Method of Predicting Shrinkage Defects and Deriving Process Conditions in HPDC (High-Pressure Die-Casting) for Electric Vehicle Motor Housings

Shrinkage porosity is one of the most common defects leading to rejection in high-pressure die-casting (HPDC). As the metal solidifies, it contracts and shrinks in volume. If the cooling rate is too rapid or the metal is not sufficiently fluid, the shrinkage rate can exceed the rate of metal flow into the cavity, resulting in the formation of porosity. Shrinkage porosity appears as a network of small voids or pores, which can reduce the strength and integrity of the final product. This study aims to investigate the comparative effects of process parameters on shrinkage defects in HPDC. Our methodology focuses on examining four distinct casting models under various casting conditions, such as changes in molten metal injection temperature, injection speed. Despite the identified influence of these process parameters, it was observed that the part geometry plays a significant role in dictating the degree of shrinkage. While our results validate the effects of process parameters on shrinkage defects, it demonstrates the predominant role of the casting geometry. We employ the secondary dendrite arm spacing and dimensionless Niyama criteria for predicting shrinkage defects, verifying our simulation data with empirical evidence from an in-process-embedding sensor-equipped casting machine. The results reveal a clear correlation between the processing parameters and shrinkage once a specific geometry is established. Within a given geometry, the extent of shrinkage defects follows a pattern determined by the processing conditions.