Study on Solidification Structure Evolution of Direct-Chill Casting High Purity Copper Billet Using Cellular Automaton-Finite Element Method

A heat transfer model and a cellular Automation-Finite Element (CAFE) coupling model were established to analyze the solid/liquid (S/L) interface and solidification structure evolution of high purity copper Direct-chill (DC) casting billet under different casting conditions. The simulation and actual experimental results of liquid sump shape and solidification structure were first compared to verify the accuracy of the model. It is proved that the model is effective for simulating the solidification structure of the actual DC casting high purity copper billet. After that, the model was used to predict the solidification structure under different casting temperatures, casting speeds, and heat transfer coefficients. It is shown that, with the increase of casting temperature, the grain size decreases first and then increases. There is a compromise between grain size and its uniformity, and the grain size is more uniform at higher casting temperature. With the increase of casting speed, the depth of liquid sump and the height of the S/L interface increase, but the total grain number of the billet cross-section decreases gradually. As the heat transfer coefficient increases, the depth of the casting liquid sump becomes shallow, but the height of the solid-liquid interface increases and the grain size increases gradually. For the preparation of high purity copper billets with large cross-sectional dimensions by DC casting, a fine solidified structure could be obtained by appropriately reducing the casting speed and cooling intensity.