfer coefficient is employed to incorporate the bottom block and mold boundaries. The influence of casting speed is studied in detail. Through the proper ramping procedures, it is proved that the start-up phase sump depth and mushy length can be lowered. However, it is found that the steady-state sump parameters are independent of ramping. Further, the influences of secondary cooling profile, and melt superheat are investigated. AA1201 alloy is considered for the study.