Four basic mechanisms:
• Mechanical (liquid‐state)
• Chemical
• Vapor‐state
• Explosion penetration
The liquid metal exerts:
• Static pressure
• Dynamic pressure
• Pressure because of expansion
Generally occurs at locations where the sand is the hottest
(cores, concave sections) and is of lowest density
• Low surface tension
• High P, Si, or Mn content
• Elevated static or dynamic metal pressure
• High metal and sand temperature
• Sand too coarse, or insufficiently rammed
• Thermal conductivity of sand too low
• Poor quality mold wash or blacking
Other Problems
• Residual stresses
• Prior history of the material
• Segregation
• Degenerated graphite