Hot tearing criteria evaluation for direct-chill casting of an Al-4.5 pct Cu alloy

Predicting the occurrence of hot tears in the direct-chill (DC) casting of aluminum alloys by numerical simulation is a crucial step for avoiding such defects. In this study, eight hot tearing criteria proposed in the literature have been implemented in a finite-element method simulation of the DC casting process and have been evaluated. These criteria were based on limitations of feeding, mechanical ductility, or both. It is concluded that six criteria give a higher cracking sensitivity for a higher casting velocity and that five criteria give a higher cracking sensitivity for the center location of the billet. This is considered in qualitative accordance with casting practice. Seven criteria indicate that use of a ramping procedure (lower casting speed during start-up phase) does not make a significant difference. However, in industrial practice, this is a common procedure, needed for avoiding hot cracking. Only one criterion is in qualitative accordance with casting practice, but it fails to quantitatively predict the hot tearing occurrence during DC casting.