Effect of wiper on thermal stresses during direct chill casting of magnesium alloy

Abstract

Understanding the thermomechanical behaviour of an alloy during the Direct Chill (DC) casting process is essential to alleviate the defects in the casting. In this work, conventional direct chill casting process is numerically modelled for evaluating the thermal stress profiles in the casting of AZ31 magnesium alloy. A cooling strategy is used where a wiper is positioned below the mold to reduce the cooling intensity and magnitude of thermal stresses. In this work, the effect of the wiper on the reduction of thermal stress is analysed in detail during the DC casting of AZ31 magnesium alloy. A 2-D computational domain growing along with the casting speed is used to replicate the DC casting process. The temperature and stress profiles are calculated by sequentially solving the energy and momentum balance using the Finite Element Method. The effect of a cooling strategy, on the variation of radial, axial and circumferential stresses is analysed. It is observed that there is a decrease in the circumferential and radial stresses developed in the billet below the mold. Implementation of wiper resulted in higher temperature billet surface which led to reduction of the stresses both in the circumferential and radial direction.