Comparative Evaluation of Gating Systems in FeMnAl Castings

To understand the efficiency of gating systems, four systems, namely AFS styled pressurized system, AFS styled non-pressurized system, naturally pressurized system with a side riser and a naturally pressurized system with a top riser, were studied. The naturally pressurized systems were provided with overflows which collected the incoming metal swirl while the pressurized and non-pressurized systems had runner wells. Parameters like velocity of metal flow, air entrapment, microporosity and Niyama criterion were considered, and a design was developed with a common pouring basin using solidification software. Two molds were 3D printed using carbonitride sand, and steel of composition Fe-29Mn-8.2Al-0.91C-0.88Si-0.49Mo was poured into both the molds. Optical microscopy revealed extensive oxide-film-like features on samples obtained from the top section of castings. Across the limited number of molds and a single heat, the pressurized and non-pressurized systems had Charpy toughness values comparable to the naturally pressurized top riser system. The observed fracture surfaces commonly contained Al-oxide-rich film features and presence of AlN, AlN-MnO and AlN-MnS inclusions.