Change in Porosity of A356 by Holding Time and Its Effect on Mechanical Properties

In most of the practical casting operations, it is important to be able to cast large number of part with one single melt. Therefore, when quantity of the charge and melting crucible is increased, during casting process, the liquid is led to settle for a long period of time. In this work, 10 kg charge of A356 was melted at 750 °C and held for 240 min. A sand mold with different thickness was cast at 30, 60, 120, and 240 min of holding time of the liquid, before and after degassing conditions. Melt quality was measured by reduced pressure test, and pore size and number were measured at each cast part. A correlation between bifilm index and tensile properties was established. It was found that melt quality was decreased with increased holding time and pore formation was enhanced linearly. Additionally, mechanical properties of the alloy were decreased with decreased melt quality and increased pore formation due to holding time of the liquid. © 2018, ASM International.