Unveiling the mechanisms behind the inconsistent impact of casting pressure on macro and microsegregation

Abstract

Segregation is a common defect in the casting process of metallic materials. This phenomenon leads to uneven variations in the mechanical properties, corrosion resistance, and machinability of the material, ultimately increasing processing difficulty and affecting the quality and performance of the product. In this study, the impact of casting pressure on the segregation of M42 high-speed steel (HSS) during die casting was systematically investigated. The results indicated that there is inconsistency in the impact of casting pressure on macrosegregation and microsegregation, that is, as the casting pressure increases, the degree of macrosegregation mitigates, while the degree of microsegregation enhances. For macrosegregation, increasing the casting pressure reduces the width of the mushy zone and expands the range of the slurry zone, which promotes feeding flow and inhibits the transport of carbon solutes by the flowing molten steel to the center, thereby mitigating macrosegregation in the ingot center. For microsegregation, as the casting pressure increases, the grain size significantly decreases and the cooling rate increases. This leads to a shortened solidification time and a weakening of the back-diffusion effect in the solid phase. Therefore, as the casting pressure increases, the degree of microsegregation is enhanced. This study unveils the mechanisms behind the inconsistent impact of casting pressure on macrosegregation and microsegregation during die casting, providing theoretical guidance for alleviating segregation and reducing processing difficulty by controlling casting pressure.