Thermal Decomposition Behavior of Expandable Pattern Including Blended Metal or Alloy Powder in Evaporative Pattern Casting Process of Cast Iron

Abstract

Metal or alloy powder capable of exothermic reaction with cast iron melt was blended into expandable polystyrene patterns. The behavior of thermal decomposition of the expandable patterns in evaporative pattern casting of cast iron was investigated. In evaporative pattern casting in which patterns including blended powder of metallic Si, Fe-Si alloy, Fe-Si-Mg alloy, or Fe-Si-Ca alloy were used, the temperature of the melt was higher than that in casting with original non-blended patterns. When the blending ratio was increased, the volume and pressure of decomposition gas during casting process were increased and, on the other hand, the filling rate of the melt was reduced. The use of patterns blended with powder caused no defect and abnormal structure in castings. These results imply that blending of metal or alloy powder into a pattern accelerates thermal decomposition of the pattern.