Runner Design to Control Defects in Iron Castings

This work examines the design and implementation of a new runner and gating system for an existing cast iron exhaust manifold. Three designs were tested. Pressurized and unpressurized systems were trialed to determine which system produces better results in gravity casting. Runner, gate and sprue areas were varied to control the peak linear velocity during filling. These trials gave high defect levels for peak velocities over 2.0 m/s in pressurized and unpressurized systems, and the pressurized systems significantly reduced slag inclusions. A pressurized system with larger runner sections reduced the casting defect rate tenfold when peak gate velocity was limited to 1.0 m/s.