Prediction of columnar-to-equiaxed transition and porosity in continuous cast billet

摘要

Columnar-to-equiaxed transition (CET) plays an important role in alloy solidification, whereas the porosity typically forms in castings during the solidfication process. Although the famous Hunt CET criterion and Niyama porosity criterion are widely used in previous studies, the predicted results had some shortcomings to some extent. In order to control both the porosity and CET better, the new criteria for them were proposed in this work, based on the previous studies and the modification performed according to the simulated and experimental results. The thresholds of shrinkage porosity (500 or 2000) and CET (4 x 10(9) or 10 x 10(9)) were achieved for the experimental conditions in this work. Then, with the new criteria, the effects of electromagnetic stirring (EMS) on CET and porosity had been studied. The results show that M-EMS significantly affects the CET and porosity, whereas the effect of F-EMS is relatively slight. The solidification map built based on the temperature gradient and cooling rate could provide a reference for the optimization of solidification.